ML20010C164
| ML20010C164 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek, Callaway  |
| Issue date: | 08/14/1981 |
| From: | Petrick N STANDARDIZED NUCLEAR UNIT POWER PLANT SYSTEM |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| SLNRC-81-67, NUDOCS 8108190208 | |
| Download: ML20010C164 (16) | |
Text
_
SNUPPS Stenderdised Nuolest Unit Power Plant System 5 Choke Cherry Road Nicholes A. Petrick Roch ville, Meryland 20050 Exocutive Director (301)8694010 August 14, 1981
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^
81-67 FILE 02p
^
ICSB Positions / p.*
SLNRC SUBJ:
f Mr.HaroldR.Denton, Director!
%y Office of Nuclear Reactor Regulation 4
f U. S. Nuclear Regulatory Commission Washington, D. C.
20555 y
Docket Nos. STN 50-482, STN 50-483, and STN 50-486 g
Dear Mr. Denton:
During an NRC-SNUPPS meeting on July 27, 1981, the NRC staff (Instrumenta-tion and Control Systems Branch) distributed ten positon statements based on the review of the SNUPPS FSAR and on previous technical meetings.
After discussion on these ten positions, it was agreed that no further SNUPPS action was required on items 3, 4, and 5.
In addition, it was agreed that no action was required on item 10 until after plant operating procedures had been completed.
The enclosure to this letter provides responses to items 1, 2, 6, 7, 8, and 9.
Very truly yours, h-f.M\\C(y
'~ Nicholas A. Petrick
- RLS, i3b9 Enclosu.
cc:
J. K.
tryan UE D. F.
,nell UE G. L. Kt ster KGE D. T. McPnee KCPL W. Hansen NRC/ CAL T. E. Vandel NRC/WC QbW 5
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1.
Concern: The signal which initiates auxiliary feedwater when the main o
feedwater pumps are tripped is manually blocked on normal shutdown of the main feedwater pumps. The current design is such that the block is not automatically removed when the plant is returned to an operating mode where auxiliary feedwater initiation on loss of main feedwater is needed.
Postiton:
Even.though the signal to initiate auxiliary feedwater when the main feedwater pumps are tripped is considered to be an " anticipatory signal" for which no credit is taken in the analyses of FSAR Chapter 15, the staff position is that the block should be automatically removed when the plant
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is returned to an operating mode where auxiliary feedwater initiation on l
loss of main feedwater is needed. This position is taken since the signal provides significant diversity for starting the auxiliary feedwater system following loss of main feedwater.
j Response: A manual block of the signals which initiate auxiliary feedwater on loss of both main feedwater pumps will be indicated by an amber light on the ESF Status Panel. Operating procedures will limit the operating i
modes where its function can be blocked (blocking just prior to shutdown 4
of the last operating main feedwater pump and removal just af ter the first main feedwater pump is put into service).
TheprovisionsdescribedaboveIh'rovide reasonable assurance that the auxiliary feedwater start signal on loss of both " main feedwater pumps will not be blocked during operating modes where the diversity of this signal is desirable.
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2.
Concern:
It is not clear from the drawings provided and the description of the turbine trip circuits and mechanisms that the equipment used to trip the 4
turbine following a reactor trip meets the criteria applicable to equipment performing a safety function.
Position:
It is the staff position that the circuits and equipment used to trip the turbine following a reactor trip should meet the criteria applicable to a safety function with the execption of the fact that the-circuits may be routed through non-seismic qualified structures and the j
turbine itself is not seismically qualified.
l Response: The equipment employed to trip the turbine is the turbine protection system, which is part of the Electro-Hydraulic Control (EHC) system. The EHC system is a highly reliable system as shown by operating experience.
In order ~to provide maximum assurance that the turbine will be tripped, each reactor trip circuit is independently routed to and processed within the turbine protection system to provide two independtst means of tripping the t
i turbine. The routing of the two trip circuits from the protection system f
cabinets (located in the control room) to the EHC cabinet (located in the turbine building) is as follows:
One N. O. sinve relay contact circuit, one from each of the i
Westinghouse SSPS train A and B cabinets, is routed as separation groups 1 and 4 respectively to isolation relays located in the control building. Once isolated, the circuits from the isolation relays are routed as separation groups 5 and 6 to the EHC cabinet.
Separation group 1 is isolated to separation group 5 and separation
,i 4 is isolated to separation group 6.
The routing of the separation
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group 5 cable is physically separat'e from the separation group 6 cable.
Each of the trip circuits described above is directed to one of two trip busses within the turbine protection system Each of these busses energizes a set of cross-trip relays that in turn cross-trip to the other trip bus.
One trip bus energizes the Mechanical Trip Solenoid Valve (MTSV) directly:
the other trip bus acts to de-energize the Electrical Trip Solenoid Valve j
(ETSV).
Each of these valves is independently capable of tripping the turbine.
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Therefore, each trip circuit activates two independent paths throughout the io L
turbine protection system for tripping the turbine.
These trip circuits within the EHC system'are the same circuits that serve to trip tia turbine in the event of other abnormal turbine conditions such
' as over temperature and overspeed. These circuits are fully testsble during full power operation.
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Concern:
Information provided by the applicants indicates that the reactor coolant wide range temperature indicators to be provided on the auxiliary shutdown panel'will not meet all criteria applicable to safety related displays (such as being provided power fr.om separate Class IE busses).
Position:
The staff position is that reactor coolant system temperature is required parameter for maintaining the plant in a safe condition.
Indicators meeting criteria applicable to safety related displays should be provided for reactor coolant temperature on the auxiliary shutdown panel.
Response
As indicated in Section 7.4.3 of the SNUPPS FSAR, the reactor coolant wide range temperature indicators are not essential for maintaining safe hot shutdown (hot standby).
Safe hot shutdown can be maintained, from 4
the auxiliary shutdown panel through the use of the essential short-term 1
monitoring indicators and controls listed la FSAR Section 7.4.3.1.1.
These indicators and conttols meet the criteria applicable to safety grade equipment (see FSAR Section 7.4.3.1.4).
The reactor coolant wide range temperature indicators (one per RCS loop) located on the auxiliary shutdown panel provide a highly reliable indication of reactor coolant temperature., These instrument loops are powered from protection set II, isolated at the protection set cabinet, and routed to the auxiliary shutdown panel via separation group six.
- The indicators are the same model number as the pal 4S indicators 1
provided for the same function on the main control board.
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7.
Concern: The original design for actuation of the accumulator valve com-ponent level window on the bypassed and inoperable status panel was such that the bypass indication was not actuated until the valve reached the fully closed position rather than when the valve left the fully open po-sition. After discussions with the staff, the applicants changed the de-sign such thet the bypass is indicated when the valve is not fully open.
There may, however, be other valves where the bypass indication is not actuated when the valve leaves the pcsition required for it to accomplish its safety function.
Position:
The staff position is that bypass indication on the bypassed and inoperable status panel should be actuated when a valve leaves the position required for it to accomplish its safety function.
Response: Where valve misalignment (position switch input) is indicative of a bypass / inoperable status, the staf f position as stated above is med.
Such cases are the auxiliary feedwater discharge valves (air operated and motor operated) and the accumulator isolation valves.
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i 8.
Concern:
Instrumentation for process measurements used for safety functions such as reactor trip or emergency core cooling typically are provided with the following:
a) An indicator in the control room to provide the operator information on process variable being monitored which can also be used for periodic surveillance checks of the instrument transmitter, b) An alarm to indicate to the operator that a specific safety function has been actuated.
c) Indicator lights or other means to inform the operator which specific instrument channel has actuated the safety function.
d) Rod positions, pump flows, or valve positions to verify that the actuated safety equipment has taken the action required for the safety function.
e) Design features to allow test of the instrument e nel and actuated equipment without interfering with normal plant operations.
During review of the applicant's design, it was found that one or more of the featitres above was not provided for certain instrumentation used to initiate safety functions.
Examples include instrumentation used to isolate essential service water to the air compressors, insturmentation used to isolate the non-safety-related protion of the component cooling water system, and instrumentation used to isolate the spary additive tank on low low level. 1
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Position: The staff position is that instrumentation provided to perform safety functions such as isolating non-seismic portions of systems, closing valves when tank levels reach low level setpoints, and similar functions should be provided with alarms and indicators commensurate with the importance of the safety function and should be testable without interfering with normal plant op'erations.
The applicants should provide the staff with a list of all itaturment channels which perform a safety function where one or more of the features listed in a) through e) of the concern above are not currently provided.
For each of these insturment
- channels, the applicants should indicate which of the features a) through e)are not currently provided.
The staff position on these instrument channels is further that the applicants should:
a) Provide an alarm to indicate that the rafety function has been actuated if j
such an alarm is not in the current design.
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b) If not in the design, provide means to inform the operator which specific channel has actuated the safety function, c) If not in the current design, provide indication that the actuated safety equipment has taken the action required for the safety function.
d) If not in the current design, provide the capability for testing each safety function without interfering with normal plant operations and without lifting instrument leads or using jury rigs.
The capability for testing should include the transmitter where indicators are not provided to perform operability checks of the transmitters.
The staff will provide requirements in
'h-plant technical specifications for testing these safety fuentions.
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Response: We have investigated all of the process instrumentation provided to perform safety functions, and we have tabulated all of those process measurements which do not, at present, comply with all of the concerns "a" through "e".
Since compliance with concern "a" is not required and since appropriate changes will be made (as noted with an asterick) to presently 1
non-conforming measurements, all of the tabulated loops will be in conformance to the NRC positions "a" through "d".
Note that measurements which fully comply at present with each concern "a" through "e",
such as containment spray additive tank level, are not included in the tabulation.
Note the following general considerations in regard to the NRC concerns and positions:
- 1) The plant computer system is both accurate and highly reliable, and as such is used to provide certain of the indications and alarms.
- 2) Indication of which safety channel caused a particular actuation is provided by means of indicating lights in the Engineered Safety Features Actuation System. Since actuations not generated by the ESFAS are all based only upon a single channel, this indication is not applicable to them.
- 3) Many safety functions are simply normal operational functions of safety-related equipment (e.g., UHS cooling tower fan control).
Alarming of each actuation of such functions would simply distract the operator from other functions, without providing any useful information. For such functions, the alarms provided indicate not that the actuation has occured but rather that the process variable has exceeded the limit where the actuation should have occurred and plant conditions indicate that additional operator action is warranted.
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TABLE 8-1 Page 2 FSAR FIGURE / INST.
PARAMETER AND SAFETY ACTUATION /
ICSB POSITION 8 CLARIFICATIONS / RESPONSE LOOP NUMBER (S)
CONTROL FUNCTION CONCERNS C.
10.4-6 Shts 7&B/
Main feedwater pump trip oil (a) not provided No analog indication of oil pressure is FCPSL 25,26,125, pressure / starts the motor (b) provided provided.
All other applicable
& 126 driven auxiliary feedwater (c) provided positions are satisfied.
pumps on loss of both main (d) provided feedwater pumps.
(e) provided D.
9.2-3 Component cooling water flow (a) not provided*
Leakage would be indicated by decreasing EGFT-107,-108 to non-seismic piping:
Isolate (b) not provided surge tank level and the attendent alarms the non-seismic CCW piping on high (c) not applicable (see discussion of loops EGLT-1 and -2).
flow to protect the CCW water (d) provided Instrument loops EGFT-107 and -108 are inventory from possible (c) provided provided to initiate immediate isolation, seismically-induced gross leakage.
and thus to minimize the effects of gross leakage on the CCW water inventory.
Considering the time required for operator response, and considering the time required for gross CCW 1eakage to impact the CCW surge tank level and cause the attendent alarms and actuations, the provision of gross leakage alarms and indications would serve no purpose.
Positive indication of isolation valve position is provided'on the main control board and alarms are provided via the computer when the isolation valves close.
Note that the isolation valves would be colsed by a safety-injection signal.
- Flow indication (via the plant computer) will be added for each flow loop.
T TABLE 8-1 Page 3
'FSAR FIGURE / INST.
PARAMETER AND SAFETY ACTUA! ION /
ICSB POSITION 8 CLARIFICATIONS / RESPONSE LOOP MJMBER(S)
CONTROL FUNCTION CONCERNS E.
9.2-2/
lssential service water flow to (a) not provided Loss of cooling water to the air EFPDT-43,-44 air compressors:
Isolate the non-(b) not provided compressors would be alarmed in the seismic piping to the air compressor (c) not applicable control room via an air compressor from the ESWS to prevent excessive (d) provided common trouble alarm.
The ESWS inventory leakage of ESW into the turbine-or (e) provided is adequate to withstand leakage from full auxiliary building in the event of rupture of the non-seismic piping in both seismically-induced leakage.
trains for at least seven days without inpacting the ESWS operation.
Thus automatic isolation is not required to protect the ESWS, although it would be advantageous from an operational standpoint. Positive indication of valve position is provided on the main control board and alarms are provided via the computer when the isolation valves close.
F.
M-K2EF01(WC)
Essential service water self-(a) provided Indication of high differential pressure 9.2-2(CAL) cleaning strainer differential (b) provided is provided via the plant computer system.
1-EF-PDT-19,-20 pressure:
This parameter is (c) not applicable The proper operation of the strainer would 2-EF-PDT-19,-20 used for normal control of the (d) provided be indicated by the computer system display 5-EF-PDT-19,-20 ESWS self-cleaning strainers, (e) provided of differential pressure, since the and not to mitigate the differential pressure would decrease consequences of some event.
upon proper operation.
Strainer cleaning is initiated on high differential pressure.
TABLE 8-1 Pege 4 FSAR' FIGURE / INST.
PARAMETER #4D SAFETY ACTUATION /
ICSB POSITION O CLARIFICATIONS / RESPONSE LOOP NUMBER (S)
CONTROL FUNCTION CONCERNS
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- 9.2-2(CAL Essential service water (a) provided Indication and alarms concerning proper Addendum) temperature at Power Block Dis-(b) provided tower operation are provided via the 2-EF-TT-67A,-68A charge:
This parameter is (c) not applicable plant computer system (EGTE 69 & 70) 5-EF-TT-67A,-68A used for normal control of the (d) provided and by indicating lights on the main Callaway Site UllS cooling (e) provided control board.
The computer monitors-towers, and not to mitigate the the tower discharge temr erature and consequences of some event.
It provides a high temperature alarm.
is not a safety actuation Snce the only function of the tower parameter.
is to provide adequate ESW cooling, the discharge temperature--rather than the inlet temperature--is the information required by the operator.
i Actuation of the tower fans and valves is an operational control function, and so no alarms of actuation are provided.
11.
5,1-1/
Reactor coolant pump thermal (a) not provided No indication of flow is provided.
BB-FT-17,-18, barrier cooling coil discharge (b) provided All_other applicale staff
-19,-20 flow:
Isolato e TBCC from (c) not applicable positions are satisfied.
the low-pressure CCW system, (d) provided to protect the CCW system (e) provided from intrusion of high-pressure reactor coolant resultant of i
possible TBCC rupture.
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TABLE 8-1 Page'6 4
FSAR FIGURE / INST.
PARAMETER AND SAFETY ACTUATION /
ICSB POSITION 8 CLARIFICATIONS / RESPONSE LOOP NUMBER (S)
CONTROL FUNCTION CONCERNS 1
K.
%5.4-1/
Emergency fuel oil day tank (a) provided The following design features are JE-LT-1,21 level control / starts and stops (b) not provided provided for each emergency fuel the fuel oil transfer pumps to (c) not applicable oil day tank: Low level alarm keep an adequate supply of fuel (d) provided below the transfer pump start set oil in the tank.
(e) provided point, high level alarm above the transfer pump stop set point, and a minimum level alarm.
Alarms are not provided at the start and stop set points for the transfer pumps since these are normal control functions.
L.
10.2-1, sht.-1/
Turbine trip oil pressure /
(a) not provided No analog indication of oil pressure AC-PT-231, 232, reactor trip on a trubine (b) provided is provided. -All staff positions
& 233 trip.
(c) provided are satisfied.
(d) provided (e) provided t
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9.
Concern: On November 7, 1979, Westinghouse notified the Commission of a potential undetectable failure which could exist in the engineered safeguards P-4 interlocks. Test procedures were developed to detect failures which might occur. The procedures require the use of voltage measurements at the terminal blocks of the reactor trip breacker cabinets.
Position: In order to minimize the possibility of accidental shorting or j
grounding of safety system circuits during testing, suitable test jacks should be provided to facilitate testing of the P-4 interlocks.
The SNUPPS design will include test jacks to facilitate testing
Response
of the P-4 interlocks.
4.