ML20116J882

Forwards Request for Addl Info Re Tech Spec Change 91-09, Containment Radiation Monitor Isolation

ML20116J882
Person / Time
Site:	Sequoyah
Issue date:	11/06/1992
From:	Joshua Wilson TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-M81384, TAC-M81385, NUDOCS 9211160417
Download: ML20116J882 (5)

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Vk 1em w ee, Aeon tw owe o uc sta twr u mmwe vm J.L Wdson ve- nwuor. scown mewu hw November 6, 1992 U.S. Nuclear Regulatory Connaission ATTN: Document Control Desk Wachington, D.C. 20555 Gentlemen:

In the Matter of ) Docket Nos. 50-327 j Tennessee Valley Authority ) 50-328 SEQU0t'All NUCLEAR PLANT (SQN) 'IECHNICAL SPECIFICATION CHANGE 91-09, CONTAINMENT RADIATION MONITOR ISOLATION, REQUEST FOR ADDITIONAL INtORMATION RESPONSE (TAC NOS, M81384 AND M81385)

References:

1. NRC letter to TVA dated March 12, 1992, " Technical Specification Change 91-09, Containment Radiation Monitor Isolation, Request for Additional Information - ,

Sequoyah Nuclear Plant, Units 1 and 2 (TAC Nos. M81384 and M81385)" -

2. 'IVA letter to NRC Jated August 27,199'., "Sequoyah Nuclear Plant (SQN) - T?chnical Specification (TS)

Change 91-09, Revision of Containment Radiation Monitor Requirements" TVA submitted TS Change Request 91-09 to NRC by Reference 2. During NRC's review, questions were identified that required additional informatica to support NRC's approval'of the reouested TS change. TVA provided answets to questions in telephone conferences held on ,

January 21, February 4, February 20, and' March 2, 1992. NRC subsequently provided the questions requiring addit.ional information by Reference 1 and requested 'IVA to document the answers that we-e verbally discussed in the telephone calls and address recaining NRC_ questions. The enclosure to this submittal provides "2VA's written response to the NRC questions.

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U.S. Nuclear Regulatory Commissicn Page 2 LNovember 6, 1992

-i Please diract questions concerning this insue to K. C. Weller at (615) 843-7527.

Sincerely, e

S nA.

L. Wilson Enclosure

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Mr. D. E. LaBr.rge, Project Manager U.S. Nuclear Regulatory Commissica One White Flint, North 11555 Rockville Pike '

Rockville, Maryland 20852 NRC Resident Inspector Sequoyah Nuciatr Plant 2600 Igou Ferry Road ,

' Soddy Daisy,_ Tennessee 37379 Mr. B.'A. Wilson, Project Chief.

U.S. Nuclear Regulatory Commission Region-II,

~101 Marietta Street, NW, Suite 2900' Atlanta, Georgia 30323-k

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ENCLOSUAE O

e Responses to NRC's Request _for Additional Information Technical Specification _(TS) Change 91-09 ,

1. "In the justificrtion for the proposed Technical Specification-(TS) I amendment, TVA noted that the Containment Gas and Particulate Radiation Monitors do not provide any primary safety-f anctions for containmect valvo isolation (CVI) in the Sequoyah Final Safety Analysis Report (FSAR). However, in the amendment request, TVA did not explain why the CVI signal associated with the radiation monitor is in tt's TS. Thus, the -taff has f und it difficult to ensure that deletion of the CVI from ae TS will not result in an unreviewed safaty question. The staif requests that TVA describe the original basis for inclusion of the CVI signal in the TS, and an explanation of why, based on this information, the CVI is no longer needed."

Response: ,

Section 12.2.4.1.2 of the FSAR states, "The initiation of containment ventilation isolation by channels RE-90-106A, RE-90-106B, RE-90-112A, and RE-90-112B is a design feature that pre-dates 6he provision of the containment purge exhaust monitors in the plant design."

Decisions were made to maintain the CVI actuntion function for the existing cantainment radiation monitors as e conservative design measure upon the addition of the containment purge radiation monitors even though they werc not assumed in the accident analysis. The spurious CVI actuations that SQN has experienced from these monitors during operation were not anticipated.

The NRC standard TSs in use at the time SQN was licensed teluded requirements for CVI. Both sets of radiation monitors were included because they were installed in the plant. In general, the instrumentation section of the standard TSs reflected installed equipment rather than just that assumed in the accident analysir.

(e.g., see Bases for reactor protection system channel). On the other hand, no standard TS existed at that time for the filtration system of the reactor building purge ventilation system (RBPVS).and none was proposed by NRC. These conditio..s were accepted by the staff in NUREG-0011, Section 16.0 (page 16-1), which states, "Furthermore, the limiting conditions for operatione _and surveillance requirements will assure that nece aary engineered safety features -

will be available in_ the event of malfunctions within the plant."

Since initial licensing, standard TSs have changed;with respect to CVI and RBPVS. The technical justification for the deletion of the CVI signal has been provided in proposed TS Chante 91-09, and it;is-concistent with the current licensing basis for GQN. The deletion of the CVI initiation signal from the containment radiation monitor channels will reduce some diversity for CVI actuation; however, it olli not reduce any redundancy or. diversity in the safety analysis'-

l (reference CSAR Sections 15.4.5 und 9.4.7.3).

In summary, TVA concludes that the existing CVI acteation from the containment radiation monitors provides additional but unnecessary L isolation capability relative to other design features:and the SQN l accident analysis assumptionc. Spurious or inadvertent actuations from these radiation monitors needlessly challenge isolation' safety systems.

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2. "The staff noted that, even though credit is not taken for the purge radiation monitcrs in the FSAR, credit is takca for cleanup of a release due to a fuel handling accident using $he Reactor Building Purge _ Ventilation System (RBPVS), an engireered safety system consisting of HEPA filters and charcoal absorbers. The-FSAR further etates that during refueling operatioas, the containment will either be isolated or ventilated through the RBPVS. This commitment was also noted in Section 15.4.2 of the staff's SER during the operating licensing phase. Credit for this Engineered Safety Feature was noted in the same section.

"However, staff review of the proposed amendment hac determined that there are no TS [ SIC] that define the operability or surveillance requirements for the RBPVS. Consequently, removal of the isolation f unction presently served by the Containment Ges and Particulate Radiation moritors would remove a TS-controlled safety feature that could limit the potential consequences of a fuel handling accident and remove the only radiation monitor that is .equited to be operable ,

fu all modes that could initiate a CVI. sherefore, it appears that the analysis for the fuel handling accident inside the containment is not rupporte' by the proposed amendment.

" Provide the baris for not having a TS on the RBPVS and justification for the proposed removal of the isolation function of the Containment Gas and Particulate monitors without having such a TS."

Response

While it is true that the containment gas and particulate radiation monitors are a TS-centro 11ed feature, the CVI feature is redundant-to that of the RBPVS radiation monitors, which are similarly TS controlled. In addition, whil TS 3.3.3.1 currently requires the containment gas and particulate radiation monitors to be operable in "ALL MODES," it also requires the RBPVS radiation monitors to be operable in all modes except Mode 5 in which containment integrity is not required. Also, TS 3.9.9 requires the CVI system to be operable during " CORE ALTERATIONS" or movement of irradiated fuel witnin the containment. From the combination of the above constraints, there are no additional credible failure modes for which the RBPVS radiation monitors do not provide adequate coverage as required by the accident analyses.

With respect to the RBPVS filtration system, not only~1s the system of the same design as the other engineered safety feature filtration systems, but the filters have been and are currently administrative 1y controlled ans tested in a method consistent with the other TS filtration systems in accordance with the parameters = defined in the FSAR, which is maintained current with accident analysis. Further,_

during the initial licensing of SQN, the NRC staff was aware that the RBPVS_ filtration system was considered to be an emergency safety '

feature (ESF) system; however, incorporation into the SQN TSs was not considered to be necessary.

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F In an effort to eliminate any perceived confusion between the FSAR-and ISs TVA is working with Westinghouse Electric Corporation to complete an evaluation of the SQN fuel Landling accident inside containment without taking credit for the RBPVS high-ef ficiency particulate air filters and charcoal adsorbers. This analysis will utilize the containment ventilation isolaticn features as actuated by the containment purge radiation monitors for ensuring compliance with 10 CFR 100 requirements. Operability of the containment purge rad 4stion monitors and isolation valves will continue to be required by the SQN TSs and is designed with appropriate redundancy and functionality to satisfy safety-reluted design requirements.

This ongoing annlysis has no bearing or. the requested TS change relative to CVI actuation radiation monitor hources. No cradit is presently taken or will be taken for any CVI sctuation from the containment radiation monitors. Instead, these monitots will only be used to provide the RCS leak-detection fenctions. Therefore, the proccasing of the CVI actuaticn deletion for the containment radiation monitors proposed by TS Change 91-09 is not affected by the curren' ESF status of the RBPVS filters and udsorbers or the future proposo reanalysis.

3. "TS Surveillance Requirement 4.9.9 requires that CVI operability tests be performed using a test signal from the ' containment rad'.ation monitoring instrumentation channels.' Presumably, the referenced instrument channels consist of the Containment Purge Radiation Monitoring System and the Containment Gas and Particulate Radiation Monitoring System. Since the containment' radiation monitoring function of the Containment Gas and Particulate Radiation Monitors is not af fected by the proposed TS change, explain wkr this TS requirement is not affected by the proposed amendment."

Response

TVA evaluated the impact to TS 4.9.9 during_the preparation and review of TS Change 91-09 and determined that a revision to this surveillance requirement (SR) was not-necessary. This was based on the position that containment radiation monitoring instrumentation chanaels applicable to this SR would be_ limited to the radiatirn monitors that have CVI actuation capability. Thertforc, the application of this 3R to the upper- and lower-ccau inment radiation monitors, af ter deletion of CV1 actuation circuitry,= would not be l .;51evable and was considered to no longer apply to these monitors.

l In order to prevent any confusion'with the application of SR 4.9.9, TVA is amenable to the modification of this SR-to clarify that it only applies to the containment purge air exhaust radiation l

monitors. This clarification of the SR would not alter any of the L discussions previously provided in the original TS Change 91-09 submittal or significant hazards evaluation. The addition of this

" clarification" te t*e TS amendment would be considered a clarification that s.oports the changes pron sed in the original IS Change 91-09 submittal, and no additional justifications would be

! required.

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