Medical aspects of criticality accident in sarov russia
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MEDICAL ASPECTS OF CRITICALITY ACCIDENT IN SAROV, RUSSIA. Module XIX. What is a criticality accident?. An unplanned event, when the neutron balance at fission is distorted and the nuclear chain reaction becomes uncontrolled. Neutron balance. Neutrons released in fission may be lost by

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What is a criticality accident
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


Neutron balance
Neutron balance

  • Neutrons released in fission may be lost by

    • escaping the container or

    • being absorbed by non-fissile materials

Module Medical XIX-24


Scheme of critical assembly

1 - fixed part

2 - fissionable material (U)

3 - reflector (copper)

4 - moving mechanism

Scheme of critical assembly

Module Medical XIX-24


Accident circumstances in sarov 17 june 1997
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


Accident circumstances
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


Accident consequences
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


Accident management
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


Medical management
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


Rapid development of early symptoms
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



Transfer to specialized clinic at biophysics institute moscow
Transfer to specialized clinic at exposure 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


Monitoring victim s radioactivity in moscow
Monitoring victim’s radioactivity in Moscow exposure

  • 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


Biological dose assessment a haematology
Biological dose assessment exposurea) 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


Biological dose assessment b cytogenetics from blood lymphocytes
Biological dose assessment exposureb) 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

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Biological dose assessment c sampling bm for cytogenetics
Biological dose assessment exposurec) 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

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Biological dose assessment d doses estimated for bm sites
Biological dose assessment exposured) 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


Treatment in specialized hospital linics of institute of biophysics moscow
Treatment in specialized hospital exposure 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

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Drugs and dosages for preventive treatment in specialized hospital
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)

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Oedema
Oedema !!! hospital

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3rd day terminal stage
3rd day: hospitalterminal 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



Dose calculation by monte carlo method
Dose calculation by hospitalMonte 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


Lessons
Lessons hospital

  • 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