MEDICAL ASPECTS OF CRITICALITY ACCIDENT IN TOKAIMURA, JAPAN

1. MEDICAL ASPECTS OF CRITICALITY ACCIDENT IN TOKAIMURA, JAPAN Module XIX

2. Tokaimura accident 30 September 1999 • Two workers – Mr. O & Mr. S – mixed 19% enriched uranyl nitrate (U3O8) solution in precipitation vessel • To enhance reaction time, poured 7-times more uranyl nitrate into the tank (17 kg instead of 2.4 kg permitted) • Process long not performed Module Medical XIX-(25)

3. Module Medical XIX-(25)

4. Accident • 30 Sep, 1999, 10:35: sudden criticality occurred with about 40 L U3O8solutionin tank • All three workers present saw “blue flash” • Gamma alarm sounded, Mr.O and Mr.S left processing room • Mr.Y reported accident by telephone, then left Module Medical XIX-(25)

5. Physical consequences • No explosion; some release of gaseous fission products (Kr, Xe) in room • No significant off-site release of fission products • Criticality reaction continued (pulsing) some 17 hours until cooling water jacket (reflecting neutrons back) drained • Gamma levels induced by fission products still too high to permit entry to processing room atend October 1999 Module Medical XIX-(25)

6. Medical evacuation • Ambulance arrived in 11 minutes (10:46) and departed for National Mito Hospital • All three taken by helicopter to NIRS Hospital, arriving at 15:25 (5 hrs PI) • Mr.O (35 yrs) transferred to ICU at Univ. of Tokyo Hospital 2 October • Mr.S (40 yrs) transferred to Hospital of Medical Research Institute at Univ. of Tokyo 4 October Module Medical XIX-(25)

7. Symptoms: Mr.O • Severe vomiting immediately • Loss of consciousness almost immediately • Diarrhoea within first hour, continued for 4 days • Erythema & oedema of face, trunk and arms within hours • Lung oedema on Day 3; pleural effusion on Day 6 • Blister formation started after 3 weeks • Kidney failure in weeks 3 and 4; high bilirubine and creatinine levels Module Medical XIX-(25)

8. Treatment: Mr.O • Reverse isolation, antibiotics & GIT sterilization (Ciprofloxazin + Acyclovir) • G-CSF, continued platelet and erythrocyte transfusions • PBSCT from HLA-identical sister (6/6 match) on 5 October; some marrow recovery after 1 month • Survival considered unlikely Module Medical XIX-(25)

9. Terminal status of Mr.O • Severe skin damage, more than 50% of body surface • Lost 2 L of fluid per day through diarrhoea • Cardiac arrest in early December, but resuscitated • Died due to multiple organ failure 21 December 1999, 82 days post-exposure Module Medical XIX-(25)

10. Symptoms: Mr.S Module Medical XIX-(25)

11. Patient S WBC CBT Lymphocyte Platelet Module Medical XIX-(25)

12. 1 2 3 4 w 2 3 4 5 6 7 8M BM failure CBT Mixed chimerism Skin transplantation 2nd degree burn CMV infection Pneumonia / sepsis Pulmonary fibrosis Skin sclerosis Multi-organ failure GI tract bleeding Clinical course of Case S Module Medical XIX-(25)

13. Clinical course of burn in patient S 13wk Transplantation 3 wk 4wk 11wk >21wk Module Medical XIX-(25)

14. Treatment of terminal status of Mr. S • Parenteral feeding from Feb 2000 • Attached to respirator from late Feb due to pneumonia and breathing difficulty • Placed on a dialysis machine mid-April • Died 27 April 2000 due to multi-organ failure Module Medical XIX-(25)

15. Symptoms: Mr.Y • Slight nausea after four hours • Moderate granulocytosis and lymphocytopenia • Hypoxaemia due to heavy smoking (2 pack/day) Module Medical XIX-(25)

16. Treatment: Mr.Y • G-CSF and antibiotic therapy • Marrow recovery after second week • Platelet infusions • Psychotherapy for severe anxiety • Full recovery after 1 month • Released from NIRS Hospital on Day 80 (19 Dec 1999) Module Medical XIX-(25)

17. Provisional dose estimation on 4th day Case O Case S Case Y Prodromal > 8Gy 4-6Gy < 2Gy signs (~20Gy) Lymphocyte > 10Gy 6-10Gy 1-3Gy >20Gy 7.8Gy 2.6Gy PCC 9Gy 5Gy 1.2Gy Na-24 neutron* 15.4GyEq 8.4GyEq 2.0GyEq If RBE is 1.7 *Parameters for calculations were adopted from the draft of the IAEA report on the Sarov Accident. Module Medical XIX-(25)

18. g Relative Case dose Neutron Activity ( Bq/g) dose ( Kerma) ( (Gy) 4 O 8.30 x 10 5.5 8.5 4 S 4.33 x 10 2.9 4.5 4 Y 1.23 x 10 0.81 1.3 Average neutron energy 1MeV ICRP Pub. 74 1cm dose equivalent neutron : g = 9 : 1 Dose assessment from Na-24 in blood Gy / (Bq/g Na-24) = 6.58E-5 Module Medical XIX-(25)

19. Final dose estimates, Gy Totaldose*, GyEq 17 8 2 Module Medical XIX-(25)

20. On-site effects • 70 other workers exposed • Highest doses to those involved in removing water from cooling jacket • 20 persons received 50-100 mSv • Others received 50 mSv or less Module Medical XIX-(25)

21. Off-site effects • Au-198 measured in gold necklace in a house 200m distant • 7 workers at warehouse 80m distant received doses of 2-9 mGy, based on Na-24 in blood • Blood tests on 1800 nearby residents in first week - all negative Module Medical XIX-(25)

22. Response of Japanese Government • Maintain commitment to nuclear power • Establish radiological emergency response capability at regional medical centre in each prefecture with nuclear facility • Increase oversight and inspection • Possibly take legal action against JCO • Japanese specialists visit USA to consult emergency response capabilities • Conduct NTC in March 2000 and IAEA/RCA RTC on radiation emergency medicine in NIRS, Chiba, 20-24 Aug 2001 Module Medical XIX-(25)

23. Lessons learned (1) • Cases O & S kept alive much longer than thought possible earlier • Acute phase of ARS can be controlled • 　by prompt medical intervention • 3. To save highly irradiated victims, • need to develop strategies for preventing • subacute and chronic radiation damage • such as microangiopathy, fibrosis • and sclerosis in soft tissue and organs Module Medical XIX-(25)

24. Lessons learned (2) • 4. Donor-derived stem cells differentiated into endothelial cells of aorta in case ‘O’. • Replacement of stem cells may facilitate tissue regeneration • 5. Transplantation of tissue stem cells (e.g. myoblast stem cells, epithelial stem cells, bone marrow stem cells) could be treatment of choice for radiation accident victims in future Module Medical XIX-(25)