A Review of Criticality Accidents A Review of Criticality Accidents

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II. REACTOR AND CRITICAL EXPERIMENT ACCIDENTS
This section brings out errors that should be avoided
in the conduct of reactor experiments and critical
experiments. Because criticality is expected, lessons
learned from this section do not contribute directly to
the discipline of process criticality safety. Of the 38
accidents studied, 5 occurred in what must be categorized
as working reactors (the water boiler, Godiva,
Dragon, SL-1, and NRX) and 33 occurred in critical
facilities where the properties of the assemblies
themselves were being investigated.
The major change to Part II of this second revision
is the inclusion of six accidents that occurred in the
Russian Federation. Four of these involved small
uranium or plutonium metal assemblies; two occurred
with assemblies involving reactor core mockups.
One minor change in this section is the deletion of
what was listed in the prior editions as II-D.2 The
U.S.S.R, 1953 or 1954. Based on research of the listed
reference and discussions with Russian experts, it has
been concluded that the reference was not to a reactor
accident but to some other source of personnel
radiation exposure.
Some of the reactor and critical experiment accident
data are summarized in Table 11. Where possible and
appropriate, the excursion fission energy is divided into
that which was created in the spike and that which was
in the plateau. For some excursions, almost all fissions
were in the plateau; others consisted only of a single
spike.
Table 11. Reactor and Critical Experiment Accidents
Event Date Location Material Geometry Damage
Total
Fissions
II-A FISSILE SOLUTION SYSTEMS
1 12-49 Los Alamos, NM ~1 kg 235 U as uranyl Sphere, graphite None ~3 × 10
nitrate
reflected
16
2 16-11-51 Richland, WA 1.15 kg Pu as nitrate Bare sphere, 93%
filled
None 8 × 10 16
3 26-05-54 Oak Ridge, TN 18.3 kg 235 U as uranyl Cylindrical None 1 × 10
flouride
annulus, bare
17
4 01-12-56 Oak Ridge, TN 27.7 kg 235 U as uranyl
flouride
Cylindrical bare Minor 1.6 × 10 17
5 30-01-68 Oak Ridge, TN 0.95 kg 233 U as nitrate Sphere, water Local 1.1 × 10
reflected contamination
16
II-B BARE AND REFLECTED METAL SYSTEMS
1 21-08-45 Los Alamos, NM 6.2 kg δ-phase Pu Sphere with WC None (one ~1 × 10
reflector fatality)
16
2 21-05-46 Los Alamos, NM 6.2 kg δ-phase Pu Sphere with Be None (one ~3 × 10
reflector fatality)
15
3 1-02-51 Los Alamos, NM 62.9 kg U(93) metal Cylinder and
annulus in water
Minor ~1 × 10 17
4 18-04-52 Los Alamos, NM 92.4 kg U(93) metal Cylinder,
unreflected
None 1.5 × 10 16
5 9-04-53 Sarov, R.F. ~8 kg δ-phase Pu Sphere with Major core ~1 × 10
natural U reflector damage
16
6 3-02-54 Los Alamos, NM 53 kg U(93) metal Sphere,
unreflected
Minor 5.6 × 10 16
7 12-02-57 Los Alamos, NM 54 kg U(93) metal Sphere,
unreflected
Severe 1.2 × 10 17
8 17-06-60 Los Alamos, NM ~51 kg U(93) metal Cylinder with C
reflector
Minor 6 × 10 16
9 10-11-61 Oak Ridge, TN ~75 kg U(93) metal Paraffin reflected None ~1 × 10 16