ML20052B936
| ML20052B936 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 03/12/1982 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20052B932 | List: |
| References | |
| NUDOCS 8205040161 | |
| Download: ML20052B936 (2) | |
Text
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[o UNITED STATES g
NUCLEAR REGULATORY COMMISSION 5
.p WASHINGTON, D. C. 20555 l
,o$
SAFETY EVALUATION OF PROPOSED l
MODIFICATION OF THE MAINE YANKEE SAFETY _
INJECTION LOGIC INTRODUCTION:
29, 1982, Confirmatory Action Letter 82-01 was sent By letter dated Januaryto Maine Yankee Atomic Power Company (licensee) by Ronald C.r This letter noted that on January 28, 1982 Administrator, USNRC Region 1.
it had been found that the automatic safety injection logic for Maine Yankee did not satisfy the Commission regulations with regard to single failure l
Items 1 and 2 of Confirmatory Action Letter 82-01 required that criterion.
the licensee propose design changes to address the single failure concern.
In accordance with Task Interface Agreement No. 82-2 the NRC's Office of Nuclear Reactor Regulation has reviewed the licensee's proposed design change.
BACKGROUND:
Safety injection at Maine Yankee is actuated on low pressurizer pressure and Four measurement channels are provided for on high containment pressure. Redundant trains (A & B) of output are provided to actuate each parameter.
The safety injection equipment to perform the required safety function.
logic matrix which combines the sensing channels to produce safety injection initiation based on a trip of any two of the four sensing channels was implemented High containment pressure was by a single logic circuit for each parameter.a two-out-of-four A train logic and lo Therefore the design satisfied the single failure criterion four B train logic.
only for events which result in coincident low pressurizer pressure and high con-l tainment pressure.
EVALUATION:
By letter dated February 22, 1982, the licensee provided a proposed modification of safety injection logic in response to the Confirmatory Action Letter 82-01 Additional information was provided by the licensee's letter Items 1 and 2.
This modification adds two-out-of-four logic matrices to of March 8,1982.
both the A and B train logic such that each train of safety injection is in-dependently initiated based upon low pressurizer pressure or high containment This change is being implemented in accordance with IEEE-279 and y
therefore includes provision for separation of electrical wiring for redundant pressure.
Following implementation of circuits in order to maintain their independence.
this change, I&E should perform an inspection to confirm that the installation of electrical wiring is in conformance to the physical separation requirements 7
l for the plant.
i The licensee's letter of March 8,1982, describes tests to be performed upon installation. During a phone coversation with the licensee on March 10, 1982, i
l we confirmed that the testing will adequately simulate the power requirementsWe l
of the logic circuitry and safety injection actuation relays (86 devices).
find the licensee's installation test program acceptable. Since functional RR0 5 0 W/6/
y testing of safety injection actuation relays are conducted during refueling outages in accordance with the plant technical specifications, the proposed modification does not involve consideration of testability at power.
Based on our review of the logic circuit modifications and description of the change included in Engineering Design Change Request 82-7 provided by the licensee's letters, we find that the requirements of Confirmatory Action Letter 82-01 Items 1 and 2 have been satisfied and the design change is therefore acceptable.
During our review of this issue it was noted that Maine Yankee Technical Specification 3.9 (Table 3.9-2) requires,as a minimum, two operable high containment pressure and two operable low pressurizer pressure sensors.
If Maine Yankee operated at these minimum requirements, a single sensor failure could cause the failure of safety injection actuation for events which do not result in both low pressurizer pressure and high containment pressure.
In their letter of March 8,1982 the licensee committed to place at least one inoperable sensor in the tripped position should the number of operable sensors fall to two. This applies to both high containment pressure and low pres-surizer pressure and is consistent with the current requirements for Maine Yankee's reactor protection system. The licensee also committed to propose this change to the Technical Specifications within 30 days of receipt of NRC approval of the safety injection actuation system design modification.
We find that the licensee's proposed actions satisfy our concerns, discussed above, and are acceptable.
MAR 12 gggg
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