ML20214U047

Forwards Addl Info Re 860122 Proposed Amend 140 to License DPR-54,increasing Reactor Trip Setpoint on High Pressure to 2,355 Psig & Threshold for Anticipatory Reactor Trip to 45% of Full Power,Per NRC 860707 Request

ML20214U047
Person / Time
Site:	Rancho Seco
Issue date:	09/19/1986
From:	Julie Ward SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Stolz J Office of Nuclear Reactor Regulation
References
JEW-86-360, TAC-61473, NUDOCS 8609300486
Download: ML20214U047 (6)

Text

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SACRAMENTO MUNICIPAL UTILITY DISTRICT O 62o1 S Street, P.O. Box 15830 Sacramento CA 958521830,(916) 452-3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CAltFORNIA JEW 86-360 September 19, 1986 DIRECTOR OF NUCLEAR REACTOR REGULATIONS ATTN J F STOLZ DIRECTOR PWR PROJECT DIRECTORATE #6 DIVISION OF PWR LICENSING-B U S NUCLEAR REGULATORY COMMISSION WASHINGTON'DC 20555 DOCKET NO. 50-312 LICENSE NO. DPR-54 PROPOSED AMENDMENT N0. 140, REPLY TO INQUIRIES This letter is in response to your request for additional information dated July 7, 1986 with respect to Proposed Amendment No. 140. This proposed amendment, submitted January 22, 1986, requests NRC approval to increase the reactor trip setpoint on high pressure from 2300 psig to 2355 psig, and to raise the arming threshold for anticipatory reactor trip (ART) on turbine trip from 20% of full power to 45%.

The information requested by the NRC and the District's response are presented on the attached.

Should you require any further information with respect to Proposed Amendment No. 140, please contact Mr. Ron W. Colombo at Rancho Seco Nuclear Generating Station Unit No. 1.

. SIARD DEPUTY GENERAL MANAGER NUCLEAR Attachments cc: Region V (2) Subscribed and sworn to before me MIPC (2) this J (/'" day of ' v t !/; t,z / H, 1986.

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ATTACHMENT Presented below, in the order. submitted, are the District's responses to NRC's request of July 7, 1986 for additional information with respect to Proposed Amendment No. 140:

REQUEST Considering Rancho Seco's bypass capabilities, atmospheric dump valve capacity and other plant specific ~ features, will the higher setpoint for reactor trip on high pressure in combination with the increased Anticipatory Reactor Trip on Turbine Trip (ART) threshold result in more frequent challenges to the Main Steam Safety Valves (MSSVs)? Also, compare the frequency of MSSV challenges for the proposed Technical Specification changes with the frequency of MSSV challenges for the initial plant design (i.e., 2355 psig and no ART). Provide the bases for SMUD's response. If the proposed changes to the Technical Specifications will result in more frequent challenges to the MSSVs, then describe why the proposed changes are acceptable in regards to a stuck open MSSV.

RESPONSE

The combination of increasing the ARTS threshold and increasing the high pressure trip setpoint will not increase the frequency of MSSV challenges. These changes may in fact reduce the number of MSSV challenges.

The transient data assembled from the Transient Assessment Program shows that all reactor trips from power levels greater than 10-15% result in the MSSVs opening.* Therefore, any power runback that occurs (in lieu of a reactor trip) and does not open the MSSVs will r2 duce the number of challenges to these valves. Even if every runback results in the MSSVs opening, the total number of challenges will not increase. The number of types of past reactor trip situotions that would now result in runbacks are discussed in BAW 77-1159095-00

" Justification For Raising Setpoint For Reactor Trip on High Pressure" and 77-1159289-00 " Basis For Raising Arming Threshold For Anticipatory Reactor Trip on Turbine Trip".

• Even at power levels less than the total steam by-pass capacity of a plant, a reactor trip will open some MSSVs. This is due to the slow opening time associated with the condenser by-pass and atmospheric vent valves.

REQUEST Demonstrate that the accident analyses in the FSAR are consistent with the higher setpoint for reactor trip on high pressure in combination with the increased ART threshold. In particular, are the accident analyses in Ch. 14 of the FSAR based on the high pressure trip setpoint of 2300 psig or 2355 psig? Are the accident analyses in Ch. 14 based on the use of ART? At least the following accidents should be specifically considered: (1) the control rod ejection accident; (2) the start-up accident; (3) the rod withdrawal accident at rated power operation; (4) the moderator dilution accident; and (5) loss of electric power. Revise the preceding accident analyses in the FSAR, as well as Ch. 4 and 7 (e.g., see Table 4.2-8, p. 4.2-43, and pp. 7.1-9, 17), as necessary.

ATTACHMENT RESPONSE The accident analyses in Chapter 14 of the Rancho Seco FSAR were performed with a high' pressure reactor trip setpoint of 2415 psig. The 2415 psig setpoint is the sum of: 2355 psig nominal setpoint at the instrument tap; a given 30 psi instrument error; and a conservative margin of 30 psi head loss-from the pressurizer to the tap location in the primary piping. No credit was taken for ART system functions in any of the FSAR Chapter 14 analyses.

With respect to specific events, (1) the control rod ejection accident; (2) the start-up event; (3) the rod withdrawal event at rated power; and (4) the moderator dilution accident were all analyzed using the 2415 psig (2355 psig nominal) reactor trip setpoint. In addition, the primary-to-secondary heat transfer was held constant during these " primary system initiated events" and in most cases a spectrum of reactivity insertion rates was analyzed. Therefore, the ART system has no impact on the results of those analyses (i.e., conservative predictions of peak primary system pressure, minimum DNBR, peak fuel enthalpy, etc).

In regard to loss of electric power, as stated previously, no credit was taken for ART system in FSAR analyses. Therefore, the reactor was allowed to trip on the RPS high pressure trip value of 2415 psig. This provides a conservative prediction of peak primary system pressure for this event.

A revision to Chapter 14 is not necessary since the RPS high pressure setpoint and turbine / reactor trip assumptions for each event are stated in the appropriate sections. FSAR pages 4.2-43, 7.1-9, and 7.1-17 will be revised to reflect the Technical Specification revision.

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SACRAMENTO MUNICIPAL UTIUTY DISTRICT O 6201 S Street. P.o. Box 15830, Sacramento CA 95852-1830,(916) 452-3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA JEW 86-360 September 19, 1986 DIRECTOR OF NUCLEAR REACTOR REGULATIONS ATTN J F STOLZ DIRECTOR PWR PROJECT DIRECTORATE #6 DIVISION OF PWR LICENSING-B U S NUCLEAR REGULATORY COMMISSION WASHINGTON DC 20555 DOCKET NO. 50-312 LICENSE NO. DPR-54 PROPOSED AMENDMENT NO. 140, REPLY TO INQUIRIES This letter is in response to your request for additional information dated July 7, 1986 with respect to Proposed Amendment No. 140. This proposed amendment, submitted January 22, 1986, requests NRC approval to increase the reactor trip setpoint on high pressure from 2300 psig to 2355 psig, and to raise the arming threshold for anticipatory reactor trip (ART) on turbine trip from 20% of full power to 45%.

The information requested by the NRC and the District's response are presented on the attached.

Should you require any further information with respect to Proposed Amendment No. 140, please contact Mr. Ron W. Colombo at Rancho Seco Nuclear Generating Station Unit No. 1.

. WARD-DEPUTY GENERAL MANAGER NUCLEAR ,

. Attachments cc: Region V (2) Subscribed and sworn to before me MIPC (2) this J (/Pday of ~ v i >[ ,.. / . ,, 1986.

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ATTACHMENT Presented beluw, in the order submitted, are the District's responses to NRC's request of July 7, 1986 for additional information with respect to Proposed Amendment No. 140:

REQUEST Considering Rancho Seco's bypass capabilities, atmospheric dump valve capacity and other plant specific features, will the higher setpoint for reactor trip on high pressure in combination with the increased Anticipatory Reactor Trip on Turbine Trip (ART) threshold result in more frequent challenges to the Main Steam Safety Valves (MSSVs)? Also, compare the frequency of MSSV challenges for the proposed Technical Specification changes with the frequency of MSSV challenges for the initial plant design (i.e., 2355 psig and no ART). Provide the bases for SMUD's response. If the proposed changes to the Technical Specifications will result in more frequent challenges to the MSSVs, then describe why the proposed changes are acceptable in regards to a stuck open MSSV.

RESPONSE

The combination of increasing the ARTS threshold and increasing the high pressure trip setpoint will not increase the frequency of MSSV challenges. These changes may in fact reduce the number of MSSV challenges.

The transient data assembled from the Transient Assessment Program shows that all reactor trips from power levels greater than 10-15% result in the MSSVs opening.* Therefore, any power runback that occurs (in lieu of a reactor trip) and does not open the MSSVs will reduce the number of challenges to these valves. Even if every runback results in the MSSVs opening, the total number of challenges will not increase. The number of types of past reactor trip .

situations that would now result in runbacks are discussed in BAW 77-1159095-00

" Justification For Raising Setpoint For Reactor Trip on High Pressure" and 77-1159289-00 " Basis For Raising Arming Threshold For Anticipatory Reactor Trip on Turbine Trip".

• Even at power levels less than the total steam by-pass capacity of a plant, a reactor trip will open some MSSVs. This is due to the slow opening time associated with the condenser by-pass and atmospheric vent valves.

REQUEST Demonstrate that the accident analyses n the FSAR are consistent with the i

higher setpoint for reactor trip on high pressure in combination with the increased ART threshold. In particular, are the accident analyses in Ch. 14 of the FSAR based on the high pressure trip setpoint of 2300 psig or 2355 psig? Are the accident analyses in Ch. 14 based on the use of ART 7 At least the following accidents should be specifically considered: (1) the control rod ejection accident; (2) the start-up accident; (3) the rod withdrawal accident at rated power operation; (4) the moderator dilution accident; and (5) loss of electric power. Revise the preceding accident analyses in the FSAR, as well as Ch. 4 and 7 (e.g., see Table 4.2-8, p. 4.2-43, and pp. 7.1-9, 17), as necessary.

ATTACHMENT RESPONSE The accident analyses in Chapter 14 of the Rancho Seco FSAR were performed with a high pressure reactor trip setpoint of 2415 psig. The 2415 psig setpoint is the sum of: 2355 psig nominal setpoint at the instrument tap; a given 30 psi instrument error; and a conservative margin of 30 psi head loss from the pressurizer to the tap location in the primary piping. No credit was taken for ART system functions in any of the FSAR Chapter 14 analyses.

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With respect to specific events, (1) the control r'od ejection accident; (2) the start-up event; (3) the rod withdrawal event at ' rated power; and (4) the moderator dilution accident were all analyzed using the 2415 psig (2355 psig nominal) reactor trip setpoint. In addition, the primary-to-secondary heat transfer was held constant during these " primary system initiated events" and in most cases a spectrum of reactivity insertion rates was analyzed. Therefore, the ART system has no impact on the results of those analyses (i.e., conservative predictions of peak primary system pressure, minimum DNBR, peak fuel enthalpy, etc).

In regard to loss of electric power, as stated previously, no credit was taken for ART system in FSAR analyses. Therefore, the rea.ctor was allowed to trip on the RPS high pressure trip value of 2415 psig. This provides a conservative prediction of peak primary system pressure for this event.

A revision to Chapter 14 is not necessary since the RPS high pressure setpoint and turbine / reactor trip assumptions for each event are stated in the appropriate sections. FSAR pages 4.2-43, 7.1-9, and 7.1-17 will be revised to reflect the Technical Specification revision.

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