ML20059K367

Informs of Revised Commitments Re Crud Induced Localized Corrosion Related to Fuel Cladding Failures.Deep Bed Demineralizers Installation Activities Will Be Performed in Unit 1 Subsequent to Third Refueling Outage

ML20059K367
Person / Time
Site:	Limerick
Issue date:	09/14/1990
From:	Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9009210272
Download: ML20059K367 (3)

Text

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PHILADELPHIA ELECTRIC COMPANY NUCLEAR GROUP HEADQUARTERS 955-65 CHESTERB'tOOK BLVD.

WAYNE, PA 19087 5691 September 14, 1990 (sis) sao sooo Docket Nos. 50-352 50-353 License Nos. NPF-39 NPF-85 i

k U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555

SUBJECT:

Limerick Generating Station, Units 1 and 2 Revised Comaltaents With Regard to the Crud Induced Localized Corrosion Related k 4 Fuel Cladding Failures at Unit 1

Dear Sir:

This letter is to inform the NRC of revised cosaiteents with regard to >

the crud induced localized corrosion (CILC) related fuel cladding failures which occurred during the second cycle of Limerick Generating Station (LGS), Unit 1 operation. By letter dated April 3, 1989, we provided the NRC with the results of our evaluation of the CILC related fuel cladding failures. That letter also provided the corrective actions and preventive measures to be implemented to address the causal factors of the failures. With respect to the water chemistry control program at both Unit 1 and Unit 2, we couaitted to install deep bed desineralizers to minimize copper input to the reactor water (one of the identified causal fartors). Section 10.4.6 of NUREG-0991 " Safety Evaluation Report Related to th! Operation of Limerick Generating Station Units 1 and 2 "

Supplement No. 8. dated June 1989, states that our comaltaent is to install the deep bed desineraliuers: 1) no later than the next (third) refueling outage for LGS, Unit 1, currer.tly scheduled to begin September 8,1990, and 2) at the first refueling outage for LGS, Unit 2, currently scheduled to begin March 23, 1991.

Completion of both Unit 1 and Unit 2 deep bed desineralizer installations has been delayed due to the extended engineering effort required to incorporate vendor-specific desineralizer design features, and due to 1990 corporate budget reductions. The LGS Unit 1 deep bed desineralizer installation activities are progressing with plant outage-related work scheduled to be perfor1eed during the third refueling outage during ths fall of 1990. The majority of the installation activities (i.e., non-outage related) will be performed subsequent to the third refueling outage with an expected service dtte for the LGS, Unit 1 deep bed deelneralizers of March, 1992. The Unit 2 deep bed CL jf00/

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Document Control Desk Siptember 14, 1990-Page 2-

'denineralizer installation activities are presently on hold with the exception _ -

of plant ~ outage-related work which is scheduled to be, performed during the first Unit 2 refueling outage in the spring of 1991.- The eventual installation of the:

1 LGS Unit 2 deep. bed demineralizers is dependent on' future corporate budget 4 allocations. However.-the earliest expected service date for the LGS. Unit'2 N

. deep bed demineralizers could be October, 1992.

Additionally..in our April-3. 1989 letter. we' committed to control thi

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'feedwater copper concentration during plant operation ~ andlin particular, during.

power ascension with a goal of less than or equal to 0.2 ppb on the basis that 5 this goal.would be re-evaluated with respect to plant operating experience.. 1 Actual; plant operating experience with the existing filter _deatneralizers and-- 'q optimal filter desineralizer performance indicates thet aimore realistic ~ andc  ;

achievable goal is less than~or equal to 0.3 ppb. LThis'new goal is supported by . l the results of a risk analysis performed to assess the-impact of increased- l feedwater copper concentrations which shows that an incremental increase from 4 0.2 ppb to 0.3 ppb copper-. concentration in the reactor feedwater would produce:a ';

mintaal increase in the risk of ClLC, assuming chemical? intrusions'to the'  ;

reactor water (i.e., a causal factor of CILC) are avoided or adequately counteracted. Therefore, as part of the water chemistry control program, a  !

revised goal of.less than or. equal to 0.3 ppb feedwater copper concentration  ;

during plant' operation has been established. Unit l' typically operates with a i feedwater copper concentration between 0.25 and 0.3 ppb..while Unit 2 typically operates with a feedwater copper concentration between 0.2 and 0.25 ppb. 'The 90al of 0.3 ppb feedwater copper concentration will be maintained for each unit uni.il the deep bed demineralizers are installed and'placed in service.. l Also, in our April-3. 1989~1etter..as part of the chemistry action plan )

in response to the CILC related fuel cladding failures, we' committed to perform on-line monitoring for total organic carbon (TOC) concentrations'in the Unit 1-  ;

final feedwater in addition to the existing monitoring of' TOC concentrations at  ;

j other plant process locations. During restari, cf Ur.ic l' fron;the second {

refueling _o..: age, the concentration of TOC in the.fira1 feedwater was monitored on-line. Values of 50 to 200 ppb of TOC were detected duringLlong path flushing )

prior to Unit 1 startup.. Long path flushing consists'of recirculating the feedwater to the condenser hotwell rather than directing 1the feedwater to the reactor vessel. Following completion of the long pathiflushings. the final '

feedwater TOC concentrations returned to less than 10 ppb (1 e., the lowest i

level of detection capability of the TOC analyzer). Evaluation of the on-line-TOC concentration data- for the:feedwater over the third cycle of Unit 1 operation indicates that less than detectable levels ofcTOC'were maintained.

The results of the on-line TOC monitoring of-the final feedwater indicate that this type of monitoring is unwarranted. ' Additionally this type ofmonitoringisnotincludedinElectricPowerResearchInstitute:(EPRI)orthe InstituteofNuclearPowerOperations(INPO)guidelinesonBoilingWaterReactor  !

(BWR) chemistry. Therefore, we intend to stop routine monitoring of final -l feedwater TOC concentrations as of the end of the. third cycle of LGS. Unit 1 operation and focus our attention and resources on the control'of recycled radwaste water input to the condensate storage tank (CST). 1 1

,.,,q Document Control Desk Srptember 14,'1990 Page 3 In our April 3. 1989 letter, we identified water chemistry transients which occurred early-in the second cycle of LGS, Unit 1 operation as a causal factor-for the CILC related fuel cladding failures. One such transient involved the intrusion of electro-hydraulic control (EHC) fluid into the reactor coolant system by way of transfer of re':ycled radwaste water to the CST. The EHC fluid-entered the radwaste system as a result-of EHC systen leakage into floor drain sumps. As part of the effort tc control recycled radwaste water input to the ,

CST, station personnel.have developed and implemented an aggressive program to j monitor for EHC fluid.at the.radwaste sample tanks prior to transfer of the j recycled radwaste water totthe CST. This ensures that the quality of recycled  ;

radweste we.ter is acceptable for use in the reactor coolant system and helps to j eliminate EHC fluid intrusions into the reactor coolant system. '

l If you have any questions, or require additior.a1 information, please contact us.

i Very truly yours, }

~

.h k U, ) .

G. A. Hunger,' Jr.

Manager 1 Licensing Section- _.

Nuclear Engineering-and Services  !

cc: T. T. Martin, Administrator, Region I USNRC T. J. Kenny, USNRC Senior Resident Inspector, LGS-1 4

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