ML20217M712

Safety Evaluation Supporting Amend 135 to License NPF-43

ML20217M712
Person / Time
Site:	Fermi
Issue date:	10/19/1999
From:	NRC (Affiliation Not Assigned)
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ML20217M710	List: ML20217M705 ML20217M712
References
NUDOCS 9910280012
Download: ML20217M712 (8)

Text

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4 UNITED STATES g

,j NUCLEAR REGULATORY. COMMISSION f

WA8HINGToN, D.C. 20066 4 001

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTQR REGULATIQN RELATED TO AMENDMENT NO. 135 FAC!LITY OPERATING LICENSE NO. NPF-43 DETROIT EDISON COMPANY FERMI 2 DOCKET NO. 50-341

1.0 INTRODUCTION

By letter dated September 24,1999, the Detroit Edison Company (DECO or the licensee) requested an amendment to the Technical Specifications (TSs) appended to Facility Operating License No. NPF-43 for Fermi 2. The proposed amendment would revise current TS 3.6.1.8 by adding footnote "" to Action b. The footnote would allow continued operation of Fermi 2 with

' the leakage of penetration X-26 exceed;ng the limit in TS 4.6.1.8.2, provided certain compensatory measures are taken. Operation would be cllowed to continue until the next plant shutdown.

Because th a NPC s'.aff issued the Fermi 2 improved standard TSs (ITS) on September 30, 1999 (Amundment No.134), with implementation within 90 days, the licensee also provided a version of the TS amendment that would be compatible with the ITS. This version would add a new special operations TS, ITS 3.10.8, to address the compensatory actions and other requirements associated with penetration X-26.

2.0 BACKGROUND

Current TS 3.6.1.8, "Drywell and Suppression Chamber Purge System," addresses the requirements associated with the purge system containment penetrations. TS 4.6.1.8.2 requires the licensee to verify that the leakage rate of each of the associated isolation valves is less than or equal to 0.05 L, when pressurized to design-basis loss-of-coolant-accident maximum peak containment pressure (P,, or 56.5 psig). L,is defined as the maximum allowable leakage rate for the primary containment. If the leakage rate limit in TS 4.6.1.8.2 is exceeded by any valve, that valve would be declared inoperable and the licensee would enter TS 3.6.1.8, Action b. Action b requires the licensee to restore any inoperable valve (s) to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in hot shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in cold shutdown within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Penetration X-26 has three primary containment isolation valves (PCIVs) that are tested concurrently (i.e., the test does not provide the leakage rates for individual valves; rather, it provides the combined leakage rate for all three valve ' ) The single inboard isolation valve is a 24-inch butterfly valve (T4803F601) and the two outboard isolation valves (in parallel) are a 24 inch butterfly valve (T4800F407) and a 10-inch butterfly valve (T4800F408). The piping configuration is such that T4800F407 is open directly to secondary containment on one side.

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. This configuration lends itself to a direct visualinspection of the valve seat. Valve T4800F408 Lonnects to the nitroger' Oupply system. During leak testing, boundary valves are used to isolate T4800F408 f,om the nitrogen system. A vent valve between T4800F408 and the test boundary valves is used to depressurize and vent the piping outboard from T4800F408.

On September 22,1999, the licensee performed a local leak rate test (LLRT) for penetration X-26, as required by TS 4.6.1.8.2. This test was performed by pressurizing between the inboard and outboard isolation valves and measuring the total leakage of the isolation valves. The penetration exceeded its TS limit of less than 0.05 L. (equivalent to 14.87 standard cubic feet per hour (SCFH)). The measured penetration leakage rate was

~ 26.7 SCFH. Based on direct observation of T4800F407 and observation of an open %-inch vent connection outboard of T4800F408, licensee test personnel concluded that the penetration failed its LLRT due to seat leakage through T4803F601. Subsequently, the licensee stroked T4803F601 under light pressure in an attempt to clear the sealing surfaces of any debris. The licensee performed the LLRT again, and the leakage from penetration X 26 increased to 82.85 SCFH. Since the only evolution performed between the two LLRTs was the stroking of T4803F601, the licensee concluded that this subsequent LLRT result substantiated that the leakage was attributable to T4803F601. A licensee level 11 VT inspector performed visual and audio inspection (utilizing Snoop, a soap bubble-type test, to aid in leak detection) for leakage

. at the exposed side of T4800F407 and at the vent connection outboard of T4800F408 during both tests on September 22,1999. The licensee indicated that the inspector observed insignificant leakage relative to the measured leakage rates. A licensee level 111 VT inspector also observed the leakage testing and concluded that T4800F407 and T4800F408 were

~ insignificant contributors to the leakage during the second test. Snoop was utilized to aid in leak detection during both tests. Snoop was applied to the seal of T4800F407 and minor bubbling was observed. It was also used at the vent connection outboard of T4800F408 and no leakage was detected through this valve.

The licensee reviewed the LLRT and maintenance records and did not find any indication of an adverse trend for this penetration. Results of previous LLRTs for the penetration ranged between approximately 0.6 SCFH and 1.75 SCFH since October 1998 (four tests). Failure of T4803F601 was not anticipated and, based on the magnitude of the leak and the change in leakage following valve stroke, the licensee concluded that the likely cause of the leakage was failure of the seal. The seal was replaced during the Sixth Refueling Outage (autumn of 1998).

Based on the previous test results, the licensee concluded that it is unlikely that the cause of this test failure is attributable to any valve other than T4803F601.

Consistent with 10 CFR 50, Appendix J, for' total Type B and Type C testing, the overall primary containment leakage allowed by TS 3/4.6.1.1 is 0.6 L,. This equates to 178 SCFH.. The sum of the known leakage from all containment penetrations prior to the September 22,1999, test was G7.28 SCFH, leaving a margin of 110.72 SCFH. The leakage from penetration X-26 was 82.85 SCFH, leaving a margin of 27.87 SCFH, when considering T4803F601 as a single boundary valve (i.e., not crediting the outboard valves to limit leakage). The outboard valves,

.when closed, would he expected to significantly increase this margin, even though the leakage through the outboard valves could not be quantified. In addition, with the penetration X-26 outboard valves closed, the licensee concluded that the leakage for this penetation remains well within the 0.05 L, limit associated with TS 3.6.1.8.

3-On September 23,1999, the licensee requested that the NRC exercise discretion not to enforce compliance with the actions reouired in TS 3/4.6.1.8. The licensee's safety basis for this request is summarized as follows:

The licensee will isolate the affected penetration using outboard isolation valves T4800F407 and T4800F408. While leak rate testing for this penetration can not quantify the leakage of the outboard valves individually, the licensee believes the leakage rate through these isolation devices is well below the acceptance criteria, as discussed above. In addition, the licensee will periodically verify that the penetratiorris

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isolated. The licensee stated that the raliability of the resilient seals in these valves and the other similar penetrations at Fermi 2 has been high, providing confidence that unexpected degradation is not occurring in these valves.

l The licensee stated that T4803F601 is not a risk-significant component in the Level 1 Fermi 2 Probabilistic Safety Analysis' (PSA). The licensee concluded that T4803F601 is not an initiator of an event that leads to core damage and does not mitigate a core damage event and the failure of T4803F601 has no effect on core damage and is not modeled in the Level 1 Fermi 2 PSA.

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~ The licensee stated that T4803F601 ja a credited component of the Level 2 Fermi 2

.. PSA. To isolate penetration X-26, T4803F601 pr the outboard isolation valves must close. The success criterion is that either inboard or outboard isolation valves in a line must close and remain closed for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.- With the penetration isolated by the outboard isolation valves, the licensee concluded that the failure of T4803F601 has no effect on the Level 2 PSA results and the success criteria for penetration X-26 is met -

and, therefore, failure of T4803F601 is not risk significant.

In conjunction with the discretion requested, the licensee committed to the following compensatory actions:

1.

Isolation valves T4800F407 and T4800F408 (both normally closed) will remain closed and be deactivated, assuring the valves remain closed until T4803F601 is repaired.

T4800F407 and T4800F408 will not be cycled until the plant is shutdown to repair

T4803F601.

2..

Isolation valves T4800F407 and T4800F408 will be verified closed every 31 days.

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Because the leakage through the outboard isolation valves cannot be individually quantified, a flanged cover will be installed over the opening of T4800F407 by 8

September 28,1999, to provide an additional leakage barrier. This flange will remain in

. place until the plant is shut down to correct the penetration leakage.

in simple' terms, the Level 1 PSA evaluates the response of the plant to transients, 0

- expressed in the form of core damage frequency. The Level 2 PSA evaluates the containment response to the events developed in the Level 1 PSA.

e Thi flanged cover was installed on September 25,1999.

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Leak testing of this penetration will be performed at least every 45 days to verify that the 0.6 L,is not exceeded due to additional penetration leakage. This testing will also qualitatively verify the integrity of the outboard isolation barriers (employing Snoop and visual and audio inspection techniques similar to those used on September 22,1999, as described above).

The licensee concluded that the proposed action will not change the types or amounts of effluents that may be released offsite, nor increase individual or cumulative occupational radiation exposures, since the proposal is expected to maintain the overall leakage of the penetration within the required limits.

The NRC staff verbally granted a Notice of Enforcement Discretion (NOED) at 5:30 p.m.

eastem daylight time on September 23,1999. By letter dated September 27,1999, the staff

- documented its issuance of the NOED. The licensee requested an exigent license amendment on September 24,1999, to modify TS 3.6.1.8 to incorporate the actions agreed upon in the NOED.

3.0 EVALUATION The licensee pre,ased to add a footnote """ to TS 3.6.1.8, Action b to allow continued operation of Fermi 2 with the leakage for penetration X-26 exceeding the limit in TS 4.6.1.8.2.

Operation may continue until the next plant shutdown, provided

. - T4800F407 and T4800F408 are closed and deactivated, i

a flanged cover is placed over the open end of T4800F407, e

T4800F407 and T4800F408 are verified closed and deactivated every 31 days, and

_ Leakage testing is performed on penetration X-26 at least every 45 days to verify that the limit of 0.6 L,is not exceeded and to allow qualitative testing of the outboard valves, i

There are two branches in the outboard portion of penetration X-26. One branch is tw.ated by T4800F408 and the other branch is isolated by T4800F407. These two branches will be discussed individually.

Based on the information provided, the staff concludes that the Snoop testing results for outboard valve T4800F408 provide reasonable assurance that this valve is currently leak-tight.

Maintaining this valve closed and deactivated will provide an acceptable containment boundary as long as the valve seal does not degrade, in addition, because these valves are in a mild environment, the most likely cause of seal degradation is mechanical failure caused by stroking the valve. Maintaining the valvu closed eliminates this failure mechanism. The periodic leakage testing of penetration X-26 will alert the licensee to any degradation in the valve seal caused by other mechanisms. Therefore, the NRC staff concludes that the TS change is acceptable for this branch of the penetration.

The situation for the other branch of the penetration, containing T4800F407, is similar to that

. described for T4800F408 and the same arguments can be applied. However, unlike

. T4800F408, the leakage rate through T4800F407 was not zero based on the qualitative testing.

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5-While the licensee estimated that the leakage through T4800F407 was very low, the compensatory action of adding a blank *lange to the end of that pipe will provide further assurance that there is little or no leakage through this portion of the penetration. The blank flange was installed on September 25,1999. Based on the compensatory actions, the NRC staff concludes that the TS change is acceptable for this branch of the penetration.

Finally, the footnote specifically requires that the leakage for penetration X-26 be restored within limits prior to startup from the next plant shutdown. This requirement, as written,

. encompasses both planned and unplanned shutdowns.

The staff issued the ITS (Amendment No.134) on September 30,1999. The licensee provided an ITS version of the proposed TS change in its submittal. The change adds a new special operations TS, ITS 3.10.8, to address the same issues addressed in the proposed footnote """

- to current TS 3.6.1.8, Action b.'

i ITS 3.10.8 would modify ITS 3.6.1.3, "PCIVs," to exclude penetration X-26 flow paths for purge valve leakage rate not within limits, provided

.T4800F407 and T4800F408 are closed and deactivated, a flanged cover is placed over the open end of T4800F407, and

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. the special operations allowance is withdrawn on the first entry into Mode 2 (startup ) or 8

Mode 3 (hot shutdown).

~ A note to the limiting condition for operation (LCO) states that, upon exiting the LCO, the 24-hour completion time for inoperable purge valves allowed in ITS 3.6.1.3 Required Action D.1 is considered expired for purge valve leakage not within limits, in other words, the licensee would immediately enter the shutdown action in ITS 3.61.3.

The ITS version also adds two surveillance requirements (SRs). SR 3.10.8.1 requires the

licensee to verify that T4800F407 and T4800F408 are closed and deactivated every 31 days.

SR 3.10.8.2 requires the licensee to perform an LLRT of penetration X-28 every 45 days and compare the results to the 0.6 L, limit provided in ITS 3.6.1.1. A note to the frequencies for

' these two SRs states that SR 3.0.2 is not applicable. This means that the licensee is not permitted to apply a 25-percent tolerance to the frequencies of the SRs.

The NRC staff concludes tnat the proposed ITS version provides the same requirements as the current TS version. Therefore, as discussed above, these changes are acceptable.

4.0. EXIGENT CIRCUMSTANCES The Commission's regulations at 10 CFR 50.91 contain provisions for issuance of amendments where the Commission finds that exigent circumstances exist, in that a licensee and the Commission must act quickly and that time does not permit the Commission to publish a 3 This mode is entered below approximately 15-percent power. Including this mode in the requirements ensures consistency with the requirements in the current TSs.

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' Federal Register notice allowing 30 days for prior public comment before issuance of an amendment.. The exigency exists in this case in that the proposed amendment is needed because Fermi 2 is operating under a NOED, and time does not permit the Commission to l publish a notice allowing 30 days for prior public comment.

In its application, the licensee explained why it could not have foreseen the need for this amendment. The amendment is required to allow continued plant operation after penetration X-26 unexpectedly failed its LLRT on September 22,1999. Based on the data it collected, the licensee believes the high leakage is passing through inboard _ containment isolation valve T4803F601. The results of previous LLRTs nad not indicated any adverse tre.,d in the

- leak-tightness of this penetration. In accordance with NRC procedures described in NRC Inspection Manual, Part 9900, Notices of Enforcement Discretion, dated J. ne 29,1999, the licensee applied for this license amendment within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the NRC staff verbally issued the NOED on September 23,1999.

Accordingly, the Commission has determined that exigent circumstanc,es exist pursuant to 10 CFR 50.91(a)(6), the submittal of information was timely, and the licensee did not create the exigency.'

5.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION

S DETERMINATION The Commission's regulations in 10 CFR 50.92(c) state that the Commission may make a final determination that a license amendment involves no significant hazards consideration lf

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. operation of the facility in accordance with the proposed amendment would not (1) involve a significant increase in the probability or consequences of an accident previously evaluated,

(2) create the possibility of a new or different kind of accident from any accident previously evaluated, or (3) result in a significant reduction in the margin of safety. The NRC staff has made a final determination that no significant hazards consideration is involved for the

.. proposed amendment and that the amendment should be issued as allowed by the criteria contained in 10 CFR 50.91. The NRC staff's final determination is presented below.

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1. The proposed change does not involve a significant increase in the probability or

. consequences of an accident previously evaluated.

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The proposed change provides an exception for Drywell Air Purge penetration X-26 to

.TS 3.6.1.8, Action b, to allow continued operetion with inboard isolation valve T4803F601 exceeding the leakage rate limit. Valve T4803F601 is not an initiator of an

event or involved in an accident initiation sequence. Therefore, the proposed change

, does not involve an increase in the probability of an accident.

Either T4803F601 or the outboard isolation valves must close to isolate penetration X-26. With the penetration isolated by the outboard isolation valves and a blank flange, as required by the proposed change, failure of T4803F601 would involve no significant increase in the consequences of an accident since the containment function is preserved.

Therefore, the proposed change does not involve an increase in the probability or consequences of an accident.

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2. The proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.

Valve T4803F601 is an inboard containment isolation valve. The safety function of the valve is to provide for containment penetration X-26 postaccident isolation. Valve T4803F601 and two outboard isolation valves (T4800F407 and T4800F408) comprise the penetration's isolation capability. The valves' safety function is to close and remain closed. The outboard isolation valves are normally closed isolation valves that will be closed and deactivated by the proposed change. Therefore, no new or different types of failures or accident initiators are introduced by the proposed change.

3. The change does not involve a significant reduction in the margin of safety.

Operating with excessive leakage on T4803F601 places additional reliance on T4800F407 and T4800F408, as they would be the single containment barrier. The change includes closing and deactivating the outboard containment isolation valves and adding a blank flange outboard of T4800F407 to provide assurance the penetration is isolated. Closing and deactivating these valves eliminates the potential that any active failure could lead to loss of function. Previous leak performance and ongoing periodic leak testing minimize the potential that passive failures would occur for these valves undetected. The change does not involve a new mode of operation or change to the transient analyses in the Updated Final Safety Analysis Report. Therefore, the proposed change does not involve a significant reduction in the margin of safety.

6.0 STATE CONSULTATION

in accordance with the Commission's regulations, the Michigan State official was notified of the proposed issuance of the amendment. The State official had no comments.

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7.0 ENVIRONMENTAL CONSIDERATION

The amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has made a final finding that the amendment involves no significant hazards consideration. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessrrient need be prepared in connection with the issuance of the amendment.

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8.0 CONCLUSION

j The Commission has conciuded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor: A. Kugler Date:

October 19, 1999

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