ML20056B406

Submits Supplemental Response to Generic Ltr 88-14 Re Design & Verification of Instrument Air Sys.Mfg Purchase Specs & Vendor Manuals Reviewed for Air Quality Requirements

ML20056B406
Person / Time
Site:	LaSalle
Issue date:	08/21/1990
From:	Taylor D COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-88-14, NUDOCS 9008280246
Download: ML20056B406 (4)

Text

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Grove. lilinois 60515 August 21, 1990 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Hashington, D.C. 20555

Subject:

LaSalle County Station Units 1 and 2 Supplemental Response to NRC Generic Letter 88-14 NRC Docket Nos. 50-373/374

References:

(a) NRC Generic Letter 88-14, dated August 8, 1988.

(b) H. Richter letter to U.S. NRC, dated February 6, 1989.

Dear Sir:

Reference (a) requested that all holders of operating licenses or construction permits for nuclear power reactors review NUREG-1275, Volume 2, and perform a design and operations verification of the instrument air system. Reference (b), which presented Commonwealth Edison Company's (Ceco)  ;

initial response to Reference (a), indicated that a response would be provided '

i upon completion of the design verification for LaSalle County Station. This letter presents the results of the design verification for LaSalle County Station which was completed in 1989.

As indicated in Reference (a), Ceco determined that the design verification should address the following:

- identify safety-related systems and equipment which use instrument air and/or nitrogen,

- review the manufacturer's air quality recommendations for the safety related equipment identified, 3

- evaluate the design basis and failure modes, of the identified '

safety-related equipment, for technical adequacy,

- review past and present testing (i.e., pre-operational, startup, inservice testing program, surveillances, etc.) to ensure proper performance of safety-related equipment upon loss of air,  !

- evaluate accumulator sizing to assure safety-related equipment will l l operate as designed, ,

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- review safety-related air accumulator check valve applications and l i tests verifying design adequacy, I - review air quality requirements (FSAR. Regulatory Guides, vendor I

input).

- review the instrument air anomalies listed in NUREG-1275, Volume 2 for applicability,

- assess the potential for common mode failures (i.e., due to poor air p

quality),

l assess the failure of non-safety-related or reliability related systems on the performance of safety-related equipment using instrument air, and review the Braidwood Station loss of instrument air event for ap@ %h{lj ty.

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t Edison was assisted in ti- design verification by the original design architect engineer for LaSalle S+ u on. The actions taken in addressing the l objectives of the design verification are summarized below.

- To facilitate the design verification, safety-related systems and equipment which use instrument air and/or nitrogen were identified and listed in a component matrix.

- Manufacturer purchase specifications and vendct manuals were reviewed for air quality requirements. No requirements were found which conflict with the LaSalle FSAR. Manufacturers were also contacted to obtain air quality recommendations of safety-related components they supplied to LaSalle Station. The manufacturers that responded reiterated a " general" requirement of clean, dry, oil-free air.

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- The design basis and failure modes of safety-related equipment were evaluated for technical adequacy. Current air-operated safety-related component failure positions were verified that they l are correct for assuring required safety functions.

! - Pre-operational tests, the Inservice Tetting (IST) Program, and various operational surveillances were reviewed and evaluated to ensure safety-related equipment will perform as expected upon loss of air and in accordance with all design-basis events. Based on tests .

reviewed, no abnormalities were found. All equipment was found to be i ac'equately tested.

Safety-related accumulator sizings were re-vetified to be correct for l their intended functions. Volumetric capacities were found to be adequate to meet design functions. No improperly sized accumulators l were found.

- Safety-related air accumulator check valve applications and seating material selection have been re-verified. Check valve tests verifying design adequacy were reviewed and no abnormalities were l discovered. All safety-related check valves were found to be adequately tetted. j

- The LaSalle Statior FSAR specifies " oil-free, filtered, and dried air" for the station air and drywell pneumatic systems. The station is committed to regulatory Guide 1.80. This guide requires ,

pre-operational testing of instrument air systems to " meet l cleanliness rer,utrements with respect to oil, water, and particulate i matter contal'.ed in the product air"

- LaSalle's instrument air is dried and filtered to remove 981, of all particles 0.07 microns and larger.

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1 The 39 cases of instrument air anomalies described in NUREG 1275 i (Volume 2) were reviewed for applicability to LaSalle Station. No deficiencies were discovered which required specific corrective actions.

- Potential common mode failures, such as those described in NUREG 1275 were evaluated for appitcability to LaSalle Station. The failure of safety-related valves due to poor air quality was investigated. The potential for such a failure does exist but is not likely to occur '

because the station dries and filters its instrument air. The station instrument air quality monitoring program (which was implemented in 1989 as indicated in Reference (b)) and the preventive maintenance program ensure that consistently high Instrument air quality is maintained. The ongoing inservice testing program and pre-operational testing provide the assurance that safety-related air users will fall safe during design basis events.

- The potential for failures in non-safety-related or reliability-related systems affecting the operation of safety-related components was reviewed. Three (3) items associated with the concerb addressed in Information Notice 88-24 (Failures of Air-Operated Valves affecting Safety-Related Systems) have been identified.

The review indicated that a safety-related Instrument Air (IA) solenoid pilot valve, for a Unit 2 Reactor Core Isolation Cooling (RCIC) drain valve to the main condenser (2E51-F025),

should be replaced with a valve model having a higher related maximum operating pressure differential (HOPD). If the upstream non-safety-related air regulator were to fall, then the solenoid valve HOPD could be exceeded which could potentially cause the RCIC drain valve to fall open. The solenoid pilot valve was replaced during the Spring 1990 refueling outage.

It was also determined that the non-safety-related Drywell Pneumatic (IN) system 175/100 psig regulators could potentially fall in a manner which would increase regulator downstream pressure to 175 psig. If this failure were to occur, then the M0PD could be exceeded on the safet',-related solenoid pilot valves which supply nitrogen / air to the inboard Main Steam Isolation Valves (HSIVs). This, in turn, could potentially cause the inboard HSIVs to fall apen. These non-safety-related regulators were replaced with eafety-related regulators during the fall 1989 and Spring 1990 refueling outages.

An evaluation was performed to determine the effect of regulator failure on the operability of the inboard HSIVs. From this evaluation, additional pressure regulators were identified, which required replacement (5 for each unit). All requiret Unit 2 regulators were replaced during the Spring 1990 refueling outage and all required Unit I will be replaced during the Spring 1991 refueling outage, l

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- The dual unit shutdown at Braidwood Station on November 15, 1988, was reviewed for applicability to LaSalle County Station. The station uses a common IA ring header design similar to that used at Braidwood Station. If the highly unilkely passive failure of a large IA header were to occur at LaSalle, both units would scram and safety-related equipment would perform its design function. The results of the review Indicated no design safety deficiencies which required the initiation of corrective actions.

The results of the instrument air design verification provides assurance that LaSalle Station is operating within its design basis analysis.

As indicated in Reference (b), an instrument air quality monitoring program was implemented on a quarterly basis at LaSalle Station. This program was found to be effective in monitoring and maintaining air quality. It was determined that this program should be continued on a quarterly basis. ,

1 Reference (b) also indicated that a system by system review of the adequacy of operating procedures in response to a loss of instrument air would be conducted and required procedure revisions would be in place by April 1,.  !

1990. The completion of those procedure revisions is now expected by December l 31, 1990.

This correspondence completes the reporting requirements for Generic Letter 88-14 for LaSa110 Station.

Please address any questions concerning this response to this office.

Respectfully, Darrell Taylor Nuclear Licensing Administrator

/Imw/ID166 cc: A.B. Davis Resident Inspector - LSCS R. Pulsifer-NRR .- ,

" OFFICI AL SE AL " ll Subscribed and Sworn to LYNN M. WLODARSKllbl NOTARY PUBuc. STATE OF ILUNOIS befor me this M I day M

,19de Y COMMISSi0h '" ~~ EXPIRES 6/25/94j of 4d O

wJk.lbbdY Notary Public