ML20126E392

Forwards Clarifications to Tech Spec Bases Re Positive Reactivity Insertions & Reduction in RCS Boron Concentrations

ML20126E392
Person / Time
Site:	Wolf Creek
Issue date:	12/22/1992
From:	Hagan R WOLF CREEK NUCLEAR OPERATING CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20126E395	List: ML20126E392 ML20126E403
References
NA-92-0122, NA-92-122, NUDOCS 9212290114
Download: ML20126E392 (10)

Text

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LF CREEK W@ NUCLEAR OPERATING

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OL*E.s?OnT"es Assurance December 22,_1992 NA 92-0122' U.-S. Nuclear Regulatory Commission ATTN: Document Control Desk Mali Station F1-137 Washington, D. C.

20555

Subject:

Docket No. 50-482: Revision to_ Technical' Specification Bases Gentlemen:

This letter transmits several clarifications to the ' Wolf Creek Generating Station Technical Specification Bases.

Attachment I provides background information and justification for the changes.

Attachment II consists of affected Technical Specification' Bases'pages marked-up to show the clarification.

If you have any questions regarding the changes, please contact me at (316) 364-8831 Ext. 4553 or Mr. Kevin J. Moles of my staff at Ext. 4565.

l Very truly yours, And l

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/ Robert C. Hagan Vice President Nuclear Assurance RCH/jra Attachment I - Background and Justification Attachment II - Marked-Up. Bases Pages cci-G. W. Allen (KDHE), w/a A. T. Howell (NRC),w /a J. L. MilhoanL(NRC), w/a G. A. Pick (NRC),-w/a W. D. Reckley.(NRC), w/a SbhUdU PO. Box 4:1/ Durhngtor'. KS 66839 / Phone. (316) 364-8831 9212290114 921222 An Equal Ownttunity Employer M'FMC/ VET -

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PDR ADOCK 05000482 l-P P DR

STATF. OF KANSAS

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) SS COUNTY OF COFFEY

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Robert C. Hagan, of lawful age, being first duly sworn upon oath says that he is Vice President Nuclear Assurance of Wolf Creek Nuclear Operating Corporations that he has read the foregoing document and knows the content thereof; that he has executed that same for and on behalf of said Corporation with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief.

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Robert C. Hagan Vic6 President Nuclear Assurance SUBSCRIBED and sworn to before me this cad day of O CC -

1992.

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4 Attachment I to NA 92-0122 Page 1 of 8 BACKGROUND AND JUSTIFICATION FOR REVISION TO TECHNICAL SPECIFICATION BASES REGARDING POSITIVE REACTIVITY INSERTIONS AND REDUCTIONS IN RCS BORON CONCENTRATION-

1.0 INTRODUCTION

Several technical specification action statements require suspension of all operations involving positive reactivity changes whenever impairments occur to

1) systems and equipment required to mitigate boron dilution events, 2)-

equipment required to detect and mitigate reactivity addition accidents and transients, or 3) equipment required to mitigate the effects of an inadvertent criticality event.

Other action statements require suspension of all_ operations involving a reduction in boron concentration of the reactor coolant system (RCS) whenever insufficient coolant flow is available to adequately mix the coolant _ and promote gradual reactivity changes during the reduction.

A listing of the applicable action statements is provided in Table 1.

At times c'uring reactor shutdown evolutions, the RCs boron concentration may-be maintained very much greater than the minimum required.:

If plant conditions involve entering the action statement of one of the technical-(

specifications identified in Table 1,

any - addition of water - with a boron concentration less than the RCS would constitute a violation to technical specification requirements, i.e.,

it would result in a positive reactivity change or a reduction in RCS boron concentration.

A violation-would occur even though the boron concentration in the added water exceeds _the-concentration required to be maintained 3n the Refueling Water Storage Tank-(RWST) for mitigating boron dilution events and maintaining shutdown margins.

Therefore, a clarification is proposed to the bases-of the affected specifications to state that the addition of RWST water or equivalent -(i.e.

water with a minimum boron concentration equal to that of the RWST) is not considered to be either a positive reactivity change or a reduction in boron concentration.

Justification for this clarification is provided in - the following section.

2-0 EVALUATION The action statements in question prohibit evolutions that add positive reactivity or reduce the' boron concentration of the RCS.

Neither the_ action statements nor the corresponding Technical Specification Bases' provide quantitative limits or define -the safety ' margins available during these evolutions.

The proposed clarification to the bases would allow - reactivity additions or RCS boron concentration reductions as long as they were made within the quantitative limits defined by the RWST boron concentration.

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Attachment I to NA 92-0122 i

Page 2 of 8 i

The RWST limit for boron concentration (which is currently a minimum 1 of 2400 ppm) has been used to define safety margins as discussed in the bases to specifications 3/4.1.2, Boration Systems.

The RWST water, in the proper quantity, has been shown to provide the shutdown margin requirements of 1.3%

delta k/k for Mode 5.

(In Mode 6,_ _the limitations on reactivity are K gg no:

e greater than 0.95 or a boron concentration of at least 2000 ppm-whichever is more restrictive).

The RWST concentration has also been used to evaluate baron dilution ~ events in the Updated Safety Analysis Report (USAR) Section 15.4.6.

The boron dilution mitigating equipment, upon detecting a neutron flux doubling, alarms and automatica1,1y aligns the charging pump suction to the RWST.

Injection of_RWST water terminates the dilution event and regains lost shutdown margin.

I The RWST is also the main source of coolant that plant operators would rely on' to provide makeup to the RCS should an inadvertent draining of the RCS occur.

The operators should not be put in the position of deliberately violating-a technical specification while taking action to place the plant in a safe condition, 10 CFR 50.54(x) not withstanding.

The above discussion shows that the RWST, with its boron concentration maintained in accordance with specifications 3.1.2.5 and 3.1.2.6, will be the main source of RCS makeup regardless of the initial RCS _ boron concentration.

The addition of RWST water, or its equivalent, should not result in a violation of technical specification requirements.

With regard to the reduction in boron concentration.that could occur-as the-result of adding-RWST water or its equivalent, it should be noted -- that the RWST boron concentration is sufficient to. provide the. required shutdown margin.

If a pocket of coolant with RWST or equivalent boron ; concentration should accumulate in an-idle RCS loop and subsequently be swept 'into the reactor core, there is no danger of an inadvertent criticality even though a positive reactivity addition would occur.

Therefore, injecting RWST water,'or-equivalent, should not involve a violation of technical specifications.

The action statement for Technical Specification - 3.4.2.1 involves placing an RHR loop in o'peration in the shutdown cooling mode.

An implication of.this action is that a cooldown of the RCS may-be _ necessary -in order to return a l

code safety valv'e to an operable condition.

In this case, the proposed' revision to the technical specification bases includes a statement that the-RCS~cooldown, if it represents a positive reactivity change, for the purpose of' restoring valve operability is not considered to be a positive reactivity-addition provided that the RCS-has been borated to cold shutdown, Xenon-free conditions.

4 Attachment I to NA 92 0122 I

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Page 3 of 8 i

3.0 CONCLUSION

S Basedlon the evaluation above,;it is proposed that:

E 1.

The bases to Technical. Specifications 3/4.1.2, 3 / 4. 3.1, _ 3 / 4. 7. 6, _ 3 / 4. 8.1..

3/4.8.2, 3/4.8.3.

and.3/4.9.2 bel revised to add the statement,

'When-determining compliance with action statement requirements, addition to the'RCS-

- of borated water.with a concentration greater than or equal to the minimum-required RWST concentration shall not be considered to be a positive reactivity change."

Note - that: the clarification will not 'significantly impact Technical Specification 3.3.1 action 4, because this action applies in Mode 2, startup..

- and the critical baron concentration will be less than the-RWST concentration.

Therefore, ' adding 1 RWST. or equivalent water does - not - involve a positive

- reactivity change under these conditions.

2.

The bases to Technical Specification 3/4.4.1 and 3/4.9.8 he revised to add the statement:

' Addition of borated water with a: concentration greater than or equal to-the minimum required RWST-concentration but less than.the actual RCS boron concentration shall not be considered a reduction ~ in; boron concentration".

3.

The bases to

. Technical _ Specification-- 3/4.4.2 be revised to add the -

- statement, " Addition to the RCS of borated water with a concentration greater than or equal.to 'the minimum required RWST. concentrationi shall not be considered a positive reactivity _ change.- Cooldown of the RCS for-restoration of operability _ of c a pressurizer code ~ safety valve,.with a negative ' moderator temperature coefficient, shall not beLeonsidered a positive reactivity change provided _the RCS is borated to.the COLD SHUTDOWN. ; Xenon-free conditions per specification 3.1.1.2".

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Attachment I to NA 92-0122 page 4 of 8-TABLE 1 Action statements requiring the suspension of all operations that involve positive reactivity changes or a reduction in reactor coolant boron -

concentration.

3.1.2.1 Action -With none of' the above flow paths OPERABLE or _ capable of being powered from an OPERABLE emergency power source, suspend all operations involving CORE ALTERATIONS or positive reactivity changes.

(Mode 4,' 5, and 6)

Bases:

The Boration System ensures. that negative reactivity control is available during each mode of facility operation.

3.1.2.3 Action: With no centrifugal charging pump OPERABLE or capable of being powered from an OPERABLE emergency power source, suspend all operations involving CORE-ALTERATIONS or positive reactivity changes.

(Mode 4, 5, and 6)

Bases:

The Boration System ensures that negative reactivity control is available during each mode of facility

p operation.

3.1.2.5 Action: With no borated water source OPEkABLE, suspend all ope ra tions involving CORE -ALTERATIONS or positive reactivity changes.

(Modes 5 and 6) g Bases:

The Boration System ensures that negative reactivity control is available during each mode of facility operation.

3.3.1. Action

ACTION 4 - With the number of OPERABLE channels one less than the minimum channels OPERABLE requirements - suspend =

all operations involving Lpositive reactivity changes =

(applicable ' to source range, Neutron Flux during startup in Mode 2 below P-6).

ACTION 5 -

a.

With the number - of 0PERABLE channels one less--than the Minimum Channels OPERABLE requirement, restore the inoperable channel to OPERABLE status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> or open the Reactor ' Trip Breakers, suspend all operations ' involving positive reactivity changes and'

. verify valves BG-V178 and BG-V601 are closed and secured in position within the next hour, b.

With no channels OPERABLE, open the Reactor Trip Breakers, suspend all'

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4 At'tachment I to NA 92-0122 Page 5 of 8' operations involving. positive-reactivity: ' changes, and verify compliance with the SHUTDOWN. MARGIN. requirements of-specification 3.1.1.1 or 3.1.1.2, as applicable.- within l*

hour and every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> thereafter, and verify valves;BG-V178 and BG-V601 are closed and secured in position _within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and verified to be closed and-secured in position-every 14 days. (Applicable to' source range,' Neutron Flux -

during shutdown in Modes 3, 4, and 5)

Bases:

The OPERABILITY of these systems ois required to provide the overall-reliability, redundancy, and-diversity-assumed available in the facility design for. the - protection and mitigation-_of accident and transient' conditions. -

_(The.

source range detectors prevent and mitigate potential-reactivity addition events per USAR-Section 15.4) 3.4.1.2 Action: Vith no reactor coolant loops in operation, suspend : all operations involving a reduction in boron' concentration-of the Reactor Coolant System and immediately. initiate corrective action -to return the required - reactor Leoolant -

loops to operation.

(Mode 3)~

Bases:

The operation of one reactor coolant pump (RCP)'orEone RHR 1

pump provides adequate flow to ensure mixing, _ prevent stratification, and produce gradual-reactivity changes during-boron-concentration reductions Jin-the~ Reactor--

Coolant System.

The ' reactivity ; changeL rate _ associated with boron reduction will - therefore, be within : the---

capability of operator recognition and control.=

3.4.1.3 Actions-With no reactor coolant or1RHR. loop.in operation, suspend all operations-involvingL a

reduction' ' in '

boron-concentratior-of the Reactor _ Coolant system and; immediately, initiate corrective -action -to. return _the required coolant loop to operation. ~(Mode 4).

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Bases:

The operation of one_ reactor coolant pump (RCP) or one RER.

pump provides. adequate flev to Lensure. mixing.- prevent stratification. and produce gradual-reactivity changes during' boron concentration. : reductions in-the Reactor-Coolant-System.

The L reactivity change rate l associated -

with boron reduction will. -therefore, be-within the capability of operator recognition.and control.

3.4.1.4.1 Action: LWith no RHR - loop in operation, suspend all operations involving a-reduction-in boron concentration of the Reactor. Coolant System and immediately initiate-corrective action to return the require RHR loop to operation.

(Mode 5 with RCS loop filled) i w

Attachment I to NA 92-0122 Page 6 of 8 Baces:

The operation of one reactor coolant pump (RCP) or one RHR pump provide:: adequate flow to ensure mixing, prevent stratification and produce gradual reactivity changes during boron concentration reductions in the Reactor Coolant System.

The reactivity change rate associated with boron reduction, will, therefore, be w1 thin the capability of operator recognition and control.

3.4.1.4.2 Action: With no Ri!R loop in operation, suspend all operations involving a reduction in baron concentration of the Reactor Coolant System and immediately initiate correccive l

action to return the required RilR loop to operation.

(Mode 5 with RCS loops not filled)

Bases:

The operation of one reactor coolant pump (RCP) or one RilR pump provides adequate flow to ensure mixing, prevent stratification, and produce gradual reactivity changes during boron concentration reductions in the Reactor Coolant System.

The reactivity change rate associated with boron reduction will, therefore, be within the capability of operator recognition and control.

3.4.2.1 Action: With no pressurizer Code safety valve

OPERABLE, immediately suspend all operations involving positive reactivity changes and place an OPERABLE RilR loop into operation in the shutdown cooling mode.

(Modes 4 and 5)

Bases:

No bases are givent however, it can be assumed that the action statement is intended to avoid a pressurization of the RCS resulting from an inadvertent criticality and power surge.

3.7.6 Action

Vith both Control Room Emergency Ventilation Systems inoperable, or with the OPERABbE Control Room Emergency Ventilation System required to be in the recirculation mode by ACTION a.,

not capable of being powered by en OPERABLE emergency power source, suspend all operations involving CORE ALTERATIONS or positive reactivity changes.

(Mode 5 and 6)

Bases:

The OPERABILITY of the Control Room Emergency Ventilation System ensures thats (1)..., and (2) the control room will remain habitable for operations personnel during and z

following all credible accident conditions.

3.8.1.2 Action:

With less than the above minimum A.C.

electrical power sources

OPERABLE, immediately suspend all operations involving CORE ALTERATIONS, positive reactivity changes, movement of irradiated fuel, or crane operations with loads over the spent fuel pool.

In addition.... (Mode 5 s

and 6)

Attachment I to NA 92 0122 Page 7 of 8 4

4 Bases:

The bases for the action statement are not _ specifically statedt_however, it can be assumed that the intention is to avoid any accidents that 'could cause a release of radioactivity during the time that electrical power to a

monitoring and mitigating systems is impaired.

J 3.8.2.2 Action:

With the required battery bank and/or full capacity charger inoperable, immediately suspend all operations 1

involving CORE ALTERATIONS, positive reactivity changes, or movement of irradiated fuels... (Hode 5 and 6)

Bases:

The bases for the action statement are not specifically_

itated: however, it can be assumed that.the intention is a

to avoid any accidents that could cause a release. of radioactivity during the time that electrical power to monitoring and mitigating systems is impaired.

L 3.8.3.2 Actions Without one of the above required divisions of electrical-bussos energized in the required manner, immediately suspend all operations involving-CORE ALTERATIONS,-

positive reactivity changes. or movement of irradiated-fuelt... (Mode 5 and 6) l Bases:

The bases. for the action statement are not specifically stated, however, it can be assumed that theLintention is to avoid any accidents. that could.cause. a 1 release - of radioactivity during the time that electrical power-to monitoring and mitigating systems is'~1mpaired.-

3.9.1 Action

With the requirements of the above specifications-not

-j satisfied, immediately suspend all 'o'perations involving CORE ALTERATIONS or positive reactivity -changes and initiate and continue-boration at' greater than or equal.to 30 g[a of a. solution containing greater than or equal _to 7000 ppm boron or its equivalent until K egg is reduced to-0.95. or the boron concentration _is restored; to greater than or equal to 2000 ppm whichever is more restrictive.

-(Mode 6)

Bases:

The limitation on reactivity conditions during REFUELING:

ensures that: '

(1). the reactor : will. remain. suberitical:

during CORE ALTERATIONS, and

_(2) a uniform : boron

'1 concentration is maintained for reactivity control in'the-water volume having~ direct access to.the reactor _ vessel..

3.9.2 Actions.

With. one of.the above required ~ monitors inoperable or not operating, immediately suspend all ' operations involving CORE ALTERATIONS or-positive reactivity changes.

(Mode 6)-

-- r Bases:

The OPERABILITY of the' source range neutron flux-monitors ensures-that redundant monitoring _ capability _ is ' available to detect changes in the' reactivity condition of the core.-

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s Attacament I to NA 92-0122 Page 8 of 8 1

3.9.8.1 Action With no R11R loop OPERABLE and in operation, suspend all operations involving an increase in the_ reactor decay heat load, or a reduction in boron concentration of the reactor concentration of the reactor system and...(Hode 6 with >23 feet of water above the vessel flange) bases:

The requirement that at least one residual heat removal (Ri!R) loop be in operation ensures thats (1).... and (2) sufficient coolant circulation is maintained through.the.

core to minimize the effect of a boron dilution incident and prevent boron stratification.-

3.9.8.2 Action:

With no RilR loop in operation, suspend all opera tictv.

involving a reduction _in boron concentration ~of the Reactor Coolant System and immediately initiate corrective-action to (Mode 6 with <23 feet of water -above the vessel flange).

Bases:

The requirement that -at least one residual heat removal l

I (RifR) loop be in operation ensures thats (1)

.., and (2) sufficient coolant circulation is maintained through he -

t core to minimize the effect of a boron dilution incident and prevent boron stratification.

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