BSEP-96-0121, Responds to NRC Bulletin 95-002, Unexpected Clogging of RHR Pump Strainer While Operating in Suppression Pool Cooling Mode

Responds to NRC Bulletin 95-002, Unexpected Clogging of RHR Pump Strainer While Operating in Suppression Pool Cooling Mode

ML20101R150
Person / Time
Site:	Brunswick
Issue date:	04/04/1996
From:	Hicks G CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BSEP-96-0121, BSEP-96-121, IEB-95-002, IEB-95-2, NUDOCS 9604160072
Download: ML20101R150 (5)

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• CP&L Carolina Power & Light Company PO Box 10429

Southport NC 28461-0429 APR 041996 SERIAL

BSEP 96-0121 United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS.1 AND 2 DOCKET NOS. 50-325 & 50-324/ LICENSE NOS. DPR-71 & DPR-62 NRC BULLETIN 95-02, UNEXPECTED CLOGGING OF RESIDUAL HEAT REMOVAL (RHR)

! PUMP STRAINER WHILE OPERATING IN SUPPRESSION POOL COOLING MODE" l

t Gentlemen:

l The purpose of this letter is to provide additionalinformation regarding Carolina Power &

l Light Company's February 13,1996 (Serial No. BSEP 95-0668) response to NRC Bulletin 95-02. Enclosure 1 provides the information discussed during a March 7,1996 conference call with members of the NRC staff, and Enclosure 2 provides a list of commitments.

l l Please refer any questions regarding this letter to Mr. George Honma at (910) 457-2741. I Sincerely l

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G. D. Hicks Manager - Regulatory Affairs Brunswick Nuclear Plant GMT/

Enclosures:

1. Response

2. List of Regulatory Commitments

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cc: Mr. S. D. Ebneter, NRC Regional Administrator, Region 11 Mr. C. A. Patterson, NRC Senior Resident inspector - Brunswick Plant Mr. D. C. Trimble, Jr., NRR Project Manager - Brunswick Plant The Honorable H. Wells, Chairman - North Carolina Utilities Commission f W I 9604160072 960404 l PDR ADOCK 05000324 G PDR o

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i ENCLOSURE 1 1

BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 NRC DOCKET NOS. 50-325 & 50-324 OPERATING LICENSE NOS. DPR-71 & DPR-62 NRC BULLETIN 95-02, UNEXPECTED CLOGGING OF RESIDUAL HEAT REMOVAL (RHR)

PUMP STRAINER WHILE OPERATING IN SUPPRESSION POOL COOLING MODE By letter dated February 13,1996 (Serial No. BSEP 95-0668), Carolina Power & Light company provided the results of our confirmatory testing and inspections per NRC Bulletin 95-02. A conference call was held with members of the NRC staff on March 7,1996, to discuss details related to the response. The four questions provided by the NRC were discussed and are recapped as follows. ,

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NRC Question 1 Why was 6 hr test run only briefly with two pumps and continued for most of the l test with only one?

CP&L Response The intent of the test was to agitate any existing debris / fibrous material, and then i collect this on a single RHR suction strainer. This was considered the best method l for collecting torus debris. It should be noted that limited debris / fibrous material was considered available, as the torus had been drained and cleaned during the each unit's last refueling outage. Since the B RHR ioops are equipped with the torus drain path, it is Operations' preferred loop and has the most run time. Most neutral buoyancy debris would have been expected to have already collected on or around this loop's strainer due to the large flow capacity combined with its run time. Debris collected prior to or during the test would act as a filter medium for the agitated sludge.

RHR loop B was started first with one pump running at 8000 gpm. Then RHR loop A was started with two pumps running at 15,000 gpm, in order to agitate torus sludge. After running both RHR loops for 10 minutes, the A RHR pumps were secured leaving a single B loop RHR pump running for at least 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. A singia RHR pump running for 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> passes the equivalent of 4.5 torus water volumes through the RHR B loop strainer. There was no additional value provided by running a second B loop RHR pump considering the length of the run, the turbulence one pump provides, and that both pumps on the B loop use a common suction strainer.

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- 1 NEC Question 2

, February 13,1996 response to Bulletin 95-02 states that there was a decrease in

! suction pressure while perfomaing the Unit 2 tests, but that only " trace amounts" l of material were found on the RHR 2A suction strainer. Explain the apparent contradiction.

l l CP&L Resoonse While a specific reason for the slight decrease (0.57 psig) in suction pressure was not identified, the change was well within the calculated maximum allowable 2.41 psig pressure drop limit that had been established for the test. Divers performing the B loop RHR strainer inspection noted approximately 75 paint chips (approximately 1/8" X 1/8") on the top half of the strainer. The area covered was l less than 1 % of the strainer surface. With only half of the Unit 2 torus repainted i during the 1994 refueling outage, some paint chips were expected to be generated

! in lirohd amounts, and this could have contributed to a small pressure drop across l the strainer. T. ., *! nit 2 torus strainers were cleaned (hydrolased), the torus i

destudged, and i ; remaining half of the torus immersion zone repainted during the )

1996 refueling outage (B212R1). J

, NRC Question 3 l l l

Discussions in November 15,1995 and February 13,1996 responses to Bulletin 95-02 focus on debris on suction strainers. Were other debris found in the pool?

CP&L Response 1

l Limited amounts of the same materials as found on the strainers (small paint chips j and small fragmer,m of duct tape) were found, along with ~ 1/16" of corrosion l product sludge or, the pool bottom. it is concluded that the paint chips ca'oe from l the half of the liner that had not been recoated during the 1994 refueling outage.

The two torus water samples, taken midway between the bottom of the torus and the top of the water, found no evidence of visible or microscopic fibers. Analysis

[ of the two sludge samples found limited fibrous material. The samples contained j two or three polyester fibers approximately twelve by forty micrometers, which

! would ea@e pass through the strainers, and a single polyester fiber one centimeter I

long w'3. ,arying diameters of about thirty five to sixty micrometers.

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! NRC Qu6stion 4 l

Although not requestedin Bulletin 95-02, the staff would appreciate a discussion of long term plans, if they have been formulated yet?

_QP38. Response Long term plans have not yet been formulated. Development is waiting on the

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completion of the final reports associated with the Unit 2 torus inspections, and the data from the Fall 1996 Unit 1 refueling outage. Unit 1 will have completed a full cycle with the torus liner recoated, and the data collected will provide a baseline for any inspection / cleaning program that may be developed.

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ENCLOSURE 2

' BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS.1 AND 2 i DOCKET NOS. 50-325 AND 50-324/ LICENSE NOS. DPR-71 AND DPR-62 NRC BULLETIN 95-02, UNEXPECTED CLOGGING OF RESIDUAL HEAT REMOVAL (RHR)

PUMP STRAINER WHILE OPERATING IN SUPPRESSION POOL COOLING MODE l

LIST OF REGULATORY COMMITMENTS The following table identifies those actions committed to by Carolina Power & Light Company in this document. Any other actions discussed in the submittal represent intended or planned actions by Carolina Power & Light Company. They are described to the NRC for the NRC's information and are not regulatory commitments. Please notify the Manager-Regulatory Affairs at the Brunswick Nuclear Plant of any questions regarding this document or any associated regulatory commitments.

Committed Commitment date or i

outage i

NONE N/A i l

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