ML20236C912
| ML20236C912 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 10/16/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20236C904 | List: |
| References | |
| NUDOCS 8710270396 | |
| Download: ML20236C912 (3) | |
Text
-_. -
9 MOO UNITED STATES
[
~'g NUCLEAR REGULATORY COMMISSION
- 5 7 8 WASHINGTON,0 C. 20555 k.....
i I
I SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION t
RELATED TO AMENDMENT NO. 9 TO FACILITY OPERATING LICENSE NO. DPR-22 j
NORTHERN STA'TES POWER COMPANY MONTICELLO NUCLEAR GENERATING PLANT j
DOCKET NO. 50-263
1.0 INTRODUCTION
By letter dated October 3,1986 as revised Decemb'er 8,1986, Northern States 4
Power Company (NSP) requested a change to the Technical Specifications for Monticello Nuclear Generating Plant. The change reflects a modification which i
replaced the Station Auxiliary Transformer No. 11 (unit auxiliary transformer energized by the main generator) by transformer No. 2R (start-up transformer energizedbythe345kVoffsitesourceofpower). The new transformer was installed during the 1986 refueling and maintenance outage.
L The amendment' changes the Technical Specifications in Section 3.9 A.1 to reflect the inclusion of the new transformer as an additional immediate source of offsite power. The change in Section 3.9.B.2 imposes a 72-hour LCO when the condition in Section 3.9.A.1 is not met. The changes also include some minor rewording of nomenclature in the bases of Section 3.9.
2.0 DISCUSSION AND EVALUATION The original design included one start-up transformer (1R) energized by the 345kV offsite power, a unit auxiliary transfomer (11) energized by the main generator, and a back-up shutdown transformer (1AR) capable of providing preferred power to j
safety buses only. Transfomer 11 provided all stction loads when the plant was in operation while the transformer 1R supplied all station loads during start up and shutdown loads after unit trip as the first and immediate source of offsite power.
If transfer of loads from transformer 11 to IR failed or the IR trans-former was not available, the safety loads would automatically transfer to the 1AR transformer. The original design had two sources of offsite power for safety-related loads. The normal source of power to station buses was transformer 11 which was only available while the plant was in operation. Also the immediate source of offsite power was dependent on the successful operation of fast transfer scheme. The modification eliminates the main generator dependent transfomer 11 and also eliminates dependence on successful transfer of shutdown loads. The new design has all three transformers (IR, 2R and 1AR) energized by the offsite source of power, thus providing an additional (total of three sources) source of offsite power. The new transformer is also equipped with an automatic load tap changer and has lower impedance than the transformer it replaced. These features will provide better voltage regulation on the plant power distribution system.
The licensee has infomed the staff that the existing switchgear has enough margin to accommodate higher available fault current due to the lower impedance of the j
new transformer.
87102703Y6 071016 PDR ADOCK 05000263 P
. In the original design, the transfer of station loads including the safety loads was from transformer 11 to transformer IR and 1R to 1AR of only the safety loads.
The licensee')rovided the icyic scheme on July 11, 1987, which is essentially the same as t1e original except for.the nomenclature change. Since the new design does not have any effect on safety and does not adversely affect'the staff's previous decision.regarding the acceptability of the offsite power sources, the staff finds.the new design acceptable.
J The Technical Specification changes proposed by the licensee include two major changes concernina limiting condition of operation requirements (TS section 3.9):
The first change involves one of the requirements for critical reactor operation.
Previously, both 1R and 1AR were required to be fully operational and energized to carry power to the plant 4160v ac buses. However, with the new revised Technical Specification, any two of the three offsite power sources (1R, 2R and 1
l 1AR) can carry power to the plant 4160v ac buses. This change meets the NRC requirement of two separate and independent power sources, prior to critical reactor operation, and is acceptable.
q The second change involves the condition during reactor operation when two out of the three offsite power sources are.not availabic. The proposed technical j
specification requires that, during this condition, continuous plant operation-4 is permissible for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> provided that either the IR or 2R transformer is operable. Since the proposed change is more conservative with respect to the reliability of sources available during continuous power operation compared to the present Technical Specification where no time limit is specified, this change 1
is acceptable.
j The proposed amendirent includes an additional source of offsite power to the plant electric distribution system which improves the reliability of the preferred power i
source to the class IE electric equipment. Also, due to a better voltage regula-j tion on the safety buses, the probability of degraded voltage on class 1E electric equipment is reduced.
I l
4.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a change to a requirement with respect to the installa-tion 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 signifi-
)
ca<t 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 in individual or cumulative occupational radiation exposure. The Comission has areviously issued a proposed finding that this amendment involves no significant lazards consideration and there has been no public coment on such finding.
Accordingly, this amendment meets the eligibility criteria for categorical exclus-ionsetforthin10CFR51.22(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 this amendment.
^~
2 L - 5.0' CONCLUSION' The staff has concluded, based on the considerations discussed above, that:
(1) therelis reasonable assurance that the health and safety of the public will l
not be endangered by operation in the aroposed manner;.and (2) such' activities L
will be conducted in compliance with tie Comission's regulations and the l
. issuance of this amendment will not te inimical to the common defense and security or to the health and safety of.the public.
1
- Principal Contributor:
IQBAL AHMED Dated: October 16, 1987 I
_