1. IAEA International Atomic Energy Agency IAEA Seibersdorf Pu-240 incident, clean-up and lessons learnt John Hunt, Rudolf Hochmann, Hugo Eisenwagner, Tobias Benesch and Christian Schmitzer. j.hunt@iaea.org HPS 2009 Meeting Minneapolis 12 - 16 July 2009

2. IAEA Pu-240/Page 2 Safeguards inspectors Safeguards samples Safeguards Analytical Laboratory IAEA safeguards operations

3. IAEA Pu-240/Page 3 Safeguards inspectors Safeguards samples Safeguards Analytical Laboratory Reference Pu, U, Am, Cf solutions (CRM) IAEA safeguards operations

4. IAEA Pu-240/Page 4 Safeguards inspectors Safeguards samples Safeguards Analytical Laboratory Reference Pu, U, Am, Cm solutions (CRM) IAEA safeguards operations Austrian Research Center

5. IAEA Pu-240/Page 5 Pu - 240 Alpha emitter Physical half-life 6563 years Biological half-lives 50 years in bone 20 years in liver. Used as tracer or reference material.

6. IAEA Pu-240/Page 6 Plutonium CRM vial

7. IAEA Pu-240/Page 7 Plutonium vial PuNO 3

8. IAEA Pu-240/Page 8 Plutonium vial PuNO 3

9. IAEA Pu-240/Page 9 Pu-240 solution

10. IAEA Pu-240/Page 10 Alpha emission and radiolysis

11. IAEA Pu-240/Page 11 Ionized water

12. IAEA Pu-240/Page 12 Recombination

13. IAEA Pu-240/Page 13 Recombination

14. IAEA Pu-240/Page 14 Pressure build-up PuNO 3

15. IAEA Pu-240/Page 15 The pressure build-up in the vial depends on: The time passed since sealing (1993 – 2008) The activity of the solution (GBq of Pu-240) The molarity of the solution (1.5 M). The air space above the solution. Pressure build-up

16. IAEA Pu-240/Page 16 The incident 3 rd of August, Sunday, a bit before 02:31 am a Pu-240 vial stored in a fire proof safe burst, and caused the breaking of a further four vials. Around 0.8 g or 6.7 GBq (0.2 Ci) of Pu-240 was released, mostly to inside the safe. The release was detected by the continuous air monitor in the room.

17. IAEA Pu-240/Page 17 The actions foreseen in the SAL emergency plan were carried out. Early in the first day it was seen that no release to the environment had happened. The incident was reported, also to the Incident and Emergency Centre of the IAEA. A press release was made. Immediate actions (first day)

18. IAEA Pu-240/Page 18 Was there a release to the environment? HEPA filter efficiency 99.999 % for a 0.3 micron particle. Total HEPA filter bank efficiency 99.999999 %

19. IAEA Pu-240/Page 19 No release to the environment The final Austrian Research Center report of 2008/09/08 states: ‘The measured values of activity of the “incident” in the environmental samples do not deviate from the routinely performed environmental monitoring results.’

20. IAEA Pu-240/Page 20 Money spent on safety related systems is money well spent. lesson learnt

21. IAEA Pu-240/Page 21 INES level 1 The IEC classified the incident as an INES level 1 anomaly. We were lucky that the incident happened on a Sunday morning.

22. IAEA Pu-240/Page 22 Visit by Dr. Richard Toohey Dr. Richard Toohey made an “expert visit” to IAEA Seibersdorf over the 8 th to the 12 th of September 2008. The objective of the visit was to review the Plutonium-in- wound measurement system and emergency procedures related to Plutonium work at the Safeguards Analytical Laboratory.

23. IAEA Pu-240/Page 23 The clean-up in three phases Safe temporary storage of other Pu vials with overpressure. Removal of the rest of the vials and clean-up of safe. Stabilization of the Pu vials with overpressure.

24. IAEA Pu-240/Page 24 Safe temporary storage The SAL inventory of reference standards was searched for similar ampoules with overpressure. 5 similar vials were found. Work-plans were prepared and approved by the IAEA Regulator.

25. IAEA Pu-240/Page 25 Modified Type B container The vials (already packed in a steel container) were stored in a modifyed type B transport container. HEPA filter

26. IAEA Pu-240/Page 26 The clean-up of the safe The safe was covered by a plastic tent, and the remaining vials were removed through a bagging-out port, as in a glove box. Positive pressure respiratory protection was used, and appropriate PPEs.

27. IAEA Pu-240/Page 27 The clean-up of the safe After the removal of the vials, the internal walls of the safe were decontaminated and finally painted. The final surface contamination was lower than 0.1 Bq/cm 2 of alpha emitters. The floor and other surfaces of the affected room were also decontaminated down to the same level.

28. IAEA Pu-240/Page 28 Doses from first and second phases Urine analysis was carried out for actinides for the staff involved in the clean-up. No Pu-240 above the detection limit was measured. The external effective doses were very low (< 10 μSv.) Many thanks to ARC medical team and fire brigade who gave us very good support.

29. IAEA Pu-240/Page 29 Third phase: stabilization

30. IAEA Pu-240/Page 30 Third phase: stabilization Proposed stabilization procedure: 1. Cool down the internal part of the modified Type B container to – 60 0 C with CO 2 (dry ice). The Pu solution will freeze.

31. IAEA Pu-240/Page 31 2. Remove the steel vial containers. 3. Transfer the steel container to a glove box. 4. Open the steel container and fill it with liquid N 2. 5. Crack the vial through remote-controlled mechanical means. Third phase: stabilization

32. IAEA Pu-240/Page 32 Vial cracking

33. IAEA Pu-240/Page 33 Lessons learnt The phenomenon of radiolysis (gas formation and pressure build-up) in Plutonium solutions is well known. However this type of event in CRM vials had not been reported in the open literature before. Therefore no safety measures were taken to prevent such an event happening (periodic pressure release). The suppliers of CRM do not inform storage problems.

34. IAEA Pu-240/Page 34 Lessons learnt – safety culture It is always important to continue learning, through seminars, congresses, reports, the internet. Learn through the problems and incidents that have happened in other facilities, and report on incidents and accidents that happen in your installation.

35. IAEA Pu-240/Page 35 Any questions or comments? j.hunt@iaea.org