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U.S. Department of Energy
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Fast-response cryogenic calorimeter containing a 52-KG radiation absorber. [To measure fission product radiation from 60 mg /sup 235/U foils irradiated in reactor]

Conference ·
OSTI ID:7307358
An isothermal liquid helium boiloff calorimeter containing a 52-kg copper radiation absorber, and having a time constant < 1sm was built to measure fission product beta and gamma radiation from 60-mg /sup 235/U foils irradiated in a nuclear reactor. The short response time was achieved by the large reduction in heat capacity of solids at 4/sup 0/K, and by nearly isothermal operation. Though the initial power level was approx.3 W, the maximum thermal energy storage was approx.1 joule. The Al clad foils were transported in approx.1 s, and cooled to liquid helium temperature in approx.3 s. Boil-off helium gas was warmed to room temperature in a controlled manner, and measured with a hot-film anemometer flowmeter, which was calibrated by comparison with a dry-test volume flowmeter, and by electric heating of the radiation absorber. The correction for gamma leakage from the absorber was less than or equal to 3%, and the correction at short cooling times for sample cooldown, 2.24-m activity of the Al cladding, and system response time, amounted to 3.4% at 10 s. The overall accuracy (1 sigma) of the radiation measurements is less than or equal to 2%, except at the shortest cooling time (10 s), where it rises to 4%.
Research Organization:
Los Alamos Scientific Lab., NM (USA)
DOE Contract Number:
W-7405-ENG-36
OSTI ID:
7307358
Report Number(s):
LA-UR-77-515; CONF-770801-2
Country of Publication:
United States
Language:
English