ML20041B807
| ML20041B807 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 02/19/1982 |
| From: | Leasburg R VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Clark R, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 387B, NUDOCS 8202250219 | |
| Download: ML20041B807 (5) | |
Text
. _ _ _ - - - - -.
._m
.m_
JD VINGINIA ELECTRIC ann POWEN COMPANY H scismoNn, VIHOINIA 20261 i
H.H.LEANBUNG vic r......,
February 19, 1982 Ns;cs. nam OPENA1 UNN Mr. Harold R. Denton, Director Serial No. 387B Office of Nuclear Reactor Regulation N0/RGS:1ms 1
Attn:
Mr. Robert A. Clark, Chief Docket Nos. 50-338 Operating Reactors Branch No. 3 50-339 Division of Licensing License 'os7NPF4 W NPFd7 l
U. S. Nuclear Regulatory Commission e
Washington, D. C.
20555 g,
g v
\\
Gentlemen:
FEB 9-H.t q,h lES2m 5 l
ADDITIONAL INFORMATION ON RESPONSE TO NRC TECHNICAL EVALUATION f;
^
BYPASS AND RESET OF ENGINEERING SAFETY FEATURES U.m@
NORTH ANNA UNITS NOS. 1 AND 2 Vepco provided a response to an NRC technicil f3 % f
'co ev51uation On December 22, 1981, of bypass and reset of Engineered Safety Features for North Anna Units 1 and 2.
In our response, we indicated that since the identified modifications deal with Westinghouse supplied systems, Westinghouse would be contacted for concurrence prior to implementation.
We have completed our review with Westinghouse and submit the following modification to the information that we forwarded by letter Serial No. 387A dated December 22, 1981.
In keeping with the requirements of General Design Criteria 55 Criterion 1 i
and 56, the overriding of one type of safety actuation signal, e.g., radia-i tion, should not cause the blocking of any other type of safety actuation i
- signal, e.g.,
pressure, for those valves that have no function besides containment isolation.
NRC REQUEST:
f
" Circuitry provided for the control of the feedwater bypass valves does not satisfy Criterion 1.
The " reset" provided at the SSPS SAF-0UT board for this subsystem is actually on override. This override will terminate an output signal and block system actuation by a second input ' signal until the first is cleared.
Circuit design changes should be required to boI satisfy Criterion 1."
r i
VEPCO RESPONSE:
/[
A (2) position, " Normal - S/G Wet Layup" keylock switch located in each Train A and B system protection rack will be added to the FW l
bypass valve circuitry such that when the switch is in the " Normal" position (station in any operating mode except cold shutdown or refueling) the FW bypass valve reset switch will not permit opening the i
f 8202250219 920219 PDR ADOCK 05000339 P
2 Vs woINI A ELECTHIC ANIJ POWE k cOMIMNY To valves until the trip signal is cleared.
When the station is preparing to place the steam generators in wet layup, the above mentioned keylock switch will be placed in the "S/G Wet Layup" position which will allow the FW bypass reset switch to perform its reset function.
In this case, the signal being blocked (Hi-Hi SG level) is not considered to be a safety signal.
Keylock switch operation will be administratively controlled in the Station's Operating Procedures.
Criterion 2 - Sufficient physical features e.g., keylock switches, are to be provided to facilitate adequate administrative controls.
NRC REQUEST:
" Systems employing pushbutton actuated " resets" (i.e., containment isola-tion Phase A and Phase B, Containment Spray, and Feedwater Bypass Valve Isolation) do not comply with Criterion 2.
These " resets" actually func-tion as overrides and require appropriate physical features to ensure that they cannot be operated inadvertently and are operated only with proper supervisory contal."
VEICO RESPONSE:
Based on NRC interpretation of Criterion 2, Vepco will initiate a modift-cation that involves the addition of covers to the pushbutton reset switches for Containment Isolation - Phase A and Phase B, Containment Spray, and Feedwater Bypass Valve Isolation.
Because of the modification that will be made to address Criterion 1,
it will not be necessary to l
include the Feedwater Bypass Valve Isolation under this criterion.
Criterion 3 - A system level annunciation of the overridden status should be provided for every safety system impacted when any override is active.
(See R. G.
1.47).
NRC REQUEST:
" Systems employing pushbutton actuated " resets" (i.e., Containment Isola-tion Phase A and B, Containment Spray, and Feedwater Bypass Isolation) do not comply with Criterion 3.
These " resets" actually function as over-rides and require system level annunciation."
VEPCO RESPONSE:
It is our contention that Criterion 3 was inappropriately applied to Containment Phase A and B, Containment Spray and Feedwater Bypass Isola-tion systems at North Anna which employ pushbutton actuated resets. FRC stated that, "these resets actually function as overrides".
However, a true overrite blocks an actuation signal.
In this sense the resets in question cannot be considered overrides because the actuation signal must first be present, prior to the reset becon.ing ef fective.
s e
visoisir Luctuic Asp Powrk COMPANY TO In the case of the above systems, the operator must make a conscious decision to reset the system and then must take a positive action to do so.
Clearly, at the time he takes the action he does not need an alarm to tell him he has taken the action. At some time later, however, he may need to know whether he has reset the system.
In the case of Containment Isolation Phase A and B, Containment Spray and Feedwater Bypass Isola-tion, there are equipment lights on the control board to inform him of the system status once a piece of equipment has been operated.
It would therefore seem that additional annunciation for these systems would not only be unnecessary, but would be redundant.
If changes were made to provide reset annunciation for the above systems, extensive changes to the Westinghouse solid state protection system, including alterations to the Safeguards Driver printed circuit card, would be necessary. Based on the above assessment of the need and impact of providing system level annunciation for the subject systems, Vepco does not intend to proceed with this modification.
Criterion 4 - Diverse signals should be provided to initiate isolation of the containment ventilation system.
Specifically, containment high radiation, safety injection actuation, and containment high pressure (where containment high pressure is not a portion of safety injection actuation) should automa-tically initiate containment ventilation isolation."
NRC COMMENT:
Criterion 4 is not applicable at NAPS.
VEPC0 RESPONSE:
Vepco is in agreement with the KRC position regarding Criterion 4.
Criterion 5 - The instrumentation and control systems provided to initiate ESF should be designed and qualified as safety grade equipment.
NRC COMMENT:
"ESF instrumentation control systems at NAPS comply with Criterion 5."
VEPC0 RESPONSE:
Vepco is in agreement with the NRC position regarding Criterion 5.
Criterion 6 - The overriding or resetting of the ESF actuation signal should not cause any valve or damper to change position.
NRC COMMENTS:
" Criterion 6 is not satisfied at NAPS. Three instances were found with a resettin; c' an ESF signal will cause valves to change position.
Air ejector vent to atmosphere isolation valves.
The licensee may be able to justify this deviation from Criterion 6.
6 V woiv A Etranic Asp Powru CowrA4Y TO 4
Feedwater flow control valves.
The NRC staff should find this to be an acceptable deviation from Criterion 6".
FRANKLIN RESEARCH CENTER (FRC) COMMEN]
"In the case of the feedwater flow control valve.i no manual (i.e., push-button) reset is provided.
The SAF-0UT device for these valves is a non-inverting driver which will deenergize its master relay when its input signal, from an upstream logic device, clears. This logic device incorporates a signal seal-in based on the status of the reactor trip breaker to prevent automatica clearing when the isolation signal is accompanied by a reactor trip.
FRC's review of the feed and condensate system had determined that the reopening of the feedwater control valves following a feedwater isolation signal will not reduce below 2 the nanber of isolation barriers between the steam generator (or auxiliary feed pump discharge connection) and the low pressure portion of the feed and condensate system for either the feed and condensate system for either isolation signal that might not be accompanied by a reactor trip (i.e.,
manual sa fety injection actuation or high steam generator water level).
In either of these cases the initiating signal will shut the main feed line isolation valves and trip the main feed pumps.
The main feed pump trip will cause the feed pump discharge valves to shut.
Neither valve will automatically reopen upon the clearing of the isolation signal.
Based on the foregoing it is FRC's opinion that this design feature should be found by the hPC staff to be an acceptable deviation from current Criterion 6 as established in the comments following Criterion 6 in Section 2 of this report."
Feedwater bypass control valves.
This situation should be corrected through design improvement."
FRANKLIN RESEARCH CENTER C0tDIENTS "In the case of the feedwater bypass valves, repositioning will follow a signal operator action (depressing the feedwater bypass valve blocked
" reset" pushbutton) regardless of the status of isolation signals.
Further, the reopening of these valves, since they bypass the feedline isolation valves, results in there being only two valves (the feed pump discharge valve and feedline check valve) between the feed pump and steam generator.
In the unlikely situation of the failure of the feed pump to trip in response to the isolation signal only the check valve will remain and steam generator feed will occur should the bypass valves be open.
This situation should be corrected through design improvement."
VEPC0 RESPONSE:
Air ejector vent to atmosphere isolation valves - Vepco does not intend to make any changes under Criterion 6 concerning the circuitry for the air ejector vent to atmosphere isolation valves, since the present circuitry receives a high radiation signai and a containment isolation Phase A signal even though this valve is not a containment isolation valve. For this circuit, if containment isolation were reset and there
O
/
5 VtWU1%IA LLECTHIC AMD POWEN COMPANY TO was a high radiation condition, the air ejector vent to atmosphere isolation valves would remain closed.
If no high radiation condition were present, no detrimental situation would be encountered if the valve opened after resetting containment isolation.
Feedwater flow control valves - Vepco is in agreement with the Franklin Research Center's opinion regarding this circuit and does not intend to make circuit modifications.
Feedwater (FW) bypass control valves.
Criterion 6c - Upon completion of the modification as described under Crite-rion 1 above, during normal operations it will take two (2) operator actions to reset the FW bypass valves following the initiation of a SI signal:
(1) reset of SI and (2) reset of FW bypass valves.
The resetting of the bypass valves following a steam generator Hi-Hi level signal will be possible only after the signal has cleared and is really not an issue under Criterion 6 since the Hi-Hi level signal is not an ESF signal.
It was added to the design to provide equipment protection (prevents moisture carryover to the turbine).
It is Vepco's intention to attempt modification of the applicable circuits for Units 1 and 2 during the following Fall of 1982 maintenance outages.
If we can be of assistance in clarifying or interpreting information submitted with this response, please advise.
Very truly yours,
{
R. H. Leasburg cc:
Mr. R. C. DeYoung, Director NRC Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C.
20555 Mr. James P. O'Reilly, Regional Administrator Office of Inspection and Enforcement Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303