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UNITEJ 8TATES f
NUCLEAR REGULATORY COMMISSION 3
WASHINGTON, D. C. 30644
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May 16. 1986 Decket Fo. 50-293 MEMORANDtJM FOR:
H. Denton R. W. Houston D. Eisenhut D. Crutchfield J. Lyons E. Rossi H. Thompson G. Lainas F. Miraglia T. Speis R. Bernero W. Russell G. Holahan V. Benaroya T. Novak W. Rega.,
F. Schroeder D. Vassallo D. Muller E. Adensam
.V W. Butler I
THRV:
John A. Zwolinski, Director BWR Project Directorate il
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Division of BWR Licensing FRDM:
Divisien of BWR Licensing
SUBJECT:
DAILY HIGHL GHT
, Pilgrim Nuclear Power Station At midnight (24:00 hours), L../
l 15, 1986, a strike of union members at Boston Edison Company comenced on a company-wide basis. The reason for the strike was failure to agree on terms for renewal of the union-company contract which expired at that time.
1 Pi'igrim's control room is being staffed by se'. tor reactor operators foi the duratica of the strike. The plant is still shutdown for repairs (see Highlicht Hay 5,1986) but is expected to restart ne.r week if the Recional Ad:11nistrator i
so authorizes, d
u.c Paul H. Leech, Project Manager RWR Project Directorate #1 Division of BWR Licensing t
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J 8810270077 380926 PDR FOIA JOHNSONOB-198 PDR
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O SSINS No.:
6820
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3150-0012 IEB 86-01
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, DC 20555 May 23,'1986 IE COMPLIANCE BULLETIN NO. 86-01: MINIMUM FLOW LOGIC PROBLEMS THAT COULO i
OISABLE RHR PUMPS Addressees _:.
All GE boiling water reactor (BWR) facilities holding an operating Ilcense (OL) l or a construction permit (CP).
Purpose:
The purposes f this bulletin are:
(1) to inform BWR licensees and applicants.
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of a recenti identified problem with theiminimum flow logic for which a single failure co d disable all RHR pumps, (2) to request that licensees affected by the proble immediately provide appropriata instructions and training to plant operators to recognize the problem if it occurs and take appropriate mitigating 3
t actions, (3) to request that licensees notify the NRC of the existence of the problem at their facility within 7 days of receipt of this bulletin, and (4) to request that licensees inform the NRC of measures taken to correct design or installation problems that are identified as a, result of this bulletin.
Oescription of Circumstances:
During a recent review of IE Information Notice 85-94, "Potential For Loss Of Mininum Flow Paths leading To ECCS Pump Damage Ouring A LOCA." the Pilgrim I
Nuclear Power Plant discovered that a single failure under certain accident l
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sequences could result in all RHR minimum flow bypass valves being signaled to This condition close while all other pump discharge valves are also closed.
could result in no flow through the RHR pumps and could lead to the pumps running l
J dead headed with potential for pump damage in a few minutes.
If this single i
failure occurred in conjunction with an automatic start of the RHR system, RHR This event could disable pump damage may occur if unrecognized by the operator.
RHR functions including iow Pressure Coolant Injection (LPCI), head spray, drywell spray, shutdown cooling, torus spray and suppression pool cooling.
As a result of the loss of suppression pool cooling over a long period of time, l
core spray pumps could ultimately lose net positive suction head and also be l
unavailabl9.
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4 IEB 86-01 May 23, 1986 Page 2 of 3 The NRC staff has judged that the overall probability of a serious co.e damage accident due to this problem is low.
Nevertheless, such a single failurc vulnerability is not in compliance with the1 regulatory reqt.iremeat. for independence in emergency c' ore cooling systems and could. comp ~romise several important systems.
GE's initial review identified the following plants with some potential for having the single failure problem: Pilgrim; Browns Ferry 1, 2 and 3; Peach Bottom 2 and 3; Duane Arnold; Hillstone 1; Monticello; Quad Cities 1 and 2; Oresden 2 and 3: Cooper; and Fermi 2.
The staff understands that GE has notified these facil' ties and informal communications from GE indicate that the list was arrowed tduring preparation of. the bulletin.
H wcrthele n, fn'ete 4 b b '
plants are b ing provid the bulletin by telecopy.
Since there is not complete certainty t at other BWR' o not have the problem, they are also addressed by eing sent by (mail,p >y
$% Ab[a A f bA this uulle n.
Thei c les a k&
a ump from running dead,heade'd, each pair of RHR AtPilgrim,tdpreventte p ups is provided with a minimum flow bypass capability.
The minimum flow s consists of an orificed flow bypass which allows a flow of approximately h
" of rated flow. The minimum flow bypass lines for each pair of RHR pump nnected to. lingle line and c,ontrolled by a single minimum flow bypass valve.
The minimum flow bypass valve is normally'open.
The valve will close upon sensing flow in either of the RHR loops.
The current logic configuration'for Pilgrim minimum flow bypass valves is that i.,9n t ic-signal from either the A or B RHR loops will close both A and 8 a
bypass valves.
Thus, a postulated single failure of a flow sensing instrument may result in all RHR pumos running without bypass flow.
If this failure occurs during an event with a h,gh drywell signal or lo.t water level signal, such as during small or intermediate size loss of cooling accidents (LOCA) or spurious actuation, the RHR pumps may start and run dead headed.
q One of the potential fixes being proposed by GE 's to remove the losing signal from the RHR minimum flow bypass valves.
This fix will result in some of the LPCI flow being diverted through the minimum flow line.
For other RHR n.udes of operation, the valves may b ma 1
closed.
Although safety analyses may justify his interim fix, there are a number of l
problems that need to be considere c #n.nany plants, the minimum flow bypass
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urt be closed during shutdown cooling in order to prevent draining the reactor vessel inventory to the torus.
Tha minimt,.n flow bypass valves are u m iuered containment isolation valves on some plants.
REQUIRED ACTION FOR GE BWR FACILITIES 1.
Promptly determine whether or not your facility has this single failure vulnerability.
2.
If the problem exists, immediately instruct all operating shifts of the problem and measures to recognize and mitigate the problem.
IEP 85-01 May 23, 1986 Page 3 of 3 3.
Within 7 days of receipt of this bulletin, provide (a) a written report to the NRC which identifies whether or not thic problem exists at your facility, (b) if the problem exists, ident,1fy the short-term modifications to plant operating procedures or hardware that h/te'been or are being implemented to assure safe plant operations.
4.
If the problem exists, provide a written report within 30 days of receipt of tnis bulletin informing the NRC of the schedule for long-term resolution of problems that are identified as a result of tnis bulletin. '
Should a licensee determine that any action requested by this bulletin jeopardizes overall plant safety, the NRC should be notified of that fact and provided with appropriate justification for not implementing the requested action.
Such notification shall be made within 7 days of receipt of this bulletin.
The written reports shall be submitted to the aporopriate Regional Administrator under oath or affirmation under provisions of Section 182a, Atomic Energy Act of 1954, as amended.
Also, the original copy of the cover letters and a copy of the reports shall be transmitted to the U.S. Nuclear Regulatory Commission, Document Control Desk, Washington, D.C. 20555 for reproduction and distributicn.
This request for information was approved by the O'ffice of Management and Budget under'a blanket clearance number 3150-0011.
Comments on burden and duplication may be directed to the Office of Nnagement and Budget, Reports Management, Room 3208, New Executive Office Building, Washington, D. C. 20503.
If you have questions regarding this matter, please contact the Regional Administrator of the appropriate NRC Regional Office or one of the technical cc,ntacts listed below.
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1 James M. Taylor, Director Office of Inspection and Enforcement Technical Contacts:
Eric Weiss, IE (301) 492-9005 i
i M. Wayne Hodges, NRR (301)492-7483 Attachment-List of Recently Issued IE Bulletins J
IEB 86-01 May 23, 1986 Page 3 of 3 3.
'ithin 7 days of receipt of this bulletin, provide (a) a writt.n report o the NRC which identifies whether or not this problem exists at your facility, (b) if the problem exists, identify the short-ters. modifications to plant' operating procedures or cardware that have b,een or are being implemented to assure safe plant operations.
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If the problem exists, provide a written report within 30 days o.' receipt of'this bulletin informing the NRC of the schedule for long-term resolution of problems that are identified as a result of this bulletin.
Should a licensee :letermine that any action requested by this bulletin jeopardizes overall plant safety, the NRC should be notified of tiat fact and provided with appropriate justification for not implementing the requested action.
Such notification shall be made within 7 days of receipt of this bulletin.
The written reports shall be submitted to the appropriate Regional Admit.istiator l
under oath or affirmation under provisions of Section 182a, Atomic Energy Act of 1954, as amended. Also, the original copy of the cover letters and a copy t
of the reports shall be transmitted to the U.S. Nuclear Regulatory Commission -
Document Control Desk, Washington 0.C. 20555 for reproduction and distribution.
i l
This request for information was approved by the Office of Management and Budaet under a blanket clearance number 3150-0011. Comments on burden and duplication may be directed to the Office of Management and Budget. Reports 4
Manegement, Room 3208, New Executive Office Building, Washington, O. C. 20503.
l If you hoe questions regarding this matter, please contact the Regional Administra 6 r of the appropriate NRC Regional Office or one of the technical contacts listed below, l
i i
l James M. Taylor, Director Office of Inspection and Enforcement l
Technical Contacts:
Eric Weiss, IE (301) 492-9005 M. Wayne Hodges NRR (301) 492-7483
Attachment:
List of Recently Issued IE Bulletins l
EAB:0EPER:IE EAB:0EPER:IE NRR 00:0EPER:IE 0:0EPER:IE EWWeiss:ew 0Allison MWHodges SASchwartz ELJordan 5/ /86 5/ /86 5/ /86 5/ /86 5/ /86 4
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May 23, 1986 LIST OF RECENTLY ISSUED IE BULLETINS Bulletin Date of No.
Subject Issue Issued to 85-03 Motor-Operated Valve Common 11/15/85 All power reactor Mode Failures During Plant facilities holding Transients Cue To Improper an OL or CP for Switch Settings action 85-02 Undervoltage Trip 11/5/85 All power reactor Attachments Of Westinghouse licensees and 08-50 Type Reactor Trip applicaats Breakers 85-01 '
Steam Binding Of Auxiliary 10/29/85 Nuclear power facil-Feedwater Pumps ities and cps listed in attachment 1 for action; all other nuclear power facil-ities for information 84-03 Refueling Cavity Water Seal 9/24/84 All power reactor facilities holding an CL or CP except Ft. St. Vrain 84-02 Failures Of General Electirc 3/12/84 All power reactor Type HFA Relays In use In facilities holding Class 1E Safety Systems an OL or CP 84-01 Cracks In Boiling Water 2/3/84 All BWR facilities Reactor Mark I Containment with Mark I contain-Vent Headers ment and currently in cold shutdown with an OL for action and all other BWRs with an OL or CP for information OL = Operating License CP = Construction Permit
4 SSINS No.:
6835 IN 86-39 UNITED STAYS
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NUCLEAR P.EGULATOR) Cc.AISSION OFFICE OF INSPECTION AND ENFORCEMENT Washington, DC 20555 i
May 20, 1986 IE INFORMATION NOTICE NO. 86-39:
FAILURES OF RHR PUMP MOTORS AND PUMP INTERNALS Addressees:
All nuclear power reactor facilities ht!di..g an operating license (OL) or a construction permit (CP).
Purpose:
This notice S provided to alert licensees to serious damage which has occurred at a licensed nuclear power plant to restuual heat removal (RHR) pumps manufac-tured by Bingham-Willamette with motors supplied by General Electric.
The damage identified at the Philadelphia Ele:tric Co. (PECO), Peach Bottom facility involved failure of motor bearings and/or failure of pump impeller wear rings.
It is expected that recipients will review this notice for applicability to
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their facilities and consider actions, if appropriate, to preclude a similar problem occurring at their facilities.
However, suggestions cor.tained in this notice do not constitute requirements; therefore, no specific action or written response is requind.
Description of Circumstances:
On November 2, 1985, during core reload of PECO's Peach Bottom Unit 3, a fire occurred in the 3C RHR pump motor which totally engulfed the motor and renoered t;.. swp inoperable.
A lower guide bearing high temperature alarm had been received for 3 days prior to the pump failure, but this warning of potential pump failure went unnoticed by personnel because of the large number of other alarms that were received during the shutdown.
The motor, a 2000 HP GE verti-cal induction model 5K6348XC29, and pump, a Bingham-Willamette single stage centrifugal m7 del 18x24x28 CVIC (Figure 1), were uncoupled, disassembled and inspected for damage.
Results of the inspection identified that the motor lower guide bearing was destroyed, the rotor bars were gouged and scorched, and the stator windings were burned and gouged.
The pump internals were found to have sustained internal damage.
Specifically, the lower impeller wear ring (Figure 1) was separated from the impeller and fused to the casing wear ring.
No other wear surfaces indicited wear or damage.
On November 16, 1985, while replacing the lower pump casing gasket on the 3A RHR pump, PECO personnel discovered that the lower pump impeller wear ring was separated from the impeller and cracked in three places.
Subsequent inspections of the remaining two unit 3 RHR pumps and two unit 2 pumps (2A and 2C) revealed similar wear ring failures in three of the pumps inspected.
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IN 86-39 May 20, 1986 Page 2 of 3 i
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On December 22, 1985, after several overcurrent alarms with pump 20 from Unit 2, PECO inspected this pump and discovered the lower pump impeller wear ring l
separated and cracked, a 6-inch piece of wear ring missing, and the impeller vanes damaged.
Not all failur:s noted above were as severe as the ones l
identified on pun.rs 3C and 20.
However, the similarity was evident.
l The RHR pump impeiler wear rings are press fit to the impeller and attached with eight dowel pins.
The wear rings provide a wearing surface on the pump impeller.
The wear rings are 410 stainless steel, A 182 grade F6 with a Rockwell C hardness of 33 to 39.
Metallurgical examinations of the wear ring fracture surfaces indicate the presence of intergranular stress corrosion cracking (IGSCC).
PECO has classified the wear ring failures as IGSCC.
On November 26, 1985, PECO made an INPO Network notification regarding these RHR pump failures.
PECO has repaired all affected pumps by replacement of damaged motors and pump internals.
Tennessee Valley Authority's Browns Ferry Units 1, 2, and 3 utilize the identical pumps for RHR service.
Similar motor and pump impeller wear ring failures have occurred at these facilities, but not to the extent identified at Peach Bottom.
Pumps of similar design, but different size, are utilized for core spray service both at Peach Bottom and Browns Ferry.
However, these pumps use the "integral" impeller wear ring design, i.e.,
extended impeller part replaces separate wear ring and forms a single unit, and therefore are not susceptible to the type of wear ring failure previously described.
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Discussion:
These multiple events are of concern because of the potential for common-mode failures of all pueps in the same system.
At Peach Bottom, six of eight pumps inspected exhibited degraded pump impeller wear rings and internals.
These flaws could lead to pump hydraulic degradation and, under the worst conditions, complete pump failure. The motor guide bearing failures are signi-ficant because they could cause failure of the pump motors and pump internal damage.
The full extent to which this type of pump m y be used in safety-related services at other facilities is not known with complete certainty.
According j
to information asce*tained from Bingham-Williamette records and confirmed by contact with affected sites, other plants utilizing this type of pump in the j
RHR system include the following:
Cooper, Pilgrim 1, and Vermont Yankee.
The exact cause of the pump internal failures has not been fully determined, except that there is evidence that IGSCC has contributed to the impeller wear ring failures.
Operating pumps with inadequate flow and'1ubrication, whereby l
high internal temperatures develop, is also a likely contributor, e.g., pump l
cavitation.
PECO is continuing to pursue root causes and wear ring redesigns l
to prevent such occurrences in the future.
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IN 86 39
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May 20, 1986 Page 3 of 3
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No specific action or written response is required by this information notice.
If you haya any questions regarding this matter, please contact the Regional Administrator of the apprcpriate NRC regional office or the technical contact listed below.
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dward L. Jordan, Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement Technical
Contact:
Ronald M. Young
' (301) 492-8985
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Attachments:
1.
Figure 1 - Typical CVIC RHR Pump Sectional Assembly 4
2.
List of Recently Issued IE Information Notices 4
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FIGURE 1 - Typical CVIC RHR Pump Sectional Assembly
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