ML17219A668

Forwards Response to Request for Info Required to Support Endorsement of Generic Ltr 86-06 Re Reactor Coolant Pump Trip 2/Leave 2 Criterion.Instrumentation Uncertainties Calculated Based on Adverse Containment Conditions

ML17219A668
Person / Time
Site:	Saint Lucie
Issue date:	07/01/1987
From:	Woody C FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
TASK-2.K.3.05, TASK-TM GL-86-06, GL-86-6, L-87-265, NUDOCS 8707070428
Download: ML17219A668 (8)

Text

REQULATO INFORMATION DISTRIBUTION STEM (RIDS)

ACCESSION. NBR: 8707070428 DOC. DATE: 87/07/01 NOTARIZED: NO DOCKET 0 FAC IL: 50&35 St, Lucie Plant> Unit ii Florida Power 5 Light Co. 05000335 50-389 St. Lucie Planti Unit 2> Florida Power 5 Light Co. 05000389 AUTH. NAME AUTHOR AFFILIATION NOODYi C. O. Florida Power h Light Co.

RECIP. NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk>

SUBJECT:

Forwards response to request for intro required to support endorsement of. Qeneric Ltr 86-06 re RCP Tri p 2/Leave 2 criterion for Wacilitg. Instrumentation uncertainties calculated based on adverse conditions in containment.

DISTRIBUTION CODE: A046D TITLE: OR Submittal: TMI COPIES RECEIVED: LTR Action Plan J ENCL J SIZE:

Rgmt NUREQ-0737 8. NUREQ-0660 NOTES:

RECIPIENT COPIES REC IP IENT COP IES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 0 PD2-2 PD 5 5 TOUR IQNYe E 1 INTERNAL: AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 ARM/DAF/LFMB 1 0 NRR/DEST/ADE 0 NRR/DEST/ADS 1 ~ 0 NRR/DREP/EPB 1 NRR/DREP/RPB 1 1 M LRB 1 1 OQC/HDS2 1 0 REQ FILE 01 1 1 RES DEPY QI 1 1 EXTERNAL: LPDR 1 NRC PDR NSIC 1 1 TOTAL NUMBER GF CGP IES REQUIRED: LTTR 22 ENCL 17

P. X 14000, JUNO BEACH, FL 33408 FLORIDA POWER 8E LIGHT COMPANY ANY 1 1S8l L-87-265 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gent lemen:

Re: St. Lucie Units I and 2 Docket Nos.50-33S and 50-389 Generic Letter 86-06 On May 29, l986, the NRC issued Generic Letter 86-06 (GL 86-06),

Subject:

"Implementation of TMI Action Item II.K.3.5, 'Automatic Trip of Reactor Coolant Pumps.' By letter L-87-S2, dated February l2, l987, Florida Power Bc Light Company provided the NRC a schedule of June 30, l987, for submitting all information required to support the endorsement of the GL 86-06 reactor coolant pump (RCP) trip 2/leave 2 criterion for St. Lucie Units I and 2. Attached is FPL s response to the information requested by GL 86-06.

If you have any questions about this submittal, please contact us.

Very truly yours, C. 0. Wood Group Vic President Nuclear Energy COW/E JW/gp Attachment cc: Dr. J. Nelson Grace, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, St. Lucie Plant O428 8O~o PQ OO03~5,'7Q7070Ocy AQ PQR P

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ATTACHMENT I PL RESPONSE TO GENERIC LETTER -06 IMPLEMENTATION RE UIREMENTS UESTION NUMBER 1 Identify the instrumentation to be used to determine the RCP trip setpoints, including the degree of redundancy nf each parameter signal needed for the criteria chosen.

RESPONSE

The St. Lucie Unit 1 and 2 Emergency Operating Procedures (EOP's) use the following instrumentation in determining RCP trip setpoints and diagnosing Reactor Coolant System (RCS) depressurization events: RCS pressure, steam generator pressure, containment pressure, pressurizer level trending, and the presence (or absence) of secondary plant radioactivity. Of these parameters, the most important is RCS pressure; an RCS pressure setpoint of 1300 psia is used to trip the first 2 RCP's during any uncontrolled RCS depressurization event. Steam generator pressure is used to distinguish Excess Steam Demand (ESD) events from LOCA's and SGTR's, and containment pressure is used to identify events in containment. Pressurizer level trending is used to help determine that the depressurization is not caused by heater or spray malfunctions, and the absence of secondary radiation is used to distinguish LOCA's from SGTR's.

In a strict setpoint sense, the RCS pressure signal is rigorously used to trip the first 2 pumps regardless of specific event diagnostics.

Its degree of redundancy for the instrument channels whose ranges are of interest here is:

St. Lucie Unit Sl St. Lucie Unit 02 4 channels! 1500 - 2500 psia 2 channels: 0 - 3000 psia 2 channels: 0 - 1600 psia 6 channels: 1500 2500 psia The parameters listed below, in conjunction with RCS pressure, are used to diagnose and distinguish LOCA and non-LOCA events. For LOCA events, all remaining RCP's are tripped promptly upon entering the LOCA EOP; for most situations, the first 2 RCP's will have already been tripped at an RCS pressure of 1300 psia. For non-LOCA depressurization events which can be definitely diagnosed, only the first 2 RCP's are tripped; for depressurization events which cannot be diagnosed, the Functional Recovery EOP requires tripping all RCP's at 1300 psia in order to protect against an undiagnosed LOCA.

CEN-268, "Justification of Trip Two/Leave Two Reactor Coolant Pump Trip Strategy During Transients," provides guidance regarding a decision process for tripping the second 2 RCP's based on RCS subcooling less than a specified value and no increasing radiation indication in the steam plant. The overriding philosphy of CEN-268, however, is that the second 2 RCP's should be tripped when a LOCA is diagnosed by whatever means are available. The NRC-approved CEN-152, "Combustion Engineering Emergency Procedure Guidelines," Figure 5-2, "Break Identification Chart,"

shows that, for LOCA events for St. Lucie, the loss of subcooling of the RCS coupled with the lack of steam plant radiation indication can be equated to maintaining secondary pressure above 750 psia coupled with the lack of steam plant radiation indication. Containment pressure is used in the Break Identification Chart as a decision point in aiding the operator to identify break location as either inside or outside containment. The St. Lucie EOPs use the latter criteria and setpoints (to be revised as indicated below) to distinguish between LOCA and non-LOCA event's.

Steam Generator Pressure - Current RCP trip setpoint is 800 psia.

Will be changed to CE's recommendation of 750 psia.

St. Lucie Unit 1 4 channels per S/G at 0 - 1200 psia 2 channels per S/G at 0 1000 psia St. Lucie Unit 2 4 channels per S/G at 0 - 1200 psia 2 channels per S/G at 0 1000 psia Containment Pressure Current setpoint is 2 psig. Will be changed to CE's recommendation of 4 psig.

St. Lucie Unit 1 1 channel, 0 - 50 psia St. Lucie Unit 2 1 channel, 0 15 psig 2 channels, 0 - 60 psig The other 2 parameters (pressurizer level and the absence of secondary plant radiation) are used in a qualitative sense rather than in a quantitative sense. Both parameters are used for trending, relative to normal or expected plant behavior. The degrees of redundancy associated with these parameters are:

Pressurizer Level St. Lucie Unit 1 5 channels St. Lucie Unit 2 6 channels Secondar Radiation St. Lucie Unit 1 and Unit 2 S/G Blowdown: 1 channel per S/G Steam Line Monitor: 1 channel per S/G Steam Jet Air Ejector: 1 channel UESTION NUMBER 2 Identify the instrumentation uncertainties for both normal and adverse containment conditions. Describe the basis for the selection of the adverse containment parameters. Address, as appropriate, local conditions such as fluid jets or pipe whip which might influence the instrumentation reliability.

RESPONSE

Instrumentation uncertainties have been calculated based on adverse conditions in the containment. Local conditions such as fluid jets and pipe whip have not been factored into this evaluation since the high degree of instrument redundancy and the diverse locations of the various instrument channels provides control room operators with adequate information to diagnose events and to trip RCP's as appropriate.

e The adverse containment temperatures considered were based on the containment 'hermodynamic response to small break LOCA's and ESD's up to the time when operator actions are directed based on, for example, low RCS pressure. The most restrictive of these temperatures was used in the evaluation of the adverse total instrument channel errors.

The temperatures considered and the basis for them are as follows:

Basis Tem erature Small Break LOCA, RCS pressure 168'F decreases to 1300 psi Small Break LOCA, 135 F increases psi Containment'ressure by 2 ESD, pure steam, 175 F Containment pressure increases by 2 psi As a conservatism, even though ESD events are not the events which require all RCP's to be tripped, the value of 175'F was used as the basis for all adverse instrument error calculations.

For St. Lucie Unit 1 and 2, the limiting instrument channel errors corresponding to this temperature have been determined as listed below:

Pressurizer pressure: +191.8, -133.9 psi Steam generator pressure: +134.1, -112.9 psi Containment pressures +1.6 psi As previously mentioned, numerical errors were not evaluated for pressurizer levels or for secondary plant radiation monitors due to the qualitative manner in which these parameters are used in the RCP trip and event diagnostic processes. The calculated errors referenced above have been evaluated in terms of plant transient behavior and the EOP steps which are based on these parameters. The evaluation has shown that there is sufficient margin to plant safety when the errors are added to or subtracted from the plant data and then compared to the EOP directed operator action values.

UESTION NUMBER 3 In addressing the selection of the criterion, consideration of uncertainties associated with the CEOG supplied analyses values must be provided. These uncertainties include both uncertainties in the computer program results and uncertainties resulting from plant specific features not representative of the CEOG generic data group.

RESPONSE

The CEOG supplied analyses of CEN-268, "Justification of Trip Two/Leave Two Reactor Coolant Pump Trip Strategy During Transients", March 1984, provided a conservative setpoint of 1210 psia for tripping the first 2 Reactor Coolant Pumps. This value did not address instrument

uncertainties. As discussed in Supplement 1-P to CEN-268, "Response to NRC Request for Additional Information on CEN-268", November 1984, the value of 1210 psia is conservatively based on the establishment of a quasi-steady state RCS pressure plateau after the secondary pressure has stabilized, after RCS subcooling has been lost, and before the postulated break location is uncovered. The derivation of the 1210 psia value is based on a steady state energy balance in the RCS under these conditions. The energy balance is established in terms of decay heat, primary to secondary heat transfer, coolant flow out the break, HPSI flow into the RCS, and assumed secondary pressure. Conservatively biasing these values resulted in 1210 psia as the value of the RCS pressure plateau established under these limiting conditions. By contrast, the non-biased transient calculations show pressure plateaus of about 950 psia and 1050 psia when the secondary pressure is at 900 psia (via Steam Bypass Control System) and 1000 psia (via Main Steam Safety Valves) respectively. The nature of the energy balance thus established is such that all of these values are accurate to within about 10 psia. The only plant specific features of the St. Lucie Unit 1 and 2 plants which are different from the data used for these calculations are the HPSI flow characteristics. Both units have higher HPSI flow capabilities than those used in the CEOG analyses, so that the pressures quoted would be slightly lower due to increased cooling if the increased HPSI flows were used. However, this is a relatively minor contribution to the energy balance, so that the CEOG analyses regarding these pressures are very representative and slightly conservative relative to the St. Lucie units.

The St. Lucie Units 1 and 2 EOP's have established 1300 psia as the operator directed value for tripping the first 2 RCP's. This value with adverse instrument errors considered is conservative relative to either the 950 psia or the 1050 psia pressure plateaus which will be realistically established for small break LOCA's. For example, using 192 psia as the adverse pressurizer pressure error provides margins of 1300 (950 + 192) = 158 psi and 1300 (1050 + 192) = 58 psia for tripping the first 2 pumps. These are adequate margins, as the establishment of the pressure plateau occurs fairly rapidly for the break sizes of interest (about 2 minutes for the 0.1 ft case), but lasts relatively long (about 10 minutes for the same case). Hence, the establishment of the plateau plus operator reaction time (used as 30 seconds in CEN-268) allows sufficient time to trip the pumps before the time when continued pump action would keep the break covered and thus cause undue RCS inventory loss.

UESTION NUMBER 4 Identify all plant procedures (except those concerning normal operations such as normal cooldown) which require RCP 'trip guidelines. Reference to the CEOG EPG's is acceptable if endorsed by the licensee. Include training and procedures which provide direction for use of individual steam generators with and without operating RCP's.

RESPONSE

The plant procedures which require RCP trip guidelines are:

1-EOP-04 S/G Tube Rupture 2-EOP-04 S/G Tube Rupture 1-EOP-05 Excess Steam Demand 2-EOP-05 Excess Steam Demand Procedures which provide direction for use of individual steam generators with and without RCP's are:

1-EOP-03 Loss of Coolant Accident 2-EOP-03 Loss of Coolant Accident 1-EOP-06 Total Loss of Feedwater 2-EOP-06 Total Loss of Feedwater 1-EOP-07 Loss of Forced Circulation 2-EOP-07 Loss of Forced Circulation 1-EOP-08 Functional Recovery 2-EOP-08 Functional Recovery The events requiring the use of EOP's and the EOP's themselves are simultaneously addressed in a St. Lucie Plant Training Department Lesson Plan which is presented as a part of the operator's initial licensing and training. All EOP's are covered extensively in the classroom and are exercised during simulator training.