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Implementation of Seismic Stops in Piping Systems

Description: Commonwealth Edison has submitted a request to NRC to replace the snubbers in the Reactor Coolant Bypass Line of Byron Station-Unit 2 with gapped pipe supports. The specific supports intended for use are commercial units designated ''Seismic Stops'' manufactured by Robert L. Cloud Associates, Inc. (RLCA). These devices have the physical appearance of snubbers and are essentially spring supports incorporating clearance gaps sized for the Byron Station application. Although the devices have a nonlinear stiffness characteristic, their design adequacy is demonstrated through the use of a proprietary linear elastic piping analysis code ''GAPPIPE'' developed by RLCA. The code essentially has all the capabilities of a conventional piping analysis code while including an equivalent linearization technique to process the nonlinear spring elements. Brookhaven National Laboratory (BNL) has assisted the NRC staff in its evaluation of the RLCA implementation of the equivalent Linearization technique and the GAPPIPE code. Towards this end, BNL performed a detailed review of the theoretical basis for the method, an independent evaluation of the Byron piping using the nonlinear time history capability of the ANSYS computer code and by result comparisons to the RLCA developed results, an assessment of the adequacy of the response estimates developed with GAPPIPE. Associated studies included efforts to verify the ANSYS analysis results and the development of bounding calculations for the Byron Piping using linear response spectrum methods.
Date: February 1, 1993
Creator: Bezler, P.; Simos, N. & Wang, Y.K.
Partner: UNT Libraries Government Documents Department

IMPLEMENTATION OF SEISMIC STOPS IN PIPING SYSTEMS.

Description: Commonwealth Edison has submitted a request to NRC to replace the snubbers in the Reactor Coolant Bypass Line of Byron Station -Unit 2 with gapped pipe supports. The specific supports intended for use are commercial units designated ''Seismic Stops'' manufactured by Robert L. Cloud Associates, Inc. (RLCA). These devices have the physical appearance of snubbers and are essentially spring supports incorporating clearance gaps sized for the Byron Station application. Although the devices have a nonlinear stiffness characteristic, their design adequacy is demonstrated through the use of a proprietary linear elastic piping analysis code ''GAPPIPE'' developed by RLCA. The code essentially has all the capabilities of a conventional piping analysis code while including an equivalent linearization technique to process the nonlinear spring elements. Brookhaven National Laboratory (BNL) has assisted the NRC staff in its evaluation of the RLCA implementation of the equivalent linearization technique and the GAPPIPE code. Towards this end, BNL performed a detailed review of the theoretical basis for the method, an independent evaluation of the Byron piping using the nonlinear time history capability of the ANSYS computer code and by result comparisons to the RLCA developed results, an assessment of the adequacy of the response estimates developed with GAPPIPE. Associated studies included efforts to verify the ANSYS analysis results and the development of bounding calculations for the Byron Piping using linear response spectrum methods.
Date: February 1, 1993
Creator: BEZLER,P.
Partner: UNT Libraries Government Documents Department

Probabilistic analysis of allowed outage times relaxation at a PWR plant

Description: Technical Specifications (TS) in a nuclear power plant are specific requirements on its day-to-day operation, designed to protect public health and safety. Two primary aspects of the TS are (1) limiting conditions of operation (LCO) with allowed outage times (AOTs) and (2) surveillance testing intervals (STIs). In recent years, there has been growing interest in the nuclear community in reexamining the TS. One of the reasons is that a significant portion of reactor downtime (plant unavailability) is attributable to the strict TS. Existing TS were derived from engineering judgement based on deterministic review; they were not directly risk-based, and their efficacy in enhancing public safety is difficult to establish. This paper presents a summary of a critical review of the Westinghouse report which proposed that AOTs for a number of safety systems at the Byron Generating Station be increased from 3 to 7 days.
Date: January 1, 1986
Creator: Cho, N.; Chu, T.; Xue, D.; Bozoki, G. & Youngblood, R.
Partner: UNT Libraries Government Documents Department

Auxiliary feedwater system risk-based inspection guide for the Byron and Braidwood nuclear power plants

Description: In a study sponsored by the US Nuclear Regulatory Commission (NRC), Pacific Northwest Laboratory has developed and applied a methodology for deriving plant-specific risk-based inspection guidance for the auxiliary feedwater (AFW) system at pressurized water reactors that have not undergone probabilistic risk assessment (PRA). This methodology uses existing PRA results and plant operating experience information. Existing PRA-based inspection guidance information recently developed for the NRC for various plants was used to identify generic component failure modes. This information was then combined with plant-specific and industry-wide component information and failure data to identify failure modes and failure mechanisms for the AFW system at the selected plants. Byron and Braidwood were selected for the fourth study in this program. The produce of this effort is a prioritized listing of AFW failures which have occurred at the plants and at other PWRs. This listing is intended for use by NRC inspectors in the preparation of inspection plans addressing AFW risk-important components at the Byron/Braidwood plants. 23 refs., 1 fig., 1 tab.
Date: July 1, 1991
Creator: Moffitt, N.E. & Gore, B.F.: Vo, T.V. (Pacific Northwest Lab., Richland, WA (USA))
Partner: UNT Libraries Government Documents Department