ML20072R159
| ML20072R159 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/18/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20072R156 | List: |
| References | |
| NUDOCS 9103220216 | |
| Download: ML20072R159 (4) | |
Text
{{#Wiki_filter:_ _ - _ - - _ _ _. pnR8009 +4 k UNITED STATES [ g NUCLEAR REGULATORY COMMISSION in 8 WASHlfv0 ton, D. C. 205B5 1 + ....+ ENCLOSURE 3 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. ISO TO FACILITY OPERATING LICENSE NO. DPR-77 AND AMENDMENT NO.140 TO FACILITY OPERATING LICENSE NO. DPR-79 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NOS S0-327 AND 50-328
1.0 INTRODUCTION
In its letter dated November 20, 1990, the Tennessee Valley Authority (TVA) proposed to modify Section 3/4.6.2, Depressurization and Cooling Systems, of the Sequoyah Nuclear Plant (SQN), Units 1 and 2, Technical Specifications (TSs). The proposed changes are to revise the Limiting Condition for Operation (LCO) 3.6.2.1 for the containment spray system to clarify the operabilit requirements for cont..inment spray (CS) and residual heat removal (RHR) y spray. TVA stated that this clarification is to ensure that an entire train of CS and RHR spray (i.e., all Train A or all Train B CS and RHR spray com-ponents) is operable when in the action statement for LCO 3.6.2.1 The action statement associated with this LC0 would also be revised to a subsystem approach (similar to TS 3.5.1 for emergency core cooling system) that requires two independent subsystems comprised of a pump, heat exchanger, and flow path for both CS and RHR spray. In addition, the index and bases would also be revised. This is TVA TS Change Request 90-16. 2.0 EVALVATION Containment heat removal during accidents is discussed in Section 6.2.2 of the Sequoyah Final Safety Analysis Report (FSAR). This heat removal is provided by the ice condenser, the air return fans, and the two separate systems that provide containment spray. These containment spray systems are the above listed CS system and RHR spray system. The RHR spray system is a portion of the RHR system. Each of these spray systems consist of two trains of redundant spray eg'Jipment (i.e., pumps, heat exchangc:s. control valves, spray headers) for each unit. There are four spray headers per unit: two headers supplied from separate trains of the CS system and the other two headers supplied from separate trains of the RHR spray system. The CS system initially operates independently of the RHR spray system and other engineered safety features. The CS pur:ps operate first from the refueling water storage tank and then from the containment sump. For extended operation, water is supplied to the RHR spray headers from the RHR pumps and heat exchangers. The RHR spray system is for long-term containment spray, 9103220216 91031e fR ADOCK 05000327 PDR
-2 The RHR spray trains are not considered redundant to the CS trains in responding to an accident because the CS trains are for initial containment spray and the RHR spray trains are for long-term containment spray. Therefore, both the CS train and the RHR spray train which are powered from the same vital bus (i.e., Train A or Train B) must be operable for that train of containment spray capability S be considered operable. In its application for amendments to the TSs, TVA stated the^ the current LCO 3.6.2.1 referring to the separate trains of CS and RHR spray has led to confusion as to which pumps are allowed to be inoperable and be within the action statement requirements of the LCO and has caused Operations' personnel to be unsure of when TS 3.0.3 would be applicable. TVA has proposed to classify the trains of the CS and RHR spray as subsystems of an overall containment spray system and to revise the TSs accordingly. TVA stated that this revision to the TSs will resolve this confusion because there will be assurance that an entire containment may subsystem is available when in the action statement for LCO 3.6.2.1 and.ae requirements of TS 3.0.3 will be complied with when there is loss of equipment in both subsystems. A subsystem would be Train A or Train B of both CS and RHR spray. This clarification would ensure that at least one train of containment spray system components are available as assumed in th' accident analysis to supply a minimum spray flow of 6.750 gallons per minute (gal / min). This flow is achieved by having at least one complete subsystem with a CS pump capable of delivering 4,750 gal / min of spray and an RHR pump capable of delivering 2,000 gal / min of spray. The title changes in the index and bases have been proposed to provide consistency with the LC0. TVA stated that these changes do not alter the operation, testing, or maintenance of the containment spray system or RHR system. The current LC0 3.6.2.1 treats the two trains of CS and the two trains of RHR spray as separate systems, as described in FSAR Section 6.2.2. Each train in the LCO is a pump, heat exchanger, and a flow path from a source to the spray header. In the current action statement for LC0 3.6.2.1, if one train of CS or RHR spray is inoperable, the inoperable spray train is returned to operable status within 72 hours or the unit is put into at least hot standby within the next six hours. The action statement does not explain what to do if more than one train is inoperable. This means that if one CS train and one RHR spray train are inoperable, the situation is outside the action statement for LCO 3.6.2.1 and, therefore, LC0 3.0.3 would apply. LCO 3.0.3 would require that one train be made operable within one hour or the unit be in at least hot standby within the next 6 hours. If the two trains are powered off different vital buses, it could be appropd ate to enter LCO 3.0.3 but, if the two trains were powered off the same vital bus, it would not be appropriate to enter the more restrictive LC0 3.0.3. For a CS train and a RHR spray train powered off the same vital bus (i.e. Train A or Train B), it does not matter whether the C1 ~ain or the RHR spray train or both trains are inoperable. In all cases, tr., current action statement for LCO 3.6.2.1 is appropriate. The train (s) should be made operable within 72 hours or the unit should be in at least hot standby within the next 6 hours. This is true because the CS and RHR trains are powered from the same vital bus. If that bus was lost in a single active failure, both the CS and RHR spray trains po.vered from that bus would be inoperable but there would remain an operable CS train and RHR spray train powered from the other vital bus. Therefore, the current requirements in the action statement for LCO 3.6.2.1 would be e.cceptable for the loss of one train of CS and RHR spray (i.e., Train A or 1 rain B).
. for a CS train and a RHR spray train that are not powered from the same vital bus to be inoperable, the current action statement for LCO 3.6.2.1 is not appropriate. This situation is outside the action statement.because if a vital bus were lost there would remain only one operable CS train or RHR spray train and both trains would be needed for there to be an operable train of containment i spray. The current wording in the LCO.3.6.2.1 in terms of containment spray trains is too restrictive in that it may require an unnecessary rapid shutdown if both a CS train and a RHR spray train wh'ch are powered from the same vital bus are inoperable. TVA has proposed to revise the LCO in terms of containment. spray subsystems with a subsystem being a CS train and a RHR spray train powered off the same vital bus. Therefore, if on' " subsystem" is inoperable, TVA should restore the inoperable subsystem to opeioble status within 72 hours or place the unit in at least hot standby within the next 6 hours. if both subsystems are inoperable, the situation.is clearly outside the action statement and TVA would enter LCO 3.0.3. Based on the above, the staff concludes that the TSs should be written in terms of contair.inent spray subsystems instead of CS trains and RHR spray trains. This is consistent with the description of containment spray in the FSAR. The L staff has reviewed the proposed changes to add the phrase " subsystem" to LCO t 3.6.2.1 and agrees that they are consistent with the concept of containment spray subsystems where one CS train and one RHR spray train powered off the same vital bus is a subsystem. The proposed action statement is consistent l with the current requirements in the action statement being followed if a subsystem is inoperable and-with LCO 3.0.3 being followed if both subsystems i l are inoperable. Both the CS train and the RHR spray train must be operable for the subsystem to be considered operable, as re,: ired by LCO 3.6.2.1. The staff concludes that these propose 11 changes are ace N able. TVA has also proposed adding the phrases " containment spray pump" and " residual heat removal pump" to LC0 3.6.2.1 to describe the two flow paths in the containment spray. These flow paths are through the containment spray pump (i.e., CS train) and the residual heat removal pump (i.e...RHR spray train). Therefore, the proposed descriptive wording is correct. The staff concludes that these proposed changes are acceptable. i TVA also proposed to add the phrase "and supplying flow to the spray header" 'to assure that the entire flow path from the source to the spray heador is operable for the RHR spray train to be considered operable. The RHR system uses' the same RHR pumps for its primary function to pump water directly into i the core to cool it under low pressure conditions. Switching RHR pump flow to the RHR spray headers means realigning valves to a new configuration and pumping water-to the spray headers. This flow path to the headers must be I operable for the RHR spray train to be merab b. The staff concludes that this additional descriptive information for LC0 3.. 2.1 is necessary and the proposed change is acceptable. This additional descriptive information is not needed for the CS train because the containment spray pumps only pump water to the CS headert. Finally. TVA proposed to change the title of LC0 3.6.2.1 to " containment [ spray sjstems." This involves changes to the index and TS Bases for LCO i 3.6.2.1. 91s new title is consistent with the revisions to LC0 3.6.2.1 which were discussed above and the new LC0 3.6.2.1 which is in terms of containment spray subsystems. Therefore, the staf f concludes that these changes are acceptable.
~ 1 Based on the above, the staff concludes that the TS changes proposed by TVA in its application dated November 20, 1990 are acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
These amendments involve a change to a requirement with respect to the as defined in 10 CFR Part 20. installation or use of a facility component located w The staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be rciersed offsite, and that there is no significant increase in individual or cumulative occupational radiation The Commission has previously issued a proposed finding that these exposure. amendments involve no significant hazards consideration and there has been no public comment on such finding. Accordingly, the amendments meet the eligibility criteria for categorical exclusion !e+ furth in 10 CFR 51.22(c)(9). assessment need be prepar(ed in connection with the issu
4.0 CONCLUSION
The Commission made a proposed determination that the am (55 FR 51187) on Decenber 12, 1990 and consulted with the State of~~ ~ Tennessee. not have any comments.No public comments were received and the State of Tennessee did The staff has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safet will not be endangered by operation in the proposed manner,y(2) such activities of the public will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense a security nor to the health and safety of the public. Principal Contributor: J. Donohew Dated: March 18, 1991 y =.....}}