ML20058C303

Proposed Tech Specs Changing LTOP of Reactor Vessel

ML20058C303
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	11/19/1993
From:	COMMONWEALTH EDISON CO.
To:
Shared Package
ML20058C297	List: ML20058C295 ML20058C303
References
NUDOCS 9312020414
Download: ML20058C303 (13)

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ZION NUCLEAR GENERATING STATION MARKED UP TECHNICAL SPECIFICATION PAGES FOR PROPOSED CHANGES TO APPENDIX A TECHNICAL SPECIFICATIONS i

FACILITY OPERATING LICENSES DPR-39 AND DPR-48 LICENSE AMENDMENT REQUEST 93-12 LOW TEMPERATURE OVERPRESSURE PROTECTION SETPOINT CHANGE

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SURVEILLANCE REQUIREHENT LIMITING CONDITION FOR OPERATION 4.3.2.G. Low Temperature Overpressure Protection 3.3.2.G.

Low Temperature Overpressure Protection 1.

Surveillance and testing of the low 1.

At least one of the following low temperature overpre ure protection temperature protection methods shall be methods shall be performed as follows:

svallable:

a.

Each PORV shall be demonstrated as Two power operate 6 relief valves a.

OPERABLE by:

(PORVs) with a lift setting of-435--

psig shall be OPERABLE, or aus.cr 1.

Perforwence of a CHANNEL FUNCTIONAL TEST on the PORY g

I actuation channel within 31 days prior to entering a condition in which the PORV is required OPERABLE, and at least once per 31 days thereafter when the PORV is required OPERABLE.

2.

Verifying the PORV backup air supply is charged, 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.

3.

Performance of a CHANNEL CAllBRATION on the PORV actuation channel at least once per refueling outage.

12470/12400 B2 Amenoment Mos. 110 " 00

A ne, 4 HN seipoint value is based on op cc ation gpf up +o 15 E F PY and a PoPN s t co k e +;.w e oP ecfval +o 3.4 seconds.

less wan or

.MM Bases:

Low Temperature Overpressure Protection N5 8 R.T 3.2.2 G There are 3 means of protecting the RCS from verpressu ization by a pressure transient at low temperatures (below 250*F). The first type of protection s ensured y the operation and surveillance of the power lift setting of psig.

A single power operated relief valve (PORV) will operated relief va'ves with a 4.2.2.G relieve a pressure transient caused by 1) a mass addition into a solid RCS from a charging pump or 2) a heat input based on a reactor coolant pump being started in an idle RCS and circulating water into a steam generator whose temperature is 50'F greater than the RCS temperature.

(1)

The second means of protection is ensured by a PORV being open.

11 will have the same relieving capabilities as mentioned above.

The third means of protection limits the pressurizer level to 25% and the pressurizer pressure to 100 psig.

A pressure transient caused by the inadvertent mass addition from a charging pump running for 10 minutes will be relieved by the large gas volume and iow pressure present in the pressurizer as mentioned above.

Maintaining the pressurizer level below 25% will also make the h1 pressurizer level deviation alarm available to the operator during a mass addition accident.

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In the event that a single PORY becomes inoperable, the repair period of 7 days is based on allowing

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sufficient time to effect repairs using safe and proper procedures and upon the operability of the redundant 6

PORV. The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> time period to reach the restrictive canditions in the pressurizer provides sufficient time to meet these conditions.

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In the event that both PORV's become inoperable, the condition is more serious than for a single inoperable PORV, therefore every attempt should be made to depressurtre the RCS in a controlled manner as rapidly as l7 possible. The 16 hour1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> time period to reach the restrictive conditions in the pressurizer represents a reasonable amount of time to meet these conditions under an expedited circumstance.

The Low Temperature Overpressure Protection System must be tested on a periodic bases consistent with the

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need for its use. A CHANNEL FUNCTIONAL TEST shall be performed prior to enabling the overpressure protection system during cooldown and startuD.

The limitations and surveillance requirements on the ECCS equipment provides assurance that a mass addition pressure transient can be relieved by the operation of a single PORV or the limiting conditions placed on the pressurizer.

The restrictions for startup of a RCP limits the heat input accident to within the relieving capabilities of a single PORV.

(1)

Pressure Mitigating Systems Transient Analysis Results July 1977 Westinghouse Owners Group on RCS Overpressurization.

12470/1247b 94 Amendment Nos ??9 i ^^

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i ATTACHMENT C ZION NUCLEAR GENERATING STATION EVALUATION OF SIGNIFICANT HAZARDS CONSIDERATIONS FOR PROPOSED CHANGES TO APPENDIX A TECHNICAL SPECIFICATIONS FhCILITY OPERATING LICENSES i

DPR-39 AND DPR-48 LICENSE AMENDMENT REQUEST 93-12 LOW TEMPERATURE OVERPRESSURE PROTECTION SETPOINT CHANGE i

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l Commonwealth Edison Company has evaluated the proposed changes j

associated with this License Amendment Request and determined that they involve no significant hazards considerations. According to

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10CFR50. 92 ( c). a proposed-amendment to an operating license involves no significant hazards considerations if operation of the facility-in accordance with the proposed amendment would not.

1.

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.

The proposed Amendment revises requirements as.sociated with the-Power Operated Relief Valve (PORV)

Low Temperature Overpressure i

Protection (LTOP) actuation setpoint. Specifically, this amendment i

changes the PORV actuation setpoint from'435 psig to s414 psig.

1.

The proposed Technical Specification change does not involve a significant increase in the probability or consequences of an accident previously evaluated.

The LTOP PORV actuation setpoint is not assumed. to de an initiator of any analyzed event.

However, pressure and l

temperature limits do preclude operation in an unanalyzed i

condition. The revised limitations provide an increase' level of protection to the previous limitations.

Revising the LTOP

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setpoint specification from 435 psig to less than or equal to i

414 psig will allow the incorporation of correction f actors into the PORV actuation setpoint and will result in' LTOP System actuation at a' pressure below that assumed in the LTOP transient analyses. A lower setpoint which includes correction factors i

associated with the RCS pressure transmitter locations and

_l Reactor Coolant Pump (RCP) and Residual Heat Removal (RHR) pump i

operation is more conservative. The incorporation of correction factors into the 'setpoint calculations has no impact on any event precursor. Therefore, the proposed amendment will' not

.significantly increase the probability of any accident previously evaluated.

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Reactor vessel integrity is assumed in mitigating the con equences of design basis-accidents. The revised limitations

.l wil not affect the performance of any safety systems. or structures beyond ensuring the continued integrity of-the reactor vessel. The amendment will allow.the setpoints ' to be conservatively reduced based on engineering calculations. which k : / 3 2 dr-sem. w;d /10

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incorporate the correction factors associated with the RC'S i

pressure transmitter locations and RCP and.RHR pump operation l

and will continue to ensure that the pressure-temperature limits i

of 10CFR50 Appendix G are met. Therefore, the change to the LTOP j

PORV actuation setpoint does not result in a significant increase in the consequences of any accident-previously evaluated.

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The proposed amendment does not change the actions required in the event of an LTOP system actuation or if the.LTOP l

Specification requirements can not be met. Any changes to the j

PORV actuation setpoint will be in accordance with the'"LTOP PORV Actuation Setpoint Methodology" and will be implemented per the requirements of 10CFR50.59. This will ensure that future changes to the LTOP PORV actuation setpoint will not involve a significant increase in the probability or consequences of an i

accident previously evaluated.

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2.

The proposed changes do not create the possibility of a new or i

different kind of accident from any accident previously evaluated.

j The change does not involve the addition of any new or dif ferent type of equipment, nor does it involve the operation 'of equipment required for safe operation of the facility in a a

manner different from those addressed in the Final Safety 1

Analysis Report. No safety related equipment or safety function i

will be altered as a result of this proposed change.

The amendment will allow the LTOP setpoints to be conservatively reduced based on engineering calculations which incorporate the correction factors associated with.RCS. pressure transmitter locations and RCP and RHR pump operation and will continue to f

ensure that the pressure-temperature limits of 10CFR50 Appendix i

G are met.

The change will result in more. conservative protective actions in the event of-an overpressure transient at

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low mperature. The proposed change does not af fect the actions.

t requ2 red in the event of an LTOP system actuation, nor does it affect the required. actions in the event-that the LTOP Specification can not be met.

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LTOP setpoint calculations will be performed using established engineering practices consistent with the - LTOP PORV actuation!

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setpoint methodology. Changes to ' the LTOP 'setpoints will be-1 evaluated in accordance with 10CFR50.59 to assure that operation of the facility in accordance with the new setpoints will not'

-l create the possibility 'of a new or diff erent kind of accident.

-l from any accident previously evaluated.

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The proposed changes do not involve a significant reduction in a margin'of safety.

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The amendment will allow the LTOP setpoints to be ' conservatively

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reduced based on engineering calculations which incorporate the correction factors associated with the RCS pressure transmitter locations and RCP and RHR pump operation and will continue to l

ensure that the pressure-temperature-limits of 10CFR50 Appendix

l G are met in the event of a low temperature overpressure transient. Reducing.the setpoints to incorporate the correction f actors will provide an increase level of protection to'that i

which currently exists and will not adversely affect the margin of safety.

'l LTOP setpoint calculations will be. performed using established i

engineering practices and consistent with the LTOP 'PORV' actuation setpoint methodology. Changes to'the.;LTOP setpoints l

will be evaluated in accordance with 10CFR50.59 to assure that-1 operation of the facility in accordance with the new setpoints will not involve a significant reduction in a margin of safety.

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ATTACHMENT D ZION NUCLEAR GENERATING STATION 3

ENVIRONMENTAL ASSESSMENT STATEMENT FOR PROPOSED CHANGES TO APPENDIX A TECHNICAL SPECIFICATIONS FACILITY OPERATING LICENSES DPR-39 AND DPR-48 l

LICENSE AMENDMENT REQUEST 93-12 LOW TEMPERATURE OVERPRESSURE PROTECTION SETPOINT CHANGE

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The proposed changes of this license amendment request have been i

evaluated against the criteria for and identification of licensing and regulatory actions requiring environmental assessment in accordance with 10CFR51.21. It has been determined that the proposed changes meet i

the criteria for categorical exclusion as provided for under

-I 10CFR51.22 (c) (9). The following is a discussion of how the-proposed changes meet the criteria for categorical exclusion:

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10CFR 51.22 (c) (9) : Although the proposed changes involve changes to I

the installation or use of f acility components or to Surveillcince Requirements; I

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The proposed changes involve no significant hazards t

considerations

.(refer to the significant hazards consideration section of this license imendment request).

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(ii)

There is no significant change'in the types or significant

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increase in the amounts of any effluents that may be i

released offsite, since the proposed changes do not affect i

the generation of any radioactive effluent nor do they l

j affect any of the permitted release paths.

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!iii)

There is no significant increase in individual or cumulative j

occupational radiation exposure.

Accordinaly, the proposed changes meet the eligibility criteria for j

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categori cal exclusion set forth in 10CFR51.22 (c) (9).

Based on the

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foremeationed and pursuant to 10CFR51.22(b),

no environmental assessment or environmental impact ' statement need be prepared in connection with issuance of a license amendment incorporating these proposed changes.

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i ATTACHMENT E i

ZION NUCLEAR GENERATING STATION LTOP PORV ACTUATION SETPOINT METHODOLOGY LICENSE AMENDMENT REQUEST 93-12 l

LOW TEMPERATURE OVERPRESSURE PROTECTION SETPOINT CHANGE f

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i The purpose of this document is to describe acceptable means' of determining the Low Temperature Overpressure Protection (LTOP).

i setpoints for the Zion PORVs.

In addition to describing basic j

methodology, conditions which require re-analysis are described to' facilitate identification of the need for such re-analysis in order to ensure continued operation within analyzed regions.

l Methodoloav:

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The LTOP system is designed to prevent inadvertent operation above the steady-state Appendix G curve as a result of a mass or heat injection transient.

Zion Technical Specifications require a means of low temperature overpressure protection whenever the plant is in modes 4.

(below T

), 5, and 6 (with the vessel head on).

The. requirement for installation of this system in PWRS arose as a result of nur.erous 2

overpressure events that occurred during solid plant operation.

Consistent with current and historical methodology, the performance of the LTOP system should be evaluated based on plant response to_ two 1

design basis events :

1.The pressure transient resulting f rom spurious isolation of letdown (RHR) concurrent with charging flow control. failed to full flow (a single centrifugal charging pump supplying flow).

2..The pressure transient resulting from the start of a reactor

-i coolant pump with the steam generator secondary side water at a i

temperature 50 F higher than the NSSS loop and vessel water.

1 The c

.at Westinghouse methodology, accepted by CECO, involves the l

use of an LTOP version of the LOFTRAN code to determine the PORV

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pressure overshoot (the difference between a setpoint pressure and

.i peak RCS pressure) during the assumed transients. This information is then used to determine a maximum setpoint pressure such that the-current steady state Appendix G curve (without random pressure instrument uncertainties) is not exceeded. In effect, the-setpoint plus the PORV pressure overshoot. must not exceed the applicable Appendix G curve.

Instrumentation uncertainties are excluded in the LTOP Actuation.

i setpoint determination on the basis that these uncertainties terms are _

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insignificant when compared to the margin terms. included in the'ASME-j!

Section III Appendix G methodology. Specifically, the pressure stress is multiplied by a factor of two, resulting in conservative stress

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Because the operation of RCPs and RH pumps introduces uni-directional error in the non-conservative direction for the wide range pressure transmitters (PT-403 and 405 which sense RCS Hot Leg pressure), error k: /129xtp,wp f /16 J

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4 margins are calculated for the operation of these pumps in various ccmbinations. These error margins should then be applied to the.

calculations (either shifting the Appendix G curve down in pressure by the magnitude of the error, or by adding the error margin to the pressure overshoot determined in the LOFTRAN analysis) to. determine-a maximum setpoint for the pump combination considered.

In order to facilitate timely plant heatup and maintain a broad pressure band for plant operation, it may be desirable (and is acceptable) to perform the calculations to support the operation of only one RCP (plus necessary RH pumps) up to a given temperature where the margin between the setpoint plus PORV overshoot, and the applicable Appendix G curve, exceeds the pressure error margin attributable to the operation of two RCPs (plus required RH pumps).

This temperature then represents the minimum required temperature to-start the second RCP. Once two RCPs are operating, the necessary RCS temperature for drawing a bubble in the pressurizer should'be easily attained. This methodology can be utilized to determine a minimum required temperature for any given combination of RCP/RH pumps.

Factors Requiring Re-Analysis:

1 There are several input parameters to the LOFTRAN code that may change over the life of the plant.

When it is anticipated that such changes will occur, the LTOP setpoint analysis should be updated to reflect such changes.

The significant parameters (or factors) are listed below:

i 1)

RCS active volume I

2)

PORV stroke times -(the code uses a specified value/can be run for a variety of values, therefore the ISI acceptance criteria for PORV stroke time'must always be verified to be consistent with the analysis assumptions) 3)

PORV throttling characteristics (Cy )

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Pressure sensor signal delay times t

5)

Steam Generator Type /significant alteration (affecting

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heat transfer coefficient) i 6)

Centrifugal Charging Pump Curve.(Head vs. Flow) s 7)

Fuel Geometry (Core delta-Pressure) 3 i

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Additionally, as the Appendix G curve shif ts with increasing EFPY, the analysis must be updated.

Usually, the analysis is performed = to some

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future EFPY that is more than one fuel cycle away.

Because the operation of RCPs and RH pumps introduces pressure error, significant alteration to these pumps (affecting the Head vs. Flow characteristics) should also be considered for re-analysis.

i Note of Exolanation:

The Appendix G curves are calculated to specify the reactor vessel temperature and pressure combinations that minimize the probability of vessel failure.

The wide range pressure sensors that are utilized-to monitor RCS pressure relative to these curves sense pressure-on the Hot Legs of the RCS. More precisely, PT-405 senses pressure directly in the C Hot Leg, and PT-403 senses pressure on. the RHR suction piping l

Which in turn connects to the A Hot Leg. The specific location'of' interest with regard to the Appendix G curves is the reactor vessel beltline.

When reactor-coolant pumps are operating, a pressure' dif f erence is induced between the vessel beltline and the RCS hot legs as a result of the head loss between the' vessel beltline and the' hot.

legs. The magnitude of this pressure difference depends on the flowrate in the RCS (which in turn depends on the number of RCPs l

operating). Likewise, pressure sensed by PT-403 is af fected by RH pump i

operation.

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