ML20246A661
| ML20246A661 | |
| Person / Time | |
|---|---|
| Issue date: | 06/20/1989 |
| From: | Sniezek J Office of Nuclear Reactor Regulation |
| To: | Jordan E Committee To Review Generic Requirements |
| Shared Package | |
| ML19306D150 | List: |
| References | |
| NUDOCS 8907070056 | |
| Download: ML20246A661 (30) | |
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$~ UNITED STATES J p, NUCLEAR -REGULATORY COMMISSION j
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i MEMORANDUM FOR: Edward L. Jordan, Chairman j Committee to Review Generic Requirements 1
'FROM: James H. Sniezek, Deputy Director Office of Nuclear Reactor Regulation
SUBJECT:
FINAL GENEPIC LETTER ON SERVICE WATER SYSTEM PROBLEMS The Committee to Review Generic Requirements (CRGR) met on May 10, 1989 to consider antong other items our proposed generic letter regarding service water system problems affecting safety-related equipment. As requested in the CkGR meeting, we have sent you a separate memorandum dated June 12, 1989 to give the staff's position on the risk addressed by the proposed generic letter. In addition, the staff has met with the Advisory Committee on Reactor Safeguards (ACRS), first with the Subcommittee on Auxiliary and Secondary Systems on May 24, 1989, and then with the full committee on June 8 and June 1.0, 1980 The ACRS issued a letter to the Comission dated June 14, 1989 (Enclosure 1, annotated). The staff has considered both the CRGR and ACRS comments and has modified the proposed generic letter. A marked up copy is enclosed (Enclo-sure 2) to indicate what changes have been made to the draft generic letter that was discussed with you on May 10. The final generic. letter incorporating both CRGR and ACRS comments is enclosed (Enclosure 3). We plan to issue this generic letter unless the CRGR wishes to discuss it again with the staff. Please inform us as soon a3 you can of your wishes in this matter.
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L e t[.;1," y M #A - James H. Sniezek, Deputy Dd[ rector Offi:e of Nuclear Reactor Regulation J
Enclosures:
- 1. ACRS Letter, Annotated
- 2. Marked Up Generic Letter
- 3. Final Generic Letter CONTACT: C. Vernon Hodge, NRR 492-1169 f -
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A , fy : Q ase g , UNITED STATES 1 ' ' e NUCLEAR REGULATORY COMMISSION Enclosure 1 y o } ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WA8HINGTON, D. C. 20806 June 14, 1989 x The Honorable Lando W. Zech, Jr. Chairman. U.S. Nuclear Regulatory Comission Washington, D.C. 20555
Dear Chaiman Zech:
SUBJECT:
PROPOSED GENERIC LETTER REGARDING SERVICE WATER SYSlEM PROBLEMS
.AFFECTING SAFETY-RELATED EQUIPMENT During- the 350th meeting of the Advisory Comittee on Reactor Safeguards, June 8-10. .1989, we discussed the proposed generic letter regarding Service Water System Problems Affecting Safety-Related Equipment. Our . Subcommittee on: Auxiliary and Secondary Systems met with' representatives of.the NRC staff '.!
and the industra on May 24, 1989 to discuss this matter. We also had the benefit of the documents referenced. Nuclear power plant operating experience and studies have led the NRC staff to question 'whether -service water systems generally comply with 10 CFR Part
. 50, Appendix A, General Des:gn Criteria 44, 45. and 46, and other applicable criteria. Consequently,: the staff is proposing to issue the subject generic letter to require that licensNs and applicants perform five' specific. actions to assure that their safety-related service water systems are and continue to be in compliance with the applicable criteria and te ensure system functional capability. I The' actions specified in the proposed generic letter are: '(1) implement an appropriate program. to control biofouling in open-cycle service water sys-tems, (2) ' verify heat transfer capability for 'all safety-related heat ex-changers, (3) implement a routine inspection and maintenance program for all open-cycle service water system piping and components. (4) confirm functional capability in accordance with the licensing design basis, and (5) confim the adequacy of the maintenance practices, operating and emergency procedures, and training.
Although we are in general agreement with the need to issue the proposed letter, we do have the following comments concerning its scope and content. O'The proposed generic letter defines a service water system as an open-cycle or closed-cycle cooling water system that transfers heat from safety-related structures, systems, or components to an ultimate heat sink. Operating experience and studies cited by the staff indicate clearly that open-cycle systems may become degraded by biofouling agents, corrosion products, chemicals, mud, silt, or debris. The staff did. not present sufficient evidence to substantiate a belief that mn ,-
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The Honcrable Lando W. Zech, Jr. June 14, 1989 l 1 R
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closed-cycle systems that use clean chemically treated water are likely to experience safety-significant degradation as a result of water conditions. Absent convincing technical evidence and because of the high cost and increased occupational radiation exposure involved, we do not believe that the blanket inclusion of closed-cycle. systems in the t
. generic letter is justified at this time. Iq, p. Sj ff y ,,3f, i
" Althcugn the scope of the proposed letter should be limited to systems that use raw cooling water or treated water which is exposed to the L environment (e.g., in cooling ponds or basins), we believe that if any component in these systems, such as a heat exchanger, is found to be l
degraded on the raw water side and heat transfer cannot be restored sufficier.tly. -then the clean water side of the component should be
^ inspected. Incorp p. 5, J,9, Ig,t gat Although not included in the proposed letter, the. staff discussed using !
the ebsence of an adequate water chemistry control r m gram over'any part l . of the operating history of a closed-cycle syster, as a basis'for includ-
'ing that system-within the scope of the letter. We do not agree that this would be'a sufficient basis. Inarp, f.f f,p H /sst .5mf ; afic fe:
n The, proposed letter requires adethe ac verifkatkn4;emen,ce of du cmb n of heat fransfer capabN-ity for all s1fety-related heat exchangers cooled by service water. The letter should make clear that a heat. transfer test, involving detailed flow'and temperature measurements, is not the only means of determining the functional adequacy of such heat exchangers. Other methods to determine and ensure adequacy may be sufficient and less resource-intensive. Inu9.p.5 241fh 3 2alsed U Theproposedletterrequiresthateachlicenseeconfirmthatitsservice water systems ,will accomplish their intended functions in accordance with the current licensing basis. This could be interpreted to mean backfitting' to current regulatory requirements. The staff has stated tnat it means to use the original licensing basis for the plant in question. We agree, and this should be clarified in the letter. y cep p. 4 412;ist sud. 3 We recommend that the proposed generic letter not be issued until these coments have been resolved. Sincerely, 1 Forrest J. Remick Chairman
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l The 1:u.crable Lando W. Zech, Jr. June 14, 1989-1
References:
- 1. Memorandum dated May 4,1989 from James H, Sniezek, Office of Nuclear l Reactor Regulation, NRC, to Edward L. Jordan, Chairman, Comittee to I Review Generic Requirements, NRC, transmitting the Proposed Generic Letter Regarding Equipment -(Internal Service ACRS Use Water Only Sy) stem Problems Affecting Safety-Related
- 2. U.S. Nuclear Regulatory Comission, NUREG-1275. Volume 3, " Operating Experience Feedback Report - Service Water System Failures and Degrada- j tions " fiovember 1988 4
- 3. U.S. Nuclear Regulatory Comission, NUREG/CR-5234, "Value/ Impact Analy-sis for Generic Issue 51:. Improving the Re*.tability of Open-Cycle Service-Water Systems," February 1989
- 4. U.S. Nuclear Regulatory Comission, NUREG/CR-5210. " Technical Findings Document for Generic Issue 51: Improving the Reliability of Open-Cycle !
Service-Water Systems," August 1988
- 5. Letter dated February 27, 1989 from William H. Rasin, NUMARC, to Edward L. Jordan, Chairman, Comittee to Review Generic Requirements, NRC, regarding NRC generic letter on service water system performance ]
- 6. Letter dated June 8,1989 from William H. Rasin, NUMARC, to Thomas E. I Murley, Office of Nuclear Reactor Regulation, NRC, regarding NRC generic )
letter on service water system performance j
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/ h,, UMTED STATES NLl CLEAR REGULATORY COMMISSION l f, r, fn _
enclosure 2 l 2 -) E m ssawatev.o.c.aosss E e q..... June 20,1939 T0; ALL HOLDERS OF OPERATING LICENSES OR CONSTRUCTION PERMITS ; i FOR HUCLEAR POWER PLANTS I
SUBJECT:
SERVICE WATER SYSTEM PROBLEMS AFFECTING SAFETY-RELATED EQUIPMENT l j (GENERIC LETTER 89-XX) f
Purpose:
l Nuclear power plant facilities of licensees and applicants must meet the ninimum requirements of the General Design Criteria (GDC) in 10 CFR Part 50, i Appendix A. In particular, "GDC 44--Cooling Water" requires provision of a i l
- system (here called the service water system) "to transfer heat from struc-tures, systems, and components important to safety to an ultimate heat sink" (UHS). "GDC 45--Inspection of Cocling Water System" requires the system design i "to permit appropriate periodic inspection of important components, such as heat exs. hangers and piping, to ensure the integrity and capability of the system." "GDC 46--Testing of Cooling Water System" requires the design "to permit appropriate periodic pressure and functional testing...."
In addition, nuclear power plant facilities of licensees and applicants must meet the minimum requirements for quality assurance in 10 CFR Part 50, 4 l Appendix B. In particular, Section XI, " Test Control" requires that "a test program shall be established to assure that all testing required to demonstrate CRGR ) that structures, systems, and components will perform satisfactorily in service is identified and performed in accordance with written test procedures which incorporate the requirements and acceptance limits contained in applicable design documents." i l Recent operating experience and studies have led the NRC to question the compliance of the service weter systems in the nuclear power plants of l licensees and applicants with these GDC and quality assurance requirements. Therefore, this generic letter is being issued to require licensees and appli-cants to supply inf ormation acout their respective service water systems to assure the NRC of such compliane and to confirm that the safety functions of i their respective service water s; stems are being met. j Backaround: ! l Bulletin 81-03: The MC staff has been studying the problems associated with service water cooling systems for a number of years. At Arkansas Nuclear One, f l Unit 2, on September 3,1960, the If tensee shut down the plant when the NRC Fesident Inspector discovered that the service water flow rate through tha l
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CONTACT: C. Vernon Hodge, NRR 492-1169
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.* l containment cooling units did not meet the technical specification requirement.
The licensee determined the cause to be extensive flow blockage by Asiatic clams (Corbicula species, a non-native fresh water bivalve mollusk). Prompted by this event and af ter determining that it represented a generic problem of safety significance, the NRC issued Bulletin 81-03, " Flow Blockage of Cooling Water to Safety System Components by Corbicula sp. (Asiatic Clam) and Mytilus sp. (Mussel). The bulletin required licensees and applicants to assess macroscopic biological fouling (biofouling) problems at their respective facilities in accordance with specific actions. A careful assessment cf responses to the bulletin indicated that existing and potential fouling problems are generally unique to each facility ("Closecut of IE Bulletin 81-03...", NUREG/CR-3054), but that surpris-ingly, more than half the 129 nuclear generating units active at that time were considered to have a high potential for biofouling. At that time, the activi- 1 ties of licensees and applicants for biofouling detection and control ranged ; widely and, in many instances, were judged inappropriate to ensure safety system reliability. Too few of the facilities witn high potential for
,biofoul ing had adopted effective control programs.
infora tion Notice 81-21: After issuance of Bulletin 81-03, one event at San Dnofre Unit I and two events at the Brunswick station indicated that conditions not explicitly discussed in the bulletin can occur and cause loss of direct access to the t!HS. These conditions include
- 1. Flow blockage by debris from shellfish other than Asiatic clams and I blue mussels ll
- 2. Flow blockage in heat exchangers causing high pressure drops that can deform baffles and allow flow to bypass heat exchanger tubes
- 3. A change in operating conditicns, such as a change from power opera-tion to a lengthy outage, that permits a buildup of biofouling organisms i The NRC issued Inf'ormation Notice No. 81-21 to describe these events and l concerns.
Generic issue 51: By March 1982 several reports of serious fouling events, by I mud, silt, corrosion products, or aquatic bivalve organisms, in open-cycle service water systems had been received. These events led to plant shutdowns, l reduced power operation for repairs and modifications, and degraded modes of operation. This led the NRC to establish Generic Issue 51, " Improving the Reliability of Open-Cycle Service Weter Systems." To resolve this issue, the NRC initiated a research program to compare alternative surveillance and control nrograms to minimize the effects of fouling on plant safety. Initial-ly, thi ;,rogram was restricted to a study of biofouling, but in 1987 the program was expanded te also address fouling by mud, silt, and corrosion products. This research program has recently been completed and the results have been published in " Technical Findings Document for Generic Issue 51... " NUREG/ CR-5210. The NRC has concluded that the issue will be resolved when licensees L - - - - - - - _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
f and applicants implement either the recommended surveillance and control program described below (Enclosure 1) or its equivalent for the service water system at their respective facilities. Many licensees experiencing service water macroscopic biofouling problems at their plants have found that these techniques will effectively prevent recurrence of such problems. The examina-tion of alternative corrective action programs is documented in "Value/ Impact Analysis for Generic Issue 51... " NUREG/CR-5234. Continuing problems: Since the advent of Generic Issue 51, a considerable number of events with safety implications for the service water system have been reported. A number of these have been described in information notices, listed in "Information Notices Related to Fouling Problems in Service Water Systems" (Enclosure 3). Several events have been reported within the past 2 years: Ocor.ee Licensee Event Report (LER) 50-269/87-04, Rancho Seco LER
. 50-312/87-36, Catawba LER 50-414/88-12, and Trojan LER 50-344/88-29. In the fall of 1988, the NRC conducted a special announced safety system functional ,
inspection at the Surry station to assess the operational readiness of the service water and recirculation spray systems. A number of regulatory viola-tions were identified (NRC Inspection Reports 50-280/88-32 and 50-281/88-32). AE00 Case Study: In 1987, the Office of Analysis and Evaluation of Operational Data (AE00) in the NRC initiated a systematic and comprehensive review and evaluation of service water system failures and degradations at light water reactors from 1930 to early 1987. The results of this AEOD case study are published in " Operating Experience Feedback Report - Service Water System Failures and Degradations," NUREG-1275, Volume 3 (Enclosure 4). j l Of 980 operational events involving the service water system reported during 1 this period, 276 were deemed to have potential generic safety significance. A l majerity (58 percent) of these events with generic significance involved system j fouling. The fouling mechanisms included corrosion and erosion (27 percent), ' biofouling (10 percent), foreign material and debris intrution (10 percent), sediment deposition (9 percent), and pipe coating failure and calcium carbonate deposition (1 percent). j The second most frequently observed cause of service water system degradations and failures is personnel and procedural errors (17 percent), followed by seismic deficiencies (10 percent), single failures and other design deficien-cies (6 percent), flooding (4 percent), and significant equipment failures (4 percent). During this period,12 events involved a complete loss of service water system function. Several of the significant causes listed above for system degrada-tion were also contributors to these 12 events involving system failure. The study identified the following actions as potential NRC requirements.
- 1. Cenduct, on a regular basis, performance testing of all heat exchang-ers, which are cooled by the service water system and which are needed to perform a safety function, to verify heat exchanger heat transfer capability.
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- 2. Require licensees to verify that their service water systems are not vulnerable to a single failure of an active component.
- 3. Inspect, on a regular basis, important portions of the piping of the service water system for corrosion, erosion and biofouling.
- 4. Reduce human errors in the operation, repair and maintena9ce of the service water system.
Recommended Actions to be taken by Addressees: cggg. theIas t i ssionabovh.theNRCrequeststhatlicenseesand applicants perform the following orph5! actions to ensure that their 3 'g A J, h service water systems are in compliance and will be maintained in compliance with 10 CFR Part 50, Appendix A General Design Criteria 44, 45, and 46.' If a D. b, licensee or applicant chooses a course of action different from the recom-mendations below, the licensee or applicant should document and retain in appropriate plant records a justification that -the heat removal requirements of the service water system are satisfied by use of the alternative program. Because the characteristics 'of the service water system may be unique to each facility, the service water system is defined as the system or systems that transfer heat from safety-related structures, systems, or components to the UHS. If an intermediate system is used between the safety-related items and the system rejecting heat to the UHS, it performs the function of a service water system and is thus included in the scope of this generic letter. A closed-cycle system is defined as a part of the service water system that is not subject to significant sources of contamination, one in which water chemis-try is controlled, and one in which heat is not directly rejected to a heat sink. If all these conditions are not satisfied, the system is to be consid- i ered an open-cycle system in regard tc the specific actions required below. ; (The scope of closed cooling water systems is discussed in the industrial
; standard " Operation and Maintenance of Nuclear Power Plants," ASME/ ANSI OM-1987,Part2.) ,
- 1. For open-cycle service water systems, implement and maintain an ongoing program of surveillance and control techniques to signifi- )
cantly reduce the incidence of flow blockage problems due to biofouling. A program acceptable to the NRC is described in "Recom-mended Program to Resolve Generic Issue 51" (Enclosure 1). It should be noted that Enclosure 1 is provided as guidance for an acceptable Yp?!% ~ program. AnDqutvalent program to preclude biofouling would also be M. e.{ Q ,vt acceptable. Initial activities should be completed prior to plant 5A startup following tne first refueling outage beginning 9 months or o more after the date of this letter. All activities should be docu-mented and all relevant documentation should be retained in appropri-ate plant records. ' of all II. Conduct safety-relateda heat testexchangers program cooledto verify the heat by service water.transfer The capability [ should consist of an initial test program and a periodic retest program. [he initial program,h Winclude heat exchangers cooled by ; BA
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yarim41c-confirmatory retdst-program-may be lihited to heat exchang- j I
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/ .ul 62'" i h - , Operating ex erience-dees indicate hat closed-cycle service I water systems, such as component cooling wat r systems, de experi:= o ' ve &
statial { significantfoulingtsaconsequenceofaging}relatedin-leakage erg jg p g g ; g g M m m*Qg]e.,?.g_-w any unexplained p3og , downward trend in heat exchanger perfoynce is identified wMA g S cannot be remedied by maintenance of-We-open-cycle system, it may be necessary to selectively extend the periodic etest program and the routine inspection and maintenance program addressed in Action III, i N A I below,totheglgdglesystems. 12de- 4 .
, A program acceptable to the NRC for heat scribed in "Proonm for Testing Heat Transfer Capability" exchanger testing (Enclosure ,
2). It should be noted that ' inclosure 2 is provided as guidance for ps # M" .j en acceptable program. A&eWi veMt program to ensure satisfaction of the heat removal requirements of the service water system would d t},df also be acceptable. Testing should be done with necessary and sufficientinstrumentation,thoughtheInsggmentationneednotbe Wrmanently installed.~ To =547meanin'gfurassessment of heat
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- tests should be performed for the k* Q vu ag g heat exchangers ny necessary corrective actions are takeng
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'p exchanger performance. The relevant temperatures should be verified M b]Jiu ed to be within design limits. If similar or equivalent test's have not ade#jy JNbeen performed 2
completedduring prior tothe plant past year,following startup the initialthetests should be first refueling outage og Jujdea beginning 9 months or more after the date of this letter. 4 In implementing the continuing program for periodic retesting of safety-related heat exchangers cooled by service water in open-cycle p4,,M [' / systems, the initial frequency of testing should be at least once each fuel cycle, but after 3 tests, licensees and applicants should
, determine the best frequency for testing to provide assurance that the equipment will perform the intended safety functions during the intervals between tests and meet the requirements of GDC 44, 45, and
- 46. The minimum final testing frequency should be once every 5 years. A surmary of the program should be documented, including the schedule for tests, and all relevant documentation should be retained in appropriate plant records.
i III. Er.sure by establishing a routine inspection and maintenance program for open cycle service water system piping and components that corrosion, erosion, protective coating failure, silting, and biofouling can not degrade the performance of the safety-related systems supplied by service water. The maintenance program should haveat}eastthefollowingpurposes:
, q .t 4 An extIple of an alternative action that would De acceptable to the NhC 15 frequent; maintenance of a heat exchanger in lieu fntght This alternative of tecting apply forto degraded small heat performente of the heat exchanger. * :k erenangers such as lube cil coolers or pump bearing coclers) n, r 3 0 ..
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*{niv'e# Yc7ssiv e e nw ionsofbiofoulingagents,c$rro-sion products, and silt; B. To repair defective protective coatings. and corroded service water system piping and components that could adversely affect performance of their intended safety functions.
This program'should be init'iated before the end of the next refueling outage and should be established prior to plant startup following the first refueling outage beginning'9 months after the date of this letter. A description of the program and the results of these maintenance inspections should be documented. All. relevant documen-tation'should be retained in appropriate plant records. IV. Confirm that the service water systen will angli;h its intended function in accordance with the r : t N licensing basis p f% 4 % incl dag enfti;, ti:n th:t 7:wir:d ::fety SnctienM:n b; .c - plished-4a th; a w.d. uf f.ilure ef a singl: :tive tempenent. is l confirmation should include recent (within the past 2 years) system ) walk-down inspections.- This confirmation should be completed prior i to plant startup following the first refueling outage beginning 9 months or fnore after the date of this letter. Results should be documented and retained in appropriate plant records. V. Confirm thet maintenance practices, operating and emergency proce-
'dures, and' training that involves the service water system are adequate to ensure that safety-related equipment cooled by the service water system will function as intended and that' operators of that equipment will perform effectively. This confirmation should include recent (within the past 2 years) reviews of practices, procedures, and training modules. The intent of this action is to reduce human errors'in the operation, repair, and maintenance of the service water system. This' confirmation should be completed prior to plant startup following the first refueling outage beginning 9 months or more after the date of this' letter. Results should be documented and retained in appropriate plant records.
Reportino Requirements: Pursuant to the provisions of Section 182a of the Atomic Energy Act of 1954, as amended, and 10 CFR 50.54 (f), each licensee and applicant shall advise the NRC whether it has established programs to implement recommendations I-V above of this generic letter or advise that it has pursued an equally effective alterna-tive course of action. -Each addressee's response to this requirement for information shall be made to the NRC within 180 days of receipt of this generic letter. Licensees and applicants shall include schedules of plans for imple- (RGR
- mentation of the various actions. ~ The detailed documentation associated with this generic letter should be retkined in Appropriate plant records.
l~ -The response shall be submitted to the appropriate regional administrator under l oath and affirmation under the provisions of Section 182a, Atomic Energy Act of 1954, as amended and 10 CFR 50.54 (f). In addition, the original cover letter and a copy of any attachment shall be transmitted to the U.S. Nuclear Regu-
' latory Commission, Document Control Desk, Washington DC 20555, for reproduction
- and distribution.
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n7 w u +aus .- - . u ; In addition to the 180-day response, each licensee and a'pplicant shall confirm to the NRC that all the recommended actions or their justifip alternatives have been implemented within 30 days of such implementation.3 This request is covered by the Office of Management and Budget Clearance Number 3150-0011, which expires December 31, 1989. The estimated average burden is 1000 man-hours'per addressee response, including assessing the actions to be taken, preparing the necessary plans, and preparing the 180-day response. This estimated average burden pertains only to these identified response-related matters and does not include the time for actuhl implementation of the recom-rnended actions. Em~ments on the accuracy of this estimate and suggestions to reduce the burden may be directed to the Office of Management and Budget, Reports Management, Room 3208, New Executive Office Building, Washington DC 20503 and to the U.S. Nuclear Regulatory Comission, Records and Reports Management Branch Office of Administration and Resources Management, Washing-ton DC 20555. 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. Addressee time necessary to perform the requested confirmation and any needed follow-up actions.
- 2. Addressee time necessary to prepare requested documentation.
If there are any questions regarding this letter, please contact the regional administrator of the appropriate NRC regional office or your project manager in this office.. - Sincerely, b
, James G. Partlow Associate Director for Projects Office of Nuclear Reactor Regulation
Enclosures:
- 1. " Recommended Cost-Effective Program to Resolve Generic Issue 51"
- 2. " Program for Periodically Testing Heat Transfer Capability"
- 3. "Information Notices Related to Fouling Problems in Service Water Systems" 4 " Service Water System Failures and Degradations in Light Water Reactors," NUREG-1275, Volume 3 l
l l
4 l 4 Enclosure 1 dL P, g# 'k l RECOMMENDED PROGRAM l TO RESOLVE GENERIC ISSUE 51
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This enclosure describes a program acceptable to the NRC for meeting the objectives of the requested Action I in the proposed generic letter. Both Action 1 and this enclosure are based upon the recommendations desc ibed in
" Technical Findings Document for Generic Issued 51: Improving the. Reliability of Open-Cycle Service-Water Systems." NUREG/CR-5210, February 1989.' The NRC has concluded that Generic Issue 51 will be resolved when licensees and appli-cants implement either the recommended surveillance and control program ad-dressed in this enclosure or an equally effective alternative course of action to satisfy the heat removal requirements of the service water system.
Water Source Surveillance Control
- . Type Techniques Techniaues Marine or Estuarine A B and C (brackish) or Freshwater with clams Freshwater without clams A and D B and C yeMi A. The intake structur should be visually inspected, an e per refueling cycle, for macros pic biological fouling organisms ( lue mussels at gg marine plants, rican oysters at estuarine plants, and Asiatic clams at freshwater plants. , sediment, and corrosion. Inspections should be O.
performed either by SCUBA divers, or by dewatering the intake structure, or by other comparable methods. Any fouling accumulationNshould be removed. g *> e,wply
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%- e The servfc&ewatersystemsho61dbecontinu(o ly hlorinated (or quidy2l\$
B. Jet 4 7-treated with anothe biocide) whenever the potential for a macro-c h tively scopic piological fouling pecies exists (blue mussels at marine plants, American oysters at estua ine plants, and Asiatic clams at freshwater pla nts'). Chlorination orkWent treatment is included for freshwater ACR6 plants without clams because it can help prevent microbiologically influ- 5b enced corrosion. However, the chlorination (or ^ not be as stringent for plants where the potenti$qu'velent) for macroscopic treatment bio-need logical fouling species does not exist compared to ose plants where it does. Precautions should be taken to obey federal, s 3te environmental regulations regarding the use of biocides.\, and locallgg,, t , g C. Redundant and infrequently used cooling loops should be flushed and flow tested periodically at the maximum design flow to ensure that they are not fouled or clogged. Other components in the service water system should be tested on a regular schedule to ensure that they are not fouled or clogged. Service water cooling loops should be filled with chlorinated or equivalently treated water before layup. Systems that use raw service
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5 2-c'jusilj e & b *Ij waterasasourpe,suchassomefireprotectionsystems,shouldalsobechlorinate A (M logically influenced corrosion. Precautions should be taken to obey Nb federal, state, and local environmental regulations regarding the use of biocides. 3 D. Samples of water and substrate should be collected annually to determine if Asiatic clams have populated the water source. Water and substrate ! sampling is only necessar.y at freshwater plants that have not previously j detected the presence of Asiatic clams in their source water bodies. If ' Asiatic clams are detected, utilities may discontinue this sampling p(JQg activity if desired, and the chlorination (or :;uivehr.t) treatment Ng program should be modified to be in agreemen with paragraph B, above. q.oll jeMedivt 9 e e
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1 PROGRAM FOR TESTIN( tlEAT TRANSFER CtPABILITY d This enclosure describes a program acceptable to the NRC for meeting the objectives of the requested Action II in the proposed generic letter. Both Action II and this enclosure are based in part on " Operating Experience Feeo- [ back Report - Service Water System Failures and Degradattor.s," NUREG-1275,
; Volume 3 and " Technical Findings Document for Generic Issue 51: Improving the !
)
j kliability of Open Cycle Service Water Systems," NUREG/CR-5210, March 1988. 1 This enclosure reflects continuing operational problems, inspection reports, and industry standards (" Operation and Maintenance of Nuclear Power Plants," i ASME/ANSIOM-1987,Part2.) The NRC requests licensees and applicants to
\ implement either the steps addressed in this enclosure or an equally effective '
s alternative course of action to satisfy the heat removal requirements of the service water system.
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A closed-cycle systen is defined as a part of the service water system that is not subject to significant sources of contamination, one in which rejected water to achemistry heat sink.is controlled, and one in which heat is, not directly (The scope of closed cooling water systems is dis-cussed in the industrial standard, " Operation and Maintenance of Nuclear Power Plants," ASME/ ANSI Part 2. W 9aWOM-1987,mned d. -) If M i 7 t r. 4 3 t.3 0.> r.1 O+vi..t ct fLt ud M.g i., b td W.." . g. W~ < Mht >. i rJ (le t < '.* t - h IE1Wpiemen"t'ingihNEntint}fnDiNalOfr' pen $c'Te's'titig,NeMkb $ I/!((icb frequency of testing should be at least once each fuel cycle. After 3 tests, e pba licensees and applicants should determine the best frequency for testing to provide reasonable assurance that the equipment will perform the interded safety functions during the intervals between tests. i frequency should not be less than once very 5 years. The minimum firal testing i Instrumentation neces-sary to accomplish thh testing shgpe ptp [ permanently insta11Q To eneMe meanin,c ftH^yided but this does not hsve to be
/ heat transfer e ability m ; r e utsh g ftssessment ?f D.c n;il dility of !
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[ changers be b e aYy neces,sary corrective actions are takerg Mt T : r.;, e te s-sery enrrect h: :ctfras ere ! *. measurements-should bc peii n :d m in to establish baseline data for future monitoring of heat excnanger performance. I. For all heat exchangers i~ Monitor and record cooling water flow and inlet and outlet tempera-
' tures for all affected heat exchangers during the modes of operation in which cooling water is flowing through the heat exchanger. For
' each measurement, verify that the cooling water temperatures and I flows are within design limits for the conditions of the measurement.
The test results from periodic testing should be trended to ensure l I that flow blockage or excessive fouling accumulation does not exist. II. In addition to the considerations for all heat exchangers in Item I, for water-to-water heat exchangers h a ao Aa a.,,h .4 M- +N "# ## L )g c,
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A. Perform functional testing with the heat exchanger operating, if practical, at its design hcat removal rate to verify its capa-bilities. Temperature and flow compensation should be made in the calculations _to adjust the results to the design conditions. Trend.the results, as explained above, to monitor degradation. An example of this type of heat exchanger would be that for cooling a diesel generator. Engine jacket water flow and temperature and service water flow and temperature could be monitored and trended during the diesel generator surveillance j testing. B. If it is not practical to test the heat exchanger at the design heat removal rate, then trend test results for the heat exchang-er efficiency or the overall heat transfer coefficient. Verify that heat removal would-be adequate for the system operating with the most limiting combination of flow and temperature. III. In addition to the considerations for all heat exchangers in item I, for air-to-water heat exchangers A. Perform efficiency testing (for example, in conjunt'; ion with . surveillance testing) with the heat exchanger operating under the maximum heat load that can be obtained practically. Test results should be corrected for the off-design conditions. Design heat removal capacity should be verified. Results should be trended, as explained above, to identify any degraded equipment.
. B. If it is not possible to test the heat exchanger to provide statistically significant results (for example, if error in the measurement exceeds the value of the parameter being measured),
. then
- 1. Trend test results for both the air and water flow rates in the heat exchanger
- 2. Perform visual inspections, where possible, of both the air and water sides of the heat exchanger to ensure cle:/iness of the heat exchanger IV. In addition to the considerations for all heat exchangers in Item I, for types of heat exchangers other than water-to-water or air-to-water heat exchangers (for example, penetration coolers, oil coolers, and motor coolers)
A. If plant conditions allow testing at design heat removal condi-tions, verify that the heat exchanger performs its intended functions. Trend the test results, as explained above, to monitor degradation.
B. If testing at design conditions is not possible, then provide
'for extrapolation of test data to design conditions. The heat exchanger efficiency or the overall heat transfer coefficient of the _ heat _ exchanger should be determined whenever possible.4
( Where possible, provide for periodic visual inspection of the heat exchanger. Visual inspection of a heat exchanger that is L an integral part of a larger component can be perfomed during l the regularly scheduled disassembly of the larger component. l- For example, a motor cooler can be visually inspected when the motcr disassembly and inspection is scheduled. I
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-, ,- s Enclosure 3' L
INFORMATION NOTICES RELATED TO FOULING PROBLEMS {j l IN SERVICE WATER SYSTEMS l
- 1. Information Notice No. 83-46: " Common-Mode Valve Failures Degrade i Surry's Recirculation Spray Subsystem," July 11, 1983
- 2. Information-Notice No. 85-24: " Failures of Protective Coatings in Pipes and Heat Exchangers " March 26, 1985
- 3. Information Notice No. 85-30: " Microbiological 1y Induced Corrosion of Containment Service Water System " April 19, 1985
- 4. Information Notice No. 86-96: " Heat Exchanger Fouling Can Cause Inadequate Operability of Service Water Systems," November 20, 1986
- 5. Information Notice No. 87-06: " Loss of Suction to Low Pressure Service Water System Pumps Resulting from Loss of Siphon,"
January 30, 1987
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asaq UNITED STATES .
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+ NUCLEAR REGULATORY COMMISSION Enclosure 3
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Cig/- June 20, 1989 TO: ALL HOLDERS OF OPERATING LICENSES OR CONSTRUCTION PERMITS FOR NUCLEAR POWER PLANTS
SUBJECT:
SERVICE WATER SYSTEM PROBLEMS AFFECTING SAFETY-PELATED EQUIPMENT (GENERICLETTERE9-XX)
Purpose:
Nuclear power plant facilities of licensees and applicants must meet the minimum requirements of the General Design Criteria (GDC) in 10 CFR Part 50, Appendix A. In particular, "GDC 44--Cooling Water" requires provision of a system (here called the service water system) "to transfer heat from struc-tures, systems, and components important to safety to an ultimate heat sink"
. (UHS). ' "GDC 45--Inspection of Cooling Water System" requires the system design "to pemit appropriate periodic inspection of important components, such as heat exchangers and piping, to casure the integrity and capability of the system." "GDC 46--Testing of Cooling Water System" requires the design "to permit appropriate periodic pressure and functional testing...."
In addition, nuclear power plant facilities of licensees and applicants must meet the minimum requirements for quality assurance in 10 CFR Part 50,
' Appendix B. In particular, Section XI, " Test Control" requires that "a test program shall be Established to assure that all testing required to demonstrate that structures, systems, and components will perform satisfactorily in service is identified and perfomed in accordance with written test procedures which incorporate the requirements and acceptance limits contained in applicable design documents."
erience and studies have led the NRC to question the Recent compliance of the se operating exp?vice water systems in the nuclear power plants of ifcensees and applicants with these GDC and quality assurance requirements. Therefore, this gbneric letter is being issued to require licensees and appli- , cants to supply infomation about their respective service water systems to assure the NRC of such compliance and to confim that the safety functions of i their respective service water systems are being met. I Backgroufid: Bulletin 21-03: The NRC staff has been studying the problems associated with service water cooling systems for a number of years. At Arkansas Nuclear One, Unit 2, on September 3,1980, the licensee shut down the plant when the NRC Resident Inspector discovered that the service water flow rate through the CONTACT: C. Verr.an Hodge, NRR 492-1169
l .. containment cooling units did not meet the technical specification requirement. The clams licensee determined (Corbicula species, athe cause tofresh non-native be extensive flowmollusk water bivalve blockage. by) Asiatic Prompted by this event and after determining that it represented a generic problem of safety significance, the NRC issued Bulletin 81-03, " Flow Blockage of Cooling Water to Safety System Components by Corbicula sp. (Asiatic Clam) and Mytilus sp. (Mussel)." The bulletin required licensees and applicants to assess macroscopic biological fouling (biofouling) problems at their respective facilities in accordance with specific actions. A careful assessment of responses to the bulletin indicated that existing and potential fouling problems are generally unique to each facility ("Closecut of IE Bulletin 81-03...", NUREG/CR-3054), but that surpris-ingly, more than half the 129 nuclear generating units active at that time were considered to have a high potential for biofouling. At that time, the activi-ties of licensees and applicants for biofouling detection and control ranged widely and, in many instances, were judged inappropriate to ensure safety system reliability. Too few of the facilities with high potential for
'biofouling had adopted effective control programs.
Information Notice 81-21: After issuance of Bulletin 81-03, one event at San Onofre Unit 1 and two events at the Brunswick station indicated that conditions not explicitly discussed in the bulletin can occur and cause loss of direct access to the UHS. These conditions include
- 1. Flow blockage by debris from shellfish other than Asiatic clams and blue mussels
- 2. Flow blockage in heat exchangers causing high pressure drops that can deform baffles and allow flow to bypass heat exchanger tubes
- 3. A change 1.n operating conditions, such as a change from power opera-tion to a lengthy outage, that permits a buildup of biofouling organisms The NRC issued Information Notice No. 81-21 to describe these events and concerns.
Generic Issue 51: By March 1982 several reports of serious fouling events, by mud, silt, corrosion products, or aquatic bivalve organisms, in open-cycle service water systems had been received. These events led to plant shutdowns, reduced power operation for repairs and modifications, and degraded modes of operation. This led the NRC to establish Generic Issue 51, " Improving the Reliability of Open-Cycle Service Water Systems." To resolve this issue, the NRC initiated a research program to compare alternative surveillance and control programs to minimize the effects of fouling on plant safety. Initial-ly, the program was restricted to a study of biofouling, but in 1987 the program was expanded to also address fouling by mud, silt, and corrosion products. This research program has recently been completed and the results have been published in " Technical findings Document for Generic Issue 51... ," NUREG/ 1 CR-5210. The NRC has concluded that the issue will be resolved when licensees i
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l and' applicants implement either the recommended surveillance and control program described below (Enclosure i) or its equivalent for the service water system at their respective facilities. Many licensees experiencing service water macroscopic biofouling problems at their plants have found that these 1 techniques will effectively prevent recurrence of such problems. The examina- 1 tion of alternative corrective action programs is documented in "Value/ Impact Analysis for Generic Issue 51...," NUREG/CR-5234. Continuing Problems: Since the advent of Generic Issue 51, a considerable number of events with safety implications for the service water system have been reported. A number of these have been described in information notices, listed in "Information Notices Related to Fouling Problems in Service Water Systems" (Enclosure 3). Several events have been reported within the past 2 years: Oconee Licensee Event Report (LER) 50-269/87-04, Rancho Seco LER I 50-312/87-36, Catawba LER 50-414/88-12, and Trojan LER 50-344/88-29. In the l fall of 1988, the NRC conducted a special announced safety system functional inspection at the Surry station to assess the operational readiness of the service water and recirculation spray systems. A number of regulatory viola-l tions were identified (NRC Inspection Reports 50-280/88-32 and 50-281/88-32). AEOD Case Study: In 1987, the Office of Analysis and Evaluation of Operational l Data (AEOD) in the NRC initiated a systematic and comprehensive review and l evaluation of service water system failures and degradations at 1*ght water reactors from 1980 to early 1987. The results of this AEOD case n udy are published in " Operating Experience Feedback Report - Service Water System failures and Degradations," NUREG-1275, Volume 3 (Enclosure 4). Of 980 operational events involving the service water system reported during this period, 276 were deemed to have potential generic safety significance. A majority (58 percent) of these events with generic significance involved system
. fouling. The fouling mechanisms included corrosion and erosion (27 percent),
biofouling (10 percent') foreign meterial and debris intrusion (10 percent), sediment deposition'(9 percent), and pipe coating failure and calcium carbonate deposition (1 percent). The second most frequently observed cause of service water system degradations and failures is personnel and procedural errors (17 percent), followed by seismic deficiencies (10 percent), single failures and other design deficien-cies (6 percent) percent), flooding (4 percent), and significant equipment failures (4 During this period,12 events involved a complete loss of service water system l function. Several of the significant causes listed above for system degrada-tion were also contributors to these 12 events involving system failure. The study identified the following actions as potential NRC requirements.
- 1. Conduct, on a regular basis, performance testing if all heat exchang-ers, which are cooled by the service water system and which are needed to perform a safety function, to verify heat exchanger heat transfer capability.
l
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- 2. Require licensees to verify that their service water systems are not vulnerable to a single failure of an active component.
- 3. Inspect, on a regular basis, important portions of the piping of the service water system for corrosion, erosion and biofouling.
4 Reduce human errors in the operation, repair and maintenance of the service water system. Recommended Actions to be taken by Addressees: On the basis of the discussion above, the NRC requests that licensees and applicants perform the following or equally effective actions to ensure that their service water systems are in compliance and will be maintained in compliance with 10 CFR Part 50, Appendix A, General Design Criteria 44, 45, and 46 and Appendix B. Section XI. If a licensee or applicant chooses a course of ! action different from the recommendations below, the licensee or applicant should document and retain in appropriate plant records a justification that the heat removal requirements of the service water system are satisfied by use of the alternative program. Because the characteristics of the service water system may be unique to each facility, the service water system is defined as the system or systems that transfer heat from safety-related structures, systems, or cnmponents to the UHS. If an intermediate system is used between the safety-related items and the system rejecting heat to the UHS, it performs the function of a service water system and is thus included in the scope of this generic letter. A closed-cycle system is defined as a part of the service water system that is not subject to significant sources of contamination, one in which water chemis-try is controlled, and one in which heat is not directly rejected to a heat
. sink. If all these conditions are not satisfied, the system is to be consid-ered an open-cycle system in regard to the specific actions required below.
(The scope of closed cooling water systems is discussed in the industrial standard " Operation and Maintenance of Nuclear Power Plants," ASME/ ANSI OM-1987, Part 2.);
)
I. For open-cycle service water systems, implement and maintain an ongoing program of surveillance and control techniques to signifi-cantly reduce the incidence of flow blockage problems due to biofouling. A program acceptable to the NRC is described in "Recom- 1 mended Program to Resolve Generic Issue 51" (Enclosure 1). It should j be noted that Enclosure 1 is provided as guidance for an acceptable i program. An equally effective program to preclude biofouling would also be acceptable. Initial activities should be completed prior to plant startup following the first refueling outago beginning 9 months or more after the date of this letter. All activ1 ties should be documented and all relevant documentation should be retatned in appropriate plant records. II. Conduct a test program to verify the heat transfer capability of all safety-related heat exchangers cooled by service water. The total test I l
program should consist of an initial test program and a periodic retest program. Both the initial test program and the periodic retest program should include heat exchangers connected to or cooled by one or more open-cycle systems as defined above. Operating experience and studies indicate that closed-cycle service water systems, such as component cooling water systems, have the potential for significant fouling as a consequence of aging related in-leakage and erosion or corrosion. The need for testing of closed-cycle system heat exchangers has not been considered necessary because of the assumed high quality of existing chemistry control programs. If the adequacy of these chemistry control programs cannot be confirmed over the total operating history of the plant or if during the conduct of the total testing program, any unexplained downward trend in heat exchanger performance is identified that cannot be remedied by maintenance of an open-cycle system, it may be necessary to selectively extend the test program and the routine inspection and maintenance program addressed in Action III, below, to the attached closed-cycle systems. A program acceptable to the NRC for heat ,xchanger testing is de-scribed in " Program for Testing Heat Transfer Capability" (Enclosure 2). It should be noted that Enclosure 2 is provided as guidance for an acceptable program. An equally effective program to ensure satisfaction of the heat removal requirements of the service water system would also be acceptable. Testing should be done with necessary and sufficient instrumentation, though the instrumentation need not be permanently installed. If a licensee or applicant decides that corrective action is needed before heat transfer testing is performed, that fact should be documented and the corrective action should be performed. To assist in the meaningful assessment of heat transfer capability, tests should be performed for the heat exchangers after any necessary corrective actions are taken to establis'h baseline data for future monitoring of heat exchanger performance. The relevant temperatures should be verified to ba! within d'esign limits. If similar or equivalent tests have not Nen performed during the past year, the initial tests should be cumpleted prior to plant startup following the first refueling outage beginning 1 9 nonths or more after the date of this letter. An example of an alternative action that would be acceptable to the i ' NRC is frequent regular maintenance of a heat exchanger in lieu o' < testing for degraded performance of the heat exchanger. This i alternative might apply to small heat exchangers, such as lube oil { coolers or pump bearing coolers or readily serviceable heat ! l exchangers located in low radiation areas of the facility. In implementing the continuing program for periodic retesting of safety-rela *td heat exchangers cooled by service water in open-cycle I systems, the L 'tial frequency of testing should be at least once each fuel cycle, but after 3 tests, licensees and applicants should ! determine the best frequency for testing to provide assurance that the equipment will perform the intended safety functions during the l C - - -
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1 1 intervals between tests and meet the requirements of GDC 44, 45, and j
- 46. The minimum final testing frequency should be once every 5 j years. A summary of the program should be documented, including the j schedule for tests, and all relevant documentation should be retained in appropriate plant records. 1 III. Ensure by establishing a routine inspection and maintenance program for open cycle service water system piping and components that corrosion, erosion, protective coating failure, silting, and biofouling can not degrade the performance of the safety-related systems supplied by service water. The maintenance program should have at least the following purposes:
A. To remove excessive accumulations of biofouling agents, corro-sion products, and silt; B. To repair defective protective coatings and corroded service water system piping and components that could adversely affect performance of their intended safety functions. This program should be established prior to plant startup following the first refueling outage beginning 9 months after the date of this letter. A description of the program and the results of these maintenance inspections should be documented. All relevant documen-tation should be retained in appropriate plant records. IV. Confirm that the service water system will perform its intended function in accordance with the licensing basis for the plant. Reconstitution of the design basis of the system is not intended. This confirmation should include a review of the ability to perform required safety functions in the event of failure of a single active component. To ensure that the as-built system is in accordance with the appropriate licensing basis documentation, this confirmation should include recent (within the past 2 years) system walk-down inspect. ions. This confirmation should be completed prior to plant startup following the first refueling outage beginning 9 months or more after the date of this letter. Results should be documented and retained in appropriate plant records. V. Confirm that maintenance practices, operating and emergency proce-dures, and training that involves the service water system are adequate to ensure that safety-related equipment cooled by the service water system will function as intended and that operators of that equipment will perform effectively. This confirmation should include recent (within the past 2 years) reviews of practices, procedures, and training modules. The intent of this action is to reduce human errors in the operation, repair, and maintenance of the tervice water system, This confirmation should be completed prior to plant startup following the first refueling outage beginning 9 months or more after the date of this letter. Results should be documented and retained in appropriate plant records.
1 s o .. Reporting Requirements: Pursuant to the provisions of Section 182a of the Atomic Energy Act of 1954, as amended, and 10 CFR 50.54 (f), each licensee and applicant shall advise the NRC whether it has established programs to implement recommendations I-V above of this generic letter or advise that it has pursued an equally effective alterna-tive course of action. Each addressee's response to this requirement for information shall be made to the NRC within 180 days of receipt o' this generic letter. Licensees and applicants shall include schedules of plans for imple-mentation of the various actions. The detailed documentation associated with this generic letter should be retained in appropriate plant records. The response shall be submitted to the appropriate regional administrator under oath and affirmation under the provisions of Section 182a, Atomic Energy Act of 1954, as amended and 10 CFR 50.54 (f). In addition, the original cover letter and a copy of any attachment shall be transmitted to the U.S. Nuclear Regu-latory Commissicn, Document Control Desk, Washington DC 20555, for reproduction and distribution.
~
In addition to the 180-day response, each licensee and applicant shall confirm to the NRC that all the recommended actions or their justified alternatives have been implemented within 30 days of such implementation. This response need only be a single response to indicate that all initial tests or activities have been completed and that continuing programs have been established. This request is ccvered by the Office of Management and Budget Clearance Number 3150-0011, which expires December 31, 1989. The estimated average burden is 1000 man-hours per addressee response, including assessing the actions to be taken, preparing the necessary plans, and preparing the 180-day response. This estimated average burden pertains only to these identified response-related matters and does not include the time for actual implementation of the recom-mended actions. Emments on the accuracy of this estimate and suggestions to reduce the burden may be directed to the Office of Management and Budget, Reports Management, Room 3208, New Executive Office Building, Washington DC 20503 and to the U.S. Nuclear Regulatory Commission, Records and Reports Management Branch Office of Administration and Resources Management, Washing-ton DC 20555. 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. Addressee time necessary to perform the requested confirmation and any needed follow-up actions.
- 2. Addressee time necessary to prepare requested documentation.
1 I 1 1 _ _ _ _ - - l
; g ., .. s .
e If there are any questions regarding this letter, please contact the regional' administrator of the appropriate NRC regional office or your project manager in this office. Sincerely, James G. Partlow Associate Director for Projects Office of Nuclear Reactor Regulation
Enclosures:
- 1. " Recommended Program to Resolve Generic !ssue 51"
- 2. " Program for Testing Heat Transfer Capability"
- 3. "Information Notices Related to Fouling Problems in Service Water Systems"
, 4. " Service Water System Failures and Degradations in Light Water Reactors ," NUREG-1275, Volume-3 l
l- !
l . , s
+
Enclosure 1 RECOMMENDED PROGRAM TO RESOLVE GENERIC ISSUE 51 This enclosure describes a program acceptable to the NRC for meeting the ' objectives of the requested Action I in the proposed generic letter. Both Action I and this enclosure are based upon the recommendations described in
" Technical Findings Document for Generic Issue 51: Improving the Reliability of Open-Cycle Service-Water Systems," NUREG/CR-5210, August 1988, and "Value/ Impact Analysis for Generic Issue 51: Improving the Reliability of Open-Cycle Service-Water Systems," NUREG/CR-5234, February 1989. The NRC has concluded that Generie Issue 51 will be resolved when licensees and applicants implement either the recommended surveillance and control program addressed in this enclosure or an equally effective alternative course of action to satisfy the heat removal requirements of the service water system.
Water Source Surveillance Control Type Technioues Technioues Marine or Estuarine A B and C (brackish) or Freshwater with clams Freshwater without clams A and D B and C t A. The intake structure should be visually inspected, once per refueling cycle, for macroscopic biological fouling organisms (for example, blue mussels at marine plants, American oysters at estuarine plants, and
- Asiatic clams at freshwater plants), sediment, and corrosion. Inspections should be performed either by SCUBA divers, or by dewatering the intake structure, or by other comparable methods. Any fouling accumulations should be removed.
B. The service water system should be continuously (for example, during spawning) chlorinated (or equally effectively treated with another l biocide) whenever the potential for a macroscopic biological fouling I species exists (for example, blue mussels at marine plants, American oysters at estuarine plants, and Asiatic clams at freshwater plants). Chlorination or equally effective treatment is included for freshwater plants without clams because it can help prevent microbiologically influ-enced corrosion. However, the chlorination (or equally effective) treatment need not be as stringent for plants where the potential for macroscopic biological fouling species does not exist compared to those plants where it does. Precautions should be taken to obey federal, state, and local environmental regulations regarding the use of biocides. C. Redundant and inOequently used cooling loops should be flushed and flow tested periodically at the maximum design flow to ensure that they are not fouled or cloggeo. Other components in the service water system should be tested on a regu'ar schedule to ensure that they are not fouled or 1 1
2 !- clogged. Service water cooling loops should be filled with chlorinated or equivalently treated water before layup. Systems that use raw service water as a source, such as some fire protection systems, should also be chlorinated or equally effectively treated before layup to help prevent microbiologically influenced corrosion. Precautions should be taken to obey federal, state, and local environmental regulations regarding the use l of biocides. D. Samples of water and substrate should be collected annually to determine l if Asiatic clams have populated the water source. Water and substrate sampling is only necessary at freshw6ter plants that have not previously detected the presence of Asiatic clams in their source water bodies. If Asiatic clams are detected, utilities may discontinue this sampling activity if desired, and the chlorination (or equally effective) treatment program should be modified to be in agreement with paragraph B, above. i l a 4
..o_v Enclosure 2 PROGRAM FOR TESTING HEAT TRANSFER CAPABILITY This enclosure describes a program acceptable to the NRC for neeting the objectives of the requested Action II in the proposed generic letter. Both Action II and this enclosure are based in part on " Operating Experience Feed-back Report - Service Water System Failures and Degradations," NUREG-1275, Volume 3 and " Technical Findings Document for Generic Issue 51: Improving the Reliability of Open Cycle Service Water Systems," NUREG/CR-5210, March 1988. This enclosure reflects continuing operational problems, inspection reports, and industry standards (" Operation and Maintenance of Nuclear Power Plants " ASME/ ANSI OM-1987, Part 2.) The NRC requests licensees and applicants to implement either the steps addressed in this enclosure or an equally effective alternative course of action to satisfy the heat removal requirements of the service water system. Both the initial test program and the periodic retest program should include all safety-related heat exchangers connected to or cooled by one or more open-cycle service water systems. A closed-cycle system is defined as a part of the service water system that is not subject to significant sources of-contamination, one in which water chemistry is controlled, and one in which heat is not directly rejected to a heat sink. (The scope of closed cooling water systems is discussed in the industrial standard, " Operation and Maintenance of Nuclear Power Plants," ASME/ ANSI OM-1987, Part 2.) If during the conduct of the total testing program any unexplained downward trend in heat exchanger performance is identified that cannot be remedied by maintenance of an opencycle system, it may be necessary to selectively extend the test program to the attached closed-cycle system. An example of an alternative action that would be acceptable to the NRC is frequent regular maintenance of a heat exchanger in lieu of testing for degraded performance,of the heat exchanger. This alternative might apply to small heat exchangers, such as lube oil coolers or pump bearing coolers or readily serviceable heat exchangers located in low radiation areas of the facility. In implementing the continuing program for periodic testing, the initial frequency of testing should be at least once each fuel cycle. After 3 tests, licensees and applicants should determine the best frequency for testing to provide reasonable assurance that the equipment will perform the intended safety functions during the intervals between tests. The minimum final testing frequency should not be less than once every 5 years. Instrumentation neces- ; sary to accomplish the testing should be provided but this does not have to be ' permanently installed. If a licensee or applicant decides that corrective action is needed before heat transfer testing is performed, that fact should be documented and the corrective action snould be performed. To assist in the meaningful assessment of heat transfer capability, tests snould be performed for the heat exchangers after any necessary corrective actions are taken to establish baseline data for future monitoring of heat exchanger performance. 1
e, t. o s,* I. For all heat exchangers Monitor and record cooling water flow and inlet and outlet tempera-l tures for all affected heat exchangers during the modes of operation l in which cooling water is flowing through the heat exchanger. For each measurement, verify that the cooling water temperatures and l flows are within design limits for the conditions of the measurement. The test results from periodic testing should be trended to ensure that flow blockage or excessive fouling accumulation does not exist. II. In addition to the considerations for all heat exchangers in item I, for water-to-water heat exchangers A. Perform functional testing with the heat exchanger operating, if practical, at its design heat removal rate to verify its capa-bilities. Temperature and flow compensation should be made in the calculations to adjust the results to the design conditions. Trend the results, as explained above, to monitor degradation. An example of this type of heat exchanger would be that for I cooling a diesel generator. Engine jacket water flow and temperature and service water flow and temperature could be monitored and trended during the diesel generator surveillance l testing. ! B. If it is not practical to test the heat exchanger at the design heat removal rate, then trend test results for the heat exchang-er efficiency or the overall heat transfer coefficient. Verify that heat removal would be adequate for the system operating with the most limiting combination of flow and temperature. III. In addition to the considerations for all heat exchangers in Item I, for air-to-water heat exchangers A. Perfo'rm efficiency testing (for example, in conjunction with surveillance testing) with the heat exchanger operating under the maximum heat load that can be obtained practically. Test results should be corrected for the off-design conditions. Design heat removal capacity should be verified. Results should be trended, as explained above, to identify any degraded equipment. B. If it is not possible to test the 1 eat exchanger to provide statistically significant results (for example, if error in the measurement exceeds the value of the parameter being measured), then I. Trend test results for both the air and water flow rates in the heat exchanger
- 2. Perform visual inspections, where possible, of both the air and water sides of the heat exchanger to ensure cleanliness of the heat exchanger
g g,:c l 1 IV. In addition to the considerations for all heat exchangers in Item I, fo'r types of heat exchangers other than water-to-water or air-to-water heat exchangers (for example, penetration coolers, oil coolers, and motor coolers) A. If plant conditions allow testing at design heat removal condi-tions, verify that the heat exchanger performs its intended y functions. Trend the test results, as explained above, to I monitor degradation. ! B. If testing at design conditions is not possible, then provide j for extrapolation of test data to design conditions. The heat exchanger efficiency or the overall heat transfer coefficient of the heat exchanger should be determined whenever possible. Where possible, provide for periodic visual inspection of the heat exchanger. Visual inspection of a heat exchanger that is an integral part of a larger component can be performed during the
, regularly scheduled disassembly of the larger component. For example, a motor cooler can be visually inspected when the motor disassembly and inspection is scheduled.
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e, - Enclosure 3 INFORMATION NOTICES RELATED TO FOULING PROBLEMS i IN SERVICE WATER SYSTEMS 1
- 1. .Information Notice No. 83-46: " Common-Mode Valve Failures Degrade Surry's Recirculation Spray Subsystem," July 11, 1983
- 2. Information Notice No. 85-24: " Failures of Protective Coatings in Pipes and Heat Exchangers," March 26, 1985
- 3. Information Notice No. 85-30: " Microbiological 1y Induced Corrosion 4 of Containment Service Water System," April 19, 1985 l
- 4. Information Notice No. 86-96: " Heat Exchanger Fouling Can Cause
. Inadequate Operability of Service Water Systems," November 20, 1986
- 5. Information Notice No. 87-06: " Loss of Suction to Low Pressure Service Water System Pumps Resulting from Loss of Siphon,"
, January 30, 1987 I
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