ML17221A565

Proposed Tech Spec 3.7.1.6,changing Action Statement to Allow 72 H to Restore Inoperable,Open Main Feedwater Isolation Valve to Operable Status

ML17221A565
Person / Time
Site:	Saint Lucie
Issue date:	12/22/1987
From:	FLORIDA POWER & LIGHT CO.
To:
Shared Package
ML17221A564	List: ML17221A563 ML17221A565
References
NUDOCS 8712300081
Download: ML17221A565 (11)

Text

ATTACHMENT l Marked-up Technical Specification Pages 3/4 7- I 0 B 3/4 7-3 (with insert) 87i2300081 871222 i Da. ~DOCK-O500OZ89-

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PLANT SYSTEMS t

MAIN FEEDWATER LINE ISOLATION VALVES LIMITING CONDITION FOR OPERATION 3.7.1.6 Each main feedwater line isolation valve shall be OPERABLE.

APPLICABILITY: MODES .1, 2, 3, and 4.

ACTION:

MODE 1 With one main feedwater line isolation lve inoperable but open, POWER OPERATION may continue p'rovided he inoperable valve is restored to OPERABLE status within hours; otherwise, be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

MODES 2, 3 - With one main feedwater line isolation valve inoperable, and 4 subseqent operation in MODE 2, 3, or 4 may proceed provided:

a. The isolation valve is maintained closed.

b. The'p> ovisions of Specification 3. 0. 4 are not applicable.

Otherwise, be in at least HOT STANDBY within the next 6 hours and in COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

SURVEILLANCE RE UIREMENTS 4.7.1.6 Each main feedwater line isolation valve shall be demonstrated OPERABLE by:

a. Part-stroke exercising the valve at least once per 92 days, a'nd

b. Verifying full closure within 5.15 seconds on any closure actuation signal while in HOT STANDBY with Tavg > 515'F during each reactor shutdown e'xcept that verification of full closure within 5.15

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seconds need not be determined more often than once per 92 days.

ST. LUG IE - UNIT 2 3/4 7-10 Amendment No. B

.PLANT SYSTEMS BASES 3/4. 7. 1.4. ACTIVITY The limitations on secondary system specific activity ensure that the resultant offsite radiation dose will be limited to a small fraction of 10 CFR Part 100 limits in the event of a steam line rupture. This dose also includes the effects of a coincident 1.0 gpm primary to.secondary tube leak in the steam generator of the affected steam line and a concurrent loss of offsite electrical power. These values are consistent with the assumptions used in the safety analyses'/4.7.1.5 MAIN STEAM LINE ISOLATION VALVES The OPERABILITY of the main steam line isolation valves ensures that no more than one steam generator will blow down in the event of a steam line rupture. This restriction is required to (1) minimize the positive reactivity effects of the Reactor Coolant System cooldown associated with the blowdown, and (2) limit the pressure rise within containment in the event the steam line rupture occurs within containment. The OPERABILITY of the main steam isolation valves within the closure times of the Surveillance Requirements is consistent with the assumptions used in the safety analyses.

3/4. 7. 1e 6 MAIN FEEDWATER LINE ISOLATION VALVES The main feedwater line isolation valves are required to be OPERABLE to ensure that (1) feedwater is terminated to the affected steam generator following a steam line break and (2) auxiliary feedwater is delivered to the intact steam generator following a feedwater line break. If feedwater is not terminated to a steam generator with a broken main steam line, two serious effects may result:

(1) the post-trip return to power due to plant cooldown will be greater with resultant higher fuel failure and (2) the steam released to containment will exceed the design.

u to re ova of th m in fee c ck val from the lant des gn and

'tion it repla ent wit second in feedwa er line al th e is t ng other t an the in feedw e line o tion alves o revent ck flow o W fol win a fe d ne br ak. his may re 1 in a 1 of con ens in ntory a the p e ial r ot being le to fe the st am ge r or.

The concern is the fai lure of one main feedwater line isolation valve to close with the other main feedwater line isolation valve in that line being inoperable (i.e., stuck open). It is thus desired to preclude operation for extended periods with a main feedwater line isolation va'.ve known to be stuck in the 'open position.

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INSERT 8'1 Two redundant main feedwater isolation valves (MFIV's) are provided in each main feedline to assure feedwater isolation in the event of a steam line break with a single failure. Also, redundant MFIV's assure that backflow in the feedlines is prevented following a feedline break.

INSERT P2 A time limit of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> on operations with an inoperable main feedwater isolation valve provides assurance that operations will not continue for an extended period with a failed, open MFIV.

ATTACHMENT 2 SAFETY EVALUATION I. INTRODUCTION The existing ACTION statement for the St. Lucie Unit 2 Technical Specifications Section 3/4.7.1.6, Main Feedwater Isolation Valves (MFIV) allows operations to continue four (4) hours with an inoperable, open MFIV. This ACTION statement does not provide adequate time to analyze an MFIV problem and effect repairs.

As a result, there exists the potential for unnecessary plant shutdowns.

This proposed change to the Technical Specifications will modify the Section 3/4.7.1.6 ACTION Statement for an inoperable, open MFIV to allow operations to continue for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> instead of the present four (4) hour limit. If the valve cannot be restored to OPERABLE, the plant would be placed in HOT STANDBY in the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and COLD SHUTDOWN within the following twenty-four (24) hours.

II. DISCUSSION AND ANALYSIS The MPIVs are required to be OPERABLE to ensure that feedwater flow to the affected steam generator is terminated in the event of a main steamline break (MSLB). If main feedwater flow is not terminated, two effects may result: (1) the post-trip return to power may be greate'r with resultant higher fuel failure and, (2) the steam release to the containment may exceed containment design pressure if the break is inside containment.

Additionally, the MFIVs function to ensure that auxiliary feedwater (AFW) can be delivered to the intact steam generator in the event of a main feedline break (MPLB). Back flow of the AFW to the Main Feedwater System following a feedline break could result in a loss of condensate inventory and the potential for not being able to feed the intact steam generator.

The closure of a single MPIV in each feedline, as required by the safety analysis, provides isolation of main feedwater and availability of AFW following a steamline or feedline break.

The second MPIV ensures that a single failure which precludes closure of one valve will not preclude main feedwater isolation or AFW availability.

The proposed change is acceptable for the following reasons:

(A) Under current Technical Specifications, operation with an inoperable,

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ATTACHMENT 2 Page 2 of 3 open MFIV is allowed for four hours. In the event of a Design Basis Event (DBE) during this period, failure to terminate feed flow would require that: 1) the second MFIV in the same line as the first valve must also fail open, 2) a main steam line (or feed line) break must occur and the affected steam generator (or feed line) must be the one fed by the line which has two failed MFIVs, and 3) this series of events must occur during the action time (4 .hours) identified in the LCO.

The likelihood of this sequence of events occurring is very low.

In order to gain perspective on the significance of the proposed change, from 4 to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, 1) an estimated MFIV fail open frequency per NUREG 2728 (lE-3 per demand) can be combined with

2) an estimate of the frequency of MSLB as given in the Zion PRA (9.4E-04) to provide a conservative estimate of the failure to terminate flow given a MSLB event occurs during operation with one MFIV inoperable, open. Review of NPRDS data for January, 1985 to May, 1987 revealed one LER written on the MFIVs.

Therefore, an assumption of entering an LCO once per year is conservative. Using the described rationale provides a conservative estimate which can help illustrate the relative significance of a change from a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action time.

(MFIV fails open) x (MSLB) x (LCO Action Time) = frequency of failure to terminate flow during MSLB (1E-03/d) x (9.4E-4/Rx yr) x (4 hr) (1/8760 yr/hr) = 4.3E-10/d (1E-03/d) x (9 'E-4/Rx yr) x (72 hr) (1/8760 yr/hr = 7.7E-09/d The ranges of .0000000077 and .00000000043 are such low occurrence events that for practical purposes the difference between the two (7.3E-09) is not significant. A similar argument and low frequency of occurrence can be demonstrated for the feedline break scenario.

B) If an MFIV becomes inoperable and is open, the present Technical Specification Section 3/4.7.1.6 allows operations to continue for only four (4) hours prior to proceeding to HOT STANDBY.

As stated in NUREG 1024, Tech Spec allowable outage times for inoperable equipment have been established on the basis of engineering judgment considering the use of standard intervals (e.g. 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, etc.). It is also stated that

ATTACHMENT 2 Page 3 of 3 outage times that are too short can result in unnecessary plant trips, transients and fatigue cycling.

The proposed 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowable outage time for an inoperable, open MFIV is consistent with the standard time interval selected for other safeguards systems. For example, with an inoperable Emergency Core Cooling System (ECCS) subsystem, Section 3/4.5.2 allows operations to continue for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> while the redundant subsystem is restored to OPERABLE. Similar situations exist with the Containment Spray Systems (Section 3/4.6.2) Containment Fan Coolers (Section 3/4.6.2.3), Intake Cooling System (Section 3/4.7.4) and Component Cooling Water System (Section 3/4 '.3).

In each case, the above systems have redundant subsystems and the ACTION time in each Tech Spec allows operations to continue for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> while an inoperable subsystem is restored to OPERABLE. Also, the MFIVs function as a portion of the flow boundary of the AFW and the proposed change is consistent with the AFW Tech Spec ACTION TIME (Section 3/4.7.1.2) given a single inoperable component in redundant trains. Thus, an extension of the MFIV ACTION TIME TO 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> provides the same time to repair an inoperable subsystem as other safeguards systems.

ATTACHMENT3 DETERMINATIONOF NO SIGNIFICANT HAZARDS CONSIDERATION The standards used to arrive at a determination that a request for amendment involves no significant hazards consideration are included in the Commission's regulations, IO CFR 50.92, which states that no significant hazards considerations are involved if the operation of the facility in accordance with the proposed amendment would not (I) involve a significant increase in the probability or consequences of an accident previously evaluated; or (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. Each standard is discussed as follows:

(I) Operation of the facility in accordance with the proposed amendment would not involve a significant increase in the probability or consequences of an accident previously evaluated.

The proposed 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> ACTION statement with an inoperable Main Feedwater Isolation Valve (MFIV) is consistent with other safeguards equipment outage times. The likelihood of a feedline or steamline break with a concurrent failure of the second valve in the same feedline is remote during the outage time. Thus, the proposed 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowable outage time will not significantly increase the probability or consequences of an accident previously evaluated.

(2) Use of the modified specification would not create the possibility of a new or different kind of accident from any accident previously evaluated.

This change will not create the possibility of a new or different kind of accident from any previously analyzed because it does not introduce a new mode of normal or emergency plant operation. In addition the proposed change does not involve a physical modification to the plant.

(3) Use of the modified specification would not involve a significant reduction in a margin of safety.

Because failure of the second MFIV in the same feedline with a simultaneous feedline or steamline break during the seventy-two (72) hour al lowable outage time is unlikely, this change does not involve a significant reduction in a margin of safety.

Based on the above, we have determined that the amendment request does not (I) involve a significant increase in the probability or consequences of an accident previously evaluated, (2) create the probability of a new or different kind of accident from any accident previously evaluated, or (3) involve a significant reduction in a margin of safety; and therefore does not involve a significant hazards consideration.

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