This report documents a plant-specific study for a BWR/4 with a Mark I containment that evaluated the potential for LOCA generated debris and the probability of losing long term recirculation capability due ECCS pump suction strainer blockage. The major elements of this study were: (1) acquisition of detailed piping layouts and installed insulation details for a reference BWR; (2) analysis of plant specific piping weld failure probabilities to estimate the LOCA frequency; (3) development of an insulation and other debris generation and drywell transport models for the reference BWR; (4) modeling of debris transport in the suppression pool; (5) development of strainer blockage head loss models for esbunating loss of NPSH margin; (6) estimation of core damage frequency attributable to loss of ECCS recirculati~on capability following a LOCA. Elements 2 through 5 were combined into a computer code, BLOCKAGE 2.3.A point estimate of overall DEGB pipe break frequency (per Ih-year) of 1.59E-04 was calculated for the reference plant, with a corresponding overall ECCS loss of NI'SH frequency (per Rx-year) of 1.58E-04. The calculated point estimate of core damage frequency (per Rx-year) due to blockage related accident sequences for the reference BWR ranged from 4.2E-06 to 2.5E-05. The results of this study show that unacceptable strainer blockage and loss of NPSH margin can occur within the first few minutes after ECCS pumps achieve maximum flows when the ECCS strainers are exposed to LOCA generated fibrous debris in the presence of particulates (sludge, paint chips, concrete dust). Generic or unconditional extrapolation of these reference plant calculated results should not be undertaken.
Portions of this document may be illegible AbstractThe BLOCKAGE 2.5 code described in t h i s User's Manual was developed by the United States Nuclear Regulatory Commission (NRC) as a tool to evaluate licensee compliance with NRC Bulletin 96-03, "Potential Plugging of Emergency Core Cooling Suction Strainers by Debris in Boiling Water Reactors". As such, BLOCKAGE 2.5 provides a generalized framework into which a user can input plant-specific and insulationspecific data for performing analyses in accordance with Regulatory Guide 1.82, Rev. 2. This user's manual describes the capabilities of BLOCKAGE 2.5 along with a description of the graphics user's interface provided for data entry. Each input/output dialog is described in detail along with special considerations related to developing and executing BLOCKAGE. Also, several sample problems are provided such that user can easily modlfy them to suit a particular plant of interest. The models used in BLOCKAGE 2.5 and their validation are presented in the accompanying NUREG/CR-6371.The BLOCKAGE models were designed to be parametric in nature, allowing the user flexibility to examine the impact of several modeling assumptions and to conduct sensitivity analyses. As a result, BLOCKAGE 2.5 results are known to be very sensitive to the user provided input. It is therefore strongly recommended that users become thoroughly familiar with BLOCKAGE models and their limitations as described in NUREG/CR-6224.iii
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A computer model of an open loop flashed steam plant for producing electrical power from a hot geothermal water supply i s documented. The model has the capability of tracing the dissolved gases, N2 and €02, throughout the plant. Sensitivity studies were performed on several o f the geothermal source, design, and atmospheric parameters u s i n g the source conditions found i n the Raft River Valley as a base case,
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