ML18012A531

Proposed Tech Specs 3/4.7.1, Turbine Cycle Safety Valves.

ML18012A531
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Site:	Harris
Issue date:	02/18/1997
From:	CAROLINA POWER & LIGHT CO.
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ML18012A530	List: ML18012A529 ML18012A531
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NUDOCS 9703040169
Download: ML18012A531 (18)

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ENCLOSURE 1 SHEARON HARRIS NUCLEAR POWER PLANT NRC DOCKET NO. 50-400/LICENSE NO. NPF-63 REQUEST FOR LICENSE AMENDMENT OPERATION AT REDUCED POWER LEVELS WITH INOPERABLE MSSVs TECHNICALSPECIFICATION 3/4.7.1, TURBINE CYCLE SAFETY VALVES BASIS FOR CHANGE RE UEST

~Back round Technical Specification (TS) Table 3.7-1 allows operation with inoperable Main Steam Safety Valves (MSSVs) provided that both thermal power and secondary coolant steam flow are reduced and the reactor trip setpoint for power range high neutron flux is reduced. The required reactor trip setpoint reduction is determined by an equation in the TS bases.

Westinghouse Nuclear Safety Advisory Letter NSAL-94-001, "Operation at Reduced Power Levels with Inoperable MSSVs," dated January 20, 1994 identified a deficiency in the basis for Standard Technical Specification Table 3.7.1.1. The deficiency is in the assumption that the maximum allowable initial power level is a linear function of the available MSSV relief capacity.

Westinghouse has determined that this assumption is not correct, and that when operating at low power in accordance with Technical Specification Table 3.7.1 with one or more safety valves inoperable, a loss-of-load/turbine trip transient concurrent with a loss of feedwater could result in overpressurization of the main steam system.

Should a plant operating at high power experience such an initiating event, the transient would be terminated early by a reactor trip due to either high pressurizer pressure or overtemperature delta temperature. The reactor trip terminates the transient and secondary side overpressure protection is provided by the actuation of the main steam safety valves.

When a plant is operating at a reduced power level, a reactor trip may not be initiated early in the transient. An overtemperature delta temperature trip is not generated since the core thermal margins are increased at lower power levels. A high pressurizer pressure trip is not generated if the primary pressure control systems function as designed. As a result, primary heat would continue to be transferred to the secondary side for a longer time period. The reactor would eventually trip on low steam generator water level. However, ifthis event occurs while the unit is operating in accordance with TS Table 3.7.1 with one or more inoperable safety valves, the trip may not occur before secondary pressure exceeds 110 percent of the design pressure.

Westinghouse NSAL 94-001 recommends the use of a more conservative equation to calculate the power range high neutron flux trip setpoint required when one or more MSSVs are inoperable. It is noted in NSAL 94-001 that use of the recommended equation will resolve the aforementioned issue by enabling recalculation of TS 3.7.1.1 setpoints without further modifications to the TS structure.

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NRC Information Notice 94-60, Potential Overpressurization Of Main Steam System, dated A'ugust 22, 1994, requested licensees to review the information provided by NSAL 94-001 for applicability and consider actions, as appropriate, to avoid such problems.

Carolina Power & Light Company approved a TS Interpretation on June 22, 1994 to provide more conservative power range neutron flux high setpoints to be used in place of the setpoints currently specified in TS Table 3.7-1 for operation with one or more inoperable MSSVs.

Pro osed Chan e The purpose of this TS change is to revise the reactor trip settings for power range high neutron flux specified in TS Table 3.7-1. The following more conservative power range neutron flux high setpoints will replace the setpoints currently specified in TS Table 3.7-1 MAXIMUMALLOWABLEPOWER RANGE NEUTRON FLUX HIGH SETPOINT WITH INOPERABLE STEAM LINE SAFETY VALVES DURING 3 LOOP OPERATION MAXIMUMNUMBER OF INOPERABLE MAXIMUMALLOWABLEPOWER RANGE SAFETY VALVES ON ANY NEUTRON FLUX HIGH SETPOINT OPERATING STEAM GENERATOR (PERCENT OF RATED THERMALPOWER) 53 35 17 In addition, the proposed amendment revises the associated Bases to reflect the use of a more conservative equation to calculate the power range high neutron flux trip setpoints in TS Table 3.7-1. This change is being implemented in response to recommendations presented in Westinghouse Nuclear Safety Advisory Letter NSAL-94-001, "Operation at Reduced Power Levels with Inoperable MSSVs," dated January 20, 1994.

Basis The loss of load/turbine trip (LOL/TT) event is analyzed in the FSAR to show that core protection margins (DNBR) are maintained and that the Reactor Coolant and Main Steam Systems will not be overpressurized. The analysis assumes an immediate loss of steam relieving capability through the turbine and loss of all main feedwater. The transient that occurs is terminated by a reactor trip on high pressurizer pressure, overtemperature delta temperature, or low steam generator water level. No credit is taken for a direct reactor trip on turbine trip.

Secondary side overpressure protection is provided by the actuation of the MSSVs, which are designed to relieve at least full power nominal steam flow. The analysis verifies that there is sufficient MSSV capacity to prevent secondary side pressure from exceeding 110% of the design pressure.

The LOL/TT transient is analyzed for a full power initial condition for different cases examining the effects of assuming primary side pressure control and different reactivity feedback conditions.

Overpressure protection can be demonstrated for any initial power level with fully operational MSSVs. TS 3.7.1.1, however, allows operation with a reduced number of operable MSSVs at a Page E1-2

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re'duced power level as determined by resetting the power range high neutron flux setpoint. This TS LCO is not based on a detailed analysis, but rather, on the assumption that the maximum allowable pre-transient power level to ensure overpressure protection during a transient is a linear function of MSSV relief capacity. It has been determined that this assumption is not valid.

The problem is that ifmain feedwater is lost, a reactor trip is necessary to prevent secondary side overpressurization for all postulated core conditions. At high initial power levels, a reactor trip is actuated early in the transient as a result of either high pressurizer pressure or overtemperature delta temperature. The reactor trip terminates the transient and the MSSVs maintain steam pressure below 110% of the design value.

At lower initial power levels, a reactor trip may not be actuated early in the transient. An overtemperature delta temperature trip is not generated since the core thermal margins are increased at lower power levels. A high pressurizer pressure trip is not generated ifthe 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% of the design value if one or more MSSVs are inoperable and reactor power is maintained at levels allowed by the current TS.

To prevent overpressurization, the maximum power level allowed for operation with inoperable MSSVs must be below the heat removing capability of the operable MSSVs. This condition can be met by using a more conservative approach and setting the power range high neutron flux setpoint to this power level, thereby ensuring that the actual power level cannot exceed this value.

The following algorithm was derived by Westinghouse to define these more conservative setpoint values.

Hip = (100/Q) ~w,h, N K

where:

Hip = Safety Analysis power range high neutron flux setpoint, percent Q = Nominal NSSS power rating of the plant (including reactor coolant pump heat), Mwt K = Conversion factor, 947.82 +tu/~sec Mwt 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 lb/sec.

h<< = Heat of vaporization for steam at the highest MSSV opening pressure including tolerance and accumulation, as appropriate, Btu/ibm Page El-3

N = Number of loops in plant The values from this algorithm must then be adjusted lower to account for instrument and channel uncertainties. This adjustment will be 9% power. This will ensure the maximum plant operating power level would then be lower than the reactor protection system setpoint by an appropriate operating margin.

Conclusions The proposed change to Technical Specification 3.7.1.1 and associated bases will address the issue identified by Westinghouse Nuclear Safety Advisory Letter NSAL-94-001, "Operation at Reduced Power Levels with Inoperable MSSVs," dated January 20, 1994. Use of the more conservative equation to calculate the power range high neutron flux trip setpoint ensures overpressure protection of the main steam system by relief provided by the operable main steam safety valves. The re-calculated reactor trip setpoints are lower than those currently allowed by the Technical Specification. For the proposed TS change, the Bases will remain consistent with the plant safety analysis criterion for preventing overpressurization of the secondary side such that the pressure does not exceed 110% of the design pressure for anticipated transients.

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ENCLOSURE2 SHEARON HARRIS NUCLEAR POWER PLANT NRC DOCKET NO. 50-400/LICENSE NO. NPF-63 REQUEST FOR LICENSE AMENDMENT OPERATION AT REDUCED POWER LEVELS WITH INOPERABLE MSSVs TECHNICALSPECIFICATION 3/4.7.1, TURBINE CYCLE SAFETY VALVES 10 CFR 50.92 EVALUATION The Commission has provided standards in 10 CFR 50.92(c) for determining whether a significant hazards consideration exists. A proposed amendment to an operating license for a facility involves no significant hazards consideration ifoperation of the facility in accordance with the proposed amendment would not: (1) involve a significant increase in the probability or consequences of an accident previously evaluated, (2) create the possibility of a new or different kind of accident from any accident previously evaluated, or (3) involve a significant reduction in a margin of safety. Carolina Power & Light Company has reviewed this proposed license amendment request and determined that its adoption would not involve a significant hazards determination. The bases for this determination are as follows:

Pro osed Chan e This Technical Specification change revises the PLANT SYSTEMS TURBINE CYCLE Specification 3/4.7.1 by revising the power range high neutron flux setpoint values in Table 3.7-

1. Specifically, the power range high neutron flux setpoint values are revised as shown below:

MAXIMUMALLOWABLEPOWER RANGE NEUTRON FLUX HIGH SETPOINT WITH INOPERABLE STEAM LINE SAFETY VALVES DURING 3 LOOP OPERATION MAXIMUMNUMBER OF INOPERABLE MAXIMUMALLOWABLEPOWER RANGE SAFETY VALVES ON ANY NEUTRON FLUX HIGH SETPOINT OPERATING STEAM GENERATOR (PERCENT OF RATED THERMALPOWER) 53 35 17 In addition, the proposed amendment revises the BASES 3/4.7.1, TURBINE CYCLE SAFETY VALVES, to reflect the use of a more conservative methodology for use in setting the power range high neutron flux setpoint for operation with inoperable MSSVs. The following algorithm defines these more conservative setpoint values:

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Hi0 = (100/Q) ~tv,h, N K

where:

Hip = Safety Analysis power range high neutron flux setpoint, percent Q = Nominal NSSS power rating of the plant (including reactor coolant pump heat), Mwt K = Conversion factor, 947.82 ~Btu/sec Mwt 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 lb/sec.

h<< = Heat of vaporization for steam at the highest MSSV opening pressure including tolerance and accumulation, as appropriate, Btu/ibm N = Number of loops in plant The values from this algorithm must then be adjusted lower to account for instrument and channel uncertainties. This adjustment will be 9% power.

Basis This change does not involve a significant hazards consideration for the following reasons:

The proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated.

The high flux setpoints are being revised to provide additional margin against secondary side overpressurization for LOL/TT events. The proposed revision will not create any loss or reduction in redundancy or diversity in the reactor protection systems that would increase the probability of a previously evaluated accident. The high flux setpoints are being revised to ensure that the consequences of a previously evaluated accident do not increase.

Therefore, there would be no increase in the probability or consequences of an accident previously evaluated.

The proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated.

No new or previously unanticipated failure mechanisms are introduced by the proposed change. No new failure modes have been created by the proposed change. No new Page E2-2

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credible event or initiating factor is introduced. Reactor power is limited to ensure that the secondary system is not overpressurized.

Therefore, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.

3. The proposed amendment does not involve a significant reduction in the margin of safety.

The margin of safety as defined in the basis of the Technical Specification does not decrease. This change is proposed to ensure that the secondary system pressure will be limited to within 110% of its design pressure during the most severe anticipated operational transient. The revised high flux setpoints are intended to bound the allowable operating configurations of TS Table 3.7-1.

Therefore, the proposed change does not involve a significant reduction in the margin of safety.

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ENCLOSURE 3 SHEARON HARRIS NUCLEAR POWER PLANT NRC DOCKET NO. 50-400/LICENSE NO. NPF-63 REQUEST FOR LICENSE AMENDMENT OPERATION AT REDUCED POWER LEVELS WITH INOPERABLE MSSVs TECHNICALSPECIFICATION 3/4.7.1, TURBINE CYCLE SAFETY VALVES ENVIRONMENTALCONSIDERATIONS 10 CFR 51.22(c)(9) provides criterion for and identification of licensing and regulatory actions eligible for categorical exclusion from performing an environmental assessment. A proposed amendment to an operating license for a facility requires no environmental assessment if operation of the facility in accordance with the proposed amendment would not: (1) involve a significant hazards consideration; (2) result in a significant change in the types or significant increase in the amounts of any effluents that may be released offsite; (3) result in a significant increase in individual or cumulative occupational radiation exposure. Carolina Power & Light Company has reviewed this request and determined that the proposed amendment meets the eligibilitycriteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment needs to be prepared in connection with the issuance of the amendment. The basis for this determination follows:

Pro osed Chan e This Technical Specification change revises the PLANT SYSTEMS Specification 3/4.7.1, TURBINE CYCLE SAFETY VALVES, by revising the maximum allowable power range high neutron flux setpoints (percent of rated thermal power) in TS Table 3.7-1.

Basis The change meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9) for the following reasons:

1. As demonstrated in Enclosure 2, the proposed amendment does not involve a significant hazards consideration.

2. The proposed amendment does not result in a significant change in the types or increase in the amounts of any effluents that may be released offsite.

The proposed change does not involve any new equipment or require existing systems to perform a different type of function than they are currently designed to perform. The change does not introduce any new effluents or increase the quantities of existing effluents. As such, the change cannot affect the types or amounts of any effluents that may be released offsite.

The proposed amendment does not result in a significant increase in individual or cumulative occupational radiation exposure.

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The proposed change does not result in any physical plant changes or new surveillances which would require additional personnel entry into radiation controlled areas.

Therefore, the amendment has no affect on either individual or cumulative occupational radiation exposure.

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ENCLOSURE4 SHEARON HARRIS NUCLEAR POWER PLANT NRC DOCKET NO. 50-400/LICENSE NO. NPF-63 REQUEST FOR LICENSE AMENDMENT OPERATION AT REDUCED POWER LEVELS WITH INOPERABLE MSSVs TECHNICALSPECIFICATION 3/4.7.1, TURBINE CYCLE SAFETY VALVES PAGE CHANGE INSTRUCTIONS Removed Pa e Inserted Pa e 3/4 7-2 3/4 7-2 B 3/4 7-1 B 3/4 7-1, B 3/4 7-la Page E4-1

ENCLOSURE5 SHEARON HARRIS NUCLEAR POWER PLANT NRC DOCKET NO. 50-400/LICENSE NO. NPF-63 REQUEST FOR LICENSE AMENDMENT OPERATION AT REDUCED POWER LEVELS WITH INOPERABLE MSSVs TECHNICALSPECIFICATION 3/4.7.1, TURBINE CYCLE SAFETY VALVES TECHNICALSPECIFICATION PAGES Page E5-1

TABLE 3.7-1 I MAXIMUM ALLOWABLE POWER RANGE NEUTRON FLUX HIGH SETPOINT WITH INOPERABLE STEAM LINE SAFETY VALVES DURING 3 LOOP OPERATION MAXIMUM NUMBER OF INOPERABLE MAXIMUM ALLOWABLE POWER RANGE SAFETY VALVES ON ANY NEUTRON FLUX HIGH SETPOINT OPERATING STEAM GENERATOR PERCENT OF RATED THERMAL POWER SHEARON HARRIS - UNIT 1 3/4 7-2

3/4.7 PLANT SYSTEM

.BASES 3/4.7. 1 TURBINE CYCLE 3/4.7.1.1 SAFETY VALVES The OPERABILITY of the main steam line Code safety valves ensures that the Secondary System pressure will be limited to within 110K (1305 psig) of its design pressure of 1185 psig during the most severe anticipated system opera-tional transient. The maximum relieving capacity is associated with a Turbine trip from 100K RATED THERMAL POWER coincident with an assumed loss of condenser heat sink (i.e., no steam bypass to the condenser).

The specified valve lift settings and relieving capacities are in accordance with the requirements of Section III of the ASME Boiler and Pressure Code, 1971 Edition. The total relieving capacity for all valves on all of the steam lines is 1.36 x 10'bs/h which is 111K of the total secondary steam flow of 12.2 x 10'bs/h at 100K RATED THERMAL POWER. A minimum of two OPERABLE safety valves per steam generator ensures that sufficient relieving capacity is available for the allowable THERMAL POWER restriction in Table 3.7-1.

STARTUP and/or POWER OPERATION is allowable with safety valves inoperable within the limitations of the ACTION requi rements on the basis of the reduction in Secondary Coolant System steam flow and THERMAL POWER required by the reduced Reactor trip settings of the Power Range Neutron Flux channels.

The Reactor Trip Setpoint reductions are derived on the following base :

For 3 loop operation ~ll' M ~ 4Lp)cL SP x (109)

X Where:

SP = Reduced Reactor Trip Setpoint in percent of RATED THERMAL POWER, V = Maximum number of inoperable safety valves per steam line.

109 = Power Range Neutron Flux-High Trip Setpoint for 3 loop operation,

= Total relieving capacity of all safety valves line in X per steam lbs/hour, and Y = Maximum relieving capacity of any one safety valve in lbs/hour 3/4.7. 1.2 AUXILIARY FEEDWATER SYSTEM The OPERABILITY of the Auxiliary Feedwater System ensures that the Reactor Coolant System can be cooled down to less than 350'F from normal operating conditions so that the Residual Heat Removal System may be placed into SHEARON HARRIS - UNIT 1 B 3/4 7-1 Amendment No. 42

INSERT A Hi0 = (100/Q) ~tv,h, N K

where:

Hi/ = Safety Analysis power range high neutron flux setpoint, percent Q = Nominal NSSS power rating of the plant (including reactor coolant pump heat), Mwt K = Conversion factor, 947.82 ~Btn/sec Mwt 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/sec.

h<< = Heat of vaporization for steam at the highest MSSV opening pressure including tolerance and accumulation, as appropriate, Btu/ibm N = Number of loops in plant The values from this algorithm must then be adjusted lower to account for instrument and channel uncertainties. This adjustment will be 9% power.

TABLE 3.7-1 MAXIMUM ALLOWABLE POWER RANGE NEUTRON FLUX HIGH SETPOINT WITH INOPERABLE STEAM LINE SAFETY VALVES DURING 3 LOOP OPERATION MAXIMUM NUMBER OF INOPERABLE MAXIMUM ALLOWABLE POWER RANGE SAFETY VALVES ON ANY NEUTRON FLUX HIGH SETPOINT OPERATING STEAM GENERATOR PERCENT OF RATED THERMAL POWER 53 35 17 SHEARON HARRIS - UNIT 1 3/4 7-2 Amendment No.

3/4.7 PLANT SYSTEMS BASES 3/4.7. 1 TURBINE CYCLE 3/4.7.1.1 SAFETY VALVES The OPERABILITY of the main steam line Code safety valves ensures that the Secondary System pressure will be limited to within 110K (1305 psig) of its design pressure of 1185 psig during the most severe anticipated system opera-tional transient. The maximum relieving capacity is associated with a Turbine trip from 100K RATED THERMAL POWER coincident with an assumed loss of condenser heat sink (i.e.. no steam bypass to the condenser).

The specified valve lift settings and relieving capacities are in accordance with the requirements of Section III of the ASME Boiler and Pressure Code.

1971 Edition. The total relieving capacity for all valves on all of the steam lines is 1.36 x 10'bs/h which is 111K of the total secondary steam flow of 12.2 x 10'bs/h at 100% RATED THERMAL POWER. A minimum of two OPERABLE safety valves per steam generator ensures that sufficient relieving capacity is available for the allowable THERMAL POWER restriction in Table 3.7-1.

STARTUP and/or POWER OPERATION is allowable with safety valves inoperable within the limitations of the ACTION requirements on the basis of the reduction in Secondary Coolant System steam flow and THERMAL POWER required by the reduced Reactor trip settings of the Power Range Neutron Flux channels.

The Reactor Trip Setpoint reductions are derived on the following bases:

For 3 loop operation Hie = (100/Q)

K Where:

Hie = Safety Analysis power range high neutron flux setpoint, percent Q

= Nominal NSSS power rating of the plant (including reactor coolant pump heat), Mwt K = Conversion factor, 947,82 ~Btu/sec Mwt 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 lb/sec.

Heat of vaporization for steam at the highest MSSV opening pressure including tolerance and accumulation. as appropriate, Btu/ibm N = Number of loops in plant The values from this algorithm must then be adjusted lower to account for instrument and channel uncertainties. This adjustment will be 9X power.

SHEARON HARRIS - UNIT 1 B 3/4 7-1 Amendment No.

3/4.7 PLANT SYSTEMS BASES 3/4.7. 1. 2 AUXILIARY FEEOMATER SYSTEM The OPERABILITY of the Auxiliary Feedwater System ensures that the Reactor Coolant System can be cooled down to less than 350'F from normal operating conditions so that the Residual Heat Removal System may be placed into SHEARON HARRIS - UNIT 1 8 3/4 7-la Amendment No.