ML14133A562

Forwards Draft Evaluation of SEP Topic VI-7.B Re Engineered Switchover from Injection to Recirculation Mode (Automatic ECCS Alignment). Info Re Differences Between as-built Facility & Evaluation Requested within 30 Days

ML14133A562
Person / Time
Site:	San Onofre
Issue date:	07/24/1981
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:	Dietch R Southern California Edison Co
References
TASK-06-07.B, TASK-6-7.B, TASK-RR LSO5-81-07-083, LSO5-81-7-83, NUDOCS 8107300037
Download: ML14133A562 (12)

Text

0 UNITED STATES SoNUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 July 24, 1981 Docket 50-206 LSO5 07-083 Mr. R. Dietch, Vice President Nuclear Engineering and Operations Southern California Edison Company ro 2244 Walnut Grove Avenue Post Office Box 800 Rosemead, California 91770

SUBJECT:

SEP TOPIC VI-7.B., ESF SWITCHOVER FROM INJECTION TO RECIRCULATION MODE (AUTOMATIC ECCS ALIGNMENT) - SAN ONOFRE 1 Enclosed is a draft evaluation of SEP Topic VI-7.B for San Onofre Unit 1.

This evaluation compares your facility with the criteria currently used by the regulatory staff for licensing new facilities. Please inform us if your as-built facility differs from the licensing basis assumed in our assessment within 30 days of receipt of this letter.

This evaluation will be supplemented upon receipt of your response to our request for information on this topic dated March 4, 1981.

We encourage you to supply for the docket any other material related to this topic that may affect the staff's evaluation.

Sincerely, Dennis M. rutc field, Chi Operating Reactors Branch No. 5 Division of Licensing

Enclosure:

As stated cc w/enclosure:

See next page

Mr.-R. Dietch cc Charles R. Kocher, Assistant General Counsel James Beoletto, Esquire Southern California Edison Company Post Office Box 800 Rosemead, California 91770 David R. Pigott Chickering & Gregory Three Embarcadero Center Twenty-Third Floor San Francisco, California 94111 Harry B. Stoehr San Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 Resident Inspector/San-Onofre NPS c/o U. S. NRC P. 0. Box 4329 San Clemente, California 92672 Mission Viejo Branch Library 24851 Chrisanta Drive Mission Viejo, California 92676 Mayor City of San Clemente San Clemente, California 92672 Chairman Board of Supervisors County of San Diego San Diego, California 92101 California Department of Health ATTN: Chief, Environmental Radiation Control Unit Radiological Health Section 714 P Street, Room 498 Sacramento, California 95814 U. S. Environmental Protection Agency Region IX Office ATTN:

EIS COORDINATOR 215 Freemont Street San Francisco, California 94111

SAN ONOFRE 1 ENCLOSURE ESF SWITCHOVER FROM INJECTION TO RECIRCULATION MODE (VI-7.B.)

I.

Introduction Following a loss of coolant accident (LOCA), safety injection is automatically initiated by a safety injection signal (SIS). The signal starts two safety injection pumps, two feedwater pumps and one charging pump; all contributing to the injection of reactor coolant at a rate of 20,892 gpm. Additionally,

'the two refueling water pumps are automatically started to provide containment spray at a rate of 1,512 gpm.

Water supply, for safety injection and contain ment spray, is initially provided by the refueling water storage tank (RWST).

Injection of reactor coolant and containment spray, with water supply from the RWST, continues until the water level in the containment sphere sump rises to-2 ft or the RWST level reaches 12%, then the water supply is transferred from the RWST to the sump.

Prior to the transfer of the water supply, however, the injection flow is considerably reduced, by manual trip of the safety injection and feedwater pumps on a low-low level alarm in the RWST.

The switchover should be completed before RWST level drops to 7%.

During the recirculation phase the recirculation pumps provide sump water to the charging pumps, for injection to the reactor coolant system and also provide sump water to the refueling water pumps for containment spray.

Figures 1, 2 and 3 respectively depict the injection, reduced-flow injection and recirculation modes of the safety injection systems for San Onofre Unit 1.

-2 II. Evaluation The switchover from injection to the recirculation mode is a fully manual procedure that requires an extremely precise execution of manual actions, by the operator, in order to assure no significant interruption of reactor coolant and containment spray following a design basis LOCA.

The applicable sections of the procedures that were submitted in Reference 2 are attached.

Emergency procedures issued to tne operator require termination of safety injection (20,562 gpi) within 30 seconds following receipt of a second indi cation/alarm of low level in the RWST, or sump level indication/alarm. We have assumed that the sump alarm fails to activate and the second alarm will be the lo-lo level on the RWST which will activate at a level of 20.8( 49,989g)..

nerefore. we have calculated that in 30 seconds the R level wi1 be reduced to 16 (33.7879).

Subsequent instructions to the ourator recuire re-establish ent Co c-C e

oinectiron w n I onree 2inues 0n

'ermiEaeion 0Z s7usty injection, by re-alignment of valves and starting of the second c ha rging p oume.

in three minutea, fo lowing termination c safety in.iCtiCn.

e have calculated the RWST level to be reduced to 13.8': as a result of the continued discharce of the two refueling water pumps and one charginO pump (1,840 qpm).

At the re establishment of cold-leg injection the discharge rate from the RWST will be 2,170 qpm and the final re-aliqnment to the sump must be completed before the water level in the R.'ST drops to 7, (16,800g).

The time available to the operator, therefore, to complete the final re-alignment is 7.5 minutes.

-3 In order to determine the effect of a continued safety injection flow on the minimum level in the RWST, we have assumed an additional 30 seconds delay before the operator interrupts safety injection. With the additional 30 seconds delay our calculations reveal that the available time for the final re-alignment of recirculation to the sump is reduced to a total of 2.4 minutes.

During these 2.4 minutes, the operator is required to operate the recirculation pumps for at least two minutes against closed discharge valves, to ensure that air is vented from the system.

Therefore, isolation of the RWST will commence at a water level in the RWST significantly lower than the critical level of 7%.

The isolation of RWST is the eighth arid last step of the re-alignment procedure.

III.

Conclusion As Dart of the SEP review for San Onofre, we have evaluated the licensee's safety injection system design (Ref.

1),

emergency procedures (Ref. 2) and additional submittal (Ref.

3) against the criteria of SRP Section 6.3, Branch Technical Position RSB 6-1, and have concluded that the design is in conformance with those criteria.

However, we have determined that the manual procedures, for swi tchover from injection to recirculation, are intolerant to small time delays in interruption of safety injection and therefore we recommend that the manul

-ocedure

-or interruotion of safety injection be realaced by automatic features that assure early interruction, such as automatic feedwater nup trip on low RWST level.

comparative risk assessment study conducted by the staff (Ref. 4) has demonstrated that automatic features enhance switchover reliability by at least an order of magnitude.

REFERENCES

1. Southern California Edison Company, "Final Safety Analysis Report, San Onofre Nuclear Generating Station Unit l," Docket No. 50-206.

2. Southern California Edison ComDany, "Operating Instruction 5-3.4.4 Emergency, San Onofre Nuclear Generating Station Unit 1," Revision 18, dated February 27, 1980.

3.

Memo to Stan Nowicki (NRC) from W. C. Moody (SCE),

Subject:

ECCS Switch over to Recirculation, dated August 18, 1980.

4. Memorandum for NRR Division Directors (NRC) from H. Denton (NRC),

Subject:

NRR Mlonthly Technical Report for Marach 1981, dated April 16, 1981.

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Attachment Revisi o EMERGE FE 2 7 1923 B.

LOSS OF REACTO. COOLANT (Cond't) 4.0 SUP-SE1j4OnT OERATOR ACTIONS (Cond't) 4.111.3 if the main condenser-is not is service. du-mp:

steam to th~e atmnospzre. with the StEam durnp to atmocsphere relief val -es to 4oe the reactor cooant temperature and consecuen y the reactor coolant pressure.

4.12 Monitor delivery of refueling water to the reactor coolant sYstem.

As Ievell approach-e s 2,-'i~ in the 'A,,S7( L 1-950), antic-i Pate recei pt the folo oc

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Upon receipt of any two, reset and terminate safety injection as per Step 4.13 below.

CAUTI0 Safety injection flow shOLld be terminated within 30 seonds following receipt of the second indication to insure sUo

• iuer:

inventory for containment spray.

4.12.1 Containmefnlt zwhere sump level above -4' as indicated by LI-95.

4.12.?

Containment sphere sump w-ter level at -3' as indicated bt the sphere sump nih-nih level alarm.

4.12.3 Refueling water storage tank level at 21% as indicatet on LI-950.

4.1.4 Re-uelin water tank low-low level alarm.

4.13 Reset Safety Iniection.

4.13.1 Terminate Safety njection flow.

.1 Reset sequencers at SLS5 surveillance panels.

.2 Stop east and west.feedwater pumps.

.3 Stop east and west safety injection pumps.

4.13.2 Isolate Safety Injection lines.

.1 Close MOV-850 A, B and C.

.2 Close HV-851 A and B.

.3 Close HY-853 A and B.

.4 Verify CV-875 A and B close automatically.

4.14 Stop automatic make-up or dilution.

LATIOT 1E' OPERAT ING U

S SAN 0.C NUCLE R E

lEMAERGENCY Pa a 9

Rev isin FES 2 7 19^1

o. c nO O REACTOP COOLANT (Cond't) 4.0 S U E!,7UE REATOR ACT 10S (Cond't) 4.15 Re-estzblish cold leg inject-Of witon n 3 minuteS of teyiflatifg safety injection flow:

4.15.1 Place MuV.-1100S and 110CD control out-of-auto and open.

4.15.2 Place MOV-1100C control out-of-auto and close.

4.15.3 Place FO-1115A, B and C on manual and close FCv-111A, P, C, D, E and F.

4.15.4 Open MCV-356,

357, 35S, 1& and 19.

-4.15.5 Start the second charging pump.

4.15.6 Close FCV-1112.

4.15.7 Open FCV-1115D, Eand F tc establish 110 om to each of Loop A, Loop B and Loop C.

I o f t e estaothir stw t in one line, set the flow to ea h of the ng r tpo lowo at-165 cnm..

Do not exceed a total charg-ing pump flow of 330 ;pm tEcausC of potentiai damage to charging pumps.

.5. 3 If instrument air is :cst to F lED E and F place back-up ranual contro'1ers in service.

1 Place Position Control Switch in "ON".

.2 Place Auxiliary Air Control Switch in "ON".

.3 Adjust flow as described in 4.15.7 above using the 'anual Control Station.

.4 After flow has been set, place Position Contrl Switch in, "OFF" position. This will lock valve in Position andi reduce nitrogen requirement.

.5 To charge flow, again place Position Control Switch in "zON", make flow change and place switch in "OFF".

4.16 Open thne safety switch to the inlet MOV of the inservice residual heat exchanger(s) to prevent inadvertent operation due to flooding.

4.16.1 East HX MOV-822A (42-1164).

4.16.2 West HX MOV-822

(.42-1266).

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.ANO~QPEEMERGENCY Pa % 20 Revision 17 S. LOSS OF REACTOR COOLANT (Cond't) 4.0

-SSE RT CPERAOR ACTIONS (Cohd't) 4.17 gcin alicnment of the safety injection recrculation system, when the Rle-T level is less than 12',, as iridi!_ated on. LI-950 oz-sphere SuMp lEvel is at/cr above -2' as indicated on sphere water level indica tng lights, LT-951 CAUTI: Complete switchever to 5.1. recirculation before RWST level reaches 7-on LI-950. This insures that adequate %PSH to the refueling water and charging pumps wilI be maint.ined.

RWST level will drop from 124 to 75-in about 5 minutes.

4.17.1 Start east and west S.I. T-ecirc. pumps.

NOTE:

Pumps should be run for at least 2 minutes against closed dischargE ValveS to insure air is vented from system.

4.i7.2 Verify that at least two component cooling water purps are running.

4.17.3 Verify that at least one salt water cooling pump is running.

4.17.4 Open the recirc. heat exchanger cooling water valves V's 737 A and 3.

4.17.5 Override and close CV's 517 and 518, reducing containment spray.

4.17.6 Stop one refueling water pump if both pumps are running.

4.17.7 Open MOV's S6E A and S, thus establishing recirc. flow.

4.17.8 Close MOV-88.3, refueling water tank outlet valve.

4.18 Periodically check auxiliary building area radiation monitOrs for detectcn of leakage from ECCS during recirculation. If significant leakage has been identified in the ECCS, attemot to isolate the leakage. The.operator MUST maintain recirculation flow to the RCS at all times.

4.19 If off-site power is available, stop Diesel Generators No. 1 and No. 2.

4.20 One hour after initiation of safety injection, reduce injection flow via MOV-356, 357 and 358 to 70 gpm to each loop. If flow is to two loops only, set flow at 105 gpm to each loop.

Do not exceed 210 gpm total flow.