ML20058E640
| ML20058E640 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 07/27/1982 |
| From: | Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE, YANKEE ATOMIC ELECTRIC CO. |
| To: | Miraglia F Office of Nuclear Reactor Regulation |
| References | |
| SBN-300, NUDOCS 8207300139 | |
| Download: ML20058E640 (13) | |
Text
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SEABROO STATION lPUBLIC SERVICE 5,'..::2., Office:
Companyof New H-..p.Jwe 1671 Worcester Road Fromingham, Massachusetts 01701 (617) - 872-8100 July 27, 1982 SBN-300 T.F. B7.1.2 United States Nuclear Regulatory Commission Washington, D. 2. 20555 Attention:
Mr. Frank J. Miraglia, Chief Licensing Branch No. 3 Division of Licensing
References:
(a) Construction Permit CPPR-135 and CPPR-136, Docket Nos. 50-443 and 50-444 (b) USNRC Letter, dated April 22,1982, "Seabrook Auxiliary Feedwater System," F. J. Miraglia to W. C. Tallman
Subject:
Response to Requests for Additional Information (RAIs) from Instrumentation and Control Systems Branch (ICSB); A - K
Dear Sir:
We have enclosed responses to the subject RAIs (A - K) which you forwarded in Reference (b).
These RAI responses were presented to Instrumentation and Control Systems Branch, Reactor Systems Branch, and Auxiliary Systems Branch at a June 23 and 24, 1982 meeting at your offices in Bethesda.
Please assure that these RAI responses are reflected in the Draft Safety Evaluation Report which is soon to be published.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY n
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. DeVin,yc ntIs cf 7T o f ' l'roject Manager Enclosures hE 8207300139 820727 PDR ADOCK 05000443 h
PDR 1
A capability for decay heat removal using the auxiliary feedwater A.
system should not be dependent upon the use of non-safety grade equipment nor local operation of equipment following any design basis event for which the system function is required.
If required to demonstrate that the system can fulfill its safety function assuming a single failure limited operator. action outside the control room may be found acceptable if suitably justified and not required for at least 30 minutes following any design basis event.
RESPONSE
As described in a meeting on June 23. and 24 with the NRC, the Seabrook Emergency Feedwater System has.been modified to eliminate the need of non-safety grade equipment and local operation following any design basis event. The system now consists of redundant, safety grade flow isolation valves for each steam generator supply. Each valve is powered from an opposite emergency electrical power train. Safety grade manual controls for each of these valves are provided at both the main control board and remote shutdown panels.
The air-operated actuators for the steam generator atmospheric relief valves, have also been eliminated and replaced with safety grade electro-hydraulic actuators. These actuators can be controlled from either the main control board or the remote shutdown panels using safety grade controls. During cooldown, should a single failure disable any of these valves, manual operation of these valves is also provided locally near the valves. Because cooldown is a relatively long-term event, suf ficient time is available for the operator to take manual control at the local station.
The FSAR will be revised to reflect these design modifications.
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Since a non-safety grade instrument air system is used during B.
system operation, it should be backed up by suitable air-accumulators or an alternate air source which satisfies safety grade and redundancy requirements for the AFW system. Where air accumulators are used, they should have the capacity to maintain the equipment in service to permit operation at hot standby for at 4
least 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and the time to cool down to the conditions permitting operation of the RHR system such that the control of the decay heat removal may be performed from the control room without local operation of the valves. If an alternate air source is used it should be automatically placed in service when required or be capable of manual operation from the control room.
Appropriate technical specifications should be applied to the safety grade portion to the instrument air or backup systems and the designs should include provisions for surveillance testing including features used for isolation from the non-safety grade portions of the system. Also, the safety grade and non-safety grade portions of the air system should be specifically identified and isolation should be provided between safety grade and non-safety grade positions of the system.
RESPONSE
As described in the presentation made to the NRC on June 23 and 24, the use of instrument air for the Emergency Feedwater System has been eliminated. Motor-operated valves have now replaced the emergency feedwater flow control valve air actuators, and electro-hydraulic actuators have replaced the original air operators on the atmospheric steam relief valves. This eliminates the concern related to a safety grade air system for the Emergency Feedwater System.
Normal operation of the RHR system utilizes instrument air for the control of the RHR heat exchanger outlet and bypass valves.
Should the instrument air system be unavailable, a backup, safety grade, manually-operated air system has been provided. This system consists of high pressure air bottles and a manual air loading' station to allow control of these RHR valves. This manual air loading station will be located at the top of the RHR vaults.
However, establishment and continued operation of the RHR system is not dependent upon the use of instrument air. With'the unavailability of both the above mentioned air systems, the RHR heat exchanger bypass valve will fail to the closed position and the RHR heat exchanger outlet valve will fail to the full-open position. This failure mode provides full RHR flow through the RHR heat exchanger. Analysis of system startup and operation under these conditions has shown that an acceptable cooldown rate of less than 500F/hr will result.
Therefore, plant operation at hot standby and cooldown to cold shutdown can now be accomplished without the use of the instrument air system.
The FSAR will be revised to reflect these design modifications.
C.'
The control of steam generator level (flow control) from the control room should satisfy single failure requirements consistent with the redundancy requirements of the AFW System and not be dependent upon the use of non-safety grade equipment. If operator action to control AFW flow is required prior to 10 minutes af ter a system initiation, automatic control of steam generator levels should be provided.
If the use of block valves for the stopping and starting of AFW pumps is required to satisfy the single failure requirement of this position, an analysis should be provided to confirm that this operating mode is within the limitations of the equipment and their power sources as well as being a suitable means to control steam generator level.
RESPONSE
During the first 10 minutes following the initiation of emergency feedwater, there is no required operator action.
The revised Seabrook design now has two safety grade flow control valves for each steam generator supply. One valve in each supply is powered by the A train emergency power source and the other valve is powered from the B train. The primary (or normal) flow control valves for the A and C steam generator will be powered by the A train with B and D steam generators' valves powered by the B train. Back-up flow control valves will be powered from the opposite emergency power train.
(The normal power supply arrangement is consistent with that used to power the steam generator atmospheric relief valves.) These valves can be controlled from either the main control board or the remote shutdown panel using safety grade controls.
Following an incident which requires initiation of the Emergency Feedwater System, as steam generator water levels return to the normal operating level, the operator now has the capability to manually modulate flow to each of the four steam generators from either the main control room or the remote shutdown panel locations. Control of flow to all four steam generators is provided at the main control board and at each of the two remote shutdown panels.
The FSAR will be revised to reflect these design modifications.
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D.'
The control of f steam generator pressure from the control room should satisfy single failure requirements consistent with the redundancy requirements of the AFW System and not be dependent on the use of non-safety grade equipment.
RESPONSE
The revised Seabrook design for the system generator atmospheric relief valves now utilizes safety grade electro-hydraulic actuators.
These actuators are powered from emergency power sources and have safety-related manual control at both the main control board and the remote shutdown panels. Additionally, provisions have been made to allow local hand hydraulic control should electrical power be unavailable to any of the valves.
Under loss of power conditions, the valves are designed to fail in the closed position.
The FSAR will be revised to reflect these design modifications.
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Y The capability to terminate auxiliary feedwater flow to a faulted E.
steam generator from the control room, should satisfy single failure requirements and not be dependent on the use of non-safety grade equipment. If the design does not require termination of AFW flow to a faulted steam generator within 30 minutes or longer, limited operator action outside the control room may be found acceptable if suitably justified. Any single failure which could preclude the capability to terminate AFW flow from the control room should not also preclude the availability of suitable information to identify the faulty steam generator.
If termination of AFW flow to a faulted steam generator is required prior to 10 minutes for any design basis event, an automatic system should be provided in accordance with the protection system requirement (IEEE Standard 279).
RESPONSE
The revised Seabrook design now incorporates redundant. motor-operated flow isolation valves in each supply to each steam generator. Each valve receives an automatic closure single on high flow in that particular supply. The signal for closure for these valves is via separate safety grade flow indication systems. As presently designed, a flow rate of approximately_450 GPM, indicative of a depressurized steam generator, will now auto close both valves in that EFW supply. Upon closure of any valve due to high flow conditions, an interlock is provided to the other steam generator flow valves to prevent them from auto-closure.
The FSAR will be revised to reflect these design modifications.
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T F. '
Operating control features of the AFW Control System should not 4
l have the capability to block automatic initiation of_the AFW system.. Those valves including manual control valves, which would i
be closed or opened during testing ~ at power or during plant startup, should be provided command signals by the AFW automatic initiation system to assure that they are in the correct position, or such valves should provide _ input signals to the bypassed and inoperable status indication' system for the AFW System when in the incorrect position.
.The applicant should identify all' valves which_ fall into this category'and describe each valve operation based on the above design consideration.
RESPONSE
The Seabrook design does not require the use of the EFW System for normal startup and shutdcwn operations. Seabrook utilizes a Startup Feedwater Pump for these evolutions, whereas most other plant designs rely on their Auxiliary Feedwater System.- During plant power operation there is only one evolution which requires repositioning of manual valves to a position other than that' alignment required for. automatic actuation. This' evolution is the conthly testing of the emergency feedwater pumps. During this test, the pump discharge valve is closed and the1 recirculation -
valve is opened to allow the pump to be operated in the recirculation mode back -to the Condensate Storage Tank. - Both these_ valves, the, pump discharge and the recirculation valve, I
provide input signals to the bypassed and inoperable status l
indication system..As soon as the pump discharge valve is moved j
from the full open position or the pump recirculation valve is
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moved from the full-closed position, a signal:is 'sent to this status indication system which annunciates in the main control room.
Separate status indication systems are provided for both the A' train and B train valves.
i Additionally, all EFW flow control valves will be monitored by the
. bypassed and inoperable status monitoring system.
The FSAR will be revised to reflect these design modifications.
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1.
Valves which could be placed in a position that could block initiation of any portion of the AFW System should have control room position indication.
2.
A single valve, or multiple valves in series which could be placed in a position which could block initiation of all normal AFW system flow, should have redundant safety grade control room position indication.
All valves that fall into the above categories should provide input signals to the bypassed and inoperable status indication system for the AFW System.
The applicant should identify all valves which fall into these categories and describe each valve function based on the above design consideration.
RESPONSE
Power-operated valves in the EFW System are provided with control room position indication. Valves which require periodic manipulation during power operations are provided input to the bypassed and inoperable status indication system (in accordance with Regulatory Guide 1.47) as described in the response to Question F.
Additionally, administrative controls are provided on all manual valves in the Emergency Feedwater System. Each manual valve in the EFW System is locked in the normal position indicated on the system P&ID. This ensures that the only action necessary to initiate emergency feedwater flow is the starting of an EFW pump. The attached valve list indicates the normal locked position of these valves.
(It should be noted that this valve list was formulated using the existing revision of the P&ID's.
Valve alignment checklists will be revised to reflect the actual as-installed or modified system design.) Administrative controls also require that the position of these normally locked valves be verified monthly using valve alignment checklists.
There is no single valve, or multiple valves in series which could be placed in a position which could block initiation of all normal EFW System flow.
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ATTACHMENT TO RESPONSE TO QUESTION G Valve
' Normal Position Valve Normal Position Valve Normal Position CO-V154 Locked Open FW-V77 Locked Closed FW-V97 Locked Open CO-V155 Locked Open FW-V89 Locked Closed FW-V98 Locked Open CD-V158 Locked Open FW-V95 Locked Closed FW-V168 Locked Open CO-V159 Locked Open FW-V83 Locked Closed
-FW-V169 Locked Open CO-V146 Locked Closed FW-V152 Locked Closed FW-V85 Locked Open i
FW-V149 Locked Open-FW-V153 Locked Closed
.FW-V86 Locked Open FW-V191 Locked Closed FW-V154 Locked Closed FW-V170 Locked Open I
FW-V69 Locked Open FW-V155 Locked Closed FW-V171 Locked Open FW-V67 Locked Closed FW-V79 Locked Open FW-V78 Locked Closed-FW-V73 Locked Closed FW-V80 Locked Open FW-V96 Locked Closed FW-V65 Locked Open FW-V164 Locked Open FW-V90 Locked Closed -
FW-V71 Locked Open FW-V165 Locked Open FW-V84 Locked Closed FW-V125 Locked Open FW-V91 Locked Open FW-V94 Locked Open i
FW-V126 Locked Open FW-V92 Locked Open FW-V76 Locked Open FW-V127 Locked Open FW-V166 Locked Open FW-V82 Locked Open FW-V156 Locked Closed FW-V167 -Locked Open FW-V88 Locked-Open FW-V134 Locked Closed I
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~ If the circuits for automatic initiation of the AFW System include inhibits to block the initiation of the system, such inhibits shall be automatically' removed for operating conditions for which the safety function is required. Anticipatory trips if'not automatically re-instated should be identified by the bypassed and inoperable status indication system when the trips are required.
The applicant should identify any inhibits which exist and discuss the Seabrook design based on the above concern.
RESPONSE
The Emergency Feedwater System is initiated by one of three conditions. They are: 1) low-low steam generator level, 2) safety injection actuation 3) loss of off-site power. There are no blocks or inhibits which defeat auto actuation of these signals.
Should the control switch for emergency feedwater pump P-37B be pla'ced in the " pull-to-lock" position, automatic start of this pump would be defeated; however, with this control switch in the
" pull-to-lock" position, an alarm signal is generated via the bypassed and inoperable status indication system. Should the control switches for the steam supply to the steam-driven emergency feedwater pump P-37A be placed in the closed position, automatic opening of these valves would be defeated. However, as with the control switch for P-37B, this control switch position provides input to the bypassed and inoperable status indication system and would be annunciated in the control room.
The FSAR will be revised to reflect these design modifications.
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It appears to be common practice in Westinghouse plant designs, to provide automatic initiation of auxiliary feedwater systems on the tripping of main feedwater pumps (loss of main feedwater flow).
This design feature is not included as part of the Seabrook design.
Please provide a discussion on this issue and-justify why this commonly used AFWS initiation function is not required for Seabrook.
RESPONSE
In the Seabrook design, the Emergency Feedwater System is intended to operate only in response to the following safety signals:
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Loss of off-site power 2.
Safety injection 3.
Steam generator level low-low For other plant conditions or evolutions, the startup feed pump will be utilized. On tripping both the main feedwater pumps (FW-P32A, FW-P32B) the startup feedwater pump is started automatically and provides the necessary flow to all steam generators.
Additionally, the analysis of the loss of normal feedwater flow in Section 15.2.7 in the FSAR, shows acceptable results without requiring automatic initiation of the Emergency Feedwater System upon tripping of the main feedwater pumps.
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If the protective system can take action which precludes operating capabilities provided at remote shutdown panels, and this action can be initiated due to the consequences of post-trip conditions, the capability should be provided at the remote shutdown panel to indicate the status of the protection system and to permit the reset of the protection system such that safe shutdown conditions can be maintained.
The applicant is requested to discuss the Seabrook design as it relates to the above concern.
RESPONSE
The revised Seabrook design of the Emergency Feedwater System now provides manual modulating capability of the emergency feedwater flow control valves from the remote shutdown panels. This capability is independent of automatic system actuation. Should the emergency feedwater system be actuated, control of emergency feedwater flow is still capable from either the main control room or the remote shutdown panel. Resetting of the EFW automatic initiation circuitry is not required for manual operation of the EFW System from either the main control board or the remote shutdown panels.
The FSAR will be revised to reflect these design modifications.
K.*
The Seabrook design for auxiliary feedwater flow control from outside the control room allows the control of only two of the four control valves from any one of the redundant remote shutdown l
panels (i.e., two' valves are controlled from panel 108A and the remaining two are controlled from panel 108B). Therefore, a single failure (loss of one train of power for. example) on one of the remote shutdown panels would leave the operator with flow control for only two steam generators. Furthermore, loss,of one.
train of power would result in' continuous uncontrolled flow to the
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remaining two steam generators. Please provide discussion on this -
phase of the design as it relates to Item C, above.
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RESPONSE
The revised Seabrook design of the Emergency Feedwater System now incorporates two flow control valves in each supply to each steam generator, for a total of eight flow control valves. Four of these valves are powered from an A train emergency power source and four are powered from a B train emergency power source. In a
each supply to each steam generator, there is an A train' valve and.
a B train valve. This new design now provides control of four-emergency feedwater flow control valves, one to each steam generator, from each of the remote shutdown panels.
The FSAR will be revised to reflect these design modifications.
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