ML20212G937
| ML20212G937 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 10/29/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20212G942 | List: |
| References | |
| NUDOCS 9711070221 | |
| Download: ML20212G937 (4) | |
Text
'
cD *t ov C
UNITED STATES s
,j NUCLEAR REGULATORY COMMISSION WASHINQTON. D.C. 30h0001
... +,o RLy1 SED SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS. 125 AND 117 TO FACILITY OPERATING LICENSE NOS. DPR 42 AND DPR 60 NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT. UNIT NOS. 1 AND 2 DOCKET NOS. 50 282 AND 50 306
1.0 INTRODUCTION
By letter dated August 15, 1996, the Northern States Power Company (NSP or the licensee) requested amendments to the Technical Specifications (TS) appended to Facility Operating License Nos. DPR 42 and DPR 60 for the Prairie Island Nuclear Generating Plant, Unit Nos. I and 2.
The proposed amendments would revise TS 3.3.B.2.
TS 3.3.B.2 specifies operability requirements Sr operation of the containment cooling systems.
2.0 DISCUSSION AND EVALUATION 2.1 Oriainal Licensina Basis for prairie Island Containment Coolina Systems The containment cooling systems for each unit include two diverse methods of post accident containment cooling:
the containment spray system and the containment fan cooler system. These systems are engineered safety features whose safety functions are to cool the post accident internal containment atmosphere.
Each system consists of two independent, redundant trains. Each of the two trains of the containment spray system is provided with a
> ump that discharges to containment spray nozzles.
Each of the two trains of tie fan cooler sy!, tem has two fan coil units that transfer heat in the containment atmosphere to cooling water circulating through the fan cooler coils. The containment fan cooler system is used during normal operation in addition to providing a post accident safety function. The two trains of the containment spray system are provided with a common (i.e., shared) sodium hydroxide filled spray additive tank that enables the containment spray system to serve the additional safety function of pH reduction. The pH control function promotes containment atmosphere iodine removal to minimize offsite and control room radiological dose consequences due to containment leakage (offsite dose, but not control room dose criteria can be met without credit for the spray system iodine fission product removal safety function).
During normal warm weather operation, fan coil units are supplied with cooling water from a nonsafety grade chilled water system.
During normal cold weather operation and during accident conditions, the fan coil units are supplied with cooling water from the safety grade Cooling Water System (river water). The
~
9711070221 971029 DR ADOCK 0 2
l p.
2-containment spray system water sup)1y is from the RWST [ refueling water storage tank] prior to recirculation switclover, and, following switchover (if operated), it is from the ECCS at a point downstream of the RHR heat exchanger.
(As a result of Information Notice 87 63, ' Inadequate Net Positive Suction Head in Low Pressure Safet operating procedures]y Systems," RHR puma runout studies, E0Ps (emergencywere revise after switchover.)
As originally desi ned, in the event of a design basis accident, any one of 3
the following comb nations of containment cooling systems trains would provide sufficient containment cooling:
Both trains of the containment fan cooler system (i.e., four fan coolers), or Both trains of the containment spray system, or One train of the containment spray system and one train of the containment fan cooler system.
These combinations meet General Design Criteria 41 and 52 and provide the basis for the current TS 3.3.B.2.
2.2 Findinas of Licensee's Reanalysis In 1995, the licensee developed an analytical model of the cooling water system to better understand and evaluate its capabilities. The licensee subsequently found that under post accident conditions, system pressure would be so low that boiling could occur in the upper level fan coolers.
The j
licensee then performed containment pressure analyses using the CONTEMPT code to evaluate the effect.
The licensee found that, for a loss of coolant accident (LOCA), the design basis requirements for containment pressure response could be met with one spray train and one fan cooler during injection and one fan cooler during recirculation (spray secured during recirculation), but could not be met with four fan coolers and no spray.
The licensee found that for a main steam line break (MSLR), design basis pressure response criteria were met with one s) ray train.
(Due to the higher containment temperatures associated with an MS.B. the licensee's analysis conservatively assumes that all four fan coil units are unavailable for that event.)
New radiological analyses also confirmed that containment spray is not needed for offsite dose mitigation, but is needed for LOCA control room dose j
mitigation.
3-In view of the above findings, the current TS 3.3.B.2 does not ensure adequate containment cooling and fission product control for all postulated design basis accidents when equipment is operating under certain permitted operating conditions.
2.3 Proposed TS Chanaes The TS would be such that the allowed completion times to restore inoperable equipment would reflect the results of the new analyses. The completion times would not be dependent on the operability status of the fan cooler system.
Similarly, the completion times for inoperable containment fan cooler units would not be dependent on the operability status of the containment spray system. The completion times for inoperable fan cooler units would be deleted and replaced by completion times for inoperable fan cooler trains.
Under the pro)osed TS, one train (two units) of containment fan cooling would be allowed to se out of service for up to 7 days.
One train of spray would be allowed to be out of service for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The spray additive tank would be allowed ott of service for up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Th-aff has established standard generic criteria for completion times in the event required equipment is inoperable. These criteria are:
7 days of continued operation is permitted while in a degraded condition if an additional single failure (including loss of an AC power subdivision) could be tolerated.
72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of continued operation is permitted if the operable containment cooling systems are sufficient.
Commence a shutdown if a safety function is completely lost.
The 7 day completion time for an inoperable train of fan cooling is based on the redundant heat removal capabilities afforded by combinations of the containment spray system and containment fan cooler system and low probability of a design basis accident occurring during this >eriod. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> completion time for an inoperable spray train is )ased on the redundant heat removal capabilities afforded by the containment spray system and containment a
fan cooler trains. reasonable time for repairs, and low probability of a design basis accident occurring during this period. These changes have been proposed to conform the TS to the results of recent Prairie Island containment cooling analyses.
The proposed containment cooling systems corpletion times are consistent with the staff criteria.
They are also consistent with NUREG 1431 Standard Technical Specifications, Westinghouse Plants.
Because the findings by the licensee indicate that the containment spray system will not adequately mitigate a design basis accident if no pH adjustment is provided and because a common spray additive tank supplies both containment spray trains, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed outage time is judged by the
k 4
licensee to be excessive.
Lack of spray additive during a design basis LOCA would result in partial loss of the s> ray systems' iodine removal safety function (but no loss of containment leat re.noval capability). A 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> completion time has been conservatively selected to reflect the importance of the iodine removal safety function for control room dose control and the fact that it is a highly reliable (assentially passive) system that can be quickly restored if found inoperable Based on these factors, the proposed 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> h
allowed outage time for the spray additive tank is acceptable. Also, the L
staff finds it acceptable that the interdependencies of the fan cooler units and the containment spray pumps have been eliminated, allowing one train of containment fan cooler units co be inoperable for 7 days and one cont * ^
spray train to be inoparable for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The staff also agrees wi o -
licensee's assessment that at least one containment spray pump shor 6
required to be operable and, therefore, the deletion of the technii
}
specification allowing one pump to be inoperable is acceptable.
3.0 STATE CONSIILTATIOR In accordance with the Commission's regulations, the Minnesota State official I
was notified of the proposed issuance of the amendments. The State official had no comments, k
4.0 MyJRONMFEAL ONSIDERATION The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as definad in 10 CFR Part 20. The NRC staff has determined that the emendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be releeced offsite. and that there i= no significant increase in individual or cumuletive occupational radiation exposure. The Commission has previously issued a proposed finding that the l
amendments involve nc significant hazards consideration and there has been no public ccmment on such finding (61 FR 64388). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental im3act statement or environmental assessment need be prepared in connection wit 1 the issuance of the amendments.
5.0 CONCLUSION
The Commit *, ion has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will nSt be endangered by ;peration in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations.
I l
and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public. Therefore; h'
the staff concludes that the proposed changes are acceptable.
Principal Contributor:
W. Long Date:
February 10, 1997 Rev4ed: October 29, 1997 l
...w
_ _ _ _ -.. _ _ _.__