ML20217C079
| ML20217C079 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 02/23/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20217C032 | List: |
| References | |
| NUDOCS 9803260281 | |
| Download: ML20217C079 (4) | |
Text
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30646 4 001 o
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULAT!.2N_
RELATED TO AMENDMENT NO.139 TO FACILITY OPE. RATING LICENSE NO. NPF-38 ENTERGY OPERATIONS. INC.
WATERFORD STE AM ELECTRIC STATION. UNIT 3 DOCKET NO. 50-382
1.0 INTRODUCTION
By application dated May 24,1997, Entergy Operations, !nc. (the licensee) submitted a request to change the Waterford Steam Electric Station, Unit 3 (Waterford 3) Technical Specifications.
The proposed changes would mooify Table 3.7-3 of TS 3/4.7.4 to incorporate more restrictive fan operability requirements and revise the TS Bases to reflect changes in the wet cooling tower water consumption. The proposed change is necessary as a result of revised design basis calculations. Specifically, the change to TS Table 3.7-3," Ultimate Heat Sink Minimum Fan Requirements per Train," would be revised to eliminate allowance for operation with fewer than 12 dry cooling tower fans (out of 15 total) per dry cooling tower.
2.0 DISCUSSION The ultimate heat sink (UHS) at Waterford 3 is redundant and consists of two forced draft dry cooling towers (DCTs) and two mechanical draft wet cooling towers (WCTs) with water stored in 3
the basins of the WCTs. Each train of the UHS uses one DCT and one WCT, which are essentially in series. During normal plant operation, two component cooling water (CCW) system loops supply cooling water to all the plant loads using the DCTs for final heat removal. Although the DCTs are the primary heat sink for the CCW System, each CCW loop also has a CCW heat exchanger, which is supplied cooling water from an auxiliary componem cooling water (ACCW) system train, which uses one of the two WCTs for heat removal. CCW flows through the CCW heat exchanger whenever the CCW system is in operation; ACCW flow is supplied to the CCW heat exchanger whenever the DCT is not adequate to maintain CCW temperature within the desired range. The ACCW system and WCTs are designed to operate following an accident and whenever the heat rejection capacity of the DCTs is exceeded or ambient environmental conditions prohibit the DCTs from rejecting their design heat load. Each DCT is sized to dissipato approximately 60 percent of the heat removed by the CCW system following a design basis lo ss of coolant accident (LOCA) while each WCT is sized to dissipate approximately 40 percent af this design basis heat load. Therefore, each train of the UHS, consisting of a DCT train and c WCT train, is designed to dissipate 100 percent of the heat load under the worst case design basis accident conditions.
9003260281 980223 PDR ADOCK 05000382 P
2 The DCTs are forced draft, dry type, parallel flow heat exchangers with each tower consisting of five separate cells. Each cell contains two 40 foot finned vertical cooling coils with forced cooling air flow on the outside of the tubes that is supplied by three fans for each cell. Therefore, there
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is a total of 15 fans for each DCT. The DCT fans are started and secured automatically to maintain the CCW system temperature at a predetermined value measured at the outlet of the CCW heat exchanger. When the CCW temperature in a CCW loop exceeds that value, the associated ACCW pump starts to initiate additional CCW cooling via the WCT.
The WCTs are mechanical draft, wet type, mixed flow heat exchangers with each tower consisting of two cells. Each cellis serviced by four induced draft fans for a total of 8 fans per WCT. There is a concrete partition that prevents air recirculation between the fans of each cell.
The WCT fans are automatically started whenever the water temperature in the WCT basin exceeds a predetermined setpoint, and continue to run until they are shut off by the operator.
Unlike the DCTs, the forced air actually contacts ACCW during the heat removal process.
ACCW enters the WCT and is sprayed downward towards the basin into fill modules separating the water into droplets. Air is drawn upward through the modules and spray area by the fans, which are located at the top of the tower.
Recent analyses by the licensee have determined that the post accident heat load assumed in the UHS transient heat analysis was not conservative in that the analysis did not consider the condition of maximum heat removal from containment and maximum heat transfer to the UHS as a result of clean heat exchangers. Additionally, the analysis did not consider the spent fuel pool as a possible heat load following a LOCA. The previous analysis, while conservative from the standpoint of containment response, was not conservative as a basis for the minimum number of Operable DCT fans, nor as a basis for the amount of water consumed from the WCT basins following a design basis LOCA. As a result of this determination the licensue has proposed to eliminate operation with fewer than 12 DCT fans operating and is revising the Bases for TS 3/4.7.4 to correct the WCT water consumption following a LOCA.
3.0 EVALUATION i
Currently, Table 3.7-3 allows continued plant operation with a minimum of 9 Operable DCT fans per train when dry bulb ambient temperature is less than 77 degrees fahrenheit (77'F). With dry j
bulb temperature less than 91*F but greater than or equal to 77'F at least 12 fans are required i
to be Operable. For dry bulb temperature greater than 91*F but less than 98'F,14 fans are
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required to be Operable and for dry bulb temperatures greater than 98'F, all 15 fans are required to be Operable. The proposed change would re:luire at least 12 Operable fans at all I
temperatures below 91 *F. Thus, continued operation with fewer than 12 Operable fans (i.e.,
more than 3 inoperable fans) will not be allowed regardless of the temperature. The current TS allows operation with more than 3 inoperable fans (up to a maximum of 6 inoperable fans) whenever dry bulb ambient temperature is less than 77'F. The revised analysis has shown that operation with more than 3 inoperable fans could continue at temperatures below 75'F without exceeding any limits. Therefore, the proposed change to require at least 12 Operable fans below 77'F is more conservative than the existing TS and is also conservative with respect to the latest i
analysis. The proposed change is acceptable on the basis of that conservatism.
The current Bases section for TS 3/4.7.3 identifies that the water consumption of one WCT for the design basis LOCA (assuming only one train is operating) is less than the required minimum
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volume of 174,000 gallons for each WCT basin (based on a 30-day post-LOCA analysis). The revised Bases section will still reflect that water consumption following a LOCA will be less than the required minimum volume of one basin without consideration of the spent fuel pool as a heat load. However, the Bases Section has been further revised to reflect that when the spent fuel pool heat load is factored in, the water consumption rate may result in exceeding the minimum required volume of one WCT basin (prior to 30 days). The Bases Section now reflects that up to I
218,155 gallons of water would be consumed in the 30 days following a LOCA under the most adverse conditions. The adverse conditions considered in the analysis included: LOCA coincident with a loss of offsite power (LOOP), a single active failure of one electrical division, worst case ambient (meteorological) conditions, inability to restore power to the electrical division within 3 days (if restored the minimum volume of one basin will stilllast 30 days) and non-essential heat loads (including the spent fuel pool) being cooled by the UHS.
The difference in the WCT water basin consumption rate is not considered safety significant because makeup can be provided from the redundant WCT basin via gravity flow through basin cross-connect valves. Additional backup is provided via a gravity flow path from the circulating water system. In the Safety Evaluation Report (SER) for Waterford 3, NUREG-0787, the staff gave credit for the Category I cross-connect between basins and concluded that the UHS provided sufficient cooling for at least 30 days under all design basis conditions in accordance with the guidance of Regulatory Guide (RG) 1.27 " Ultimate Heat Sink." Because of the seismic Category I cross-connect, it was not necessary to demonstrate that the volume of one WCT basin was sufficient to last 30 days following a design basis LOCA. The staff further concluded that the UHS met the requirements of General Design Criterion 44, " Cooling Water," with respect to decay heat removal capability.
Based on its evaluation, the staff concluded that the proposed changes are consistent with Regulatory Guide 1.27 and GDC 44, are based on conservative analysis assumptions and are necessary to reflect the latest UHS transient heat analysis for the Waterford 3 plant. The staff, therefore, concludes that the proposed changes to TS 3/4.7.4 and its Bases are acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Louisiana State official was notified of the proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC 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 l
released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the i
amendment involves no significant hazards consideration and there has been no public comment
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. on such finding (62 FR 33123). Accordingly, the amendment meets the eligibility criteria for i
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4 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 need be prepared in connection with the issuance of the amendment.
6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health 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 amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: W. Lefave Date: March 23, 1998
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