Proceedings Series
Naturally Occurring Radioactive Material (NORM VIII)
Proceedings of an International Symposium Rio de Janeiro, Brazil, 18–21 October 2016
INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA
ISBN 978–92–0–107618–2 ISSN 0074–1884
Naturally Occurring Radioactive Material (NORM VIII)
NATURALLY OCCURRING RADIOACTIVE MATERIAL
(NORM VIII)
AFGHANISTAN ALBANIA ALGERIA ANGOLA
ANTIGUA AND BARBUDA ARGENTINA
ARMENIA AUSTRALIA AUSTRIA AZERBAIJAN BAHAMAS BAHRAIN BANGLADESH BARBADOS BELARUS BELGIUM BELIZE BENIN
BOLIVIA, PLURINATIONAL STATE OF
BOSNIA AND HERZEGOVINA BOTSWANA
BRAZIL
BRUNEI DARUSSALAM BULGARIA
BURKINA FASO BURUNDI CAMBODIA CAMEROON CANADA
CENTRAL AFRICAN REPUBLIC CHADCHILE CHINA COLOMBIA CONGO COSTA RICA CÔTE D’IVOIRE CROATIA CUBACYPRUS
CZECH REPUBLIC DEMOCRATIC REPUBLIC
OF THE CONGO DENMARK DJIBOUTI DOMINICA
DOMINICAN REPUBLIC ECUADOR
EGYPT EL SALVADOR ERITREA ESTONIA ESWATINI ETHIOPIA FIJIFINLAND FRANCE GABON GEORGIA
GERMANY GHANA GREECE GRENADA GUATEMALA GUYANA HAITI HOLY SEE HONDURAS HUNGARY ICELAND INDIA INDONESIA
IRAN, ISLAMIC REPUBLIC OF IRAQIRELAND
ISRAEL ITALY JAMAICA JAPAN JORDAN KAZAKHSTAN KENYA
KOREA, REPUBLIC OF KUWAIT
KYRGYZSTAN
LAO PEOPLE’S DEMOCRATIC REPUBLIC
LATVIA LEBANON LESOTHO LIBERIA LIBYA
LIECHTENSTEIN LITHUANIA LUXEMBOURG MADAGASCAR MALAWI MALAYSIA MALIMALTA
MARSHALL ISLANDS MAURITANIA
MAURITIUS MEXICO MONACO MONGOLIA MONTENEGRO MOROCCO MOZAMBIQUE MYANMAR NAMIBIA NEPAL
NETHERLANDS NEW ZEALAND NICARAGUA NIGER NIGERIA NORWAY OMANPAKISTAN
PALAU PANAMA
PAPUA NEW GUINEA PARAGUAY
PERUPHILIPPINES POLAND PORTUGAL QATAR
REPUBLIC OF MOLDOVA ROMANIA
RUSSIAN FEDERATION RWANDA
SAINT VINCENT AND THE GRENADINES SAN MARINO SAUDI ARABIA SENEGAL SERBIA SEYCHELLES SIERRA LEONE SINGAPORE SLOVAKIA SLOVENIA SOUTH AFRICA SPAIN
SRI LANKA SUDAN SWEDEN SWITZERLAND
SYRIAN ARAB REPUBLIC TAJIKISTAN
THAILAND
THE FORMER YUGOSLAV REPUBLIC OF MACEDONIA TOGOTRINIDAD AND TOBAGO TUNISIA
TURKEY
TURKMENISTAN UGANDA UKRAINE
UNITED ARAB EMIRATES UNITED KINGDOM OF
GREAT BRITAIN AND NORTHERN IRELAND UNITED REPUBLIC
OF TANZANIA
UNITED STATES OF AMERICA URUGUAY
UZBEKISTAN VANUATU
VENEZUELA, BOLIVARIAN REPUBLIC OF
VIET NAM YEMEN ZAMBIA ZIMBABWE The following States are Members of the International Atomic Energy Agency:
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PROCEEDINGS SERIES
NATURALLY OCCURRING RADIOACTIVE MATERIAL
(NORM VIII)
PROCEEDINGS OF AN INTERNATIONAL SYMPOSIUM ORGANIZED BY THE
INSTITUTE OF RADIATION PROTECTION AND DOSIMETRY, NATIONAL NUCLEAR ENERGY COMMISSION, BRAZIL
IN COOPERATION WITH THE
INTERNATIONAL ATOMIC ENERGY AGENCY AND HELD IN RIO DE JANEIRO, BRAZIL,
18–21 OCTOBER 2016
INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 2018
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October 2018 STI/PUB/1832
IAEA Library Cataloguing in Publication Data Names: International Atomic Energy Agency.
Title: Naturally occurring radioactive material (NORM VIII) / International Atomic Energy Agency.
Description: Vienna : International Atomic Energy Agency, 2018. | Series: Proceedings series (International Atomic Energy Agency), ISSN 0074–1884 | Includes bibliographical references.
Identifiers: IAEAL 18-01187 | ISBN 978–92–0–107618–2 (paperback : alk. paper) Subjects:
LCSH: Ionizing radiation — Dosage. | Radiation — Safety measures. | Radioactive substances.
Classification: UDC 614.876 | STI/PUB/1832
FOREWORD
All minerals and raw materials contain radionuclides of natural origin, of which the most important for the purposes of radiation protection are the radionuclides in the 238U and 232Th decay series. For most human activities involving minerals and raw materials, the levels of exposure to these radionuclides are not significantly greater than normal background levels.
Such exposures are not of concern for radiation protection. However, certain work activities can give rise to significantly enhanced exposures that may need to be controlled by regulation.
Material giving rise to these enhanced exposures has become known as naturally occurring radioactive material (NORM).
As a direct consequence of the 1996 European Council Directive 96/29/Euratom and its possible implications for non-nuclear industries in Europe, a symposium on NORM, the first in the current series, was held in Amsterdam in 1997. The second in the series (NORM II) was held in 1998 in Krefeld, Germany, the third (NORM III) in Brussels in 2001, the fourth (NORM IV) in Szczyrk, Poland, in 2004, the fifth (NORM V) in Seville, Spain, in 2007, the sixth (NORM VI) in Marrakesh, Morocco, in 2010 and the seventh (NORM VII) in Beijing in 2013. In addition, a symposium on Technologically Enhanced Natural Radiation was held in Rio de Janeiro, Brazil, in 1999, reflecting the growing interest at that time within regions beyond Europe in the management of exposure to NORM.
The close involvement of the IAEA in most of these symposia is reflected in the fact that the proceedings of the Rio de Janeiro symposium in 1999 and the Szczyrk symposium in 2004 were published as IAEA-TECDOC-1271 and IAEA-TECDOC-1472, respectively, while the proceedings of the Seville, Marrakesh and Beijing symposia were published in the IAEA Proceedings Series. In the case of NORM VIII, the IAEA entered into a formal cooperation arrangement with the organizer (as it had done for other recent symposia in the series), in terms of which the IAEA, in addition to publishing these Proceedings, served on the Steering Committee and Scientific Committee and provided financial support to several participants from Member States eligible to receive assistance under the IAEA’s technical cooperation programme.
The NORM VIII symposium was attended by 257 participants from 50 countries and provided an important opportunity to review the developments that had taken place during the three year period since the Beijing symposium in 2013. This period was characterized by ongoing activities to implement international standards on radiation protection and safety in many countries. These Proceedings contain 31 papers accepted for oral presentation, text versions of 35 poster presentations and a summary that concludes with the main findings of the symposium.
The IAEA, on behalf of the Brazilian organizers — the Institute of Radiation Protection and Dosimetry, and the National Nuclear Energy Commission — gratefully acknowledges the cooperation and support of all the organizations and individuals who contributed to the success of this symposium.
The IAEA officer responsible for this publication was H.B. Okyar of the Division of Radiation, Transport and Waste Safety.
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CONTENTS
SUMMARY
...1INTERNATIONAL AND NATIONAL STANDARDS ON NORM — PRACTICAL IMPLICATIONS (Session 1)
IAEA work programme on NORM: Achievements and challenges...19 H.B. Okyar
ICRP and NORM exposure: A report in preparation (Summary)...22 J.-F. Lecomte
Standards for NORM industrial practices in accordance with the
graded approach to regulation: Elaboration of a strategy for Austria...24 M. Tatzber, S. Friedreich, F. Rechberger, C. Katzlberger
Updates to TENORM management in the United States...27 P.V. Egidi
Challenges in implementing the change in regulations in the NORM industry:
The new European Directive...35 R. García-Tenorio
Poster presentation
Radiological risk classification of NORM industries in Brazil…………..…………40 A.L.R. Ferreira, J.N. da Silva, C.A.M. Lima, F.C.A. da Silva
RISK COMMUNICATION (WORKERS AND PUBLIC) (Session 2)
Mission (im)possible: Communicating about NORM topics and
stakeholder engagement……….40 T. Perko
Building the bridge from both ends? Comprehensive extraction and
zero waste strategies for NORM industry tailings and residues...53 H. Tulsidas, J. Hilton, B. Birky, M. Moussaid,
T.K. Haldar, R. García-Tenorio
Case study in the municipality of Iperó regarding the Brazilian multipurpose reactor implementation and public acceptance:
Would it be a matter of communication? ...65 R.M. Ayllon, A.A. Castro, L.A. Farias
RADIOACTIVE WASTE MANAGEMENT AND DISPOSAL (Session 3)
Management of NORM residues: Practical aspects...78 N. Tsurikov
Management of radioactive residues and waste generated during
remediation of uranium production legacy sites in Germany………91 P. Schmidt, J. Regner
Radionuclide behaviour in potential applications of phosphogypsum...96 F.P. Carvalho, J.M. Oliveira, M. Malta
NORM management in the Netherlands...101 L.P.M. van Velzen, J. Welbergen
Radiological risks associated with building materials and industrial by-products...110 Z. Sas, W. Schroeyers, G. Bator, M. Soutsos, W. Sha, R. Doherty, T. Kovacs Poster presentations
Reactive barrier design to mitigate acid mine drainage………116 A.C. Silva, H.T. Fukuma, A.F. Benedito
Fabrication of titanium dioxide supports for ceramic membranes used in the
treatment of nuclear waste………...………120 E.E.M. Oliveira, J.G. Santos, U.C.C.S. Siciliano
Uranium recovery from acid mine drainage treatment residue………126 M.M. Dias, H.T. Fukuma, C.H.T. de Carvalho, R.A.S. Villegas
NATURAL RADIOACTIVITY (Session 4)
UNSCEAR review of radiation exposure due to activities involving NORM...131 J.G. Hunt
Poster presentations
Natural radioactivity in sediments and water of Clotilde Briozzo Lagoon………..135 A. Noguera, G. Azcune, H. Bentos Pereira, L. Fornaro
Gross alpha and gross beta radioactivity determination in the
coastal groundwater of Rocha………...………139 G. Azcune, L. Fornaro
High purity germanium gamma-ray detector for gross alpha and gross beta
measurements in water samples………...………..143 M.F.S. Casagrande, D.M. Bonotto
NaI(Tl) detectors for environmental gamma survey and background radiation
mapping of venues and other strategic locations for major public events…...150 E.M. de Souza
Radon activity concentrations in an experimental living environment
in Curitiba, Brazil………...………..155 Y.R. Hashimoto, J.N. Corrêa, S.A. Paschuk, D.C. Narloch, A.P. Mendes,
L.M. Wosniack, G. Macioski
Variability and spatial distribution of radionuclides of natural origin
in the state of Minas Gerais………...……..……….159 C.M. Peixoto, P.R.M. Fernandes, J.F. Macacini,
P.C.H. Rodrigues, V.M.D. Feliciano
Radionuclides of natural origin in food and water from a high background
radiation area in south-eastern Brazil………...……165 M.M.L. Rosa, M.H.T. Taddei, I.C.A. Carrosco, L.T.V. Cheberle,
R.P. Avegliana, V.A. Maihara
Radionuclides of natural origin in a Brazilian mussel reference material…………169 E.G. Moreira, M.B.A. Vasconcellos, M.M.L. Rosa, M.H.T. Taddei
Natural radioactivity in Brazilian underground mines………..……173 T.O. Santos, Z. Rocha, P.R. Cruz, F.L.S. Borges, J.B. Siquiera, V.A. Gouvea Radionuclides of natural origin in environmental samples collected in the
catchment area of Ponte Nova reservoir, São Paulo, Brazil………....179 A.R. Silva, S.R. Damatto, L. Leonardo, P.N. Gonçalves,
J.M. Souza, M.F. Máduar
Experience and performance obtained in indoor radon intercomparison exercises.186 D.C.S. Dias, N.C. Silva, T.A.A. Oliveira, R.L. Bonifácio
GEORAD: Geo-referenced database of environmental radioactivity in Brazil……191 R.C. dos Reis, T.A.A. Silva, S.A. Gonzalez, D.C. Lauria
Short term temperature stability test for uranium soil
reference material……….193 A.M.G. Fonseca, A.F. Clain, V.D.B. Dantas, M.J.C. Bragança, P.S. Souza Uncertainty estimation using the spreadsheet approach for determination of
210Po in environmental samples by alpha spectrometry………...198 T.B.S. Nascimento, M.H.T. Taddei
Concentrations of 226Ra, 232Th and 40K in Brazilian wall paint………204 L.M. Fonseca, B.R.S. Pecequilo
Spatial surveyof radioactivity in Brazil………....208 F.C.A. Ribeiro, D.C. Lauria, F.G. da Cunha, M.A. Pires do Rio,
J.I.R. Silva, S.A. Gonzalez, T.A.A. Silva, W.O. Sousa
Comparison of 210Pb and 210Po activity concentrations for sediment dating………213 H.C. Almeida, T.B.S. Nascimento, M.H.T. Taddei, B.P. Mazzilli
ENVIRONMENTAL IMPACT ASSOCIATED WITH NORM INDUSTRIES (Session 5)
Radiological evaluation of monazite mining in central Spain...220 R. García-Tenorio, E. Sanz, E. Burkhalter, G. Manjón, I. Vioque, I. Diaz Environmental contamination around the Caldas uranium mine due to
uranium and thorium in sediments, rocks, mine waste and fertilizer...225 P.H. Dutra, V.M.D. Feliciano
Radiation exposures from landfill disposal of titanium dioxide industry waste:
Comparison of models with site specific measurements...231 K.A. Jones, P.V. Shaw
Radionuclides of natural origin in stream sediments of the
Poços de Caldas plateau, Brazil...236 N.C. da Silva, H.L.C. Alberti, E.T.Z. Guerrero, M.R.L. Nascimento,
R.L. Bonifácio, H.A. Franco da Nascimento, R.A.S. Villegas
Preliminary radiological assessment of the phosphate industry of Senegal...240
A.S. Ndao, F.P. Carvalho, L. Silva, J.M. Oliveira, M. Malta, N.A.B. Faye Radiological assessment of heavy-mineral sand exploitation in Mozambique...244
F. Conceição, F. Catuane, S. Taímo, F.P. Carvalho, J.M. Oliveira, M. Malta Residues from NORM industries: A unified approach to
environmental impact assessment...248 B. Michalik
Poster presentations
Natural uranium in biological material from high background
radiation areas in Brazil………..……….256 W.S. Pereira, A. Kelecom, C.B. Espindola, A.X. da Silva, R.A. Filgueiras NORM waste from Ghanaian oil production………..…………..261
D.O. Kpeglo, J. Mantero, E.O. Darko, G. Emi-Reynolds, A. Faanu, G. Manjón, I. Vioque, E.H.K. Akaho, R. García-Tenorio
Radiological assessment of water treatment systems in Poços de Caldas, Brazil…266 A.M. Ferreira, R.A.S. Villegas, H.T. Fukuma
Bacterial leaching in uranium mine effluents at the Ore Treatment Unit,
Caldas, Brazil………...271 H.A.F. Nascimento, M.B. Campos, S. Rodgher, C.V. Roque,
A.L. Bruschi, M.R.L. Nascimento
INDUSTRY SPECIFIC STUDIES (e.g. OIL, GAS, COAL, METALS) (Session 6)
Practical cases of NORM transport: Problems and solutions………...278 N. Tsurikov
NORM related mineral developments in Finland...287 E. Pohjolainen, H. Tuovinen, P. Sorjonen-Ward, R. Neitola
Radiological assessment of tantalite mining in Ethiopia...293 M.B Tufa, F.P. Carvalho, J.M. Oliveira, M. Malta
Radiological investigation at Yatagan coal fired
power plant, Turkey...297 B. Ozden, T. Vaasma, M. Horvath, M. Kiisk, T. Kovacs
Poster presentations
Radioactivity in soil near oilfields………302 M.H. Alharbi
Evaluation of NORM residues from the processing of crude oil in a refinery…….306 A. Reichelt
Radioactivity in gas mantles sold in Mexico………311 C.D. Mandujano-García, M. Sosa, R. García-Tenorio, J. Mantero
Lead-210 in NORM from the oil and gas industry………...316 L.S. Faria, R.M. Moreira
Potential for NORM waste in some mining and processing industries of Ukraine..320 T. Pavlenko, V. Riazantsev, M. Aksenov, M. Fryziuk, O. Taraziuk, N. Vlasiuk
OCCUPATIONAL RADIATION PROTECTION AND NORM METROLOGY (Session 7)
UMEX: A worldwide IAEA survey of occupational exposure in
facilities for the production of uranium...329 F. Harris, D. Chambers, H.B. Okyar
New IAEA Safety Report on occupational radiation protection in the
uranium mining and processing industry...344 H.B. Okyar
Dose assessment in a phosphoric acid facility in Zimbabwe...347 T. Watyoka, F.P. Carvalho, L. Silva, J.M. Oliveira, M. Malta
Poster presentations
Measuring activity concentrations using a high purity germanium detector:
Extended source efficiency correction and optimization of sample position..351 P. Ochoa, F. Bautista, E. Fajardo, W. Rodrigues, F. Cristancho
Determination of the minimum sample mass of U3Si2 to be used as candidate
reference material for chemical analyses of total uranium and total silicide...356 L.V. Santana, M.E.B. Contrim, C.Sisti, C.M. Silva, D.S. Said, M.A.F. Pires Self-attenuation factors in gamma-ray spectrometry of samples containing
radionuclides of natural origin……….…………361 B.R.S. Pecequilo, F. Cavalcante, L.F. Barros, A.O. Ferreira,
L.M. Fonseca, C. Mateus
DECOMMISSIONING AND REMEDIATION (Session 8)
Decommissioning of a rare earths extraction plant and
remediation of the NORM contaminated site...368 Teng Iyu Lin
Evaluation and survey of NORM legacy sites in Austria (Summary)...372 F. Rechberger, E.Lindner, M. Dauke, M. Tatzber,
C. Landstetter, C. Katzlberger
Hydrogeochemical and isotopic study of groundwater in the environmental
remediation of OSAMU UTSUMI uranium mine...374 H.L.C. Alberti, S.Y. Pereira, R.P. Borba, P.M. Fleming, R.T. Goda,
M.S. Antunes, A.Í. Dias, F.W. Rodrigues Poster presentations
Treatment of coal mining tailings to reduce the leaching of metals
including uranium and thorium………...….378 Z.C.Castilhos, R.C.J. Alamino, R.G. Cesar, E.F. Souza,
A.C. Ribeiro-Duthie, C.L. Schneider
Acute toxicity of manganese to Ceriodaphnia silvestrii and Daphnia magna in bioassays and the potential toxicity of this metal in uranium mine effluent…382 C.R. Ferrari, H.A.F. Nascimento, A.L. Bruschi, S. Rodgher,
C.V. Roque, N.R.L. Nascimento, R.L. Bonifácio
Chairpersons of Sessions, Secretariat of the Symposium, Steering Committee of the Symposium,
National Organizing Committee of the Symposium,
Scientific Committee of the Symposium...386 List of
Participants...389 Author Index...409
1
SUMMARY
1. BACKGROUND TO THE SYMPOSIUM 1.1. Objectives
This Symposium, the eighth in a series of symposia on naturally occurring radioactive material (NORM), once again provided an important opportunity to review recent technical and regulatory developments concerning exposure to NORM, with the overall objectives of addressing radiation protection issues, discussing the results of new research, exploring practical case studies of industrial applications and identifying new societal needs and technical requirements for regulatory bodies and NORM industries. The Symposium provided a platform for experts from NORM industries, academic and research institutions and regulatory bodies from all over the world to share experiences, to identify opportunities, to analyse current challenges, and to review progress made in identifying, quantifying and managing the radiological risks associated with industrial processes involving NORM. Ongoing activities to implement new international standards during the period since the last NORM symposium in 2013 provided an important backdrop to the presentations and discussion.
As with previous symposia in this series, the technical programme was well subscribed.
These Proceedings contain 31 papers that were accepted for oral presentation along with 35 contributions in the form of posters.
1.2. International aspects
The first NORM symposium, held in Amsterdam, Netherlands, in 1997, had been organized in response to concerns within the non-nuclear industry in the European Union that the implementation of a new European Council Directive1 would place unreasonable and unwarranted legal obligations on many industrial enterprises that handled and processed material containing low levels of radionuclides of natural origin. Subsequently, as new regulations for the control of exposure to NORM became established in European Union Member States and as knowledge about exposure levels improved, those concerns diminished to some extent, although the definition of the scope of regulation remained controversial.
Furthermore, it became apparent that this was becoming more of a global issue because of the increasingly international profile of the mining and mineral processing industry, with large quantities of minerals being mined and beneficiated in countries far from Europe and shipped to other countries — often over vast distances — for further processing. In line with this trend, successive NORM symposia began to take on a more international flavour and the involvement of the IAEA became progressively greater.
Given this background, it was fitting that Brazil — a major source, processor, user and supplier of industrial minerals, many of which contained elevated concentrations of radionuclides of natural origin — was chosen as the venue for the NORM VIII symposium.
The planning of the symposium followed an approach similar to that adopted for NORM V, NORM VI and NORM VII, in that steps were taken to encourage participation from all regions of the world. The steering committee arranged for broad international representation on the scientific committee of the symposium and encouraged members of that committee to actively promote participation in the symposium from within their own geographic regions.
Furthermore, the IAEA once again provided financial support to several participants from Member States eligible to receive assistance under the IAEA technical cooperation programme.
1COUNCIL OF THE EUROPEAN UNION, Council Directive 96/29/Euratom of 13 May 1996 laying down basic safety standards for the protection of the health of workers and the general public against the dangers arising from ionizing radiation, Official Journal of the European Communities, L 159, vol. 39 (1996).
2
These efforts were evidently successful in that the symposium attracted 257 participants from 50 countries. While the high level of participation by individuals from regulatory bodies and scientific institutes was encouraging, it was noted that, once again, there were relatively few participants from NORM industries.
2. RADIATION PROTECTION STANDARDS AND REGULATORY APPROACHES 2.1. Activities of the IAEA and the International Commission on
Radiological Protection
The latest version of the IAEA’s International Basic Safety Standards — IAEA Safety Standards Series No. GSR Part 3, published in 2014 (the BSS)2 — establishes radiation protection requirements for NORM industries in planned and existing exposure situations. The IAEA has initiated many activities, including the development of safety guides and safety reports, for assisting Member States in implementing the relevant requirements of the BSS. It was pointed out in this regard that the characteristics of industrial processes and exposure situations involving NORM are in many cases quite different from those associated with other activities involving radioactivity. Reference was made to the wide diversity of industrial processes and process materials, the generally very low (but sometimes unpredictable) exposure levels, the presence of non-radiological hazards that may well be of greater concern than radioactivity, and the involvement of several different regulatory bodies. This situation gives rise to various challenges for operators and regulatory bodies alike. For instance, guidance on radiation protection and NORM residue management has to be tailored to specific NORM industries and/or industrial processes and has to address the management of extremely large amounts of NORM residues (including the use or recycling of residues where possible) and the remediation of contaminated legacy sites. The work programme includes the development of industry specific guidelines for radiation protection and management of NORM residues, long term management of bulk NORM residues and remediation of legacy sites contaminated with NORM. The programme also addresses the need for enhanced and improved levels of knowledge, understanding and communication. It was emphasized that the the IAEA work programme on NORM focuses heavily on the application of the graded approach to regulation, one of the key concepts in the BSS.
It was reported that the International Commission on Radiological Protection had, in 2013, relaunched a task group to prepare a report on exposure to NORM. It was pointed out that industrial activities involving NORM tend to be well-established activities that continue to be regulated by various authorities concerned with the control of non-radiological hazards.
Consequently, when dealing with radiological hazards the need for a graded approach to regulation is not always well appreciated and a radiation protection culture is often lacking. In addition, it seems that there is still some confusion as to whether activities involving NORM should be regarded as planned exposure situations or existing exposure situations.
2 EUROPEAN ATOMIC ENERGY COMMUNITY, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, IAEA Safety Standards Series No. GSR Part 3, IAEA, Vienna (2014).
3 2.2. Implementation of international standards
The new International Basic Safety Standards published by the IAEA in 2014 have been implemented within the European Union through a new European Council Directive3. With regard to NORM, this Directive has achieved some progress in reducing (but not eliminating) the complications and confusion that existed previously — these had given rise to some misunderstandings and differences in interpretation, resulting in overregulation in some instances. For example, the new Directive has now introduced numerical criteria for NORM with respect to clearance (e.g. 1 Bq/g for activity concentrations of uranium and thorium series radionuclides) and exemption (an annual effective dose of the order of 1 mSv/a). Nevertheless, there is still some confusion with regard to the newly introduced concept of reference levels in existing exposure situations, with the result that such reference levels are sometimes being erroneously treated as action levels or as limits, rather than as criteria for prioritizing the need for protective or remedial actions and below which optimization of protection is still required.
Among other observations, it was noted that, for radiological assessment purposes, there is an ongoing need to give more effort to using actual measurements rather than modelling, since exposures to NORM are often difficult to predict reliably by modelling and tend to be overestimated in such cases. It is encouraging to see that by-product use and recycling of NORM residues are steadily gaining acceptance. Where disposal as waste is the only feasible option, more attention needs to be given to the possible use of facilities for general industrial waste (hazardous or non-hazardous) rather than radioactive waste repositories.
The regulation of NORM in the United States of America continues to be complicated, as a result of being primarily (but not entirely) left to individual states. While this approach provides flexibility, it can lead to inconsistencies in regulation and diverse approaches, particularly in the management of NORM residues. Even the terminology can be confusing, since there is no single definition of NORM and widespread use is still made of the additional term TENORM (with such use having largely fallen away in other countries). Inconsistencies between states are now starting to attract more attention, and are even giving rise to legal issues, while there is now a recognized need for more data on exposure to NORM.
In the Netherlands, regulations and procedures for activities involving NORM have been under development for many years, although with the establishment of the new European Directive in 2014 there is some work still to be done in order to implement the new requirements while at the same time reducing the costs involved. Experience over the past years has highlighted a tendency for the regulation of NORM to be unnecessarily restrictive and it is felt that this needs to be relaxed. Experience has also demonstrated the benefits of cooperation between all stakeholders. With regard to NORM residues, the by-product use or recycling of such residues is the primary target of the NORM residue management system. For application in civil engineering, a specific requirement in Dutch legislation is that the NORM residue is diluted to a level such that it is no longer considered radioactive (in that it does not exceed the relevant ‘exemption’ level). Thus, dilution in this case is not only a treatment option but also a legal obligation. Only if the options of recycling or use are not feasible can the material be disposed of, and only then is it considered to be waste.
3COUNCIL OF THE EUROPEAN UNION, Council Directive 2013/59/Euratom of 5 Dec 2013 laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation, Official Journal of the European Communities, L13, vol. 57 (2014).
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In Austria, implementation of the latest European Council Directive is now getting underway. It has been found that more data are needed on the various activities involving NORM and the associated exposures. Also, additional guidelines will have to be developed.
The implementation process is based firmly on the graded approach to regulation. There are many legacy sites potentially contaminated with radionuclides of natural origin, especially isotopes of radium and thorium. A legacy site catalogue is regularly updated, sites are being characterized and the associated radiological risks are being prioritized on the basis that an activity concentration of 1 Bq/g for uranium and thorium series radionuclides is assumed to be broadly equivalent to an annual dose of 1 mSv. For each site identified as requiring action, a decision will be made on whether to decontaminate or secure the site. Factors influencing this decision include the size of the site, whether it is enclosed or open, the solubility of the contaminant and the possibility of groundwater contamination. The approach for sites that are to be remediated involves a dose assessment, radiation protection and monitoring during the remediation work, coordination of the work carried out by the various experts and companies and a post-remediation survey of environmental media. The local population will be informed of the radiological risks and the waste from the remediation work will be disposed of at a hazardous waste landfill facility or at a radioactive waste repository, depending on the radiological risk, on a case by case basis.
In Brazil, a new regulation based on the latest version of the IAEA BSS has been promulgated. Implementation of this regulation has begun, with the classification of industrial activities involving NORM into one of three risk categories: high, medium and low. The industrial activities concerned are classified according to the activity concentrations of 238U and
232Th and — in the case of very low activity concentrations — according to risk (in terms of dose). It has been found that, of the 19 facilities concerned, nine were classified as low risk and four were classified as medium risk. The six facilities classified as high risk were facilities involved in the production of niobium and tantalite.
It is clear from many of the presentations at the Symposium that worldwide implementation of international standards applicable to NORM and the use of supporting documentation by governments and regulatory bodies continues to grow. However, concern was expressed that NORM industries were not using the guidance and supporting information available at the international level and the participation of NORM industry experts in the NORM symposia had declined to very low levels.
2.3. Transport of NORM
The application of the IAEA Regulations for the Safe Transport of Radioactive Material (the Transport Regulations)4 to the transport of NORM has given rise to some significant problems. The problems relate principally to international shipments and arise from a lack of understanding and communication between transport companies and government departments in different countries. These problems have resulted in rejections of shipments at ports of entry and claims for compensation by workers and by owners of properties near transport routes. One particular problem area is related to NORM that presents additional, non-radiological hazards such as corrosivity, biological hazards, flammability or chemical toxicity. Other problems arise from the temporary storage of NORM shipments in transit storage areas (regulatory control for material in storage is more restrictive than that for material in transport), the triggering of alarms by shipments containing NORM but which are exempt from the Transport Regulations, the buildup of radon in containers and hulls of ships (which can be significant even for exempt shipments) and a failure to recognize that, for the purposes of defining surface contamination,
226Ra is not a low toxicity alpha emitter and is consequently subject to a surface contamination
4INTERNATIONAL ATOMIC ENERGY AGENCY, Regulations for the Safe Transport of Radioactive Material, 2012 Edition, IAEA Safety Standards Series No.SSR-6, IAEA, Vienna (2012).
5 limit ten times lower than that for other radionuclides associated with NORM contamination on the surfaces of objects in transport.
Investigation of these problems has highlighted the following contributory factors: a lack of communication between parties concerning legal requirements; misinterpretation of legislation, regulations and guidelines; the use of different editions of the Transport Regulations in various countries; the adoption of national regulations and/or standards that are in conflict with the Transport Regulations; and regulatory inconsistencies between countries concerning the transshipment of NORM through ports on the way to the final destination.
2.4. Use of raw materials and industrial residues for construction
Materials used for construction purposes are mostly obtained from natural raw materials, but may also be associated with residues from the mining and processing of minerals. In both cases, the materials contain radionuclides of natural origin that represent a source of public exposure. For some materials, this exposure may be significantly higher than exposure to normal natural background radiation. In terms of international standards, the use of such materials for construction purposes may be subject to restrictions, depending on the dose to members of the public. This dose generally has to be assessed by exposure modelling based on the activity concentrations of radionuclides of natural origin contained within the material.
In a project funded by the European Union, a large number of worldwide materials used for construction purposes are being investigated. Activity concentrations of individual radionuclides of natural origin have been measured in 30 materials (23 natural materials and 7 industrial residues) and used for the calculation of external gamma exposures of members of the public when used as building materials. For 226Ra, activity concentrations of up to 27.8 Bq/g were reported for natural materials and up to 3.1 Bq/g for industrial residues. For 232Th, the corresponding activity concentrations were up to 0.9 Bq/g for natural materials and up to 1.35 Bq/g for industrial residues. Two approaches to dose assessment were used: the
‘I-index’ screening approach developed within the European Union and a more precise approach developed by the IAEA and published as an IAEA Safety Guide. It was found that the I-index approach tended to overestimate doses, sometimes to a significant extent (up to 70%). This could result in unnecessary regulatory restrictions being placed on the use of many materials for building purposes.
3. ACTIVITY CONCENTRATIONS IN RAW MATERIALS, PROCESS MATERIALS AND PRODUCTS
3.1. Production and use of thorium-containing materials
Heavy-mineral sand deposits tend to be associated with thorium because of the presence of monazite. Two heavy-mineral sand operations in Mozambique producing zircon and rare earth elements were investigated. The activity concentrations in the sand dune top layer, sand waste, magnetic ilmenite and magnetic fraction were all less than 1 Bq/g. The activity concentrations in the remaining materials were consistent with values obtained from other heavy-mineral sand operations around the world:
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Sand dune, rich layer: 1.01 Bq/g 232Th 0.4 Bq/g 238U
Wet mineral concentrate: 3.2 and 1.4 Bq/g 232Th 0.7 and 0.6 Bq/g 238U Non-magnetic fraction: 1.6 and 4.5 Bq/g 232Th 2.7 and 1.6 Bq/g 238U
Zircon: 0.2 Bq/g 232Th 1.1 Bq/g 238U
Activity concentration measurements were performed on thorium-containing gas mantles in Mexico. The 232Th activity concentrations ranged from 232 to 683 Bq/g, consistent with values measured in other countries. While thorium-containing gas mantles have largely been replaced by thorium-free products in various countries, they can still be purchased in Mexico and disposed of in normal household waste.
Commercially available paint contains titanium dioxide as a pigment material. This is produced from heavy-mineral sand which contains thorium in the form of monazite. The pigment production process is essentially a purification process, so the final product is not expected to contain significant amounts of thorium. In Brazil, the activity concentrations of
232Th, 226Ra and 40K were measured in several samples of wall paint. As would be expected, none of the activity concentrations were significantly elevated.
3.2. Oil and gas production
In the processing of crude oil in a refinery, over 1000 t of residues containing radionuclides of natural origin can be generated in a year. The use or disposal of these residues is subject to limits on activity concentration. Measurements performed on various samples collected from an oil refinery showed that all of the sludge samples were below 1 Bq/g but high
210Pb activities were measured on heat exchanger scale (up to 8 Bq/g) and installed equipment in distillation columns (up to 25 Bq/g). In Germany the 95 % upper confidence limit of the mean of a random sample activity concentration has to fall below 1 Bq/g concerning the dumping or combustion of NORM residues. Several samples were taken from sewage sludge (800 t/a) and oil sludge (500 t/a) as independent random samples. From these samples the upper confidence limit for the confidence level 0.95 was determined by means of both classical and modern numerical (‘bootstrapping’) statistical methods. In the case of ten independently gathered samples of oil sludge, the control limit was exceeded in terms of both statistical methods. When the sample size was expanded to 20 samples, it could be shown by means of the bootstrap method that the control limit was not exceeded. By using the classical method, the control limit was exceeded again as previously.
The deposition of 210Pb, particularly in gas production facilities, was also highlighted from the point of view that there are two distinct deposition mechanisms. The decay of 222Rn can generate unsupported 210Pb in association with dispersed particles and colloids. It can also generate supported 210Pb in the form of very thin deposits that are invisible and difficult to detect. In the latter case, activity concentrations exceeding 1 Bq/g are commonly found.
A survey of oil production facilities in Ukraine identified the presence of sludge and other waste with radionuclide activity concentrations far in excess of 1 Bq/g. The mean activity concentrations for a given facility were up to 8 Bq/g for 238U, up to 9 Bq/g for 226Ra, up to 11 Bq/g for 210Pb and up to 3 Bq/g for 232Th. Several oil refineries were also surveyed. Samples from waste disposal ponds were analysed and the average radionuclide activity concentrations were found to be 5 Bq/g for 238U and 226Ra, 7 Bq/g for 210Pb and 2 Bq/g for 232Th.
Activity concentration data for produced water and scale were reported from oil production facilities in Ghana. As expected, the dominant radionuclides were 226Ra and 228Ra.
Activity concentrations of these radionuclides in produced water ranged from 6 to 34 Bq/L, while in scale the activity concentrations ranged from 27 to 58 Bq/g. These results were consistent with values reported from elsewhere in the world.
7 Activity concentrations of radionuclides in the uranium decay series and thorium decay series were measured in soil samples gathered from around oil extraction sites in Kuwait and Qatar. The concentrations were all significantly below 1 Bq/g. While the results showed some evidence of elevated concentrations at these locations, the upper bound of the normal worldwide range for rocks and soil was exceeded only in the case of one sample.
3.3. Phosphate production
The following activity concentration data were reported for phosphate production facilities in various parts of the world:
(a) A phosphoric acid plant in Zimbabwe had suffered a decline in production in recent years and process materials and residues from past production were stored at the site. Contrary to expectations, the activity concentrations in the various process materials were not significantly enhanced except for some radium scale which had an activity concentration of 3 Bq/g.
(b) A phosphate mine and processing facility in Senegal was investigated. The 226Ra concentrations in the phosphate rock, wet phosphate raw material and phosphogypsum were 1.2, 1.1 and 0.6 Bq/g (dry weight), respectively.
(c) A survey of a phosphate fertilizer production facility in Ukraine revealed that the radionuclide activity concentrations in the various process materials were all less than 1 Bq/g.
(d) In Finland, the mining of a phosphate deposit with uranium and thorium mineralization is planned. The average activity concentrations in the deposit are 0.3 Bq/g for 238U and 0.5 Bq/g for 232Th.
3.4. Non-uranium mines
At a tantalite mine and processing facility in Ethiopia, the activity concentration of 238U was found to be about 0.1 Bq/g in unprocessed materials and 0.1–0.3 Bq/g in the tailings. In contrast, the tantalite concentrate had 238U and 232Th activity concentrations of 53 and 36 Bq/g, respectively.
Most rare earth elements are obtained from monazite, a mineral normally associated with a high thorium content. In Spain, a rare earths deposit comprises a particular form of monazite that does not contain high concentrations of thorium. The mining of this deposit was the subject of a radiological investigation. The mined materials were analysed for uranium and thorium series radionuclides, as well as 40K. All activity concentrations were found to be less than 1 Bq/g.
In Brazil, analyses were conducted on samples of rock, soil and underground water from eight underground mines producing agalmatolite, coal, emeralds, fluorite, scheelite, tourmaline and zinc. The mean activity concentration in the rock and soil samples from each mine ranged from 0.005 to 0.34 Bq/g for 226Ra, from 0.005 to 0.13 Bq/g for 232Th and from 0.19 to 1.3 Bq/g for 40K. The mean 222Rn activity concentration in underground water ranged from 2 to 487 Bq/L.
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In Finland, mineral deposits containing various metals of value are being mined or are being considered for mining. All the deposits have some uranium mineralization:
(1) Nickel–zinc–copper–cobalt deposit: 0.0017 wt% U (0.2 B/g 238U), Associated gypsum pond waste: 0.058–3.375 Bq/g 238U;
(2) Gold–cobalt ( two deposits): 158 ppm U (2 Bq/g 238U) and
194–347 ppm U (2.3–4.3 Bq/g 238U);
(3) Gold deposit: Up to tens of wt% U (≈4000 Bq/g 238U);
(4) Niobium–rare earths deposit: Hundreds of ppm U and Th (≈15 Bq/g 238U).
In Ukraine, samples of material were gathered at two iron ore production sites that between them incorporate six mines. Activity concentrations of uranium and thorium series radionuclides were determined. The maximum activity concentration was for 210Pb, with a value of 0.11 Bq/g. The maximum concentrations of other radionuclides were less than half this value.
Activity concentrations were also measured on waste samples from non-ferrous metal mining.
Again, the maximum activity concentration was for 210Pb, with a value of 0.044 Bq/g, while values for other radionuclides were very much lower.
3.7. Coal fired electricity generation
Ash from the coal burning process was sampled at three points within a generating plant in Turkey. The activity concentrations ranged from 0.15 to 1.15 Bq/g for uranium series radionuclides and from 0.065 to 0.16 Bq/g for thorium series radionuclides. As expected, the highest concentrations of 210Pb were found in flyash in the electrostatic precipitators. Using the
‘I-index’ screening approach widely adopted within the European Union, it was determined that the flyash could be used at proportions of up to 40% in cement without the risk of annual effective doses exceeding 1 mSv.
4. OCCUPATIONAL RADIATION PROTECTION
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has gathered data on the annual effective doses received by workers in activities involving NORM. These data are currently being updated. In the meantime, the latest available information from UNSCEAR, published in 2008, is based on data gathered up to 2002, mostly for workers in mines. This information indicates that the average annual effective dose is about 3 mSv.
4.1. Uranium production facilities
The production of uranium is a major NORM industrial activity worldwide which, after a decline in recent years, is now growing once more. An IAEA Safety Report has been developed, dealing with occupational radiation protection in uranium production facilities. This report is aimed at assisting regulatory bodies and facility operators in implementing a graded approach to the regulation of such activities and generating a common understanding between regulatory bodies, operators, workers and their representatives, and health and safety professionals. The report provides information on the various uranium production processes, the associated radiological hazards, dose assessment methods and the establishment of the overall radiation protection programme.
The IAEA has also established the Uranium Mining Exposure (UMEX) project, the general aim of which is to strengthen and enhance the radiation protection of uranium production workers. More specific aims are to increase the opportunities for optimization of
9 protection and to support quality assurance programmes across the industry. The key activities are: the development of an information system for occupational exposure; the evaluation of the current occupational radiation protection situation; and the identification of instances of good practice, opportunities for improvement and, where appropriate, actions to be implemented for assisting employers, workers, regulatory bodies and other stakeholders in implementing the principle of optimization of protection and safety. In 2012, a questionnaire was distributed to uranium producing countries worldwide. Responses were received from 36 operating companies in 20 countries, together representing about 85% of world uranium production.The responses provided information on current practices for monitoring and reporting of occupational exposure and on occupational exposures determined for 2012. The UMEX project has provided a significant amount of information on the monitoring of worker exposures in uranium production facilities worldwide and on the doses received by workers. The information on monitoring approaches can be summarized as follows:
(a) The determination of external gamma exposure is carried out mostly by individual monitoring of all exposed workers using thermo-luminescent detectors (TLDs). However, only about half of the facilities subtract background radiation, resulting in an overestimation of the exposure in such cases.
(b) Internal exposure to inhaled long-lived radionuclides in airborne dust is determined mostly by area monitoring, although significant use of personal monitoring is made. Time variations in exposure are taken into account mostly through the use of periodic monitoring. The inhaled activity is measured mostly by gross alpha counting of the captured dust particles. Where the exposure time needs to be determined as part of the dose assessment process, this is done mostly through the use of time sheets. Bioassay techniques are not widely used for routine dose assessment. The dose conversion factors used for dose assessment vary significantly between facilities.
(c) Internal exposure to inhaled short-lived radon progeny is determined mostly by monitoring of workgroups using radon progeny monitoring devices. The exposure time is established using time sheets and individual doses are assessed by assigning the workgroup average values.
The information obtained from the UMEX project shows that the average annual effective dose received by workers across uranium production facilities worldwide, weighted according to the number of workers at each facility, is less than 5 mSv. This is consistent with the data provided by UNSCEAR, as described above. It is considered unlikely that a worker will receive an annual dose of more than 15 mSv. For workers in underground uranium mines, most of the dose is received from external exposure to gamma radiation and internal exposure from the inhalation of short-lived radon progeny, with similar contributions from each. For workers in opencast uranium mines and in situ uranium recovery operations, most of the dose originates from external gamma radiation. For workers in uranium ore processing facilities, the majority of the dose originates from internal exposure due to the inhalation of long-lived radionuclides in airborne dust. The results for the various facilities highlight the need for consistency in deciding which workers to monitor. The monitoring of all workers at the facility, regardless of whether they received significant exposure, significantly affects the characteristics of the dose distribution, since the vast majority of workers receive exposures of no real concern and the average dose is not necessarily representative of the true situation. It was demonstrated that the compilation of a ‘normalized’ dose distribution (by dividing the number of workers in each dose range by the total number of workers) gives a more meaningful result that conforms closely to the expected lognormal distribution. The importance of selecting the most appropriate dose interval for the distribution was also highlighted.
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4.2. Other industrial facilities
An assessment of occupational exposures in eight non-uranium underground mines in Brazil revealed that internal exposure from the inhalation of short-lived radon progeny was the predominant contributor to the total annual effective dose. Under operating conditions (when the ventilation system was working) the annual effective dose averaged over each of seven mines, estimated from measurements of radon and its progeny over 48 h periods, ranged from 0.2 to 7 mSv. Measurements were also conducted in two mines in which the ventilation system was not working. These gave in each case an annual average effective dose of 21 mSv. A wide range of equilibrium factors between radon and its progeny — from 0.2 to 0.7 — was found, illustrating the shortcomings of using a single default value for dose assessment purposes.
Annual effective doses due to external exposure to gamma radiation, determined from dose rate measurements, ranged from 0.1 to 2 mSv.
A preliminary investigation of an opencast tantalite mine in Ethiopia indicated that workers could receive annual effective doses exceeding 1 mSv in the packaging, loading and transport areas, especially near piles of tantalite concentrate. This result reflected the relatively high activity concentrations of uranium and thorium series radionuclides measured in the tantalite concentrate and the very low concentrations in the other process materials.
At a phosphate mine and processing facility in Senegal, the annual effective doses received by workers (assessed assuming an annual exposure time of 2000 h) were found to be 2–4 mSv at most work stations but 16 mSv at the filtration unit and up to 24 mSv close to the surfaces of scaled pipes.
At a phosphoric acid plant in Zimbabwe, gamma dose rates were found not to exceed 0.22 μSv/h, indicating that the annual effective doses received by workers from external exposure would be less than 1 mSv.
During a radiological investigation of a landfill disposal site for NORM waste from titanium dioxide production, the modelling of worker exposures to external gamma radiation predicted that each worker would receive an annual dose of 1.9 mSv, of which 85% was due to external gamma exposure. Subsequently, the exposures were redetermined by on-site observations and measurements. This resulted in a very different outcome. It was found that there was no significant possibility of internal exposure, so 100% of the exposure could be attributed to external gamma radiation. This external exposure was then determined from a gamma survey of the site and the maximum annual worker dose was calculated to be 0.8 mSv.
Next, the workers were monitored individually using electronic dosimeters, from which the maximum annual dose was determined to be 0.6 mSv. Finally, the workers were monitored over a 3 month period using TLDs and this gave a maximum annual dose of 0.4 mSv — about 20% of the dose initially determined using predictive modelling. This clearly demonstrates the shortcomings of relying on modelling techniques for assessing doses received by workers.
5. DECOMMISSIONING AND REMEDIATION 5.1. Uranium production
Several presentations provided information on the decommissioning and remediation of uranium production facilities, which can be summarized as follows:
(a) An update was given of the remediation activities by the company Wismut with respect to former uranium production facilities in Germany. After 25 years of work, another 10 years were needed for remaining physical work, beyond which several more years of water treatment and monitoring would be required. Although IAEA standards were generally being followed, more restrictive measures were sometimes being applied. Large reductions
11 in the environmental impact had been achieved. The residues being generated included water treatment residues and contaminated scrap metal, rubble and soil. These residues were being used or recycled where possible but had to be disposed of as waste where necessary. The recycling of scrap metal was actually providing some economic return.
(b) Brazil’s first uranium production facility, located on the Poços de Caldas plateau, was in production from 1982 to 1995 and is now undergoing active maintenance prior to being decommissioned. The presence of sulphides in the open pit, waste rock piles and tailings deposits is generating acid mine drainage. This has resulted in significant elevations of uranium and other metals in and around the facility. A uranium concentration of 53 Bq/g was measured in sediment at a water discharge point. Elevated concentrations were also found at points downstream, although significant attenuation was observed. A hydrogeochemical and isotopic study of water sampled from 20 sampling points, together with simulation studies, has provided a large amount of information on the situation and the processes involved, including sulphate reducing bacterial action and the mobility of uranium. The groundwater has been identified as being calcic and sulphated. The main elements and their ionic form, as well as the major dissolved and precipitated minerals have been identified. The mechanisms of pyrite oxidation have been evaluated. A review of current measures for effluent control may be necessary. Preliminary results of laboratory studies were also reported. The use of limestone as a permeable barrier component demonstrated its effectiveness in reducing uranium and sulphate mobility, while the use of alkaline leaching of effluent samples achieved an 88% recovery of uranium from the effluent.
5.2. Rare earths extraction from monazite
In Malaysia, following the decommissioning of a plant for extracting rare earth elements from monazite, the site was remediated in two stages. First, the plant site was rehabilitated and then the NORM waste from the decommissioning and rehabilitation operations was disposed of in a specially constructed near-surface repository consisting of two engineered cells. The first cell was used for the disposal of decomissioning waste (contaminated soil and construction material) while the second cell was used for disposal of thorium hydroxide waste in the form of sludge after it had been stored in a temporary facility nearby. It was packaged in concrete containers. After decomissioning the temporary storage facility, the site was rehabilitated using residual activity concentration criteria of 1 Bq/g for uranium and thorium series radionuclides and 10 Bq/g for 40K, using dilution with clean soil to meet these criteria where necessary, so as to qualify for free release. On completion of the work, a single cap was constructed over both cells. Post-release monitoring of the site for gamma radiation and radioactivity in soil, water and air was carried out. The environment around the disposal site is being monitored for 2 years and institutional control will be maintained for at least 300 years.
6. MANAGEMENT OF NORM RESIDUES 6.1. General issues
The costs and liabilities associated with NORM residue management have not always been properly taken into account over the entire life cycle of mining and minerals processing facilities, especially where the radiological and environmental impacts extend far into the future. Modern financial accounting and reporting tools such as the System of Environmental–
Economic Accounting and Full Cost Accounting are now able to capture the true costs of mining and minerals processing activities. It has been demonstrated that, when the full life cycle costs are taken into account, the industry has clearly failed to maintain its former economic
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performance, as illustrated by a decline of 60% on the stock market in the past 15 years. The underlying reason for this failure seems to be the business model itself. A new approach is needed which encompasses, among other things, an environmentally sustainable, socially acceptable, affordable solution to the problem of residues.
The amount of residues generated run into many billons of tonnes. For instance, uranium production generates almost 100% ‘waste’. The corresponding percentage for phosphate production is much lower, at 25–30% of the deposit, but during chemical digestion as part of the so-called wet process the production of 1 t of phosphoric acid generates 5 t of phosphogypsum (which is still widely regarded as waste). The volume of residues is not the only problem. Regulatory bodies, as well as the public, have become fearful of the NORM legacy content, with the result that such residues are often regulated as hazardous waste even if that position contradicts the weight of scientific evidence.
To address these problems, mining and minerals processing residues should no longer be automatically referred to as waste — this important statement was repeated many times during the Symposium. Avoidance of the term ‘waste’ opens the door to value-add uses based on two complementary processing strategies:
(i) ‘Comprehensive extraction’ considers an orebody (or even a whole geological basin) as a single, complex resource and seeks to optimize returns from all co-located resources, not a single target.
(ii) ‘Zero waste’ considers the role of innovation, technology and efficient use of all resources in avoiding the generation of waste; an importent part of this strategy is the use of residues as co-products.
Citing the phosphate industry as an example, attention was drawn to the importance of recovering uranium and rare earth elements from phosphoric acid production and of treating phosphogypsum as a valuable co-product rather than as an ongoing liability (i.e. waste). While the recycling or by-product use of a NORM residue might not always be feasible at the time of its generation, it was pointed out that this situation could change in the future and consideration should be given to the possibility of storing the residue in the meantime, rather than deciding there and then to dispose of it as waste.
The dilution of a NORM residue to reduce its activity concentration may open up possibilities for its recycling or by-product use and thus avoid the need for its disposal as waste.
This is in line with the established principal of ‘dilute and disperse’. In some situations, however, insufficient material is available for dilution and there is not always a suitable market for the co-product. Furthermore, the application of the dilute and disperse principal to NORM residues still faces considerable opposition from regulatory bodies, environmental groups and members of the public. Further effort is needed to encourage the use of the dilution option where appropriate.
Management of NORM residues requires an assessment of short term human exposure as well as a demonstration that environmental criteria for long term human health protection are met. Because of the wide diversity of NORM industrial activities, risk assessments tend to be designed on a site specific basis. This leads to inconsistencies, especially in situations where previous radiological experience is lacking. To address this problem, a unified approach to environmental impact asessment is now proposed. It is argued that the situation is not as complicated as it might initially appear and that the environmental impacts can be grouped into just three basic scenarios: (i) disposal of large amounts of solid residues on relatively small areas of land, (ii) discharge of contaminated water to water bodies, and (iii) discharge of contaminated gases or airborne dust to the atmosphere. In the case of solid residue deposits of on land, the environmental impact is limited and localized and the affected environment is already irrevocably altered. In the case of liquid and gaseous discharges, the impact may be
