ML060260576

E-mail, Lobel, NRR, to Ennis, NRR, VY EPU Rg 1.82 Slides

ML060260576
Person / Time
Site:	Vermont Yankee
Issue date:	01/18/2006
From:	Lobel R Office of Nuclear Reactor Regulation
To:	Richard Ennis Office of Nuclear Reactor Regulation
References
%dam200606, RG-1.082
Download: ML060260576 (15)

Text

l Rick Ennis - RG 1.82 slides Page 1 4 From: Richard Lobel To: Rick Ennis Date: 1/1 8/06 9:14AM

Subject:

RG 1.82 slides Rick I thought I may as well send you the slides now in case you have comments.

I c:\temP\GWV}00001 .TMP Page 1 Page 11 c:\temp\GW}00001 .TMP Mail Envelope Properties (43CE4D5C.109: 5: 49614)

Subject:

RG 1.82 slides Creation Date: 1/18/06 9:14AM From: Richard Lobel Created By: RML(nrc.gov Recipients owf4_po.OWFNDO RXE (Rick Ennis)

Post Office Route owf4_po.OWFNDO Files Size Date & Time MESSAGE 485 01/18/06 09:14AM ACRS REVISIONS TO RG 1.82 JANUARY 19,2006 rev l.ppt 47104 01/17/06 04:41PM Options Expiration Date: None Priority: Standard Reply Requested: No Return Notification: None Concealed

Subject:

No Security: Standard

REVISIONS TO REGULATORY GUIDE 1.82 January 19, 2006 ACRS Thermal Hydraulics Phenomena Subcommittee Richard Lobel, NRR Marty Stutzke, NRR 1

Planned Changes to RG 1.82 Rev 3 NPSH Guidance

• Revise format: Appendix for each topic

• Revise guidance on use of containment accident pressure for NPSH

• Revise and expand guidance on statistical approach

• Revise guidance on on credit for pump operation in cavitation

• Include risk-informed guidelines

• Revisions to reflect the resolution of GSI-1 91 will be done separately (at a later date) 2

Related Documents

• These documents will also be revised to be consistent with revisions to RG 1.82:

-RG 1.1

- Standard Review Plan Section 6.2.2

- NRR Review Standard for EPU 3

Current Applications

• Vermont Yankee EPU

• Browns Ferry 1/2/3 EPU

• Beaver Valley 1 containment conversion and EPU (currently credits containment accident pressure)

• Oconee 4

Revised Format

• The body of RG will be brief and written in terms of pump suction issues

• Appendices will be added for:

PWR Sump and Sump Screen Design BWR Suction Strainer Design Air Entrainment and Vortex Suppression NPSH (BWR and PWR subsections)

BWR Strainer Blockage PWR Sump Screen Blockage 5

Application of Containment Accident Pressure to NPSH-1

• Delete guidance stating that credit for containment accident pressure is acceptable if the "design cannot be practicably altered."

• Credit based on: (1) acceptably conservative deterministic analysis, and (2) acceptable risk evaluation 6

Application of Containment Accident Pressure to NPSH-2

• No limitation on time pressure is credited (reliability argument: the most likely containment failure modes occur either before or coincident with the initiating events of interest)

• Revise guidance on credit for pump cavitation to allow data from similar pumps (in terms of NPSH)

• Provide more detailed guidance for the use of a statistical approach (best estimate + uncertainty) 7

Statistical Approach

• More detailed guidance on the use of an approach which calculates a best estimate NPSH margin (NPSHA-NPSHR) and addresses uncertainty in the significant parameters

• GE topical report 8

Credit for Operation in Cavitation

• RG 1.82 currently allows operation in cavitation if prototypical pump is tested and post-test inspection shows acceptable results

• Tests done to date show no damage from such tests

• Considering a change to also accept data for pumps of similar design in terms of parameters important to NPSH 9

Risk-Informed Guidelines- I

• SRP 19, App. D invoked to request licensees to evaluate the risk of containment accident pressure credit:

• Credit could create "special circumstances" that rebut the presumption of adequate protection from compliance with existing requirements:

- Substantially increase the likelihood or consequences of accidents

- Degrade multiple levels of defense

- Involve changes for which the synergistic or cumulative effects could significantly impact risk 10

Risk-Informed Guidelines- 2

• ACRS letter of 12/12/1997 recommended that decisions to grant containment accident pressure credit be guided by a risk-informed approach that considers a broad range of accident sequences

• Consistent with NRR Office Instructions:

- LIC-1 01 , Rev. 3, "License Amendment Review Procedures"

-LIC-504,"Integrated Risk-Informed Decision-Making Process for Emergent Issues" 11

Risk-Informed Guidelines- 3

• SRP 19, App. D refers to RG 1.174:

evaluate the credit against the five key principles of risk-informed decisionmaking

• Reviewers should be mindful to:

Clearly differentiate the concept of adequate protection from the numerical risk acceptance guidelines Consider uncertainties in the risk evaluation 12

Proposed Schedule ACRS June 2006 Presentation CRGR July 2006 Draft RG for September 2006 public comment Final RG revision September 2007 issued 13