ML20211Q092
| ML20211Q092 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 10/16/1997 |
| From: | Wetzel B NRC (Affiliation Not Assigned) |
| To: | Richard Anderson NORTHERN STATES POWER CO. |
| References | |
| TAC-M99666, TAC-M99667, TAC-M99669, TAC-M99670, NUDOCS 9710220091 | |
| Download: ML20211Q092 (6) | |
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. soseHoot g_7gg o,
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October 16, 1997 Mr. Roger O. Anderson, Director i
Nuclear Energy Engineering i
Northem States Power Company 414 Nicollet Mall l
Minneapolis, MN 55401
SUBJECT:
TECHNICAL SPECIFICATION INTERPRETATIONS FOR AUXILIARY FEEDWATER AND SAFETY INJECTION SYSTEMS OPERABILITY - PRAIRIE-ISLAND NUCLEAR GENERATING PLANT UNIT NOS.1 AND 2 (TAC NOs. M99666, M99667, M99669, and M99670)
Dear Mr. Anderson:
The NRC staff has reviewed Northem States Power Company's (NSP) requests for technical 4
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specification (TS) interpretations dated September 12 and September 15,1997. The -
questions pertained to safety injection (SI) system OPERABILITY during changing plant l
conditions and auxiliary feedwater (AFW) system OPERABILITY when the AFW pump i
selector switches are in MANUAL and SHUTDOWN AUTO positions and the pump discharge valves are throttled, respectively. The staff's interpretations of Prairie Island TS for the SI and AFW systems are enclosed.
The staff agrees with NSP that the Si system is OPERABLE and there is no violation of the TS between reactor coolant system (RCS) temperatures of 310 'F and 200 'F with both Si i
control switches in the pullout position, and that the operator has a reasonable amount of time to perform the actions necessary to place the control switch in the pullout or AUTO retition at the RCS transition temperatures of 3"O 'F and 200 *F. However, the staff requests that NSP submit a TS change to eliminrate any ambiguity or questions regarding OPERABILITY during changing plant conditions.
The staff also agrees with NSP.that Prairie Island (PI) TS 3.4.B.1.c allows the AFW pump discharge valves to be throttled under administrative control during startup and shutdown operations. However, the staff does not agree with the NSP interpretation that in MODE 2 l
with the AFW pump selector switch in SHUTDOWN AUTO on MANUAL position which disables Function 7.d - automatic AFW pump start on main feedwater pump trip - that the
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AFW system is OPERABLE. Since function 7.d is required to be OPERABLE in MODES 1 i
and 2 in accordance with Pl TS Table TS 3.5-2B, placing the AFW pump selector switch in i
- the SHUTDOWN AUTO or MANUAL position would make funciton 7.d inoperable and require entry into the appropriate ACTIONS. The staff requests that NSP submit a TS change to
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- R. O. 'An'derson October 16, 1997
'._ Table TS 3.5-2B to change the APPLICABILITY from MODES 1 and 2 to MODES 1 and 2
above 2% power, as well as TS 3.4.B.1.c to explicitly state shutdown operations for the throttle valves.
Sincerely, ORIGINAL SIGNED BY Beth A. Wetzel, Senior Project Manager Project Directorate ill ' Division of Reactor Projects - lil/IV Office of Nuclear Reactor Regulation Docket Nos. 50-282 and 50-306
Enclosure:
As stated cc w/ encl: See next page OlSTRIBUTION:
Docket File PUBLIC PD# 3-1 Reading i
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< copy. ?No major changes to SE.
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OFFICIAL RECORD COPY-1
4 Mr. Roger O. Anderson, Director Prkirie Island Neclear Generating Northem States Power Company Plant cc:
J. E. Silberg, Esquire Site Licensing Shaw, Pittman, Potts and Trowbridge Prairie Island Nuclear Generating 2300 N Street, N. W, Plant Washington DC 20037 Northem States Power Company 1717 Wakonade Drive East Plant Manager Welch, Minnesota 55089 Prairie Island Nuclear Generating Plant Tribal Council Northem States Power Company Prairie Island Indian Community 1717 Wakonade Drive East ATTN: Environmental Department Welch, Minnesota 55089 5636 Sturgeon Lake Road Welch, Minnesota 55089 Adonis A. Nebiett Assistant Attomey General i
Office of the Attomey General 455 Minnesota Street Suite 900 St. Paul, Minnesota 55101 2127 U.S. Nuclear Regulatory Commission Resident inspector's Office 1719 Wakonade Drive East Welch, Minnesota 55089-9642 Regional Administrator, Region ill U.S. Nuclear Regulatory Commission 801 Warrenville Road Lisle, Illinois 60532-4351 Mr. Jeff Cole, Auditor / Treasurer Goodhue County Courthouse Box 408 Red Wing, Minnesota 55066-0408 Kris Sanda, Commissioner Department of Public Service 121 Seventh Place East l
Suite 100
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TECHNICAL SPECIFICATION (TS) INTERPRETATIONS FOR PRAIRIE ISLAND NUCLEAR GENERATING PLANT UNIT NOS,1 AND 2 Safety injection System Operability Prairie Island (PI) TS 3.3.A.1.c requires two safety injection (SI) pumps to be OPERABLE when the Reactor Coolant System (RCS) temperature is h310 'F. When the RCS temperature is <310 'F, Pl TS 3.3.A.3 and 3.3.A.4 determine SI pump OPERABILITY, Pl TS 3.3.A.3 requires that at least one SI pump control switch in the control room be in the pullout position whenever the RCS temperature is <310 'F, while 3.3.A.4 requires both SI pump-control switches to be in the pullout position whenever the RCS temperature is <200 'F.
In an effort to satisfy both of these requirements, the Pl TS have recently been interpreted to require plant operators to instantaneously place the one remaining SI pump control switch in pullout when the RCS cools to 200 *F. Likewise, as the RCS is heated, when the plant -
reaches 310 *F, the second SI pump control switch is required to be instantaneously placed in the " AUTO' position. With the control switch in the " AUTO' position, no Si switches can be in pullout or the heatup has to be stopped. Yet, the SI pump control switch cannot be placed
'in AUTO position prior to reaching 310 'F because this would violate the requirements of TS 3.3.A.3 whis requires at least one SI pump control switch in pullout when less than 310 'F.
Since you c.annot satisfy these requirements instantaneously, both of these circumstances were considered noncompliance with TS requirements that required reporting under 10 CFR 50.73 as a licensee event report (LER 1-97-09).
For changing plant conditions at 200 'F, NSP has re-interpreted the TS to allow both Si pump control switches to be in pullout position. This is based on the interpretation that both TS 3.3.A.3 and 3.3.A.4 requirements can be met if the TS phrase "at least one' is interpreted
- to allow both Si pump control switches to be placed in pullout prior to cooling down to 200 'F. Thus, one switch will be placed in pullout when the RCS is below 310 'F until the
- temperature approaches 200 'F. At that time both switches will be placed in pullout. This maintains the plant in a safe :ondition since events that require operation of the Si system at low RCS temperatures occur slowly and allow ample time for the operator to manually place the SI system in service. - The staff agrees that the phrase "at least one" will allow both Si control switches to be placed in the pullout position at any time the RCS temperature is
<310 'F.
For changing plant conditions as the RCS temperature reaches 310 'F, NSP interpreted TS 3.3.A.1.c and TS 3.3.A.3 to allow some reasonable time for operators to place the second SI
. pump control switch in the AUTO position. This reasonable time does not require definition since the plant is not in any imminent danger if the second SI pump control switch is not instantaneously placed in the AUTO position. This is based on the fact that the temperature of 310 *F is a target temperature at which the operators take their actions to implement low temperature overpressure protection. However, it was not expected the operator actions would occur precisely at 310 'F since the instrumentation that provides the RCS temperature indication is not exact and this temperature was based on heatup and cooldown curves where a precise temperature'was not calculated. Thus, it is not reasonable to expect operator action instantaneously at the precise temperature of 310 'F.
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The staff agrees with the licensee that the temperature is a target temperature at which actions need to be taken and that the actions cannot be taken instantaneously. However, the staff would expect the operator actions to be taken immediately upon reaching 310 *F.
Immediately is defined in the Standard TS (NUREGs 1430-1434) as actions that should be pursued without delay and in a controlled manner. Thus, the staff agrees with the licensee that a reasonable time limit for operator action is acceptable. However, the staff requests that Northem States Power Company (NSP) submit a TS change to eliminate any ambiguity or questions regarding OPERABILITY during changing plant conditions.
Auxiliary Feedwater System Operability with Throttled Pump Discharge Valves.
I Whenever the unit is critical or the RCS average temperature exceeds 350 *F, for single unit operation, TS 3.4.B.1.a requires the turbine-driven auxiliary feedwater (AFW) pump associated with the operating reactor and a motor driven AFW pump be OPERABLE; and for two unit operation, TS 3.4.B.1.b requires all four plant AFW pumps to be OPERABLE. TS 3.4.B.1.c requires all valves and piping associated with the AFW pumps to be OPERABLE whenever the unit is critical or the RCS average temperature exceeds 350 *F. This specification makes an exception that "during STARTUP OPERATION necessary changes may be made in motor-operated valve position." During normal plant startup and shutdown operation, the AFW pump discharge valves are throttled to control steam generator levels.
NSP questions whether the AFW pump discharge valves are OPERABLE when they are throttled, particularly during shutdown operations. The staff has reviewed TS 3.4.B.1.c and concludes that the term "STARTUP OPERATION
- encompasses MODES 2 through 4 in the Pl TS. However, based on the definition of STARTUP OPERATION in Section 1.0 of the Pl TS, the words "during STARTUP OPERATION" apply only when the plant is going up in power (startup). For shutdown operations the PI TS are not as explicit. However, the staff concludes that the defmition of OPERABLE - OPERABILITY in Section 1.0, the Objective of TS 3.4 " assure the capability of removing decay heat from the reactor," and the allowance to -
= change the throttle valves position on start-up and manual valve position during operations provide sufficient justification to conclude that the throttle valves can be throttled during shutdown operdtions. Thus, there is no question that the AFW pump discharge valves can be throttled as long as the throttling is done under direct administrative control, and that the
__ valves and the system _are considered OPERABLE. However, the staff requests that
. TS 3.4.B.1.c be modified to explicitly state that the motor-operated valves' position can be changed both on startup and shutdown.-
Auxiliary Feedwater System Operability with AFW Pump Selector Switch in Shutdown Auto in MODE 2.
AFW pump selector switches have three positions, AUTO, MANUAL, and SHUTDOWN AUTO, When the selector switch is in the AUTO position, all required automatic AFW start functions listed in Table TS 3.5-2B are enabled for the AFW pump. In the MANUAL position the AFW pump can be started or stopped by placing the associated pump control switch in-the START or STOP positions, respectively. In the MANUAL position, no automatic AFW pump start functions apply to the pump. The SHUTDOWN AUTO position enables all automatic AFW start functions on the pumps except the automatic start for loss of both main feedwater pumps. Pl TS Table TS 3.5-2B requires the AFW system to automatically start for a
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3 Function 7.e (SI) during MODES 1,2,3, and/or 4; for Functions 7.b and 7.f during MODES 1,2, and 3; and for Functions 7.c and 7.d during MODES 1 and 2. Function 7.d is the trip of both main feedwater pumps.
During startup and shutdown operation when there is a low feed demand, the normal method for providing steam generator feedwater is by using the motor-driven AFW pump. This is required because at low power levels, extended operation of the main feedwater pumps in the recirculation mode would cause damage to the main feedwater pumps due to heating and vibration of the pumps. Thus, safe, prudent operation of the plant requires placement of the AFW pump selector switches in SHUTDOWN AUTO during plant startup and shutdown.
During startup operations, as the plant approaches 2% power, the motor-driven AFW pump is operating and both pump selector switches are in SHUTDOWN AUTO. The first main feedwater pump is started and once stable operation is confirmed, the motor-driven AFW pump selector switch is briefly placed in MANUAL, the pump control switch is tumed to STOP to secure the pump, and then the AFW pump selector switch is set on AUTO. Likewise, during plant shti f wn, once the plant is below 2% power one AFW pump selector switch is momentarily tumeo to MANUAL, the ptg is started, and then the switch is placed in the SHUTDOWN AUTO position and the other AFW pump selector switch is placed in SHUTDOWN AUTO. Then the last operating main feedwater pump is secured. During both startup and shutdown evaluations the AFW pump selector switches are temporarily in SHUTDOWN AUTO or MANUAL while a main feedwater pump is operating.
Thus, NSP proposed that the PI TS Table TS 3.5-2B Functional Unit 7 d requirement for MODE 2 OPERABILITY be interpreted to only require automatic AFW pump start on loss of both main feedwater pumps when one or both main feedwater pumps are required for operation in MODE 2, and that AFW pumps be considered OPERABLE within the requirements of Table TS 3.5-2B, Functional Unit 7 d. for the brief period of time when the AFW pumps are operating in SHUTDOWN AUTO or MANUAL while the main feedwater pumps are operating.
The staff has reviewed the subject TS and concludes that the NSP interpretation is not correct. The TS require Functional Unit 7.d to be OPERABLE in MODE 2; placing the AFW pump selector switch in the SHUTDOWN AUTO or MANUAL positions makes this function (7 d), as well as the other AFW start functions for the manual position. inoperable. This then would require entry into the appropriate ACTIONS for the TS for inoperable instrumentation and/or AFW system. While the staff agrees that use of the AFW system during startup and shutdown to avoid main feedwater pump damage is required at Prairie Island, interpretating the TS to cllow this type of operation is not correct. The TS shauld be revised to limit the OPERABILITY of Functional Unit 7.d to MODE 2 above 2% power or other quantifiable limit.
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