A Review of Criticality Accidents A Review of Criticality Accidents

exact configuration, concentration, and amount of oil
injected into the central pipe of the oil reservoir from
the pump are not well known. The total number of
fissions for both excursions was estimated by fission
product analysis to be about 1.2 × 1015 .
From 1 July until the accident, the following
procedural violations occurred:
1. The temperature recording instruments of the main
cylinders were turned off.
2. The main cylinders were cooled by manually pouring
the liquid nitrogen directly onto the iron shot
and not through the coil as procedure required. This
resulted in significant temperature gradients within
the main cylinders and, as a consequence, to misleadingly
low temperature readings because the
thermometer was adjacent to the liquid nitrogen
pour point.
3. Cooling of the intermediate cylinders was no longer
being performed.
The dose to the operator was estimated to be about
200 rad, and only mild radiation sickness symptoms
followed. No one else received measurable doses, and
there was no equipment damage nor contamination as
a result of the accident.
26
Table 7. Results of γ-Radiation Exposure Rate Measurements at Oil Reservoir
Date
(1961) Time
14 July 12:00
13:30
15:25
17:30
20:10
23:15
Elapsed Time from
Second Excursion
(min)
270
360
475
600
760
945
Exposure
Rate (R/h) Notes
36.0
25.2
14.4
14.4
11.2
9.0
15 July 12:00 1710 3.6
16 July 10:00
15:00
17 July 11:00
15:00
3030
3330
4530
4770
18 July 07:00 5730 0.9 Draining of oil reservoir begun
19 July 08:00 7230 0.3 Draining of oil reservoir completed
1.8
1.8
1.1
1.1