ML17199U465
| ML17199U465 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/15/1988 |
| From: | Silady J COMMONWEALTH EDISON CO. |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| 4270K, NUDOCS 8803220343 | |
| Download: ML17199U465 (3) | |
Text
e Common.th Edison One First Nati Plaza, Chicago, Illinois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 - 0767 March 15, 1988 Mr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Dresden Station Units 2 and 3 Clarification of Past Appendix R Submit ta ls NRC Docket Nos. 50-237 and 50-249 References (a): Letter from J.R. Wojnarowski to J. Zwolinski dated August 9, 1985 Cb):
Letter from J.R. Wojnarowski to H.R. Denton dated January 9, 1986 (c): Letter from I.M. Johnson to T.E. Murley dated September 10, 1987
Dear Mr. Murley:
on January 13, 1988, we discussed with Dr. Chandrasekaran past Appendix R submittals concerning common enclosure, high impedence faults and fuse pulling.
This discussion resulted in four questions that Dr.
Chandrasekaran wanted documented in a new submittal.
- 1. It was stated in Reference (a) that overcurrent protective devices will provide protection from doWnstream faults.
- Can upstream faults cause a problem?
No.
The cables are protected from faults upstream of the common enclosure by the same protective devices that protect the cables for faults in the common enclosure and downstream of the common enclo~ur~.
- 2.
In order to defeat high impedence fault, the breakers for non-safe shutdown loads are tripped and, where necessary, their control power fuses are removed.
How much time after reactor scram is allowed for pulling the control power fuses?
The operators have 30 minutes to complete the breaker trip and fuse pulling operation.
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T. March 15, 1988
- 3.
In response to the concerns of I&E Information Notice 85-09, Exemption Request 7.3 was submitted to permit fuse replacement.
Which fire areas require fuse replacement?
Fuse replacement. may be required for fires in Fire Areas TB-I, RB 2-II and TB-V.
- 4.
When is the auto blowdown inhibit switch operated?
Procedures instruct the operators to immediately operate the auto blowdown inhibit switch in the event of a severe fire in any fire area.
In previous submittals, it has been stated that Dresden does not have a high-low pressure interface.
This is also reflected in the January 19, 1983 Safety Evaluation Report.
Changes have been made at the station so that a high-low pressure interface now exists between the fuel pool cooling system and the reactor shutdown cooling system.
While the reactor shutdown cooling system can withstand reactor pressure, the fuel pool cooling system cannot.
The interfaces between these systems exist between lines 2(3)-lOllC-6"-B (shutdown cooling) and 2(3)-lOll-6"-L (fuel pool cooling) and between lines 2(3)-1012C-6"-B (shutdown cooling) and 2(3)-1012-6"-K (fuel pool cooling).
Spurious operation of one of the following valve combinations while the reactor is operating could pressurize the fuel pool cooling system:
a) 2(3)-1001-2C and 2(3)-1001-lA b) 2(3)-1001-2C and 2(3)-1001-lB c) 2(3)-1001-4C and 2(3)-1001-5A d) 2(3)-1001-4C and 2(3)-1001-5B Information on these valves is as follows:
a) 2(3)-1001-lA and 2(3)-1001-lB -- These shutdown cooling inlet inboard isolation valves are 16" normally closed AC motor-operated valves fed from ESS Division I, 480V AC MCC-28(38)-1.
b) 2.(3)-1001-2C -- These shutdown cooling pump c suction outboard isolation valves are 14" normally closed DC motor-operated valves fed from ESS Division II, 250V DC MCC-2(3)-A.
c) 2(3)-1001-4C -- These shutdown cooling pump c discharge valves are 12" normally closed.DC motor-operated valves fed from ESS Division II, 250V DC MCC-2(3)-B.
d) 2(3)-1001-5A and 2(3)-1001-5B -- These shutdown cooling return isolation valves are 14" normally closed AC motor-operated valves fed from ESS Division I, 480V AC MCC-28(38)-1.
T. March 15, 1988 Although spurious operation of more than one valve is unlikely, the power to Valves 2(3)-1001-2C and 2(3)-1001-4C has been removed to preclude this possibility.
The breakers that feed these valves will be open during unit operation and power will be restored only when necessary during outage activities (i.e., while the reactor is depressurized).
Please contact this office if you require further information.
Very truly yours,
/)d~
J. A. Silady Nuclear Licensing Administrator 4270K