ML20211A461
| ML20211A461 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 09/30/1986 |
| From: | Miosi A COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 2191K, NUDOCS 8610150148 | |
| Download: ML20211A461 (8) | |
Text
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i }- 72 West Adams Street, Chicago, Illinois Commonwealth Edison Address Riply to: Post Off ce Box 767 Chicago, Illinois 60690 0767 September 30, 1986 Mr. Harold R. Denton U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulatory Washington, DC. 20555
Subject:
Braidwood Station Unit 1 Fire Protection August 1986 Audit-Resolution of Issues NRC Docket No. 50-456
Reference:
September 22, 1986 A.D. Miosi letter to H.R. Denton l
Dear Mr. Denton:
The purpose of this letter is to provide you with the results of our review of spurious operation of the Reactor Head Vent Valves for Braidwood Station Unit 1 as discussed with members of your staff on September 12, 1986 which was referenced in the above letter.
The analysis of the Head Vent valves is completed.
Attached are changes to the Fire Protection Report which account for that analysis.
Based on this analysisjchanges will have to be made to the Control Room Inaccessibility procedure (PRI-5) at both Braidwood and Byron Stations.
We anticipate that these changes to the PRI-5 procedure can be completed prior to exceeding 5% power f
pending your comments.
Also included are 2 copies of the draft procedure PRI-5 which was presented to the NRC during the September 22-26, 1986 Byron Unit 2 Fire Protection Audit.
This draft procedure addressed the concern about the use of jumpers to attain hot standby.
This was the subject of open item T-1 at the Braidwood Fire Protection Audit.
Mr. A. Coppola of Brookhaven National Labs reviewed the draft procedure with Byron operating personnel and he indicated that the draft procedure adequately addressed the jumper problem.
This is now submitted for your review.
ho]Q $
$ 004 ll #
. Please contact us should you have any questions concerning this matter.
One signed original and fifteen copies of this letter and enclosure are provided for your review.
Very truly yours, N
A. D. Miosi Nuclear Licensing Administrator
/klj enc 1.
cc:
J.
Stevens 2191K
BRAIDWOOD-1 AMENDMENT 9 2.4.3 Identification and Analysis of High-Low Pressure Interfaces 2.4.3.1 Indication of High-Low Pressure Interfaces A thorough review of all interfaces of the RCS with other plant systems has identified six high-low pressure interfaces that l
utilize redundant electrically controlled devices for isolation of the primary coolant pressure boundary.
Two of the interfaces consist of the two motor-operated valves in series in each of the RHR pump suction lines.
Two additional interfaces consist of the l
two power-operated relief valves (PORV's) and their associated motor-operated block valves.
The other two interfaces consist of the two pairs of solenoid-operated reactor head vent valves.
2.4.3.2 Evaluation of High-Low Pressure Interfaces 2.4.3.2.1 RHR Pump Suction Lines 2.4.3.2.1.1 Interface Description l
The two RHR pump suction lines are as follows:
1.
MOV RH8701A-1 and RH8701B-2 in RHR suction line from RC loop A.
2.
MOV RH8702A-1 and RH8702B-2 in RHR suction line from RC loop C.
These valves are interlocked by diverse pressure instruments as described in FSAR Subsection 7.6.4 and are shown in FSAR Figure 6.3-2 (P&ID M-62).
Power and control cables for valves 1RH8701A, 1RH8701B, 1RH8702A, and 1RH8702B are listed in Table 2.4-11.
2.4.3.2.1.2 Assumptions and Information Failure of a power cable either by ground or open would not affect the valve actuation logic.
Spurious opening of an RHR valve due to a hot short in the power cabling is considered.
Control circuit failures are also considered to cause spurious valve opening.
For any of the four valves to open, five control / interlock circuit conditions must be met:
Valve 1RH8701A 1.
Control switch on main control board in OPEN position; 2.
Reactor pressure less than approximately 400 psig (lPT-0405);
3.
Valve CV8804A closed (limit switch);
2.4-35
BRAIDWOOD-1 AMENDMENT 9 available at the remote shutdown panel and the fire hazards panel.
Therefore, procedures require closure of both of the PORV block valves (lRY8000A and B) following control room evacuation if pressurizer pressure cannot be maintained.
Block valve 1RY8000A can be closed from motor control center 131X2 which is located on elevation 414 feet 0 inch at column-row 11/S (Fire Zone ll.5A-1).
This is accomplished by transferring control of the block valve from the control room to the MCC using the transfer switch provided at the MCC, and then, by closing the block valve using the open/close switch provided at the MCC.
Likewise, block valve 1RY8000B can be closed at motor control center 132X2 located on elevation 426 feet 0 inch at column-row 12/S (Fire Zone 11.6-1).
This procedure will prevent the spurious operation of a PORV from having detrimental effects on plant safety.
Analysis and Results of Failure Mode 4 Failure mode 4 could occur in the following zones:
Train A Train B 2.1-0 2.1-0 3.3B-1 3.2B-1 3.3C-1 3.2C-1 ll.5A-1 11.6-1 Containment Containment For the failures in zones 3.2B-1, 3.2C-1, 3.3B-1, and 3.3C-1, the block valves would be closed from their respective MCC's using the same procedure used for a fire in Zone 2.1-0.
Fire Zone ll.5A-1 contains the MCC serving block valve A and cable IRY486 for PORV A.
Zone 11.6-1 contains the MCC serving block valve B and cable IRY487 for PORV B.
The PORV cables have been routed individually in conduit for these two zones.
- Thus, if a fire damaged the conduit and the PORV cable insulation, a hot short would not occur since there are no cables in direct i
contact with either PORV cable.
2.4.3.2.3 Reactor Head Vent Valves 2.4.3.2.3.1 Interface Description l
The four reactor head vent valves are as follows:
l 1.
Valve IRC014A in series with valve IRC014C (Train A);
2.
Valve IRC014B in series with valve IRC014D (Train B).
l l
2.4-44 i
l
BRAIDWOOD-1 AMENDMENT 9 I
The arrangement of these valves is shown in FSAR Figure 5.1-1, Sheet 1.
All four valves are d-c solenold-operated and are closed (de-energized) during normal operation.
Each valve is controlled through a separate circuit from a 2-position (CLOSE 4
and OPEN) switch at main control room panel 1PMllJ.
Power is supplied to each solenoid directly through the control cabling.
The Train A valves are powered from 125-Vdc non-safety-related Division 11 distribution panel 1DCCSEB and the Train B valves are powered from 125-Vdc non-safety-related Division 12 distribution panel 1DC06EB.
Table 2.4-15 lists the cables serving the head vent valves.
2.4.3.2.3.2 Assumptions and Information Spurious opening of a head vent valve due to a two-wire d-c hot short in the cabling is considered.
There are no interlocks.in the valve control circuits, however, fire induced failures of the control switches are considered.
2.4.3.2.3.3 Failure Modes Two fire induced failure modes are postulated.
Failure Mode 1 - Control Switch Contact Closure Train A:
Fire causes closure of control switch contacts at panel IPMllJ for valves 1RC014A and 1RC014C.
Circuits are energized and both valves open.
Train B:
Fire causes closure of control switch contacts at panel 1PMllJ for valves 1RC014B and IRC014D.
Circuits are energized and both valves open.
Failure Mode 2 - Two-wire d-c Hot Short to Control Cable Train A:
A two-wire hot short occurs due to contact of energized d-c conductors with cables 1RC620, IRC621, or 1RC622 for valve IRC014A, or with cable IRC626, IRC627 or 1RC628 for valve IRC014C.
Train B:
A two-wire hot short occurs due to contact of energized d-c conductors with cable IRC623, IRC624, or 1RC625 for valve IRC0148, or with cable IRC629, IRC630, or 1RC631 for valve IRC014D.
2.4.3.2.3.4 Evaluation and Results Failure mode 1 could occur as a result of a fire in the control room (Zone 2.1-0) only.
In the event of a fire in this zone, evacuation may be required.
Therefore, to preclude inadvertent 2.4-44a I
BRAIDWOOD-1 AMENDMENT 9 opening of the head vent valves, the PRI-5 procedure will be revised to require that, upon evacuation of the control room during a fire, the circuits for the non-safety-related head vent valves will be deenergized.
Failure mode 2 could occur as a result of a fire in any of the following zones:
Valve IRC014A or Valve IRC014B or 1RC014C Opens 1RC014D Opens 2.1-0 2.1-0 3.2E-1 3.2B-1 3.3C-1 3.2C-1 3.3D-1 11.6-0 3.4A-1 11.6-1 11.5-0 Containment ll.5A-1 11.6-0 Containment For any of the above zones, a fire could only open one of the valves.
Spurious opening of valves A and C or B and D would d-c require two simultaneous two-wire d-c hot shorts in the control cabling.
This is not postulated to occur.
2.4-44b
BRAIDWOOD-1 AMENDMENT 9 TABLE 2.4-15 CABLING FOR REACTOR HEAD VENT VALVES VALVE 1RC014A 1DC166 Power from 1DC05EB (Division 11) to control panel 1PMllJ 1RC620 Valve to reactor head connector plate IRC0lR-A 1RC621
' Reactor head connector plate to penetration lLV01E 1RC622 Penetration to control panel 1PMllJ VALVE 1RC014B 1DC167 Power from 1DC06EB (Division 12) to Control Panel 1PMllJ 1RC623 Valve to reactor head connector plate IRC0lR-A 1RC624 Reactor head connector plate to penetration lLV03E 1RC625 Penetration to control panel 1PMllJ VALVE 1RC014C 1DC166 Power f rom 1DC05EB (Division ll) to control panel IPMllJ 1RC626 Valve to reactor head connector plate IRC0lR-A IRC627 Reactor head connector plate to penetration lLV01E 1RC628 Penetration to control panel 1PMllJ VALVE 1RC014D 1DC167 Power f rom 1DC06EB (Division 12) to Control Panel 1PMllJ 1RC629 Valve to reactor head connector plate IRC0lR-A 2.4-216
BRAIDWOOD-1 AMENDMENT 9 TABLE 2.4-15 (Cont'd) 1RC630 Reactor head connector plate to penetration lLV03E 1RC631 Penetration to control panel IPMllJ J
1 i
2.4-217 l
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