ML20214T874
| ML20214T874 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 11/13/1986 |
| From: | Daltroff S PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-86-003, IEB-86-3, NUDOCS 8612090040 | |
| Download: ML20214T874 (4) | |
Text
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i PHILADELPHIA ELECTRIC COMPANY 230s MARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.191o1 SHIELDS L DALTROFF November 13, 1986 ELEC?plC PRODUCTION Docket No. 50-352 1
Dr. Thomas E. Murley, Administrator
' Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406
SUBJECT:
Response to IE Bulletin 86-03 Potential Failure of Multiple ECCS Pumps i
Due to Single Failure of Air-Operated Valve In Minimum Flow Recirculation Line - Dated October 8, 1986 Limerick Generating Station Unit 1
Dear Dr. Murley:
r The purpose of this letter is to provide the Philadelphia Electric Company (PECo) response to IE Bulletin 86-03 for Limerick Generating Station Unit 1.
The bulletin discussed a situation at another nuclear power plant in which a single failure could result in the loss of minimum flow bypass for all Emergency Core Cooling System (ECCS) pumps in a system.
As indicated in the bulletin, this condition could result in no flow through the ECCS and could lead to the pumps running dead headed with potential for pump damage in a few minutes.
Since i
the finding for the first action required for the bulletin determined that Limerick Unit 1 is not vulnerable to these failures, items 2, 3 and 4 require no response.
The actions required by the bulletin are restated below followed by PECo's response:
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.
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Dr. Thomas E. Murley November 13, 1986 Page 2 2.
If the problem exists, (a) promptly instruct all operating shifts 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 GDC 35.
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 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.
4.
If the problem exists (or existed), provide a written report within 90 days of receipt of this bulletin informing the NRC of the schedule for long-term resolution of this problem.
Response
PECo has reviewed the ECCS and RCIC minimum flow recirculation design for Limerick Generating Station Unit 1 and has determined that a single failure vulnerability in the minimum flow recirculation line of any ECCS or RCIC pump that could cause a failure of more than one ECCS train does not exist at Limerick Generating Station Unit 1.
All of the minimum flow recirculation line shut-off valves for the RHR, Core Spray, HPCI and RCIC pumps are motor operated valves.
The HPCI, RCIC, each of the four trains (loops) of RHR, and each of the two trains (loops) of Core Spray have their own dedicated minimum flow return line to the suppression pool with a motor operated shut-off valve in each return line, and a flow sensing instrument loop installed in the discharge line of that train to control the position of the minimum flow recirculation line shut-off valve.
Each train of RHR contains one 100% loop flow capacity pump and each train of Core Spray contains two 50%
loop flow capacity pumps.
Each train of RHR is assigned to a different electrical safeguard division and as such each train is redundant to, independent of, and separated from the other trains of RHR.
Likewise, each train of Core Spray is assigned to two different electrical safeguard divisions, and as such each train is redundant to, independent of, and separated from each other.
The HPCI and RCIC systems are dependent on the plant DC power supplies only.
The pump, minimum flow recirculation line shut-off valve, and the discharge line flow sensor, for HPCI, RCIC and each train of
Dr. Thomas E. Murley November 13, 1986 4
Page 3 RHR and Core Spray and the electrical safeguard divisions which they are assigned to are provided in Table 1.
There is no single failure identified which will result in the failure of an ECCS or RCIC minimum flow recirculation line that will result in the loss of more than one train of ECCS.
However, a single failure that would disable more than one ECCS or RCIC system minimum flow recirculation line would be the loss of one of the AC electrical safeguard division motor control centers.
This single failure would disable one RHR and one Core Spray minimum flow recirculation line shut-off. valve.
If the disable valves were closed at the time of the single failure, the associated trains of RHR and Core Spray could be lost.
The i
HPCI, RCIC, each of the three remaining trains of RHR and the remaining train of Core Spray would not be affected.
The loss of one of the AC electrical safeguard division motor control centers is enveloped by the loss of one diesel generator along with its associated safeguard bus, i.e.,
the loss of one AC electrical safeguard division.
This event 4
has previously been analyzed as a part of the plant's design i
basis in FSAR Section 8.3.1.
A single failure vulnerability in the minimum flow recirculation line of any ECCS or RCIC pump that could cause a failure of more than one ECCS train as discussed in IE 4
Compliance Bulletin 86-03 does not exist at Limerick Generating Station Unit 1.
There is no identified single failure of one ECCS or RCIC minimum flow recirculation line that will disable more than one train of ECCS or RCIC.
No modifications to plant operating procedures or hardware are required.
l l
l Should you have any questions, or require additional information, please do not hesitate to contact us.
Very truly
- ours, A
cc:
E. M. Kelly, LGS NRC Site Inspector i
i
TABLE 1 AC ELECTRICAL SAFEGUARD DIVISION ASSIGNMENTS ECCS MIN. FLOW DISCH. LINE SAFEGUARD TRAIN PUMP RECIRC. VALVE FLOW SENSOR DIVISION A RHR 1AP202 HV-51-lF007A FT-51-lNOS2A Division I B RHR 1BP202 HV-51-lF007B FT-51-lN052B Division II C RHR 1CP202 HV-51-lF007C FT-51-lN052C Division III D RHR 1DP202 HV-51-lF007D FT-51-lN052D Division IV A Core Spray 1AP206 HV-52-lF031A FT-52-lN051A Division I 1CP206 Division III B Core Spray 1BP206 HV-52-lF031B FT-52-lN051B Division II 1DP206 Division IV DC ELECTRICAL SAFEGUARD DIVISION ASSIGNMENTS 1
ECCS/RCIC MIN. FLOW DISCH. LINE SAFEGUARD TRAIN PUMP RECIRC. VALVE FLOW SENSOR DIVISION HPCI 10P204 HV-55-lF012 FT-55-lN051 Division II i
RCIC LOP 203 HV-49-lF019 FT-49-lN051 Division I t
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