ML20073D128

Proposed Tech Spec 3.5.3.2 Re Operability of Safety Injection Pump in Modes 5 & 6

ML20073D128
Person / Time
Site:	Seabrook
Issue date:	04/24/1991
From:	PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:
Shared Package
ML20073D127	List: ML20073D123 ML20073D128
References
NUDOCS 9104260178
Download: ML20073D128 (20)

Text

. ,

New Hampshire Yankee April 24,1991 ENCLOSURE 1 TO NYN 91067 PROPOSED TECHNICAL SPECIFICATION CH ANGES hhh DO .[

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EMERGENCY CORE COOLING SYSTEMS I

-ECC CUBSYSTEM - T LES: T"A" 35C I l avg ECCS SUBSYSTEMS - T avg EQUAL TO OR LESS THAN 200*F LIMITING CONDITION FOR OPERATION 3.5.3.2 ^11 Rf;ty hj :tter purp: :h5" 5: i noper:ble. 4- DJ5E R T A APPLICABILITY: MODE 5 and MODE 6 with the reactor vessel head on.

ACTION:

W t' : Rfety k p d.ivu ,..::.; ODE 0**LE, rc:t:r: c',' 5:fety hj :ti;r purp: t: c an imerab'; atet.u n i;;.k 4 h:tr:, s fd.se/2r 2 SURVEILLANCE REOUIREMENTS r' "$" * *

• #" P 4.5.3.2- All Safety Injection pumpsAshall be demonstrated inoperable verifying that the motor circuit breakers are secured in the open position at least once per 31 days.

• An inoperable pump may be energized for testing or for filling accumulators provided the discharge at the pump has been isolated from the RCS by a closed

. isolation valve with power renoved from the valve operator, or'by a manual isolation valve secured in the' closed position.

l SEABROOK - UNIT 1 3/4 5-10

Inserts for Technical Specification 3.5.3.2 Insert A:

s a minimum, the following number of Safety Injection pumps shall be inoperable:

a. Two when the RCS vent urea is less than 18 square inches.*

b. One when the RCS vent area is equal to or greater than 18 square inches.

-Insert B:

With fewer than the required number of Safety Injection pumps inoperable, restore all pumps required to be inoperable, to inoperable status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

REACTOR COOLANT SYSTEM

,, PRESSURE / TEMPERATURE LIMITS b-OVERPRESSURE PROTECTION SYSTEMS LIMITING CONDITION FOR OPERATION 3.4.9.3 4.t hc:t MIe following Overpressure Protection Systems shall be OPERABLE:

0. 24 s fe Y A p' l) Two residual heat removal (RHR) suction relief valves each with a setpoint of 450 psig 3%, or

f. 9) Two power-operated relief valves (PORVs) with lif t setpoints that vary with RCS temperature which do not exceed the limit established in Figure 3.4-4, or

0. rect

% 3)The Reactor Coolant System (RCS) depressurized with an RCS vent

greater than or equal to 1,58 square inches.

D. %A S ER *r 8 APPLICABILITY: MODE 4 when the temperature of any RCS cold leg is less than '

or equal to 329'F; MODE 5 ard MODE 6 with the reactor vescel head on.

ACTION:

0.. ~3~9 5 6 2 7 C-p'. l} With one PORV and one RHR suction relief valve inoperable, either A-restore two PORVs or two RHR suction relief valves to OPERABLE

'((i? status within 7 days or depressurito and vent the RCS through at least a 1.58-square-inch vent within -the next 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.

72)WithbothPORVsandbothRHRsuctionrel.ief.valvesinoperable, depressurize ar.d vent the RCS through at least a 1.58 square-inch vent within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, p'.3)In the event the PORVs, or the RHR suction relief valves, or the RCS vent (s) are used to mitigate an RCS pressure transient, a Special Report shall bo prepared and submitted to the Commission pursuant to Specification 6.8.2 within 30 days. The report shall describe the circumstances initiating the transient, the effect of the PORVs, or the RHR suction relief valves, or RCS vent (s) on the transient, and

-any corrective action necessary to prevent recurrence,

b. ~%ASGKT b -

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SEABROOK - UNIT 1 3/4 4-34

Inserts for Technical Specification 3.4.9.3 Insert A:

In MODE 4 when the temperature of any RCS cold leg is less than or equal to 329'F; and in MODE 5 and MODE 6 with all Safety Injection pumps inoperable:

Insert B:

In MODE 5 and MODE 6 with all Safety Injection pumps except one inoperable:

1) The Reactor Coolant System (RCS) depressurized with an RCS vent area equal to or greater than 18 square inches.

Insert C:

In MODE 4, MODE 5 and MODE 6 with all Safety Injection pumps inoperable:

Insert D:

In MODE 5 and HODE 6 with all Safety Injection pumps except one inoperable:

1) With the RCS vent area less than 18 square inches, immediately restore all Safety Injection pumps to inoperable status.

l REACTOR COOLANT SYSTEM

, PRESSURE / TEMPERATURE LIMITS

@ OVERPRESSURE PROTECTION SYSTEMS SURVEILLANCE RE0VIREMENTS 4.4.9.3.1 Each PORV shall be demonstrated OPERABLE by:

a. Performance of an ANALOG CHANNEL OPERATIONAL TEST on the PORV actuation channel, but excluding valve operation, within 31 days

. prior to entering a condition in which the PORV is required OPERABLE and at least once per 31 days thereaf ter when the PORV is required OPERABLE;

a. Performance of a CHANNEL CALIBRATION on the PORV actuation channel at least once-per 18 months; and

c. Verifying the PORV isolation valve is open at least once per 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> when the PORV is being used for overpressure protection.

4.4,9.3.2 Each RHR suction relief valve shall be demonstrated OPERABLE when the RHR suction relief valves are being used for cold overpressure protection as follows:

1. 5 a. For RHR suction relief valve RC-V89

'W

1) By verifying at least once per 31 days that RHR RCS Suction Isolation Valve RC-V88 is open with power to the valve operator removed, and

2) By verifying at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> that RC-V87 is open.

b. For RHR suction relief valve RC-V24

1) By verifying at least once per 31- days that RC-V22 is' open with power to the valve operator removed, and

2) By verifying at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> that RC-V23 is open.

c. Testing pursuant to Specification 4.0.5.

4.4.9.3.3 The RCS vent (s) shall be verified to be open at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />

• when the vent (s) is being used for overpressure protection, gg(s) or- }DVIC AIS\

• Except when the vent pathway is provided with a vehethat is locked, sealed, or otherwise secured in the open position, then verify the:c 19/Qpen'at least once per 31 days.

./A,3 Alge(s)Lorjewel(y l

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SEABROOK - UNIT 1 3/4 4-35

New Hampshire Yankee April 24,1991 ENCLOSURE 2 TO NYN 91067 PROPOSED REVISIONS TO TECHNICAL SPECIFICATION BASES 4

REACTOR COOLMT SYSTEM go,, BASES

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3/4.4.9 PRESSURE / TEMPERATURE LIMITS (Continued)

COLO OVERPRESSURE PROTECTION The Maximum Allowed PORV Setpoint for the Cold Overpressure Mitigation System (COMS) is derived by analysis which models the performance of the COMS assuming various mass input and heat input transients. Operation with a PORV Setpoint less than or equal to the maximum Setpoint ensures that Appendix G criteria will not be violated with consideration for: (1) a maximum pres-sure overshoot beyond the PORV Setpoint which can occur as a result of time de-lays in signal processing and valve opening; (2) a 50 F heat transport effect made possible by the geometrical relationship of the RHR suctien line and the RCS wide range temperature indicator used for COMS; (3) instrument uncertain-ties; and (4) single failure. To ensure mass and heat input transients more severe than those assumed cannot occur, Technical Specifications require lock-out of both Safety injection pumps and all but one centrifugal charging pump while in MODES 4, 5, and 6 with the reactor vessel head installed and disallow st' art of an RCP if secondary coolant temperature is more than 50 F above reac-tor coolant temperature. Exceptions to these requirements are acceptable as described below.

Operation above 350 F but less than 375 F with only centrifugal charging pump OPERABLE and no Safety Injection pumps OPERABLE is allowed for up to

.#. 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. As shown by analysis, LOCAs occurring at low temperature, low pres-JSc'4

' ire conditions can be successfully mitigated by the operation of a single centrifugal chargi'ng pump and a single RHR pump with no credit for accumulator injection. Given the short time duration and the condition of having only one centrifugal charging pump OPERABLE and the probability of a LOCA occurring dur-ing this time, the failure of the single centrifugal charging pump is not assumed.

Operation below 350 F but greater than 325 F with all centrifugal charging and Safety injection pumps OPERABLE is allowed for up to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. During low pressure, low temperature operation all automatic Safety injection actuation signals except Containment Pressure - High are blocked. In normal conditions, a single failure of the ESF actuation circuitry will result in the starting of at most one train of Safety Injection (one centrifugal charging pump, and one Safety Injection pump). For temperatures above 325 F, an overpressure event occurring as a result of starting two pumps can be successfully mitigated by ,

i operation of both PORVs without exceeding Appendix G limit. Ci a th; ; W t4-

,:_ a - >:.- ru,+ su. --at.:~ m~,a ,a s u ,. u ~ u ,u , s a . . TNSERT

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$5[f$!$[UbkV7b$U;dm2b.AiNitiation of b"o[ trains'o[ Safety Injection during this 4-hour time frame due to operator error or a single fail-ure occurring during testing of a redundant-channel are not considered-to be credible accidents.

Operation with all centrifugal charging pumps and both Safety injection pumps OPERABLE is acceptable when RCS temperature is greater than 350 F, a single PORV has suf ficient capacity to relieve the combined flow rate of all SEABROOK - UNIT 1 B 3/4 4-15 1 l

i Insert for BASES Page B 3/4 4-15 A single failure of-a PORV is not assumed due to the short duration that this condition is allowed and the low probability of an event occuring during this interval in conjunction with the failure of a PORV to open.

'..- REACTOR COOLANT SYSTEM i BASES 3/4.4.9 PRESSURE / TEMPERATURE LIMITS (Continued) 4

. COLOOVERPRESSUREPROTECTION(Continued) pumps. Above 350 F two RCPs and all pressure safety valves are required to be OPERABLE. Operation of an RCP eliminates the possibility of a 50*F difference existing between indicated and actual RCS temperature as e result of heat trans-port effects. Considering instrument uncertainties only, an indicated RCS tem-parature of 350 F is sufficiently high to allow full RCS pressurization in ac-cordance with Appendix G limitations. Should an overpressure event occur in these conditions, the pressurizer safety valves provide acceptable and redun-dent overpressure protection.

1 NS EA 7" The Maximum Allowed PORY Setpoint for the Cold Overpressure Mitigation System vill be revised on the basis of the results of examinations of reactor v'essel material irradiation surveillance specimens performed as required by 10 CFR Part 50, Appendix H.

3/4.4.10 STRUCTURAL INTEGRITY The inservice inspection and testing programs for ASME Code Class 1, 2, and 3 ccaponents ensure that the structural integrity and operational readiness of these components will be maintained at en acceptable level throughout the life of-the plant. ihese programs are in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda as required by 10 CFR 50.55a(g) except where s;scific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).

Cocoonents of the Reactor Coolant System were designed to provide access to permit inservice inspections in accordance with Section XI of the ASME Boiler and Pressure vessel Coce, 1983 Edition and Addenda through Summer 1983.

3/4.4.11 REACTOR COOLANT SYSTEM VENTS Reactor Coolant System vents are provided to exhaust noncondensible gases and/or steam from the Reactor Ccolant System that ceuld inhibit natural circu-lation core cooling. The OPERABILITY-of least one Reactor Coolant System vent path from the reactor vessel head and the pressurizer steam space ensures that the capability exists to perform this function.

The valve redundancy of the Reactor Coolant System vent paths serves to minimize the probability of inadvertent or irreversible actuation while ensuring that a single f ailure of a vent valve, power supply, or control system does not prevent isolation of the vent path.

The function, capabilities, and testing requirements of the Reactor Coolant System vents are consistent with the requirements of Item II.B.1 of HUREG-0737, Clarification of TMI Action Plant Requirements," November 1980.

l 1

l SEABROOK - UNIT 1 B 3/4 4-16

Insert for BASES Page 3/4 4-16 When operating below 200*F in MODE 5 or MODE 6, Technical Specification 3.5.3.2 allows one Safety injection pump to be made OPERABLE whenever the RCS has vent area equal to or greater than 18 square inches. Cold overpressure protection in this configuration is provided by the 18 square inch or greater mechanical opening in the RCS pressure boundary.

This mechanical opening is larger in size than the 1.58 square inch opening required for normal overpressure protection and is of sufficient size to ensure that the Appendix G limits are not exceeded when an SI pump is operating in MODE 5 or MODE 6. Additionally, when operating in a reduced inventory condition, the larger vent area limits RCS pressure during overpressure transients to reduce the possibility of adversely affecting steam generator nozzle dams. When the reactor has been shut down for at least 7 days, the larger vent area also enhances thc ability to provide a gravity feed to the RCS from the Refueling Water Storage Tank in the unlikely event that the CCP and Si pumps were unavailable after a loss of RHR.

3/4.5 EMERGENCY CORE C0OLING SYSTEMS j$2 BASES -

q) 3/4.5.ljCCUMULATORS D e 3dRABILITY of each Reactor Coolant System (RCS) accumulator ensures that a tufficient volume of borated water will be immediately forced into the reactor core through each of the cold legs in the event the RCS pressure falls below the pressure of the accumulators. This initial surge of water into the core provides the initial cooling mechanism during large RCS pipo ruptures.

The limits on accumulator volume, boron concentration, and pressure ensure that the assumptions used for accumulator injection in the safety analysis are met.

The accumulator power-operated isolation valves are considered to be

" operating bypasses" in the context of IEEE Std. 279-1971, which requires that bypasses of a protective function be removed automatically whenever permissive conditions are not met. In addition, as these accumulator isolation valves fail to meet single-failure criteria, removal of power to the valves is required.

The limits for operation with an accumulator inoperable for any reason except an isolation valve closed minimizes the time exposure of the plant to a LOCA event occurring concurrent with failure of an additional accumulator which may result in unacceptable peak cladding temperatures. If a closed isolation g valve cannot be immediately opened, the full capability of one accumulator is Q$n

~

not available and prompt action is required to place the reactor in a mode where this capability is not required.

3/4.5.2 and 3/4.5.3 ECCS SUBSYSTEMS The OPERABILITY of two independent ECCS subsystems ensures that suf ficient emergency core cooling capability will be availabi'e in the event of a LOCA assuming the loss of one subsystem through any single-failure consideration.

Either subsystem operating in conjunction with the accumulators is capable of supplying sufficient core cooling to limit the peak cladding temperatures within acceptable limits for all postulated break sizes ranging from the

-double ended break of the largest RCS cold-leg pipe downward. In addition, each ECCS subsystem provides long-term core cooling capability in the recirculation mode during the accident recovery period.

With the RCS temperature below 350 F, one OPERABLE ECCS subsystem is acceptable without single failure consideration on the basis of the stable reactivity condition of the reactor aid the limited core cooling requirements.

The limitation for a maximum of one centrifugal charging pump to be OPERABLE and the Surveillance Requiremen', to verify all charging pum'ps and safety injection pumps except the requireC OPERABLE charging pump to be in-operable in MODES 4 and 5 and in MODE 6 with the reactor vessel he'ad on pro-vides assurance that a mass addition pressure transient can be relieved by the

. operation of a single PORV or RHR suction relief valve.

W 2"N S E R Y SEABROOK - UNIT 1 B 3/4 5-1

9-l Insert for BASES Page B 3/4 51

, 1 1

When the RCS has a vent area equal to or greater than 18 square laches,.one Safety Injection pump may be made OPERABLE when in MODE' S or MODE 6 (below 200'F).

When' operating in this configuration, cold overpressure protection is provided by the

.;?chanical vent opening, equal to or greater than 18 square inches, that is required to be present la the RCS boundary prior to making the SI pump OPERABLE, This required RCS vent area and the surveillancs requirement to verify the presence of the RCS vent area provides assurance that a mass addition transient can be relieved and that adequate cold overpressure protection is provided, f

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New ilampshire Yankee April 24,1991 ENCLOSURE 3 TO NYN 91067 NO SIGNIFICANT HAZARDS CONSIDER ATION

\ .

i NO SIGNIFICANT H AZARDS CONSIDER ATION Backcround NRC Ger.cric Letter 8817, ' Loss of Decay Heat Removal *, requires that prior to operating in a reduced inventory condition, at ! cast two available means of adding inventory to the Reactor Coolant System (RCS) be provided in addition to pumps which are part of the normal decay heat removal system. These means are to include at least one high pressure injection pump. Currently, the Seabrook Station Technical Specifications require that all Safety injection (SI) pumps be inoperable in MODE 5 and in MODE 6 with the reactor vessel head on to preclude RCS mass addition transients which are more severe than that assumed in the design basis for the Cold Overpressure Mitigation System (COMS). The proposed changes will allow one SI pump to be made operable when the plant is in either MODE 5 or MODE 6 with the reactor vessel acad on when an adequate mechanical venting capabinty exists to preclude overpressure of the RCS.

Descriotion of Prooosed Chances The changes proposed are to Technical Specification 3.5.3.2, BMERGENCY CORE C,00 LING SYSTEMS. ECCS SUBSYSTEM 1 T.,, LESS TH AN 350'F. ECCS SUBSYSTEMS T.,, EOU AL TO OR LESS TH AN 200'F. LIMITING CONDITION FO" OPER ATION:

Technical Specification 4.5.3.2, the associated SURVEILLANCE REOUIREMENTS: and the Technical Specification BASES for 3/4.d.9 PRESSURE / TEMPER ATURE LIMITS and 3/4.5.2 AND 3/4.5.3 ECCS SUBSYSTEMS.

a. Technical Soccification 3.5.3.A The proposed change to Technical Specification (TS) 3.5.3.2 would allow one Safety injection (SI) pump to be made OPERABLE when the plant is operating in either MODE 5 or MODE 6 and a Reactor Cooiant System (RCS) vent equel to or grester than 18 square inches is established.

Currently, when the plant is in either MODE 5 or MODE 6 with the reactor vessel head on, all Si pumps are required by existing TS 3.5.3.2 to be inoperable, in order to prevent RCS mass addition transients more severe than those assumed in the design basis for the Cold Overpressure Mitigation System (COMS) setpoints. The pumps are made inoperable by securing the pump motor circuit breakers in an open position. The proposed change would allow one SI pump to be made OPERABLE by restoring the associated motor circuit breaker to a closed position whenever an RCS vent area equal to or greater than 13 square inches is established. This change addresses programmed enhancement (3b) of NRC Generic Letter 8817 and provides an additianal means of adding inventory to the RCS. The use of the Si pump provides a diverse and redundant means to makeup RCS inventory in the event the Residual Heat Removal System and the Centrifugal Charging Pump became unavailable while the plant is operating in a reduced inventory condition.

1 l

The Limiting Condition for Operation (LCO) of this specification has been revised i to state the number of Safety injection pumps that, as a minimum, must be inoperable under  ;

two unique plant configurations. These configurations are 1) with an RCS vent ar a less l than 18 square inches and 2) with an RCS vent area equal to or greater than 18 square j inches. The Action Statement has also been rewritten in terms of the required number of inoperable pumps rather than addressing an OPERABLE pump.

In order to provide overpressure protection of the reactor vessel Appendix G pressure / temperature limits during this mode of operation, the proposed changes to TS 3.5.3.2 requires that a mechanical opening equal to or greater than 18 square inches must be present is the RCS pressure boundary prior to making the Si pump operable. The size of the required mechanical opening was determined by analysis to be 18 square inches. This area is less than 21 square inches, the free flow area of one pressurizer safety vahe flange, thus the removal of one safety valve would provide the required vent area.

The Surveillance Requirement has been rewritten to be consistent with the Action Statement and to requhe a demonstration of inoperability by verification that the motor circuit breaker is secured in the open position for those pumps required to be inoperable.

Additionally, the asterisk (') has been deleted from the surveillance requirement and relocated to part a, of the LCO to ensure that inoperable pumps are energized for testing while isolated from the RCS, only when no Safety injection pumps are OPERABLE.

The additional surveillance requirement that was included in the December 14, 1990 submittal has been relocated to Technical Specification 3.4.9.3 and is discussed in item b.

below.

Additionally, the page subtitle was revised to climinate the heading "ECCS Subsystems - Tavg Equal to or Less Than 350,F". This specification is applicable in, MODE 5 and MODE 6 and therefore only applies when Tavg is equal to or less than 200 F.

b. Technical Snecification 3,4A3 This specification was revised to establish the requirements for the overpressure protection in one specification and to consolidate the surveillance requirements. This is a change from the original submittal which specified the requirement for the RCS vent area and the surveillance requirement in Technical Specification 3.5.3.2.

Specification 3.4.9.3 has also been revised to specify which overpressure protection systems are required to be OPER ABLE in twa unique plant configurations.

e First, for operation in MODE 4 when the temperature of any RCS cold leg is less than or equal to 329'F; and in MODE 5 and MODL 6 with all Safety injection pumps inoperable, the required overpressure '

protection systems are specified. There are no changes to the i

overpressure protection system descriptions with the exception of adding I the word

• area" in item 3).

l 2

i e A second plant configuration was addressed which ir, operation in MODE 5 or MODE 6 with all Safety injection pumps, except one inoperable. In this configuration the requirement to depressurize the RCS with a vent area equal to or greater than 18 square inches is added. The 18 square inch vent provides the overpressure protection to ensure that the Appendix 0 limits are not exceeded.

Similar changes are made to the action statements that must be taken in these two plant configurations.

Surveillance Requir;ments 4.4.9.3.3 was revised to add the words valve (r.) or device (s).

This change would allow a device to be locked in place in the RCS opening to ensure ,

the required vent path is maintained. The removal of a pressurizer safcty valve is one of the methods being considered to establish the required vent area equal to or greater than 18 square inches. When the safety valve is removed it is expected that some type of screen will be installed to keep debris from the RCS. If the device were locked in place, the equivalent surveillance requirement would be applied as now exists from a vent pathway that is provided by a valve that is locked in the open position. It should be noted that by revising the submittal to utilize the surveillance / requirements of specification 4.4.9.3.3 the surveillance frequency from our original submittal has been reduced from 24 to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and introduces additional conservatism,

c. Iluses Two changes are proposed to the BASES for TS 3/4.4.9.

e As noted in the existing BASES, operation below 350'F but above 325'F with all Centrifugal Charging Pumps (CCP) and Safety injection (SI) pumps operable, is allowed for up to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The first proposed change is a clarification of the wording dealing with the reasoning behind the assumption ~

that there will be no single failure of a PORV in conjunction with an inadvertent actuation of a single ESF train. The existing sentence is not complete. The proposed change inserts the appropriate words and punctuation to make the sentence complete. This change is just a wording clarification of an existing aspect of the BASES and does not change the intent or meaning of the BASES.

e The second change to the llASES for TS 3/4.4.9 is to insert a discussion of the basis for the proposed revision to the requirement that both Si pumps be locked out while in MODES 4, 5 and 6. The change describes that one Si pump may be operable while in MODE 5 or MODE 6 whenever the required RCS vent area equal to or greater than 18 square inches is established. The overpressure protection for a mass addition transient is prosided by the RCS vent area equal to or greater than 18 square inches.

3

Finally, a change is also proposcd to the IIASES of TS 3/4.5.3 to describe the basis for the proposed revision to the requirement to lockout both Si pumps in MODE 5 and MODE 6. The change describes the requirement to verify the existence of the adequate RCS vent area prior to making an SI pump OPERAllLE and the surveillance requirement to verify the presence of the RCS vent area on a peri ?dic bases.

Encineerine Evaluation The 1.58 square inch vent area specified in Technical Specification (TS) 3.4.9.3c is the equivalent flow area of a single pressurizer power operated relief valve (PORV). The relid capacity of a single pressurizer PORV is sufficient to prevent violation of the Appendix G pressure limits for the current Cold Overpressure Mitigation System (COMS) system design ..

% sis events The current COMS design basis events and mass addition assumptions are either: (1) cperation of a single Centrifugal Charging Pump (CCP) or a single Safety injection (SI) ps,mp without letdown (limiting mass addition events), or, (2) inadvertent start of a Reactor Coolant Pump with a 50'F temperature differential between the Reactor Coolant System (RCS) and Steam Generator (SG) secondary temperatures (limiting heat addition event). The 18 square inch vent area specified in the proposed change to TS 3.5.3.2, therefore, provides inore than the minimum vent area which would be sufficient to preclude violation of Appendix G pressure limits for the COMS design basis events.

Since TS 3.5.3.1 and TS 3.5.3.2 currently prohibit operation of an Si pump in Modes 4, 5 and 6, the COMS design basis does not include simultaneous operation of a CCP and an SI pump. Implementation of the proposed TS change would allow one SI pump to be made operable in Modes 5 and 6. As a result, a mass addition transient more limiting than the current COMS system design basis mass addition event becomes possible. This event is cht.racterized by mass addition from the simultaneous operation of both a single CCP and a single Si pump, with no letdown. A vent flow area greater than 1.58 square inches is required to prevent violation of the Appendix G limits during such an event. The pressure relief capacity afforded by the 18 square inch vent area specified in the proposed change to TS 3.5.3.2 is more than sufficient to prevent violation of the Appendix G pressure limits for this event. The anticipated method of providing this vent area is removal of a pressurizer safety valve (SV) from its flange or optionally, opening a pressurizer manway.

A vent area larger than that required based upon Appendix G overpressure protection requirements was conservatively specified after consideration was given to two other factors influencing mid loop operation as discussed below:

e if operating with SG nozzle dams in place, in . order to avoid exposure of plant personnel to reactor coolant due to nozzle dam failure, it is necessary to provide a vent capable of maintaining the pressure in the RCS hot and cold legs lower than the allowable pressure differential across the nozzle dams in order to preclude failure.

The tel square inch vent area specified is sufficient to limit the pressure differential across the SG nozzic dams during the new mass addition event to 33 psig, which is less than the 56.5 psig design pressure differential of the nozzle dams which may be used at Seabrook. In-the event of a loss of Residual Heat Removal (RilR) cooling during mid loop operation, the 18 square inch vent area (as provided by rernoval of a single pressurizer SV) also provides adequale steam relief capacity to prevent RCS pressure from exceeding the SG nozzle dam design pressure differential assuming the plant has been shutdown for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. The equilibrium RCS pressure is 4

espected to be 46 psig following a loss of RilR shutdown cooling, during mid loop operation,48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after shutdown utilizing best estimate decay heat and no makeup flow so that decay heat is removed by vaporization of saturated liquid.

e in addition to the SI pump and the CCP, gravity feed from the Refueling Water Storage Tank (RWST) to the RCS is possible at Scabrook subject to RCS (hot leg) pressure and RWST level. With an RWST level of 25%, gravity feed is possible with RCS pressures up to 32 psig. With a full RWST, gravity feed is possible up to an RCS pressure of 45 psig. The RCS pressures discussed above are substantially below the Appendix G pressure limit. A vent path larger than the 1.58 square inches specified in TS 3.4.9.3c is required to meet Appendix 0 limits and to allow gravity feed from the RWST. Removal of a single pressurizer SV from its flange (which .

provides a vent area slightly greater than the 18 square inches specified in tLe proposed change to TS 3.5.3.2) is the smallest vent path under consideration for this purpose. This vent path is sufficient to pass the steaming rates associated with decay heat remo'al via saturated steam cooling while maintaining RCS hot leg pressures 1-45 psig, for shutdown times in excess of 168 hours0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br /> (7 days)t and maintaining RCS hot leg pressure 132 psig, for shutdown times in excess of 360 hours0.00417 days <br />0.1 hours <br />5.952381e-4 weeks <br />1.3698e-4 months <br /> (15 days).

Gravity feed from the RWST is a backup means of providing RCS makeup and cooling. The primary method is to utilize the RHR system, if RHR were to fail the Coolant Charging System, using the CCP, and the Safety injection System, using the Si pump are the primary backups systems to provide additions to the RCS inventory.

Gravity feed from the RWST is available to backup these systems in the unlikely event that both the CCP and SI pumps are unavailable after a loss of RHR.

The 18 square inch vent area specified in the proposed change to TS 3.5.3.2 therefore represents a conservatively large vent area with respect to Appendix G overpressure protection requirements, and a minimum desirahle vent area with respect to these other considerations. Seabrook Station procedures will include administrative controls to ensure that a vent path of at least 18 square inches is established pric,r to making the Si pump available for use in a reduced inventory condition.

NO SIGNIFICANT H AZARDS CONSIDER ATION CONCLUSION New Hampshire Yankee has reviewed the proposed changes in accordance with the criteria specified in 10 CFR 50.92, and based upon the information provided in the revised Technical Specifications and above has determined that the proposed changes would not:

1. Involve a significant increase in the probability or consequences of any accident previously evaluated. The only accident potentially affected by the proposed change to allow operation of an SI pump when the RCS has a vent area equal to or greater ll an 18 square inches is the low temperature overpressurization mass addition transient. The probability of this event is not affected since the operable Safety injection (SI) pump would only be made OPERABLE after the suitable vent area in the Reactor Coolant System pressure boundary had been established. The creation of this vent area is similar to the existing requirement in Technical Specification 3.4.9.3.c to provide an RCS vent of at least 1.58 square inches in the event that neither of the COMS alternate relief valve configurations is available. The maximum possible flow rate into the Reactor Coolant System (RCS) during the mass addition transient will be 5

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increased, however this does not increase the consequences of this type of accident. The consequences of such an event would be mitigated by ensuring that a suitable vent area in the RCS pressure boundary exists prior to making an Si pump OPERABLE. This vent area will prevent any transient induced pressure increase from exceeding the 10 CPR 50 Appendix 0 pressure limit.

The inclusion of the surveillance requirement in Technical Specification 3.4.9.3.3 casures that the RCS sent area is maintained. Additionally, by providing an additional source of reactor vessel inventory, the proposed change reduces the consequences of a malfunction of the Residual 11 cat Removal (R11R) system.

2. Create the possibility of a new or different kind of accident from any previously evaluated. Allowing a SI pump to be operable in these modes creates the possibility of a more severe mass addition transient than those within the capability of the Cold Overpressure Mitigation System (COMS),

flowever, the proposed requirement to provide an RCS vent aru equal to or greater than 18 square inches prior to making the Si prmp OPERABLE provides overpressure protection for the Appendix 0 limit. 'T his prerequisite to provide the RCS vent area prior to allowing one (1) SI pump to be OPERABLE is similar to the existing requirement in Technical Specification 3.4.9.3e to provide an RCS vent of at least 1.58 squate inches in the event that neither of the COMS alternate relief valve configurations is available. The opening of a small vent in the RCS pressure boundary to provide overpressure protection is not a new or different approach than that currently used for low temperature overpressure protection and therefore does not create the possibility of a new or different type of accident than any previously evaluated.

3. Involve a significant reduction in a margin of safety. The proposed changes would allow one Si pump to be made OPEP ABLE in MODE 5 and MODE 6 creates the possibility of a mass addition transient more severe than those considered in the COMS design basis, llowever, the requirement to provide a suitably sized RCS vent area prior to making the Si pump OPERABLE will ensure that no violation of Appendix 0 limits will occur for such au event and no reduction of margin of safety for overpressure protection con occur. The utilization of the RCS vent area equal to or greater than 18 square inches provides protection of the reactor vessel Appendix G limit independent of the COMS system. Therefore the proposed changes do not result in a reduction in the margin of safety.

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