ML18026A416

Forwards Response to NRC 910730 Request for Addl Info Re Proposed Amend 137 to License NPF-14 & Proposed Amend 91 to License NPF-22 Re Elimination of Temp Leak Detection Isolation Function in RHR Room

ML18026A416
Person / Time
Site:	Susquehanna
Issue date:	03/03/1992
From:	KEISER H W PENNSYLVANIA POWER & LIGHT CO.
To:	MILLER C L Office of Nuclear Reactor Regulation
Shared Package
ML17157B072	List: ML17157B071 ML18026A416
References
PLA-3732, NUDOCS 9203090230
Download: ML18026A416 (92)

Text

ACCELERATED DISTRIBUTION DEMONST$&TION SYSTEM REGULAOtY INFORMATION DZSTRIBUTZOSYSTEM (RIDE)A CCESSION NBR:9203090230 DOC.DATE: 92/03/03 NOTARIZED:

NO FACIL:50-387 Susquehanna Steam Electric Station,'Unit 1, Pennsylva 50-.388 Susquehanna Steam Electric Station, Unit 2, Pennsylva AUTH.NAME AUTHOR AFFILIATION

'-'KEISER,H.W.

Pennsylvania Power 6 Light Co.RECIP.NAME RECIPIENT AFFILIATION MILLERFC.L.

Office of Nuclear Reactor Regulation, Director (DOCKET g 05000387 05000388 st 870411

SUBJECT:

Responds to request for additional info re license to amend NPF-22.DISTRIBUTION CODE: AOOZD COPIES RECEIVED:LTR t ENCL g SIZE'+TITLE: OR Submittal:

General Distribution D NOTES:LPDR 1 cy Transcripts.

LPDR 1 cy Transcripts.

S 05000387 05000388/RECIPIENT ID CODE/NAME PD1-2 IA RALEIGH,J.

COPIES LTTR ENCL 1 1 2 2 RECIPIENT ID CODE/NAME PD1-2 PD COPI'ES LTTR ENCL 1 1 D D INTERNAL: ACRS NRR/DET/ESGB NRR/DST 8E2 NRR/DST/SICB8H7 NUDOCS-ABSTRACT OGC/HDS2 RES/DSIR/EIB EXTERNAL: NRC PDR NOTES: 6 NRR/DET/ECMB 7D 1 NRR/DOEA/OTSB11 1 NRR/DST/SELB 7E 1 NRR/DST/SRXB 8E 1 OC/WNB~0~EL~IFEN 0 1 1 NSIC 2 2 1 1 1 1 1 1 1 1 1 0 1 1 1 1 R D NOTE TO ALL"RIDS" RECIPIENTS:

A D D PLEASE HELP US TO REDUCE WAS'ONTACT THE DOCUMENT CONTROL DESK, ROOM P 1-37 (EXT.20079)TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!TOTAL NUMBER OF COPIES REQUIRED: LTTR 26 ENCL 24 NARO 3 1g92 Pennsylvania Power 8 Light Company Two North Ninth Street~Allentown, PA 18101-1179

~215/774-5151 Harold W.Kelser Senior Vice President-Nuclear 215/774<194 Director of Nuclear Reactor Regulation Attention:

Mr.C.L.Miller, Project Director Project Directorate I-2 Division of Reactor Projects U.S.Nuclear Regulatory Commission Washington, D.C.20555 SUSQUEHANNA STEAM ELECTRIC STATION RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION ON PROPOSED AMENDMENT NOS.137 TO LICENSE NO.NPF-14 AND 91 TO LICENSE NO.NPF-22: ELIMINATION OF TEMPERATURE LEAK DETECTION ISOLATION FUNCTION IN RHR ROOM PLA-37 2 FIL R41-2 A17-2 Docket Nos.50-387 and 50-388

Dear Mr.Miller:

This letter is in response to the NRC staff's request for additional information regarding our requested revisions to the Technical Specifications for Susquehanna SES related to the elimination of the temperature leak detection isolation functions in the RHR room.The following material provides specific responses to the staff questions contained in a letter dated July 30, 1991.RE UETN I The licensee has had previous discussions with the staff regarding this matter and for completeness, the submittal should make reference to these discussions and should include a summary of the major points of discussion and any conclusions that were reached.'R~es onse: If On February 5, 1991, PP&L and NRC staff held a meeting in'he NRC office in White Flint, Maryland to discuss issues related to PP&L steam leak detection system.The following are excerpts which discuss the RHR room issues from PP&L's summary of that meeting: OOOO"'J 9203070230 920303 PDR ADOCK 05000387 P PDR FILES R41-2/A17-2 PLA-3732 Mr.C.L.Miller The purpose of this meeting was to discuss PP&L actions taken to close the steam leak detection issue and to obtain NRC's preliminary concurrence on the action taken.Copies of the slides used during the'presentation are attached as Attachment

'A.'he detailed topics discussed were: I 1.The change in the design basis leakage rate from 5 gpm to 25 gpm in the HPCI, RCIC, and RWCU areas.(Tech Spec change submitted) 2.The deletion of the ambient temperature isolation in the turbine building main steam tunnel.3.The deletion of the ambient and delta temperature isolation in the RHR rooms.(Tech Spec change submitted) 4.Not changing the allowable value in the Technical Specification for the Reactor Building main steam tunnel.PP&L presented a discussion on the deletion of the temperature and delta temperature isolation in the RHR rooms based on the fact that the steam condensing mode of RHR was removed from the plant;and therefore, there are no high energy lines in the RHR room.The NRC staff was receptive to this deletion.RE ET 2 It is not clear why it is necessary to delete the isolation function.This should be explained in detail.Also, are other options available, such as enabling the isolation function only for periods when the RHR system is not isolated from the reactor coolant system and/or establishing a higher leak rate as the basis for isolation?

~Res~on The PP&L request to eliminate automatic isolation of RHR shutdown cooling, documented in PLA-3485 1/14/91, was based on a number of considerations.

Elimin i n f m nden in Mode: Original temperature isolation setpoints in the RHR room area are consistent with setpoints in the HPCI and RCIC areas, and are based upon temperature increases in these rooms caused by leaking steam at normal full power operating conditions.

In 1987 (Unit 1)and 1989 (Unit 2)the steam condensing mode of operation of the RHR system was eliminated FILES R41-2/A17-2 PLA-3732 Mr.C.L.Miller from the plant design, thereby eliminating the apparent basis for the temperature based isolation function.A lication to RHR Shutdown lin: A feature of the original design which has resisted explanation was that the steam temperature derived setpoints and isolation functions were applied to the isolation function for the RHR shutdown cooling suction valves.Therefore, our thermal analyses used leakage of reactor coolant at process temperatures existing when RHR shutdown cooling would be on line.For conservatism, we used a temperature of 212'F.This was within the band of possible temperatures for the Reactor Coolant System (RCS)when RHR shutdown cooling was in operation, but hot enough that some of the leaking fluid would flash to steam upon escape and be apparent to the temperature detection circuits.We believe that using the 212'F number is more conservative than using the upper end of the band in that the room thermal response is reduced with the lower driving temperature, and it would take longer for the temperature circuits to function.Using the lowest end of the band at 200'F would not be compatible with the COTI'AP thermal analyses model.n cce ilit of 5 PM an 2 PM e Ba Early COTI'AP analyses demonstrated that the original 5 gpm leak basis for setpoint selection was not supported by present analytical methods.See PLA-3630 which provided justification for the use of 25 gpm leakage as an analytical basis for setpoint selection for other ECCS rooms in which temperature based steam leak detection circuitry was used.In the RHR area however, the COTTAP thermal analyses at leak rates of 25 gpm could not be shown to support the existing Technical Specification setpoints within a reasonable time frame, and stated this in our first submittal, PLA-3485, 1/14/91, We calculated room temperature after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of a 25 gpm leak and defined that as the Allowable Value for use in our setpoint calculations.

We found that for the winter condition case, the temperatures setpoints would have to be reduced 24'F to 33'F.The resultant setpoints would be very close to the post LOCA design maximum temperatures for the area.They would not provide adequate margin and could result in inadvertent isolations when availability of RHR shutdown cooling could be very important to plant safety.Fif and ne Hundred PM We also used COTTAP to determine the room thermal response with leak rates of 50 gpm and 100 gpm.For the 50 gpm case, the resultant room temperature at the four hour point was 165'F.Using established setpoint methodology, a margin of 22'F was calculated between the maximum post LOCA temperature and the trip setpoint.Because the FILES R41-2/A17-2 PLA-3732 Mr.C.L.Miller as-installed setpoint is always provided with additional margin to avoid instrument drift beyond the Allowable Value, actual margin is further reduced.We do not consider this margin to be acceptable for potential unnecessary loss of the shutdown cooling function.For the 100 gpm case, the resultant room temperature at the four hour point was 184'.Again using established setpoint methodology, the corresponding Trip Setpoint would satisfy the existing Technical Specification Trip Setpoint of 167'F.The basis for the decision to delete the function included the low increment of additional safety provided by the automatic isolation, and the larger potential decrement in safety caused by retention of the function at a larger design bases leakage.Tim D rin WhichAuomticI l i nW ldB Fn i nl: The actual time during which the isolation circuitry would function to isolate a leak is very small.Limits are determined by RCS conditions of 98 psig (336'F temperature) and 0 psig (200'F temperature).

The upper limit is set by the high pressure/low pressure interlock which allows RHR Shutdown cooling to be unisolated only when reactor steam dome pressure is less than 98 psig.The lower limit reflects the Technical Specification requirements that steam leak detection automatic isolation functions are only required to be operable in startup, hot shutdown, and run modes of operation (i.e., when the RCS.temperature is greater than 200'F.)The condition with RCS temperatures between 200'F and 336'F is usually just a short duration transient condition with the plant traversing between hot and cold shutdown.Thus the time in which the circuitry could perform its intended function is very limited.11 Time In Which i ment Malfuncti n n e F Misactua ion:, The time window is much larger than above in which a transient or malfunction could upset the steam leak detection circuitry and cause an unnecessary isolation with shutdown cooling system in operation to maintain core temperatures below 200'F.These transients/malfunctions could originate in the electrical distribution system, HVAC system, or in surveillance and preventive maintenance induced transients.

Should one of these transients cause an automatic isolation, the potential for an undesired RCS temperature transient outside of the cold shutdown temperature band is high.Such a transient would require initiation of the SSES emergency plan, exercising both in-plant and out-of-plant response teams and would constitute an unnecessary challenge to plant safety.

FILES R41-2/A 17-2 PLA-3732 Mr.C.L.Miller If the transients or malfunctions were to initiate an inappropriate isolation circuit actuation during the time in which the plant were at power (RHR Shutdown Cooling isolated), the above consequences would not be applicable.

However, reporting and documentation requirements would remain.her n iderati n: We considered the process of leak development.

Most leaks would start small and grow over long periods of time.We believe it improbable that a leak could progress to values close to the 100 gpm leak rate without detection by instrumentation alarms or by plant staff, Included in these means would be room flood detection, area radiation monitors, temperature alarms, and actual RHR room temperatures read in the control room.Our original proposal in PLA-3485 stated that deletion of the automatic isolation function would not include deletion of the temperature indication and alarm functions presently associated with the isolation function.;

These functions would be retained.See our response to Request No.5.We also considered retention of the isolation function with enabling/disenabling switches to ensure that the isolation function was only operable in the small period of time in Condition 3 while traversing between the high pressure/low pressure interlock temperature and cold shutdown limits.We concluded that this approach would not be beneficial in that it would not improve the sensitivity of the circuitry to potential leaks, it would unnecessarily complicate plant design, promote potential personnel error and possible ESF equipment misoperation or malfunction.

As stated in Regulatory Guide 1.45 RCPB Leakage Detection System"it is not necessary that all leakage detection systems be employed in a specific nuclear power plant.However, since the methods differ in sensitivity and response time, prudent selection of detection methods should include sufficient systems to assure effective monitoring during periods when some detection systems may be ineffective or inoperable.

Some of these systems should serve as early alarm systems signaling the operators that closer examination of other detection systems is necessary to determine the extent of any corrective action that may be required." In line with the philosophy of the Regulatory Guide the use of temperature monitoring as a method of isolation is effective and appropriate wh'en used in conjunction with high energy lines such as RWCU, HPCI, RCIC, and main steam.It is ineffective when used for lower pressure/temperature lines such as the RHR shutdown cooling mode because detection would require leakage rates of greater than 90 gpm existing for up to four hours.As stated in PLA-3485, the inadequacies of the system for automatic isolation would not impact on its use for room temperature monitoring and alarm at lower leakage rates. FILES R41-2/A17-2 PLA-3732 Mr.C.L.Miller Without the consequences of unnecessary isolation actuation, margins could be reduced resulting in manual detection and alarm of lower leakage rates.PP&L is following the guidance of the Regulatory Guide by maintaining the high temperature alarm function and utilizing flood detection, area radiation monitors and operator rounds to monitor for leaks.These leak detection methods are described in detail in response to Request No.5.We believe that consideration of the issues as explained herein and in our original submittal PLA-3485 provide the detail to justify the deletion of this function.RE UE TNO 3 The staff's copy of the FSAR for Susquehanna has not been updated for some time and the information regarding RHR operation may not be current, In order to facilitate the staff's review, a detailed description of the RHR system and operating modes should be provided.R~es oose: An updated copy of the FSAR for Susquehanna was recently provided to the Project Manager for the Staff's use.Section 5.4.7 provides a description of the modes of the RHR system.RE UE TNO.4 Details of the RHR pump room temperature analysis should be provided for staff review.Detailed information related to the application of computer codes should also be provided unless the staff has previously reviewed and approved the code for the specific application in question.In any case, all assumptions used in the analysis should be identified and fully explained.

~Res oose: PP&L's submittal to the NRC, PP&L letter PLA-3630 dated August 19, 1991, on Temperature Leak Detection RWCU/HPCI/RCIC contained the user's manual for the COTTAP computer code and a copy of a paper recently published in Nuclear Technology which describes the methodology used in the COITAP program and presents some of the verification calculations which have been performed.

The user's manual presents some of the calculations which were performed against problems that have.exact analytical solutions.

The referred paper presents the methodology along with calculations which have been benchmarked against calculations performed with the CONTEMPT computer program.In addition, the program and computation package have been independently FILES R41-2/A17-2 PLA-3732 Mr.C.L.Miller reviewed by Gilbert Associates.

PP&L also maintains a Quality Assurance file/package for the COTTAP computer code.PP&L has not resubmitted this information with this request for additional information.

Attachment B contains a summary of the calculations which were performed for the RHR Pump Room and upon which the setpoint deletions were based.Calculations were performed under a variety of conditions (for example, summer and winter initial conditions) and have been independently reviewed.Attachment B also contains the COTTAP results for a 50 gpm and 100 gpm leak.The attachment presents a summary which includes the methodology and assumptions for each calculation along with the representative results.RE VEST N.The licensee has discussed actions that can be taken in lieu of the automatic isolation function, but complete description of specific actions that will be required and how these requirements will be implemented has not been provided for staff review.The qualification, quality classification, surveillance requirements and single-failure aspects of equipment such as the sump level instrument and annunciators have not been discussed and it is not clear to what extent this equipment can be relied upon to function.Additionally, there was no discussion relative to ASME Code requirements and how these requirements would be satisfied.

~Res oose: Deletion of the high temperature, automatic isolation function from the RHR Shutdown Cooling mode of operation will require operator action.Alternative leak detection methods and their utilization are discussed below.1.0~AI There are three high temperature alarms in the control room: RHR Leak Detection Hi Temp, RHR Leak Detection Logic A Hi Temp and RHR Leak Detection Logic B Hi Temp.1.1 RHR Leak Detection Hi Temp This alarm is initiated via RHR pump room high ambient or differential temperature detection.

The setting is lower than the present Technical Specification isolation setpoint to alert Operators early on of potential off normal conditions.

Operator response is covered by alarm response procedure AR-109-001.

Specific operator actions are:

FILES R41-2/A 17-2 PLA-3732 Mr.C.L.Miller a.Determine what produced the alarm by observing temperature recorders located in the Control Room.b.C.Check system for leaks.Check Reactor Building ventilation system for proper operation.

There are no automatic actions resulting from this condition.

The system utilizes a Class 1E temperature element and an affiliated cable to a non-Class 1E temperature recorder with input into the non-class 1E annunciator system.RHR Leak Detection Logic A Hi Temp/RHR Leak Detection Logic B Hi Temp This alarm is initiated via RHR Pump Room high ambient and differential temperature detection.

The alarms are set to pick up in accordance with the present Technical Specification isolation setpoints.

The temperature monitoring system is divisionalized in each RHR pump room.The system utilizes redundant Class 1E temperature detectors, switches, cable and raceway with inputs into the non-class 1E plant alarm system.Operator response is covered by alarm response procedure AR-109-001.

Proposed operator actions with deletion of the automatic isolation function are: a.Check panel 1C614 in Control Room to determine source of high temperature or high differential temperature.

b.Check temperature module for proper operation and alarm setpoint.C.Check system for leaks.d.Check Reactor Building Ventilation System for proper operation in accordance with OP-134-002.

FILES R41-2/A17-2 PLA-3732 Mr.C.L.Miller F'I 2.2 i~ID Level instrumentation is provided in each of the divisionalized RHR Pump Rooms.The instrumentation is non-class 1E.Level indication will detect a 50 gpm leak in about 90 minutes and a 100 gpm leak in about 45 minutes.Operator response is covered by alarm response procedures AR-109-001.

Specific operator actions are: 'I~Perform, off-normal procedure, ON-120-001, Flooding in Reactor Building.~'-Dispatch operator to assess extent and determine source of flooding.~Isolate source of flooding as rapidly as possible, unless source is required to shutdown reactor or assure adequate core cooling or suppress a fire.~Follow the remaining steps in ON-120-001.

Again the flooding procedure requires the operator to assess and manage the leak relative to assuring adequate core cooling.This is in-line with the position to delete the automatic isolation function.3.0 A mticT I inF re The following are the additional automatic isolation features for the RHR system in the shutdown cooling mode excluding the temperature detection features: Reactor vessel water level signal will isolate the system if the vessel level drops below 13.0 inches.Reactor vessel pressure signal will isolate the system if the vessel pressure exceeds 98 psig.RHR flow signal will isolate the system if the flow is greater than 25,000 gpm.4.0 e rR nd In accordance with operations procedure OI-PL-0161 the operator must enter the RHR pump room to check bearing oil levels every 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.If a leak were to occur before the high temperature or flood detection alarms actuated the operator would identify the leak during rounds. FILES R41-2/A17-2 PLA-3732 Mr.C.L.Miller Relative to the ASME Code requirements, the Susquehanna SES ISI Manual which is based on'ASME Section XI, defines the plant specific piping and component inspection requirements and the frequency with which'"the ISI is performed.

For the RHR lines, a leak test is performed every other'utage to identify potential areas of pipe degradation.

A surface and volumetric weld exam is also performed every ten years to identify potential weld defects.1 If a leak were to occur, the operator would assess and manage the leak and weigh its severity to the importance of providing adequate core cooling.The faulty pipe would be repaired in accordance with the ASME Section XI repair and replacement requirements.

The repair will be inspected in accordance with ASME Section XI.Prior to startup, an evaluation of the leaks effect on other area equipment will be conducted and appropriate action taken.The steam leak detection system (ambient and delta temperature) at Susquehanna SES is not required by the ASME Code, nor is it used to show compliance with the ASME Code.RE ZT The licensing basis assumes that leaks from the reactor coolant system will be isolated in a short period of time.Without the automatic isolation capability in place, a detailed analysis of the radiological consequences of a coolant leak outside primary containment must be completed and submitted for staff review.Resp'~: For the greatest part of plant life, RHR is isolated from the reactor coolant system by two isolation valves subject to a high/pressure/low pressure permissive.

The next greatest part of plant life is spent in cold shutdown when steam leak detection is not effective and is not required.Only a small portion of plant life (a transient condition) is spent with the RHR shutdown cooling isolation function being on-line and ready to operate.In this period, on line instruments are available to warn of a reactor coolant system leak.If a leak were to occur, installed instruments and operator observation would detect that leak before 10CFR100 limits were reached, and before leakage rates could approach the 100 gpm value.Action would be required to isolate the leak.This conclusion would hold regardless of whether the presently installed steam leak detection isolation functions were retained or removed.The radiological consequences of a coolant leak outside primary containment were analyzed in PP&L calculation SE-B-NA-078.

Fifty gpm of reactor grade water was assumed to leak to secondary containment at a concentration of 4.0 uCi/gm Dose FILES R41-2/A17-2 PLA-3732 Mr.C.L.Miller.Equivalent Iodine-131.

This is the maximum allowable coolant concentration of iodine for Susquehanna SES operation.

No credit for removal, holdup or decay was taken.The period of the leak was assumed to be 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after which environmental leakage was terminated.

The analysis concludes that the resultant offsite and control room doses fall far below 10,CFR 100 offsite dose limits and 10 CFR 50, Appendix A, GDC-19 control room dose limits.An analysis of a reactor steam leak was also conducted in PP&L calculation FX-C-DAM-010.

A 50 gpm water equivalent steam leak was assumed to occur for a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period.No credit for removal, holdup or decay was taken.This analysis also concluded that the resultant offsite and control room doses fall far below 10 CFR 100 offsite dose limits and 10 CFR 50, Appendix A, GDC-19 control room dose limits.Calculations SE-B-NA-078 and FX-X-DAM-010 which document the radiological analysis were included in PP&L's letter PLA-3630 dated August 19, 1991 on temperature Leak Detection RWCU/HPCI/RCIC.

Based on the calculation, even if a 100 gpm leak of'reactor coolant were allowed to continue for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the resultant'offsite and control room doses fall far below 10CFR100 offsite dose limits and 10CFR50, Appendix A, GDC-19 control room dose limits.It is not expected that a leak at any rate, would continue for an extended period.(greater than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />)without isolating shutdown cooling.If you have any questions, please contact Mr.C.T.Coddington at (215)774-7915.Very truly yours, H.W.Keiser Attachment cc: NRC Document Control Desk (original)

NRC Region I Mr.G.S.Barber, NRC Sr.Resident Inspector Mr.J.J.Raleigh, NRC Project Manager ATTACHMENT A F9203090230.'

Susquehanna Steam Electric Station Steam Leak Detection Issues I I 5 AGENDA Introducti on C, T.Coddington Mari agement Perspective

',l.I I Discussion of Issues F.G.Butler D.J.Cardinale and J.C.E:night Rx Bldg MS Tunnel dT Inop NOTIFICATION PROB CORR MNGMNT PLAN GENERIC WALK DOWNS MODS t CODE DVLPMT~DESIGN BASIS ROOT CAUSE QUESTIONAIRE CHANNEL CHK 7/27/88 8/88 9/88 ROOM THERMAL MODELS STEAM TUNNEL COOLER MODEL LEAK RATE ASSMNTS SETPOINT CALCS TECH SPEC FSAR CHANGES PRESSURE TEMPERATURE RESPONSE PLANT MODS 3/89 6/90 9/90 1/91 2/91

Rx Bldg MS Tunnel dT lnop NOTIFICATION I PROB CORA)MNGMNT PLAN GENERIC WALKDOWNS MODS ICODE DVLPMT t DESIGN BASISI ROOT CAUSE QUESTIONAIRE CHANNEL CHK ROOM TI IERMAL MODELS LEAK RATE ASSMNTS PRESSURE TEMPERATURE RESPONSE SL I I'()IN I (AL(:S 1LCI I!il'LlAI I (.'I I AN(il.S I'LANT MODS J I SII.AM 1UNNLLOOLI II MODLI.7/27/88 8/88 9/88 3/89 6/iJ()iJ/iJ()I/iJ I'/iJ I MANA EMENT ACTION TEAM MANAGEMENT DESIGN I&C MAINTENANCE SSES TECHNICAL STAFF COMP I IANCE LICENSING ANALYSIS OTHERS AS REQUIRED-RADIOLOGICAL EQ PARTS RE R E AP LIED BECHTEL GEERAL ELECTRIC ORIGINAL A/E THERMAL CALCULATION ORIGINAL SETPOINT CALCULATION DESIGN BASIS CONFIRMATION CRITICAL CRACK SIZE ANALYSIS GILBERT COMMONWEALTH

-TUNNEL THERMAL MODEL VERIFICATION AIR COOL TUNNEL COOLER MODEL P

ORIGINAL DISCOVERY:

July 27,<988 CONDITION DISCOVERED:

REACTOR BUILDING MAIN STEAM TUNNEL BOTH UNITS AFFECTED FOUR TRIP CHANNELS PER UNIT DIFFERENTIAL TEMPERATURE ISOLATION TRIP FUNCTION INOPERABLE"HOT" AND"COLD" LEG TEMPERATURE ELEMENT LOCATlO'NS REVERSED

'4 INIMEDlATE ACTlONS: PROMPT MANAGEMENT ATTENTION AND ACTION PLANNING PROMPT NRC NOTIFICATION INSTRUMENTS REWIRED TO REVERSE DIRECTION OF DELTA-T SIGNAL RESTORE INSTRUMENT OPERABILITY DEFINE A IVIANAGEMENT TEAM TO-DETERIVIINE CAUSE (S)-REVIEW THE DESIGN, AND WALKDOWN ALL OTHER SLD TENIPERATURE SENSORS FOR RELATED PROBLEMS-IMPLEMENT CORRECTIVE ACTIONS FOR SHORT TERIVI PROBLEMS-IMPI EMENT ACTION PLANS FOR LONGER TERM PROBLEMS PARTICIPANTS IN TEAM TO INCLUDE: MANAGEMENT DESIGN-.STATION TECHNICAL STAFF OPERATIONS LICENSING AND COMPLIANCE MAINTENANCE OTHERS AS REQUIRED Qfl g CORRECTIVE ACTION ITEMS:-PERFORM DESIGN BASIS ANALYSES OF ROOM THERMAL RESPONSE TO STEAM LEAKS AS IDENTIFIED IN FSAR.-ASSESS LOCATlONS OF OTHER TEMPERATURE ELEMENTS AND CORRECT PROBI EMS WHERE FOUND.-ENSURE ADEQUATE INSTALLATION INSTRUCTIONS ARE PROVIDED IN MODIFICATION PACKAGES FOR TEMPERATURE ELEMENT INSTALLATION

-ASSESS VALUE OF DELTA-T INSTRUMENTS FOR ISOLATION OF STEAM LEAKS, AND COORDINATE THIS ACTIVITY WITH THE BWROG.QUESTIONNAIRE SURVEY, OPERATIONS AND I8cC MAINTENANCE STAFF.-ROOT CAUSE ANALYSIS-CLEARLY ASSIGNED SLD SYSTEM RESPONSIBILITIES

-IDENTIFY NORMAL VALUES FOR VARIANCE CHECKS-EVALUATE RECORDING AND RETENTION OF DATA DURING DAILY CHANNEL CHECK ACTIVITIES.

-V l Ay Ci (*

OTHER CONSIDERATIONS

-PROMPT NRC REPORTING-ENFORCEMENT CONFERENCE 88-226, DATED 9/30/88-REGULAR AND ONGOING COMMUNICATION WITH NRC-INDUSTRY FOREFRONT IN PROBLEM IDENTIFICATION AND RESOLUTION

-EARLY AND CONTINUOUS DIALOG WITH NSSS SUPPLIER-INDUSTRY FOREFRONT IN ROOM THERMAL RESPONSE CODE DEVELOP MENT COTTAP: COMPARTMENT TRANSIENT TEMP ERATU R E ANALYSIS PROGRAM-FORMAL SETPOINT CALCULATION METHODOLOGY

-ALL INCLUSIVE PROGRAM, DESIGN ANALYSES COMPLETED, WITH RECOMMENDATIONS DEFINED, JUSTIFIED, AND DOCUMENTED.

I I c$V SENSOR P LACEM ENT STEAM LEAK DETECTION SYSTEM PROBLEMS SYSTEM/AREA UNIT 2 Rx BLDG MAIN STEAM TUNNEL PROBLEM SENSORS INSTALLED REVERSED DELTA-T MONITORED ACROSS COOLERS ACTION SOOR 1-88-205.DCP 88-9023 CORRECTED PROBLEM BY REVERSING LEADS NCR 88-0554.DCP 88-9024 RELOCATED TE'S TO VENT INLETS.NIT 2 HPCI ROOM DELTA-T INLET TE'S NOT FULLY IN COLD AIR INLET.NCR 88-6062.DCP 88-6057 RELOCATED HVAC INLET DUCT FLANGE.(ECO)UNIT 1 Rx BLDG MAIN STEAM TUNNEL UNIT 1 RWCU AREA SENSORS INSTALI.ED REVERSED.PUMP ROOM HI AMB TE I OCATED INCORRECTLY.

SOOR 1-88-0598.

DCP 88-9022 CORRECTED THE PROBLEM BY REVERSING WIRES.NCR 88-0598.DCP 88-9030 RELOCATED TE.PUMP RM DELTA-T TE LOCATED IN LESS SENSITIVE AREA THAN DESIRED.DESIGN BASIS THERMAL CALCS.DCP 90-9036 RELOCATED TE TO MEASURE ONLY PUMP ROOM EXHAUST TEMPERATURE.

PENETRATION RM SENSOR LOCATED IN PUMP ROOM.NCR 87%484.DCP 87-9215 RELOCATED TE.

STEAM LEAK DETECTION DESIGN BASIS REGULATORY REFERENCES GDC 30: REQUIRES THAT ibiEAi4S BE PROVIDED FOR DETECTING AND....IDENTIFYING LOCATION OF REACTOR COOLANT LEAKAGE.REG GUIDE 1.45 LEAKAGE IDENTIFICATION

&MEASUREMENT DRY WELL SUMP LEVEL OR FLOW TWO OF THREE OTHER TYPES PARTICULATE NOBLE GAS TEMPERATURE BASED ISOLATION SYSTEMS NOT SPECIFICALLY DISCUSSED SRP (5.2.5)REFERENCES GDC 30 AND R.G.1.45 AS CONTROLLING DOCUMENTS FOR DETECTION, IDENTIFICATION AND MONITORING OF REACTOR COOLANT LEAKAGE.

1 ,',I 0 P~~i'I 1 ECCS ROOM SLD DESIGN BASIS SSES REFERENCES FSAR: 5.2.5.1.3 defines the basis for HPCI, RCIC, and RHR SLD systems--setpoints are kept low enough to allow timely detection of a 5 gpm leak.(does not define the basis for RWCU, nor the Main Steam Tunnel)-setpoints include sufficient margin above post LOCA maximum area temperatures to preclude inadvertent isolation signals.SER: 5.2.5-notes that temperature sensing systems are installed.

-concludes that leakage detection systems provide.reasonable

assurances TECH SPECS BASIS 3/4.3.2-Isolation Actuation Instrumentation Setpoints are established at a level away from normal operating range to prevent inadvertent operation.

ECz ESTABLISHING DESIGN BASIS FSAR SEARCHES-.'sparrow window for setpoint selection BECHTEL (A/E)CALCULATION REVIEWS:-Simplified Model-No Heat Loss, Rapid Heat Up-Setpoints selected:-with large tolerances

-similar to previous BWRs-below fire protection system setpoints GE Company (NSSS)Study Effort-5 gpm vs 25 gpm basis-25 gpm current design, BWR 4 design

,.tg r,q INITIAL 0EVELOPME'.iT 1.RECONCILIATION OF FSAR OBJECTIVES 2.ROOM THERMM, ANALYSES-%'inter Conditions

-Summer Conditions 3.COTTAP CODE DEVELOPMENT

-Energy Balance-Mass Balance-Single Node Model

SLD THERMAL MODEL ORIGINAL DESIGN SLD THERMAL MODEL COTTAP DESIGN COTTAP Compartment Temperature Transient Analysis Program A computer code to predict environmental conditions in compartments separated by uniform walls.The code solves transient heat and mass balance equations to determine temperature, pressure and relative humidity.The one-dimensional heat conduction is calculated for each slab to compute heat flow between rooms.User inputs include physical and geometric data, steam leak conditions, flow path data and initial conditions.

DESIGN BASIS LEAKAGE RATE Problem tatement: FSAR Requires~, Setpoints have sufficient margin to preclude inadvertent isolation~Setpoints be low enough to allo~timely detection of a 5 gpm leak Calculations show~Setpoints consistent with detection of 5 gpm could cause inadvertent isolation HPCI ROOM TEMPERATURE RESPONSE (WINTER)260~, 200 (3.D UJ K: 150 I-CL 100 eo--0 10 15 TIME (HRS)I 20 I 25 LegeI>d g'b OS'Lt I/p5 CPM lbOL Al>OH bt If'OIHI TEMPERATURE SETPOINT CALCULATION RESULTS HPCI Room A,IIB IE, iT Evistine Calculated DIFFERENTIAL Evistino Cele.:ta!e.:.

Analytical Limit Allowable Value Trip Setpoint Process Setpoint RCIC Room Analytical Limit Allowable Value Trip Setpoint Process Setpoint HPCI/RCIC piping Area Analytical Limit Allowable Value Trip Setpoint Process Setpoint+it A 174 167 160 N/A 174 167 159 N/A 174 167 160 201 194 188 182 230 223 217 211 191 184 178]72 M/A 98 89 86 N/A 98 89 86 N/A 98 89 86 I" l 116 3 107 147 1 g'l 139 133 105 100 97 93 PROPOSED L$DX DETECTION SETPOINT CK-'&CAGES HPCI Room AMBIE'.4T Exisrin~COOLER I'.iLET~Exisri o P~ro osed Allowable Value Trip Setpoint Process Setpoint RCIC Room Allowable Value Trip Setpoint Process Setpoint 174 167 160 174 167 160 154 147 140 154 147 140 174 167 160 174 167 160 I l,j(Wl SAFETY A E ME.v'T 25 gpm leak rate basis allows timely detection of leakage without risk of inadvertent isolation 25 gpm basis is consistent with GE design Spec and with basis used for other BWR's and accepted by NRC Leak Detection System continues to conform to requirements of GDC 30 and Reg.Guide 1.45 Tech Spec changes provide additional margin to assure HPCI, RCIC and R%CU systems will not inadvertently isolate Other redundant leak detection systems continue to perform their safety function "a', PI lg gl t.U 4V"ip DELETION OF STEAM LEAK DETECTION SLD ISOLATION FUNCTION-RHR ROOM (TS CHANGE O220)PROBLEM STATEMENT:

Design Philosophy of SLD is Not'onsistent in RHR Room~Existing RHR Room Temperature SLD Isolates Shutdown Cooling (SDC)~Setpoints Based on Leakage from Steam Condensing Mode~SLD in RHR Room Not Evaluated as Part of Removal of Steam Condeasiag Mode Lowering Setpoints Create Possibility Qf Inadverteat Isolatioa of SDC Coaflicting Design Documeats~GE Desiga Spec-Alarm Oaly~FSAR-Alarm Only/Alarm

-Isolation~TS-Alarm-Isolati oa RHR PUMP ROOM (I-14.104)HEATUP EVALUATION (25 GPM WATER LEAK/WINTER)

-160.140 (3 Lal l20:-LJ I-w~100 CL LLI I-80-60 10 15'IME (HRS)20 I 25

.5)ig 4 TEMPERATURE SETPOINT CALCULATION RESULTS RHR Room AilfBIENT~is~t'alculated DIFFERENT!AL

~v~t Calcu ated Analytical Limit Allowable Value Trip Setpoint Process Setpoint N/A 170.5 167 156 147 140 134 128 N/A 90.5 89 86 73 70 67 63 f,y 1I~%S't SAFE T Y ASSESSMENT Redundant Systems Adequate to Detect Leaks in SDC Temperature Alarms, Flood Alarms and Manual Isolations Satisfy Need to Defect/Control Leakage in RHR Room~Manual Isolation Reduces Net Risk of Isolating System Under Non-Leak Conditions Consequence of Operating SDC~ith Small Leak May be Loser Than Consequence of.Losing Decay Heat Removal 7 h, REACTOR BUILDING MAIN STEA.'vf TUNVEL PROBLEM STATEMENT:

Original calculations showed existing Tech Spec setpoints are inconsistent with the design basis conditions.

Cooler performance is difficult to model due to variations in relative humidity and latent heat removal.Latest calculations produce setpoints consistent with the design basis.

,C V CALCULATION PROCESS Original model used simple cooler model (neglecting latent~~cooling)and no room pressurization.

Model was refined to integrate cooler model (vary latent heat removal)and to include pressurization.

Conservative interpretation of"25 gpm water equivalent" was changed to match basis used for dr@veil leakage.

STEAM TUNNEL TEMPERATURE RESPONSE (WiNTER)200 180 C9 LLl-Q 160 CC.140 CL 1Z0 100 0 10 15 TIME (HRS}I 20 25 Legend~40 Cf'M (J"5GVM'iso'.Aviv~

st irvi~<

STEAM TUNNEL HEATUP EVALUATION (25 GPM EQUIVALENT STEAM LEAK/WINTER) 200 180 C3 4J.160 LLJ 43 140 CL LJ t-'20 100 0 15 10 TIME (HRS)I 1 I 20 I 25 IAITI.M CAJ.CULATIOYf RESULTS Ambient Temperature Setpoints~Evistin 25 gpm 50 gpm alculated Calculated Analytical Limit Allowable Value.Trip Setpoint Process Setpoint N/A 184 177 174 166 159 153 150 191 184 178 175 Differential Temperature Setpoints Qdsti~n 25 gpm 50 gpm alculated Ca culated Analytical Limit Allowable Value Trip Setpoint Process Setpoint N/A 108 99 96 90 85 82 80'09 104 101 99 P 0 1*

PRESENT CALCULATION RESULTS Ambient Temperature Setpoints~Ev'ski~C~id'I I d Analytical Limit Allowable Value Trip Setpoint Process Setpoint N/A 184 177 174 184 177 174 168 187 180 177 171 Differential Temperature Setpoints F~x'stag Calcu ared'alculated-'nalytical Limit Allowable Value Trip Setpoint Process Setpoint N/A 108 99 96 109 104 102 97 109 104 102 97 1.Interpolated temperature from 9300&;14,800 lb/hr calculations.

2.Calculated temperature for 12,500 lb/hr leak.

ASSESSME,'-iT Calculated setpoints confirm the existing setpoints are consistent with detection of leaks 25 gpm or greater.Results are within the margin of error of the model.No change is required to the existing Tech Spec setpoints.

t TURBINE BUILDING MAIN STEAVf TU'NOEL DELETION OF HIGH TEAPERATL'RE ISOLATION, PROBE.E~!STATEWiE.'v'TS o Exisitin set pints are not adequate to detect and isolate a 25 gpm leak.e The existing system does not provide sufficient protection against false isolation.

~Detection capability is highly dependent on leak location.~The steam tunnel is not a c osed vo u e and does not fit the basis for temperature measurement.

~Analyzing the tunnel to establish reliable setpoints requires a complex 3D model beyond the odellin ca abili of available computer codes..~Temperature alarms and e detectio ethods used elsewhere in the turbine building are adequate to detect and control leakage.

TURB BLDG STM TUNNEL EVALUATION (25 GPM EQUIV STM LEAK/WINTER) 150 140-C3 IJJ" C3 LJJ 150 lY LJ CL I-120 110 0 10 15 TIME (HRS)20 25 h~V I>>, J~

RISK OF FALSE ISOLATION The existing setpoints provide insufficient margin (less than 25'F)above the normal maximum temperature.

Temperature increases along the length of the tunnel and TE's are located'in the highest temperature area of the tunnel.Temperatures up to 150'F have been observed with normal, non-leak conditions.

Temperatures have reached the 157'F alarm setpoint due to small packing leaks and ventilation system disturbances.

C I r i:~'D l g/il LEAK DET=: pip~-~~c t A'VI gl 4\y Its LEAK LOCATION Leakage at the far end of the tunnel from the TE's will be diluted and masked.Leakage near the TE's is undiluted and has an amplified effect on measured temperature.

Leaks downstream of the TE's will not be detected.

~1~Cl I

CLOSED VOLUVIE The open end of the tunnel al1ows uncontrolled f1ow into and out of the tunnel.The effect of this How path on temperature measurement and leak detection capability is unknown.Temperature measurement should be used in a closed volume to effectively detect leakage.FSAR 5.2.5.13-"piping...is installed in compartments or rooms...so that leakage may be detected by area temperature measurement."

TEMPERATURE MODELLING CAPABILITY The configuration of the tunnel causes difficulty in creating a temperature model.COTTAP is limited to calculating average temperature for the room volume.The temperature gradient and flow patterns cannot be accurately modelled with available computer codes.

LEAK DETECTION METHODS Main steam lines elsewhere in the turbine building are not montitored by leak detection instruments.

Radiation alarms, visual observation provide adequate.detection capability.

Temperature alarms for the steam tunnel will be retained.

I' SAFETY ASSESSME'NT

~Deleting the automatic high temperature isolation signal reduces the risk of inadvertent main steam line isolation.

~Reliable isolation setpoints cannot be established to provide sufficient protection against inadvertent isolation.

~Temperature alarms provide adequate leak detection capability in the main steam tunneL~The radiological consequences of a 25 gpm leak are well mthin safety limits.

ga j,l li, fl>>g.4 II t t RADIOLOGICAL CONSEQUENCES 25 GPM STEAM LEAK FOR 2a HOURS Dose Category 2 HR Site Boundary Thyroid 2 HR Site Boundary Whole Body 30 Day Low Population Zone Thyroid 30 Day Low Population Zone Whole Body 25 gpm Calculated Dose (rem)1.89x1 0~9.55x1 0 2.17Ã1 0 1,09x1 0 FSAR Steam Line Break Dose (rem)3.07 2.98x10'.98x10 6.77x1 0 SRP Acceptance Criteria 300 25 300 25 S" I A 3'J t OBSERVATIONS-DESIGN BASIS DESIGN BASIS FLOW RATE-ECCS and RWCV Rooms-5 gpm----25 gpm RWCU PENETRATION ROOM.....Raise setpoints HPCI, RCIC Rooms.........Raise setpoints of Cooler Inlet Hi Ambient Trip i(', I'I 4" 14" 1q'C)p OBSERVATIONS

-RHR ROOMS 1.STEAM LEAK SETPOINT BASIS 2.ABSENCE OF STEAM SUPPLY 3.ISOLATION OF SHUTDOWN COOLING SUCTION 4.NO RE UIREMENT FOR SLD IN COLD SHUTDOWN 5.MINIiKU OVERLAP IN.HOT SHUTDOWN 6.PROPOSAL-ELIMiNATE ISOLATION FUNCTION OF SLD-REPLACE WITH TEMPERATURE BASED FUNCTION FOR SDC LEAkMGE OBSERVATIONS

-Rx BLDG 1MAJN STEAiVI TU'NOEL 1.FSAR-25 GPM DESIGN BASIS 2.ROOM COOLER MODELING DIFFICULTY Fraction of sensible vs latent heat removal under steam leak conditions Auto start of 2nd cooler at 13QF 3.INITIAL STUDIES-LEAKAGE AT RECTOR TEMPERATURE 4.FINAL STUDIES-.12,500 LBS-M/HR 5.APPLICATION OF SETPOINT CALCULATION METHODOLOGY

%ae.

OBSERVATIONS

-TURB BLDG iKAJN STEAIVl TUNNEL 1.ABSENCE OF CLOSED GEOMETRY 2.TEiVIPERATURK GRADIENT ALONG TUNNEL-3.SENSITIVITY OF TEMPERATURE TO LEAK LOCATION 4.INADEQUACY OF 25 GPM AS SETPOINT BASIS S.PRESENT OPERATION SUBJECT TO SPURIOUS ISOLATION DUE TO Sled%L 1VhWGIN 6.SYSTEM COVERS ONLY A SjVGu'PORTION OF MAIN STEAM PIPING IN TURBINE BUILDING.7.PROPOSAL-CO&iTERT ISOLATION FUNCTIONS TO FUNCTIONS ATTACHMENT B

~4 p'4 R k