Advanced reactivity measurement facilities. A description and performance evaluation
The Advanced Reactivity Measurement Facilities, ARMF-I and ARMF-II, are nearly identical critical facilities and are used almost exclusively for measuring reactor physics parameters, such as reactor-spectrum cross sections and resonance integral cross sections. They are, therefore, designed to (a) have large statistical weights for fuels and poisons, (b) be mechanically stable enough to produce reproducible reactivity measurements, and (c) have sensitive instrumentation capable of measuring very small reactivities. These facilities are swimming-pool-type reactors having light-water moderated cores made up of platetype fuel elements containing fully enriched U-235. The facilities are located at the National Reactor Testing Station in Idaho near the Materials Testing Reactor (MTR). Being located near the MTR permits measurements on short- lived fission products and transmuted isotopes. By use of the capsule transfer tube connecting the MTR and ARMF canals, a capsule can be transferred from the MTR hydraulic rabbit to the ARMF and prepared for reactivity measurements in 15 minutes. Both ARMF reactors use a servo-controlled regulating rod for reactivity measurements rather than a pile oscillator. The reactivity effect of a capsule placed in the reactor is determined from the resultant regulating rod displacement. In order to make the regulating rod a precise measuring device, its drive and position instrumentation includes no gears. Because the rod rotates about a vertical axis, it can be driven by a torque motor, the armature of which is attached directly to the rod. A digital shaft-angle encoder, the position transducer, also attaches directly to the rod. Characteristics important to facilities used for reactivity measurements are statistical weights and expected measurement errors. Typical statistical weights in the ARMF are (a) 2.8 x 10/sup -2/ DELTA k/k per g of natural boron, (b) 6.36 x 10/sup -4/ DELTA k/k per g o f U-235, and (c) 1.16 x 10/sup -4/ DELTA k/k per g of gold inside a cadmium shield. Expected measurement error (standard deviation) for a single 4.5 minute capsule measurement is 10/sup -7/ DELTA k/k. (13 references) (auth)
- Research Organization:
- Phillips Petroleum Co., Idaho Falls, Idaho (USA). Atomic Energy Div.
- DOE Contract Number:
- AT(10-1)-205
- NSA Number:
- NSA-29-020103
- OSTI ID:
- 4330818
- Report Number(s):
- IDO-17005
- Resource Relation:
- Other Information: Orig. Receipt Date: 30-JUN-74
- Country of Publication:
- United States
- Language:
- English
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