View source for Information Notice 1986-40, Degraded Ability to Isolate the Reactor Coolant System from Low-Pressure Coolant Systems in Bwrs

{{Adams
| number = ML031250039
| issue date = 06/05/1986
| title = Degraded Ability to Isolate the Reactor Coolant System from Low-Pressure Coolant Systems in Bwrs
| author name = Jordan E L
| author affiliation = NRC/IE
| addressee name = 
| addressee affiliation = 
| docket = 05000000, 05000003, 05000010, 05000029, 05000133, 05000155, 05000206, 05000213, 05000219, 05000220, 05000237, 05000244, 05000245, 05000247, 05000249, 05000250, 05000251, 05000254, 05000255, 05000259, 05000260, 05000261, 05000263, 05000265, 05000266, 05000267, 05000269, 05000270, 05000271, 05000272, 05000275, 05000277, 05000278, 05000280, 05000281, 05000282, 05000285, 05000286, 05000287, 05000289, 05000293, 05000295, 05000296, 05000298, 05000301, 05000302, 05000304, 05000305, 05000306, 05000309, 05000311, 05000312, 05000313, 05000315, 05000316, 05000317, 05000318, 05000320, 05000321, 05000322, 05000323, 05000324, 05000325, 05000327, 05000328, 05000329, 05000330, 05000331, 05000333, 05000334, 05000335, 05000336, 05000338, 05000339, 05000341, 05000344, 05000346, 05000348, 05000352, 05000353, 05000354, 05000358, 05000361, 05000362, 05000364, 05000366, 05000368, 05000369, 05000370, 05000373, 05000374, 05000382, 05000387, 05000388, 05000389, 05000390, 05000391, 05000395, 05000397, 05000400, 05000409, 05000410, 05000412, 05000413, 05000414, 05000416, 05000417, 05000423, 05000424, 05000425, 05000437, 05000438, 05000439, 05000440, 05000441, 05000443, 05000444, 05000445, 05000446, 05000454, 05000455, 05000456, 05000457, 05000458, 05000461, 05000482, 05000483, 05000498, 05000499, 05000508, 05000522, 05000523, 05000528, 05000529, 05000530, 05000546, 05000547
| license number = 
| contact person = 
| document report number = IN-86-040, NUDOCS 8606030014
| document type = NRC Information Notice
| page count = 5
| revision = 0
}}
{{#Wiki_filter:LIS ORIGINALNo: 6835R E C E IVE DUNITED STATES Bart D. WithersNUCLEAR REGULATORY COMMISSION Vice Presdent. NuclearOFFICE OF INSPECTION AND ENFORCEMENT *JlJjfi 131986WASHINGTON, D.C. 20555 Route To: ..'eL _June 5, 1986IE INFORMATION NOTICE NO. 86-40: DEGRADED ABILITY TO ISOLATE THE REACTORCOOLANT SYSTEM FROM LOW-PRESSURE COOLANTSYSTEMS IN BWRS

==Addressees==
:All nuclear power reactor facilities holding an operating license (OL) or aconstruction permit (CP).

==Purpose==
:This notice is provided as a supplement to Information Notice (IN) 84-74 oninterfacing systems loss-of-coolant accidents (LOCA) in boiling water reactors(BWRs) which would bypass primary containment. Two recent events are describedwhere the high-pressure reactor coolant system could not be fully isolated fromlow-pressure piping systems outside of primary containment.It is expected that recipients will review the information for applicability totheir facilities and consider actions, if appropriate, to preclude similarproblems from occurring at their facilities. However, suggestions contained inthis information notice do not constitute NRC requirements; therefore, nospecific action or written response is required.

==Description of Circumstances==
:PilgrimOn February 13, 1986, Pilgrim experienced a "design pressure" alarm on the Bloop of the residual heat removal (RHR) system because of leakage through acheck valve (1001-68B) and a motor-operated Isolation valve (1001-288, theoutboard, normally closed, isolation valve) in the line (see Figure 1). TheRHR system has a design pressure of 450 psig compared with a 1250 psig designpressure of the reactor coolant system. In addition to design pressure alarms,the piping up to the 288 valve had become warm. Several design pressure alarmshad occurred during the preceding several weeks. The licensee's prior correc-tive action had been to vent the lines. On February 13, the licensee closedthe normally open 1001-29B valve and opened the 288 valve to isolate thesystem. The licensee planned to operate in this configuration until a sched-uled refueling and maintenance outage in September 1986.Copies to: YWethers, Yundt, Lentsch, Orser, Steele, E. Burton, E. Jordan, A. Holm,-.LIS,'C. A. Olmstead, S. Hoag, S. Sautter, TNP:GOV REL F:NRC CHRONO,TNP:GOV REL F:NRC IE Information Notice 86-40PGE OAR Action -M. H. Malmros (Due 9/12/86)NSRD Action -M. H. MalmrosI ,, ' :,
IN 86-40June 5, 1986 On April 11 and 12, 1986, the closed 29B valve began leaking. Several highpressure alarms were reported. The licensee bled off the line to reducepressure and began an orderly shutdown, but within a short period of time, thehigh pressure alarm was again received. The 28B valve was closed, but theleakage problem continued. The shutdown rate was then increased until the unitscrammed because of other problems. An NRC augmented inspection team wasdispatched to the site to investigate these RHR valve problems and two problemsin other systems.Duane ArnoldOn March 15, 1986, while reducing power for an outage, Duane Arnold reportedclosing the outboard LPCI (low-pressure coolant injection mode of RHR) isola-tion valve MO-2004 due to leakage through the inboard isolation valve MO-2003(see Figure 2).Because the leakage flow was relatively small, the ap across the check valveinside of containment (CV-2002) was not high enough to seat the check valve.The problem was discovered when it was noted that the pressure controllers onthe RHR heat exchangers were indicating a pressure of 450 psig rather than thenormal 70 psig. RHR system relief valves had lifted to keep pressure at orbelow 450 psig. Closing the MO-2004 valve stopped the leakage, but because theplant has loop selection logic, both loops of LPCI were rendered inoperable.The plant continued its planned shutdown and reached cold shutdown on March 16.s_ The leaking valves were repaired during the outage.Discussion:The underlying cause of this problem is leaking valves, one of which is inac-cessible with the plant at power. Possible solutions include increased sur-veillance, preventive maintenance, and reliability-based replacement. OtherBWR systems that can be subject to similar problems include but are not limitedto core spray, high pressure coolant injection system (see IE Information Notice84-74), and reactor core isolation cooling.It is possible for leakage to exist from the reactor coolant system to a lowpressure system without causing a high pressure alarm or lifting of safetyvalves in the low pressure system. For example, for the preceding events, ifthe check valve at the discharge of one of the RHR pumps is leaking, thereactor coolhnt will flow to the suppression pool. Hence, slowly increasinglevel in the suppression pool is one indication that there is leakage from thereactor coolant system to the low pressure RHR system, and degradation of thereactor coolant pressure boundary. If leakage through the degraded valves wereto increase suddenly, a severe accident could result, as described in thefollowing paragraph. Further, it should be noted that such leakage does notmeet the intent of general design criteria 14, 30, and 54 of Appendix A to 10CFR Part 5 IN 86-40.June 5, 1986 The leaking of primary coolant into RHR lines that were never meant to containfluid at that temperature and pressure can cause a number of incidents:over-pressurization with possible faulting of the low pressure line and a LOCA,steam binding of one or more of the RHR pumps, and waterhammer. The safetysignificance of these events is the increased probability of core melt andreleases in excess of 10 CFR 100 limits. The Office of Nuclear Reactor Regula-tions has designated this topic Generic Issue number 105, "Interfacing SystemsLOCA at Boiling Water Reactors," and has given it a "high" priority. A genericletter concerning staff actions relating to this topic is being considered.No specific action or written response is required by this information notice.If you have any questions about this matter, please contact the RegionalAdministrator of the appropriate regional office or this office.Divisio oEmrnc epre n Xsand Engineeri g ResponseOffice of Inspection and Enforcement

===Technical Contact:===
Mary S. Wegner(301) 492-4511

===Attachments:===
1. Simplified RHR Diagrams2. List of Recently Issued IE Information Notices 
.4.Attachment 1IN 86-40June 5, 1986SIMPLIFIED RHR DIAGRAMSFigure 1(Original Condition)Figure 2(Original Condition)RHR PumpIP-229CExchanger A Attachment 2IN 86-40June 5, 1986LIST OF RECENTLY ISSUEDIE INFORMATION NOTICESInformation Date ofNotice No. Subject Issue Issued to86-3986-38Failures Of RHR Pump MotorsAnd Pump InternalsDeficient Opera; 'r ActionsFollowing Dual Function ValveFailuresDegradation Of StationBatteriesChange In NRC PracticeRegarding Issuance OfConfirming Letters ToPrincipal Contractors5/20/865/20/865/16/8r5/16/8686-3786-3686-3586-3486-3386-3286-31Fire In Compressible Material 5/15/86At Dresden Unit 3All power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL.or CPFuel cycle licenseesand Priority 1 materiallicenseesAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or a CPImproper Assembly, MaterialSelection, And Test Of ValvesAnd Their ActuatorsInformation For LicenseeRegarding The ChernobylNuclear Plant AccidentRequest For Collection OfLicensee RadioactivityMeasurements Attributed ToThe Chernobyl Nuclear PlantAccidentUnauthorized Transfer andLoss of Control ofIndustrial Nuclear Gauges5/13/865/6/865/2/865/6/86OL = Operating LicenseCP = Construction Permit}}

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