ML20003H707
| ML20003H707 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 05/01/1981 |
| From: | Kay J YANKEE ATOMIC ELECTRIC CO. |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| FYR-81-69, NUDOCS 8105070296 | |
| Download: ML20003H707 (4) | |
Text
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YANKEE ATO.3?D ELECTRIC COMPANY
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1671 Worcester Road, Framingham, Massachusetts 01701 YYR 81~69 YAmuss May 1, 1981 United States Nuclear Regulatory Commission Washington, D.C. 20555 Attention:
Office of Nuclear Reactor Regulation Mr. Dennis M. Crutchfield, Chief Operating Reactors, Branch #5 Division of Licensing
References:
(1) License No. DPR-3 (Docket No. 50-29)
(2) USNRC Letter to YAEC dated 6/3/77 (3) USNRC Letter to YAEC dated 10/16/79 (4) YAEC Letter to USNRC dated 7/18/77 (WYR 77-67)
(5) VYNPC Letter to USNRC dated 12/6/79 (WVY 79-139)
(6) YAEC Letter to USNRC dated 7/24/80 (WYR 80-83)
(7) USNRC Letter to YAEC dated 10/2/80
Subject:
Mitigating the Effects of Grid Degradation on Safety-Related Electrical Equipment.
Dear Sir:
In Reference (6) YAEC proposed to adopt a scheme to mitigate the effects of grid degradation on safety-related electrical equipment. This scheme was developed as an alternative to both the NRC's generic position (References 2, 3), and the Yankee Atomic Electric position (References 4, 5) on degraded grid voltage protection. This alte native scheme was originally suggested by the NRC and carefully analyzed by ' ankee Atomic; the alternative was presented to the NRC as Reference (6) and engineering commenced immediately.
We believed we had a mutual understanding which assumed that the alternative scheme would stand on its own merits and would replace in its entirety both the NRC's generic position as well as the Yankee Atomic position; therefore, it came as a surprise to receive Reference (7) from the NRC stating that the proposed alternative described in Reference (6) was not in full compliance with four requirements of the NRC-generic position of Reference (2).
Listed below are Yankee 's responses to the four NRC staff positions identified in Reference (7).
P 810 5 070 2(QG
U.S. Nucisci R2gulstory Cosmiccien May 1, 1981 Attention:
Mr. Dennis M. Crutchfield Page 2 1
1.
Staff Position Staff Position 1 of Reference (2) requires coincident logic in the voltage protection scheme to preclude spurious trips of the offsite power source. The proposed logic in Reference (6) does not prealude spurious trip of offsite source in all cases and, therefore, the required coincident logic should be provided in accordance with Table 3.3-3 in of Reference (2).
YAEC Response YAEC proposes to modify its design to include coincident logic. Two second level undervoltage relays will be added to each safety bus. Each second level undervoltage relay will be supplied from an independent instrument transformer. The circuit breaker connecting offsite power to the emergency bus is shown in Figure 1 (typical). The first level undervoltage relays are shown as device 27A-1 and 27A-2.
The second level undervoltage relays are shown as device 27B-1 and 27B-2.
When voltage is degraded below ~ st required to ensure continued operation of safety-related eq 2nt, the second level undervoltage relays 27B-1 and 27B-2 will be civated. Contacts of the second level undervoltage relays will close in the breaker trip circuit as well as in the alarm circuit. The contacts in the breaker trip circuit are arranged to provide 2 out of 2 coincident logic and the breaker will trip automatically if an accident signal is also received. The contacts in the alarm circuit are arranged to provide 1 out of 2 coincident logic.
2.
Staff Postition Staff Position 1 of Reference (2) also required Technical Specification changes including limiting conditions for operation, surveillance, trip setpoints with minimum and maximum limits, and allowable values for second level voltage protection monitors. The required changes to the Technical Specifications should be submitted in accordance with Tables 3.3-3, 3.3-4 and 4.3-2 in Enclosure 2 of Reference (2).
Yankee Response Technical Specifications will be changed to meet the requirements of this staff position and will be submitted according the the Schedule section of this letter.
3.
Staff Position l
Staff Position 2 of Reference (2) requires that load shedding on the emergency buses be prevented from occurring when the diesel generator is supplying power to all the sequenced loads and that the load shedding feature be reinstated automatically when the diesel generator circuit breaker is tripped. Reference (4) indicates that there is an automatic l
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U.S. Nucloor R:gulatory Cosmicalen May 1, 1981 Att;ntica:
Mr. Dennio M. Crutchfisld Peg 2 3 s
bypass of the load shedding feature when the diesel generator circuit breaker is closed, however, the reinstatement of the f eature is not provided. The bypassing of a protective function (i.e., load shedding should meet the requirements of IEEE 279-1971 paragraph 4.12 by removing the bypass automatically whenever the permissive condition (i.e. diesel generator breaker closed) is not met.
The licensee should revise its design to meet these requirements.
Yankee Response In Reference (4) Yankee Atomic objected 'to compliance with reinstating the load shedding f eature because we believed this was an arbitrary requirement over and above the ground rules established by NRC's General Design Criteria for Nuclear Power Plants, as well as one which has not been assumed in the accident analysis of any station. Though Yankee Atomic's position remains unchr.nged by the above NRC arguments, we shall comply with this staff position.
4.
Staff Position Staff position 3(b) Reference (2).equires that the diesel generators operate for at least five minutes while loaded with the emergency loads.
The licensee should submit Technical Specification changes to include this requirement.
Yankee Response Yankee Rowe technical specification 4.8.1.1.2.d seets the above requirement.
PROPOSED ACTION AND SCHEDUII:
Engineering will proceed upon receipt of NRC approval. The modification will be installed at the first opportune shutdown following completion of engineering and receipt of materials. Technical specification changes will be submitted for approval prior to completion of the modification installation.
Technical specification changes will become effective upon completion of the modification.
l Very truly yours, YAhTEE ATOMIC ELECTRIC COMPANY J. A. Kay Senior Engineer - Licensing
FIGURE I
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SCHEMATIC REPRESENTATION OF OFFSITE PCWER CIRCUIT BREAKER TRIP CIRCUlT
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