ML20206T715

Application for Amend to License NPF-18,changing Tech Specs to Modify Automatic Depressurization Sys for Specific Transients Not Producing High Drywell Pressure Signal,Per NUREG-0737,Item II.K.3.18.Fee Paid

ML20206T715
Person / Time
Site:	LaSalle
Issue date:	07/03/1986
From:	Allen C COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20206T723	List: ML20206T715 ML20206T752
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.18, TASK-TM 1838K, NUDOCS 8607080213
Download: ML20206T715 (8)

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- Commonwealth Edison 72 West Adams Street, Chicf go,Illinoi's

'#, ]'/ Address Reply to: Post Offico Box 767 V Chicago,!!!inois 60690-0767 July 3, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

LaSalle County Station Uait 2 Proposed Amendments to Technical Specification for. Facility Operating License NPF Modification of ADS Logic NRC Docket No 50-374 References (a): Unit 1 (NPF-ll) License Condition 2.c.(30)(1)

(b): Unit 2 (NPF-18) License Condition 2.c.(18)(d)

(c): SER, SSER #1, SSER #3, and SSER #5 II.K.3.18 Modificatin of Automatic Depressurization System Logic (d): H. R. Feffer letter to T. E. Watts dated September 29, 1983, ADS Logic - Technical Specification Modifications and Timer Settings (e): Modifications 1-1-84-36 and 1-2-84-69 (f): C. W. Schroeder letter to A. Schwencer dated September 30, 1982 - Modification of Automatic Depressurization System Logic (g): C. W. Schroeder letter to H. R. Denton dated July 1, 1983 - Modification of Automatic Depressurization System Logic (h): Original FSAR Appendix L.62.

(1): A. Schwencer letter to D. L. Farrar dated April 11, 1983 - Modification of Automatic Depressurization System Logic for LaSalle

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H. R. Denton July 3, 1986 l

(ji: UFSAR Section 15.6.4, Steam System Pipe Break i-Outside Containment '

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(k): UFSAR Sections 6.3.3.7.8, 6.3.5.2 and 7.3.1.1.1.2 l (1): C. W. Schroeder letter to A.-Schwencer dated March 9, 1982 - ADS Logic Modification and ATWS l

, (m): W. R. Butler letter to D. L. Farrar dated a November 1, 1985 approving Am. 29 to NPF-ll.

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Dear Mr. Denton:

i Pursuant to 10 CPR 50.59, comunonwealth Edison proposes to amend Appendix A, Technical Specification, to Facility Operating License NPF-18.

This amendment change is being submitted for your ststf's review and approval in accordance with one of the conditions contained in the license,

! reference (b).

Attachment A provides background and discussion. The proposed j change is enclosed in Attachment B. The attached change has received both On-Site and Off-Site review and approval. We have reviewed this amendment request and find that no significant hazards consideration exists. Our review is documented in Attachment C.-

i Commonwealth Edison is notifying the State of Illinois of our request for this amendment by transmitting a copy of this letter and its ,

l attachments to the designated State official.

This amendment is the same for Unit 2 as was approved for Unit 1 in reference (m).

Since the logic required by these proposed changes is not yet

installed for Unit 2, we request that this amendment become effective upon 1 startup following the first refueling outage of the unit. This effective date is consistent with the referenced license condition. 1 I

Please note that your approval of this change is required prior to.  ;

the installation of these modifications. In accordance with the <

requirements of 10 CPR 50.170, a fee remittance in the amount of $150.00 is enclosed.

} Please direct any questions you may have concerning this matter to 4

this office.

4 H. R. Denton July 3, 1985 . -

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Three (3) signed originals and thirty-seven (37) copies of this transmittal and its attachments are provided for your use.

Very truly yours,

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s C. M. Allen Nuclear Licensing Administrator Im Attachments A: Background and Discussion ,

B: Technical Specification Change to NPF-18 C: Evaluation of Significant Hazards Consideration cc: Region III Inspector - LSCS A. Bournia - NRR G. Wright - State of Ill SUBSCRIBED AND SWO to bef r y this O day of _ AUL - ,- , 1986 l AA o AAAA ^

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ATTACIWWNT A 1

TECHNICAL SPECIFICATION CHANGE REOUEST 3

LASALLE COUNTY STATION UNIT 2

SUBJECT:

Modification of the Automatic Depressurization System Logic 7

BACKGROUND: The automatic depressurization system-(ADS), through seven l safety / relief valves, functions'as a backup to the operation of  ;

j the high pressure coolant systems (feedwater, high pressure '

' core spray (HPCS), reactor core isolation cooling (RCIC) ) for protection against excessive fuel cladding heatup upon loss of coolant, over a range of steam or liquid line breaks inside the drywell. The ADS depressurizes the reactor vessel, allowing the operation of the low pressure coolant systems (condensate, low pressure core spray (LPCS), low pressure coolant injection (LPCI). The present ADS design is activated automatically upon coincident signals of low reactor water level, high drywell pressure and low pressure ECCS pumps running. A time delay of approximately 2 minutes after receipt of these signals allows time for the water level to be restored by the high pressure coolant systems prior to automatic blowdown (reference (k)).

For transient events which do not directly produce a high drywell pressure signal and are further degraded by a loss of-

] all high pressure coolant systems, adequate core cooling is

assured by manual depressurization of the reactor vessel. The ,

intent of NUREG 0737 item II.K.3.18 is to provide additional j assurance of adequate core cooling for these additional events.

Commonwealth Edison participated with the BWR Owners' Group to

evaluate possible ADS logic modifications. The results of f

these evaluations are documented in references (c) and (h). i The first submittal was based on a BWR Owner's Group study I which concluded that the intent of II.K.3.18 may be satisfied two ways: the ADS logic may be modified to automate depressurization for specific transients not producing a high drywell pressure signal, or the operator may-be given specific guidance and training for performing manual actions under

, degraded conditions. LaSalle procedures developed from generic j

Emergency Procedure Guidelines provide the above mentioned guidance.

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l The second submittal (reference (1)) addressed the_ relationship of ADS logic modifications to transient events and specifically reserved Commonwealth Edison's judgment on ATWS recovery as differing from-that discussed by the BWR Owners Group and the i reactor vendor. The third submittal (reference (f)) met the j requirements of the Unit 1 license condition (reference (a))

part 2.C.30.(1)(a) which required evaluation of the alternative design modifications as proposed by the BWR Owners' Group. In this submittal, Commonwealth Edison committed to modify the ADS l logic to bypass the high drywell pressure trip after a j sustained low water level -(level 1) signal and to add a manual bypass switch which could be used to inhibit the automatic depressurization system action if required.

Reference (i) provided the NRC finding that the proposed modifications were acceptable, provided the following:

1) Approval of the detail logic implementation.

2) A plant specific analysis must be provided to justify the bypass timer setting.

3) Technical Specifications must be provided for the bypass i timer and manual inhibit switch.

4) The use of the inhib _it switch must be addressed in the plant emergency procedures.

5 'r Installation on Unit 1 and Unit 2 rust be completed prior to startup following the first refueling outage for each

. unit.

Reference (g) was submitted to provide information addressing item 1 above. The present submitta1 provides the information needed to address items 2 and 3 above. This submittal also will meet the requirements of reference (b) item (i) which required submittal of final circuit diagrams and an analysis of

- the bypass timer time delays. prior to installation and provides l proposed Technical Specifications (Attachment B) to meet item (iii) of reference (b).

DISCUSSION Basis for the ADS timer setting.

The maximum-and minimum settings for the ADS logic drywell pressure bypass timer (DpBT) are determined based upon minimizing the operator-actions related to the ADS logic, minimizing the chance for l unintentional ADS, and limiting the impact on the design basis ECCS ' '

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The maximum setting is based upon the UFSAR calculation of the design-  ;

basis main steam line break outside primary containment. For this event, the HPCS is assumed to be unavailable (single worst failure) and the manual ADS is currently modeled at ten minutes after the event

.begins (reference (j)). Since this ADS logic modification further delays the ADS initiation for events where high drywell pressure does not occur, due to the 10 minutes required to bypass the high drywell i pressure signal after the RPV level reaches level 1, a revised calculation was performed. The design goal of this calculation was to i limit the PCT to approximately 1500*F so that this event doesn't become the limiting design basis accident (DBA) replacing the large LOCA. The analytical time setting for the DPBT acknowledges the standard ADS i initiation delay of 120 seconds in addition to the DPBT along with this PCT analytical limit of 1500*F.

The minimum DPBT setting acknowledges that the operator should not be unduly burdened by having to repeatedly reset the ADS logic initiation delay during an event with sustained high drywell pressure. The time delay should be long enough to enable the operator to stabilize RPV I water level near the top of the active fuel before he manually inhibits

! ADS with the inhibit switch that is also a part of this logic

modification. With this approach, the operator has the option during 1 the DPBT time interval of deciding to either manually inhibit ADS or i Prepare for RPV depressurization, depending upon whether the RPV water level is stabilized or whether it is decreasing, respectively.

Several assumptions were necessary with respect to operator actions and responsen in establishing the minimum time delay value:

1. Given an ATWS event from full power with MSIV closure (currently at 1.evel 2 but with ATWS-2A fix it is lowered to level 1), the water level would drop to just above the RPV level 1 setpoint and then increase due to HPCS initiation at level 2. Operator action is not expected until RPV water level is observed to be increasing. If the level has dropped below level 1, the ope'ator is expected to i allow the level to increase above level 1 before manually j controlling level back to the normal range. This would allow DPBT

to reset. Specific plant procedures on ADS will incorporate appropriate actions following the installation of the ADS logic i modification.

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2. Given a genuine ATWS event where MSIV closure occurs, the DPBT will start when water level decreases to level 1. Water level is manually controlled with HPCS per the Emergency Operating Procedures. A five minute interval is assumed adequately long for the operator to stabilize the RPV level using the Emergency Operating Procedures.

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3. Events, other than ATWS, having a persistent high drywell pressure, are less time constraining for operator response than is the ATWS event described in 2 above, hence also fall within the five minute stabilization interval-for level control.

The analytical limit for the maximum DPBT timer setting is set at 10 minutes (plus the existing 2 minute ADS initiation delay). Analysis Provided in reference (d) resulted in a nominal Technical Specification setting of 9 minutes with an allowable setting of 9.5 minutes. These nominal trip setpoints and allowable values are derived after taking setpoint drift, accuracy and calibration precision into account.- (5%

setpoint accuracy, 0.1 minute calibration error and 0.5 minute drift is assumed based on manufacturer information.)

l The proposed modification provides a bypass timer (9 minutes) which ,

initiates at reactor vessel level 1. An alarm indicates when this bypass. timer has started. After the set time delay the high drywell 3

pressure permissive is bypassed and the existing 105 second timer initiates. Another alarm indicates that this timer has started. After i l

i this time delay, as before, the ADS solenoids are energized provided

that at least one low pressure pump in that division is operating I (discharge pressure above normal standby). This will further automate the ADS system by providing automatic ADS initiation, if required, for events such as a break external to the drywell or a stuck-open.SRV.. The bypass timers automatically reset when the low water level signal clears

. or the reset button is depressed. In addition, a manual inhibit switch

is also included to allow the operator to inhibit ADS operation without i repeatedly pressing the reset pushbutton. An indicating light and an annunciator alert the operator of the inhibit condition.. The pressure

relief function and the manual ADS or. individual SRV control is not effected by this manual inhibit switch. This modification also allows j the operator to manually initiate ADS without the low pressure ECCS pumps in that division operating. This provides additional flexibility in the use of the Emergency Operating Procedures (BOP) where the operator, for example, is instructed to perform an " emergency depressurization" to prevent containment damage. Although individual SRV control is available, the current logic requires at least one ECCS pump to be operating in the same division to permit manual initiation of

! the ADS system via the manual initiation pushbuttons. The proposed j modification will facilitate implementation of the BOPS.

The seal-in feature has also been revised such that the seal-in occurs only if the final relays which energize the ADS solenoids are actually-4 energized. This eliminates the pcssibility of inadvertent depressuriza-i- tion of the RPV if a low pressure-ECCS pump is started and a previous seal-in has not been reset. Modification 1-2-84-69 (Unit 2) will be installed prior to startup after the first refueling outage as required by item 5 above and reference (b) item (1).

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i Revisions to procedures, including the BOPS, and the updated PSAR l (reference (k)) will be controlled as part of the modification process.

A revision to Action 34 of Technical Specification Table 3.3.3-1 is also included in this request. This' revision changes the word " valve" to

" trip system". Since this specification is concerned with the instrumentation which actuates the ADS system and not the ADS valves l i themselves, action C of specification 3.3.3 applies. This change is >

required to made these actions consistent. Technical Specification i 3.5.1 applies if an ADS valve (s) is inoperable. To clarify the distinction between ADS Valve and ADS trip system footnote ** has been added to specification 3.S.1 to refer the Technical Specification user to Specification 3.3.3 if an ADS trip system is inoperable. If an ADS valve is operable but an ADS trip system is inoperable, the ADS valves required for specification 3.5.1 are operable and the action of specification 3.3.3 applies. This change does not effect the intent of l the present specifications.

This Technical Specification amendment must not be made effective until I the Unit 2 first refueling outage since operation with the present ADS design is not possible under the revised Technical Specification.

Revised Technical Specification pages are provided as Attachment B.

These pages reflect the requirements and setpoints as described herein.

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