ML20244A620
| ML20244A620 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 04/03/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20244A607 | List: |
| References | |
| NUDOCS 8904180106 | |
| Download: ML20244A620 (3) | |
Text
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_8 NUCLEAR REGULATORY COMMISSION o
2 WASHINGTON, D. C. 20066
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SAFETY EVALUATION BY THE OFFICE-0F. NUCLEAR. REACTOR. REGULATION RELATED TO AMENDMENT NO.- 29 TO FACILITY OPERATING. LICENSE.NO..NPF-42 '
WOLF. CREEK NUCLEAR.0PERATING. CORPORATION WOLF. CREEK GENERATING. STATION DOCKET NO. 50-482 INTRODUCTION
'The Wolf Creek Generating Station Technical Specifiestion Table 3.3-3,
" Engineered Safety Features Actuation System Instrumentation", states that while in Modes 1 or 2, a trip of all main feedwater pumps will result in the
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automatic actuation of the motor driven auxiliary feedwater pumps. This I
feature could be undesirable during certain portions of plant startup or shutdown operations while in MODE 2.
During normal startup operation in MODE 2, the steam generators are normally being fed by either the startup motor driven feedwater pump or the auxiliary l
feedwater pumps. A turbine driven main feedwater pump (TDMFP) is not started i
until the reactor is at approximately 2% power and preparations are being made j
to start the main turbine generator. Once a TDMFP is.placed in service, reactor power is then increased above 5% into MODE 1, and the main turbine is rolled up to speed.
When the plant is being shutdown, the main turbine generator is taken off line, reactor power is dropped below 5% (entering MODE 2) to approximately 2%,
the startup motor driven feedwater pump is placed in service, the last TDMFP is taken out of service and then the Reactor Operator inserts the control rods and lowers the plant into MODE 3.
The problem that can develop is that during plant shutdown, at least one TDMFP mustbereset(i.e.,notripsignals)priortoenteringMODE2. Similarly, during plant startup while in MODE 2, at least one TDMFP must be reset prior to startup of the first TDMFP. The TDMFPs exhaust their steam into the Main Condensers. Therefore if there is no vacuum in the Main Condensers, the TDMFP cannot be reset, or if while in MODE 2, condenser vacuum must be taken out, an Auxiliary Feedwater Actuation will occur. An auxiliary feedwater actuation under such conditions is undesirable because 1) it is unnecessary from an operations viewpoint and 2) it causes thermal cycling by injecting cold water from the condensate storage tank to the hot steam generators.
By letter dated July 6,1988, the licensee submitted a proposed amendment that revises Wolf Creek Generating Station (WCGS), Unit No.1, Technical Specification Tables 3.3-3 and 4.3-2, which address the Engineered Safety Features Actuation System Instrumentation. This amendment request removes the MODE 2 applicability requirements from TABLE 3.3-3 Functional Unit 6.g and TABLE 4.3-2 Functional Unit 6.g, " Trip of all Main Feedwater Pumps - Start Motor Driven Pumps".
8904180106 890403 DR ADOCK O 42
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' EVALUATION l
J This proposed amendment allows the actuation signal to remain blocked until a l
TDMFP is placed in service, and when shutting down to allow blocking the signal before securing the last TDMFP. This action is consistent with the following statements in the NRC Safety Evaluation Report for Wolf Creek, Section 7.3.2.7:
"The signal which initiates auxiliary feedwater when the main feedwater pumps are tripped is manually blocked on normal shutdown of the main feedwater pumps. The 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.
Even though the I
signal to initiate auxiliary feedwater when the main feedwater pumps are tripped 1s considered to be en " anticipatory signal," for.which no credit is taken in the analyses in SNUPPS FSAR Chapter 15, the staff position was that the design should include appropriate features to ensure that the block is removed when the plant is returned to an operating mode where auxiliary feedwater initiation on loss of main feedwater is needed. The applicant has committed to provide automatic indication of the block of the signals which initiate auxiliary feedwater on loss of both main feedwater pumps on the bypassed and inoperable status panel.
Operating procedures will lisait tho operating modes during which the block can be in effect. Blocking will be permitted just before shutdown of the last operating main feedwater pump end removed just after the first main feedwater pump is put into service. The staff concludes that the applicant's design and operating procedures will provide adequate assurance that the auxiliary feedwater start signal on loss of both ~ main feedwater pumps will not be blocked during operating modes when the diversity of this signal is desirable. The applicant's design is, therefore, acceptable. The license'will be conditioned to require the bypassed and inoperable status panel indication described above."
In accordance with the above, the blocking of the TDMFP and associated indication is described in USAR Section 7.3.6.1.1.
There is no need for the Auxiliary Feedwater Actuation function below 5% power, since there is sufficient time for operator actions to occur prior to steam generator levels decreasing to the low-low level reactor trip setpoint.
Should no operator actions occur, the reactor will trip and both motor driven auxiliary feedwater pumps will start when the first steam generator level drops to the low-low level setpoint. Should a second steam generator level reach its low-low level setpoint, the turbine driven auxiliary feedwater pump l
starts. With all 3 auxiliary feedwater pumps, the steam generator levels are rapidly recovered. Procedurally, the signal will be unblocked just after the first TDMFP is placed in service during startups, and will be blocked just prior to securing the last TDMFP during shutdowns.
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, During a normal shutdown of the main feedwater pumps, and also during.the startup of the main feedwater pumps, the automatic initiation signal for the auxiliary feedwater system should be blocked. This will allow for greater operational flexibility during normal shutdowns and startup of the plant when automatic initiation of auxiliary feedwater flow, upon the trip of both main feedwater pumps, is not needed.
The proposed revision to'the TS clarifies the conditions upon which the i
automatic initiation signal for. auxiliary feedwater flow upon a loss of main-feedwater flow can be blocked. The proposed wording is consistent with the staff's SER on the Wolf Creek Plant.
In addition, the accident analysis in Chapter 15 of the FSAR states that no credit is taken for the signal to 1
initiate auxiliary feedweter when the main feedwater pumps are tripped. Thus, the staff finds the proposed change acceptable.
ENVIRONMENTAL. CONSIDERATION The amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The staff has determined that the amendment involves no significant increase in the amounts, and no'significant change in the types, of any effluents that may be released offsite, and that there is no significant increase ~1n individual
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or cusolative occupational radiation exposures. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in.10CFRSection51.22(c)(9). Pursuantto10CFR51.22(b),noenvironmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
CONCLUSION The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the Commission's regulations, and the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Date:
April 3, 1989 Principal Contributor: Douglas V. Pickett 1
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