ML17158A120

Safety Evaluation Supporting Amend 100 to License NPF-22

ML17158A120
Person / Time
Site:	Susquehanna
Issue date:	01/31/1994
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML17158A119	List: ML17158A118 ML17158A120
References
NUDOCS 9402090236
Download: ML17158A120 (8)

Text

~C

~pg RE0y Vp0 Cy A

I O

pp 0

+>>*<<>>

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION 8 THE OFFICE OF NUCLEAR E

CTOR REGULATION RELATED TO AMENDMENT N0.100TO FACILITY OPERATING LICENSE NO. NPF-22 ENNSY VANIA POWER

& LIGHT COMPA Y

A~LE EIIEAT E TRI I RATIIIE I E.

SUS UEHANNA STEAM ELECTRIC STATION UNIT 2 DOCKET NO. 50-388

1.0 INTRODUCTION

By letter dated January 24, 1994, the Pennsylvania Power and Light Company (PP&L or the licensee) submitted a request for changes to the Susquehanna Steam Electric Station (SSES),

Unit 2, Technical Specifications (TS).

The requested changes would modify the applicability requirements of Sections 3.0.4, 4.0.4, 3.3.7.5 Action 80, 4.3.7.5, 3.4.2 Action c, and 4.4.2 of the TSs to permit Unit 2 to continue to operate with the acoustic monitor on the "S" safety/relief valve (SRV) tailpipe i'noperable.

On January 21, 1994, the licensee verbally requested and the NRC orally granted a request to exercise discretionary enforcement from the above applicability requirements of the TSs.

The licensee documented the request by letter of January 24, 1994.

The NRC confirmed that the request to exercise discretionary enforcement had been granted by letter of January 27, 1994.

By letter of January 24, 1994, the licensee also submitted an emergency request for revisions to the TSs to effect the changes approved in the notice of enforcement discretion.

2.0 EVALUATION The reason PP&L requested enforcement discretion and changes to the TSs is described in both their letters of January 24,

1994, and in the NRC's notice of January 27, 1994.

The accident at TMI-2 was initiated by a stuck-open pilot operated relief valve (PORV).

Prior to the accident, both PWRs and BWRs included temperature monitoring instrumentation on the discharge tailpipes from any relief valves to detect weeping, cycling, or stuck-open valves.

One of the many NUREG-0737 requirements was that licensees install a second diverse means on the tailpipes to detect an open relief valve.

Considering what was most readily available, almost all licensees installed acoustic monitors as the second means of detecting flow in the line.

The requirement to have the acoustic monitor on each discharge line operable while at power was incorporated in the TSs.

In the new Improved Standard Technical Specifications

("Standard

(

9402090236 940i3i PDR ADOCK,05000388

,. P ~,'

',,"PDR-

Technical Specifications, General Electric Plants, BWR/4," NUREG-1433, issued September 1992),

the requirement to have either the temperature sensors nr acoustic monitors operable was deleted from Table 3.3.3.1-1 (Page 3.3-25) of the accident monitoring instrumentation that is required to be operable.

As described in the Susquehanna Steam Electric Station Final Safety Analysis

Report, the safety/relief valve position indication system is a safety grade

system, indicated and alarmed on a control room panel, and powered from a Class lE'vital instrument bus.

Also, backup methods of determining valve position are available and are discussed in the off normal procedures.

Specifically, off normal procedure ON-283-001, "Stuck Open Safety Relief Valve," Revision 12, dated March 16, 1993, provides a list of indications and symptoms for determining safety/relief valve position indication.

This off normal procedure is included as part of current operator training and has been trained on by the SSES Operators.

These alternate indications and symptoms are:

Suppression Pool Temperature Loss of Generator HWs Reactor Pressure Vessel Pressure Reactor Pressure Vessel Level Swell Suppression Pool Level Suppression Pool Pressure Indicated Feedwater Flow Greater Than Steam Flow The suppression pool temperature monitoring system (SPOTMOS) provides the operator with safety grade, redundant pool temperatur e information.

There are 16 temperature sensors in the system, with two in each location, each powered from a separate division.

These sensors are located in the upper levels of the suppression chamber.

There are also non-safety grade temperature elements located in the lower elevations of the pool to measure bulk-water temperature.

The reactor pressure vessel

pressure, reactor pressure vessel level swell and suppression pool level in'strumentation are used to satisfy the positions set forth in Regulatory Guide 1.97 and are safety grade systems.

The suppression pool level instrumentation is also safety grade.

For,the "S" SRV, Suppression Pool Temperature Elements TE 25757 thru 25761 are in proximity to the SRV discharge line quencher and would see an elevated temperature if the SRV were open.

Temperature Elements TE 25757,

25758, 25759, and 25760 are safety grade elements.

In addition, tail pipe temperature sensors also provide immediate indication if an SRV is open.

Thus, in addition to the temperature sensors on each SRV tailpipe, there are multiple other means that would alert the operators to a weeping, cycling, or stuck-open relief valve.

As a compensatory

measure, the licensee issued a Procedure Change Approval Form (PCAF) to procedure ON-283-001 identifying the condition of the acoustic monitor for the "S" SRV and identifying the Suppression Pool Temperature Monitoring channels that are located most closely to its discharge line.

High temperature at the Suppression Pool Temperature Honitoring Channels will provide specific indication of a discharge of steam through the "S" SRV.

The licensee's proposed changes to the TS would permit Unit 2 to operate with the "S" SRV acoustic monitor inoperable until the next unit shutdown of sufficient duration to allow for containment entry or until the upcoming refueling outage, whichever occurs first.

The sixth refueling outage is scheduled to start March 12, 1994.

Susquehanna-has Crosby safety/relief valves.

The performance history on these valves have shown only two instances of weeping, and no cycling or inadvertent opening.

Setpoint drift has not been significant.

Given the perform'ance history of these valves and the many other means available to alert the operators to possible weeping, cycling, or a stuck-open relief valve, the proposed changes to the TSs are acceptable.

3.0 EMERGENCY CIRCUMSTANCES At 1:30 p.m.

on January 19,

1994, Governor Casey declared a State of Emergency in the Commonwealth of Pennsylvania due to low electrical supply.

As of January 21,

1994, when PP&L requested enforcement discretion, Susquehanna, Unit 1 was still coming out of an extended refueling outage that began on September 25, 1993.

Susquehanna, Unit 2 had scrammed at 1:50 a.m. the day before (January 20, 1994).

Thus neither Susuquehanna units were generating

power, and were instead, using power from the grid to operate pumps and equipment.

On January 19, 1994, the Pennsylvania New Jersey Maryland Interconnection (PJH), of which PP&L is a

part, had initiated an emergency mode of operation, including primary reserve alert, voltage reductions, load curtailment, and rolling blackouts.

The Federal Government, including NRC headquarters, closed early on January 19,

1994, remained closed on January 20,

1994, and opened late on January 21, 1994, to reduce power demands.

Many coal fired plants were shut down due to frozen coal piles.

Many oil-fired plants were shut down due to gelled oil or inability to get delivery of oil because of frozen rivers or ice and snow on the roads.

Essentially, all co-generation plants in Pennsylvania had shut down due to cold weather.

At 1:50 a.m.

on January 20,

1994, Susquehanna, Unit 2, scrammed from 100X power as a result of a turbine/generator trip on high stator cooling water temperature.

A problem with the stator cooling temperature control valve linkage caused the valve to reposition such that all of the flow bypassed the heat exchanger.

Eight SRVs lifted and peak reactor pressure was 1083 psig.

The reactor recirculation pumps were restarted at 2:15 a.m.

and 3:02 a.m.

and Unit 2 was brought from Mode 3 to Mode 2.

During the startup from this scram, the acoustic monitor for the "S" SRV spuriously alarmed, indicating an open valve and flow greater than 25K.

The "S" SRV was verified closed through other indications.

An investigation, along with a discussion with the equipment vendor revealed the problem to be with the acoustic monitor system components located inside containment.

Repair would require shut down and containment entry.

Since the acoustic monitor could not be relied upon to provide accurate indication, it was declared inoperable on January 21, 1994, at 6:05 a.m.

and the appropriate Limiting Condition for Operation (LCO) was entered.

The licensee addressed why the emergency situation occurred and why it could not be avoided.

The licensee stated that:

"The failure of the "S" SRV acoustic monitor was an unanticipated failure of a component during the plant startup.

Previous operations did not indicate a problem; repairs to the acoustic monitor can not be affected with the unit in startup or at power."

We agree with the licensee that the erratic indication on the acoustic monitor was not something that would be anticipated and that there was no action they could have taken, short of shutting down and replacing the instrument, to avoid failure.

At the time PP&L requested enforcement discretion on January 21, 1994, Unit 2 was in Operational Condition 2 with only a few hours remaining to reach Operational Condition 1.

To perform an adequate investigation of this inoperable acoustic monitor would require returning to cold shutdown, deinerting the containment, making a containment entry to repair/replace the acoustic monitor, and beginning the restart process upon completion of these

repairs, resulting in several days of delay during these emergency situations.

As noted previously, the TS changes being approved by this amendment were implemented on January 21,

1994, when the Commission granted PPLL's request for enforcement discretion.

The staff determined that operation with the one acoustic monitor inoperable involved minimum or no safety issues and that enforcement discretion was clearly warranted.

The staff has also concluded that processing an amendment to the TSs to formally implement what was approved in the Notice of Enforcement Discretion was warranted under 10 CFR 50.91(a)(5).

4.0 FINAL NO SIGNIFICANT CONSIDERATION DETERMINATION The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant hazards consideration if operation of the facility in accordance with the 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 license proposed that the TS change did not involve a significant hazards consideration, stating as follows:

The proposed change does not:

Involve a significant increase in the probability or consequences of an accident previously evaluated.

The acoustic monitors do not affect the operation of the safety/relief valves.

The valve functions [safety-related Safety Function (TS 3.4.2), safety-related ADS function (six selected valves-TS 3.5.1) and non-safety related automatic and manual relief functions] are independent of the acoustic monitoring function.

No failure or misoperation of the acoustic monitoring system can affect the ability of these valves to perform their design functions.

Failure of the acoustic monitoring system to actuate in the event of an actual valve actuation does not affect the consequences of that action.

The consequences of an undetected SRV failure to close or to remain closed when desired or required is unacceptable; the purpose of the monitoring system is to increase the probability that a failure of the valve actuation mechanism is detected.

Operation without this detection system will not significantly increase the plant vulnerability to the event.

Operation without this detection system would also not create any condition where the reliability of the valve is reduced.

The SSES IPE assigns a conservative IX probability to the stuck open safety relief valve.

This valve is specifically designed and specified for the intended function, and is operated and maintained in accordance with the requirements 'of the design.

The lack of position monitoring will not affect the valve's ability to perform its intended operational and safety function.

Operation without the SRV acoustic monitor will not affect the plant response to the stuck open relief valve at power or hot shutdown conditions.

The stuck open SRV transient as analyzed in the Design Assessment Report (DAR) (Appendix I) indicates that the maximum pool transient temperature (185 'F) does not approach the NUREG 0783 accepted limit (208 'F bulk pool temperature).

This is assured by using SPOTMOS in accordance with off normal procedure ON-283-001.

SRV tail pipe temperature rise is a true early indication of SRV actuation and a reliable indication of closure.

Alarms generated by this sensor will alert the operator to the open SRV and start the two minute period mandated by Technical Specification 3.4.2.

The Suppression Pool Temperature Elements located closest to the "S" SRV discharge quencher will also indicate heat input to the pool from that line.

Other indications can be used to infer an open relief valve and to confirm a closed valve (i.e.,

by demonstrating pressure integrity).

The probability of a Stuck Open SRV Event is not affected by the presence of position indication for the SRV.

The ability to detect the stuck open SRV condition is adequately covered by the tail pipe temperature indication and secondary reactor vessel and steam cycle parameter indications, and will not result in an increase in the probability or consequences of an accident previously evaluated.

2.

Create the possibility of a new or different type of accident from any accident previously evaluated.

The SRV Acoustic Monitor performs no control or active protective function other than indication.

Failure or misoperation of this device will not cause an unanalyzed failure or misoperation of an engineering safety feature.

Because of the diverse and redundant indication system described

above, misoperation of this system will not cause the operator to take unanalyzed

actions, nor will it cause the operator to commit errors of commission or omission, and as such will not create the possibility of a new or different type of accident.

3.

Involve a significant reduction in the margin of safety.

Operating without the "S" SRV position indication does not reduce the design or operating basis margin to safety.

In the unlikely event that the "S" SRV should cycle, sufficient indication would be available to identify and mitigate the occurrence.

Thus, this change has been demonstrated to have no safety significance and will result

'n no change to the margin of safety.

Based on the above discussion, the staff concludes that this amendment meets the criteria and therefore, does not involve a significant hazards consideration.

5.0 STATE CONSULTATION

In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendment.

The State official had no comments.

6. 0 ENVIRO M NTA CONS IOERAT ON The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.

The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.

The Commission has made a final no significant hazards finding with respect to this amendment.

Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).

Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

5.0 CONCLUSION

The Commission has concluded, based on the considerations discussed

above, that:

(1) the amendment does not (a) significantly increase the probability or consequences of an accident previously evaluated, (b) increase the possibility of a new or different kind of accident from any previously evaluated or (c) significantly reduce a safety margin and, therefore, the amendment does not involve a significant hazards consideration; (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed

manner, (3) such activities will be conducted in compliance with the Commission's regulations and, the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor:

R. Clark Date:

january 31, 1994

v L

\\