NRC Generic Letter 1988-03
| ML031200470 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley, Millstone, Calvert Cliffs, Davis Besse, Salem, Oconee, Mcguire, Palisades, Palo Verde, Indian Point, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Watts Bar, Sequoyah, Byron, Arkansas Nuclear, Three Mile Island, Braidwood, Summer, Prairie Island, Seabrook, Surry, North Anna, Turkey Point, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Farley, Robinson, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, McGuire, 05000000, Washington Public Power Supply System, Trojan, Marble Hill |
| Issue date: | 02/17/1988 |
| From: | Miraglia F Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| GSI-093 GL-88-003, NUDOCS 8802180267 | |
| Download: ML031200470 (10) | |
I ..4 UNITED STATES NUCLEAR REGULATORY
COMMISSION
e WASHINGTON, D. C. 2055 TO ALL LICENSEES, APPLICANTS
FOR OPERATING
LICENSES, AND HOLDERS OF CONSTRUCTION
PERMITS FOR PRESSURIZED
WATER REACTORS Gentlemen:
SUBJECT: RESOLUTION
OF GENERIC SAFETY ISSUE 93, "STEAM BINDING OF AUXILIARY
PUMPS" (GENERIC LETTER 88-03)This generic letter is being issued: (1) to inform you of the staff's resolution of the subject generic safety issue, and (2) to request that you continue to implement, as a minimum, the monitoring and corrective procedures previously identified for interim resolution of this issue in IE Bulletin 85-01, "Steam Binding of Auxiliary Feedwater Pumps,' dated October 29, 1985.(A copy of this bulletin is attached.)
The issue concerns the potential disabling of auxiliary feedwater (AFW) pumps by steam binding that is caused by backleakage of main feedwater (MFW) past the isolation check valves between the AFW and MFW systems. The issue is significant because most AFW systems are potentially vulnerable to common mode failure of the redundant AFW pumps as a result of steam binding. This vulnerability is inherent to the piping configurations used, which allow redundant trains of AFW to be cross-connected via common headers on the suction and discharge sides of the pumps.To reduce the probability of AFW pump failure as a consequence of steam binding if backleakage does occur, IE Bulletin 85-01 requested that certain licensees and construction permit holders implement procedures both for monitoring the AFW piping temperatures for indication of possible backleakage and for restoring the pumps to operable status if steam binding were to occur. The bulletin was not issued to all holders of operating licenses and construction permits for pressurized water reactors because the staff had determined that a number of them had already taken actions that would minimize the occurrence of the AFW pump steam binding problem at their plants. The bulletin recommended a monitoring frequency of once a shift, compared with the previously recommended frequency of once a month. This increased frequency reduced the likelihood of pump unavailability because of steam binding by a factor of 90 (3 shifts/day x 30 days/month).
Cla FEB 1 7 8 Multiple
Addressees
-2-As part of its efforts toward a final generic resolution of this issue, the staff surveyed the backleakage experience in operating plants following the implementation of monitoring procedures.
Although the number of backleakage events varied from an average of less than one per reactor year at i large majority of plants to more than 100 per reactor year at others, none of the backleakage events that occurred during the review period appeared to have resulted in the steam binding of an AFW pump. This indicates that the various monitorina methods employed can be highly effective in preventing steam binding if backleakage occurs. For the plants with a high backleakage event rate, the installation of continuous monitoring systems with control room alarms was instrumental in providing for early warning to the operator and timely corrective action.The results of the staff's regulatory analysis indicated that following the recommendations in Bulletin 85-01 would ensure that the contribution of AFN pump steam binding to core melt frequency and public risk was sufficiently low and that there is no need for new recommendations beyond those in XE Bulletin 85-01.The staff has concluded that the recommended monitoring actions of IE Bulletin 85-01 should be continued.
However, although the staff has concluded that the currently assessed risk associated with this issue is reasonably low, it is still concerned about the generally unsatisfactory reliability of checik valves in operating plants. Plant operators should continue to be alert to the possible development of malfunctioning check valves, especially as the plant ages. They should be prepared to increase the monitoring frequency as needed and to implement appropriate recovery procedures to ensure that steam binding failure of the AFN pumps does not occur.IE Bulletin 85-01 recommended that procedural controls remain in effect (1)until the completion of hardware modifications to substantially reduce the likelihood of steam binding, or (2) until it was superseded by action Implemented as a result of resolution of Generic Issue 93. This generic letter resolves Generic Issue 93 by perpetuating the recommendations of IE Bulletin 85-01. In particular, all addressees should: 1. Maintain procedures to monitor fluid conditions within the AFW system each shift during times when the system is required to be operable.This monitoring should ensure that fluid temperature at the AFN pump discharge is maintained at about ambient levels.2. Maintain procedures for recognizing steam binding and for restoring the AFW system to operable status, should steam binding occur.All addressees are requested to provide a letter of confirmation to the NRC within 90 days of receipt of this generic letter indicating that the procedures discussed in this generic letter are in place and will be maintained.
Confir-mation by addressees who did not previously receive IE Bulletin 85-01 is being requested because the staff believes that they would rely on these procedures as part of the actions to minimize the occurrence of the AFW pump steam binding problem.
Multiple
Addressees
-3- FEB 17 WC3 Pursuant to 10 CFR 50.54(f), you are requested to submit under oath or affirma-tion the letter of confirmation to the U.S. Nuclear Regulatory Commission, Document Control Desk, Washington, D.C. 20555, for reproduction and distribution.
This request for information is covered by the Office of Management and Budget under blanket clearance number 3150-0011, which expires December 31, 1989. Comment on burden and duplication should be directed to the Office of Management and Budget, Reports Management, Room 3208, New Executive Office Building, Washington, D.C. 20503.Although no specific request or requirement is intended, the following informa-tion would be helpful to the NRC in evaluating the cost of this generic letter: 1. Staff time to perform the requested confirmation and any needed followup actions.2. Staff time to prepare requested documentation.
If there are any questions regarding this matter, please contact the Regional Administrator of the appropriate NRC regional office or your project manager in this office.Sincerely, Frank J. ra Associate Director for Projects Office of Nuclear Reactor Regulation Enclosure:
IEB 85-01 a- Attachment.
OMB No.: 3150-0011 Expiration Date: 9/30/86 1EB 85-01 UNITED STATES NUCLEAR REGULATORY
COMMISSION
OFFICE OF INSPECTION
AND ENFORCEMENT
WASHINGTON, D.C. 20555 October 29, 1985 IE BULLETIN 85-01: STEAM BINDING OF AUXILIARY
PUMPS
Addressees
For Action -Those nuclear power reactor facility licensees and construction permit MCP) holders listed in Attachment
1.For Information
-All other nuclear power reactor facilities.
Purpose
- The purpose of this bulletin is to inform licensees and CP holders of a poten-tially serious safety problem that has occurred at certain operating facilities involving the inoperability of auxiliary feedwater (AFW) pumps as a result of steam binding. Certain PWR licensees and all PWR CP holders are requested to take further action to prevent similar events from occurring at their facili-ties and to document those actions taken or planned.
Description of Circumstances
Numerous events have been reported where hot water has leaked into AFW systems and flashed to steam, disabling the AFW pumps. Events at Robinson 2 in 1981 through 1983, Crystal River 3 in 1982 and 1983, and D. C. Cook 2 in 1981 were summarized in IE Information Notice (IN) 84-06, issued in January 1984. Also in January 1984, the Institute of Nuclear Power Operations (INPO) issued Significant Event Report (SER) 5-84 detailing'events at Robinson 2 and Farley.In April 1984, INPO issued Significant Operating Experience Report (SOER) 84-3 that discussed another event at Surry 2 In 1983.The NRC's Office for Analysis and Evaluation of Operational Data (AEOD) issued a case study report entitled "Steam Binding of Auxiliary Feedwater Pumps" in July 1984. This study identified
22 events since 1981; 13 of these occurring in 1983. Based on operating experience, it appears that backleakage into AFW could occur in any PWR. In a number of plants, the two motor-driven pumps feed into a single pipe which feeds into the steam generator;
therefore, a leaking valve in that pipe increases the probability of steam binding in both trains of AFW. Also, multiple AFW pumps often take suction from a common manifold;therefore, if one pump becomes steam bound because of leaking check valves, the steam can heat the common suction and cause other pumps to become steam bound.~~ l g .
I..tachmerot IEB 85-01 October 29, 1985 AFW capability is needed for normal shutdown and transient conditions as well as for accident mitigation.
The AEOD case study examined the effects.of steam binding on a sequence in which there was a loss of the power conversion (steam generation)
system after a transient other than loss-of-offsite power. A probabilistic risk analysis had previously shown this sequence to be a dominant contributor to the core-melt risk for a sample plant (Sequoyah).
The case study indicated that unavailability of the AFW system as a result of steam binding contributes significantly to the risk of core melt in PWRs. Monitoring AFW to detect backlealkage and to promptly correct the situation if backleakage occurs would reduce the probability of steam binding.Since the AEOD study was issued, a series of events involving backflow of hot water into the AFW system occurred at McGuire 2 over a period of 7 days in August 1984, before effective corrective action was taken. One of these events involved overpressurization of the suction line and damage to instruments.
In November 1984, Catawba 1 experienced backflow of hot water into AFW resulting in fumes from Insulation and blistering of paint. In December 1984, the NRC's Office of Nuclear Reactor Regulation (NRR) determined that steam binding of AFW was a generic issue and assigned it a high priority (Generic Issue 93, Steam Binding of Auxiliary Feedwater Pumps").To determine the extent of the safety issue and the need for short-term correc-tive actions, the NRC's regional offices conducted a survey in April and May of 1985. Of the 58 operating reactors surveyed, 39 had temperature monitoring of AFW piping at least once per shift. Of the remaining
19, 17 had normally closed gate or globe valves in the pump discharge path in addition to check valves, or some unique feature such as complete separation of trains that made serious safety problems unlikely.
The remaining
2 licensees have subsequently decided to monitor AFW piping temperature.
Although some degree of action has been taken at all units, many have not incorporated these actions into procedures to detect or correct steam binding.Without these provisions, there is little assurance that effective actions will continue.
For this reason, the addressees are requested to take the following actions: Action for
Addressees
Listed in Attachment
1 1. Develop procedures for monitoring fluid conditions within the AFW system on a regular basis during times when the system is required to be operable.
This monitoring should ensure that fluid temperature at the AFR pump discharge is maintained at about ambient temperature.
Monitoring of fluid conditions, if used as the primary basis for precluding steam binding, is recommended each shift.This item is not intended to require elaborate instrumentation.
A simple means of monitoring temperature, such as touching the pipe, is a satisfac-tory approach.
a 2. Develop procedures for recognizing steam binding and for restoring the AFW system to operable status, should steam binding occur.
.ttachment IEB 85-01 October 29. 1985 3. Procedural controls should remain in effect until completion of hardware modification to substantially reduce the likelihood of steam binding or until superseded by action implemented as a result of resolution of Generic Issue 93.Schedule:
For operating plants, develop and implement procedures within 90-days of the date of this bulletin.
For plants under construction, develop and implement procedures within 90 days after receiving an operating license or provide an appropriate response and commitment within 1 year of the date of this bulletin, whichever comes first.Re orting Requirements:
Prepare and submit a report describing the methods used to accomplish these actions. Include the date(s) that procedures and training were implemented or scheduled to be implemented.
State the frequency of monitoring of the temperature.
For operating plants, submit this report within 120 days of the date of this bulletin.
For plants under construction, submit the report within 120 days after receiving an operating license or within 1 year of the date of this bulletin, whichever comes first. It is not netessary to submit the procedures for review.The written report, requested above, shall be submitted to the appropriate Regional Administrator under oath or affirmation under provisions of Section 182a, Atomic Energy Act of 1954, as amended. In addition, the original copy of the cover letter and a copy of the attached report should be transmitted to the U. S. Nuclear Regulatory Commiss0on, Document Control Desk, Washington, DC 20555 for reproduction and distribution.
This request for information was approved by the Office of Management and Budget under blanket clearance number 3150-0011.
Comment on burden and dupli-cation should be directed to the Office of Management and Budget, Reports Management, Room 3208, New Executive Office Bullding, Washington, DC 20503.Although no specific request or requirement is intended, the following informa-tion would be helpful to the NRC in evaluating the cost of this bulletin: 1. staff time to perform requested review and testing 2. staff time to prepare requested documentation I Attachment IEB 85-01 October 29, 1985 If there are any questions regarding this matter, please contact the Regional Administrator of the appropriate NRC regional office or this office.es 14. Taylor, S'rector ice of Inspection and Enforcement Technical Contacts: Mary S. Wegner% IE (301) 492-4511 C. Vernon Hodge, IE (301) 492-7275 Attachments:
- 1.
Addressees
for Action'2. List of Recently Issued 1E Bulletins I a- Attachment
1 IEB 85-01 October 29. 1985
ADDRESSEES
FOR ACTION: The following PWRs having an OL: BYRON 1 CRYSTAL RIVER 3 DAVIS-BESSE
DIABLO CANYON 1 GINNA INDIAN POINT 3 KEWAUNEE MAINE YANKEE MILLSTONE
2 NORTH ANNA 1 NORTH ANNA 2 PALISADES POINT BEACH 1 POINT BEACH 2 PRAIRIE ISLAND 1 PRAIRIE ISLAND 2 RANCHO SECO SAN ONOFRE 1 ST. LUCIE 1 ST. LUCIE 2 SUMMER TMI I TROJAN TURKEY POINT 3 TURKEY POINT 4 WATERFORD
3 WOLF CREEK 1 YANKEE-ROWE
All PWRs holding a CP t a Attachment
2 IEB 85-01 October 29, 1985 LIST OF RECENTLY ISSUED IE BULLETINS hued to*Bulletin Date of No. Subject Issue Isl 84-03 Refueling Cavity Water Seal 8/24/84 All 0 fan an Cov sued to,_ oe eco 84-02 84-01 Failures Of General Electric Type HFA Relays In Use In Class 1E Safety System Cracks In Boiling Water Reactor Mark I Containment Vent Headers 3/12/84 2/3/84 vl Al fa an Al Wi am if a'V.ii 1 power
- eactor:1ilities holding OL or CP except rt St. Vrain 1 power reactor cilities holding OL or CP 1 BWR facilities ith Mark I contain-ent and currently i cold shutdown ith an OL for Action ad All other BWRs Ith an OL or CP for nformation
83-08 83-07 Sup. 2 83-07 Sup. 1 83-07 Electrical Circuit Breakers With An Undervoltage Trip Feature In Use In Safety-Related Applications Other Than The Reactor Trip System Apparently Fraudulent Products Sold By Ray Miller, Inc.Apparently Fraudulent Products Sold By Ray Miller, Inc.Apparently Fraudulent Products Sold by Ray Miller, Inc.12/28/83 12/09/83 10/26/83 7/22/83 All power reactor facilities holding an OL or CP Same as IEB 83-07 Same as IEB 83-07 All power reactor facilities holding an 0L or CP; Other fuel cycle facilities and Category B, Priority I (processors and distributors)
material licensees A*DL = Operating License CP
- Construction Permit
1 5ST OF , ENTLY ISSUED ENEFIC LETT Date of Sub ect. I sSuance S b em 1r i c'Letter No.I ssuIE~d To GL 8R-02 GL 69-01 GL 87-1 6"INTEGRATED
SEFETY ASSESSMENT
PROGRiAM II (ISAP-8F II)""NRC POSITION1l O;J IGSCC IN BWlR (-t Ic~i.r II( STAINLESS
STEEL.P P1NbF," NlJREG--1262. "ANSWERS TO QUESTIONS
AT PUBLIC MEETINGS RE IMPLEMENTATION
OF 1o CFR55 ON OFERAT ORS LICENSES t- 1. /20tO/a9 A1 /25/88 11 / 12/87 ALL POWER REACTOR LICENSEES ALL LICENSEES OF OPERATING BOILING WATER REACl ORS ANI, HOLDERS OF CONSTRUCT
I ON PERMITS FOR 14FRS ALL. POWER AND NONP OWER REACTOR LICENSEES
AND APPLICANTS
FOR LICENSES GL 87-15 POLICY STATEMENT
ON DEFERRED PLANTS 11/04/87 ALL HOLDERS OF CONSTRUCT
I ON PERMITS FOR A NUCLEAR POWER PLANT GL 87-14 UL 87-13 REQUEST FOR OPERATOR LICENSE SCHEDUiJLES
INTEGRITY
OF REQUALIFICATION
EXAMINATIONS
AT NON-POWER REACTORS 08 / 04 / 87 07/ 10/87 ALL. POWER REACTOR LICENSEES ALL NON-POWER REACTOR LICENSEES GL 87-12 50.54(f) LETTER RE. LOSS OF RESIDUAL HEAT REMOVAL (RHR)DUFING MID-LOOP OPERATION 07 / 09/87 ALL LICENSEES OF OPERATING PWRS AND HOLDERS OF CONSTRUCT
I ON PERM ITS FOR FPWR' S GL 87-11 GL 87-10 RELAXATION
IN ARBITRARY INTERMEDI
ATE PIPE RUFTURE REQU I REMENTS IMPLEMENTATION
OF 10 CFR 73.57, REQUIREMENTS
FOR FBI CRIMINAL HISTORY CHECk:S 06/23/87 06/12/87* ALL OFPERATING
LICENSEES, CONSTRUCTION
PERMIT HOLDERS, AND APPLI CANTS FOR CONSTRUCTION