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

Module Medical XIX-24 - 2

Neutron balance



Neutrons released in fission may be lost by



escaping the container or



being absorbed by non-fissile materials

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Module Medical XIX-24

Scheme of critical assembly

1 - fixed part 2 - fissionable material (U) 3 - reflector (copper) 4 - moving mechanism - 4

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

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Accident circumstances



Point of criticality exceeded, flash of blue light and wave of heat



10.52: technician informed supervisors and colleagues



he thought his exposure would be fatal

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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 radionuclides in his body (mainly by by 24 Na) indicated a whole body dose of about 10 Gy

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Accident management



11.00-11.09: building evacuated



11.10: nurse arrived - Accident Report Card completed



11.20: ambulance to local hospital

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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

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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

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Typical early haematological parameters of very severe exposure

Date/hr:min 1997.06.17/12:00 14:00 16:00 22:10 1997.06.18/03:00 09:15 1997.06.19/09:35

Last saved: 2000-09-19

WBC (x 10 9 /L) 4.5

15.0

9.0

12.1

12.2

15.0

12.0

Lymphocytes (x 10 9 /L) 0.9

0.6

0.2

0.1

0.2

0.2

0.2

- 11 Module Medical XIX-24 Document in med asp (24).ppt Revision: 1 Last saved by:Istvan Turai Page 1 of 1

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

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Monitoring victim’s radioactivity in Moscow

  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

24

Na activity concentration in blood was 290 Bq/mL, corresponding to mean whole body neutron dose of 14 Gy - 13 Module Medical XIX-24

Biological dose assessment a) haematology



In local Sarov Hospital, lymphopenia increased quickly: detected severe



0.9 x 10 9 0.18 x 10 9 L -1 L -1 at 1 hour, 0.6 x 10 9 at 5 hrs L -1 at 3 hours, and (Normal range: 1.5-4.3 x 10 9 L -1 )



data indicate a dose at least 12 Gy . Suggest an extremely poor prognosis with fatal outcome

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Biological dose assessment

b) cytogenetics from blood lymphocytes



Chromosome aberration analysis

could not be

performed on circulating blood lymphocytes because of deep lymphopenia at time of sampling



Also,

surviving lymphocytes

culturing of cells impossible

damaged,

making



Therefore, bone marrow cells used for assessing chromosome aberrations requiring cell culturing by direct method not

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Biological dose assessment

c) 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, for treatment decisions important - 16 Module Medical XIX-24

Biological dose assessment

d) 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

metaphases: half had aberrations and rest fragmented chromosomes) (analysis of 12 

6–7 Gy right posterior iliac crest

(50 metaphases: 48 had multiple aberrations, two fragmented chromosomes) 

about 6 Gy to fourth thoracic vertebra

metaphases: two had fragmented chromosomes) (three - 17 Module Medical XIX-24

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, reduced to 100 mL/h fluid infusion  Total volume of fluid infused on second day 2800 mL, compared with urinary output 1200 mL - 18 Module Medical XIX-24

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 !!!

Module Medical XIX-24 Photo 3 Right hand of the victim 50 hours after the exposure - 20

Module Medical XIX-24 Photo 5. Computer tomographic image of the thorax at the level of Th-10 Note compression of the lung by pleural fluid and intensification of the lung pattern. - 21

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

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Summary of dose assessments by measurement and calculation Location

Face

Neutron radiation

Kerma (Gy) 41  12 32 Method S (n, p) 32 P Chest Back Hands

Average to body

45  5 40  1 6.7

1500  320 1700  170 8–11

14



4

Measurement (DINA) Calculation Calculation Measurement (ESR) Calculation 23 Na (n,  ) 24 Na (rapid method) (spectrometry) Absorbed dose (Gy)

Gamma radiation

Method 4.5

5.4

3.5

 0.3

2.5

 0.5

Measurement (ESR) Calculation Measurement (IKS) Calculation 4.1

100  5 120  12 Calculation Measurement (ESR) Calculation

3.5



0.3

Measurement (IKS) Module Medical XIX-24 - 23

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 - 24 Module Medical XIX-24

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!

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