ML20210K363

Marked-up & Revised TS Bases Page B 3/4 5-2 Re ECCS

ML20210K363
Person / Time
Site:	Seabrook
Issue date:	07/30/1999
From:	NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO)
To:
Shared Package
ML20210K331	List: ML20210K328 ML20210K363
References
NUDOCS 9908060087
Download: ML20210K363 (4)

Text

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. 'ENERGENCY CORE COOLING SYSTEMS

^

BASES 3/4.5.2 and 3/4.5.3 ECCS SUBSYSTEMS (Continued) /

When the RCS has a vent area equal to or greater than 18 square inches, 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 f provided by the mechanical vent opening, equal to or greater than 18 square inches that is required to be present in the RCS boundary prior to making the SI pump, OPERABLE. This required RCS vent area and the surveillance requirement to verify the presence of the RCS vent area provides assurance that a mass t addition transient can be relieved and that adequate cold overpressure protection is provided. 3 gp -

j The Surveillance Requirements provided'to ensure PERABILITY of each com-ponent ensures that at a minimum, the assumptions used in the safety analyses are met and that subsystem OPERABILITY is maintainid. Surveillance Requirements for throttle valve position stops and flow balance testing provide assurance that proper ECCS flows will be maintained in the event of a LOCA. Maintenance of proper flow resistance and pressure drop in the piping system to each injec-tion point is necessary to: (1) prevent total pump flow from exceeding runout conditions when the system is in its minimum resistance configuration, (2) pro-vide the proper flow split between injection points in accordance with the assumptions used in the ECCS-LOCA analyses, and (3) provide an acceptable level of total ECCS flow to all injection points equal to or above that assumed in,the ECCS-LOCA analyses. -

3/4.5.4 REFUELING WATER STORAGE TANK The OPERABILITY of the refueling water storage tank (RWST) as part of the ECCS ensures that a sufficient supply of borated water is available for injection by the ECCS in the event of a LOCA. The limits on RWST minimum volume and boron concentration ensure that: (1) sufficient water is available within containment to permit recirculation cooling flow to the core and (2) the reactor will remain subcritical in the cold condition following mixing of the {

RWST and the RCS water volumes with all control rods insertad except for the most reactive control assembly. These assumptions are consistent with the LOCA analyses.

The contained water volume limit includes an allowance for water not usable because of tank discharge line location or other physical characteristics.

The limits on contained water volume and boron concentration of the RWST also ensure a pH value of between 8.5 and 11.0 for the solution recirculated within containment after a LOCA. This pH band minimizes the evolution of iodine and minimizes the effect of chloride and caustic stress corrosion on mechanical systems and components.

SEABROOK - UNIT 1 -

8 3/4 5-2 Amendment No.

9908060087 990730 PDR ADOCK 05000443 P PDR I

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With the exception of the operating centrifugal charging pump, the ECCS pumps are n standby, non-operating of entrained gases. Maintainin mode. As such, flow path iping has the potential to develop void at the accessible ECCS$g the piping from th CCC'; ymup to the RCS full of water (by verifyin

diping high' points and pump casings, excluding the operating centrifugal charging pump) ensures that the system will perform properly, injecting its fu the RCS upon demand. This will also prevent water hammer, pump cavitation and pumpi condensable gas (e.g., air, nitrogen, or hydrogen) into the reactor vessel following a safet signal or during shutdown cooling. The 31 day Frequency takes into consideration the gradu gas accumulation in the ECCS piping and the procedural controls governing system operation.

U P

EMERGENCY CORE COOLING SYSTEMS j

BASES 3/4.5.2 and 3/4.5.3 ECCS SUBSYSTEMS (Continued) i When the RCS has a vent area equal to or greater than 18 square inches, one Safety injection pump may be made OPERABLE when in MODE G or MODE 6 (below 200 F). When operating in this configuration, cold overpressure protection is provided by the mechanical vent opening, equal to or greater than 18 l square inches, that is required to be present in the RCS boundary prior to making the Si pump

) OPERABLE. This required RCS vent s rea and the surveillance 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.

1 The Surveillance Requirements provided to ensure OPERABILITY of each component ensures that at a minimum, the assumptions used in the safety analyses are met and that subsystem OPERABILITY is maintained. With the exception of the operating centrifugal charging pump, the ECCS pumps are normally in a standby, non-operating mode. As such, flow path piping h :s the potential to develop voids and pockets of entrained gases. Maintaining the piping from the refueling water storage tank l

(RWST) to the RCS full of water (by veriffing at the accessible ECCS piping high points and pump casings, excluding the operating centrifugal charging pump) e,nsures that the system will perform properly, injecting its full capacity into the RCS upon demand. This will also prevent water hammer, pump cavitation, and pumping of non-condensable gas (e.g., a r, nitrogen, or hydrogen) it'to the reactor vessel following a safety injection (SI) signal or during shutdown ccoling. The 31 day Frequency takes into consideration the gradual nature of gas accumulation in the ECCS piping and the procedural controls governing aystem operation.

l Surveillance Requirements for throttle vah'e position stops and flow balance testing provide assurance that l proper ECCS flows will be maintained in the event of a LOCA. Maintenance of proper flow resistance and pressure drop in the piping system to each injection point is necessary to: (1) prevent total pump flow from exceeding runout conditions when the system is in its minimum resistance configuration, (2) provide the proper flow split between injection points in accordance with the assumptions used in the ECCS-LOCA analyses, and (3) provide an acceptable level of total ECCS flow to all injection points ec"al to or above that assumed in the ECCS-LOCA analyses.

3/4.5.4 REFUELING WATER STORAGE TANK l The OPERABILITY of the refueling water storage tank (RWST) as part of the ECCS ensures that a sufficient supply of borated water is available for injection by the ECCS in the event of a LOCA. The limits on RWST minimum volume and boron concentration ensure that: (1) sufficient water is available within containment to permit recirculation cooling flow to the core and (2) the reactor will remain suberitical in the cold condition following mixing of the RWST and the RCS water volumes with all control rods inserted except for the most reactive control assembly. These assumptions are consistent with the LOCA analyses.

The contained water volume limit includes an allowance for water not usable because of tank discharge line location or other physical characteristics.

SEABROOK- UNIT 1 B3/45-2 Amendment No. 5