Decay heat from products of /sup 235/U thermal fission by fast-response boil-off calorimetry

Technical Report · Thu Sep 01 04:00:00 EDT 1977

OSTI ID:5311150

Yarnell, J L; Bendt, P J

A cryogenic boil-off calorimeter was used to measure the decay heat from the products of thermal-neutron-induced fission of /sup 235/U. Data are presented for cooling times between 10 and 10/sup 5/ s following a 2 x 10/sup 4/ s irradiation at constant thermal-neutron flux. The experimental uncertainty (1 sigma) in these measurements was approximately 2 percent, except at the shortest cooling times where it rose to approximately 4 percent. The beta and gamma energy from an irradiated /sup 235/U sample was absorbed in a thermally isolated 52-kg copper block that was held at 4 K by an internal liquid helium reservoir. The absorbed energy evaporated liquid helium from the reservoir and a hot-film anemometer flowmeter recorded the evolution rate of the boil-off gas. The decay heat was calculated from the gas-flow rate using the heat of vaporization of helium. The calorimeter had a thermal time constant of 0.85 s. The energy loss caused by gamma leakage from the absorber was less than or equal to 3 percent; a correction was made by Monte Carlo calculations based on experimentally determined gamma spectra. The data agree within the combined uncertainties with summation calculations using the ENDF/B-IV data base. The experimental data were combined with summation calculations to give the decay heat for infinite (10/sup 13/ s) irradiation.

• Research Organization: Los Alamos Scientific Lab., N.Mex. (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5311150
• Report Number(s): LA-NUREG-6713
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220100* -- Nuclear Reactor Technology-- Theory & Calculation
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
AFTER-HEAT
ALPHA DECAY RADIOISOTOPES
CALORIMETERS
CALORIMETRY
CONFIGURATION
EVEN-ODD NUCLEI
HEAVY NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MEASURING INSTRUMENTS
MINUTES LIVING RADIOISOTOPES
NUCLEI
PERFORMANCE
RADIOISOTOPES
URANIUM 235
URANIUM ISOTOPES
YEARS LIVING RADIOISOTOPES