ML20235W015
| ML20235W015 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 03/01/1989 |
| From: | Burski R LOUISIANA POWER & LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| W3B89-0195, W3B89-195, NUDOCS 8903100459 | |
| Download: ML20235W015 (7) | |
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..(t LG UISI AN A / 317 BAF;ONNE STREET P. O. DOX 60340 POWER S LIGHT NEW ORLEANS, LOUISIANA 70160 (504)595-3100
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burch 1, 1989 W3B89-0195 A4.05 QA U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Machington, D#C. 20555
SUBJECT:
Waterford SES Unit No. 3 Docket No. 50-382 Response to Item 1 of December 20, 1'188 RAI Regarding ATWS Rule Compliance
REFERENCE:
NRC letter (RAI), dated December 20, 1988 Gentlemen:
The above reference requested additional information regarding AThS Rule
-compliance at Waterford 3.
The Enclosure to this letter provides our response to Item 1 in the above reference.
Should you need additional information, please contact Roy Prados at (504) 595-2806.
Yours ery truly.
,.hh
. B*rski, Manager R.
u l'uclear Salety & Regulatory Affairs RFB/RWP/j tz Enclosure cc:
E.L. Blake, W.M. Stevenson, J.A. Calvo, D.L. Wigginton, R.D. Martin, NRC Resident Inspector's Office (W3) 8903100459 390301 g
DR ADOCK 05000382' W 9 p
PNV "AN EQUAL OPPORTUNITY EMPLOYER"
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RESPONSE TO ITEM 1 of 1'2/20)80 RAI REGARDING ATWS RULE COMPLIANCE
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W5B89-0195' 1.1 Justify the use of the existirg RTS instrument power for the DSS instruments, and demonstrate that the possibility of common mode failure is prevented.
ANSWER:
REFERENCES:
(1)
Figure 3 of October, 1988 ATWS submittal (2) DSS Power Supply Interface Sketch SK-B-E-0009 (3) Pressurizer Pressure Pam LOOP A and DSS Auto Trip Signal Interface Loop Diagram Sketch SK-B-E-0010 (4) Pressurizer Pressure Pam LOOP B and DSS Auto Trip Signal Interface Loop Diagram Sketch SK-B-E-0011 The RTS power supplies shown in Figure 3 of the October, 1988 submittal did not show the 3A and 3B static uninterruptable power i
supply back-up power supplies. The revised DSS power supply interface diagram, attached Reference 2, reficcts the power supply interfaces and the intent of the signal interface at the LCP 61 and LGP 62 PAC cabinets.
The DSS power supply is separate from the existing RTS power supplies as-it is powered from a non-1E vital, 125 VDC power distribution panel. This power distribution panel is connected to the'1E vital AB station battery with protection provided to prevent a common mode failure from occurring to the 1E vital bus. The 1E to non-1E class break (as approved in Section 8.3.2 of the FSAR) requires double device protection.
a isolation is accomplished as follows. The 1E feeder from the AB battery is initially isolated using a thermal overload circuit breaker and a current limiting fuse. The 1E to non-1E class break is taken after the current limiting fuse. A branch circuit breaker then feeds the DSS cabinet.
In the DSS cabinet, another circuit breaker has been added besides the previously identified fusing.
This will provide conservative double device fault protection at the DSS cabinet.
The signal interface for the DSS at the PAC cabinets is also isolated and diverse from the existing RTS (see attached References 3 and 4).
The signal to the DSS is from the wide range RCS pressure transmitters installed on the pressurizer. These pressure transmitters are used for monitoring and serve no safety control function regarding the RTS.
Isolation, comparator and relay interface cards will be installed in the PAC cabineta, which has been previously approved for isolating annunciator circuits from a safety function loop. The design incorporates separate transmitter signals which are not used for RTS signal inputs as well as having each interface card fused. The design precludes common mode failure at both the signal interface and at the power supply interface.
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-1.2 Clarify that the 125 VDC vital bus which supplies power te the RTS circuit breaker UV and shunt trips coils is not the same 125 VDC vital bus which supplies power to the DSS /DTT power relays. Describe the association, if any, between the RTS power and the 125 VDC vial bus power us<..d on the DSS actuation relay.
ANSWER:
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The Reactor Trip System (RTS) breaker under voltage (UV) and shunt
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trip coils are powered from the station batteries A and B.
The Diverse Scram System (DSS) and Diverse Terbine Trip (DTT) power relays are provided power by the non-1E vital bus as discussed in Item 1.1.
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