Revised fluences and displacements per atom (dpa) and their uncertainties were determined after re-evaluating the neutron dosimeters from forty-one pressurized water reactor (PWR) surveillance capsules. However, the actual helium concentrations will depend on the actual boron concentration in the steel. Helium production is dominated by the /sup 10/B(n.cap alpha.) reaction and ranged from 2 to 100 atomic parts per billion for most capsules. Since thermal to fast ratios were in the range of one to two, thermal neutron fluences were generally comparable to fast fluences. Improvements not previously reported include: (1) the use of more » 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. 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. 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. The use of these standards to guide selection and deployment of advanced dosimetry sets for commercial reactors is also summarized. It also describes the validation of these standards both by in-reactor testing of advanced PV cavity surveillance physics-dosimetry and by data development. This paper summarizes the applications of these standards to define the selection and deployment of recommended dosimetry sets, the selection of dosimetry capsules and thermal neutron shields, the placement of dosimetry, the methods of measurement more » of dosimetry sensor reaction products, data analysis procedures, and uncertainty evaluation procedures. These procedures and data are governed by a set of 21 ASTM standard practices, guides, and methods for the prediction of neutron-induced changes in light water reactor (LWR) PVs and support structure steels throughout the service life of the PV.
Standardized Physics-Dosimetry procedures and data are being developed and tested for monitoring the neutron doses accumulated by reactor pressure vessels (PV) and their support structures.
0 kommentar(er)
