Processing of DSRS for BDC Disposal: Conditioning and Storage

1. Processing of DSRS for BDC Disposal including Conditioning and Storage Presenter Name School of Drafting Regulations for Borehole Disposal of DSRS 2016 Vienna, Austria

2. Outline of Presentation • Presentation Resources • Regulatory Framework • Definitions • Processing of DSRS: Conditioning • What is conditioning? Why condition sources? • BOSS example and requirements, • Hot cell uses and requirements • Processing of DSRS: Storage • Why store? Member state experience. • Generic requirements for storage, • Summary 2

3. Presentation Resources • International Atomic Energy Agency, BOSS: Borehole Disposal of Disused Sealed Sources – A Technical Manual, IAEA-TECDOC-1644, IAEA Vienna (2011) • International Atomic Energy Agency, Handling, Conditioning and Storage of Spent Sealed Radioactive Sources, IAEA-TECDOC-1145, IAEA Vienna (2000). • International Atomic Energy Agency, Management of Disused Long lived Sealed Radioactive Sources (LLSRS), IAEA-TECDOC-1357, IAEA Vienna (2003). 3

4. Presentation Resources • International Atomic Energy Agency, Predisposal Management of Radioactive Waste, General Safety Requirements, Part 5, IAEA, Vienna (2009). 4

5. Regulatory Framework • Basis in national statues • May be based upon IAEA documents • Many countries have national regulations for LLW disposal • Protection of the public and the environment • Examples of typical regulations governing licensing: • Public dose • Worker dose – conditioning/hot cell • Training • Isotope limits due to site safety assessment • Regulatory Body should provide guidance to the licensee on disposal issues. 5

6. Processing Definitions Conditioning – the sealing of an SRS into a capsule. Usually followed by interim storage. Storage – as the placement of the source in a facility where isolation, environmental protection and human control (e.g., monitoring) are provided with the intent that the source will be retrieved. Transfer/transport flask – a Type A transport container designed for the public domain transport of conditioned SRS and for transferring disposal packages to the disposal borehole. Exists only as a design at present. 6

7. Processing of DSRS: Conditioning • BOSS conditioning is the placing of one or more disused SRS: • within a 316L stainless steel capsule that is subsequently seal welded. Capsules are standard length and in two diameters for different sized sources. • subsequently capsule in placed into another SS container in a cavity along the centerline • Example: For disposal in Washington, a 2R container is used for the initial containment of the source. The 2R is geometrically centered in a 200 L Type 7A drum with structural grade concrete filling the void. Drum is temperature protected to allow the concrete to cure and achieve a compressive strength of at least 2500 psi. 7

8. Processing of DSRS: Conditioning Conditioning provides: • Conversion to a Special Form radioactive material for transportation, • Proper documentation, • Physical protection from damage/leakage, and • Package standardization for handling. For Cat 3 sources and lower, conditioning can take place in a lightly shielded conditioning unit. For Cat 1 or 2 sources, a shielded hot cell is needed. 8

9. Conditioning Zones & Equipment 9

10. Conditioning Areas The manned area for the conditioning operation should consist of the following five zones: • Receiving zone – receipt point & review characterization data • Transfer zone – SRS placed into capsule behind shielding (e.g., lead brick wall); • Welding zone – TIG welded behind special shield and capsule cooling area; • Leak testing zone – necessary equipment & shield • Container filling/storage zone – transfer to temporary shielded container for storage/transport. 10

11. Processing of DSRS: Conditioning Generic requirements for conditioning: • Contamination control per RB/regulations, • Receiving area – incoming transport packages are handling; surveys needed, • Transfer zones – Pb shielding bricks covered with double poly (to prevent generating mixed waste), • Ops area small; limit area for contamination spread, • Operations optimized to limit exposure from DSRS, • Ventilation system – exhaust fan over highest contamination potential to control air flow and contamination spread; HEPA filters. 11

12. Conditioning Areas The areas should be subjected to the following: • All containers within the supervised area should be checked for contamination before the campaign and at regular intervals during it. • Radiation levels within the supervised area should be established prior to the intended work (e.g. encapsulation operation). The radiation level in the transfer zone should be checked before and after the transfer of the contents of a transport or storage container to a capsule. 12

13. Conditioning Unit in South Africa 13

14. (BOSS) Hot Cell Design & Ops BOSS Hot Cell Design • One steel box inside another steel box • Annulus (1.55 m) is the bio shield; full of sand • BOSS hot cell includes a tank of water to act as a window; • Areas not viewable through the window can be seen with closed circuit TV (CCTV); Hot Cell Operations • With sand density of 1.6 kg/L, radiation levels for 1,000 Ci Co-60 SRS will be 0.045 mSv/hr on the outer wall. 14

15. Processing of DSRS: Storage • Per GSR-5, waste needs to be stored such that it can be inspected, monitored, retrieved, and preserved in a manner for its subsequent management. For long term storage, care must be taken to prevent degradation of the waste packages. • Based upon IAEA experience, conditioning of DSRS will be completed months or years ahead of disposal. Sources will then be held in a central, secure storage location. • Storage facility design will depend on DSRS inventory and the estimated time in storage. • SRS storage is unique; need qualified personnel. 15

16. Processing of DSRS: Storage • Estimated time in storage may be several decades; up to 100 years; • Unconditioned SRS – RB policy to condition SRS at the licensee’s storage facility rather than incur the risk of public transport. • Due to the robust reusable nature of transportation casks, shielded containers will be needed at the central storage location. These storage containers need not be as robust due to the controlled storage conditions. • Source needs to be packaged for package integrity. 16

17. Processing of DSRS: Storage • Package comply with regulations: • Surface dose rate and radiation zones (e.g., shielded rooms for higher dose rate packages), • Contamination surveys/control, • Markings and symbols, • ID tags. • Source and packaging must be compatible (e.g., don’t store Sr-90 in Pb pigs), • Physical controls against unauthorized intrusion, • Ventilation provided when iodine or radium sources are present. 17

18. Processing of DSRS: Storage • Shield higher dose rate packages with significantly lower dose rate packages, • Store packages in an orderly manner for easy visual identification: • Away from commonly occupied areas, • In an engineered space (e.g., floor loading, contour) • DSRS away from non-radioactive material, • Store-for-decay in separate area, and • Long term storage away from “soon to ship” inventory. • Lessons learned: Be leery of package markings in extreme environments over time. Markings disappear. Check markings at least every six months. 18

19. Summary • In order to ensure there will be no public impact after borehole facility closure, DSRS’ need to be conditioned before disposal. • Conditioning is the sealing of an SRS into a 316 L SS capsule. After conditioning, the package will most likely be placed into storage for several years/decades. • Periodic inspections are needed of the packages in long term storage as environmental conditions can degrade the package potentially leading to a leaking source. 19

20. Thank you!