ML020520639

Fqa Methodology & Shutdown Margin During Physics Tests Methodology

ML020520639
Person / Time
Site:	Prairie Island
Issue date:	01/25/2002
From:	Nazar M Nuclear Management Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NAD-PI-003, Rev 0, NAD-PI-004, Rev 0
Download: ML020520639 (17)

Text

Committed to Nuclear Excellence Nuclear Management Company, LLC Prairie Island Nuclear Generating Plant 1717 Wakonade Dr. East 9 Welch MN 55089 January 25, 2002 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 FQA Methodology and Shutdown Margin During Physics Tests Methodology By letter dated December 11, 2000, Prairie Island submitted proposed Improved Technical Specifications (ITS). In support of certain of the proposed specifications, two new methodologies were developed. These two new methodologies are described in detail in Attachments 1 and 2. discusses the method by which the required Shutdown Margin (SDM) during PHYSICS TESTS initiated in MODE 2 shall be established for Prairie Island.

PHYSICS TEST Exception - MODE 2 was incorporated in Prairie Island proposed ITS, specification 3.1.8. One requirement of the proposed specification is that the SDM remain within the limits provided in the Core Operating Limits Report (COLR) during the performance of the PHYSICS TESTS. The purpose of Attachment 1 is to describe the method by which the SDM limit during physics testing is established for inclusion within the COLR.

Attachment 2 discusses the method by which a factor, FQA, is to be determined. FQA is the factor to increase FQw(Z) in the event measurement indicates that the maximum over z [FL(Z)] has increased since the previous evaluation of FQo(Z). Proposed ITS specification 3.2.1, Heat Flux Channel Factor, (FQ(Z)), requires that, when measurements indicate that the maximum over z of L()] has increased since the

USNRC NUCLEAR MANAGEMENT COMPANY, LLC January 25, 2002 Page 2 previous evaluation of FQc(Z), either:

(1) a factor - FQ, specified in the COLR - must be applied to increase FQW(Z), or (2) flux map measurements must be taken every 7 effective full power days (EFPD).

After application of FQA, FQW(Z) must meet the limits specified in the COLR. If this requirement is not met, flux map measurements must be taken every 7 EFPD until the maximum over z [M has not increased, rather than every 31 EFPD as is normally required. Attachment 2 describes the method by which FQA is determined.

Prairie Island seeks NRC approval of the two methodologies described in Attachments I and 2 in support of our conversion to ITS.

In this letter we have made no new Nuclear Regulatory Commission commitments.

Please contact Jeff Kivi (651-388-1121) if you have any questions related to this letter.

Mano K. Nazar Site Vice Preside t Prairie Island N lear Generating Plant c: Regional Administrator- Region Ill, NRC Senior Resident Inspector, NRC NRR Project Manager, NRC J E Silberg Attachments:

1. NAD-PI-003, "Prairie Island Nuclear Power Plant Required Shutdown Margin During Physics Tests," Revision 0.

2. NAD-PI-004, "Prairie Island Nuclear Power Plant Fw (Z) Penalty with Increasing Lc)] Trend," Revision 0.

Fq & SDM methodology.DOC

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Prairie Island Nuclear Power Plant Required Shutdown Margin During Physics Tests NAD-PI-003 Revision 0 January, 2001 Nuclear Management Company Nuclear Analysis and Design Copyright © 2001 by Nuclear Management Company

Prairie Island Nuclear Generating Plant Required Shutdown Margin during Physics Tests NAD-PI-003 Revision 0 January, 2001 Date: 0/

Prepared by:

Keith G. Dehnbostel Reviewed by: ac2. & ';1.-, Date:

I-/a- 2-00/

H. Oley Nelson Approved by: I *.e. L Date: /

'I

/< -g,(

iff A.'B/nneau /

NAD-PI-003, Rev. 0 Page I of 6

ABSTRACT This document is a Topical Report describing the method by which the required Shutdown Margin (SDM) during PHYSICS TESTS initiated in MODE 2 shall be established for the Prairie Island Nuclear Generating Plant.

NAD-PI-003, Rev. 0 Page 2 of 6

LEGAL NOTICE This report was prepared by or on behalf of Nuclear Management Company (NMC). It is intended for use by NMC personnel only. Use of any information, apparatus, method, or process disclosed or contained in this report by non-authorized personnel shall be considered unauthorized use, unless said personnel have received prior written permission from NMC to use the contents of this report. With respect to unauthorized use, neither NMC, nor any person acting on behalf of NMC:

a. Makes any warranty or representation, express or implied, with respect to the accuracy, completeness, usefulness, or use of any information, apparatus, method or process disclosed or contained in this report, or that the use of any such information, apparatus, method, or process may not infringe privately owned rights; or

b. Assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method, or process disclosed in the report.

Page 3 of 6 NAD-PI-003, Rev. 0

TABLE OF CONTENTS 1.0 IN TR OD UCTION .......................................................................................................... 5 2.0 BA CKG R OU ND ............................................................................................................ 5 3.0 M ETH O D OLO GY .......................................................................................................... 5 4.0 B A SES .................................................................................................................................... 5 5.0 SU M M A RY ............................................................................................................................ 6 6.0 REFEREN CES ....................................................................................................................... 6 Page 4 of 6 NAD-PI-003, Rev. 0

1.0 INTRODUCTION

This document discusses the method by which the required Shutdown Margin (SDM) during PHYSICS TESTS initiated in MODE 2 shall be established for the Prairie Island Nuclear Generating Plant.

2.0 BACKGROUND

As part of the change to Improved Standard Technical Specifications (ISTS) for Prairie Island, specification 3.1.8: PHYSICS TESTS Exceptions - MODE 2 was incorporated. One requirement of this specification is that the SDM remain within the limits provided in the Core Operating Limits Report (COLR) during the performance of the PHYSICS TESTS.

The purpose of this document is to discuss the method by which the SDM limit during physics testing is established for inclusion within the COLR.

3.0 METHODOLOGY For the ISTS, the required SDM during physics testing will be set as 0.5% Ak. This SDM value will be used to determine the limiting reactor configuration allowed during physics testing. The limiting configuration will take into account Rod Cluster Control Assembly (RCCA) positions, reactor thermal power and Reactor Coolant System (RCS) loop average temperature as allowed by specification 3.1.8: PHYSICS TESTS Exceptions - MODE 2.

From the limiting reactor configuration, the ability must be maintained to take the reactor 0.5% Ak subcritical in the event of a reactor trip in which all RCCAs that are not inserted or partially inserted drop into the reactor core with the exception of the single RCCA of highest reactivity worth, which is assumed to be fully withdrawn. The required SDM, 0.5% Ak, shall be incorporated within the COLR and the reactor shall never be taken to a more limiting configuration during physics testing.

4.0 BASES The basis for incorporating a restriction on the allowed reactor configuration during physics testing is to ensure that there is sufficient trippable reactivity to bring the reactor to a subcritical condition at any point during physics testing even if the highest worth RCCA is fully withdrawn. There is no specific event or accident that is being protected against for which a specific shutdown margin is required. The purpose of physics testing is to ensure that the operating characteristics of the core are consistent with the design predictions and that the core can be operated as designed. A value of 0.5% Ak shutdown margin was chosen Page 5 of 6 NAD-PI-003, Rev. 0

event to provide additional margin in ensuring that the reactor can be taken subcritical in the remains fully of a reactor trip by action of the control rods alone if the highest worth RCCA withdrawn.

range of When determining the limiting reactor configuration, consideration is given to the two thermal power and RCS temperature allowed by specification 3.1.8 since these of control rod parameters may slightly impact SDM. Consideration is also given to the range measured by patterns allowed during physics testing. For example, when RCCA worths are in the reactor the boration/dilution technique, all control bank RCCAs may be fully inserted reactor to a core. The shutdown bank RCCAs may also be slightly inserted to return the during critical configuration if the RCS boron concentration has been slightly over-diluted the control bank measurements.

5.0

SUMMARY

SDM shall be The required SDM during physics testing will be set as 0.5% Ak. The required limiting incorporated within the COLR and the reactor shall never be taken to a more configuration throughout physics testing.

6.0 REFERENCES

Physics

1) NSPNAD-8101-A (latest approved revision), Qualification of Reactor Methods for Application to Prairie Island, October 2000 Page 6 of 6 NAD-PI-003, Rev. 0

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Prairie Island Nuclear Power Plant F*(Z) Penalty with Increasing Trend NAD-PI-004 Revision 0 January, 2001 Nuclear Management Company Nuclear Analysis and Design Copyright © 2001 by Nuclear Management Company

Prairie Island Nuclear Generating Plant F W (Z) Penalty with Increasing [FC(Z)

Q. .Trend

~KtZT NAD-PI-004 Revision 0 January, 2001 Prepared by: /e11411 Date: I/ /4 OO [

KeýihG!De~l'bostl Reviewed by: Date:

H. Oley Nelson Approved by: Date: 6'Zi**/C Cliff . Bonneau NAD-PI-004, Rev. 0 Page I of 7

ABSTRACT This document is a Topical Report describing the method by which a factor, FQA, is determined.

FQA is the factor to increase F~v (Z) in the event measurement indicates that the maximum over z

[FQ(Z)] has increased since the previous evaluation of FC (Z).

NAD-PI-004, Rev. 0 Page 2 of 7

LEGAL NOTICE This report was prepared by or on behalf of Nuclear Management Company (NMC). It is intended for use by NMC personnel only. Use of any information, apparatus, method, or process disclosed or contained in this report by non-authorized personnel shall be considered unauthorized use, unless said personnel have received prior written permission from NMC to use the contents of this report. With respect to unauthorized use, neither NMC, nor any person acting on behalf of NMC:

a. Makes any warranty or representation, express or implied, with respect to the accuracy, completeness, usefulness, or use of any information, apparatus, method or process disclosed or contained in this report, or that the use of any such information, apparatus, method, or process may not infringe privately owned rights; or

b. Assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method, or process disclosed in the report.

NAD-PI-004, Rev. 0 Page 3 of 7

TABLE OF CONTENTS 1.0 IN TRODU CTION ................................................................................................................ 5 2.0 BACK GROUND .................................................................................................................. 5 3.0 M ETH OD OLOGY ............................................................................................................... 5 4.0 BA SES .................................................................................................................................. 6 5.0 SUM M ARY .......................................................................................................................... 7 6.0 REFEREN CES ..................................................................................................................... 7 NAD-PI-004, Rev. 0 Page 4 of 7

1.0 INTRODUCTION

This document discusses the method by which a factor, hereafter referred to as FQA, shall be determined. FQA is the factor to increase F6v (Z) in the event measurement indicates that the maximum over z L has increased since the previous evaluation of Fc (Z).

2.0 BACKGROUND

Improved Standard Technical Specification (ISTS) 3.2.1: Heat Flux Hot Channel Factor (FQ(Z)) requires that when measurements indicate that the maximum over z of L QO] has increased since the previous evaluation of FQ (Z), either a factor FQ , specified in the Core Operating Limits Report (COLR), must be applied to increase Frv (Z) or flux map measurements must be taken every 7 Effective Full Power Days (EFPD). After application of FQA, F~v (Z) must meet the limits specified in the COLR. If this requirement is not met, FFZ(Z)1 flux map measurements must be taken every 7 EFPD until the maximum over z [ I has not increased, rather than every 31 EFPD as is normally required. The purpose of this document is to discuss the method by which the factor FQA shall be determined.

3.0 METHODOLOGY The computer model and reactor physics methodology that will be used to determine FQA shall be consistent with that in Reference 1, or another approved methodology. The approach will have two parts. First, a bounding percentage increase at a 95%/95% level of confidence in the maximum over z Iwill be determined. The bounding percentage increase will be determined using historical data at approximately 31 day intervals from at least 3 completed cycles. Second, for each upcoming cycle, the percentage increase in the maximum FQ nuclear prediction (FP (Z)) will be calculated over approximately 31 EFPD intervals from the Beginning of the Cycle (BOC) until the End of the Cycle (EOC). The greater of the two values, one based on historical data, and one based on the predicted change in the maximum Fp (Z) shall be used to set FQA. FQA shall be reported in the COLR. The FQA reported in the COLR may vary with cycle exposure. The maximum FQ (Z) values may be NAD-PI-004, Rev. 0 Page 5 of 7

taken from a predictive cycle depletion from BOC to EOC assuming nominal operating conditions.

4.0 BASES The basis for increasing the F~v (Z) by an additional factor, FQa, based on observed changes in I KF-(-*) between flux maps lies in the requirement that flux maps be taken only once every 31 EFPD. The concern is that if t7 shows an increasing trend between two successive flux maps, it may increase by such an amount during the next 31 EFPD that F W (Z) could exceed the FQ(Z) limit prior to the taking of the next map. Applying the factor FQA to Fw (Z) based on the maximum expected increase in Fp (Z) should ensure that the COLR limit on FQ(Z) will not be exceeded prior to the taking of the next map. Furthermore, establishing a minimum value for FQA based on historical changes in the maximum over z of KF(Z) adds conservatism to the calculation of FQA.

Using Fp (Z) prior to the application of any calculated V(Z) penalty to determine the factor FQA is consistent with the plant monitoring the trend in I K-(Z to determine whether to apply the factor FQA.

The V(Z) factor is applied to [L() I to account for variations from steady state operation.

The concern over increasing trends in [ K(Z) is in regard to the base nuclear FQ(Z) prior to application of the V(Z) factor. Use of 31 EFPD in the calculation of the factor FQA is consistent with the maximum period allowed between flux maps and will therefore provide for the maximum observed increase in FQ (Z) between flux maps.

NAD-PI-004, Rev. 0 Page 6 of 7

5.0

SUMMARY

A factor FQA will be calculated which is the amount by which F~w (Z) will be increased if the maximum over z of I K-- ) increases for any two consecutive measurements. FQA will be determined by considering both increases in the maximum over z of I K(Z) from previous cycles and also increases in FQ (Z), the maximum FQ nuclear prediction, over approximately 31 EFPD operating periods from BOC until EOC for the cycle of interest. FQA may vary with cycle exposure. FQA shall be included in the COLR.

6.0 REFERENCES

1) NSPNAD-8101-A (latest approved revision), Qualification of Reactor Physics Methods for Application to Prairie Island, October 2000 NAD-PI-004, Rev. 0 Page 7 of 7