ML20004D087
| ML20004D087 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 06/03/1981 |
| From: | Gallagher J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| GL-81-12, NUDOCS 8106080337 | |
| Download: ML20004D087 (13) | |
Text
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PHILADELPHIA ELECTRIC COMPANY 2301 M ARKET STREET P.O. BOX 8699 1881 1981 PHILADELPHI A. PA.19101 (21518485003 JOSEPH W. G ALLAGHER absciasc peocuc7 om espastinsam7 June 3, 1981 Docket Nos. 50-277 50-2
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<;ar o Mr. Darrell G. Eisenhut, Director Q/
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et j U.S. Nuclear Regulatory Commission 2,y Washington, DC 20555
SUBJECT:
Peach Bottom Fire Protection Safe Shutdown Analysis
Dear Mr. Eisenhut:
The enclosures to this letter provide information associated with a new Peach Bottom Fire Protection Safe Shutdown Analysis that we committed to in the March 20, 1981 letter, S.
L.
Daltroff, Philadelphia Electric Company, to D. G.
Eisenhut, NRC.
The analysis is being repeated as a result of additional clarification provided in 10 CFR 50, Appendix R, and Generic Letter 81-12, dated February 20, 1981, from D.
G.
Eisenhut, and will demonstrate that the plant's fire protection features (either existing design or modifications to be proposed) will prevent damage to all systems that can be used to achieve and maintain safe shutdown conditions.
i l provides a description of the criteria and the two methods selected for the Safe Shutdown Analysis.
These two methods are consistent with those outlined in Generic Letter 81-12, section 6, titled:
"BWR Equipment Generally Necessary for Hot Shutdown".
This represents the safe shutdown analysis criteria committed to in our March 20, 1981, letter referenced l
above.
For purposes of the Safe Shutdown Analysis, these two methods will be tabulated essentially down to the component level and all cables required will be identified.
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Mr. Darrell G. Eisenhut Page 2 responds to item 1 of enclosure 2 to Generic Letter 81-12 by proposing an alternate method for providing the information requested. responds to item 2 of enclosure 2 to Generic Letter 81-12 on the high-low pressure interface consideration.
This enclosure identifies the interfaces and provides the bases for acceptability of the present Peach Dottom design.
In the interest of meeting the September 30, 1981, schedule for completion of the Safe Shutdown Analysis (committed to in our March 20, 1981 letter), we are proceeding with the safe shutdown analysis in accordance with the criteria and format described in the attached enclosures.
We would appreciate your expeditious review of and comments to this submittal so as to minimize possible delays in the resolution of this issue.
Please contact us if you should have any questions regarding this matter.
Very truly yours, V.\\,r) D _ /_ _. ___
Enclosures i
i
PEACH BOTTOM ATOMIC POWER STATION ENCLOSURE 1 Safe Shutdown Analysis Criteria Methodology of Analysis Two methods of achieving safe shutdown were selected for detailed study from the numerous possible combinations of equipment that could be used to achieve a safe shutdown. The two shutdown methods selected are described later.
In performing the safe shutdown analysis, the two shutdown methods were examined to determine the minimum equipment, control, and power requirements for operability of each method. The equipment and cables required for the two methods will be identified with respect to their location in the various fire areas.
The following assumptions vill be made for the first stage of the safe shutdown analysis:
a)
No credit is talen for manual fire fighting efforts or automatic fire suppreasion systems.
b)
The fira is assumed to disable all equipment and electrical cables located within the fire crea.
c)
Of fsice power is assumed to be unavailable af ter the fire as a result of the fire.
d)
Plant accidents, severe natural phenomena, and compone.f f ailures are not assumed to occur concurrently with the fire unless they can be identified to be caused by the fire.
e)
Credit is taken for reactor trip. Any fire affecting the reactor protection system or the control rod drive circuitry will not prevent the reactor from being tripped. The reactor can be tripped manually (in the control room), automatically (by the RPS logic), or manually by tripping the RPS power supplies (in the emergency switchgear rooms).
f)
No credit is assumed for proper operation of equipment that is not requi.s to change status during the course of the shutdown.
d I
Under these assumptions the analysis will identify those fire areas of the ' plant where a fire could possibly disable both methods of safe shu tdown.
In these areas the previous assumptions will be re-examined i
and analyzed to provide justification for the existing installation.
If the existing installation cannot be justified, it will be modified to t
provide compliance. Typically, the changes to the initial assumptions might be as follows:
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a)
Some credit may be taken for automatic suppression systeme where it can be demonstrated that it would be effective in isolating the fire to one of the two methods.
b)
Fire areas may be broken up in several fire zones based on the geometries of the areas and the lack of intervening combustibles.
c)
Offsite power may be assumed available for fires in areas not containing the power and control feeds for the two offsite sources.
d)
Multiple hot shorts, opens, and shorts to ground in multiple conductor cables may be considered incredible if several conductors and more than one failure mode is involved.
1 Description of Shutdown Methodc Although the safe shutdown analysis places primary emphasis on achieving react or shutdown using the two methods described below, many alternative shutaown methods would be available following a fire. Use of safety-related and nonsafety-related systems not addressed in the safe shutdown analysis, plus manual operation of certain equipment and con rols, would provide numerous combinations of systems with adequate capebility to snfely shutdown the plant.
Shutdown With Offsite Power With offsite power available, conventional plant equipment is used to achieve shutdown. Reactor heat is removed by bypassing main steam to the condenser. Heat is removed from the condenser by the circulating water system. Makeup water is supplied to the reactor vessel by the condensate and feed water system, taking suction on the condenser hotwell.
When the reactor has been depressurized below a nominal 75 psig, the RHR system is initiated in the shutdown cooling mode of operation. In this mode, reactor water is circulated through the RHR heat exchanger, where it is cooled by the HPSW system. Heat is rejected from the HPSW systen to the river.
Shutdown Without Offsite Power For purposes of this safe shutdown analysis, two methods of shutdown were selected that are operable without offsite power. Due to the assumption of loss of of fsite power, both Units will require the safe shutdown coincidentally. Due to the sharing of the die;e1 generators for certain common plant equipment, both Units safe anutdown analysis must be performed together. The two methods are described below.
3 f
Method A s
I The RCIC system is used to supply makeup water to the reactor from the condensate storage tank. The RCIC system also removes energy from the reactors in the form of steam used to drive the RCIC turbine.
I Initially, as steam is generated at a rate in excess of RCIC consumption it is relieved to the torus by automatic actuation of the relief valves operating in the over pressure relief mode. Heat is removed from the torus by one loop of the RHR system operating in the suppression pool cooling mode. Torus water is circulated through the RHR heat exchanger and returned to the torus. Heat is removed from the RHR heat exchanger by the HPSW system which in turn dissipates heat to the river.
At a reactor pressure of 100 psig, the RCIC system becomes inoperative due to system isolation. The reactor can then be depressurized below 75 psig by operation of the relief valves in the depressurization mode.
When the reactor has been depressurized below 75 psig, the RHR system 1
can be switched from torus cooling to the shutdown cooling mode.
In the i
shutdown cooling mode, heat is removed from the RHR heat exchanger by the HPSW system, which in turn dissipates heat to the river. The shutdown cooling mode of RHR will maintain the reactor in a cold shutdown condition.
The items of equipment that are required for this shutdown method include the following:
a).
Main steam relief valves - overpressure relief mode and depressurization mode b)
RCIC pump, turbine, and associated valves c)
"A" RHR/HPSW pumps valves, heat exchangers - Unit 2 "C" RRR/HPSW pumps valves, heat exchangers - Unit 3 l
d)
RHR compartment coolers e)
RCIC compartment coolers f)
"A" and "C" Diesel Generators and auxiliaries g) 2A/C and 3A/C Station Batteries h)
RHR Shutdown coolitg isolation valves Method B This method is essentially identical to Method A except that the HPCI system is substituted for the RCIC system.
The items of equipment that are required for this shutdown method include the following:
i
4 a)
Main steam relief valves - overpressure relief mode and depressurization mode, b)
HPCI pump, turbine and associated valves c)
"B" RRR/HPSW pumps, valves, heat exchangers - Unit 2 "D" RHR/HPSW pumps, valves, heat exchangers - Unit 3 d)
RHR compartment coolers e)
HPCI compartment coolers f)
"B" and "D" Diesel Generators g) 2B/D and 3B/D Station Batteries h)
RHR Shutdown cooling isolation valves Support Systems Additionally, the following support systems are required for both Method A and Method B.
These are common plant systems that are fed from the indicated power supplies, a)
Emergency service water for diesel and compartient cooling Two 100% loops - fed from "B" and "C" diesels (Unit 2 switchgear) b)
Battery room and Emergency Switchgear room ventilation systems. Two 100% loops - fed from "C" and "D" diesels (Unit 2 switchgear) c)
Control room emergency ventilation system. Two 100% loops fed f rom the "C" and "D" diesels (Unit 2 switchgear)
The following instrumentation will be provided in the control room for operator information.
a)
Reactor temperature b)
Reactor water level c)
Reactor pressure d)
Containment pressure e)
Torus temperature f)
Torus water level e-,
5 At least two of emel4 of these parameters will be identified along with their essential cables and power supplies. The support systems and cables will be located throughout the plant and will be subject to the same acceptance criteria as the equips ut used for the two methods of the shutdown.
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PEACH BOTTOM ATOMIC POWER STATION ENCLOSURE 2 Response to Request for Additional Information (RAI) #1 RAI 1.A Provide a table that lists all equipment including instrumentation and support system equipment that are required by the alternative or dedicated method of achieving and maintaining hot shutdown.
Response
A table of equipment (including instrumentation and support system equipment) will be established as part of the safe shutdown analysis.
This table will list the two methods of safe shutdown described in and will include all equipment required for operation of the two methods (valves, pumps, motors, logic cabinets, control switches).
This list will also include equipment whosa failure could defeat the method cf shutdown.
RAI 1.B For each alternative shutdown equipment listed in 1.A above, provide a table that lists the essential cables (instrumentation, control and power) that are located in the fire area.
Response
A list of all cables required for operation of the table will be developed. These cables will then be identified according to their physical location in the plant and a set of layout drawings will be marked to show the physical separation between the two methods.
RAI 1.C Provide a table that lists safety related and non-safety related cables associated with the equipment and cables constituting the alternative or dedicated method of shutdown that are located in the fire area.
RAI 1.D Show that fire-induced failures of the cabics listed in B and C above will not prevent operation or cause maloperation of the siternative or dedicated shutdown method.
Enclosere 2.
Response
A list of associated circuits will not be developed for each firs area, however, all the associated circuits will be analysed to demonstrate that their involvement in a fire will have no ef fect on the safe shutdown circuits, which we believe meets the intent of your request.
The third paragraph of the Request for Additional Information Item
- 1 lists _ three types of associated circuits that need to be addressed.
The following responses are only outlines of how these three areas will be addressed as part of the Safe Shutdown Analysis. The numbers correspond to the numbers in the RAI.
(1). All the power sources required for safe shutdown will be identified. The non-safe shutdown loads connected to these sources will then be analysed to verify that their isolating devices (circuit breakers and fuses) are properly co-ordinated to insure isolation at the rower source without af fecting the feed to the power source.
(2) All circuits that are connected to circuits required for safe shutdown will either be included in the Safe Shutdown Analysis or will be modified to be properly isolated from the safe shutdown circuits. All circuits for equipment whose spurious operation would adversely affect safe shutdown will be included in the safe shutdown analysis or modified to preclude the adverse effects.
[3] Associated circuits that share raceways with safe shutdown circuits will be acelysed to show that their failure due to a fire in a fire area will not cause adverse ef fects to the safe shutdown circuits with which they shara raceways in other fire areas. The basis for this analysis will be the results of the Sandia Labs cable fire tests where it was demonstrated that a sustaining fire could not be established due to an electrical fault in an IEEE 383 qualified cable. A fire in a fire area will be restricted to cables in that area and the only ef fects remote to the fire area might be fault current in the cables.
As deconstrated by the tests, these currents will not start a fire in an area remote to the fire area.
The Safe Shutdown Analysis will provide more details on these three types of associated circuits, however, we anticipate that the associated circuits will not have to be identified as to their physical location in the plant. This type of an analysis will be mcre direct than lengthy tabulation and retabulation of all the cables located in each room of the plant. The fire induced failures of the associated circuits will not prevent operation or cause misoperation of the safe shutdown circuits.
, RAI 1.E For each cable listed in 1.B above, provide detailed electrical schematic drawings that show how each cable is isolated from the fire area.
Response
If isolation devices are added to the eq'tipment used for safe shutdown in order to bypass specific plant areas, the details of these devices will
' be provided as part of the modifications, i
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PEACH BOTTOM ATOMIC POWER STATION ENCLOSURE 3 Response to Request for Additional Information (RAI) #2 RAI 2.A Identify each high-lev pressure interface that used redundant electrically controlled devices (such as two series motor operated valves) to isolate or preclude rupture of any primary coolant boundary.
Response
There are nine high-low pressure. interfaces per unit at Peach Bottom. Of these, only two per unit use redundant electrically operated devices (two series motor operated valves in each case) to isolate or preclude rupture of the primary coolant boundary. These two lines are the RHR shutdown cooling suction line (valves MD-10-17,18) and the RER head spray line (valves MO-10-32, 33).
RAI 2.B Identify the device's essential cabling (power and control) and describe the cable routing (by fire area) from source to termination.
Response
The M0-10-17 and MD-10-33 valves are 250V DC motor operated valves and the MD-10-18 and MD-10-32 valves are 39 480V AC motor operated valves. In order for the DC valves to open as a result of a power cable f ailure, would require a +125V DC hot short on two specific conductors, two other conductors shorting to each other and the fif th wire hot shorting to negative 125V DC.
These cables are each routed in their own conduits with one other control cable in each conduit. This control cable provides valve position indication and control. There are no combination of failures to the control cable that could cause the valve to operate. Additionally, there is no negative 125V DC in this control cable. Therefore, there is no conceivable way for the power cable to develop the necessary five correct shorts in order to open spuriously.
Therefore, the power and control cable between the motor control center and the valve, and the valve itself, need not be included in the identification of the valves' cables.
Similarly, between each 480V AC valve and its motor control center there is a power and control cable. Again, the control cable contains valve position indication and control; there are no combinations of j
failures to this cable that could cause the valve to open.
In order for the power cable to cause the valve to go open, a three phase to three phase correct rotation hot short would have to occur on the power cable.
_The power cables are multi-conductor cables, so the likelihood of all three phases receiving a different hot short are remote. These cables need not be included in the identification of the cables required for valve misoperation.
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. There are several ccatrol cables for each valve whose failure muld cause misoperation. The control cables for the shutdown cooling valves are routed from the control room to the remote shutdown panels from the remote s'iutdown panels to the motor control centers and logic panels in the cable spreading room. The control cables for che head spray valves are routed from the control room to the cable spreading room to the motor control centers.
The fire zones that contain these cables for the shutdown cooling valver are as follows:
MO 2-10-17 MD 2-10-18 Control room Control room Cable spreading room Cable spreading room Remote shtudown area Remote shutdown area M-G set room 165' elev. reactor b1dg.
135' elev. reactor b1dg.
MO 3-10-17 MO 3-10-18 Control room Control room Cable spreading room Cable spreading room Remote shutdown area Remote shutdown area 135' elev. reactor b1dg.
M-G set room 165' elev. reactor b1dg.
RBCW pump room Refer to the Response to RAI 2.D (following) for justification for not locating the head spray valve cables.
RAI 2.C Identify each location where the identified cables are separated by less than a wall having a three-hour fire rating from cables for the redundant device.
Response
From the tabulation above it can be seen that cables for both shutdown cooling valves are located within the control room, cable spreading room, and the remote shutdown area.
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. RAI 2.D For the areas identified in item 2.C above (if any), provide the bases and justification as to the acceptability of the existing design or any proposed modifications.
Response
The circuit breaker for one of the head spray valves will be administrative 1y controlled by locking it in the open position when the systen is not required to be in operation. Since the power will be removed from the valve and the discussion in the response to question 2.B above showed that the failure of the cables be'. ween the valves and the motor control center that caused the valves tr open is considered incredible, this blocking will provide absolute assurance that these valves will not open spuriously.
In addition to the concern for the shutdown cooling valves opening when its not wanted, these valves are also required to go open in order to get into shutdown cooling. Therefore, these valves will be included in the safe shutdown analysis and any changes to these valves' control cables for purposes of fire protection separation will be submitted with the results and recommendations following completion of the safe shutdown analysis. Continued operation is justified as follows:
a)
The shutdown cooling valves are isolation valves. As such that are separated according to the PBAPS separation criteria (physical separation between redundant components is in accord with Reg. Guide 1.75).
b)
The control room area is continuously manned. Any fire would be rapidly detected and extinguished. There are no open flames in the area and combustibles are held to a minimum, c)
The cable spreading room has smoke detectors and a CO, suppression sys t em.
Access to the arer. is controlled end non-essential combustibles are not allowed in the area.
d)
The remote shutdown arer has smoke detectors. Non-essential combustibles are held to a minimum in the area.
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