ML20214M336

Safety Evaluation Supporting Util Rept Entitled, Rod Swap Methodology Rept for Startup Physics Testing

ML20214M336
Person / Time
Site:	Mcguire, Catawba, McGuire, 05000000
Issue date:	05/22/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20214M313	List: ML20214M310 ML20214M336
References
TAC-62981, TAC-62982, NUDOCS 8706010275
Download: ML20214M336 (6)

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Enclosure SAFETY EVALUATION REPORT FOR DUKE POWER COMPANY'S

" ROD SWAP METHODOLOGY REPORT FOR STARTUP PHYSICS TESTING" Introduction ,

Duke Power Company (the licensee) submitted a report titled " Rod Swap Methodology Report for Startup Physics Testing" on December 4,1986. Answers to NRC i questions and additional information were submitted by letters dated February 11, 1987 (Ref. 2) and March' 11, 1987 (Ref. 3). The report describes the rod swap methodology which Duke Power Company would like to use for rod worth measurement for the McGuira 1 and 2 and the Catawba 1 and 2 units after each i' reload. While the rod swap technique has been used on Duke plants in the past, 1

the methodology was the Westinghouse methodology which NPC approved on

. May 28, 1983. Due to the complexities of Rod Swap, the May 28, 1983 approval stated that the method was approved for use by Westinghouse only. Thus, it is necessary for Duke to obtain NRC approval before using the Duke Rod Swap methodology.

Background

The reactivity worth of the control rods is measured at the beginning of each 4

cycle. Rod worth measurements are made in order to verify shutdown margin.

The measurement conditions are not those used in the accident analysis but comparison of measurement and predicted rod worths for a known set of conditions gives assurance that rod worths and the shutdown margin predicted for the worst conditions are accurate. For reload cores, usually, not all rod banks are measured. Normally, the control banks (approximately 4 banks,

, worth about half the total worth) are measured.

The traditional method of rod worth measurement is by boron dilution. Starting

, from an all rods out, critical configuration, the bank is-inserted a few steps at a time and the reactor is kept critical by diluting the boron concentration.

[j. One control bank would be inserted until it is all the way in and then the next bank would be started. A reactivity computer is also used to measure the b reactivity change at each position. The reactivity worth of the bank is the e

g no sum of all the reactivity changes recorded by the reactivity computer. The worth of the bank is also equal to the difference in boron concentrations from 08 the bank fully withdrawn to fully inserted positions.

So n:c Several years apolan alternative method of rod worth measurement called rod So swap or rod exchange was proposed. In this method the highest worth bank, oc called the reference bank, is measured by boron dilution and remaining banks, U - called test banks, are measured by " swapping" the test bank with the reference t

bo bank. The critical position of each measurement is'the reference bank position when the test bank is fully inserted. This method is an indirect method in that it does not measure the worth of banks in combination (i.e. banks D + C + B + A). Rod Swap does have some advantages over boron dilution, however. It does not require the large change in boron concentration and

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_2 subsequent processing of thousands of gallons of water. It is less time consuming and thus all banks can be measured in much less time than it would take to measure one half the banks by boron dilution.

Evaluation The Duke Report presents a minimal description of the methodology and a comparison of calculated and inferred worths for several cycles on McGuire 1 and 2. Additional infonnation supplied more details of the procedure. The Duke methodology is very similar to the methodology NRC approved for use by Westinghouse. Duke will use previously approved physics codes and ,

methodologies as described in Reference 4 for the calculations of rod worths and critical heights.

As verification of the methodology, Duke supplied rod swap data for 5 cycles (McGuire Unit 1, Cycles 2, 3 and and 4. McGuire Unit 2, Cycles 2 and 3). This data compares measured and predicted worth for each bank. In addition we have made comparisons of this data with that presented in the Startup Reports for these cycles. (This data is different since Westinghouse did the calculations for thesecycles). Examination of the data reveals that the greatest deviation on any one bank was 103 pcm or 24% on a small bank. The greatest deviation on the total worth was 6.9% for Unit 2, Cycle 2. The average total difference was 4.94% which compares favorably with the 6.38% for the Westinghouse predictions.

While for some of the McGuire data the difference between measurement and prediction is greater than usually seen, it is still within the acceptable range. Duke did not perfonn a side-by-side comparison of boron dilution and rod swap for the same cycle. However, Duke supplied data from the initial startup of Catawba 1 and 2, Catawba 1 using boron dilution and Catawba 2 using Rod Swap. The cores are essentially identical as confinned by as built parameters and other physics test measurements. The rod worth measurements were within acceptable limits.

Based on our review of the material submitted, we find the rod swap methodology l as proposed by Duke Power Company to be acceptable subject to the following l conditions, to which Duke Power Company has agreed:

1) The boron dilution rate for measurement of the reference bank shall not exceed 500 pcm.

2) All banks, both control and shutdown banks, must be measured.

3) The review criteria are:

A. The absolute value of the percent difference between measured and predicted integral worth for the reference bank is < 10 ~

percent.

B. For all banks other than the reference bank, either (whichever is greater);

1) the absolute value of the percent difference between inferred and predicted integral worths is 515 percent or

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2) the absolute value of the reactivity difference between 1 inferred and predicted integral worths is f 100 pcm.*

C. The sum of the measured / inferred worth of all the rods must be

< 110 percent of the predicted worth.

4) The acceptance criteria are:

(1) The sum of the measured / inferred worth of all the rods must be

> 90 percent of the predicted rod worth.

(2) For all banks other than the reference bank, either (whichever is a) greater) the absolute value of the percent difference between inferred and predicted integral worth is < 30 percent or b) the absolute value of the reactivity difference between inferred and predicted integral worths is < 200 pcm.

(3) The absolute value of the percent difference between measured and predicted integral worth for the reference bank is < 15 percent.

5) Additional testing is required if the reference bank boron concentrations and reactivity computer worth do not agree. Remedial action for failure of an acceptance or review criterior require investigation and solution within 30 days (for acceptance criterion) or 60 days (for review criterion). The licensee must then submit a report of the find %gs to the NRC within 4E days of the test (for acceptance criterion) or within 75 days of the test (for review criterion).

• A pcm is equal to 10-5 o k/k.

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REFERENCES

1) letter, H. B. Tucker, Duke Power Company, to Harold R. Denton, NRC, December 4, 1986. .

2) Letter, H. B. Tucker, Duke Power Company, to Nuclear Regulatory Commission, Document Control Desk, dated February 11, 1987.

3) Letter, H. B. Tucker, Duke Power Company, to Nuclear Regulatory Commission, Document Control Desk, dated March 11, 1987.

d) Duke Power Company, " Nuclear Physics Methodology for Reload Design,"

DPC-NF-2010A, June 1985.

o Mr. H. B. Tucker Duke Power Company Catawba Nuclear Station cc:

A.V. Carr, Esq. North Carolina Electric Membership Duke Power Company Corp.

422 South Church Street 3400 Sumner Boulevard Charlotte, North Carolina 28242 P.O. Box 27306 Raleigh, North Carolina 27611

'J. Michael McGarry, III, Esq.

Bishop, Libeman, Cook, Purcell Saluda River Electric Cooperative, and Reynolds Inc.

1200 Seventeenth Street, N.W. P.O. Box 929 Washington, D. C. 20036 Laurens, South Carolina 29360 North Carolina MPA-1 Senior Resident Inspector Suite 600 Route 2, Box 179N 3100 Smoketree Ct. York, South Carolina 29745 P.O. Box 29513 Raleigh, North Carolina 27626-0513 Regional Administrator, Region II U.S. Nuclear Regulatory Coninission, L.L. Williams 101 Marietta Street, NW, Suite 2900 Area Manager, Mid-South Area Atlanta, Georgia 30323 ESSD Projects Westinghouse Electric Corp.

MNC West Tower - Bay 239 P.O. Box 355 Pittsburgh, Pennsylvania 15230 Mr. Heyward G. Shealy, Chief Bureau of Radiological Health South Carolina Department of Health and Environmental Control 2600 Bull Street Columbia, South Carolina 29201 County Manager of York County York County Courthouse Karen E. Long York South Carolina 29745 Assistant Attorney General N.C. Department of Justice Richard P. Wilson, Esq. P.O. Box 629 Assistant Attorney General Raleigh, North Carolina 27602 S.C. Attorney General's Office P.O. Box 11549 Spence Perry, Esquire Columbia, South Carolina 29211 General Counsel Federal Emergency Management Agency Piedmont Municipal Power Agency Room 840 100 Memorial Drive 500 C Street Greer, South Carolina 29651 Washington, D. C. 20472 Mr. Michael Hirsch Federal Emergency Management Agency Office of the General Counsel Room 840 500 C Street, S.W.

Washington, D. C. 20472 Brian P. Cassidy, Regional Counsel Federal Emergency fianagement Agency, Region I J. W. McComach P0CH Boston, Massachusetts 02109

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• O Mr. H B. Tucker Duke Power Company McGuire Nuclear Station cc:

Mr. A.V. Carr, Esq. Dr. John M. Barry Duke Power Company Department of Environmental Health

.P. O. Box 33189 Mecklenburg County 422 South Church Street 1200 Blythe Boulevard Charlotte, North Carolina 28242 Charlotte, North Carolina 28203 County Manager of Mecklenburg County 720 East Fourth Street Charlotte, North Carolina 28202 Chairman, North Carolina Utilities Commission Mr. Pobert Gill Dobbs Building Duke Power Company 430 North Salisbury Street Nuclear Production Department Raleigh, North Carolina 27602 P. O. Box 33189 Charlotte, North Carolina 28242 Mr. Dayne H. Brown, Chief Radiation Protection Branch J. Michael McGarry, III, Esq. Division of Facility Services Bishop, Liberman, Cook, Purcell Department of Human Resources and Reynolds 701 Barbour Drive 1200 Seventeenth Street, N.W. Raleigh, North Carolina 27603-2008 Washington, D. C. 20036 Senior Resident Inspector c/o U.S. Nuclear Regulatory Comission Route 4, Box 529 Hunterville, horth Carolina 28078 Regional Administrator, Region II U.S. Nuclear Regulatory Commission, 101 Marietta Street, N.W., Suite 2900 Atlanta, Georgia 30323 L. L. Williams Area Manager, Mid-South Area ESSD Projects Westinghouse Electric Corporation MNC West Tower - Bay 239 P. O. Box 355 Pittsburgh, Pennsylvania 15230 l

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