ML12279A138
| ML12279A138 | |
| Person / Time | |
|---|---|
| Site: | Framatome |
| Issue date: | 10/04/2012 |
| From: | AREVA |
| To: | NRC/NRR/DNRL |
| Gleaves, B C | |
| References | |
| Download: ML12279A138 (8) | |
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Closure PIan U.S. EPR FSAR Open ltem RAI 505 Q 07.01 Single Failure SPND Purpose
) Present the schedule for U.S. EPR FSAR open items for RAI 505 Q 07.01 single failure of a self powered neutron detector (SPND)
) Confirm agreement with the NRC on the path to closure for U.S. EPR open items for RAI 505 Q 07.01-33 A
Closure Pl.n for RAl 5OS O07.01 Octobr 4. 2012 2 AREVA
Schedule for Open Items for RAI 505 Q 07.01-33 Closure Plan for RAl 505 Q07 01 Odober 4, 2012 A
AREVA RAI Question Topic/Subjst Draft to Final to NPC 505 07 01-33 SindlF frihrr. in rn SPNn 6t2At2n1a 7l?ol201a 6t?AD01a.
At3nDO13 RAI 505 Q 07.01-33
) Question 07.01-33:
OPEN ITEM Provide an evaluation of the most limiting location of the undetected single failure of a self-powered neutron detector (SPND). ln addition, identify any changes to the lnspections, Tests, Analyses, and Acceptance Criteria (ITAAC) and Combined License (COL) action items associated with the new setpoint method.
ln Attachment 2 of the letter dated, May 24, 20'l t, the applicant proposed to revise the Topical Report ANP-10287P, "lncore Trip Setpoint and Transient Methodology For U.S. EPR," Revision 0, to add the method for including the undetected SPND failure and perform necessary Chapter 15 transient analyses taking credit of this SPND-based incore low departure from nucleate boiling ration (LDNBR) and high linear power density (HLPD) trips. ln these two new submittals, the staff requests the applicant to (1) include the uncertainty analysis and method taking into account the possible undetected single failure of SPND at the most limiting location; (2) provide an evaluation of the most limiting location of the undetected single failure of SPND; (3) evaluate the impact on the DNBR undershoot due to this new SPND undetected single failure; and (4) identify any changes to the ITAAC and COL action items associated with the new setpoint method.
A Closure Plan for RAI 505 O07 01 Oclober 4 2012 4 AREVA
Objective
) Provide an overview of the planned approach to incorporate the undetected failure of an SPND in the U.S. EPRrM safety analysis bases.
Highlight where the failure is implemented Discuss the setpoint method (ANP-10287P) in conjunction with the SPND failure Describe the manner in which the planned method of trip threshold generation provides the same level of protection for the safety limits A
Closure Pl.n for RAl 505 O07 01 October 4, 2012 5 ARE\\/A
Background
) Redundancy, single failure and the SPNDs All 72 SPND signals are distributed to each of the four redundant protection system divisions The SPNDs themselves are not redundant to each other The alternative request, acceptable level of protection, and conservative setpoint selection o Detected failure
- Trip threshold shift to more restrictive value
- Threshold is lculated through application of the statistical methods to a series of random failed sensor calculations
. Undetected failure
- Low probability, non-self announcing failures may be postulated in the SPND amplifition and signal multiplition equipment
- lnclude failure of the most limiting SPND response as an initiel condition in the trip threshold determination and transient @mpensation rcnfirmation A
Closure Plan for RAl 505 O07 01 October4, 2012 6 AREVA
Background (Continued)
> U.S. EPRrM FSAR Chapter 15 Original submission did not include an undetected SPND failure as a credible single failure Non self-announcing failure within signal conditioning modules can be incorporated as proposed in the alternative request
) Alternative request approach Utilize the existing ANP-10287P methodology Modify inputs to the methods to explicitly account for the undetected failure of the most limiting SPND response A
Closure Plen lor RAl 505 Q07 01 Oclober 4, 2012 7 AREVA SPND Responses (Power Distribution3)
Other Parameters (Uncerlainties, pressure, temperature, flow,,..)
Conceptual Path Overview ANP-l0287P Re Ma_
S-RELAPS (Plant Response 15.1,'15.2, etc.)
J ANP.IO287P Trip Threshold Determination Dynamic Compensation Confirmation I
J Dynamic Compsnsation Confirmed (yrn)
FSAR Results Sensed vs. Reference (LPD & DNBR)
. Fundamental concept of the methodology
. Desire to quantify the difference between what the PS senses and the real core condition Core power distribution is provided to the methodology as simulated SPND responses o Facilitates simulation of the reference core condition and the sensed core condition with the requisite uncertainties L
PR A
AREVA Closure Plan tor RAl 505 Q07 01 oc1ober4,2012
Static Trip Threshold Determination Closure Plan for RAl 505 Q07 01 October 4, 2012 9 AREVA Conceptual lllustration of Monitored DNBR Distribution Closure Plan for RAl 505 O07 0'l October 4, 2012 10 AREVA
Exam ple Response and
PS Compensated Response lsi Min
-Trip Threshold PS Compensated Respo.se 2nd Min Trip Threslrold witlr Most Litrriting SPND Failurc The increased uncertainty in the PS response ls accounted for in the static threshold determination Time
) The reference DNBR remains the same
) The modified trip threshold will provide for an equivalent trip time that accommodates the increased uncertainty
) The safety limit is respected with the same coverage and confidence Closure Plan for RAI 505 Q07 01 October 4, 2012 l1 A AR EVA Proorieta' xample lllustration - lmbalance / Rod Drop 1of 4 Trip Threshold Modification 3.2 Best Estimate Nominal 2.5 DNBR LCO 2.1 rMB DNBR *r r_-_{
I I
'1.0 Safety Limit
. Level of protection of the safety limit is unchanged.
. The impact is seen as a reduction in operating margin Closure Plan for RAI 505 O07 01 October a. 2012 3.2 Best Estimate Nominal 2,5 DNBR LCO IMB DNBR RT 1.0 Safety Limit A
AR EVA EFR
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Summary
) The undetected failure of the most limiting SPND is implemented as a modification of the existing ANP-10287P methodology ANP-10287P describes the statistical techniques utilized in U.S. EPR setpoint methods, as well as the design basis for the incore trip and LCO functions The statistical techniques and design basis are not altered by consideration of an undetected failure The incore trip thresholds will be decreased (HLPD) and increased (Low DNBR) as dictated by the ANP-10287P methodology to provide the required safety limit protection.
ANP-10287P will be modified to reflect undetected single failed SPND
) Changes to the FSAR Update of the modified trip thresholds Modifications of Chapter 15 to describe the manner in which the
-A.
undetected SPND failure is addressed in the safety analyses.
Closure Plan [or RAl 505 O07 01 October 4, 2012 13 AREVA Schedule for Open ltems for RAI 505 Q 07.01-33 RAI Ouestion Topic/Subject Draft to Final to 505 07 01-33 Sinole failure in an SPND 6DAt)O13 7t30DO1a 6DAD013.
ano/?o13 s and inserls Closure Plan for RAl 505 O07 01 October 4, 2012
I nteraction Opportu n ities
> NRC/AREVA lnteraction Opportunities Potential AudiUPublic Meeting Mid-March 2013
. Preliminary results/status Potential Audit Mid-June 2013
. Final results A
Closure Plan for RAI 505 Q07 01 October 4, 2012 1s AREVA