ML18092B480
| ML18092B480 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 09/06/1986 |
| From: | Public Service Enterprise Group |
| To: | |
| Shared Package | |
| ML18092B474 | List: |
| References | |
| S-C-E130-NSE-04, S-C-E130-NSE-4, NUDOCS 8704010142 | |
| Download: ML18092B480 (6) | |
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'CPS~G S-C-El30-NSE-0458, REV. 1 Page Date 1 of 4 9/6/86 TITLE: JUSTIFICATION fOR OPERATION OF UNITS l AND 2 WITH LIMITED 4KV LOADS 1.0 PURPOSE This Safety Evaluation is being written to justify the continued safe operation of Salem Unit No. 1 and Unit No. 2 following the reactor trip/safety injection and subsequent loss of off site power indication which occurred on Salem Unit No. 2 on August 26, 1986.
2.0 SCOPE This Safety Evaluation is applicable to the operation of both Salem Unit No. 1 and Salem Unit No. 2.
3.0 REFERENCES
3.1 u.s. NRC letter "Adequacy of Station Electrical Distribution System Voltages at Salem Units 1 and 2" to F.
- w. Schneider, dated October 21, 1981.
3.2 "Adequacy of Station Electric Distribution System Voltages, Salem Nuclear Power Station Units 1 and 2".
Prepared for U.S. NRC by EG&G Idaho, Inc., June, 1981.
3.3 u.F.S.A.R., Section 3, Section 8, and Section 15.
Rl 3.4
- G.D.C. 17, *Electric Power Systems.
3.5 Public Service Electric and Gas Company Drawings 203061 A8789 and 203062 A8789.
4.0 DISCUSSION
se/SS4 On August 26, 1986,* Unit No. 2 experienced a reactor trip and safety injection followed shortly by a loss of of fsite power to the 4KV Vital A, B, & C electrical busses.
Initially on the safety injection, all safeguards loads loaded simultaneously in accordance with the design.
Subsequent to the safety injection
- an indication of loss of offsite power was received.
The "A" and "C" vital bus loads sequenced onto the diesels as per design.
The "B" vital bus remained deenergized because the "B" diesel generator was tagged for maintenance.
(Two vital 4160 volt buses EDD-7 FORM l REV 0 10SEPT81 The Energy People 95-2 168 t75Ml 12*83
Page 2 of 4 S-C~El30-NSE-0458 REV. l Date: 9/6/86 se/SS4 are required to provide mini~um safeguard~ equirment).
Upon i::vestigat.~on it was
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- investigation r~vealad that a tr~nsi9nt stability analysis had not been performed on the plant since June, 1981.
Plant loads have been modified on the basis of a static loading analysis only.
The changes in plant loads may be found in Attachment No. 1.
The June, 1981 transient stability analysis was performed by Public Service Electric and Gas (PSE&G) and supplied to the U.S. NRC in accordance with a request dated August 8, 1979.
The U.S. NRC then submitted this study to their contractor EG&G, Idaho, Inc. for review.
The U.S. NRC then supplied PSE&G with a Safety Evaluation Report which approved the Salem Unit No. 1 and Unit No. 2 electric distribution system (Reference 3.2).
Section 8.3.1.2 of the UFSAR describes the normal operation of the 4160 volt system which is to switch the non-vital loads from the station power transformer to the auxiliary power transformer after the unit is at approximately 20% power.
Section 8.3 of the UFSAR refer to analysis and tests which were performed to verify that the off site power systems in combination with the onsite power systems possess sufficient capacity and capability to automatically start and subsequently operate all safety loads within their voltage ratings for anticipated transients and accidents.
The worst sustained undervoltage condition in the plant distribution system was found to occur with a severely degraded 500 KV offsite system simultaneous with a conc~rrent LOCA on Unit No. 2 and Unit trip on Unit No. 1, or vice versa.
(Reference 3.2)
This undervoltage condition results from the automatic transfer of the group busses from the auxiliary power R
transformers to the station power transformers and the 1
automatic start of the required vital bus loads.
The reduc~ion of loads to the June 1981 level will ensure that the worst case transient conditions will not affect the capability of the station power transformer to supply sufficient power to the safeguards equipment.
Additionally, the worst case transient may be improved by eliminating the voltage transient caused by the group bus transfer.
The station power transformers have been shown by previous analysis (Reference 3.2) to have sufficient capacity and capability of assuring power to the 4160 volt group and vital busses under the most severe transient conditions as stated in the UFSAR.
Based on these analyses the probability of occurrence or the consequences of an accident or malfunction of equipment important to safety ~s not increased as evaluated in the UFSAR.
Furthermore, the possibility for an accident or malfunction of a different type than previously evaluated in the UFSAR is not created by the alteration of the normal operating configurations.
EDD-7 FORM 1 REV 0 10SEPT81
Page 3 of 4 S-C-El3B-NSE-0458 REV. 1 Date: 9/6/86 The Technical Specification (T.S~ 3/4.8.1.la) requires tha~
two phy3ically lnda~endent circuits between offsite an~
--~i~e Clr.:ss :s distributi,:n sv.::tc*;*..s (Vit::.1 8us:-32s) s\\"'..:3.lL :::,.3 iR operable.
The bases for r.ht: limit.ng condition ot cperd'--"'n l
is that sufficient power be available to supply the safety-related equipment required for the safe shutdown of the plant and the mitigation and control of accident conditions within the plant.
The station power transformers fulfill the function of connecting the offsite and onsite distribution systems as analyzed in the June 1981 study.
By operating the non-vital station loads on the station power transformers instead of the auxiliary power transformer, the margin of safety is not decreased and the operability of the vital buses is not compromised.
This change in operating configuration reduces the transient loading on the station power transformers and therefore enhances the availability of the offsite power feeds to the vital busses.
In addition the complete loss of offsite power is analyzed in Section 15.2.9 of the UFSAR and therefore the altered configuration is within the scope of the UFSAR.
5.0 RECOMMENDATIONS
Since a transient stability analysis has not been performed since June 1981, operation of the Salem Unit No. 1 and Unit No. 2 plants may only be continued when the plant loads are returned to within the values identified in the study and approved by the NRC.
In addition, the plant loads will be supplied from the station power transformers with the auxiliary power transformer group bus infeed breakers open.
This will further remove the potential transient load added to the station power transformers when a group bus transfers from the auxiliary power transformer.
The reduced loads identified in Attachment It will result in more conservative loads than that which were identified in the June 1981 study.
6.0 CONCLUSION
S:
.;e/SS4 The continued operation of Salem Units 1 & 2 is justified on the basis of the discussion above.
Implementation of the above recommendations do not constitute an Unreviewed Safety Question since, a) it does not involve a modification, test or experiment associated with equipment important to safety, but rather the administrative operation of balance of plant equipment, b) it is based on the results of analysis for a modification of a type previously approved by the NRC (Ref.
3.1), c) it recommends the administrative control of operation of non-vital equipment that are not part of the basis for any Technical Specification (See attachment)
- EDD-7 FORM 1 REV 0 10SEPT81
Page 4 of 4 s-c-El30~NSE-0458 REV. 1 Date: 9/6/86
- 7. 0 VENDOH MANU.~L H1PACT None a.o SIGNATURES Ver1f er Group Head Date*
Date (j.7lA44hn"""' /.,,,,,,.. IY'= t;k,- w/ti. ~4:! 9h/e6 Manager -
r Date.
Plant Engineering I.
ss-1h9/5 se/S$4 EDD-7 FORM l REV 0 10SEPT81
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Group Busses Vital Busses Group Busses Vital Busses ATTACHMENT I - Changes in Plant Loads UNIT
~JO. l 11 Station Power Transformer 2000 KVA (2) Cond. Pumps 333 KVA Misc. Subs.
833 KVA Misc. Subs.
3166 KVA Total UNIT NO.
21 Station Power Transformer 6000 KVA ( 3 ) Cond. Pumps 1000 KVA Non Rad Waste 333 KVA Misc. Subs.
833 KVA Misc. Subs.
8166 KVA Total 2
12 Station Power Transformer 22 1000 KVA (1) Cond. Pump 333 KVA Misc. Subs.
833 KVA Misc. Subs.
2166 KVA Total Station Power Transformer 1000 KVA (1) Cond. Pump 333 KVA Misc. Subs.
833 KVA Misc. Subs.
2166 KVA Total
ATTACHMENT II Equipment tc be aut of service to obtain reduction. of Station Power Transformer Loads 11 Station Power Transformer must reduce by 3166 KVA, any of the following may be removed from service to total 3166 KVA.
11 Cond. Pump -
4000 KVA*
12 Cond. Pump -
4000 KVA 11 Heater Drain Pump -
1000 llA Circ. Water Pump -
2000 12A Circ. Water Pump -
2000 13A Circ. Water Pump -
2000 21 Station Power Transformer must reduce by 8166 KVA, any KVA KVA KVA KVA of the following may be removed from service to total 8166 KVA.
11 Cond. Pump -
4000 KVA**
21 Cond. Pump -
4000 KVA 22 Cond. Pump -
4000 KVA 21* Heater Drain Pump -
1000 KVA 21A Circ. Water Pump -
2000 KVA 22A Circ *. Water Pump -.2000 KVA 23A Circ. Water Pump -
2000 KVA
- Out of service presently
- NOTE:
Unit No. 1 equipment UNIT NO. 1 12 Station Power Transformer must reduce by 2166 KVA, any of the following may be removed from service to total 2166 KVA.
13 Cond. Pump -
4000 KVA 12 Heater Drain Pump -
1000 13 Heater Drain Pump -
1000 llB Circ. Water Pump -
2000 12B Circ. Water Pump -
2000 13B Circ. Water Pump -
2000 UNIT NO. 2 22 Station Power Transformer must reduce by 2166 KVA, any KVA KVA KVA KVA KVA of the following may be *removed from service to total 2166 KVA.
23 Cond. Pump -
4000 KVA 22 Heater Drain Pump -
1000 KVA 23 Heater Drain Pump. -
1000 KVA 21B Circ. Water Pump -
2000 KVA 22B Circ. Water Pump -
2000 KVA 23B Circ. Water Pump -
- 2000 KVA