ML19326C190
| ML19326C190 | |
| Person / Time | |
|---|---|
| Site: | Oconee, Arkansas Nuclear, Rancho Seco, McGuire, Crane  |
| Issue date: | 11/15/1976 |
| From: | Zech G Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19326C185 | List: |
| References | |
| NUDOCS 8004210681 | |
| Download: ML19326C190 (4) | |
Text
O ENCLOSURE 2 4
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UNITED STATES NUCLEAR REGULATORY COMMISSION y
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WASHINGTON, D. C. 20555 i
NOV 151976 00CKETS NOS.: 50-313, 50-289, 50-312, 50-269, 50-270, and 50-287 LICENSEE / FACILITY: Arkansas Power & Light Co. (Arkansas Nuclear Unit One, Unit 1)
Metropolitan Edison Co. (Three Mile Island, Unit 1)
Sacramento Municipal Utility District (Rancho Seco)
Duke Power Company (0conee, Units 1, 2 & 3)
SUMMARY
OF MEETING HELD ON NOVEMBER 5, 1976, CONCERNING PROPOSED MEASURES TO PREVENT REACTOR VESSEL OVERPRESSURIZATION IN OPERATING BABC0CK &
WILC0X (PWR) FACILITIES On November 5,1976, the staff met with representatives of PWR licensees with Babcock & Wilcox (B&W) designed plants to discuss measures being taken to prevent reactor vessel overpressurization.
A list of attendees is enclosed.
Significant discussions are sumarized below.
We summarized the correspondence and discussions that had occurred with the B&W licensees since our generic letter on reactor vessel overpressurization was issued in August 1976. We acknowledged that three of the four licensees had responded with the submittals requested in the generic letter and that the submittals included a description of certain design features that provided some degree of protection against reactor vessel overpressurization.
However, we indicated the need to discuss the details of these design features
' further and to determine if all potential pressure transients had been considered.
The staff iridicated that the below listed design criteria should be included in that equipment intended to provide overpressurization protection:
1.
Credit for Operator Action - No credit can be taken for operator action until 10 minutes after the ' operator is aware that a pressure transient is in progress.
2.
Single Failure Criteria - The pressure protection system should be designed to protect the vessel given a single failure in addition to a failure that initiates the pressure transient.
In this area, redundent or diverse pressure protection systems would be considered as meeting the single failure criteria.
3.
Testability - The equipment design should include some provision for testing on a schedule consistent with the frequency that the system is used for pressure protection.
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8004210
a NOV j. 51976
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- 4.. Seismic Design and IEEE 279 Criteria - Ideally, the pressure protective system should meet both seismic Cat 1 and IEEE 279 criteria. The basic objective however, is that the system should not be vulnerable to an event which both causes a pressure transient and causes a failure of equipment needed to terminate the transient.
The licensee emphasized the fact that none of the B&W plants ever go water-solid, even when shutdown, in that the pressurizer steam bubble is replaced with a low-pressure (35 to 50 psig) nitrogen gas bubble when the plant is cooled down.
In addition, the B&W plant design already includes a dual setpoint feature on the pressurizer power operated relief valve.
The lower setpoint of 500 psig is selected whenever the plant is shutdown and cooled down to provide overpressure protection for the Reactor Coolant System (RCS).
Rancho Seco, however, indicated that its power operated relief valve is also used during normal plant operation as an aid in the contrc' of reactor coolant boron concentration. As a result of this use, the licensee indicated that during plant shutdown the valve has required maintenance and would therefore not be available for overpressure protection. We requested that Rancho Seco provide further details on the maintenance program for this valve.
With reference to the single failure criteria, we discussed the possibility of an overpressurization event occurring in those situations where adminis-trative measures would be used such as removal of power from the circuit breakers of valves or hign pressure pumps. The licensee agreed to study this further and will provide a more detailed discussion of this type of control.
We requested that the licensees and BaW provide a transient analysis of the RCS response to a single High Pressure Injection Pump and a Core Flood Tank discharge.
The licensees agreed to study the possibility of limiting the volume of water in the RCS Makeup Tank such that the pressurizer would not go water-solid if the Makeup Control Valve should fail full open.
The licensees agreed to provide additional information regarding how they
-intend to meet the above described design criteria.
In those instances where deviation from the criteria might be involved, the licensees are to provide detailed justification including the technical basis for not meeting the criteria and, where significant, the impact on the schedule for implementation.
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- NOV 151976 Arkansas Power & Light Company representatives agreed to submit their analysis and proposed methods to provide pressure protection by December 3, 1976. They indicated that they now operate with a nitrogen bubble in the pressurizer when shutdown, as do the other B&W licensees.
Regarding the additional infomation requested in the meeting', all B&W licensees are to provide responses upon receipt of the additional transient analyses from Babcock & Wilcox. These analyses are estimated to require approximately 30 days to prepare.
We agreed to send each licensee a letter describing the information requested.
D Gary G. Zech, Project Manager Operating Reactors Branch #1 Division of Operating Reactors
Enclosure:
List of Attendees cc w/ encl:
See next page O
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NRC STAFF MEETING WITH BABCOCK & WILCOX PWR LICENSEES NOVEMBER 5, 1976 ATTENDANCE LIST NRC Arkansas Power & Light Co.
G. G. Zech R. Cook R. L. Baer G. R. Young C. H. Berlinger G. Lanik Sacramento Municipal Utility Dist.
L. B. Marsh J. D. Neighbors P. Oubre' J. A. Dyer R. A. Dieterich R. E. Martin D. M. Verre111 Duke Power Company R. P. Snaider W. E. Converse D. C. Holt J. E. Ouzts T. E. Crawford F. Clemenson E. D. Blakeman R. M. Gamble G. R. Mazetis Metropolitan Edison Com.
G. B. Swetzig V. Rooney D. Huffman F. Orr J. J. Moran R. Wright (ACRS)
Florida Power Corp.
Bechtel B. Simpson E. J. Ray Babcock & Wilcox J. Merchant W. J. Keyworth D. G. Newton NOV 15 B76