The Richard repository [8.4] is situated in a former limestone mine near the town of Litomerice (60 km NW of Prague). The mine consists of more than 40 km of galleries and passage ways. Chambers and corridors, adopted for use as a disposal facility in a separate part of the mine complex were excavated in a thin (3 - 5m) layer of limestone some 40 - 60 m below the surface. This layer is insulated from top and bottom by 30-60 m layer of water impermeable marlstone (hydraulic conductivity is 3x10-9 - 4.9x10-11 m.s-1).
Although generally dry, the mine is infiltrated by rainwater at several places. This water is collected in a drainage system running along the access gallery and, after being monitored, it is released to the environment. The underground water table is approximately 50 m below the disposal level in a sandstone formation. The temperature and relative humidity in the repository is essentially constant at 10°C and 95% respectively. To support mechanical stability of the mine, a reinforced concrete frame was installed at the most exposed places (see Figure 8-4).
Figure 8-4: The Main Access Gallery of the Richard Repository
The total volume of available underground spaces exceeds 17 000 m3. The present gross volume of the chambers for disposal of radioactive waste is approximately 9 950 m3 and the estimated volume of radioactive waste that could be disposed of is about 5 500 m3. By 2003, about 62% of this capacity was used. The radioactive inventory of the waste is summarized in Table 8-1.
Table 8-1: The Radioactive Inventory in the Richard Repository as of 2003 Nuclide Total inventory
limit
Drum activity limit (200 litre drum)
Total disposed of inventory
% of limit The highest activity of any drum disposed
% of limit
[Bq] [Bq] [Bq] % [Bq] %
3H 1.00E+15 1.00E+13 5.794E+13 5.79 7.001E+12 70.01
14C 1.00E+14 3.00E+10 7.223E+12 7.22 3.380E+08 1.13
90Sr 3.00E+14 3.00E+11 3.262E+12 1.09 4.891E+09 1.63
137Cs 1.00E+15 6.00E+11 4.201E+14 42.01 3.649E+10 6.08
alpha 2.00E+13 1.00E+08 1.400E+13 70.01 9.943E+07 99.43
NA = not applicable
Since 1964, radioactive waste from institutional applications has been disposed in the Richard repository. Waste acceptance criteria were changed several times since repository commissioning based on legislative requirements valid at the time. Simple waste packages were used in the early stages of operation. There is a lack of detailed information on the packages disposed of during the 1960’s and 1970’s. Most waste was in steel drums (50, 60, 80, 100, or 200 litre capacity).
In the 1990’s, “sandwich construction” was developed for non-solidified waste consisting of a 100 litre drum grouted into a 200 litre drum. With this method, a 5 cm thick concrete barrier surrounds the waste in each package.
Waste packages are placed into chambers, some of which are closed with simple walls without provision for access or active control of their physical or radiological properties. Spaces between packages not filled (see Figure 8-5).
Figure 8-5: View of a Disposal Chamber in the Richard Repository
The repository has operated for almost 40 years without accident, but it needs systematic maintenance and upgrading as its operation will continue for decades. The following lists the main improvements that have been completed recently:
• mine reconstruction (conservation of underlying structures, mine entrance, ventilation, lights, electric supply),
• surface are reconstruction and upgrading (new administration building with an information centre, new fences, refurbished hot cells and operations building, road resurfacing),
• radiation protection (new monitoring programme and measuring devices, controlled zone regime),
• records (extension of record content with tracking, conditioning and chemical properties data), and completion of additional hydrological investigation and updating of the Safety Report for the repository).
Further upgrading will focus on the following issues:
• adoption of two chambers for accepting dimensionally non-standard waste arising during refurbishment and decommissioning of radioactively contaminated laboratories,
• reconstruction of a hot cell for conditioning disused sealed sources,
• design and demonstration of sealing a chamber (methodology development to demonstrate a feasibility of safe closure of disposal chambers, specification of appropriate filling materials and a proposal of adequate implementation technology for closing the repository), and
• introduction of new waste acceptance activity limits (see Table 8-2).
Table 8-2: Radionuclide Acceptance Criteria for the Richard Repository since 2004 Radionuclide Activity of bulk
waste [Bq/kg]
Activity of non-conditioned waste in
sandwich type packages [Bq]
Activity of conditioned waste in
200 l drums [Bq]
Total inventory limit [Bq]
3H 3.109 1.1012 1.1013 1.1015
14C 1.107 3.109 3.1010 1.1014
36Cl 3.106 1.108 1.109 1.1012
90Sr 1.108 3.1010 3.1011 1.1014
99Tc 1.105 5.107 5.108 2.1011
129I 1.104 2.106 2.107 2.108
137Cs 1.108 3.1010 3.1011 1.1015
Total activity of long lived alpha-emitting nuclides
3.104 1.107 1.108 2.1013
References for Section 8
8.1 Agence nationale pour la gestion des déchets radioactifs, “The VLLW disposal facility”
http://www.andra.fr/interne.php3?id_article=325&id_rubrique=112 8.2 British Nuclear Fuels Limited, “Drigg”
http://www.bnfl.com/index.aspx?page=568
8.3 Envirocare, “Tour Envirocare’s Treatment and Disposal Facility”
http://www.envirocareutah.com/pages/educate/tour/tour.php
8.4 Radioactive Waste Repository Authority (Czech Republic), “Information on Repositories”
http://www.vidivici.cz/surao2/index.php?c=86&s=tisk
9 THE MANAGEMENT OF SPENT/DISUSED SEALED RADIOACTIVE SOURCES
Previous issues of this Status and Trends report identified problems associated with the management of sealed radioactive sources (SRS). In particular, concerns were expressed regarding SRS that are taken out of service (disused or spent SRS) and for which no proper management system exists. It was pointed out that accidents with disused or spent SRS account for a significant proportion of all radiation accidents and they can lead to severe injuries or death.
Issue 1 presented the basic concepts for SRS management per the requirements of Article 28 (Disused Sealed Sources) of the Joint Convention [2.1]. Under Article 28, two requirements must be addressed:
• the Contracting Party must demonstrate that the possession, remanufacturing, or disposal of disused sealed sources takes place in a safe manner, and
• the Contracting Party permits disused sealed sources to re-enter into its territory to a manufacturer qualified to receive and possess the disused sealed sources.
Issue 1 concluded that effective national regulatory systems, implemented by knowledgeable people, are the key to preventing accidents with SRS. Such systems must:
• include rigorous control of the SRS inventories,
• ensure the adequate planning of actions to be carried out in the event of loss of control of an SRS, and
• the capability to carry out such actions.
Issue 1 also pointed out that the safe disposal of disused sources is basically a national responsibility.
For countries that have no disposal facilities, safe disposal may require transferring disused/spent SRS to another country - normally the country of the supplier - that has the infrastructure to dispose of them safely.
Issue 2 described ‘The Borehole Disposal Concept” and provided an update of the compilation of data for the “International Catalogue of Sealed Radioactive Sources”.
Issue 3 provided overviews of SRS management in various countries (Argentina, Belarus, Chile and USA). It also included a discussion of the “Proposed EU Directive on Orphan SRS” and an overview of the work of the SRS Task Group of the Forum for Nuclear Cooperation in Asia.
This Section of the current issue of the Status and Trends report:
• discusses the return of spent/disused SRS to suppliers (see Subsection 9.1),
• discusses the development of a mobile installation for handling sealed high activity radioactive sources (SHARS) (see Subsection 9.2),
• provides examples of Member State programmes and experiences with SRS management (see Subsection 9.3), and
• describes and provides examples of IAEA assistance to Member States in the area of SRS management (see Subsection 9.4).
9.1 Topical Issue: Return of Sources to Suppliers