ML20101A816

TS Change Request NPF-38-123 to License NPF-38,modifying TS 4.7.1.5 Re MSIVs & Table 3.3-5, ESF Response Time. Change Proposed to Reduce Stress on MSIVs Due to Fast Closure

ML20101A816
Person / Time
Site:	Waterford
Issue date:	04/24/1992
From:	Barkhurst R ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20101A820	List: ML20101A816 ML20101A822
References
W3F192-0020, W3F192-20, NUDOCS 9204300373
Download: ML20101A816 (10)

Text

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W3F192-0020 A4.05 QA April 24, 1992 U.S. Nuclear Regulatory Commission ATTH: Document Control Dosk Washington, D.C. 20555

Subject:

Waterford 3 SES Docket No. 50-382 i

License No. NPP-38 Technical Specification Ch.nge Reglest NPP-38-123 4

Gentlemen Entergy Operations, Incorporated requests a modification to Waterford 3 ' technical Specification 4.7.1.5, " Main Steam Isolation Velves", Surveillance Requirements and Table 3.3-5, " Engineered Salety Features Responne Time".

This change is proposed to reduce stress on the Main Steam W Isolation valves (dsIVs) due to fast closure (i.e., a maximum of 3.0 seconds) . We feel that this site specific change will help preclude probleus experj enced in the past which in part were due to high atress subjected to MSIV's during surveillance testing.

The attached description and safety analysis provides assurance that the currcnt limiting enalyses presented in the Watecford 3 Final Safety Analysis Report are suf ficiently conservative to boun3 a 4.0 second MSIV closure time combiner! with a. 1.0 Second delay.

A plant modification necessary to support the changes identified 6* ' heroin is currently planned for refue '.ing outage number five which is scheduled to begin September 1992. However, this action is depundent _ epon your approval within an appropriate time frame.

Therefore, Entergy Operations Incorporated, respectfully requests a time 3r review.

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, U.S. Nutdoar Regulatory Commissj on Technichi Specification Change Request HPP '18-123 W3F192-0020 Page 2 April 24, 1992 Entergy operations, .t r c . fenic those plant specific changen would result in improvod reliability and plant safety. Please direct any questions or ocamer.Lc to Paul Caropino at (504) 739-6692.

I very truly yours, 1 V h. ML' C RPD/ PLC/dc

Attachment:

Affidavit NPF-38-123 cc: R.D, Martin, NRC Region IV D.L. Wigginton, NRC-NRR R.B. McGahee N.S. Reynolds NRC Resident Inspectors Office Administrator Radiation Protection Division (State of Louisiana)

American Nuclne Insurers o

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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the matter of )

)

Entergy Operations, Incorporated ) Docket No. 50-382 Waterford 3 Steam Electric Station )

1 AFFIDAVIT I

R.P. Barkhurst, being duly sworn, hereby deposes and nya that ho )

is Vice President Operations - Waterford 3 of Entergy Operatior.s, Incterporated; that he is duly authorized to sign and file with the  !

Nuclear Regulatory Commission the attached Technical Specification Change Request NPF-38-123; that he As familiar vith the content thereof; and that tha mattern set forth therein are true and correct to the best of his knowledge, information and belief.

45J\ AAA$ -

R.P. Barkhurat Vice President Operations - Waterford 3 STATE OF LOUISIANA )

) sa PARISH OF ST. CERLES )

Subscribed and sworn to before me, a Notary Public in and for the Parish and State above named thia 'L 4 " day of APRIL , 1992.

YG u .s Notary Public My Commission expires' W** M .

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DESCRIPTION AMD SAFETY AMALYsIs

. OF-PROPOSED CHANGE MPF-38-123 This proposal justifies a change to Waterford 3 Technical specification 4.7.1.5, " Main steam Isolation valves,H surveillanoc Requirements and Table 3.3-58 Engineered safety Features Response Time.

1 Existina specification see Attachment A Proposed specification see Attachment B Description The proposed change revises surveillance requirement 4.7.1.5 of Technical specification 3.7.1.5, Main steam Isolation valver (MsIVs).- This specification requires the plant _to _ demonstrate the-operability of each M8IV by verifying the operation and full ,

closure of each M8IV.within three seconds when tested pursuant to 1 specification 4.0.5.- The-proposed change revises the full closure time from three to four seconds. - This change -is proposed to reduce the stress on the MsIV due to fast closure during surveillance testing.

MsIVs isolate the steam generators (80) from one another and the ramaining portions of the secondary system in response to a variety of transients and postulated noidents, e.g., main steam line break. . The MsIV: closure time' is an important : parameter in

- calculating the consequences of an event which involves MsIV

. closure.: closure cimo affects 50- inventory, primary system cooldown rate, . peak containment. temperature and' pressure and secondary system inventory release to the. environment.

The limiting analyses for the MsIV olosure time - are the FSAR section 5.s Main. steam Line Break (MsLB) analyses performed to determine the , containment paak temperature and pressure. MsLB discharges . steam generator secondary. inventory into the

. containment. Refere the MsIV closes-- both - sGs feed the break through the cross connect _ pipe. MsIV. closure isolates the intact >

SG,-thereby limiting. release of mass and energy into containment.

- The existing analyses (Fs&R' section . 6.s Main l steum Line Break) assume- that the MsIV remains fully. open ..and- then closes' .

instantaneously three seconds after receiving a signal to close.

The resulting mass:and energy release to containment were used to determine peak'. containment pressure and temperature.

ABB/CE has reanalysed the-mass and energy released to containment-  !

for the three most limiting, in: terms of peak containment tamperature and; pressure, M8LB cases with a-longer (four seconds) 1-

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MSIV cloouro tino. Thoso analynos uoo o coro dotniled representation of the steam line piping and pressure drop from 80 to MBIV. In addition, more realistic MSIV closure characteristics wJre used. Instead of an instantaneous closure, the HSIV flow area was decreased as shown in Figure 1.

Table i shows the results for mass and energy release for the existing MBLB analyses and for the revised four second MSIV closure i time. For all cases the revised more realistic mass and energy release with a four second closure time is less than that used for j current peak containment pressure and temperature analyses in tha l FDAR. An analysis of containment peak pressure and temperature using the revised mass and energy would result in lower peak j values. Therefore, the current MsLB analyses in the PBAR conservatively bound the peak containment pressure and tamperature that would be calculated with the revised four seconda MSIV l closure time.

l MBIV closure time is also important for several events analyzed in FDAR Chapter 15. These analyses can be categorized into two groups bassed on the assumed MSIV closure time being greater than or less I

than four seconds. The events analysed with a MSIV closure time l greater than four socords and therefore not affected by this change ares (1) Full Power Double Ended Steam Line Break (BLB) Inside Containment With Concur.ent Loss of Offsite Power, (2) Double Ended BLB Inside and outside Containident During Mode 3 Operation With concurrent Loss of offsite Power, and (3) Steam System Piping Failures Pre-Trip Power Excursion Analysis Outside Containment With Loss of Offsite Power. The analyses that use lawe than a four second MSIV closure time, are discussed belows

1. Increased Main Steam Flow Due To Fail Open of Cne Turbine Bypass Valve (FSAR Section 15.1.1.1)1 This transient causes increased steam flow and, in turn, excess heat removal from the reactor coolant system (RCs).

The excess haat removal reduces RCS temperature and pressure, and increases core power due to a negative moderator l temperature coefficient (MTC).

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, The increase in core power decreases DNBR such that at 18.2 l

seconds after the initiating event, a low DNBR reactor trip signal is generated. At 255.2 seconds the low SG pressure generates a main steam isolation signal (MBIS) which closes the MBIVs three seconds later.

In this transient, the MSIV closure occurs long af ter the time of interest for this event, i.e., minimum DNDR and reactor trip. Therefore, increasing the closure time from three to four seconds will not affect plant response. The impact of this change on the radiological consequences of this event is expected to be negligible since the mass flow through the MSIVs is released to the condenser and is not directly released to the anvironment.

2. A Steam Line Break At Hot Hero Power Outside containment With Concurrent Loss of Offsite Power (FSAR Section 15.1.3) 2

In thic trancient tho main otcan lino rupturco upotreaa of M81V shortly af ter a shutdown from fitll power operation. This transient causes a large SG mass release and radiological consequences. However, the consequenose of this event are bounded by the full power r;eam piping failure event outside containment Pre-Trip Pow 6r Excursion With Loss of Offsite Power (FDAR Section 15.1.3.3). This latter event is analysed with an MSIV closure time of almost il seconds, which bounds the four second closure time.

3. Feedwater System Pipe Draak With Loss of Offsite Power (FBAR 15.2.3.1):

This transient causes critical flow of saturaten liquid from the affected BG through the break and instantaneous loss of feedwater to the intact 80. This causes a gradual heatup of )

the primary and secondary system >s. The ruptured steam generator empties and this causes a rapid increase in RCS temperature and pressure. At 15.4 seconds into the transient a high pressuriser pressure trip condition is reached.

The primary concern about the consequences of this transient is the Rc8 peak pressure which occurs due to the loss of best sink and loss of reactor coolant pump flow. An increase in MsIV closure time increases the primary and secondary systems temperature difference which, in turn, causes higher primary system cooldown rate and lower peak prussure. Therefore, increasing the 48IV olosure time from three to four seconds will not adversely af fect the consequences of this transient.

4. Loss of Normal Feedwater Flow With an Active Failure In Tha Steam Bypass System (FDAR 8ection 15.2.3.2):

The loss of feedvater flow increases SG pressure and tamperature. This opens the turbine bypass valves and increases steam flow and Rc8 cool down rate. The bypass control valves fail to close even in ths presence of closure signal. The cooldown of the primary system onuses core power to increase due to negat.ive MTc. The heat flux increases to its maximum possible value before the reactor trips at 42.6 seconds on low SG water level. At 77.3 seconds a MSIS is generated due to low SG pressure, which causes MSIVs to close three seconds inter.

changing the MDIV olosure time from three to four seconds will I not affect the transient results in terms oft (1) core damage due to high heat flux and (2) radiological consequences. This is because (1) MSIV olosure occurs long af ter the timing c4 the maximum heat fMx in the core and reactor trip and (2) the secondary mass release through t.he MSIV is not dischs.rged to the environment. The extra one second flow through MSIV however, causes a slight reduction in Rc8 temperature which will have a negligible effect on the course of the transient.

5. Bingle Reactor coolant Pump Shaft Daisure With A Stuck Open Secondary Safaty Valve (FBAR Section 15.3.3.2):

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Thio trcnoient ocuoco o rapid roduction in coro coolent flow and an increase in core average temperature. The low DNDR signal generates a reactor trip signal at about one second into the transient. The main turbine trip and reduction in feedwater flow causos 80 pressure to increase khich, in turn, opens the 80 safety valves. It is assumed that one of the safety valves remains open throughout the transient. The steam flow through the valve reduces the pressure in the 80.

At about 700 seconds into the transient the low 80 pressure l generates a MSIS which causes the XBIV to close 3 seconds l later. closure of the MDIV isolates the intact 80 from l discharging steam through the affected 80 open safety valve. ,

changing the closure time fro.4 three to four secondst (1) will not have an effect on the primary system behavior since the minimum DNDR occurs long before MSIV closure and (2) the radiological consequences of the extra one second contribution of the intact 80 to safety valve flow is insignificant.

Safety Analynis The proposed change described above shall be doomed to involve a significant hazards consideration if there is a positive finding in any of the following arcast

1. w f *.a. the operation of the facility in accordance with these proposed, changes involve a significant increase in the probability or consequence of any accident previously ovaluated?

Responses No The limiting mass and energy released into containment for the longer M8IV closure time has been reanalyzed. Other previously analysed accidents that are af fmotad by this change have been reviewed. This change has no impact on probability of occurrence of these accidents. The consequences of this change are either bounded by current plant safety analyses or have a negligible impact. Therefore, this change does not increase the probability or consequence of any accident previously evaluated.

t 2. Will the operation of the facility in accordance with th7se l proposed changes create t he possibility of a new or dif ferent I kind of accident from any accident previously evaluated?

l Response: No The MSIVs close aut,ountically upon main steam isolation l signal. The proposed change increases the closure time from I three to four seconds. This change will not alter the '

function or operability of the MSIV. However, it may increase l the rCliability of the K9IV. Based on above discussion, this change does not create the possibility of a new or different kind of accident previously evalusto1.

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4 3. Cill tho cp0 ratio 3 of tho fccility in cccord0nco cith thoco proposed changes involve a significant reduction in the margin .

of safety? l Responses No Revised analyses for the events with greatest potential impact l dite to this change, show a decroare in mass and energy release into the containment from a MSLB. This would result in inver peak containment pressure and temperature values than currently presented in the FSAR. Thus the margin of safety would increase for these analyses. No other accident analyses or margine of safety are affected by this change.

The Commission has provided guidance concerning the application of standards for determining weather a significant hazards consideration exists by providing certain examples (48 FR 14870) of amendments that are considered not likely to involve significant hazards considerations. The changes identified in this submittal closely natch example (V).

n(v) A change which either may result in come increase to the probability or consequences of a previously-analysed accident or may reduce in some way a safety margin, but where the renuits of the change are clearly within all acceptance criteria with respect to the system or component specific in the Standard Review Plant for example, a change resulting from the application of a maall refineaant of a previously unsd calculational model or design methods" Bafety and Significant Hazard Determination Based on the above safety analysis, it is concluded thats (1) the proposed change does not constitute a significant hasards consideration as defined by 10 CFR 50.921 and (2) there is a reasonable assursuce that the haalth and safety of the public will not be endangered by the proposed changer and (3) this action will not result in a condition which significantly alters the impset of the station on the environment as described in the NRC Final Environmental Statement.

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Figure 1 Illustration of the MSIV linear Stem Stroke Rate Closure 1

4-sec Linear Stem Travel MSIV Rampdown 1-sec delay ofter trip & before closure

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Table 1 Comparison of Reanalysis and Case Results the WSES FSAR .

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I Energy Release to Mass release to Containment at End of r Containment at End of Blowdot.n for WSES-3.

Blowdown for WSES-3 (Btu) f1bm) ,

i Description of WSES 1-sec Delay WSES 1-sec Dalay

• Limiting Case - FSAR After Trip FSAR After Trip  !

Case -Followed by Cast. Followed by a 4-sec MSIV a 4-sec MSIV -

Closure-Case Closure Case

. -1 75%-Power MSLB Containment 2.431 E5 2.430 ES 291.444 h6 291.1 E6

" Cooling. Train Failure 102% Power.MSLB Containment - 2.273 E5 2.269 E5 272.685 E6 272.1 E6 .

-Cooling Train Failure 75% Pover MSLB Failure of'One 2.604 ES 2.565 ES 312.220 E6 306.4 E6

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