ML20137G661

Application for Amends to Licenses NPF-39 & NPF-85,deleting Drywell & Suppression Chamber Purge Sys Operational Time Limit & Adding SR to Ensure Purge Sys Large Supply & Exhaust Valves Are Closed as Required

ML20137G661
Person / Time
Site:	Limerick
Issue date:	03/24/1997
From:	Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20137G665	List: ML20137G661 ML20137G675
References
NUDOCS 9704010460
Download: ML20137G661 (8)

Text

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.. , ctation support o.p.et nt 4 10 CFR 50.90

= sir PECO NUCLEAR reco % c -

A Unit of PECO Energy Np7$7**

March 24,1997 Docket Nos. 50-352 50-353

, t License Nos. NPF-39 NPF-85 t

l U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Subject:

Limerick Generating Station, Units 1 and 2 Technical Specifications Change Request No.96-234 Deletion of Containment Purge Operational Time Limit Gentlemen:

PECO Energy Company is submitting Technical Specifications (TS) Change Request No. 96 l 0, in accordance with 10 CFR 50.90, requesting a change to TS (i.e., Appendix A) of operating j License Nos. NPF-39 and NPF-85 for Limerick Generating Station (LGS), Units 1 and 2.

1 The proposed changes will delete the Drywell and Suppression Chamber Purge System )

operational time limit, and add a surveillance requirement to ensure the purge system large supply and exhaust valves are closed as required. These changes also satisfy a PECO Energy Company commitment identified in a NRC Safety Evaluation which supported NRC approval of l

Unit 1 amendment 115, and Unit 2 amendment 77 by letter dated March 29,1996.

Information Supporting this TS Change Request is contained in Attachment 1 to this letter, and copies of the ' marked-up" Technical Specifications pages are contained in Attachment 2. This information is being submitted under affirmation, and the required affidavit is enclosed.

We request that if approved, the changes be issued by October 1,1997, and become effective within 30 days of issuance.

l If you have any questions, please do not hesitate to contact us. \ {

Very truly yours, 9704010460 970324' PDR l

l P ADOCK 05000352 <

PDR

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G. A. Hunger, .

Director - Licensing Attachments M.N E N

. Enclosure cc: H. J. Miller, Administrator, Region I, USNRC (w/ attachment, enclosure)

N. S. Perry, USNRC Senior Resident inspector, LGS (w/ attachment, enclosure) 030063 R. R. Janati, PA Bureau of Radiation Protection (w/ attachment, enclosure) l

i J P COMMONWEALTH OF PENNSYLVANIA  :

ss COUNTY OF CHESTER  :  !

l D. B. Fetters, being first duly sworn, deposes and says: That he is Vice President of I

PECO Energy Company, the Applicas t herein; that he has read the enclosed Technical Specifications Change Request No. 96-23-0 " Deletion of Containment Purge Operational  ;

Time Limit, " for Limerick Generating Station, Unit 1 and Unit 2, Facility Operating License Nos. NPF-39 and NPF-85, and knows the contents thereof, and that the statements and l matters set forth therein are true and correct to the best of his knowledge, information I l

and belief, h

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Subscribed and sworn to before me this / y i of 1997.

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Notary Public ,

Notarial Seal W xpi 999

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ATTACHMENT 1 -

LIMERICK GENERATING STATION l UNITS 1 AND 2 DOCKET NOS.  ;

50-352- l 50-353 i LICENSE NOS.

NPF-39 NPF .

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" Deletion of Drywell and Suppression Chamber Purge System Operational Time Limits" Information Supporting Changes - 5 Pages I

l DISCUSSION AND DESCRIPTION OF THE PROPOSED CHANGES PECO Energy Company (PECO Energy) is requesting Technical Specifications (TS) changes which will delete Drywell and Suppression Chamber Purge System operational time limits stated in TS Requirements 3.6.1.8 and 4.6.1.8, 'Drywell and Suppression Chamber Purge System," and TS Bases 3/4.6.1.8, 'Drywell and Suppression Chamber Purge System? The time limitations applied to opening the containment purge supply and exhaust valves are being removed; however, specific criteria for when the purge valves can be opened will be retained. This activity also adds a surveillance requirement to ensure that the primary containment purge valvss are closed as required or, if open, opened only for TS Identified reasons. These proposed cha . s reflect a similar level of operational control that is contained in NRC NUREG 1433 ' Standard Technical Specifications, General Electric Plants, BWR/4?

A Limerick Generating Station (LGS) TS change was previously approved by the NRC on March 29, 1996 which increased the operational time limit for the purge system from 90 to 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br />. The NRC conditionally approved the 180 hour0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> operational time limit provided that PECO Energy submit a proposal to remove the purge time limit from the TS and replace it with requirements similar to those stated in NRC NUREG 1433 (i.e., improved TS). This TS change request satisfies the March 29,1996, i commitment.

The current 180 hour0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> requirement was approved by the NRC and the staff's conclusions are contained in the March 29,1996 NRC Safety Evaluation. The NRC Safety Evaluation stated that the staff recognized the need to provide operational flexibility, the 180 hour0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> restriction per 365 days provided reasonable margin to expected operational needs, and PECO Energy's supporting Level 2 Probabilistic l Safety Assessment (PSA) analysis results submitted to the NRC were well within the staff's safety goal value (i.e., policy limit) of 1.0 E-6 per year of reactor operation.

SAFETY ASSESSMENT Current LGS TS and LGS Updated Final Safety Analysis Report (UFSAR) requirements limit the operating time of the Drywell and Suppression Chamber Purge System to 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> each 365 days during operational conditions 1,2, and 3. This operational restriction was placed on the use of vent and purge valves since the LGS design involved several exceptions to Standard Review Plan 6.2.4 " Containment isolation System" and Branch Technical Position CSB 6-4 ' Containment Purging During Normal Plant Operations? UFSAR Section 9.4.5.1.2.2 states *Because the purge and vent valves are opened during only a limited period of power operation (less than 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> per year), it is unlikely that a LOCA will occur while the valves are open? This unlikely probability of a malfunction was originally based on engineering judgment and early plant operating experience. The Intent of the restriction is to reduce the probability of, and minimize the consequences of, equipment damage resulting from a LOCA during the time that the large purge and vent valves are open. LGS Units 1 and 2, Safety Analysis Report (SAR) evaluations and a Level 2 Probabilistic Safety Assessment (PSA) analysis pertaining to containment failure have evaluated the risk associated with the current 180 hour0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> limit. The main parameter considered is the large early release frequency (LERF), which considers the release of radioactive material without the occurrence of public evacuation.

The time limitations applied to opening the containment purge supply and exhaust valves are proposed to be removed; however, specific criteria for when the purge valves can be open will be retained. The specific criteria for opening the purge valves includes: inerting, de-inerting, pressure control, ALARA or air quality concerns for personnel entry or Surveillances that require the valves to be opened. The original time limit (prior to the March 29,1996 NRC approval of 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br />) was based on engineering judgment and early plant operating experience, and not based on any analytical requirement. The proposed TS limits on when the valves are permitted to be open will continue to ensure appropriate controls. Use of the purging system will be minimized and limited to the TS identified specific j operations. Industry operating history indicates that when these lines are opened only for the specified j reasons (identified during the development of NUREG 1433) that the open hours are significantly less on

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average than the current General Electric Standard TS allowed cumulative times. Removing the operational time limit for purge system operation does not automatically increase the time limit that these ,

valves w!!I be open. A review of operating history at LGS supports this conclusion. The average open  !

hours for the purge system valves over the last five years is 43 hours4.976852e-4 days <br />0.0119 hours <br />7.109788e-5 weeks <br />1.63615e-5 months <br /> for Unit 1 and 29 hours3.356481e-4 days <br />0.00806 hours <br />4.794974e-5 weeks <br />1.10345e-5 months <br /> for Unit 2.

This proposed change will incorporate the Improved TS (ITS) operational controls which will result in the same order of magnitude of equipment malfunction probability as that provided by limiting purging to 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> per 365 days. An additional Level 2 PSA Analysis (containment failure) was performed to determine the additional risk associated with changing the operating limit from 90 to a nominal 500 l hours each 365 days. 500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> was chosen as an increase on the same level of magnitude that was l previously submitted to and approved by the NRC which increased the open hours from 90 to 180 j hours. The figure of merit that is evaluated is the LERF which represents the likelihood of containment  !

failure following core damage that could significantly affect the public. The 500 hour0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> purge duration increased the LERF approximately 6.6% from the base value of 2.57 E-8 for all PSA initiators. Previous  ;

PSA Analysis for increasing to 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> had shown a 3% increase from the base value calculated at 90 l hours. This analysis concluded that the increase in risk of containment failure is well within the bounds of the EPRI PSA Applications Guideline for permanent changes and the NRC Staff's safety goal value of 1.0 E-6 per year of reactor operation. Industry and LGS historical operating experience indicates that the purging lines are opened only for the specified reason proposed in ITS and for periods which do not  ;

exceed the current magnitude of equipment malfunction probability. Therefore, earlier engineering ]

judgment which established the time limit is now being replaced by operating experience.

This request also adds a TS Surveillance Requirement to ensure that the primary containment purge valves are closed as required or, if open, open only for the TS identified reasons. The Surveillance 4 Requirement is being added to verify the purge valves are closed each 31 days in Operational Conditions 1,2 and 3. The specific criteria for opening the purge valves includes: inerting, de-inerting, pressure control, ALARA or air quality concerns for personnel entry or Surveillances that require the valves to be opened.

The primary containment purge valves are only required to be closed in Operational Conditions 1,2, and

3. If a LOCA inside primary containment occurs in these Operational Conditions, the purge valves may not be capable of closing before the pressure pulse affects systems downstream of the purge valves, or the release of radioactive material will exceed limits prior to the purge valves closing. At other times when the purge valves are required to be capable of closing, pressurization concerns are not present and the purge valves are allowed to be opened. UFSAR Section 9.4.5.1.2.2 for high volume purging, although limiting the operating time the vent and purge system is to be in service, evaluates the consequences of a LOCA should the vent and purge valves be open. This analysis concluded that:

1. The containment isolation valves would close rapidly (less than 6 seconds after receipt of isolation signal) and would terminate the release. Isolation will be complete long before any fuel damage or significant offsite exposure would occur.

2. Failure of the operating Standby Gas Treatment System (SGTS) filter bank as a result of over pressurization or moisture is of little significance since failure of SGTS during a LOCA does not contribute to any significant releases. Additionally, the backup filter bank would be operational.

The LGS Offsite Dose Calculation Manual (ODCM) paragraph 3.3 6 requires that both SGTS trains be operable prior to purging through the SGTS. When the purge system is in use during operational cond.tlons 1,2 and 3 only one SGTS train shall be used to prevent damage to both trains should a LOCA occur. System operating procedures for venting and purging require that the backup SGTS train be isolated (reference procedure S57.1.A *inerting Primary Containment", S57.5.A *De-inerting and Purging Primary Containment", and S57.5.B "De-inerting and Purging the Drywell Only"), thus assuring the availability of SGTS should a LOCA occur as postulated in the above scenario. Even if failure of the backup SGTS train occurs (postulated single active failure), the analysis also showed that total failure of SGTS during a LOCA would not result in significant releases. Based on the above analysis and the subject operational limit, the NRC staff concluded in the SER, NUREG-0991, dated August 1983, that

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' deviation from the explicit provisions of SRP 6.2.4/BTP CSB 6-4 is acceptable since the associated dose I consequences will be within 10 CFR 100, assuming that the undamaged train of SGTS is available.

These proposed changes do not affect the ability of the Drywell and Suppression Chamber Purge I isolation valves to function in response to a LOCA and does not increase the probability that these valves will be open during the initiation of a LOCA since the proposed change will incorporate the ITS j operational controls which will result in the same order of magnitude of equipment malfunction probability as that provided by limiting purging to 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> per 365 days. The probability that one of the two SGTS filter trains will be damaged as a consequence of high volume purging will also not increase as a result of this change.

Information Sucoortina a Findina of No Slanificant Hazards Consideration We have concluded that the proposed changes to the Limerick Generating Station, Unit 1 and Unit 2, Technical Specifications (TS) which will remove the Drywell and Suppression Chamber Purge System Operating time limit of 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> per 365 days, and adds a TS Surveillance Requirement, do not involve a Significant Hazards Consideration. In support of this determination, an evaluation of each of the three (3) standards set forth in 10 CFR 50.92 is provided below.

1. The crocosed Technical Sagcifications chances do not involve a slanificant increase in the orobability or conseauences of an accident oreviousiv evaluated.

This activity does not increase the probability of occurrence of an accident previously evaluated in the SAR. This activity involves deleting the allowable operating limit (180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> each 365 days) for the Drywell and Suppression Chamber Purge system, while maintaining specific criteria for when the valves are allowed to be open. These changes do not increase the probability that this system will be in service shou:d a LOCA occur and does not increase the probability that a LOCA will occur. These changes also do not impact the probability of occurrence of any anticipated operational occurrence, other postulated design basis accident, or other event in which the plant was designed to respond.

This activity does not increase the concequences of an accident previously evaluated in the )

SAR. UFSAR Section 9.4.5.1.2.2 for high volume purging, although limiting the operating time the '

vent and purge system is to be in service, evaluates the consequences of a LOCA should the vent and purge valves be open. System operating procedures for venting and purging assure the availability of SGTS should a LOCA occur. i This activity will not increase the probability of a LOCA occurring during the time the Drywell and 1 Suppression Chamber Purge system is in opeib as previously evaluated. The improved TS  !

do not identify a specific time limit value as long as the valves are operated under the stated I conditions (inerting, de-inerting, pressure control, ALARA or air quality considerations for personnel entry or Surveillances that require that the valves be open). These proposed changes will incorporate the ITS operational controls which will result in the same order of magnitude of equipment malfunction probability as that provided by limiting purging to 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> per 365 days. A LGS Level 2 PSA Analysis was performed to determine the additional risk assochted with changing the operating limit from 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> to a nominal 500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> each 365 days. This analysis concluded that the increase in risk of containment failure is well within the  ;

bounds of the EPRI PSA Applications Guideline for permanent changes and the NRC Staff's  !

safety goal value of 1.0 E-6 per year of reactor operation. Industry and LGS historical operating  !

I experience confirms that the purging lines are opened only for the specified reasons stated in ITS and for periods which do not exceed the current magnitude of equipment malfunction probability. Therefore, earlier engineering judgment is being replaced by operating experience.

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Failure of the operating SGTS filter bank following a LOCA has been found to be acceptable due to the limited benefit derived from SGTS for accident sequences important to plant risk and the possibility that the backup filter bank would be available. Additionally, as discussed in UFSAR Section 9.4.5.1.2.2 the failure of SGTS during a LOCA does not contribute to any significant releases and is bounded by the analysis performed to address containment overpressure rupture.

Deleting the time limit restriction that the vent and purge line isolation valves may be open does not ine ease the probability that these valves will not perform as designed (close upon Isolation signal) in response to a LOCA. Removing the 180 hour0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> requirement will not increase the likelihood that the vent and purge valves will be called upon to close from that previously l evaluated. UFSAR Section 6.2 states that the containment purge valves have undergone extensive testing and analyses to demonstrate the operability of these valves following a LOCA.  !

These changes do not directly or indirectly degrade the performance of any other safety system (assumed to function in the accident analysis) design basis. The potential for other equipment failures in the reactor enclosure due to duct impact, impingement, and the resulting i environmental conditions was previously evaluated in the LGS SAR. It was concluded that the environmental qualifications for the LGS equipment are sufficient to ensure operability under the predicted environmental condition, and, the potential does not exist for impact or impingement -

related damage to essential equipment. Maintaining the existing SAR analysis and retalning I operating criteria for opening the containment purge valves, demonstrates that the risk of equipment failure and resulting radiological consequences will not increase.

Therefore, deleting the TS operating limit for the Drywell and Suppression Chamber Purge system from 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> each 365 days and the addition of a TS Surveillance Requirement verifying that the purge valves are dosed under certain conditions does not increase the probability or consequences of an accident previously evaluated .

2. The orocosed Technical Soecifications chanaes do not create the oossibility of a new or different kind of accident from any accident oreviousiv evaluated.

This activity does not change the function of the Drywell and Suppression Chamber Purge system, the containment Isolation system, or SGTS as previously evaluated. Deleting the

! operational time limit that the vent and purge system is in service and the addition of a surveillance requirement does not create an accident initiator not already considered.

in addition, this activity does not create a failure mode not considered. All evaluated equipment failures that could occur as a result of a LOCA during high volume purging have previously been identified and evaluated. Therefore, these changes do not create the possibility of a new or different kind of accident from any accident previously evaluated.

3. The orooosed Technical Soecifications chanaes do not involve a slanificant reduction in a marain of safety.

The bases of TS 3 S.1.8 state that the 180 hour0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> each 365 day operating limit for the Drywell and Suppression Chaniber Purge system is imposed to protect the integrity of the SGTS filters. The LGS Offsite Dose Calculation Manual assures the availability of the backup SGTS filter train l during operation of the vent and purge system. Furthermore, deleting the operating limit (180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> each 365 days) does not reduce the margin of safety since specific criteria for opening the purge valves is being maintained and does not involve an increase in risk. Therefore, the proposed changes do not involve a significant reduction in a margin of safety.

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' INFORMATION SUPPORTING AN ENVIRONMENTAL ASSESSMENT An Environmental Assessment is not required for the Technical Specifications changes proposed by this TS Change Request because the requested change to the Limerick Generating Station Unit 1 and Unit 2 TS conform to the criteria for ' actions eligible for categorical exclusion," as specified in 10 CFR 51.22 ( c )(9). The requested changes will have no impact on the environment. The proposed TS changes do no involve a Significant Hazards Consideration as discussed in the proceeding safety assessment section. The proposed changes do not involve a significant change in the types or significant increase in the amounts of any effluent that may be released offsite. In addition, the proposed TS changes do not involve a significant increase in individual or cumulative occupational radiation exposure.

CONCLUSION i The Plant Operating Review Committee and the Nuclear Review Board have reviewed these proposed '

changes to the Limerick Generating Station, Unit 1 and Unit 2, Technical Specifications, and have j concluded that they do not involve an unreviewed safety question, they do not involve a Significant Hazards Consideration, and they will not endanger the health and safety of the public.

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