DORT/TORT Analyses of the Hatch Unit-1 Jet Pum Riser Brace Pad Neutron Dosimetry Measurements with Comparisons to Preductions Made with RAMA

摘要

Regulatory Guide 1.190 for determining pressure vessel fast neutron fluence requires that the vessel fluence calculational methodology be evaluated using dosimetry measurement benchmarks. To insure the viability of the underwater welding that has been proposed for repairing Boiling Water Reactor (BWR) highly irradiated stainless and high nickel alloy vessel internals, an accurate and well benchmarked calculational method is required for determining the BWR thermal fluence. The recent Electric Power Research Institute (EPRI)/ Nuclear Regulatory Commission (NRC) measurement program performed at Hatch-1 provides both a fast and thermal neutron dosimetry data-base for benchmarking BWR fluence calculation methodologies. Under the NRC BWR Fluence Program (JCN-Y-6391), the neutron dosimetry measurements performed at Hatch-1 are being used as a data base for assessing the accuracy of calculational methodologies used to predict neutron fluence accumulated by BWR internal components and the vessel. Results from both the well established DORT/TORT computer codes and the new state-of-the-art RAMA Fluence Methodology were to be compared in order to reduce the uncertainty in fluence estimates, and in the future, to permit a better evaluation of the feasibility of underwater welding techniques of highly irradiated components.