Updated reevaluations of the dosimetry for reactor pressure vessel surveillance capsules

The goals of this Hanford Engineering Development Laboratory (HEDL) Reactor Dosimetry Center work are: (1) to apply new ASTM recommended physics-dosimetry analysis methods and new data being developed for light water power plant surveillance, and (2) to provide improved neutron exposure values for the metallurgical data bases that support the analysis of the integrity of reactor pressure vessels. Neutron dosimetry data from surveillance capsules from several pressurized water reactors (PWR) and boiling water reactors (BWR) were reevaluated, resulting in revised values of fluences and displacements per atom (dpa) and their uncertainties. Improvements not previously reported include: (1) the use of improved a priori neutron spectra, (2) correction of errors in the spectrum weighting of the thermal neutron cross sections, (3) the inclusion of thermal neutron fluences and their uncertainties, and (4) calculated helium content for a generic pressure vessel chemical composition. Since thermal to fast ratios were in the range of one to two, thermal neutron fluences were generally comparable to fast fluences. Uncertainties ranged from 9 to 62%. Helium production is dominated by the 10B(n,α) reaction and ranged from 2 to 100 atomic parts per billion for most capsules. However, the actual helium concentrations will depend on the actual boron concentration in the steel. 10 refs