ML20248M222

Revised Tech Specs Pages,Changing TS Bases Section 3/4.7.1.5 to Reword Section Which Describes Limiting Temperature Case for Containment Analysis

ML20248M222
Person / Time
Site:	Millstone
Issue date:	06/04/1998
From:	NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20248M221	List: B17257, Forwards Change to TS Bases Section 3/4.7.1.5,rewording Section Which Describes Limiting Temperature Case for Containment Analysis ML20248M222
References
NUDOCS 9806150165
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Text

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l Docket No. 50-423 l

B17257 l

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i Millstone Nuclear Power Station, Unit No. 3 Marked Up Technical Specification Page i

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l Jurie 1998 l

9906150165 990604 PDR ADOCK 05000423 p

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April 10, 1997

' Verified Revision _9/a /9 7 -

PLANT SYSTENS

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Date37M L.

BASES O

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3/4.7.1.5 MAIN STEAM LINE ISOLATION VALVES o

BACKGROUND o

The main steam line isolation valves (MSIVs) is' olate steam flow from the ks secondkry side of the steam generators following a high energy line break

_g (HELB). MSIV closure. terminates flow from the unaffected (intact) steam generators.

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One MSIV is located in each main steam line outside, but close to, d

containment. The MSIVs are downstream from the main steam safety valves l'

(MSSVs) and auxiliary feedwater (AFW) pump turbine steam supply, to prevent-

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MSSV and AFW isolation from the steam generators by MSIV closure.

Closing the

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MSIVs isolates.each steam generator from the others, and isolates the turbine,

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Steam Bypass System, and other auxiliary steam supplies from the steaii ~

g generators.

W The MSIVs close on a main steam isolation signal generated by low steam kd generator pressure, high containment pressure, or steam line pressure negative rate (high). The MSIVs fail closed on loss of control or actuation power.

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Each MSIV has an MSIV bypass valve. Although these bypass valves are normally E

closed,. they receive the same emergency closure signal as do their associated

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MSIVs.

The HSIVs may also be actuated manually.

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' A description of the MSIVs is found in 1.he FSAR, Section 10.3.

e 4o S W} a y APPLICABLE SAFETY ANALYSIS 4 *g j

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l The design basis of the MSIVs is established by the containment analysis for r g d) o.

e the large steam line break (SLB) inside containment, discussed in the FSAR, g

ob g Section 6.2.

It is' also affected by the accident analysis of the SLB events rgv presented in.the FSAR, Section 15.1.5.

The design precludes the blowdown of 4)4 g 1

o more than one steam generator, assuming a single active component failure d

(e.g., the failure of one MSIV to close on demand).

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a The limiting temperature case for the containment analysis is the SLB inside containment, :ith : '::: f Off:ite p:=rlfollowing turbine trip, and failure of the MSIV on the affected steam generator to close. IAt hot zero power, the steam generator inventory and temperature are at their maximum, maximizing the SR i

analyzed mass and energy release to the containment. Due to reverse flow and failure of the MSIV to close, the additional mass and energy in the steam i

headers downstream from the other MSIV contribute to the total release. With the most reactive rod cluster control assembly assumed stuck in the fully withdrawn position, there is an increased possibility that the core will become critical and return to power. The reactor is ultimately shut down by the boric acid injection delivered by the Emergency Core Cooling System.

MILLSTONE - UNIT 3 8 3/4 7-3 Amendment No. JJ7, M

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1 Docket No. 50-423 4

B17257 1i t

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1 Millstone Nuclear Power Station, Unit No. 3 Retyped Technical Specification Page l

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June 1998 I

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PLANT SYSTEMS BASES 3/4.7.1.5 MAIN STEAM LINE ISOLATION VALVES BACKGROUND The main steam line isolation valves (MSIVs) isolate steam flow from the secondary side of the steam generators following a high energy line break (HELB). MSIV closure terminates flow from the unaffected (intact) steam generators.

One MSIV is located in each main steam line outside, but close to, containment. The MSIVs are downstream from the main steam safety valves (MSSVs) and auxiliary feedwater (AFW) pump turbine steam supply, to prevent MSSV and AFW isolation from the steam generators by MSIV closure.

Closing the MSIVs isolates each steam generator from the others, and isolates the turbine, Steam Bypass System, and other auxiliary steam supplies from the steam generators.

The MSIVs close on a main steam isolation signal generated by low steam generator pressure, high containment pressure, or steam line pressure negative rate (high). The MSIVs fail closed on loss of control or actuation power.

Each MSIV has an MSIV bypass valve. Although these bypass valves are normally closed, they receive the same emergency closure signal as do their associated MSIVs. The MSIVs may also be actuated manually.

A description of the MSIVs is found ir, the FSAR, Section 10.3.

APPLICABLE SAFETY ANALYSIS The design basis of the MSIVs is established by the containment analysis for

'the large steam line break (SLB) inside containment, discussed in the FSAR, Section 6.2.

It is also affected by the accident analysis of the SLB events presented in the FSAR, Section 15.1.5.

The design precludes the blowdown of more than one steam generator, assuming a single active component failure (e.g., the failure of one MSIV to close on demand).

The limiting temperature case for the containment analysis is the SLB inside containment, at 75% power with mass and energy releases based on offsite power available following turbine trip, and failure of the MSIV on the affected steam generator to close.

'At hot zero power, the steam generator inventory and temperature are at their maximum, maximizing the analyzed mass and energy release to the containment.

Due to reverse flow and failure of the MSIV to close, the additional mass and energy in the steam headers downstream from the other MSIV contribute to the total release. With the most reactive rod cluster control assembly assumed stuck in the fully withdrawn position, there is an increased possibility that the core will become critica'i and return to power.

The reactor is ultimately shut down by the boric acid injection delivered by the Emergency Core Cooling System.

MILLSTONE - UNIT 3 B 3/4 7-3 Amendment No. JJ7, J7J, 0591