Anomalies of Criticality (Rev. 2)

Technical Report · Fri Sep 06 00:00:00 EDT 1974

DOI:https://doi.org/10.2172/4257550· OSTI ID:4257550

Clayton, E. D. ^[1]

---

1. Battelle Pacific Northwest Labs., Richland, WA (United States)

During the development of nuclear energy, a number of apparent anomalies have become evident in nuclear criticality. Some of these have appeared in the open literature and some have not. Yet, a naive extrapolation of existing data, without knowledge of the anomalies, could certainly lead to potentially serious consequences. The known "anomalies" includes, but are not limited to: 1) relationship between criticality in finite spheres and reflected cubes; 2) effect of added scatterers on the criticality of infinite slabs; 3) a small mass concept whereby criticality could be achieved with less than an ounce of fissile material in the form of a single small foil ≅ 0.2 mil thick; 4) laser-induced micro-explosion involving the initiation of a supercritical event in a highly compressed, small pellet of Pu containing as little as 10^-2g Pu; 5) effects of progressive water flooding on the criticality of interacting arrays of fissile materials in storage vaults; 6) effect of mixing metal and fissile bearing aqueous solutions together in the same vault; 7) criticality of coupled fast-thermal systems composed of small plutonium metal spheres surrounded by aqueous plutonium-bearing solutions; 8) criticality of slightly enriched uranium and the negative buckling core; 9) homogeneous aqueous mixtures of ²³⁵U and ²³⁸U, wherein it would be possible to achieve criticality (over limited concentration ranges) with a smaller quantity of ²³⁵U in the form of low enriched U than if the ²³⁵U were in the highly enriched form; 10) interacting finite cubic arrays of metal units wherein an unmoderated array of 30.0% ²³⁵U enriched spheres might have a lower critical lattice density and hence ²³⁵U mass, than an array of 93.2% ²³⁵U enriched spheres; 11) effects of density changes in spherical cores with weakly absorbing reflectors (external moderation); 12) insertion of a neutron absorbing control rod into a Pu solution sphere wherein the effect of this was to cause the assembly's reactivity to initially increase as the rod entered the solution; 13) appearance of criticality unbounded regions (of infinite masses) for slightly enriched uranium; 14) criticality in the earth; 15) criticality in the universe; 16) an apparent chain reaction which took place in the Republique of Gabonaise some 100 million years ago with low (3 wt% ²³⁵U) enriched uranium. 17) criticality of even-n nuclides beginning with the naturally occurring element, $$^{231}_{91}$$Pa; 18) beyond Californium projection of the "micro" critical mass for the doubly-closed shell, super-heavy magic nuclei of the future; 19) neutron multiplication and the power reactor (four billion watts and subcritical).

• Research Organization: Battelle Pacific Northwest Labs., Richland, WA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); US Atomic Energy Commission (AEC)
• DOE Contract Number: AT(45-1)-1830
• NSA Number: NSA-31-004038
• OSTI ID: 4257550
• Report Number(s): BNWL-SA-4868(Rev.2)
• Country of Publication: United States
• Language: English

Related Subjects

*CRITICALITY-- VARIATIONS
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
22 GENERAL STUDIES OF NUCLEAR REACTORS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
Criticality
Development
Enrichment
Equipment
Handling
N52300* --Nuclear Materials & Waste Management--Handling Equipment & Procedures
Nuclear Criticality Safety Program (NCSP)
Nuclear Energy
Plutonium
Procedures
REVIEWS
Safety
Uranium