Text

Safety Evaluation Supporting Amends 151 & 139 to Licenses DPR-39 & DPR-48
	ML20058G298
Person / Time
Site:	Zion File:ZionSolutions icon.png
Issue date:	11/29/1993
From:	; Office of Nuclear Reactor Regulation
To:	;
Shared Package
ML20058G257	List: ML20058G254; ML20058G266; ML20058G298;
References
	GL-90-06, GL-90-6, NUDOCS 9312090166
	Download: ML20058G298 (6)
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UNITED STATES

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NUCLEAR REGULATORY COMMISSION n

WASHINGTON, D. C. 20555

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l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.151 TO FACILITY OPERATING LICENSE NO. DPR-39 AND AMENDMENT NO.139 TO FACILITY OPERATING LICENSE NO. DPR-48 r

COMMONWEALTH EDIS0N COMPANY l

ZION NUCLEAR POWER STATION. UNITS I AND 2 DOCKET NOS. 50-295 AND 50-304 l

l.0 INTRODUCTION On June 25, 1990, Generic Letter (GL) 90-06 was issued. The G represented the technical resolution of Generic Issue 70, " Power-Operated Relief Valve and l

Block Valve Reliability," and Generic Issue 94, " Additional Low-Temperature l

Overpressure Protection for Light Water Reactors." The resolution of these l

issues proposed new requirements and Technical Specification (TS) changes that would enhance the reliability of power-operated relief valves (PORVs) and block valves along with TS changes that would provide additional low-temperature overpressure protection (LTOP).

Genuic Issue 70, " Power-0perated Relief Valve and Block Valve Reliability,"

involves the evaluation of the reliability of PORVs and block valves and their safety significance in PWR plants. The GL discussed the increasing reliance on PORVs to perform safety related functions and the corresponding need to improve the reliability of both PORVs and their associated block valves.

i Proposed staff positions and improvements to the plant's TS were recommended l

to be implemented at all affected facilities. This issue is applicable to all Westinghouse, Babcock & Wilcox, and Combustion Engineering designed facilities with PORVs.

Generic Issue 94, " Additional Low-Temperature Overpressure Protection for Light Water Reactors," addresses concerns with the implementation of the requirements set forth in the resolution of Unresolved Safety Issue (USI)

A-26, "Reacter Vessel Pressure Transient Protection (Overpressure Protection)." The GL discussed the continuing occerrence of overpressure events and the need to further restrict the allowed outage time (A0T) for a low temperature overpressure protection (LTOP) channel in operating modes 4, 5 and 6.

This issue is only applicable to Westinghouse and Combustion Engineering facilities.

By letter dated July 8,1992, Commonwealth Edison Company (CECO, the licensee) proposed an amendment to the Zion Nuclear Power Station TS to address the concerns of Generic Letter (GL) 90-06 relative to PORVs and LTOP. Several editorial changes were also proposed.

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4. The proposed changes will ensure Zion satisfies the intent of GL 90-06, which is to enhance the reliability of PORVs and block valves and provide additional LTOP. These changes resolve Generic Issues 70 and 94. The proposed changes to TS 3/4.3.1.F satisfy the intent of the GL with respect to PORV operability requirements in Modes 1, 2, and 3.

The proposed changes to TS 3/4.3.2.G satisfy the intent of the GL with respect to LTOP requirements in Modes 4, 5 and 6.

?.0 EVALUATION 2.1 EVALUATION FOR GENERIC ISSUE 70 The actions proposed by the staff to improve the reliability of PORVs and block valves represent a substantial increase in overall protection of the public health and safety and a determination has been made that the attendant costs are justified in vicw of this increased protection. The technical findings and the regulatory analysis related to Generic Issue 70 are discussed i

in NUREG-1316, " Technical Findings and Regulatory Analysis Related to Generic Issue 70 - Evabation of Power Operated Relief Valve Reliability in PWR Nuclear Power Plants."

Technical Soecifications Section 3/4.3.1.F The proposed changes to the Limiting Conditions for Operation (LCO) add the specific failure mechanism of excessive seat leakage to the TS.

It requires that with one or both PORVs inoperable due to excessive seat leakage, either restore the PORV(s) to operable status within I hour, or the associated block valve must be closed to isolate the PORV, with power maintained to the block valve.

If these actions are not followed, the reactor must be in Mode 3 within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and in Mode 4 within the following 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months .

If a PORV is inoperable for a reason other than excessive seat leakage, within l

I hour, the valve must be restored to operable status or its block valve shut and power removed. The PORV must be restored to operable status within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months or the reactor must be placed in Mode 3 within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and in Mode 4 within the following 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months .

If both PORVs are inoperable due to causes other than excessive seat leakage, within I hour, one PORY must be restored to operable status or the associated block valves must be closed with power removed and the reactor placed in Mode 3 within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and in Mode 4 within the following 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months .

If one or both block valves are inoperable, within I hour, the block valve (s) must be restored to operable status or its associated PORV(s) must be verified closed with power removed.

If both block valves are inoperable, at least one block valve must be restored to operable status within the next hour; any remaining inoperable block valves must be restored to operable status within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months ; otherwise, the reactor must be placed in at least Mode 3 within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and in Mode 4 within the following 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months .

In these proposed LCOs, Zion's submittal differs from the guidance in the GL in that the GL requires the reactor to be placed in Mode 3 within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and Mode 4 within the following 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months . The licensee justified this difference

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l by saying the additional 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months are necessary because TS Table 3.4-1 specifies that P-12, the manual block permissive which is used to block the i

High Steam Line Differential Pressure actuation of the Engineered Safeguards Actuation System Safety Injection signal, may only be activated if the reactor coolant system (RCS) is borated to greater than cold shutdown conditions.

This manual block must be activated before the plant is cooled below 540 degrees Fahrenheit. The additional 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months to reach Mode 4 allows-for boration of the RCS, adequate time to ensure proper mixing and time to draw and analyze a sample.

Although the Zion submittal differs from the GL in the time to reach Mode 4,.

the staff has evaluated it and considers that the changes that have been 1

proposed contribute to safer reactor operation.

In the case of a PORV(s) with excessive seat leakage, since it incorporates the provision for operating with-a block valve closed but power still supplied to the valve, the block valve i

can be readily opened from the control room, which means the associated PORV would be available for pressure relief if required. Additionally, reactor '

i operation in Modes 1, 2 and 3 with PORVs and block valves inoperable (for reasons other than seat leakage in the case of'PORVs) would not be permitted for periods of more than 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months . The staff feels that this also contributes to safer operation of the reactor.

The proposed surveillance requirements (SR) ensure that the PORV and block' valve can perform their intended functions.

Present surveillance requirements require only a channel calibration every 18 months. The proposed changes retain this requirement and also clarify that the performance of the channel calibration relates to the actuation equipment. The proposed SRs also require operation of each PORY through one complete cycle of full travel during Modes 3 or 4 and operation of the air control valves and check valves on associated j

air accumulators in the PORV control system through one complete cycle of full travel. The block valves are exempt from the surveillance requirements to 4

cycle the valves when they have been closed to comply with the Action require-ments of 3.3.1.F.

This precludes the need to cycle the valve with full system differential pressure or when maintenance is being performed to restore an inoperable PORV to operable status. Testing of the PORVs in Mode 3 or Mode 4 is required to simulate the temperature and pressure environmental effects on the PORV.

i The staff has reviewed the proposed changes and finds that they increase the reliability and availability of the PORVs, and, therefore, result in an overall increase in the protection of the public health and safety. The proposed changes to the surveillance requirements are, therefore, acceptable.

Additional administrative changes were made that.are editorial in nature and changes consistent with those above were made to the Bases in sections 3.3.1 and 4.3.1.

The administrative changes are editorial in nature and are acceptable.

' 2.2 EVALUATION FOR GENERIC ISSUE 94 The actions proposed by the staff to improve the availability of the LTOP system represents a substantial increase in the overall protection of the public health and safety and a determination has been made that the attendant costs are justified in view of this increased protection. The technical findings and the regulatory analysis related to Generic Issue 94 are discussed in NUREG-1326, " Regulatory Analysis for the Resolution of Generic Issue 94, j

Additional Low-Temperature Overpressure Protection for Light-Water Reactors."

i Technical Specifications Section 3/4.3.2.6 When in Mode 4, current TS 3.3.2.G.a allows 7 days to restore an inoperable PORY to operable status and if this is not accomplished, requires depressuri-zation of the RCS within the next 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . The 7 day LC0 is consistent with the GL. However, the GL guidance requires depressurization of the RCS within the next 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months . The licensee provided a time table for a plant cooldown and depressurization that indicates that 23 hours2.662037e-4 days 0.00639 hours 3.80291e-5 weeks 8.7515e-6 months are required to depressurize from an initial temperature of 250 degrces Fahrenheit in Mode 4 in a reasonable, controlled manner. The licensee further justified the difference by stating that based on the current RCS and pressurizer cooldown rate limits and the physical constraints on the rate at which the pressurizer can be drained, this is the amount of time required.

Although the licensee's current TS is not consistent with the GL, the staff considers it acceptable because of the time required to cooldown and depressurize from 250 degrees Fahrenheit. The difference between the time tabla and the proposed 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months is inconsequential and since the licensee's time table does not include leeway for complications or logistics delays, the 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months is an acceptable LCO.

The proposed change to the LCO for one inoperable PORY in Modes 5 and 6, Action 3.3.2.G.b, allows 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months for the inoperable PORY to be restored to operable condition, and, if the PORV can not be made operable in this period, within the next 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , the RCS must be depressurized. Although the initial 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months period to restore the PORV to operable condition is consistent with the GL, the GL guidance also requires depressurization of the RCS within a total of 32 hours3.703704e-4 days 0.00889 hours 5.291005e-5 weeks 1.2176e-5 months which means the cooldown from 200 degrees Fahrenheit and depressurization would need to be accomplished in 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months . The proposed Zion change would give a total of 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months from the time of discovery of an inoperable PORV until the RCS is depressurized which allows 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months for the cooldown and depressurization.

Although the proposed am;ndment to Action 3.3.2.G.b is not totally consistent with the GL, it represents a substantial improvement over the current TS, which allows the same 7 day A0T for Modes 4, 5 and 6.

Hence, in Modes 5 and 6, current T3 allow 7 days with an inoperable PORV and an additional 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months in which to depressurize the RCS. The licensee provided a time table for a plant cooldown and depressurization from Modes 5 and 6 that shows that 22 hours2.546296e-4 days 0.00611 hours 3.637566e-5 weeks 8.371e-6 months are required. The licensee further justifies the difference by stating that based on the current RCS and pressurizer cooldown rate limits and the physical constraints on the rate at which the pressurizer can be drained, this

oe l 1 is the amount of time required. The staff finds the difference from the GL to be acceptable since it is a substantial decrease of the A0T from that in the current TS, and hence is an appreciable increase in. safety while in Modes 5 l

and 6.

The difference between the time table and the proposed 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months is inconsequential and since the licensee's time table does not int:1ude leeway for complications or logistics delays, the 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months is an acceptable LCO.

The proposed change to the LC0 for two inoperable PORVs in Action 3.3.2.G.c increases the time allowed to depressurize the RCS from 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months to 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months .

This differs from the guidance in the GL, which allows 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months for the depressurization. The licensee justifies the difference by stating that based on the current RCS and pressurizer cooldown limits and the physical constraints on the rate at which the pressurizer can be drained, the specified actions to depressurize the RCS can not be completed in 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months , and, therefore, not in 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months . The licensee estimates that the required conditions can be established in 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months .

The staff has reviewed the licensee's proposal and finds that although 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months for depressurization would be more desirable, the metallurgical limits on cooldown and the i

practical time limits to drain the pressurizer are sufficient for it to concur in a requirement that is different from the guidance in the GL. The licensee's proposed change to Action 3.3.2.G.c is, therefore, acceptable.

The licensee's proposed change to Surveillance Requirement (SR) 4.3.2.G.I.a.1 changes the current TS to specifically exclude valve operation from the Channel Functional Test. This is consistent with the GL guidance, and is, therefore, acceptable.

Additional administrative changes were made that are editorial in nature and changes consistent with those above were made to the Bases for sections 3.2.2.G and 4.2.2.G.

These changes are administrative in nature and are acceptable.

The staff has reviewed the licensee's proposed modifications to the Zion TS.

Although not all the changes are consistent with the guidance in Generic Letter 90-06, taken overall, they represent a substantial increase in safety by providing greater assurance that PORVs and LTOP will be available if required. The staff, therefore, finds the proposed modifications to the TS to be acceptable.

3.0 STATE CONSULTATION

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

4.0 ENVIRONMENTAL CONSIDERATION

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The amendments change 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 change surveillance requirements. The NRC staff has determined I

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I that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may bc released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a l

proposed finding that the amendments involve no significant hazards consideration, and there has been no public coment on such finding (57 FR 40209). Accordingly, the amendments meet the eligibility criteria for i

1 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 amendments.

5.0 CONCLUSION

I The Comission 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, i

and (3) the issuance of the amendments will not be inimical to the common i

defense and security or to the health and safety of the public.

Principal Contributor: Clyde Shiraki 3

Date: November 29, 1993 I

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ML20058G298

Contents

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3.0 STATE CONSULTATION

4.0 ENVIRONMENTAL CONSIDERATION

5.0 CONCLUSION

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ML20058G298

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3.0 STATE CONSULTATION

4.0 ENVIRONMENTAL CONSIDERATION

5.0 CONCLUSION

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