ML20212P105
| ML20212P105 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 08/22/1986 |
| From: | Miosi A COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 2027K, NUDOCS 8609020189 | |
| Download: ML20212P105 (7) | |
Text
N A ) C3mmonwealth Edison Om Fire Nabonal Plaza. Chicago, Enois Address Reply to: Post Omco Bcx 767
,N Chicago,luinois 60690 0767 August 22, 1985 Mr. Harold R. Denton U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, DC. 20555
Subject:
Braidwood Station Units 1 & 2 Response to FSAR Q010.65 NRC Docket Nos. 50-456 and 50-457
Dear Mr. Denton:
Enclosed is our response to FSAR Question 010.65.
This is
. being provided to address questions raised by your staff during the review of the Braidwood Safe Shutdown Analysis which was included in Amendment 7 of the Byron /Braidwood Fire Protection Report.
This response will be included in a future amendment to the FSAR.
If you have any questions concerning this matter please contact this office.
One signed original and fifteen copies of this lett(r and attachment are provided for your review.
Very truly yourc, 0.'
h A. D. Miosi Nuclear Licensing Administrator
/klj cc:
J.
Stevens 2027K k,of 8609020189 860822 PDR ADOCK 0D000436 F
BRAIDWOOD-FSAR OUESTION 010.65 "The response to Question 10.55 provided by Amendment 39, regarding ope::ator response to plant transients caused by fire-induced spurious operation of equipment does not provide : sufficient detail.
For each fire area, identify the plant transients that could be initiated by fire-induced spurious operation of equipment.
Identify the instrumentation available to the operator to assess the transient and, necessary ccrrective actions to be taken.
Identify how the corrective actions would be integrated into the shutdown actions identified for Question 10.64."
RESPONSE
Valves are the only plant equipment considered subject to o
spurious operation, as a result of a fire, which could impact the safe shutdown capability of the plant.
Spurious starting of pumps due to a fire is not considered because there is no adverse safety impact of a pump starting.
An analysis has been' performed to identify those valves which are subject to spurious actuation due to a fire and could impact safe shutdown capability.
Assumptions The assumptions made in performing the analysis were as follows:
a.
Appendix R definitions of safe shutdown capability were used; b.
Fire occurs in only one fire zone of the plant; c.
All safe shutdown equipment which could be disabled by a fire in this fire zone is disabled and is thus not available for mitigation of the spurious operation.
Additionally, all circuits with cables in the fire zone are assumed to be disabled, and no credit'is taken for automatic functions initiated by these circuits.
d.
Spurious actuation of a valve results from hot short or open to power or control cables; e.
Only one spurious actuation occurs per single fire; f.
Spurious actuation plus failure of identical redundant components were not considered because separation of redundant equipment is addressed in Section 2.4 of the Fire Protection Report; and Q10.65-1
BRAIDWOOD-FSAR s
g.
Valves with power locked out were not considered because a hot short of the control cables would not cause actuation.
System Review Each plant system's piping and instrumentation diagram was reviewed to determine the effect of the worst case single spurious valve actuation.
(The Braidwood-l pressurizer POF.V's, block valves, and RHR suction valves are addre'ssed in Subsection 2.4.3 of the Fire Protection Report.
The Braidwood-2 PORV's, block valves, and RHR suction valves will be addressed in a future amendment to the Fire Protection Report.)
As a result of the system review, 13 valves for each unit were identified whose fire-induced actuation could affect i
, safe shut-down-capability of the plant.
These valves ~are J-as follows:
Auxiliary feedwater pump discharge, test valves 1/2AF004A a.
and 1/2AF004B; spurious operation closes valve A (B) and results in loss of AFW train A(B) flow, b.
Fire protection system containment isolation valves 1/2FP010 and 1/2FF011; spurious operation closes either valve and results in loss of water supply for hose stations inside containment.
c.
Essential service water pump suction valves 1/2SX001A and 1/2SX001B; spurious operation closes valve A(3) resulting in ' loss of ESW train A(B).
d.
RCFC essential service water inlet valves 1/2SX016A and 1/2SX016B; spurious operation closes valve A(B) resulting i
in loss of RCFC train A(B).
e.
RCFC essential service water outlet valves 1/2SX027A and 1/2SX027B; spurious operation closes valve A(B) resulting in loss of RCFC train A(B).
f.
Motor-driven auxiliary feedwater pump oil cooler outlet valve 1/TSX101A; spurious operation closes valve resulting in loss of lube oil cooling.
t g.
Suction valve 1/2SX173 for engine-driven cooling water pump for diesel driven auxiliary feedwater pump; spurious operation closes valve resulting in loss of oil and pump cubicle cooling.
h.
Diesel-driven auxiliary feedwater pump cooler outlet valve 1/2SX178; spurious operation closes valve resulting in loss of oil and pump cubicle cobling.
Q10.65-2
B RAIDWOOD-FSAR Evaluation The results of the system review show that the spurious operation valves identified for Braidwood are the same as those identified for Byron, except that Braidwood does not have valves OSX162A,B,C, and D.
However, the evaluation performed for B raidwood-l and -2 dif f ers from that performed f or Byron-l.
In the Byron-1 analysis, every fire zone was identified for which a single fire could result in a spurious valve actuation and a simultaneous loss of function of redun-dant safe shutdown equipment.
For B raidwood-l and -2 it was determined that identification of every zone where simul-taneous failures might occur is not necessary.
The reason is that the emergency shutdown procedures for Byron /Braidwood are symptom-oriented.rather than event-oriented, as discussed in Subsection 2.4.1.5 of the Fire Protection Report.
That is, there are no special procedures.for a fire in fire zone X,
rather the procedures cover loss of equipment X for whatever l'
reason.
These procedures would apply in the event of a spurious valve operation.
Also, while the B raidwood evaluation does not identify every zone where simultaneous failures might occur, it does identify the " worst case" zone (s) relative to impairment of the ability to mi,tigate the effects of a spurious valve operation.
As in the Byron-1 analysis, valves FP010 and FP011 were not reviewed for simultaneous loss of function of redundant safe shutdown components since the spurious actuation alone results in the worst case effect on safe shutdown capability.
Disposition of Results There are a number of fire zones for which spurious actuation of any of the 13 valves identified previously due to a single fire could af f ect the safe shutdown capability of the plant.
The following discussion addresses the actions that will be taken in regard to these valves.
a.
Valves 1/2AF004A and 1/2AF004B These valves are located in the auxiliary building general area on Elevation 383 feet 0 inch, Fire Zone 11.4-0.
Following a spurious operation of one of these valves for a fire in another fire zone, the valves would be accessible for manual operation.
- Thus, only a fire in Fire Zcne 11.4-0 is of concern.
However, a fire in Fire Zone 11.4-0 is acceptable for the following reason.
These valves are air-operated valves.
They are normally open and fail in the open position.
Instrument air is used to apply pressure on the diaghram to hold the valve closed against the force of the spring which normally 010.65-3
B RAIDWCOD-FSAR holds the valve open.
Following a fire in Fire Zone 11.4-0 which causes the simultaneous spurious operation of one of these valves and the loss of the opposite division AFW pump, all auxiliary feed-water flow would be lost.
However, the simultaneous loss-of-off site-pcwer event also results in loss of power to the instrument air compressors.
Since a continuous demand for instrument air exists, the air pressure of the instrument air system will quickly bleed off, and the 1/2AF004A/B valve will automatically open, and auxiliary feedwater flow will be restored..
No operator action will be required to achieve this.
The effects of the spurious operation automatically will be mitigated.
For the case where offsite power remains available coincident with a fire, the plant would remain in operation, and the auxiliary feed-water system would not be required.
Thus, a spurious operation of either of these valves would not be of concern when offsite power remains available, n
o b.
Valves 1/2FP010 and 1/2FP011 These valves are normally open energized valves, thus they fail closed on loss of power.
The fire protection line served by these valves is only required in the event of a fire inside containment.
The cables tor outboard isolation valve 1/2FP010 are routed outside containment and, therefore, a fire inside containment could not spuriously close this valve.
Spurious closure of 1/2FP010 or 1/2FP0ll due to a fire outside containment is not a problem since it would not be necessary to supply water to hose stations inside containment.
Since a fire inside containment could cause spurious closure of inboard isolation valve 1/2FP011, this valve has been replaced with a check valve (valve no. 1/2FP345).
The check valve is not subject to spuricus operation due to a fire, c.
Valven 1/2S_X001A and 1/2SX001B
]
l Circuit breakers supplying power to these valves will be deenergized during normal plant operation.
This will preclude spurious operation of these valves, d.
Valves 1/ 2S X016 A, 1/2S X016B, 1/2SX027A, and 1/2SX027B The worst case scenario involving these valves assumes that a fire in the auxiliary building damages the power cables to one train of RCFC fans and causes 010.65-4
BRAIDWOOD-FSAR a spurious closure of either the inlet or outlet valve for the essential service water supply to the redundant RCFC train.
This would result in a complete loss of RCFC function until the valve could be manually reopened.
Instrumentation available to the operator to determine that this situation exists includes containment temperature indication a'nd RCFC status indication in the main control room.
It has been verified that the inlet and outlet valves are accessible for manual operation.
These valves are all located in Fire Zone 11.3-1/2, the Unit 1/2 piping penetration area, which is also one of the fire zones with redundant cabl,es.
Therefore, a calculation has been performed for the loss of all RCFC's (conservatively assuming that the reactor continues to operate at full power) to determine if sufficient time -(at. least 30 minutes)
I' is.available to allow for manual operation prior to the time at which the containment temperature reaches the equipment environmental qualification temperature (325 F).
The results of this calcu-lation show that in 30 minutes the containment temperature reaches approximately 170 F,
assuming an initial temperature of 120
- F.
It is estimated that the equipment EQ temperature of 325
- F would be reached after 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br />.
Therefore, sufficient time is available to allow for manual operation.
e.
Valves 1/2SX101A, 1/2SX173, and 1/2SX178 The consequence of the worst case scenario involving spurious operation of any one of these valves is a loss of all auxiliary feedwater flow.
Valves 1/2SX173 and 1/2SX178 are cooling water valves to the diesel-driven auxiliary feedwater pump, and are located in the same room with the diesel engine and the pump, Fire Zone ll.4A-1/2.
For a fire in zone ll.4A-1/2, the motor-driven AFW pump could be operated.
For a fire in zone 11.4-0 the diesel ' driven pump would have to be operated, however, zone 11.4A-1/2, containing valves 1/2SX173 and 1/2SX178, is only accessible through zone 11.4-0.
For fires in other zones, the valves will be immediately accessible for manual operation.
For Fire Zone 11.4-0, credit is taken for opening of these valves upon loss of instrument air, since these valves are air-operated and they fail to the open position on loss of air.
Refer to the discussion under item (a) for valves 1/2AF004A/B for more details.
Q10.65-5
B RAIDWOOD-FS A R Valve 1/2SX101A is the cooling water valve to the motor-driven auxiliary feedwater pump, and it is located in the general area on Elevation 383 feet 0 inch, Fire Zone 11.4-0.
This is also one of the zones for which a fire could cause loss of the Train B auxiliary feedwater pump, and the Train B essential service water pump.
This is acceptable however, for the following reason.
A remote start switch has been added for the Unit 1/2 Train B AFW pumps to allow a remote start of these pumps following a fire in Fire Zone 11.4-0.
Furthermore, the Train B AFW pump diesel engine is provided with an engine-driven cooling water booster pump (1/2SX04P).
This pump will provide adequate essential service water cooling flow to the diesel engine and all of its auxiliaries, so that loss of both essential service water pumps would not prevent operation of the diesel driven AFW pump.
Refer to FSAR Subsection 10.4.9.2.1 and to FSAR Figure 9.2-2, sheet 6 of 11.
Thus, spurious operation of valve 1/2SX101A and coinpident loss of, the Train B AFW and ESW pumps can be mi.tigated by manually remote starting the Train B AFW pump with the new remote start switch.
Q 10. 6 5 -6 i