CRITICALITY ACCIDENTS IN USAEC FACILITIES*

(from "Operational Accidents and Radiation Exposure Experience Within the United States Atomic Energy Commission, 1943-1970," (WASH 1192), U. S. Government Printing Office, Washington, D.C., 1971.)

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METAL SYSTEMS IN AIR

Date Location Active Material Geometry Total Fissions Cause Physical Damage $ Loss
Aug. 21, 1945Los Alamos, New Mexico 6.2 Kg delta-phase Pu Spherical core tungsten-carbide reflected ~1016 Hand stacking reflector None-
May 21, 1946 Los Alamos, New Mexico 6.2 Kg delta-phase Pu Spherical core, Be reflected ~ 3 x 1015 Hand stacking reflector None-
Apr. 18,1952 The Los Alamos Scientific Lab., New Mexico 92.4 Kg uranium metal , 93% U-235 Cylinder unreflected 1.5 x l0l6 Computation error None-
Feb. 3,1954 The Los Alamos Scientific Lab., New Mexico 53 Kg uranium metal, 93% U-235 Sphere unreflected 5.6 x l0l6 Slight warping of pieces $600
Feb. 12,1957 The Los Alamos Scientific Lab., New Mexico (GODIVA) 54 Kg uranium metal, 93% U-235 Sphere unreflected except for experiment 1.2 x l0l7 Shift of experiment Warping, oxidation near melting closeto center $2,400
Nov. 10,1961 The Oak Ridge National Lab., Tennessee 75 Kg uranium metal, 93% U-235 ~1016 Too rapid assembly None-
Mar. 26, 1963 LRL Livermore Calif. 47 Kg 93% U-235 Cylinder reflected 5 x l0l7 Too rapid assembly Assembly machine and fire effects $94,881

SOLUTION SYSTEMS

Date Location Active Material Geometry Total Fissions Cause Physical Damage $ Loss
Dec., 1949 The Los Alamos Scientific Lab., New Mexico ~ 1 Kg U-235 UO2(NO3)2 in 13.6 liters water Sphere graphite reflected 3-4 x 1016 Manual withdrawal of two poison control rods None-
Nov. 16, 1951 The Hanford Works, Richland, Washington 1.15 Kg Pu PuO2( N03 )2 in 63.8 liters water Sphere 93% full unreflected 8 x l0l6 Poison control rod run out too fast None**
May 26, 1954 The Oak Ridge National Lab., Tennessee 18. 3 Kg U-235 U02F2 in 55.4 liters water Cylindrical annulus unreflected 1 x 1017 Tilting of inner poison cylinder None-
Feb. 1, 1956 The Oak Ridge National Lab., Tennessee 27.7 Kg U-235 U02F2 in 58.9 liters water Cylinder unreflected 1.6 x 1017 Falling scram set up waves creating a critical geometry Warping of bottom of cylinder -
June 16, 1958 Y-12 Processing Plant, Oak Ridge. Tennessee 2.5 Kg U-235 UO2(NO3)2 in 56 liters water Cylinder concrete reflected below 1.3 x 1018 Wash water added to U02(NO3)2 solution None$1,000
Dec. 30, 1958 The Los Alamos Scientific Lab., New Mexico,Pu Processing Plant 3.27 Kg Pu PuO2( N03 )2 in ~ 168 liters water Cylinder water reflected below 1.5 x 1017 Agitator created a critical geometry None-
Oct. 16, 1959 Chemical Processing Plant, Idaho Reactor Testing Area 34.5 Kg U-235 ~800 liters UO2(NO3)2 water Cylinder concrete reflected below ~4 x 1019 Solution surged from safe to unsafe geometry None$61,800 (to recover contam. solution)
Jan. 25, 1961 Chemical Processing Plant, Idaho Reactor Testing Area 8 Kg U-235 UO2(NO3)2 in 40 liters water Cylinder 6 x 1017 Solution pumped from safe to unsafe geometry None$6,000
Apr. 7, 1962 Hanford Atomic Products Pu Solution Cylinder 8 x 1017 Solution over flow down unsafe geometry transfer tank $1,000
Jan. 30, 1968 Y-12 Processing Plant, Oak Ridge. Tennessee 3.3 Kg U-235 UO2(NO3)2 in 20 liters water Sphere water reflected 1.1 x 1016 Solution surged from safe to unsafe geometry None-

INHOMOGENEOUS WATER MODERATED SYSTEMS

Date Location Active Material Geometry Total Fissions Cause Physical Damage $ Loss
June 4, 1945 Los Alamos, New Mexico 35.4 Kg uranium ~83%, U-235 1/2-in. cubes Pseudosphere water reflected ~3 x 1016 Water seeping between blocks None-
Mar. 20, 1951 The Los Alamos Scientific Lab., New Mexico 2 cylinders uranium 24.4 and 38.5 Kg 93% U-235 2 cylinders water reflected 1017 Scram increased reactivity Slight oxidation -
June 2, 1952 The Argonne National Lab. 6.8 Kg U-235 oxide particles in plastic Inhomogeneous cylinder water reflected 1.22 x 1017 Manual withdrawal of central safety rod Plastic destroyed -
July 22, 1954 The Reactor Testing Area, Idaho Falls, Idaho (BORAX) U-Al plates clad with Al Inhomogeneous cylinder water moderated 4.68 x 1018 Estimate of expected excursion too low Reactor destroyed intentionally by test -
Jan. 3, 1961 Idaho Reactor Testing Area (SL-1) U-Al plates clad with Al Inhomogeneous cylinder water moderated 1.5 x 1018 Under study Extensive to reactor $4,350,000

MISCELLANEOUS SYSTEMS

Date Location Active Material Geometry Total Fissions Cause Physical Damage $ Loss
Feb. 11, 1945 Los Alamos, New Mexico UH pressed in styrex Cylinder ~6 x 1015 Reflector added and/or source too large UH3-styrex cubes swollen and blistered -
Nov. 29, 1955 Idaho Reactor Testing Area (EBR-1) 1/2-in. U-235 rods Cylinder, rods cooled by NaK 4.7 x 1017 Incorrect scram used Core molten Not reported
July 3, 1956 The Los Alamos Scientific Lab., New Mexico 58 Kg uranium 93% U-235, 2 and 5 mil foils Cylinder 3.2 x 1016 Too rapid assembly None-
May 18, 1967 Los Alamos, New Mexico U-235 in graphite Cylindrical 4 x 1016 Improper Proceedures None-

* For additional information on these accidents, see previous TID-5360 series and "A Review of Criticality Accidents" by W. R. Stratton,