Chairman F. NITSCHE
TRANSPORT AND DISPOSAL REQUIREMENTS FOR SOME SELECTED WASTE SHIPMENTS TO
THE KONRAD REPOSITORY
F. NITSCHE, F.W. COLLIN Bundesamt für Strahlenschutz, Saltzgitter, Germany
Abstract
The Konrad repository is planned to accept radioactive waste with negligible heat generation originating from nuclear power plant operation, decommissioning, nuclear fuel cycle and application of radioisotopes in medicine, industry and
research. Standardized packagings of different sizes and requirements are used for shipment and final disposal.
Preliminary waste acceptance criteria were derived from safety analyses for the Konrad repository. These criteria for some typical wastes are compared with transportation
requirements based on IAEA-Regulations in particular for waste form, packaging and radionuclide inventory. The range of applicability of LSA/SCO-regulations for these waste shipments is considered and some aspects concerning the further
development of these regulations within the IAEA Revision Process of Safety Series No. 6 are discussed.
1. INTRODUCTION
The Konrad repository in Germany is planned to dispose of radioactive waste with negligible heat generation, that means radioactive waste of low and intermediate level
activity. The waste arises from nuclear power plant operation, decommissioning, nuclear fuel cycle industry and application of radioisotopes in medicine, industry and research.
In the whole waste management field different processes have to be considered like conditioning, interim storage and final disposal together with transportation as the linking process. It is necessary to pay attention to all the relevant requirements of these processes in particular for a safe waste management.
In the following the transportation and disposal requirements for waste shipments to the planned Konrad
repository will be described and compared. The application of LSA-transport regulations to those waste packages will be discussed and some conclusions will be drawn concerning some aspects of the further development of the corresponding transport regulations.
2. DISPOSAL REQUIREMENTS FOR WASTE PACKAGES
The safety principles and basic criteria for underground disposal in Germany are described in /!/. Based on these
criteria a site specific safety assessment of the Konrad repository was performed taking into account the operational phase of the repository as well as the post-operational
period. It includes the waste packages intended to be disposed of, the technical concept of the repository and the overall geological situation /2/. Based on the results of this
assessment preliminary waste acceptance criteria were derived concerning waste form, packaging and radionuclide inventory /3/.
The permissible radionuclide inventory per waste package is specified
(a) for various waste forms and packaging tightness levels resulting from safety assessment of normal operation, and (b) for various waste form groups and packaging integrity
levels (waste container class I and II) resulting from safety assessment of incidents, and
(c) for various packaging types to limit decay heat resulting from safety assessment of decay heat influence upon host rock, and
(d) for various packaging tyes to quarantee criticality safety in case of fissile contents resulting from criticality safety assessment.
These limits are independent of one another and the most restrictive one has to be applied /3/.
The waste itself must be in a solid form, has to meet further basic requirements and must be assigned to one of the six waste form groups:
01 - Bitumen and plastic product 02 - Solid matter
03 - Metallic solid matter 04 - Compacted waste
05 - Cemented / concreted waste 06 - Concentrates
as described in detail in /3/. Especially the following two waste form requirements are of relevance to transport issues.
This is the requirement of a uniform activity distribution in case of cemented/concreted waste and the limitation of fissile material concentration to 50 g per 0.1 m^ of waste volume.
There are various types of packagings as shown in Table I and Figure 1 which are standardized according to operational requirements of the Konrad repository. Two of the main basic requirements /3/ they have to meet are
to comply with the external dimensions and gross volumes as give in Table I, and
to be designed in such a way that, when filled, they can be stacked over a hight of at least 6 m without adverse effect their tightness and integrity.
The waste packagings can be assigned to two waste
container classes having different integrity levels concerning their mechanical and thermal stability under incident
conditions in addition to the basic requirements /3/:
Waste container class I:
The design of the waste packagings is such that, up to an impact velocity of 4 m/s, their integrity is
Table I:
o\
Standardized packagings for the disposal of radioactive waste in the Konrad repository /2/
No
Cylindrical concrete packaging type 1 Cylindrical concrete packaging type II Cylindncai cast iron packaging type 1 Cylindrical cast iron packaging type II Cylindrical cast iron packaging type 111 Container typel ') Stacking height 1400 mm for KIK type
Container materials are eg sheet steel, reinforced concrete or cast iron.
1 1
Cylindrical cast iron packaging (type II)
Fig. 1: Basic design of standardized packagings for radioactive waste /2/
preserved to an extent that in the case of a subsequent thermal impact the access of oxygen to the waste form is so limited that flammable waste forms with melting points above 300°C do not burn away with a naked flame, but pyrolyse.
Waste container class II: The design must
- withstand a dropping from a height of 5 m onto an unyielding target in such a way that the leak rate after the drop does not exceed 10~5 Pa-m3/s,
- ensure in the case of fire with a temperature of 800°C during one hour that the leak rate prior to the fire is less than 10"-1 Pa'm-Vs and that the integral leakage rate from the gas plenum of the packaging during the fire and a cooling phase of 24 hours does not exceed a value of 1 mole.
Finally each waste package must not exceed the following dose rate and contamination limits, according to /3/:
Dose rate limits:
at surface - maximum value : 10 mSv/h at surface - mean value : 2 mSv/h at l m distance from cylindrical packages : 0.1 mSv/h at 2 ra distance from containers : 0.1 mSv/h The non fixed surface contamination is limited to
0.5 Bq/cm2 for alpha emitters having an exemption limit1) of 5 x 10^ Bq 50 Bq/cnr for beta emitters and electron
capture nuclides having an exemption limit1) of 5 x 106 Bq
5 Bq/cm2 for other radionuclides
Based on all these waste acceptance requirements a safe handling and disposal of all waste packages in the Konrad repository is ensured.
3. TRANSPORT REQUIREMENTS FOR WASTE PACKAGES
The radioactive waste in Germany has to be shipped according to the GGVS /4/ on road and the GGVE /5/ on rail, which are based on the IAEA Transport Regulations, Safety Series No. 6 (SS6) /6/.
The regulations for low specific activity material (LSA) of SS6 are mainly applied in case of waste shipments which leads to the following requirements for the relevant waste packages.
a) the waste form has a limited specific activity and can be assigned to LSA-II or LSA-III category according to para 131 (b) or (c) of SS6.
" Exemption limit according to the germaji radiation protection ordinance
U)
In case of LSA-II the activity is distributed throughout the waste form and the estimated average specific
activity does not exceed 10~4A2/g.
In case of LSA-III it is required that
(i) The radioactive material is distributed throughout a solid or a collection of solid objects, or is essentially uniformly distributed in a solid compact binding agent (such as concrete, bitumen, ceramic, etc.);
(ii) The radioactive material is relatively insoluble, or it is intrinsically contained in a relatively insoluble matrix, so that, even under loss of packaging, the loss of radioactive material per package by leaching when placed in water for seven days would not exceed 0.1 A,/ and
(iii) The estimated average specific activity of the solid, excluding any shielding material, does not exceed 2 x 10 A,/g.
b) LSA-II and LSA-III material has to be shipped in
industrial packagings Type 2 and 3 (IP-2, IP-3) according to para 426 of SS6. They must meet the general design requirements (para 505-514) and, in addition,
in case of IP-2 the free drops test (para 622) and the stacking test (para 623), and
in case of IP-3 all Type A tests (paras 621-624) and Type A design requirements (paras 523-537) for solids. By these tests it is demonstrated that the package can withstand normal conditions of transport.
Alternatively freight containers may also be used as IP-2 or IP-3 provided they meet the general design
requirements and the ISO 1496/1-1978 requirements ("Series 1 Freight containers - Specifications and
Testing - Part 1: General Cargo Containers") according to para 523.
c) The total quantity of LSA material in a single IP-2 or IP-3 package shall be so restricted that the external radiation level at 3 m from the unshielded material does not exceed 10 raSv/h (para 422). In addition in case of combustible solid LSA-waste in IP-2 or IP-3 the total activity per conveyance is limited to 100 Aj (para 427).
d) IP-2 or IP-3 waste packages must not exceed the following external radiation and contamination limits :
Dose rate limits:
(i) under exclusive use conditions:
- at the package surface :10 mSv/h - at the external surface of
the conveyance : 2 mSv/h - at 2 m from the ext. surface
of the conveyance : 0.1 mSv/h (ii) under non exclusive use conditions:
- at the package surface : 2 mSv/h - at l m from the package
surface : 0.1 mSv/h
• at the external surface of the conveyance
• at 2 m from the ext. surface of the conveyance
: 2 mSv/h : 0.1 mSv/h The non fixed surface contamination is limited to
- 4 Bq/cm for beta and gamma emitters and low toxicity alpha emitters, and
-0.4 Bq/cm^ for all other alpha emitters If radioactive waste materials can be classified as surface contaminated object (SCO) according to para 144 of IAEA Regulations than also IP-2 packagings have to be used with the requirements as decribed above for LSA-material.
4. COMPARISON AND APPLICATION OF DISPOSAL AND TRANSPORT REQUIREMENTS TO WASTE PACKAGE SHIPMENTS
A waste package intended to be disposed of in the Konrad repository has to meet both transport and disposal
requirements. In comparing both the following conclusions can be drawn concerning the main criteria of a waste package.
a) External radiation and surface contamination level:
These criteria are limited in a similar way, so that in most cases compliance with transport requirements results also in compliance with disposal needs.
b) Waste form characteristics:
Basically each waste form group may be categorized as LSA-Material provided that compliance with LSA-Material defintion (see chapter 3.a)) can be demonstrated. In case of waste form group 05 e.g. uniform activity distribution is already required by disposal needs, which is also an important criteria for LSA-Material. To classify such waste as LSA Material it remains to check specific activity limits and in case of LSA-III leachability criteria (chapter 3.a)(ii)).
Due to the disposal limitation of fissile material concentration to 50 g per 0.1 mj which is in compliance with the transport requirement of fissile exempted material (para 560 (d) /6/) such a waste package is excepted from transport requirements for packages containing fissile material, provided the activity is uniformly distributed.
c) Activity inventory:
The activity limits are specified differently. For disposal, as described in chapter 2, there are various limits derived from considerations on normal operation,
incidents, decay heat and criticality, depending in particular on waste form and package characteristics. For transportation, as described in chapter 3, the activity inventory is limited by the specific activity of waste according to LSA-II or LSA-III specifications in an IP-2 or IP-3 packaging and by the limit of 10 mSv/h at 3 m from the unshielded waste contents. In addition, in case of combustible waste the total activity limit per
conveyance of 100 An has to be considered. All these limits have to be obeyed and the most restrictive one determines the permissible activity inventory of the waste package. This has to be done based on the real waste package specifications in particular the radionuclide mixture contained in the waste and the material and the geometry of the waste and the packaging.
As a simplified example those activity limits are given in Tables 2 and 3 for Co-60 and Cs-137 as relevant nuclides of the activity inventory of waste from nuclear power plant operation. In this case the total activity for most of the waste forms is mainly restricted by the external unshielded radiation limit of 10 mSv/h from transport requirements and by the decay heat limits from disposal requirements.
In principle, compliance with this 10 mSv/h radiation limit is to be expected for waste shipments to the Konrad repository, because the standardized packagings have a limited shielding capability. The cylindrical concrete packagings are designed with a wall thickness up to 200 mm and the cylindrical cast iron packagings up to 160 mm wall thickness. Experience with those waste package from nuclear power plant operation showes that the unshielded contents meets the 10 mSv/h criteria 111.
packaging
For disposal, as described in chapter 2, the package has to meet basic requirements which take into account normal operation conditions of the repository and in addition the mechanical and thermal test requirements of waste container class I or II representing assumend incident conditions within the Konrad repository. For transport
(see chapter 3.b)) general design requirements and specific test requirements of IP-2 or IP-3 package have to be met, to demonstrate that the waste package can withstand normal conditions of transport including minor mishaps.
In comparing these requirements the following conclusions may be drawn. The IP-2 or IP-3 qualification of a package gives high credit to meet the basic package requirement from disposal and in particular meets the mechanical integrity requirements under impact velocity condition of 4 m/s for waste container class I up to a package mass of 10 t (height of free drop is more than 0.8 m). In
addition, for waste container class I qualification, the
Table II: Activity limits per waste package in Bq from disposal requkements for Co-60 and Cs-137
class II, for all waste form groups
Table III: Activity limits per waste package from transport requirements (LSA-Material for Co-60 and Cs-137 Total activity limit according to the
external radiation limit of 10 mSv/h at 3 m from the unshielded waste
depending on material (binding agent) and geometry of waste (e.g. incase of Co-60 for concreted waste about
1 x 1012 Bq... 4 x 1012 Bq per waste package)
behaviour of the waste package under fire conditions (800°C, Ih) has to be taken into account.
For waste container class II the test requirements are much more severe. But in that case it has taken into account that activity inventories are permitted which exceed the LSA Material specification, resulting in the necessity to use a Type B package for transport which is required to withstand severe accident conditions.
On the basis of model data provided by waste generators, categorized and summarized according to /8/, an estimation concerning the applicability of LSA-criteria to planned waste package shipments to the Konrad repository was performed. It comprises waste with negligible heat generation from
reprocessing, nuclear power plant operation, decommissioning, research centres, nuclear industry and collecting depots.
Using these model data on activity inventory and waste volume it can be expected that more than 95 % of the waste complies with LSA-requirements concerning the limits of specific activity and dose rate at 3 m from the unshielded waste volume.
5. CONCLUSIONS
For radioactive waste intended for disposal in the planned Konrad repository both transport and disposal
requirements have been taken into account in the qualification of the waste package. Concerning the shipment of those waste packages with negligible heat generation it can be expected that more than 95 % of the waste complies with LSA-transport regulations of Safety Series No. 6 /6/ regarding the limits of specific activity and dose rate at 3 m from the unshielded waste volume. Taking into account both transportation and disposal requirements the following conclusions can be drawn with respect to some aspects of the further development of LSA/SCO-requirements discussed within the current revision process of Safety Series No. 6 /9/.
(a) It seems to be more appropriate to keep the present dose rate limit of 10 mSv/h at 3 m from the unshielded LSA/SCO-Material (/6/, para 422) instead to introduce a new limit on the basis of a multiple of A-^ as proposed in /9/.
(b) Waste packages of the container type (see Table 1) are designed according to ISO-Standards but they don't need to meet necessarely ISO-dimension requirements. Dimensions are specified according to technical and operational needs in storage, transport and disposal. To take account of those dimensions the alternative IP-2/IP-3 qualification of freight containers according to para 523 of SS6 should also be applicable to containers with other than ISO-dimensions, provided their external dimensions don't exceed the maximum dimension specification of ISO-Standard.
(c) In case of waste package shipments with negligible heat generation to the Konrad repository there seems to be no need to introduce a so called "transport system approach"
/9/ in the Transport Regulations.
REFERENCES
/!/ Bundesminister des Innern: Sicherheitskriterien für die Endlagerung radioaktiver Abfälle in einem Bergwerk, Bundesanzeiger 35 (1983) no. 2, 45-46
111 BERG, H.P., BRENNECKE, P., The Konrad Mine. The Planned German Repository for Radioactive Waste with Negligible Heat Generation, BfS-ET-6/90, Salzgitter 1990
/3/BRENNECKE, P., Anforderungen an endzulagernde radioaktive Abfälle (Vorläufige Endlagerungsbedingungen, Stand: April 1990 in der Fassung Oktober 1993) Schachtanlage Konrad -BfS-ET-3/90-REV-2, Salzgitter, Oktober 1993
/4/ Verordnung über die innerstaatliche und grenzüber-schreitende Beförderung gefährlicher Güter auf Straßen
(GefahrgutverOrdnung Straße - GGVS) vom 22.7.1985, zuletzt geändert durch die 4. Straßen-Gefahrgut-Änderungsverordnung vom 13. April 1993 (BGBl. I S. 448)
/5/ Verordnung über die innerstaatliche und grenzüber-schreitende Beförderung gefährlicher Güter mit Eisenbahn
(Gefahrgutverordnung Eisenbahn - GGVE) vom 22.7.1985, zuletzt geändert durch die 4. Eisenbahn-Gefahrgut-Änderungsverordnung vom 05. Mai 1993 (BGBl. IS. 678) /6/Regulations for the Safe Transport of Radioactive Material,
1985 Edition (As Amended 1990), International Atomic Energy Agency, Vienna, 1990
/?/GESTERMANN, G., GNS Essen, personal communication
/8/BARD, CH., NOACK, W., Mengengerüst der radioaktiven Abfälle für ein repräsentatives Jahr der Einlagerung in der
Schachtanlage Konrad, ET-IB-52, Salzgitter, April 1992 /9/HOPKINS, D., Chairmen's Report "Technical Committee Meeting
on Issues Related to Low Specific Activity Materials and Surface Contaminated Objects (LSA/SCO), IAEA, TC. 845, Vienna, 11-15 October 1993
INVENTORY AND CHARACTERISTICS OF CURRENT AND PROJECTED LOW-LEVEL RADIOACTIVE MATERIALS AND WASTE IN THE UNITED STATES OF AMERICA A. BISARIA, R.G. HUGOS, R.B. POPE, R. SALMON, S.N. STORCH
This paper addresses the quantities and forms of low-level radioactive wastes (LLW) and mixed low-level wastes (mixed LLW) which have been generated and could yet be generated in the U. S. and which could require packaging and transport at some time in the future to storage and/or disposal sites. The current inventory of buried and stored LLW and mixed-LLW in the U. S. that needs to be, or already has been disposed of, in surface facilities was approximately 4.5 million m3 in 1991. The inventory of LLW is projected to grow to approximately 6.4 million m3 by the year 2000, and to approximately 25 million m? by the year 2010. This will result in an average growth in LLW inventories requiring packaging and transport of about of 0.2 million m, per year through 2000, and more than 1.8 million 1% per year during the first decade of the next century. The majority of this growth will result from environmental restoration activities of U. S. Department of Energy facilities. The paper also addresses Greater-rhan Class C LLW and Special Case LLW which will require disposal in other than surface facilities. Efforts are still underway in the U.
S. to better understand the classification and quantities of these materials, but it currently appears that there could be as much as 1 million m3 of these materials which will require packaging and transport in the future.
The Integrated Data Base (TOB), under U.S. Department of Energy (DOE) funding and guidance, provides an annual update of compiled data on current and projected inventories and characteristics of DOE and commercially owned radioactive wastes. The data base addresses also
The Integrated Data Base (TOB), under U.S. Department of Energy (DOE) funding and guidance, provides an annual update of compiled data on current and projected inventories and characteristics of DOE and commercially owned radioactive wastes. The data base addresses also