ENS 48735

v t e ENS Event
05:00 Feb 8, 2013
Title	Part 21 - Completed Evaluation for Potential Error in Main Steam Line High Flow Calculational Methodology
Event Description	GEH recently discovered that some calculations of the choked flow rate in the Main Steam Lines (MSLs) of GEH BWRs were non-conservative, with potential effects on margins between choked flow conditions and existing MSL high-flow Nominal Trip Setpoints (NTSPs), Allowable Values (AVs), and Analytical Limits (ALs). GEH has now completed the evaluation of this condition and has determined this condition is not reportable under 10 CFR 21 for all U.S. BWR/2-6 plants. The effect of the discovered non-conservatisms in choked flow rate values was offset by unintended conservatisms in the GEH recommended formulation for calculating pressure drop across the MSL flow restrictor. As a result, GEH has determined that the flow-instrument pressure remain at conservative values (which would ensure that the associated NTSPs and AVs expressed in psid also remain at conservative values), and the MSL high-flow trip will function as designed. This update to the 60-day Interim Notification issued on December 12, 2012 (MFN 12-111 R1) will be sent to all US BWR/2-6 plants licensed using the GEH design basis and safety analysis. See previous NRC Event 48350.

ENS 48735 +/-
Where
Ge Hitachi Nuclear Energy Wilmington, North Carolina (NRC Region 1)
Organization:	Ge Hitachi Nuclear Energy
Reporting

10 CFR 21.21(d)(3)(i), Failure to Comply or Defect
Time - Person (Reporting Time:+11.53 h0.48 days <br />0.0686 weeks <br />0.0158 months <br />)
Opened:	Dale Porter 16:32 Feb 8, 2013
NRC Officer:	Pete Snyder
Last Updated:	Feb 8, 2013
48735 - NRC Website
v • d • e

v t e Emergency Notification System
Ge Hitachi Nuclear Energy with 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect
WEEKMONTHYEAR2021-02-18T04:00:00 [Table view]
[ENS list for Ge Hitachi Nuclear Energy]

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