ML20065F863

Application for Amends to Licenses NPF-68 & NPF-81, Revising TS 3/4.7.1.1 & Bases Re Max Allowed Reactor Thermal Power Operation W/Inoperable Main Steam Safety Valves

ML20065F863
Person / Time
Site:	Vogtle
Issue date:	03/31/1994
From:	Mccoy C GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20065F869	List: ML20065F863 ML20065F896
References
LVC-0286, LVC-286, NUDOCS 9404120057
Download: ML20065F863 (8)

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l L Georgia Powei Company

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j Post Office Box 1295 Bam<ngham, Alabama 35201 =

Telephone 205 877 7122 -

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c. K. McCoy Georgia4 Power -

Vice President Nuclear Vogtle Pro \ect lie southem Ekonc system March 31, 1994 Docket Nos. 50-424 LCV-0286 l 50-425 U. S. Nuclear Regulatory Commissicn ATTN: Document Control Desk Washington, D. C. 20555 VOGTLE ELECTRIC GENERATING PLANT . l 1

REQUEST TO REVISE TECHNICAL SPECIFICATIONS -

INOPERABLE MAIN STEAM SAFETY VALVES -

Gentlemen:

In accordance with the provisions of 10 CFR 50.90, Georgia Power Company (GPC) proposes to amend the Vogtle Electric Generating Plant (VEGP) Unit I and Unit 2 Technical Specifications, Appendix A to Operating Licenses NPF-68 and NPF-81; The proposed changes revise Technical Specification 3/4.7.1.1 and its Bases regarding l maximum allowed reactor thermal power operation with inoperable' main steam safety valves (MSSVs). .

By letter dated January 20,1994 , Westinghouse issued Nuclear Safety Advisory Letter (NSAL)94-001 which notified GPC of a deficiency in the basis for VEGP Technical Specification 3/4 7.1.1 which allows the plant to operate at reduced power levels with a specified number of MSSVs inoperable. Westinghouse also provided a copy of this

notification to the Nuclear Regulatory Commission (NRC) since it impacts information contained in NUREG-1431, " Standard Technical Specifications, Westinghouse Plants."

Accordingly, VEGP Technical Specification 3/4.7.1.1 is not based on a detailed analysis, but rather on the assumption that the maximum power level at which the plant is allowed to operate is a linear function of the available MSSV relief capacity. The linear function is identified in the Bases section for VEGP Technical Specification 3/4.7.1.1 and is used to calculate the maximum allowable power range neutron flux high setpoint values shown in Table 3.7-1. Under certain conditions and with typical conservative safety analysis assumptions, a loss ofload/ turbine trip transient from reduced power conditions may .

result in overpressurization of the main steam system when operated in accordanc4 with .

VEGP Technical Specification 3/4.7.1.1. Consequently, the linear function assumption is 9404120057 940331 PDR

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not valid. Instead, an algorithm should be used to calculate the allowed reduced ' power conditions. Based on the evaluation presented in NSAL 94-001, Westinghouse concluded that this deficiency does not represent a substantial safety hazard pursuant to 10 CFR 21.-

The basis for the proposed changes to the VEGP Technical Specifications is provided in Enclosure 1. The supporting significant hazards evaluation pursuant to .10 CFR 50.91 is provided in Enclosure 2. Based upon the analysis provided, GPC has determined that the proposed changes to the VEGP Technical Specifications do not involve a significant hazards consideration as defined by 10 CFR 50.92. The hand-marked pages of the VEGP Technical Specifications are provided in Enclosure 3.

The proposed allowable power range conditions versus inoperable MSSVs are more conservative than the conditions currently allowed by VEGP Technical Specification 3/4.7.1.1. Therefore, GPC has taken the initiative to implement administrative controls at VEGP which restrict plant operation in accordance with the proposed operating conditions until receipt of NRC approval of this license amendment request.

In accordance with 10 CFR 50.91, the designated state official will be sent a copy of this letter and all enclosures..

Mr. C K. McCoy states that he is a vice president of Georgia Power Company and is authorized to execute this oath on behalf of Georgia Power Company and that, to the best of his knowledge and belief, the facts set forth in this letter and enclosures are true.

GEORGIA POWER COMPANY l

l By:

C. K. McCoy /

Sworn to and subscribed before me this 3 ay f of OL , 1994.

Y OllM k . kkI

' Nbtary Public  !

CKM/TMM LCV-0286 700775

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Georgia Po ver b U. S. Nuclear Regulatory Commission Page 3

Enclosures:

l 1. Basis for Proposed Change

2. 10 CFR 50.92 Evaluation

3. Proposed Technical Specification Changes c(w): Geornia Power Company Mr. J. B. Beasley, Jr.

I Mr. M. Sheibani NORMS U. S. Nuclear Reeulatory Commission Mr. S. D. Ebneter, Regional Administrator i Mr. D. S. Hood, Licensing Project Manager, NRR l Mr. B. R. Bonser, Senior Resident Inspecter, Vogtle State of Georgia Mr. J. D. Tanner, Commissioner, Department ofNatural Resources  ;

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LCV-0286 700775

ENCLOSURE 1 l

l VOGTLE ELECTRIC GENERATING PLANT L REQUEST TO REVISE TECHNICAL SPECIFICATIONS l INOPERABLE MAIN STEAM SAFETY VALVES l

BASIS FOR PROPOSED CHANGE Pronosed Change The proposed changes to the Vogtle Electric Generating Plant (VEGP) Unit I and Unit 2 l

Technical Specifications would revise the requirements of Technical Specification

( 3/4.7.1.1 by reducing the maximum allowable power range neutron flux high setpoint -

values (percent of rated thermal power) shown in Table 3.7-1.- Bases Section 3/4.7.1.1 is also being revised to reflect the new methodology used to calculate these setpoints.

Basis for Proposed Change i- The loss ofload/ turbine trip (LOI/rT) event is analyzed in Section 15.2 of the VEGP l Final Safety Analysis Report (FSAR). The FSAR only analyzes the LOL/TT transient l from the full power initial condition, with cases examining the effects of assuming primary-l side pressure control and different reactivity feedback conditions. The analysis

! demonstrates that core protection margins (departure from nucleate boiling ratio) are I l maintained, the reactor coolant system will not overpressurize, and the main steam system ,

l will not overpressurize. The analysis assumes an immediate loss of steam relieving l capability through the turbine and coincident loss of all main feedwater. No credit is taken l for a direct reactor trip on turbine trip, since this trip would not be actuated for the case of -

a loss of steam load. Rather, the transient is terminated by a reactor trip on high pressurizer pressure, overtemperature AT, or low steam generator water level. Secondary side overpressure protection is provided by actuation of the MSSVs, which are designed to relieve at least full power nominal steam flow. The analysis verifies that the MSSV capacity is sufficient to prevent secondary side pressure from exceeding 110 percent of the design pressure. However, VEGP Technical Specification 3/4.7.1.1 allows the plant to operate at reduced power levels with a specified number of MSSVs inoperable. j Consequently, the maximum allowed power level with inoperable MSSVs is dependent on the heat removal capability of the operable MSSVs. Accordingly, the power range high neutron flux setpoint assures that the actual power level does not exceed the heat removal capability of the operable MSSVs.

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ENCLOSURE I (CONTINUED)

VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATIONS INOPERABLE MAIN STEAM SAFETY VALVES J

4 BASIS FOR PROPOSED CHANGE As stated above, the FSAR only_ analyzes the LOIlfT transient from the full power initial condition. Therefore, the setpoints listed in Table 3.7-1 of VEGP Technical Specification 3/4.7.1.1 are not based on a detailed analysis, but rather on the assumption thtt the maximum power level at which the plant is allowed to operate is a linear function of available MSSV relief capacity. This linear function is identified in Bases Section 3/4.7.1.1. However, under certain conditions and with typical conservative safety analysis assumptions, a LOIJTT transient from reduced power conditions may result in overpressurization of the main steam system (> 110 percent). At lower initial power levels, a reactor trip may not be actuated early in the transient. An overtemperature AT

- trip is also not generated since the core thermal margins are increased at lower' power levels. A high pressurizer pressure trip is not generated either if the primary pressure control systems function normally. This results in a longer time during which primary heat is transferred to the secondary side. The reactor eventually trips on low steam generator water level, but this may not occur before steam pressure exceeds 110 percent of the design value if one or more MSSVs are inoperable in accordance with VEGP Technical Specification 3/4.7.1.1. Consequently, the linear function assumption is not valid.

Instead, the following algorithm should be used to calculate the setpoint values:

Hi $ = (100/Q) (W,hgN) -

K where:

Hi $ = Safety Analysis power range high neutron flux setpoint, percent

= Nominal NSSS power rating of the plant (including reactor coolant pump Q

heat), MWt K = Conversion factor,947.82 (Btu /s)

MWt El-2

ENCLOSURE 1 (CONTINUED)

VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATIONS -

INOPERABLE MAIN STEAM SAFETY VALVES BASIS FOR PROPOSED CHANGE w, . Minimum total steam flow rate capability of the operable MSSVs on any one steam generator at the highest MSSV opening pressure including tolerance and accumulation, as appropriate, in Ib/s. For example, if the maximum number ofinoperable MSSVs on any one steam generator is one, then w, should be a summation of the capacity of the operable MSSVs at the highest operable MSSV operating pressure, excluding the highest capacity MSSV. If the maximum number ofinoperable MSSVs per steam generator is three then wg should be a summation of the capacity of the operable MSSVs at the highest operable MSSV operating pressure, excluding the three highest capacity MSSVs.-

hrg

= Heat of vaporization for steam at the highest MSSV opening pressure including tolerance and accumulation, as appropriate, Btu /lbm.

l N = Number ofloops in the plant. l l

Additionally, the calculated values are reduced to account for instrument and channel uncertainties (typically 9 percent power). Therefore, the maximum plant operating power level would be lower than the reactor protection system setpoint by an appropriate l' operating margin. The following table compares the maximum allowable power range neutron flux high setpoint values versus number of MSSVs inoperable with the power range values calculated using the linear function and the algorithm method of analysis:

Number Maximum Power Maximum Power of Range- % Rated Range- % Rated MSSVs Thermal Power Thermal Power Inoperable (Linear Function Basis) (Algorithm Basis) 1 87 71 2 65 51 3 43 31 El-3 l

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ENCLOSURE 1 (CONTINUED)

I VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATIONS INOPERABLE MAIN STEAM SAFETY VALVES BASIS FOR PROPOSED CHANGE 'l Accordingly, Enclosure 3 contains proposed changes to VEGP Technical Specification Table 3.7-1 which incorporate the new power range neutron flux high setpoint values listed above that were derived using the algorithm methodology. These new setpoints will -

provide continued assurance that the secondary side steam pressure will remain below

.110 percent of the design value following a LOL/rT when one or more MSSVs are declared inoperable. Bases Section 3/4.7.1.1 has also been revised to include the -

algorithm setpoint derivation methodology.

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATIONS INOPERABLE MAIN STEAM SAFETY VALVES 10 CFR 50.92 EVALUATION Georgia Power Company has reviewed the requirements of 10 CFR 50.92 as they relate to the proposed changes to the Vogtle Electric Generating Plant (VEGP) Technical Specifications and has made the following determination:

1. The proposed changes do not involve a significant increase in the probability or..

consequences of an accident previously evaluated.' The new power range neutron flux high setpoint values will ensure that the secondary side steam pressure will remain below 110 percent ofits design value following a loss ofload/ turbine trip (LOI/rT) when one or more main steam safety valves (MSSVs) ate declared inoperable.

Therefore, this transient will remain classified as a Condition 11 probability event (faults of moderate frequency) per ANSI -' N18.2,1973 as discussed in Section 15.0.1 of the VEGP Final Safety Analysis Report (FSAR).. Accordingly, since the new power range setpoints will maintain the capability of the MSSVs to perform their pressure relief function associated with a LOI/IT event, there will be no effect on the probability or consequences of an accident previously evaluated.

2. The proposed changes do not create the possibility of a new or different kind of  :

accident from any accident previously evaluated. The proposed changes do not -

involve any change to the configuration or method of operation of any plant equipment,'and no new failure modes have been defined for any plant system or component. The new power range neutron flux high setpoints will maintain the capability of the MSSVs to perform their pressure relief function to ensure the secondary side steam design pressure is not exceeded following a 1,OI/fT.

Therefore, since the function of the MSSVs is unaffected by the proposed changes, the possibility of a new or different kind of accident from any accident previously evaluated is not created.

3. The proposed changes do not involve a significant reduction in a margin of safety.

The algorithm methodology used to calculate the new ~ power range neutron flux high setpoints is conservative and bounding since it is based on a number ofinoperable MSSVs per loop; i.e., if only'one MSSV in one loop is out of service, the applicable power range setpoint would be the same as if one MSSV in each loop were out of E2-1 l

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VOGTLE ELECTRIC GENERATING PLANT I REQUEST TO REVISE TECHNICAL SPECIFICATIONS l INOPERABLE MAIN STEAM SAFETY VALVES i 4 10 CFR 50.92 EVALUATION I i

i service. Another conservatism with the algorithm methodology is viith the assumed -

j minimum total steam flow rate capability of the operable MSSVs. The assumption is a

that ifone or more MSSVs are inoperable per loop, the inoperable MSSVs are the largest capacity MSSVs, regardless of which capacity MSSVs are actually inoperable.

l Therefore, since the power range setpoints calculated for the proposed changes using .

the algorithm methodology are more conservative and ensure the secondary side steam i design pressure is not exceeded following a LOI1rT, there will not be a significant

. reduction in a margin of safety.

Conclusion I . Based on the preceding analysis, Georgia Power Company has determined that the

proposed changes to the VEGP Technical Specifications will not significantly increase the probability or consequences of an accident previously evaluated, create the possibility of a i new or different kind of accident than any previously evaluated, or involve a significant i reduction in a margin of safety.. Therefore, the proposed changes meet the requirements i of 10 CFR 50.92(c) and do not involve a significant hazards consideration.

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