IAEA International Conference on the Safety of Radioactive Waste Management

Transcription

1 IAEA International Conference on the Safety of Radioactive Waste Management BOREHOLE DISPOSAL OF DSRS IN BRAZIL Laís Alencar de Aguiar / Institute of Radiation Protection and Dosimetry - IRD Vienna, Austria, November 2016

2 BOREHOLE DISPOSAL OF DSRS IN BRAZIL This paper presents the overview of the IAEA TCP ( ) development concerning the feasibility of the BOSS concept for the Brazilian DSRS inventory, including safety and legal considerations. Project Team and affiliation: Nuclear and Energy Research Institute (IPEN), São Paulo, Brazil Eduardo Ferreira Goro Hiromoto Júlio Marumo Roberto Vicente Radioprotection and Nuclear Safety Board - Brazilian Nuclear Energy Commission (CNEN), Rio de Janeiro, Brazil Nuclear Technology Development Center (CDTN), Belo Horizonte, Brazil Carlos Carvalho Filho Francisco Rios Heidar Gharbieh Igor Pereira Paulo Rodrigues Sônia Prates Stela Cota Flávia Schenato Laís Aguiar 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 2

3 Brazilian Nuclear Energy Commission - CNEN The Brazilian Nuclear Energy Commission is a federal agency, created in 1962 (Law #4118), with administrative and financial autonomy and legal personality under public law, which has the following institutional purposes: I. Support development of the National Nuclear Energy Policy; II. Perform actions for research, development, and provision of nuclear technology and its applications for peaceful purposes as provided in Federal Law #7,781 (1989), and III.Regulate, license, authorize, supervise and control such use. The Brazilian Nuclear Energy Commission - CNEN - is the governmental body responsible for the final disposal of radioactive wastes in the whole country. The promulgation of regulation concerning waste management and disposal is also a responsibility of CNEN. 24 November 2016 IAEA INTERNATIONAL CONFERENCE ON THE SAFETY OF RADIOACTIVE WASTE MANAGEMENT 3

4 Brazilian Nuclear Energy Commission CNEN Radioprotection and Nuclear Safety Institutional Management Research and Development Regulatory Body Standarts and Guidance Research Centres and Laboratories Medical, Industries Facilities Nuclear Reactors Fuel Cicle Facility Waste Management and Disposal Raw materials and Minerals Safeguards and Physical Protection 24 November 2016 Laboratories: IRD LAPOC DSRS are stored at four nuclear research institutes of CNEN CDTN IEN IPEN CRCN-NE IAEA INTERNATIONAL CONFERENCE ON THE SAFETY OF RADIOACTIVE WASTE MANAGEMENT 4

5 Brazilian Inventory Of Disused Sealed Radioactive Sources MAIN SOURCES IN THE BRAZILIAN DSRS INVENTORY ON 31/12/2014 Quantity (unit) Radionuclide Half-life Activity (y) (Bq) (%) A total of 29 radionuclides have been identified in storage facilities for DSRS in Brazil. (1) Radioactive sources from medical, industrial and research applications (2) Radioactive sources attached to lightning rods (3) Radioactive sources attached to smoke detectors 267 Am-241 (1) E Am-241-Be (1) E C-14 (1) E+07 < Cf-252 (1) E+08 < ,093 Co-60 (1) E ,098 Cs-137 (1) E ,114 Ir-192m2 (1) E+08 < ,429 Ra-226 (1) E ,454 Am-241 (2) E+11 < ,680 Am-241 (3) E+09 < ,365 Ra-226 (2) E+10 < Ra-226 (3) E+04 < ,501 Others (1) 4,7E Total 189, E November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 5

6 Souce Activity (Bq) 1.00E Co 137 Cs Am Am Ba E Kr 3 H Cd-109 Cf-252 Cm-244 Co-60 Brazilian DSRS Inventory 1.00E Pm 90 Sr 244 Cm 63 Ni 226 Ra Cs-134 Cs-137 Fe-55 H Pu Kr-85 Ir-192m Na E+08 Ni-63 Pm-147 Pu-238 Ra-226 Ru E+06 Sr-90 Ti-44 Tl-204 C-14 Clearance 1.00E E E E E+03 Source half-life (y) 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 6

7 Preliminary Site Selection The approach for site evaluation for a borehole repository carried out in this project is presented in a specific paper Borehole Disposed of Sealed Sources: Methodological proposal for the site selection of a borehole repository in Brazil (Poster 181) Site selection, in consonance with CNEN regulation CNEN-NN-6.06, must follow a technical evaluation based on different mapping scales. CNEN NN 6.06:1989 Site Selection for the Radioactive Waste Disposal Facilities Disposal facilities (near surface repository) LILW (Short lived) 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 7

8 CNEN NN 6.06:1989 Site Selection for the Radioactive Waste Disposal Facilities Factors for selecting a suitable disposal site: a) Ecological b) Socioeconomic c) Geological d) Physiographic The preferred site must be on government land Regions of Interest Regional Analysis Preliminary Sites Technical Analysis Potential Sites Screening Candidate Sites Comparison and Ranking Preferred Sites Rejected Regions Rejected Sites Rejected Sites Rejected Sites 24 November 2016 IAEA INTERNATIONAL CONFERENCE ON THE SAFETY OF RADIOACTIVE WASTE MANAGEMENT 8

9 Preliminary Safety Assessment The preliminary safety assessment developed was strongly based on the generic safety assessment (GSA) performed by: LITTLE, R.H., VAN BLERK, J.J., WALKE, R.C., BOWDEN, R.A., Generic Post Closure Safety Assessment and Derivation of Activity Limits for the Borehole Disposal Concept, Quintessa Report QRS 1128A 6 v2.0, Quintessa Limited, Henley on Thames INTERNATIONAL ATOMIC ENERGY AGENCY, Generic Post closure Safety Assessment for Borehole Disposal of Disused Sealed Sources. IAEA Draft Safety Report, International Atomic Energy Agency, Vienna For unknown or not yet defined issues (such as site-specific geosphere characteristics), the definitions used in GSA were maintained. Important no attempt was made in this report to adjust the dimensions of the borehole components to allow physical fitting of all the Brazilian inventory. 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 9

10 Preliminary Safety Assessment The results of the IAEA (2013) document have shown that the most restrictive activity limits were obtained for the saturated disposal zone with high flow rate in a porous system, with Pu 238, Pu 239 and Am 241 the most limiting radionuclides. Considering the current Brazilian inventory and the results of IAEA (2013) document Saturated disposal zone in a porous system 5 Scenarios: 1 Design 4 Defects Flow Rate: High Medium Low Quantity (unit) Radionuclide Half-life (y) Activity (Bq) 169,506 Am E+13 7 Ba E Cf E+08 7 Cm E+09 2,093 Co E+14 3,098 Cs E Fe E H E+11 1 K E E Kr E Ni E Pm E+10 4 Pu E E+09 8,067 Ra E Sr E+11 3 Th E E+05 1 Ti E Tl E+08 1 U E E November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 10

11 Preliminary Safety Assessment The AMBER software tool was used for the preliminary safety assessment of a Brazilian borehole repository. The same model developed by Quintessa and implemented in the IAEA (2013) document was used with the same data, except for the inventory and radionuclide specific factors (CNEN regulation). Among all design and defect scenarios, the results have shown that the only case in which the predicted dose exceeded the dose constraint of 0.3 msv/y was for high flow rates condition in the porous system, with the 241 Am chain responsible for the highest dose rates. The impact on the safety assessment results, excluding all 241 Am sources from the present inventory, was also addressed and has shown that the dose rates for all cases were below the dose constraint. 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 11

12 High flow rates Dose Constraint Medium flow rates Low flow rates Dose Constraint Dose Constraint 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 12

13 Legal & Regulatory Framework Federal Law 10,308 (2001) Establishes rules for the site selection, construction, operation, licensing and control, financing, civil liability and guaranties related to the storage and disposal of radioactive waste. APPLIES TO: Storage Facility Disposal Facility ALLOWS FOR: The storage and disposal facilities will be built, licensed, operated and managed according to criteria, procedures and standards established by CNEN. CNEN is responsible for designing, building and operating radioactive waste disposal facilities (repositories). 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 13

14 CNEN NN 8.02:2014 In compliance with National Radioactive Waste Act (Law ), CNEN issued the: Establishes general criteria and basic requirements for the licensing process of storage and disposal facilities for LILW. Also includes the classification of radioactive waste according to the levels of radiation, based on the IAEA General Safety Guide #GSG-1 (2009), as well as disposal methods. 24 November 2016 IAEA INTERNATIONAL CONFERENCE ON THE SAFETY OF RADIOACTIVE WASTE MANAGEMENT 14

15 CLASS 0. Exempt Waste Radioactive Waste Classification CNEN NN 8.02:2014 (based on GSG-1:2009, IAEA) CHARACTERISTICS Activity levels or activity concentration at or below clearance levels established by CNEN. (CNEN NN 8.01 Radioactive Waste Management for LILW) CLEARANCE OR DISPOSAL unrestricted 1. Very Short Lived Waste 2. Low and Intermediate Level Waste Very short lived radionuclides (half-life 100 days) and activity levels or activity concentration above clearance levels. Activity levels or activity concentration above clearance levels and thermal power below 2 kw/m 3. Decay storage and subsequent clearance 2.1 Short Lived Waste 2.2 and 2.3 NORM 3. High level Waste 2.4 Long Lived Waste Short lived beta/gamma emitting radionuclide (half-life 30 years) and restricted long lived radionuclide concentration (limitation of long lived alpha emitting radionuclides to 3700 Bq/g for individual waste packages and an average of 370Bq/g for a group of waste packages). Waste containing radionuclides of U and Th decay series from the oil/gas industry and general mining industry, respectively, with activity levels or activity concentration above clearance level. Long lived alpha emitting radionuclides in concentrations exceeding limitations for short lived waste. Thermal power above 2 kw/m 3 and long lived alpha emitting radionuclides in concentrations exceeding limitations for short lived waste. Near Surface Disposal Near Surface Disposal or below surface defined by safety assessment (NORM packaged) Geological Disposal Geological Disposal 24 November 2016 IAEA INTERNATIONAL CONFERENCE ON THE SAFETY OF RADIOACTIVE WASTE MANAGEMENT 15

16 Licensing of storage and disposal facilities for LILW CNEN NN 8.02 administrative actions: Predisposal (storage) Disposal Radioactive Waste Class 2 (LILW): short lived waste 2.2. and 2.3 NORM (packaged) 2.4 long lived waste 24 November 2016 IAEA INTERNATIONAL CONFERENCE ON THE SAFETY OF RADIOACTIVE WASTE MANAGEMENT 16

17 Legal & Regulatory Framework The design and construction of a near surface disposal facility for LILW has been defined as priority of the National Nuclear Program. However, considering the Brazilian DSRS inventory, many of these sources may not meet the waste acceptance criteria for near surface disposal in compliance with requirements of Brazilian regulations. High activity sources containing 60 Co, 137 Cs and 90 Sr may not be suitable for shallow disposal or decay to exemption levels during a conventional institutional control period (~300 years), thus representing a possible hazard in a near surface repository. Furthermore, a large number of 241 Am sources and other long-lived radionuclides, such as 226 Ra, are of particular concern for disposal of Brazilian inventory, since longer half-life sources might require a greater degree of isolation and depth superior to 30 m normally associated with near surface disposal. The depth required for disposal will depend on the host geology of a specific site and the amount of waste to be disposed of. 24 November 2016 IAEA INTERNATIONAL CONFERENCE ON THE SAFETY OF RADIOACTIVE WASTE MANAGEMENT 17

18 Comments (1/3) In the current Brazilian DSRS inventory, 241 Am is the largest subcategory of sources with roughly 170,000 units; however, the future inventory remains unknown. The dimension of the borehole repository has not yet been defined. In particular, decisions associated to the size of the disposal container have still to be made which in turn will influence the depth of the borehole. Moreover, since the Brazilian DSRS inventory is relatively large, it may be necessary to implement more than only one borehole. 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 18

19 Comments (2/3) Since the Brazilian inventory is relatively large compared to the inventories presented in IAEA (2013) and Little et al. (2004) documents, the large configuration (capsule and containment barrier) could be considered for the Brazilian borehole repository in order to minimize its depth. The typical BOSS depth was indicated to be around 100 m [IAEA (2013), Little et al. (2004), IAEA (2004a) documents]. Nevertheless, greater borehole depths must be evaluated to fit the whole Brazilian DSRS inventory. The safety assessment of a Brazilian borehole repository is regarded as a preliminary assessment with a high level of uncertainty. 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 19

20 Comments (3/3) All range of activities and radionuclides intrinsic to national inventory of DSRS may require the establishment of further requirements and appropriate approach for long-term safety disposal and acceptability of other disposal concepts. Concerning Brazilian regulatory framework, a more specific regulation is required aiming to provide safety requirements for a licensing process applicable to disposal of other classes of waste (e.g. long-lived LILW): (a) waste acceptance criteria such as conditioning and packaging of high activity sources and Long-lived LILW; (b) site selection process following predetermined criteria, aiming the siting of the suitable host geology for other disposal options; (c) timescales for licensing including the period of active and passive institutional control. 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 20

21 Acknowledgments The authors are very grateful to: The Brazilian Nuclear Energy Commission CNEN: Nuclear Technology Development Center (CDTN) Nuclear and Energy Research Institute (IPEN) Radioactive Waste Management Division (DIREJ) Institute of Radiation Protection and Dosimetry (IRD) The International Atomic Energy Agency IAEA, in particular Stefan Joerg Mayer The Quintessa Limited Company, in particular Richard Little 24 November 2016 IAEA International Conference On The Safety Of Radioactive Waste Management 21

22 BOREHOLE DISPOSAL OF DSRS IN BRAZIL Laís Alencar de Aguiar, D.Sc. Institute of Radiation Protection and Dosimetry - IRD laguiar@cnen.gov.br / laguiar@ird.gov.br Vienna, Austria, November 2016