ML20085F051
| ML20085F051 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 10/16/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20085F048 | List: |
| References | |
| NUDOCS 9110220017 | |
| Download: ML20085F051 (4) | |
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UNITED ST ATES
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a wn.HiNot ow. o. c. 20shs SAFELY EVAtVATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION R_ ELATED TO AMENDMENT NO.126 TO FACILITY OPERATING LICENSE NO. NPF-6 ENTERGY OPERATIONS, INC.,
AR_ KANSAS NUCLEAR ONE, UNIT NO. 2 DOCKET NO. 50-368 1.0 INTR 000CT10N In NRC Generic Letter 88-17, the staff identified a concern regarding potential loss of decay heat removal (DHR) due to air ingestion into the shutdown cooling (SDC) system as a result of vortexing during reduced reactor coolant system (RCS) inventory operation.
A high SDC system flow rato contri-butes to the likelihood that air will be inDested which could bind the SDC pumps and result in ptmp cavitation and the loss of DHR.
The staff recommended that licensees should evaluate and propose changes to the Technical Specifica-tions (TS) limiting condition for operation (LCO) on SDC system flow rate to enhance the overall rollability of SDC system operation.
By 1 Hter oated February 25, 1991 (Ref. 1), Entergy Operations, Inc., proposed changes to the TS for Arkansas Nuclear One, Unit 2 (ANO-2).
This was for TS 3/4.1.1.3 and the associated Bases 3/4.1.1.3 to reduce the required SDC system flowrate during Mode 5 operation.
Additional information was supplied in a telecon (Ref. 2).
At the currently required flowrate of 3,000 gpm the SDC system could be susceptible to vortexing at the SDC pump suction piping during RCS partial drain operation.
The licensee propMed a reduction of the SDC flowrate to 2,000 gpm in T5 3/4.1.1.3 and Bases ~3/4.1.1.3.
Also, the licensee proposed to change the applicable pump in TS 3/4.1.1.3 f rom a low pressure safety injection pump to either a low pressure safety injection or containment spray pump for use in shutdown cooling.
The licensee had previously proposed a similar amendment to reduce the minimem SDC loop flow from 3,009 gpm to 2,000 gpm for Mode 6 operation by letter daad December 15, 1989.
On April 30, 1990, the staff approved the flow reduction for Mode 6 operation and issued Amendment No. 104 to the facility Operating I
License.
2.0 EVALUAT10tj 2.1 Adequate Flow to Remove Decay Heat Operation with the RCS partially drained in Modes 5 and 6 is necessary for required inspection and maintenance of RCS components such as reat. tor coolant pamos and steam generators.
As indicated in NUREG-1269 (Ref. 3), reduced SDC 9110220017 911015 PDR ADOCK 05000363 P
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system flowrate would provide a greater margin against vortexing and preclude an inadvertent loss of decay heat removal captbility due to air entrainment and cavitation of the SDC pumps.
As the time after plant shutdown increases, decay heat removal requirenents from the SDC suctica flow are reduced since decay heat decreases as a function of time af ter initial reactor shutdown.
For ANO-2
-the Combustion Engineering (CE) Owners Group has recommended a minimum flowrate of 2,000 gpm for the SDC system.
The 2,000 gpm value is limited by the potential for excessive wear in the pumps.
The proposed TS change wt require that the SDC flowrite be maintained at least equal to or greater than. 000-gpm.
ANO performed a vortexing test to determine the level at which vortexing would occur at various flow rates.
This test verified that the proposed 2,000 gpm was acceptable with a minimum RCS level of 10 inches above the bottom of the RCS hot leg.
An RCS level of 19 inches is the procedurally required minimum level for SDC operation.
The change proposed by Entergy has been evaluated by the licensee to provide sufficient flowrate to maintain the RCS at equal or less than 200'F as required for Mode 5 cperation.
Operation at the reduced flow rate of 2,000 gpm was previously approved for Mode 6 operation.
i The staff f.herefore finds that the proposed TS change provides reasonable assurance that. adequate flow to remove decay teat will be available during Mode 5 operation, whilu the potential to vortexing is minimized.
2.2 Adeauate flow t.o Ensure Mixing Entergy and CE evaluated the effect of reduced RHR flowrate on the Find! Safety Analysis Report (FSAR) boron dilution accident analysis and determined that the reduction in flou*M e does not impact the results of tne. analysis.
The staif considers that the consequences of a boron dilution event when the SDC fluw rate is 2,000 gpm are bounded by the FSAR analysis, 2.3 Use of the Containme.it Spray Pump for Shutd9wn Cooling The licensee proposed that the containment spray pump be added as an optional pump for use during the shutdown cooling operation.
This is in addition to the low presst.re safety injection pump currently specified in TS 3/4.1.1.3.
The piping configurations for ANO-2 allows use of either the low pressure safety injection pump or containment spray pump for heat removal.
The purpose is to have more flexibility for scheduling maintenance on the pumps.
The staff considers the use of the containment spray pump to be acceptable as it has the required capacity and safety qualification for the SDC operation.
3.0 EVALUATION OF TECHNICAL SPECIFICATIONS
-As a result of reducing the minimum residual heat removal tiowrate and adding the use of the containment spray pump, changes to the plant's TS were proposed.
The-following TS were examined.
Change 1 TS 3/4.1.1.3, page.'./4 1 Boron Dilution The reference to a mir.imum flow of 3,000 gpm was changed to 2,000.
This is acceptable as explained in Section 2.0.
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-3a Chance 2 TS 4.1.1.3, page.3/4 1-4 Surveillance Requirements for Boron Dilution In addition to the use of the inw pressure safety injection pump the containment spray pump was added as an option for une in the shutdown cooling operation.
This is accept-able as the containrent spray pump has the proper characteristics and provides for more flexibility in periorming the task.
Chance 3 Bases 3/4.1.1.3, page B 3/4 1 Boron Dilution The reference to a minimum flow of 3,000 gpm was changed to 2,000.
This is acceptable as explained in Section 2.0.
Also, +.he cubic feet pumped in 75 minutes was changed from 9,975 cubic feet to 6,650 cubic feet.
This change is acceptable as it represents the reduction in cubic feet pumped for the lower flowrate.
The proposed TS changes include a reduction in the shutdown cooling system flowrate during operation in Mode 5 as was previously approved for Mede 6.
Also, the containment spray pump was added as an optional pump for use during the shutdown cooling operation.
The changes are consistent with the position of Generic Letter 88-17 and were found to be acceptable as discussed in Section 2.0,
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Arkansas State official was notified of the proposed issuance of the amendment.
The State official had no comments.
5.0 ENVIRONMENTAL-CONSIDERATION The amendment chan0es a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendment involves no signifi-cant increase in the amounts, end no significant change in the types, of any I
effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation expnsure.
The Commission has previously issued a proposed finding that the amendment involves na significant haznrds consideration, and there has been no'public comment on such finding (56 FR 20035).
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment l
need be prepared in coanoction with the issuance of the amendment.
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6.0 CONCLQ510N l
lhe Commission nas concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the ht alth and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amenoment will not be inimical to the corrmon defense and security or to the health and safety of the public.
7.0 REFERENCES
1.
Letter, Neil S. Carns Entergy Operations, Iric., to USHRC, dated February 25, 1991.
2.
Telecon, Curt Taylor, Entergy Operations, Inc., and USNRC, August 28, 1991.
3.
NUREG-1269, " Loss of Residual Heat Removal at Diablo Canyon Unit 2."
Principal Contributor:
H. Balukjian I
Date:
October 16, 1991 i
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