B11747, Forwards Review of Integrated Safety Assessment Program Topic 1.25, Degraded Grid Voltage Procedures, Resulting from Review of SEP Topics VIII-1.A & VII-3 Per 850517 Commitment

Forwards Review of Integrated Safety Assessment Program Topic 1.25, Degraded Grid Voltage Procedures, Resulting from Review of SEP Topics VIII-1.A & VII-3 Per 850517 Commitment

ML20138J563
Person / Time
Site:	Millstone
Issue date:	10/09/1985
From:	Opeka J, Sears C NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	Charemagne Grimes Office of Nuclear Reactor Regulation
Shared Package
ML20138J567	List: B11747, Forwards Review of Integrated Safety Assessment Program Topic 1.25, Degraded Grid Voltage Procedures, Resulting from Review of SEP Topics VIII-1.A & VII-3 Per 850517 Commitment ML20138J571 ML20138J575 ML20138J582
References
TASK-07-03, TASK-08-01.A, TASK-7-3, TASK-8-1.A, TASK-RR B11747, NUDOCS 8510290388
Download: ML20138J563 (8)

Text

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N UTILITIES '

General Offices e Selden Street, Berlin, Connecticut

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J 5 0;0"l'.".%'"_ (2m) ses-som October 9,1985 Docket No. 50-245 B11747 Director of Nuclear Reactor Regulation Attn: Mr. Christopher I. Grimes, Chief Systematic Evaluation Program Brarch U. S. Nuclear Regulatory Commission Washington, D.C. 20555

References:

(1) 3. F. Opeka letter to C. I. Grimes, dated May 17,1985.

(2) H. L. Thompson letter to 3. F. Opeka, dated July 31,1985.

Gentlemen:

Millstone Nuclear Power Station, Unit No.1 Integrated Safety Assessment Program In Reference (1), Northeast Nuclear Energy Company (NNECO) provided a proposed scope for the Integrated Safety Assessment Program (ISAP) review of Millstone Unit No.1. In Reference (2), the Staff formally issued the results of the ISAP screening review process, establishing the scope of ISAP for Millstone Unit No. I and initiating issue-specific evaluations. Reference (1) also indicated that for each issue or topic included in ISAP, NNECO would provide a discussion of the safety objective and an evaluation of the plant design with respect to the issue being addressed to identify specific terms to be considerd in the integrated assessment. In accordance with this commitment, the review for the following ISAP topic is attached.

o ISAP Topic 1.25 " Degraded Grid Voltage Procedures" We note that ISAP Topic 1.23, " Grid Separation Procedures" address the same issue as Topic 1.25. ISAP Topic 1.23 resulted from the review of SEP Topic VIII-1.A, " Potential Equipment Failures Associated with a Degraded Grid Voltage",

while Topic 1.25 resulted from the NRC's review of multi-plant action MPA B-

23. The safety evaluation for SEP Topic VIII-1.A specifically referenced MPA B-23 and the Staff's review of this issue for Millstone Unit 1, noting the direct relationship between the grid separation procedures and the SEP Topic VII-3 Safe Shutdown review. Thus, it appears as though ISAP Topics 1.23 and 1.25 address the same issue, and both are addressed by the attached review.

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If you have any questions concerning the attached review, please contact us.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY b k.D '

J. F. Opeka Senior Vice President By C. F. Sears Vice President cc: 3. A. Zwolinski l

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ISAP TOPIC 1.25 DEGRADED GRID VOLTAGE PROCEDURES

I. Introduction General Design Criterion (GDC) 17 of Appendix A to 10CFR50 requires an on-site and off-site electric power . system _ to be provided to permit functioning of structures, systems, and components important to safety.

The on-site AC Class IE electric power system is supplied power by either the offsite transmission grid _ or the on-site standby emergency diesel generators. During normal plant operation, the Class IE buses are supplied power by the. transmission grid. If the grid voltage were to degrade and become low enough so that the voltage at the Class IE equipment is less than its qualified operating voltage, equipment damage could occur. On June -2,1977, NNECO was requested by the NRC to address this issue

- (Reference 1). As discussed in the Integrated Plant Safety Assessment Report (Reference 6), under nonaccident conditions, a degraded grid E voltage condition requires operator action to prevent damage to Class IE systems. The NRC concluded that sufficient time and appropriate alarms and Indications are available _ at Millstone Unit No. I so that operator action is acceptable. The purpose.of ISAP Topic 1.25 is to provide the L .NRC with degraded grid voltage procedures, which define operator actions

!- during such conditions.

II. - Review Criteria 10CFR50, Appendix A, General Design Criterion 17 -

Regulatory Guide 1.93 III.' Related Topics / Interface ISAP Topic 1.23 - Grid Separation Procedures IV. - Evaluation As previously stated, on June 2,1977 (Reference 1), NNECO was requested by the NRC to address the issue of degraded grid voltage for Millstone Unit No. l.- In .a subsequent letter to NNECO, dated November- 24, 1981 (Reference 2), the NRC indicated that their review of degraded grid voltage protection for Millstone Unit No. I was ongoing, and additional information was requested concerning operator training and plant operating procedures instituted to ensure prompt and appropriate decisions regarding

. this issue. NNECO provided the requested information to the NRC in a letter dated April 21,1982 (Reference 3).

On June 23,1982.(Reference 4), the NRC issued its Safety Evaluation Report for degraded grid protection at Millstone Unit No.1. As a result of the NRC's review of Millstone Unit No.1, certain design modifications were required. NNECO committed to provide the NRC with degraded grid voltage procedures reflecting the requisite design modifications, once completed (Reference 7). These design modifications were to be completed during the 1984 refueling outage; however, vendor-related difficulties necessitated postponement of the plant modifications

' (Reference 10) until the 1985 refueling outage. In view of this

. postponement, NNECO committed to implement interim degraded grid voltage procedures pending completion of the Millstone Unit No. I design modifications -(Reference 10) and further committed to submit these interim procedures for NRC review (Reference 11).

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The attachment to this Topic provides the interim degraded grid voltage procedures for Millstone Unit No.1. Specifically, the following procedures are provided:

Annunciator Alarm and Response Procedures 230-721 230-756 230-757 230-996 230-997 Operating Procedures 340 (24 KV Level) 341 (4 KV Level) 342A (480V Level)

These procedures have been grouped in the attachment as follows:

o Final 480V Under/Over Voltage Alarm and Final Operating Procederes (OP342A) o 4 KV Bus Interim Undervoltage Alarm and Operating Procedures (OP341) o Reserve Station Service Transformer (RSST) Interim Undervoltage Alarm and Operating Procedures (OP340)

Note that the 480V Under/Over Voltage Alarm and Operating Procedures are final since there are no automatic trip circuits which will be tied to these alarm relays as part of the 1985 refueling outage design modifications. The procedure intent of OP340 will be provided in OP341 once the final design changes are made, e

V. Conclusions As communicated to the NRC (References 7 and 10), NNECO currently intends to complete the following design modifications during the 1985 refueling outage. It is noted that these modifications are undergoing additional review using the recently completed plant-specific PSS. If the results of this review identify the need for changes to the modifications summarized below, you will be so advised in future correspondence.

o Relocate the loss of voltage and degraded voltage protection to the 4.16 KV Class IE buses; o Split the Loss of Normal Power (LNP)into two divisions; and o Provide an automatic reinstatement of the bus load-shed feature in the event of an on-site emergency power supply trip.

Once the above design changes are complete, NNECO intends to finalize the attached interim degraded grid voltage procedures. Until such time as these procedures are finalized, NNECO believes that the attached interim procedures provide technically acceptable means for defining operator actions during degraded grid voltage conditions without concurrent LOCA conditions.

VI. References

1. G. Lear letter to D. C. Switzer, dated June 2,1977.

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2. D. M. Crutchfield letter to W. G. Counsil, dated November 24,1981.

3. W. G. Counsil letter to D. M. Crutchfield, dated April 21, 1982.

4. D. M. Crutchfield letter to W. G. Counsil, dated June 23,1982.

5. 3. Shea letter to W. G. Counsil, dated June 30,1982.

6. Integrated Plant Safety Assessment, NUREG-0824, Millstone Nuclear Power Station, Unit No.1, Final Report, February 1983.

7. W. G. Counsil letter to D. M. Crutchfield, dated January 17, 1984.

8. W. G. Counsil letter to D. M. Crutchfield, dated April 26,1984.

9. 3. R. Miller letter to W. G. Counsil, dated April 27,1984.

10. W. G. Counsil letter to D. M. Crutchfield, dated May 11, 1984.

11. W. G. Counsil letter to 3. R. Miller, dated June 11,1984.

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Docket No. 50-245 Attachment Millstone Nuclear Power Station, Unit No.1 Interim Degraded Grid Voltage Procedures October 1985

Millstone Nuclear Power Station, Unit No. I Under/Over Voltage Alarm and Operating Procedures 1