ML20006B278

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LER 89-017-00:on 890718,determined That Isolation for Postulated RWCU Blowdown Line Breaks in Piping Cold Rooms Was 80 S,Causing Plant to Operate in Unanalyzed Condition. Tech Spec Change Request Will Be submitted.W/900116 Ltr
ML20006B278
Person / Time
Site: Grand Gulf Entergy icon.png
Issue date: 01/16/1990
From: Byrd R, Cottle W
SYSTEM ENERGY RESOURCES, INC.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
AECM-90-0013, LER-89-017, NUDOCS 9002010231
Download: ML20006B278 (5)
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mesnuums,mur -/ w e .smsum esc m  : 7 4-vee Prescent January- 16, 1990 Nuclear CYvotons U.S. Nuclear Regulatory Commission [Rg VED Mail Station F1-137 Washington, D.C. 20555 2 1990 Attention: Document Control' Desk + D e ** Gentlemen:

SUBJECT:

d Gulf Nucl ation Docket No. 50-416 License'No. NPF-29 RWCU'Line Break Analysis Does Not Reflect Changes-In Isolation Provisions. AECM-90/0013 LER 89-017-00 Attached is Licensee Event Report (LER) 89-017-00 which is a final ' report. Yours truly, 

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d WTC:cg Attachment cc: Mr. D. C. Hintz (w/a) Mr. T. H. Cloninger (w/a) Mr. R. B. McGehee (w/a) Mr. N. S. Reynolds (w/a) Mr. H. L. Thomas (w/o) Mr. H. O. Christensen (w/a) , , c Mr. Stewart D. Ebneter (w/a)~  ; , 4 Regional Administrator 4$O' U.S. Nuclear Regulatory Commission "8' Region II og 101 Marietta St., N.W., Suite 2900 mo Atlanta, Georgia 30323 g MO Mr. L. L. Kintner, Project Manager (w/a) , 

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l 7ACILITY NAME til DOCMET NuMSER 43) PAug (33 Crand Gulf Nuclear Station - Unit 1 015 l 0 l 0 l 01411 16 1 l0Fl 014 TITLE tot RWCU Line Break Analysis Does Not Reflect Changes in Isolation Provisions EVSNT DATE (S) LER NMER 104 R4 PORT DATE (7) OTMER FACILITIES INVOLVED (4) 88 '4 DQCKET NuMSERISI MONTH DAY YEAR YEAR , ",'[ MONTM DAY YEAR F AClwlTV NAMES NA 0l5l0l0l0j ;; 0 \7 1l 8 89 8l9 

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Isolation for postulated Reactor Water Cleanup (RWCU) line breaks is provided by area temperature and delta-flow signals in areas containing " hot piping," and delta-flow signals in areas containing " cold piping." The area temperature system isolates within 60 seconds, whereas the delta-flow system isolates in approximately 80 seconds. The delta-flow system provides generally greater sensitivity and response to smaller RWCU breaks / leaks, but slower isolation for large breaks. Prior to 1984 somo " cold piping" roomr,had area temperature as well as delta-flow isolation. In 1984, a change was made to delete the temperature isolation feature in these areas from the Technical Specifications. In 1985 a Design Change was implemented to disable the temperature isolation featurea in these areas. At this time, a judgment was apparently made that no UFSAR reanalysis was necessary. System Energy identified in July 1989 that reanalysis of this event using the longer blowdown time should be performed to update the UFSAR. The results of the reanalysis confirmed that the consequences of previously evaluated accidents were not increased. Therefore, the plant was in an unanalyzed condition which did not significantly compromise plant safety. LER89017/SCMPFLR - 1

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                 'A. Condition Reported' The existing FSAR analysis for the limiting Reactor Wat're Cleanup (RWCU) System (EIIS system' code:CE) piping fallures'is based on leak
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detection and system isolation at no J moresthan 60.-seconds,following the" postulated failure. This isolation time was based on-isolation 1 signals 1 from area temperature monitoring instrumentation. .However, the existing 

                        ,RWCU isolation circuit (EIIS system codeiJM) contains no room temperature or differential- temperature isolation:

signals for rooms normally having RWCU piping with water at temperatures- j of less than 120 F. The actual system isolation for piping failures in these " cold" piping rooms is provided by differential flow- -{- instrumentation.- An increased time delay due to' differences in 

                         . instrument function times results.'in a! postulated blowdown in;these                                        y rooms of approximately 80 seconds, which was not1 accounted for in the.                              ~

existing FSAR analysis. A new' evaluation which' assessed the11mpact of j the longer blowdown duration, concluded that the consequences of;  ; previously evaluated accidents were not increased. -System Energy Resources, Inc. (SERI) is providing this report as'a-Special Report in accordance with Technical-Specification 6.9.2. ' a' 1 B. Initial Conditions The condition was identified on July, 18, 1989 while'. operating at 1 approximately 100 percent power.  ! l C. Description of Occurrence Various methods of leak detection and system isolation are provided for) postulated piping failures in the RWCU system. pipe break zones are monitored by at least one of.the following methods: .1) high  ; differential flow between the system inlet flow rate and the sum of the  ;; system discharge flow rates, and 2) high temperature and-high 

                       -differential temperature inside the rooms containing RWCU process                                                j piping. The GGNS low power Operating License (Technical Specification                                           1 Table 3.3.2-2) required RWCU isolation by high temperature and high^                                             l differential temperature signals for the following areas:                                                        1
1. RWCU Heat Exchanger Room '
2. RWCU Pump Room
3. RWCU Valve Nost Room
4. RWCU Demineralizer Rooms
5. RWCU Receiving Tank Room
6. RWCU Demineralizer Valve Room (also designated the Holding pump Room) ,

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  • E. ' Supplemental Corrective Actions-
                            'A new line break analysis was performed.by System Energy. JThe.' analysis determined that the new isolation time of~80 seconds,-based only'on the differential flow trip, is acceptable since the increased consequences"                                       .]

are still bounded by existing design limits. The newJan'alysisLwill_be( reflected in Rev. 5 of the UFSAR which  :]j will be issued by December, 1990- ' A 10CFR50.59 safety evaluation was performed which determined that the ld existing conditions did not involve any unreviewed safety _ questions.  ; This evaluation.was reviewed and approved by the pSRC on November 21,  :! 1989. 

                                                                                                                                            }l   -i System Energy has implemented a nuIrber of improvements in the safety.                                        'i evaluation process as documented in a' meeting summary report from Mr. L.                                     d L. Kintner to SERI on January 25, 1989.(MAEC 89/0021). !A direct' benefit.

of these improvements is a heightened awareness:and sensitivityLto 

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maintaining UFSAR analyses corrected and updated.' We-believe this;  ; heightened awareness contributed to=SERI's self-identification of-this' i issue. No further actions are considered necessary. Since the temperature monitoring instrumentation is installed-in_the actual location needed (the heat exchanger valve nest area) and'is;bei covered by the existing TechnicaliSpecifications", SERI-is pursuing;a-normal Technical Specification Change Request to clarify the current wording. q F. Safety Assessment + The new RWCU line break analysis assessed the impact'of the' longer. . , I blowdown duration in the applicable areas for pressure and differential pressure, temperature, flooding, and offsite radiation dosos. The  : analysis demonstrated that the required design functions are'still met and the consequences of previously evaluated accidents are not ) increased. jl h d 1 

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                     . w.s -. m-w mw e 2mw nn ,                                                                                           i On June 22, 1984, SERI requested the deletion of the requirement for temperature isolation signals for rooms 4, 5, and 6 above, since the rooms contained " cold process fluid" (e.g. less than 120F). Detection of leakage downstream of the RWCU heat exchanger was not practical with conventional' monitoring instruments because of the relatively low temperature of the                                          ,

reactor coolant in these rooms. Leak detection was provided by the existing. j differential flow monitoring.  ! 

                                                                                                                                         'l On August'31, 1984, the USNRC approved the deletion of these items by the                                         !

issuance of Nnendment 13 to NPF-13. .In March-1985,.a design change was. implemented to disable the isolation function of items 4, 5, and,6. leaving only the Control Room alarms functional. The need to revise the FSAR analysis was identified and documented by a Quality Deficiency Report on July 18, 1989 during an engineering evaluation  ; of RWCU leak detection methods'and alternatives. This evaluation was ' initiated as a result of spurious differential flow isolations-(Refer to LER 88-014-01 and LER 89-007-00). This QDR also identified a lack of temperature instrumentation in the RWCU Valve Nest Room which was included in the FSAR analysis for RWCU line breaks. The revised FSAR analysis addressed this room as well. j I D. Apparent Cause The Technical Specification change was requested during the Technical Specification Review Program (TSRp) conducted in 1984. It was determined in 1984 that since these equipment rooms normally contained only " cold" RWCU  ! process fluid, detection of a 25 gpm leak as required by. General Electric  ! design specifications on leak detection would not be practical using i conventional high temperatur'e detection methods. Removal of the requirements was justified at the time by reliance on the differential flow isolation instrumentation to detect and isolate RWCU leakage in these rooms. It appears that a judgment was made that line breaks in the " cold" RWCU 3 equipment areas monitored by delta-flow instrumentation alone were still enveloped by existing FSAR analyses. In addition, a lack of precision in describing the location of temperature instruments resulted in the current Technical Specification discrepancy. Specifically, that instrumentation described as being located in the RWCU Valve Nest Room (1A443, also termed the RWCU Valve Access Area Room) is actually located in the valve nest area of the RWCU Heat Exchanger Room (1A414). The 1984 Technical Specification change described the instrumentation requiremento for both areas based on  ! the common location of all the instruments in room 1A414. However, this ambiguity in the Technical Specifications has not resulted in inadequate system surveillances as the temperature instrumentation in the RWCU heat , exchanger valve nest area has been included in the appropriate surveillance and calibration procedures. > pc,oau ssaALER89017/SCMPFLR - 3 i omi i 

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