ML20234F571
| ML20234F571 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 12/24/1987 |
| From: | Firlit J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Miraglia F Office of Nuclear Reactor Regulation |
| References | |
| AGM-NPP-87-478, IEB-79-27, TAC-64359, NUDOCS 8801110529 | |
| Download: ML20234F571 (7) | |
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SACRAMENTO MUNIC' PAL UTILITY DISTRICT D P. O. Box 15830. Sacramento CA 95852-1830,(916) 452-3211 AN ELECTRIC SYSTEM SERVING.THE HEART OF CALIFORNIA AGM/NPP 87-478 DEC 1 m; U.S. Nuclear Regulatory Commission
. Attn: Frank J. Miraglia, Jr.
Associate Director for Projects Phillips Building 7920 Norfolk Avenue Bethesda, MD 20014 Docket No. 50-312 Rancho Seco Nuclear Generating Station License No. DPR-54 IEB 79-27 INSPECTION, FOLLOW-UP QUESTION RESPONSES
Dear Mr. Miraglia:
On December 15,1987,' the NRC, Mr. Rick Kendall, was at the Rancho Seco site for an inspection of the Districts IEB 79-27 response. The results of the inspection indicated that the staff was satisfied with the Districts IEB 79-27 re-review effort. During the meeting, several i
l questions were asked by the staff and the District responses were requested by the staff to be formally submitted. The attachments to this letter provides the question and District response as presented in the December 15, 1987 meeting.
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Please contact me if you have any questions. Members of your staff with questions requiring additional information or clarification may contact j
Mr. John Atwell at (209) 333-2935, extension 4917.
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Sincerely,
[
jo h F. Fir 11t Assistant General Manager, i
Huclear Power Production 1
Attachment cc:
G. Kalman, NRC, Bethesda A. D'Angelo, NRC, Rancho Seco J. B. Martin, NRC, Walnut' Creek
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G RANCHO SECO NUCLEAR GENERATING STATION O 1444o Twin Cities Road, Herald, CA 95638-9799;(209) 333 2935
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ATTACHMENT
- l. kRC State whether the effects of loss of power to all loads (not just Question the loads used for plant shutdown following a reactor trip via procedures E.01, E.02, and B4) affected by a loss of bus power, including loss of power to loads due to cascading power losses, were considered simultaneously to determine the overall effect on the plant when at full power operation.
Also, state for all bus power losses (when considering the combined effects of loss of power to each bus on plant operation) whether a plant shutdown (to cold shutdown) can be achieved through procedures E.01, E.02, and B.4 without having to rely on any additional procedures to mitigate the effects of the power loss.
If procedures other than E.01, E.02, ant' '3.4 are used, state whether the other procedures were reviewed to determine the impact of the ous power loss on performing the procedures.
Please discuss the IE Bulletin 70-27 review methodology with respect to the above.
Response
IE Bulletin 79-27 re-review considered the failure of all loads connected to the bus including the loads not required for safe shutdown and iower level buses (except the buses which are fed from multiple sources via ABT, static switches, etc.) fed from th:s bus.
The study also considered the cumulative loss (cascading effect) of equipment from each single bus failure.
The plant shutdown capability was evaluated for each bus failure l
by a procedure walk through in accordance with E 01 and E.02, i
followed by the appropriate sections of B.4 depending on equipment availability.
Basically., procedures E 01 and E.02 are used to stabilize the plant conditions post trip and procedure B.4 to achieve cold shutdown.
Casualty procedures for the loss of power supply buses have been written to provide the operators with the necessary response and recovery actions to mitigate the consequences of loss of each bus.
This study starts at the plant trip as stated in the report.
When at power operation, if a loss of a bus occurs, the respective casualty procedure for a lost bus directs the operator to take necessary action to stabilize the plant using the equipment and/or instruments available.
If plant parameters reach a point requiring a manual reactor trip, the operator trips the plant manually and immediately goes to E.01 and E.02.
Hence, this study did not start at power operation because loss of bus casualty procedures considered the loss of a bus at any power level and also addresses impact, if any, on the safety of plant and directs the operator on how to deal with the situation.
The results of the report indicate that plant cold shutdown can be achieved after the plant trip through procedures E.01, E.02, and B.4 without having to rely on other plant procedures, other than the respective loss of bus casualty procedure or other referenced casualty procedures.
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ATTACHMENT 1
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- 2. NRC Indicate whether plant casualty procedures were included in the Question IE Bulletin 79-27 review.
Discuss the extent of the review and the methodology for reviewing casualty procedures.
Response
The IE Bulletin 79-27 re-review evaluated the adequacy of Rancho Seco normal operating procedures for achieving cold shutdown for each loss of bus scenario.
Plant casualty procedures for power supply buses were also reviewed and revised as required to provide the operators with the necessary response and recovery actions to mitigate the consequences of loss of power supply buses.
i ATTACHMENT
- 3. NRC Clearly describe the IE Bulletin 79-27 review methodology I
Question applied to buses fed from multiple sources via automatic bus transfer (AT&T) devices, static switches, etc.
If a bus fed from multiple sources is assumed to remain operable upon failure of its higher level (upstream), normal supply bus (due to proper operation of an ABT, static switch or similar device), describe the periodic surveillance / maintenance program applicable to the device to ensure its operability.
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Response
In case of buses fed from multiple sources via automatic bus transfer devices, static switches, etc., the IE Bulletin 79-27 re-review considered the loss of bus and the equipment connected to this bus.
However, in case of loss of higher level buses, downstream lower level buses fed from multiple sources were assumed to be available.
In such cases, it was assumed that transfer switches and the alternate supply sources will not be lost simultaneously with the loss of a normal power supply bus.
Casualty procedures require the operator to check that lower level buses are available, if not directions via the casualty procedure are provided to give the operator proper response.
Rancho Seco plant administrative / operating procedures ensures availability /- operability of bus transfer devices.
Operation of manual by-pass switches and the manual operation of static transfer switches are controlled by procedure. Preventive maintenance on inverters and transfer switches is done normally during every refueling outage or major modification outage per EM 171B and C procedures.
Preventive maintenance on ABT's in the ICS/NNI cabinets is done once every year per EM 144 procedures.
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ATTACHMENT
- 4. NRC State whether the plant bus and load configuration reviewed for Question IE Bulletin 79-27 is the plant configuration that will exist for restart, and indicate whether future plant modifications will be considered with respect to impact on the IE Bulletin 79-27 analysis.
Response
IE Bulletin J9-27 re-review considered the plant configuration as of restart. Therefore, all DCN's still outstanding (as of August 1987) against the power supply buses were reviewed for this study.
Since then, there have been no changes in the plant configuration affecting IE Bulletin 79-27 analysis.
Any future plant modification will be considered in the future with respect to impact on the IE Bulletin 79-27 analysis.
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ATTACMENT J
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S. NRC Discuss the impact of loss of the auxiliary boilers on the Question capability to achieve safe shutdown following bus power losses.
Response
The loss of aux. boilers do not affect the ability to achieve safe shutdown or cooldown. The main steam system can be used, except at very low RCS temperatures, to provide steam for
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necessary loads such as gland steam and air ejectors, thus the loss of auxiliary boilers has no affect on the ability to achieve hot shutdown or cooldown to cold shutdown.
The casualty procedures, including applicable loss of bus procedure and loss of auxiliary boiler procedure, provide direction to the operator to isolate steam loads to prevent excessive cooldown as a result of aux. bolier unavailability.
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ATTACHMENT i
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- 6. NRC Certain procedures refer to use of IDADS displays by the i
Question operators following ICS/NNI power losses.
However, some inprits to the IDADS are provided by ICS/NNI. Discuss the precautions taken to ensure that operators will not be misled by false / invalid indications provided by the IDADS following ICS/NNI power losses.
Response
Emergency operating procedures and the loss of ICS and NNI casualty procedures provide the operator with plant indications that are not affected by the loss, identifies indications that are af fected and provides alternate indications (which also include indication in IDADS) for the operator.
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