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MEDICAL ASPECTS OF CRITICALITY ACCIDENT IN SAROV, RUSSIA

Explore the medical aspects of a criticality accident in Sarov, Russia in 1997, detailing the incident, symptoms, treatments, and biological dose assessments.

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MEDICAL ASPECTS OF CRITICALITY ACCIDENT IN SAROV, RUSSIA

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  1. MEDICAL ASPECTS OF CRITICALITY ACCIDENT IN SAROV, RUSSIA Module XIX

  2. What is a criticality accident? • An unplanned event, when the neutron balance at fission is distorted and the nuclear chain reaction becomes uncontrolled Module Medical XIX-24

  3. Neutron balance • Neutrons released in fission may be lost by • escaping the container or • being absorbed by non-fissile materials Module Medical XIX-24

  4. 1 - fixed part 2 - fissionable material (U) 3 - reflector (copper) 4 - moving mechanism Scheme of critical assembly Module Medical XIX-24

  5. Accident circumstances in Sarov, 17 June 1997 • 10:50: during construction of critical assembly, component from upper copper reflector suddenly slipped from technician’s rubber gloved hand and • fell onto lower part of assembly, already constructed and containing enriched uranium core Module Medical XIX-24

  6. Accident circumstances • Point of criticality exceeded, flash of blue light and wave of heat • 10.52: technician informed supervisors and colleagues • he thought his exposurewould be fatal Module Medical XIX-24

  7. Accident consequences • First few minutes after criticality excursion he was fully conscious and active • 10.59: initial direct measurements of neutron induced gamma radiation emitted by radionuclides in his body (mainly by 24Na) indicated a whole body dose of about 10 Gy Module Medical XIX-24

  8. Accident management • 11.00-11.09: building evacuated • 11.10: nurse arrived - Accident Report Card completed • 11.20: ambulance to local hospital Module Medical XIX-24

  9. Medical management • 11:45: Technician arrived at hospital of Sarov Occupational Medical Service within one hour of accident • experiencing nausea and began to vomit • Vomiting more frequent over two hours. Given antiemetic drugs, and vomiting stopped around 14:00 Module Medical XIX-24

  10. Rapid development of early symptoms • In 3-4 hrs patient’s general condition poor - fatigue, dizziness, headache, pallor, shivering, confusion, excessive perspiration • Rapidly invasive erythema appeared on hands with invasive oedema • Known hypotony progressed very quickly. In 3-4 hrs decreased to 70/50 and did not respond to treatment • No diarrhoea Module Medical XIX-24

  11. Typical early haematological parameters of very severe exposure Module Medical XIX-24

  12. Transfer to specialized clinic at Biophysics Institute, Moscow • On admission to this hospital, 10 hours post-exposure, patient still active, could walk and was stable in vertical position. Fully conscious but persistent fatigue and headache • First night (17–18 June), swelling of hands worsened, pain intolerable • Swelling extended to forearms Module Medical XIX-24

  13. Monitoring victim’s radioactivity in Moscow • 10 hrs post-exposure, dose rates from induced activity in victim’s body: • 30 µGy/h at head, 45 µGy/h over chest • 35–40 µGy/h over abdomen • 17–19 µGy/h in left leg • At this stage dose to whole body estimated 8-11 Gy, to hands 200-300 Gy • The 24Na activity concentration in blood was 290 Bq/mL, corresponding to mean whole body neutron dose of 14 Gy Module Medical XIX-24

  14. Biological dose assessmenta) haematology • In local Sarov Hospital, detected severe lymphopenia increased quickly: • 0.9 x 109 L-1 at 1 hour, 0.6 x 109 L-1 at 3 hours, and 0.18 x 109 L-1 at 5 hrs (Normal range: 1.5-4.3 x 109 L-1) • data indicate a dose at least 12 Gy. Suggest an extremely poor prognosis with fatal outcome Module Medical XIX-24

  15. Biological dose assessmentb) cytogenetics fromblood lymphocytes • Chromosome aberration analysis could not be performedon circulating blood lymphocytes because of deep lymphopenia at time of sampling • Also, surviving lymphocytes damaged, making culturing of cells impossible • Therefore, bone marrow cells used for assessing chromosome aberrations by direct method not requiring cell culturing Module Medical XIX-24

  16. Biological dose assessmentc) sampling BM for cytogenetics • Samples of bone marrow were taken from: • sternum • left anterior iliac crest • right posterior iliac crest • fourth thoracic vertebra • to characterize spatial dose distribution, important for treatment decisions Module Medical XIX-24

  17. Biological dose assessmentd) doses estimated for BM sites • at least 15 Gy to sternum (no metaphases seen, damaged, fully fragmented chromosomes) • 10–15 Gy to left anterior iliac crest (analysis of 12 metaphases: half had aberrations and rest fragmented chromosomes) • 6–7 Gy right posterior iliac crest (50 metaphases: 48 had multiple aberrations, two fragmented chromosomes) • about 6 Gy to fourth thoracic vertebra (three metaphases: two had fragmented chromosomes) Module Medical XIX-24

  18. Treatment in specialized hospital linics of Institute of Biophysics, Moscow • Because of drop in pressure in femoral vein, steroids administered and volume of infused fluids increased to 200 mL/h • Oligouria persisted and worsened, fluid infusion reduced to 100 mL/h • Total volume of fluid infused on second day 2800 mL, compared with urinary output 1200 mL Module Medical XIX-24

  19. Drugs and dosages for preventive treatment in specialized hospital • To prevent infection: irrigation of both hands with Lioxazol, special drug developed by pharmaceutical laboratory of Biophysics Institute (administered 1x 1-2 hrs), Acyclovir (6 mg per kg of body weight over 8 hrs), Ketoconazole (200 mg 2x day); and Ciprofloxacin (250 mg 2x day) • To prevent thrombosis: continuous perfusion of sodium heparin (20 000 IU per day) with plasma infusion • To prevent necrosis: Aprotinin (1 million IU per day) Module Medical XIX-24

  20. Oedema !!! Module Medical XIX-24

  21. Module Medical XIX-24

  22. 3rd day: terminal stage • Vascular damage --> hypoalbuminaemia, hypocalcaemia, progressive acidosis, lung oedema, hypoxaemia • 03:20, 20 June 97 (66.5 hrs after exposure) dramatic drop in blood pressure, bradycardia and death due to heart failure Module Medical XIX-24

  23. Summary of dose assessments by measurement and calculation Module Medical XIX-24

  24. Dose calculation by Monte Carlo method • Technician estimated distance of his hands from surface of critical assembly as about 5 cm and calculations were made accounting for known neutron and photon fluxes and their spatial distribution around assembly • Total dose to hands could lie between 800 and 2000 Gy. Final estimates were 1700 kerma (Gy) for neutron and about 120 Gy for gamma components Module Medical XIX-24

  25. Lessons • High n-doses may result in moderate early clinical signs, but do not necessarily indicate good prognosis • Patient died before clinical symptoms of gastrointestinal or bone marrow syndrome could develop • Death occurred within three days of exposure, not due to effects on central nervous system but on vascular system • Observe radiation safety rules! Module Medical XIX-24

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