ML20085K324

Safety Evaluation Supporting Amend 167 to License DPR-20

ML20085K324
Person / Time
Site:	Palisades
Issue date:	06/08/1995
From:	Office of Nuclear Reactor Regulation
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ML20085K314	List: ML20085K310 ML20085K324
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NUDOCS 9506230287
Download: ML20085K324 (5)

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UNITED STATES 4

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j-NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION I

RELATED TO AMENDMENT NO. 167 TO FACILITY OPERATING LICENSE NO. DPR-20 CONSUMERS POWER COMPANY PALISADES PLANT 4

DOCKET NO. 50-255 i

1.0 INTRODUCTION

d By letter dated January 13, 1995, as supplemented April 12 and 27,1995, the Consumers Power Company (the licensee) requested an amendment to the Technical Specifications (TS) appended to Facility Operating License No. DPR-20 for the Palisades Plant. The proposed amendment would modify the required settings and allowable "as found" and "as left" tolerances for the primary and 1

secondary safety valves. Specifically, the proposed limits would allow j

installed primary and secondary valve settings to be within a 3 percent tolerance of their nominal settings, but would require returning the valve i

settings to within 1 percent of the nominal settings if the valves are removed from the piping for maintenance or testing.

l The April 12 and 27, 1995, letters provided clarifying information ir. response to the staff's request for additional information of April 11, 1995, and a telephone request for information on the Palisades loss of load analysis 4

contained in the January 13, 1995, submittal. This information was within the i

scope of the original application and did not change the staff's initial no significant hazards consideration determination.

The licensee proposed changes to TS 3.1.7 and its associated bases.

These changes are summarized below:

1.

Current TS 3.1.7a requires that all three pressurizer safety valves (PSV) be operable when the reactor is critical.

Proposed TS 3.1.7.1 would require that all PSVs be operable when the plant is operating above cold 5

4 shutdown.

l 2.

Current TS 3.1.7c requires that a minimum of 23 (out of 24) main steam i

safety valves (MSSV) be operable during power operation.

Proposed TS j

3.1.7.2 would require that a minimum of 23 MSSVs be operating when the plant is operating above cold shutdown.

I 3.

Current TS 3.1.7b requires that a minimum of one operable PSV be installed whenever the head is on the reactor vessel.

Proposed TS 3.1.7 would 4

delete this requirement.

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Current TS 3.1.7a requires that the lift settings for all three PSVs be maintained within i I percent of their nominal setpoints.

Proposed TS 3.1.7.1 would change the tolerance band to i 3 percent.

5.

Proposed TS 3.1.7.1 and 3.1.7.2 specify the individual setpoints and tolerance bands for all PSVs and MSSVs. Tables 3.1.7-1 and 3.1.7-2 reflect the revised tolerance band of item 4 above.

6.

Current TS 3.1.7 does not contain an action statement pertaining to inoperable safety valves.

In the event of an inoperable safety valve, Palisades TS 3.0.3 becoscs :pplicable. TS 3.0.3 requires that the plant be placed in hot standby within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />, hot shutdown within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />, and cold shutdown within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />.

Proposed TS 3.1.7 adds an action statement regarding inoperable PSVs and MSSVs which requires the plant to be placed in hot shutdown within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and cold shutdown within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

7.

Proposed TS 3.1.7 (as revised in the licensee's April 27, 1995. submittal) states that "after testing or valve maintenance which could affect the setting, it shall be reset to within 1 percent of the nominal setpoint prior to being returned to service." This statement' applies to PSVs and MSSVs.

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2.0 EVALUATION At Palisades, there are three PSVs with nominal setpoints of 2500 psia [ pounds per square inch, absolute), 2540 psia, and 2580 psia, and a total of 24 MSSVs which have nominal setpoints of 985 psig [ pounds per square inch, gauge], 1005 psig, and 1025 psig. The function of the PSVs and MSSVs is to provide i

overpressure protection for the primary and secondary systems, thus limiting i

the pressure to within 110 percent of the system design pressures.

The licensee is proposing to revise the Palisades TS to allow a relaxation in the PSV setpoint tolerances for the as-found test condition from i I percent to i 3 percent. The current TS setpoint tolerance for the MSSVs is i 3 percent.

i The licensee is also proposing to reset the PSVs and MSSVs to within 1 percent of nominal setpoints after testing or maintenance which could affect the setting. This will reduce the possibility of setpoint drift outside the allowable tolerance.

The licensee stated that the existing TS criteria for the PSV setpoint tolerance (i I percent) was derived from the American Society of Mechanical

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Engineers (ASME) Code,Section III, NB-7524.3, which requires a tolerance of i I percent for the original construction.

Further, the licensee stated that throughout the history of testing of the PSVs it has been common for at least one PSV to exceed the i I percent criterion.

However, there have only been two occasions when the as-found setting exceeded the i 3 percent criterion.

If a safety valve is-tested and found to be outside the allowable tolerance, additional valves must be tested in accordance with ASME Code,Section XI.

Increasing the as-found setpoint tolerance will, therefore, reduce the frequency of requiring more than one valve to be tested during a refueling 4

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outage. The staff agrees that the increase in the PSV setpoint tolerance to i 3 percent is acceptable provided the licensee can demonstrate that adequate overpressure protection is provided.

In accordance with the ASME Code, the PSVs and MSSVs must be designed with sufficient relief capacity to limit the primary and secondary side pressures to less than 110 percent of their design values during the most severe design basis overpressure. transient. The loss of external load event represents the

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most limiting transient for both the primary and-secondary systems. For the 1

proposed upper limit (+3 percent) on PSV setpoint tolerance to be deemed acceptable, it must be demonstrated that the primary and secondary system pressures remain below 2750 psia and 1100 pria, respectively, during this transient when the PSVs'and MSSVs are set at 3 percent above their nominal j

j setpoints.

The licensee has performed the requisite analysis using an approved model (ANF-RELAP) and has documented the results in its January 13, 1995, submittal.

The following conservative assunptions were made in order to. maximize primary and secondary system pressures during the analyzed event:

+. Normally, the turbine trip which accompanies the loss of external load event causes a direct reactor trip.

For the Palisades analysis, the reactor trip on turbine trip is assumed to be disabled.

The steam dump (turbine bypass) system is assumed to be unavailable.

i a

A 25 percent steam generator tube plugging level-is assumed.

j An initial pressurizer level which is 10 percent above the programmed level for full power operation is assumed.

No credit is taken for relief through the pressurizer power-operated relief valves (PORVs).

PSV and MSSV accumulation (+3 percent) is accounted for.

Rated power ceditions are assumed at event initiation.

The results of the licensee's analysis indicate that both primary and secondary system pressures remain below 110 percent of the design value during the limiting overpressure event. Therefore, the acceptance criteria are met for the proposed upper limit (+3 percent) on the PSV setpoint tolerance.

To demonstrate the acceptability of the proposed lower limit (-3 percent) on the PSV setpoint tolerance, the licensee reviewed all existing departure from nucleate boiling (DNB) analyses to determine whether the PSVs would become challenged as a result of the revised lower limit.

For those events during which a significant increase in primary system pressure occurs, the peak pressurizer pressure never exceeds 2200 psia and the PSVs (with the current -l f

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percent setpoint tolerance) are not challenged. With the propsed -3 percent setpoint tolerance, the lowest PSV setpoint is 2425 psia and therefore, the PSVs remain unchallenged.

4 Proposed TS 3.1.7.1 and 3.1.7.2 include the requirement that all PSVs and at least 23 (out of a total of 24) MSSVs be operable when the plant is operating above cold shutdown. This encompasses the current requirements (T5 3.1.7a and 3.1.7c) that these valves be operable when the reactor is critical or in power i

operation and is therefore acceptable.

Furthermore, the licensee has verified that with one inoperable MSSV in any of the three valve banks, adequate relief capacity exists to maintain secondary system pressure below 110 percent of the i

design value during the loss of external load event.

The proposed deletion of current TS 3.1.7b (which requires that a minimum of i

one operable PSV be installed whenever the head is on the reactor vessel) is acceptable because the combined range of applicability of current TS 3.1.8 and proposed TS 3.1.7.1 encompasses that of TS 3.1.7b.

Current TS 3.1.8 ensures that overpressure protection is provided for the primary system during cold shutdown. This is accomplished via the pressurizer PORVs operating in the low temperature overpressure protection (LTOP) mode.

i The inclusion of Tables 3.1.7-1 and 3.*t.7-2 in proposed TS 3.1.7.1 and 3.1.7.2 i

serves to clarify the setpoint values and corresponding tolerance bands for each of the PSVs and MSSVs and therefore represents an acceptable administrative change. The licensee's April 25, 1995, letter revised the footnotes to these tables initially propm ed in the January 13, 1995, submittal.

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The proposed action statement added to TS 3.1.7 to address inoperable PSVs and l

MSSVs, when compared with existing TS 3.0.3, allows essentially the same amount of time to reach hot shutdown, but allows an additional 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br /> to 4

i reach cold shutdown. As noted above, TS 3.1.8 ensures overpressure protection for the reactor coolant system (RCS) via the LTOP system during low temperature operation. This system is automatically activated whenever the RCS temperature drops below 430*F. Therefore, during most of the transition i

period between hot shutdown (525'F) and cold shutdown (210'F), the PORVs and not the PSVs are the principal source of RCS overpressure protection.

During this same period, the MSSVs would not be challenged because secondary pressure is well below the MSSV setpoints.

(At 525'F, the saturation pressure is approximately 850 psia). Consequently, the 11-hour relaxation in the time allowed to reach cold shutdown does not have a significant impact on plant safety and is therefore acceptable.

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3.0 STATE CONSULTATION

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

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4.0 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. 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 previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding (60 FR 11130). 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 assessment need be prepared.in connection with the issuance of the amendment.

5.0 CONCLUSION

The staff has concluded, 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 Contributors:

H. Abelson and G. Hammer Date:

June 8, 1995 1

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