Zero Power Tests, SM-1A Core III

Technical Report · Thu Apr 01 00:00:00 EST 1965

DOI:https://doi.org/10.2172/4601138· OSTI ID:4601138

Batch, M. L. ^[1]; Ball, R. M. ^[1]; Lewis, R. H. ^[1]; Pitts, T. G. ^[1]

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1. Babcock & Wilcox Co., Lynchburg, VA (United States)

The zero power tests on SM-1A Core III were performed at The Babcock & Wilcox Company's Critical Experiment Laboratory in Lynchburg, Virginia. The core was assembled using grid plates, a skirt, control rod boxes, and a shield mockup especially constructed for the tests. The results are summarized below. 1) The plant-site instrument response was established for the core loading sequence. 2) The differential and integral worths of all seven rods were measured from the initial clean critical position to the fully withdrawn position using boric acid in the moderator for holddown. The differential worth at the clean critical position (25.3 cm withdrawn) is 85 cents/cm; the total excess reactivity (Δk/k) of the core is 0.0899. 3) The critical positions for a variety of rod patterns were measured. The stuck-rod measurements showed that the core was subcritical with any three rods fully withdrawn. 4) The temperature coefficient of reactivity was measured from 20 to 70 C for both five-rod bank and seven-rod bank cases. The coefficient changes from -0.7 cents ^oC to -2.1 cents/^oC over this range. A slight difference was noted between the two cases. 5) The spare fuel assemblies were shown to have almost the same reactivity as the normal fuel assemblies have; the difference is only 2.5 cents. 6) Fast and thermal fluxes were measured from the center of the core to the mockup pressure vessel. The fast flux was attenuated by a factor of 2 x 10⁴. In absolute units, the fast flux is approximately 4.2 x 10⁴ neut/cm²-sec-watt at the pressure vessel wall. 7) Gross and fine-power distributions were measured for (9 the cold, clean core using a gamma-scan technique on fission product activity. The gross distribution used the standard elements the fine distribution used fuel plates (similar to those in the standard elements) in special "take apart" assemblies. All results are normalized to average power in the active core. 8) Power distribution was also measured in "take apart" assemblies made up of fuel plates without flux suppressors in order to evaluate the effect of the suppressors. 9) A special series of measurements was performed to compare the relative fine distributions obtained from the normal gamma scan, a very fine beta scan, and uranium foil activation. The measurements showed that all three techniques give similar data, but care must be taken in interpreting the measurements near the edge of a plate. Foil data indicated that some peaks were about 10% higher than peaks from fuel data, and in one case, a 20% higher peak was indicated near the end of the scan.

• Research Organization: Babcock & Wilcox Co., Lynchburg, VA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); US Atomic Energy Commission (AEC)
• DOE Contract Number: AT(30-1)-3466
• NSA Number: NSA-19-031531
• OSTI ID: 4601138
• Report Number(s): BAW-3466-1
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-65
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CONTROL ELEMENTS
CRITICALITY
FABRICATION
LATTICES
MEASURED VALUES
MOCKUP
PLATES
POWER
POWER PLANTS
REACTIVITY
REACTOR CORE
REACTORS
RODS
SHIELDING
SM-1A
TESTING
Nuclear Criticality Safety Program (NCSP)
Criticality
Control Element
Fabrication
Lattice
Measured Values
Power
Reactivity
Power and Power-Breeder Reactors