ML20213G116

Forwards Response to IE Bulletin 86-003 Re Potential Failure of Multiple ECCS Pumps Due to Single Failure of air- Operated Valve in Min Flow Recirculation Line.Mechanical Block Installed on Each Valve Actuator & Procedures Revised

ML20213G116
Person / Time
Site:	Robinson
Issue date:	11/03/1986
From:	Cutter A CAROLINA POWER & LIGHT CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
IEB-86-003, IEB-86-3, IEIN-85-094, IEIN-85-94, NUDOCS 8611170332
Download: ML20213G116 (3)

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CP&L Carolina Power & Light Company SERIAL: NLS-86-404 Dr. J. Nelson Grace, Re ional Administfdtd$V i

• tl United States Nuclear egulatory Commission 101 Marietta Street, NW Atlanta, GA 30303 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261/ LICENSE NO. DPR-23 4 RESPONSE TO IE COMPLIANCE BULLET'N 86-03; POTENTIAL FAILURE OF MULTIPLE ECCS PUMPS DUE TO SINGLE FAILURE OF AIR-OPERATED ,

VALVE IN MINIMUM FLOW RECIRCULATION LINE -

Dear Dr. Grace:

Per the requirements of IE Compliance Bulletin 86-03, Carolina Power & Light Company (CP&L) hereby submits the results of our revmw of the H. B. Robinson Steam Electric Plant, Unit No. 2 (HL2R2) Emergency Core Cooling System (ECCS). The subject Bulletin required that it be determined whether a licensee's facility has a single-failure vulnerability in the minimum flow recirculation line of any ECCS pump which could result in the failure of more than one ECCS train. Should this problem exist, corrective actions are to be developed and implemented to bring the facility into compliance with CDC 35. A written report providing the results of the review, a justification for continued operation, and a description of the short-term corrective actions are to be submitted within 30 days of receiving the Bulletin. In addition, a report detailing the long-term corrective actions is to be submitted within 90 days of receipt of the Bulletin.

As stated in the Bulletin, CP&L submitted Licensee Event Report (LER)86-001 on February 5, 1986, which detailed a desi HBR2 Safety injection (SI) gn deficiency pumps. Attachedinvolving the minimum is a description flow recirculation of the HBR2 ECCS and thepath for the corrective actions taken to resolve this concern per.LER 86-001. This information is formatted such that the specific subheadings correspond to the Bulletin actions.

Please note that both the short-term and proposed long-term corrective actions have been adequately described in this submittal. CP&L therefore believes that the actions required by IE Compliance Bulletin 86-03 have been completed and that a second submittal providing our proposed long-term corrective actions ts not necessary. For this reason, CP&L considers the Bulletin actions for HBR2 to be complete.

Should you have any concerns with regard to this submittal, please contact Mr. R. W. Prunty at (919) 836-7318.

Yours,very truhy

. e (I . by ABC/AWS/bmc (5038AWS) A. B. Cutter - Vice President Attachment Nuclear Engineering & Licensing

'cc: Mr. G. Requa (NRC) W/A Mr. H. Krug (Nke Resident inspector - RNP) W/A US NRC Document Control Desk W/A A. B. Cutter, having been first duly sworn, did depose and say that the information contained hareir. is true and correct to the best of his information, knowledge and belief; and the sources of his information are of ficers, employees, contractors, and agents of Carolina Power- .&" "Light "***,

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O RESPONSE TO NRC IE COMPLIANCE BULLETIN 86-03 The following sections provide specific detail on each of the IE Compliance .

Bulletin 86-03 action items.

NRC Action 1:

Promptly determine whether or not your facility has a single-failure vulnerability in the minimum flow recirculation line of any ECCS pumps that could cause a failure of more than one ECCS train.

CP&L Response:

As a result of IE Information Notice No. 85-94 entitled " Potential For Loss of Minimum Flow Paths Leading to ECCS Pump Damage During a LOCA," a review of the HBR2 51 Syster i was conducted. A design deficiency was discovered in the SI pump minimum flow recirculation path on January 7,1986. The SI system design was such that a single failure of the instrument air or control circuitry for either of the isolation valves in the minimum flow recirculation path could lead to damage and loss of the three SI pumps. The failure could occur subsequent to actuation of the pumps with Reactor Coolant System (RCS) pressure remaining above pump shut off head (~ 1500 PSIG) for a short period. This would cause the pumps to operate deadheaded causing possible damage to the SI pumps. 1 The SI pumps have a common return pipe from their discharges to the Refueling Water Storage Tank (RWST). This is to provide a test flow path and a recirculation path for minimum flow when the RCS pressure exceeds pump shut off head. There are two isolation valves, SI-856A and SI-856B, in series in the return line. They are air-operated (normally open) and fail-closed when their control circuits lose electrical power or upon loss of air pressure. The purpose of these valves is to isolate the RWST (outside containment) from the containment sump during the recirculation phase of emergency core cooling following a postulated Loss of Coolant Accident.

NRC Action 2:

If the problem exists: (a) promptly instruct all operating shif ts of the problem and measures to recognize and mitigate the problem,(b) promptly develop and implement corrective actions which bring your facility into compliance with CDC 35.

CP&L Response:

l As an interim corrective action, a mechanical block was installed on each valve actuator so that upon loss of electrical power or air pressure, the valves will fail-as-is (open). The necessary plant procedures have been revised to reflect this change. These actions were completed by January 7,1986.

This interim corrective action ensures that the SI recirculation valves remain open, thereby providing a minimum flow path when the RCS pressure exceeds the pump shut off head. In addition, the valves are administratively controlled such that they will be placed in a closed position prior to the need for long-term j recirculation to keep the containment sump isolated from the RWST. CP&L

believes that these corrective actions resolve any operability concern with the SI pumps.

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NRC Action 3:

Within 30 days of receipt of this bulletin,(a) provide a written report to the NRC which identifies whether or not this problem exists at your facility,(b) if the

'p problem exists (or existed), include in the report the justification for continued

' operation and identify the short-term modifications to plant operating procedures or hardware that have been or are being implemented to ensure safe plant operations.

CP&L Response:

,lE Compliance Bulletin 86-03 was received by CP&L on October 13,1986, therefore, this information is being submitted within the time frame required.

CP&L believes that the interim corrective actions described in our response to NRC Action 2 above adequately resolve any operability concerns and will ensure safe plant operations.

NRC Action 4:

If the problem exists (or existed), provide a written repprt within 90 days of receipt of this Bulletin informing the NRC of the schedule for long-term resolution of this and/or any other significant problems that are identified as a result of this Bulletin.

CP&L Response:

Although the corrective actions described above are believed to be adequate for the long term operability of the SI system, efforts are currently underway to develop and implement a modification to change the two Si recirculation valves to a fail-as-is design. Implementation of this change is planned to occur during Refueling Outage 13, currently scheduled for 1990.

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