ML17261A366
| ML17261A366 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 01/09/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17261A365 | List: |
| References | |
| GL-83-28, GL-85-09, GL-85-9, NUDOCS 8701140367 | |
| Download: ML17261A366 (9) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 SIIPPLEMENTAL SAFETY EVAI IJATION RY T~E FFI F
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P IER PL NT GENFR IC I ETTER 3-8, ITEM
.3 REACT R TRIP BREAKER UT M TIC SHUNT TRY.P INTROIIUCTION AND SIIMMARY Generic Letter 83->8 was issued hy NRC on luly 8, 1983, indicatino actions to be taken by licensees based on the generic implication of the Salem ATMS events.
Item 4.3 of the generic letter requires that modifications be made to improve the reliability of the reactor trip svstem bv implementation o+ an automatic actuation of the shunt trip attachment on the reactor trip breakers.
Suhsequent to the review o~ the licensees'ubmittals of November 4, 1983, and March 19, 1985, the staff issued a safetv evaluation report on lay 13, lo85, indicatina the acceptable and unacceptable aspects of the design and requested the licensees to submit additional information <or staff's approval.
Rv letters dated November 19,
- 1985, May 15,
- 1986, and November 20, 1986, the licensees submitted additional information.
In addition, the licensees responded to specific staff questions by telecons on May 28, lune 19 and 1une 30, 1986.
The staff has reviewed this in~ormation, and finds it acceptable.
The licensees have not submitted proposed Technical Specification changes in accordance with Generic Letter 85-09 and Item 4.3 T.S. of Generic Letter 83-R8; however, these proposed Technical Specifications will be separately evaluated as part of the review for Item 4.3 TS.
8701140367 870109 PDR "kDDCK'5000244 EVALIjATION The licensees have not committed to performing all o< the testing requirements which are considered necessar v; however, these issues will be considered under Jtem 4.3 T.S.
(Technical Specification changes>
and Item <.5 "RTS ~eliabilitv
~
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'1 (System Functional Testing)."
We, therefore, consider this present review as limited to the proposed design modifications.
The licensees submitted revised electrical schematics as requested in the staff's Hay 13, 1985, SER.
Our review of these schematics show that the design:
(1) permits independent verification of the operability of.the shunt and undervoltage trip attachments of the reactor trip breakers during on-line testing; (2) provides bypass breaker position status lights on the main control board, including a cell switch interlock to indicate when the bypass breaker is in the operating (racked-in) position; and (3) provides interlocks to preclude both bypass breakers (if a second bypass breaker is installed in the future) from being closed at the same time.
The Ginna design for the shunt trip actuation of the reactor trip breakers differs from the g'eneric design provided hy the Westinghouse Owners Group in that the Ginna design does not use an auxiliary relay to initiate the shunt trip actuation.
- Instead, the spare contacts of the existing reactor protection system logic relays ar ranqed in a matrix are used for automatic actuation of the shunt trip device.
Attachment
- l. is a simplified schematic diagram to con-ceptually illustrate the design.
The letters in parenthesis used below refer to those on the attachment.
The logic relav contacts (A> and (R) operate simultaneously to trip the RTB.
The (Al contacts close to eneraize the shunt trip attachment TI; and the (R>
contacts open to deenergize the UV coil.
The red light (If> across the UY coi 1 goes of< and the green light (4~ across the ~TR's "a" contact (F) goes on to indicate successful operation o~ the relav contacts (Bl and (A),
respectfully.
This test checks the operation of the relay contacts and does not independently test the UV coil and STA o< the RTB.
The test can be made with the RTB in the test or racked-in position and in the tripped condition.
Independent testing of the UY trip device and STA of the reactor trip breakers is accomplished using manual test pushbuttons or switches.
For the shunt trio
- test, a test pushhutton (C) in parallel with the spare contacts (Al of the automatic trio logic matrix can be used for manual independent on-line testing of the STA.
The I.Y trio circuitry is not actuated hy this test.
Ae find this independent on-line testing caoability acceptable.
4-For the UV trip test, operation of the center plunger on a relay in the zircon-ium guide tube circuitry can be used to interrupt power flow to the UV coil without actuating the STA as follows.
A unique feature of the Ginna station is the zirconium guide tube interlock circuitry.
This circuitry is not required for the reactor protection but assures that the control rods are not engaged in the grippers during plant cooldown when different materials may experience dif-ferent thermal contraction rates.
The zirconium guide tube circuitry provides additional relay contacts (D) in series with the protection system logic relay matrix for the UV trip.
These contacts can be opened by operating the center plunger of the relay.
Opening of these relay contacts tests the operability of the UV trip coil by interrupting the power flow to the UV trip coil without af-fecting the STA circuitry.
Me find this on-line testing capability acceptable.
The Ginna cell switch interlocking circuitry associated with the bypass break-ers also differs from other designs that we have reviewed.
The Ginna design h
prevents a second bypass breaker from being closed if the other bypass breaker is first racked into the operating position.
Other designs would permit the second bypass breaker to be closed, but would immediately trip it if the other
~ ~ ~ bypass breaker were racked in and closed.
The Ginna design is somewhat super-ior in this regard.
However, in the Ginna design, the electric circuitry by itself would not prevent an already closed bypass breaker from being racked in while the other bypass breaker was racked in and closed.
Upon questions posed by the staff in this regard, the licensees stated that the bypass breaker is prevented from being racked in while it is closed by a hardware device which would mechanically trip the breaker as it was being racked in.
The staff, therefore, finds this design acceptable.
Presently, the issue is moot because Ginna uses only one bypass breaker.
How-
- ever, the staff reviewed the design in case a second breaker is utilized in the future.
CONCLUSION All issues under Item 4.3 of Generic Letter 83-28 have now been found acceptable except for submission of proposed Technical Specification changes for staff re-view.
The proposed Technical Specification changes will be considered under a
separate safety evaluation.
Principal Contributor:
A. Toalston
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Simplifie Schematic Diagram
.Illustrating Independent Testing of Reactor Trip Breaker UV and STA Devices and Logic Relay Contracts Attachment 1
Notes:
Ey A and B are logic relay
- contacts, C and 0 are test
- switches, E and F are "a" contacts on the Reactor Trip
- Breaker, G and H are test lights.
During normal operation, the Reactor Trip Breaker is closed A and C are open.
For surveillance testing, the Reactor Trip Breaker is by-'assed, 0 is opened to test breaker opening by UV device, C is closed to.test breaker opening by STA.
With the Reactor Trip Breaker open and bypassed, contacts C,
E and F open and D closed, the logic test opens, contacts B and closes contacts A,
light H.goes out, light G
goes on.
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