1. Introduction. 2. Collecting DSRS

Transcription

1 International Conference on the Safety and Security of Radioactive Sources Abu Dhabi, October 27-31, 2013 French Experience of DSRS Management Bernard Sevestre Commissariat à l Energie Atomique et aux Energies alternatives (CEA) et GIP sources HA, Bâtiment 121 du CEA Saclay, BP Gif sur Yvette cedex France Abstract. Sealed radioactive sources require a safe and secure management from cradle to grave. The risk of loss of control is exacerbated when the source is no longer used: disused sealed radioactive sources (DSRS) require a safe and secure storage until their elimination. Each individual DSRS should either be recycled, or be managed as radioactive waste and find a way to a disposal. 1. Introduction Sealed radioactive sources require a safe and secure management from cradle to grave. The risk of loss of control is exacerbated when the source is no longer used. For this reason, the present paper is focused on the management of DSRS. In a first step, DSRS have to be collected in a safe and secure storage. Then their elimination has to be organized. Elimination of a DSRS can only be realized by two potential processes: recycling or management as waste. In France, the planning act of June 28, 2006, concerning the Sustainable Management of Radioactive Materials and Waste entrust to the government to develop a National Plan Management for Radioactive Materials and Waste (Plan National de Gestion des Matières et Déchets Radioactifs PNGMDR). ANDRA, CEA and a specific Waste Management Group in the framework of PNGMDR are in the process of creating the necessary disposal solutions for any type of DSRS. 2. Collecting DSRS French regulation requires that any DSRS has to be collected by the supplier of the source. In the present situation with no available waste solution, the supplier can: store the source; return the source to its own supplier who is in most cases the producer; search for a recycling opportunity. Return to supplier or producer as well as recycling may need to export the source. 3. PNGMDR and radioactive waste management in France The main PNGMDR objectives are as follows: to establish a clear definition of the waste categories to be considered as radioactive; to seek long-term management solutions for every category of radioactive waste being produced; to take due account of public concerns about the future of radioactive waste. The various types of radioactive wastes are classified according to the half-lives and radioactivity levels of the main radionuclides they contain. 1

2 With regard to half-lives, they are divided into very-short (less than 100 days), short (between 100 days and 31 years) and long (over 31 years). In France, there are six major waste categories depending on their radioactive content (activity level and half-life) as follows: high level (HL) waste consisting mainly of vitrified waste as a result of nuclear fuel reprocessing, in the order of billions of Bq/g; intermediate-level long lived (IL-LL) waste consisting mainly of cemented waste packages, in the order of millions of Bq/g; low-level-long lived (LL-LL) waste consisting mainly of graphite and radium waste, in the order of 100 thousand Bq/g; low level and intermediate level short-lived (LIL-SL) waste resulting mainly from the operation and dismantling of nuclear power plants, fuel cycle facilities, and research facilities; very low (VLL) waste having the same origin, with activity levels below 100 Bq/g; very short lived wastes resulting mainly from medical uses, which can be managed by radioactive decay, and are not considered radioactive after decay (this option is not available for DSRS) Table 1 presents the global national strategy for the management of radioactive waste: Table 1: Main long term management solutions for each waste category; shallow disposal and geological disposal are under study Activity Half life Short half life 31 years Long half-life >31 years Very Low Level Surface Disposal (CSTFA) Low Level Intermediate Level Surface Disposal (CSFMA) except for tritiated waste Dedicated shallow disposal (FAVL) Geological disposal (MAVL) High Level Geological disposal (HAVL) 4. PNGMDR and DSRS management in France; ANDRA criteria for DSRS disposal acceptance DSRS have some specific characteristics which have to be considered when the decision is taken to manage them as radioactive waste: attractiveness and concentration of activity. The consequence is that DSRS waste packages may need a specific characterization process and include radiological protection such as lead, depleted uranium, cement. 2

3 Very high activity DSRS (mainly cat I and cat II : see IAEA publication Categorization of Radioactive Sources No. RS-G-1.9) may remain dangerous after a long duration of storage or disposal. Decay from 1 TBq to 1 Bq needs 40 half-lives: table 2 gives typical examples for frequent isotopes. Table 2: decay time (in years) from 1 TBq to 1 Bq for some typical high activity DSRS Isotope 57Co 60Co 137Cs 90Sr 238 Pu 241Am 226Ra Decay time ANDRA has established criteria or draft criteria for each existing or planned disposal. CSTFA surface disposal should receive all DSRS completely decayed after 30 years: detailed criteria are in preparation and will include all DSRS with a half-life of less than 1 year. CSFMA surface disposal can receive all DSRS which present no danger after 300 years: detailed criteria are available and include all DSRS with the half-life of Cobalt-60 or less, and some DSRS with a half-life of less than 31 years, with respect to specified activity limit/source. FAVL shallow disposal potential for acceptance of DSRS is not yet established, and will depend on the safety scenarios 500 years after the disposal facility has closed. Geological disposal should be able to receive all other DSRS, with the exclusion of Tritium sources. DSRS waste packages will be oriented to HAVL or MAVL depending of the thermal output of the DSRS waste package. Tritium DSRS will need a specific solution with long interim storage due to a very low acceptance criteria in CSFMA for Tritium waste. 5. CEA Strategy For many years, the CEA has been the sole sealed sources producer in France. In 1984, high activity Cobalt-60 and Cesium-137 sources production was transferred to CIS bio international; in 1999, low activity sources production was transferred to AREVA-CERCA/LEA and eventually, the CEA stopped the production of alpha and neutron sources in Furthermore, the CEA created in 2009, together with its former subsidiary, CIS bio international, a public interest group (GIP sources HA) mainly focused on the collection, recovery and disposal of Cobalt-60 and Cesium-137 high activity sources. CEA has elaborated a strategy for the management of a very large variety of DSRS, including those collected by the GIP. DSRS are collected from French users and from some French suppliers and stored in three facilities on the basis of radiological protection criteria: Highly irradiating beta-gamma sources, most of them Cobalt-60 and Cesium-137, are collected by CISBIO facility INB29 in Saclay; High level alpha or neutron sources, most of them Plutonium-238, Americium-241, and Americium-Beryllium collected by CEA facility INB148 in Marcoule; Other sources (with low irradiation level) are collected by CEA facility CERISE located in INB47 in Saclay. 3

4 Pursuant to the PNGMDR, as revised in 2009, the CEA has started to implement elimination systems for all types of DSRS as follows: the recycling of batches of sources, in cooperation with the sources manufacturer (thus requiring their export most of the time) the return of some batches of sources to their initial producer or their country of origin (thus requiring their export); the destruction of some specific types of DSRS: Tritium sources, gaseous sources, liquid sources, and incinerable plastic or resin sources. These sources are then managed in waste processes with no more sealed source specificity. All other sources will be managed in four specific processes, derived from existing solutions that will be adapted to the specificity of DSRS; table 3 gives global indication of the quantities involved. DSRS with a half-life of less than 1 year will be evacuated to CSTFA using 1 cubic meter metallic baskets; DSRS with a half-life lower or equal to Cobalt-60, Europium 152/154 sources, and Barium 133 sources will be managed using 5 cubic meter cemented packages produced on CSFMA ANDRA site; source batches will be prepared in different types of primary containments providing adequate radiological protection; all other DSRS will be accepted in 0,9 cubic meter cemented packages produced and stored in CEA Cadarache, waiting for the availability of MAVL geological disposal; for smoke detector americium sources, two alternative solutions are under study: recycling and FAVL disposal. nevertheless some existing stockpiles of sources with high thermal output will be conditioned in 0,2 cubic meter welded drums and stored in CEA Marcoule waiting for the availability of HAVL geological disposal. This includes Stontium-90 sources from RTGs, high activity Cesium-137 sources, and Plutonium-238 sources from pacemakers. Table 3: DSRS waste package production planned by CEA Disposal Sources to be managed Number Activity (TBq) CSTFA Surface disposal Waste Package 1 m 3 Metallic basket Total Volume (m 3 ) 4 m 3 CSFMA Surface disposal < 120 watts/package m 3 Cement package 200 m 3 MAVL Geological disposal < 10 watts/package * m 3 Cemented package 160 m 3** HAVL Geological disposal < 200 watts/package ,2 m 3 Metallic drum 1 m 3 * the large numbers are Americium-241 smoke detector sources; **including 120 m 3 for historic cemented packages of 3 m 3 each CEA objective is to open the different routes for the management of DSRS as radioactive wastes within two years (three years maximum). This will require many specific authorizations. 4

5 6. PNGMDR working group A specific working group has been created in the framework of PNGMDR. This group includes representatives of all stakeholders: producers, suppliers, users, ANDRA, IRSN and ASN observers. The group has already produced a first batch of recommendations for the improvement of the global management of DSRS in France. A new report will be produced at the end of The first priority is to complete, amend or confirm the ANDRA specifications for acceptance of DSRS in the different existing or planned disposal sites. In parallel, CEA and ANDRA will review their planned waste systems for sources with the following objectives: CEA + ANDRA solutions should cover all types of DSRS; the solutions should be available and accessible to all authorized stakeholders (in most cases, the suppliers who collect DSRS from the users). ASN will review the existing regulatory framework to take into account the new situation resulting from the creation of waste management solutions for DSRS, and the feedback after ten years of practice of the 2002 revision of the Public Health Code, with respect to DSRS management. 7. Conclusions My conclusion will propose some recommendations of general interest on the basis of French experience: (a) Safe and secure interim storage is a necessary first step in any DSRS management strategy; (b) Interim storage is not a long term solution; each Country should plan for effective elimination of DSRS, using an optimized mix of the following solutions: (i) return some DSRS to the supplier or the country of origin; (ii) recycle some DSRS; (iii) manage all other DSRS as radioactive waste. (c) Management of DSRS as radioactive waste requires two conditions: (i) elaborate of a national strategy for the management of radioactive waste, and (ii) take due account of the specificities of DSRS (attractiveness and concentration ). (d) Difficult transport issues have to be solved, due to the following: (i) the lifetime of SRS and devices is much longer than that of transport agreements; (ii) International transport of very high activity DSRS in type B packages is very expensive and can easily become an administrative and logistics nightmare, with the consequence of large uncertainties on final cost. 5