ML17332A392

Safety Evaluation Supporting Amends 184 & 169 to Licenses DPR-58 & DPR-74,respectively

ML17332A392
Person / Time
Site:	Cook
Issue date:	11/08/1994
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML17332A390	List: ML17332A389 ML17332A392
References
NUDOCS 9411150611
Download: ML17332A392 (7)

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1. 0 INTRODUCTION By letter dated November 12, 1993, the Indiana Hichigan Power Company (the licensee) requested amendments to the Technical Specifications (TS) appended to Facility Operating License Nos.

OPR-58 and DPR-74 for the Donald C. Cook Nuclear Plant, Unit Nos.

1 and 2.

The proposed amendments would revise TS 3/4.5. 1 which addresses the emergency core cooling system (ECCS) accumulators.

The action statements would be revised to provide one action for an accumulator boron concentration outside TS limits, and a second action For all other inoperabilities.

Currently the action statements provide one action for a closed isolation valve and another action for all other inoperabilities.

In addition, the current action statements differ for each unit.

The proposed change would make the actions consistent.

The surveillance requirements are also proposed to be changed.

First, the requirement is changed to require verification of accumulator boron concentration only after a water addition from other than the refueling water storage tank (RWST) rather than after any water addition.

Second, the 18-month verification that the isolation valve opens upon receipt of a safety injection (SI) signal is to be deleted.

Finally, consistent changes to the Bases are also proposed.

2.

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~Il The functions of the ECCS accumulators are to supply water to the reactor vessel during the blowdown phase of a loss-of-coolant accident (LOCA), to provide inventory to help accomplish the refill phase that follows thereafter, and to provide reactor coolant system (RCS) makeup for' small break LOCA.

The accumulators are pressure vessels partially filled with borated water and pressurized with nitrogen gas.

The accumulators are passive components, since no operator or control actions are required in order for them to perform their function.

Internal accumulator tank pressure is sufficient to discharge the accumulator contents to the RCS, if RCS pressure decreases below the accumulator pressure of 620 psig.

9+111ioi11 9411aS PDR ADOCK 05000315 P

PDR Each accumulator is piped into an RCS cold leg via a 10-inch accumulator line and is isolated from the RCS by a motor-operated isolation valve and two check valves in series.

The motor-operated isolation valves are interlocked with the pressurizer measurement channels to ensure that the valves will automatically open as RCS pressure increases to above the setpoint.

The interlock also prevents inadvertent closure of the valves during normal operation prior to an accident.

The valves will automatically open,

however, as a result of an SI signal.

These features ensure that the accumulators will be available for injection without reliance on operator action.

The accumulator

size, water

volume, and nitrogen cover pressure are sized so that three of the four accumulators are sufficient to partially cover the core before significant clad melting or zirconium water reaction can occur following a LOCA.

The need to ensure that three accumulators are adequate for this function is consistent with the LOCA assumption that the entire contents of one accumulator will be lost via the RCS pipe break during the blowdown phase of the LOCA.

U The proposed change to the action requirements would correct an inconsistency in the present TS.

The Accumulator TS is applicable in Nodes 1, 2, and 3 with pressurizer pressure above 1000 psig.

However, the present action statement requires, if the inoperability cannot be corrected in the required timeframe, that the unit be taken to Node 4 (Hot Shutdown).

Yet simply reducing the unit to Mode 3 with pressurizer pressure less than 1000 psig would place the unit in a condition where the Accumulator TS is not applicable.

Therefore, the licensee has proposed that the TS action statements be revised such that the end point of the action is Node 3 with pressurizer pressure less that 1000 psig.

Since this is consistent with the applicability conditions, the staff finds the change acceptable.

The licensee has proposed to create a new action statement for accumulator boron concentration being outside the TS limit.

This action statement would allow 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to restore the boron concentration to within the required limits or go to Node 3 within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and reduce pressurizer pressure to less or equal to 1000 psig within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

The staff has previously addressed these proposed action requirements in the improved "Standard Technical Specification - Westinghouse Plants,"

NUREG-1431, September 1992.

Specifically, the boron in the accumulators contributes to the assumption that the combined ECCS water in the partially recovered core during the early reflooding phase of a large break LOCA is sufficient to keep that portion of the core subcritical.

One accumulator below the minimum boron concentration limit, however, will have no effect on available ECCS water and an insignificant effect on core subcriticality during reflood.

Boiling of KCCS water in the core during reflood concentrates boron in the saturated liquid that remains in the core.

In addition, current analysis techniques demonstrate that the accumulators do not discharge following a large main steam line break for the majority of plants.

Even if they do discharge, their impact is minor and not a design limiting event.

Therefore, the staff considers ihe extended action requirements for boron concentration outside the limits to be acceptable.

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The licensee has also proposed a revised second action statement to address an accumulator inoperable for any reason other than boron concentration not

, within limits.

This action, which would allow 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to correct the inoperablity or go to Node 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and reduce pressurizer pressure within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, is generally consistent with the current TS except for the case of a closed isolation valve.

The current TS, for a closed isolation valve, requires immediate action to open the valve.

Although this revised action would allow greater time to open an isolation valve than the current TS, it would be consistent with the actions in the iSTS and provides a

minimal time for valve restoration which may limit plant transients.

As stated in the fSTS, "the allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systeis.

and, "[t]he Completion Time minimizes the potential for exposure of the plant to a LOCA under these conditions."

In addition, the revised action, although consistent with the current Unit 2 action which allows 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to reach Hot

Shutdown, allows greater time than the current Unit 1 action requirement of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to reach Hot Shutdown.

This change is also consistent with the iSTS and provides consistency between the units.

Based on the above, the staff considers the replacement of the current action requirements with the proposed action statement to be acceptable.

An editorial change is proposed to Unit 1 surveillance requirement 4.5. I.a. 1.

This change would replace "water level" with "contained borated water volume."

The term "contained borated water volume" more accurately describes the item to be checked, is consistent with the Cook Unit 2 TS and with the fSTS.

The staff considers this proposed change to be acceptable.

The licensee has proposed to revise surveillance requirement 4.5.1.b. to specify that the verification of boron concentration, performed after a volume increase of greater than or equal to IX, is only done on the affected accumulator(s) and only when the addition came from a source other than the

&ST.

The portion of 4.5. l.b which requires verification of boron

,concentration in the accumulators every 31 days remains unchanged.

The first

change, which would specify that only the accumulator which had a volume addition need be checked, clarifies the intent of that part of the surveillance.

For the accumulators without a volume adjustment, the normal 31-day surveillance is sufficient.

There is no interconnection between the accumulators so a volume change to one will not affect the others.

The proposed change is consistent with the iSTS, clarifies the intent and is therefore, acceptable.

The second part of the change would only require boron concentration verification when the addition is made from a source other than

%he RWST.

Cook TS 3/4. 1.2.8 and 3/4.5.5 require an identical boron concentration for the RWST as for the accumulators during power operation.

Therefore, the addition of water to an accumulator from the RWST would not pose a potential dilution problem.

This aspect was previously noted by the staff in the development of the iSTS and the licensees proposal is consistent with the iSTS.

Based on the above, the proposed change is acceptable.

The deletion of TS surveillance 4.5. l.d is also proposed.

Currently, this surveillance requires verifying each 18 months that each accumulator isolation valve vill open upon a SI signal.

Existing TS 4.5. l.a.2. requires

verification every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> that each accumulator isolation valve is open, and TS 4.5.l.c. requires verification every 31 days when RCS pressure is ab'ove 2000 psig, that power is removed from the isolation valve operator.

These two surveillances provide adequate assurance that the isolation valves will remain open during power operation.

Therefore, the verification that the valve will open upon a safety injection signal is redundant and unnecessary.

The staff previously considered the necessity for this surveillance and removed it from the iSTS for these reasons.

Based on the above, the staff considers the deletion of TS surveillance 4.5. I.d to be acceptable.

The licensee has also proposed certain changes to the Bases which support the above changes and are, therefore, acceptable.

4.0 STATE CONSULTATION

In accordance with the Commission's regulations, the Nichigan State official was notified of the proposed issuance of the amendments.

The State official had no comments.

5. 0 ENVIRONMENTAL CONSIDERATION The amendments change the requirements with respect to the installation or use Df a faci'lity component located within the restricted area as defined in 10 CFR Part 20.

The staff has determined that the amendments involve 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 amendments involve no significant hazards consideration and there has been no public comment on such finding (58 FR 67848).

Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 3].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.

6. 0 CONCLUSION The staff has concluded, based on the considerations discussed above, that:

(I) 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 amendments will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor:

John B. Hickman, NRR Date:

November 8, 1994

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