ML14138A103
| ML14138A103 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/24/1982 |
| From: | Paulson W Office of Nuclear Reactor Regulation |
| To: | Dietch R Southern California Edison Co |
| References | |
| TASK-06-07.B, TASK-6-7.B, TASK-RR LSO5-82-11-077, LSO5-82-11-77, NUDOCS 8211300351 | |
| Download: ML14138A103 (19) | |
Text
November 24, 1982 Docket No. 50-206 LS05-82-11-077 Mr. R. Bietch, Vice President Nuclear Engineering and Operations Southern California Edison Company 2244 Walnut know Avenue Post Office Box 800 Rosemead, California 91770
Dear Mr. Dietch:
SUBJECT:
SEP TOPIC VI-7.B, ESF SWITCHOVER FROM INJECTION TO RECIRCULATFON (AUTOMATIC ECCS. REALIGNMENT)
SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1 Enclosed is the staff's final safety evaluation of SEP Topic VI-7.B.
As described in the evaluation, your comments on the draft evaluation have been considered; however, we cannot conclude that the present design provides adequate assurance that manual switchover will be completed in a timely manner.
The need for design changes will be addressed in the integrated safety assessment for your facility. This topic evaluation may be revised in the future if your facility design is changed or if NRC critertdarela ting to this topic are modif1id before the integrated assessment is completed.
Sincerely, Walter Paulson, Project Manager Operating Reactors Branch No. 5 Division of Licensing
Enclosure:
cA As stated cc w/enclosure:
(
iy See next page 8211300351 821124 PDR ADOCK 05000206 P
. E f f... DR.~S S--.g...
O OFFICEI0 P
BSEBOR#
EMcKenna:bl1 CGrimes WRussell WPaulson DC.d sURNAME 11E~l/40182 11 ~/82 11ly/8 j II / 82 i(77t DAT..)
- 2 ****
O FFI
- IA.L...
R E.C.O.....R...D......
C O P NRC FORM 318 (10-80) NROM 0240 OF FICIAL RE CO RD CO PY USGPO: 1981-335-960
San Onofre Unit 1 Docket No. 50-206 cc Charles R. Kocher, Assistant General Counsel James Beoletto, Esquire Southern California Edison Company Post Office Box 800 Rosemead, California 91770 David.R. Pigott Orrick, Herrington & Sutcliffe 600 Montgomery Street 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 Mayor City of S 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:
Regional Radiation Representative 215 Freemont Street San Francisco, California 94111 Robert H. Engelken, Regional Administrator Nuclear Regulatory Commission, Region V 1450 Maria Lane Walnut Creek, California 94596
S SYSTEMATIC EVALUATION PROGRAM TOPIC VI-7.B SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1 TOPIC: VI-7.B, ESF Switchover from Injection to Recirculation (Automatic ECCS Realignment)
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 automati cally started to provide containment spray at a rate of 1,513 gpm.
Water supply for safety injection and containment 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 RWST level reaches 12%, then the water supply is transferred from the RWST to the sump. Prior to the transfer of the water supply, the injection flow is considerably reduced, by manual trip of the safety injection and feedwater pumps, on low-level (21%) in the RWST. The switchover to sump suction should be completed before the RWST level drops to 7% to assure suffi cient NPSH and vortex suppression. During the recirculation phase the recirculation pumps provide sump water to the charging pumps, for in jection 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 in jection and recirculation modes of the safety injection systems for San Onofre Unit 1.
II. REVIEW CRITERIA The plant design was reviewed with regard to Appendix A, 10 CFR 50, General Design Criteria 35, "Emergency Core Cooling," which requires that a system to supply abundant emergency core cooling be provided.
III.
RELATED SAFETY TOPICS AND INTERFACES The scope of review for this topic was limited to avoid duplication of effort since some aspects of the review were performed under related topics. The related topics are identified below:
-2 111-6 Seismic Design Considerations III-10.A Thermal-Overload Protection for Motor-Operated Valves IIT-11 Component Integrity III-12 Environment Qualification VI-7.C ECCS Single Failure Criterion VI-l.A Testing of ESF System VII-2 Engineered Safety Features (ESF) System Control Logic and Design IX-4 Boron Addition System XV-19 Loss-of-Coolant Accidents Resulting From Spectrum of Postulated Piping Breaks Within the Reactor Coolant Pressure Boundary IV. REVIEW GUIDELINES This review is conducted in accordance with SRP 6.3, "Emergency Core Cooling System," Regulatory Guide 1.62, "Manual Initiation of Protec tion Actions," and Branch Technical Position ICSB 20, "Design of Instrumentation and Controls Provided to Accomplish Changeover from Injection to Recirculation Mode."
These guidelines state that automatic transfer to the recirculation mode is preferable to manual transfer and should be provided for standard plant designs submitted for review on a generic basis under the Commission's standarization policy.
They also stateithat a design that provides manual initiatton at the system level of the transfer to the recirculation mode, while not ideal, is sufficient and satisfies the intent of IEEE Std. 279 provided that adequate instrumentation and information display are available to the operator so that he can make the correct decision at the correct time. Furthermore, it should be shown that, in case of operator error, there is sufficient time and information available so that the operator can correct the error, and the consequences.of such an error are accep table.
Item 19 of the review procedures in SRP Section 6.3 states that the complete sequence of ECCS operation from injection to long term core cooling (recirculation) is examined to confirm that a minimum of manual actions is required and that where manual action is needed, sufficient time (about 20 minutes) is available for the operator to respond.
Further guidance on timing of operator actions is provided by draft ANSI Standard N660.
V.
DISCUSSION On July 24, 1981 (Reference 1), the staff issued a safety evaluation on systems aspects of this topic which may be summarized as follows:
Upon safety injection (SI) initiation, a maximum flow rate of 22,405 gpm from the RWST can occur. By procedure, upon detection of either low RWST level (21%) or high containment sump level (-3 feet), the operator is instructed to terminate safety injection flow (by tripping the feedwater and SI pumps) within 30 seconds, which would reduce the flow out of-the tank to a maximum of 1877 gpm. Switchover to sump suction should be completed before the RWST level drops to 7%.
From detection of the need to initiate reduced-flow injection until level drops to 7% takes about 10 minutes.
Assuming an additional 30 second delay in tripping the feedwater pumps would reduce to time to less than 6 minutes. The staff concluded that the manual switchover procedure was intolerant of small time delays; and-therefore, that automatic features to assure early interruption of flow should be provided.
On September 4, 1981 (Reference 2), the staff issued an evaluation of the instrumentation provided to the operator for switchover operation which may be summarized as follows:
Two instruments, a pneumatic indicator (LI-950) and a level switch alarm (LS-69) (powered by Train A), are provided for RWST level.
Containment sump level is monitored by indicating lights (Train A) and a level switch alarm (Train A).
In addition, two new instruments, powered by independent Class 1E channels are being provided.
The staff concluded that the instrumentation provided did not satisfy the single failure criterion, although the new sump level instruments were a significant improvement. The staff recommended that redundant Class 1E instrumentation be provided for the RWST level.
By letter dated January 26, 1982 (Reference 3) the licensee, Southern California Edison Company, provided comments on the July 24, 1981 evaluation. These comments modified some of the flowrates and time estimates but did not alleviate the staff concern on the time frame available for operator action.
By letter dated September 13, 1982 (Reference 4), the licensee provided copies of Emergency Operating Instructions including those for loss-of coolant accidents and switchover. A key point to be noted in these procedures is that the operator is instructed to reduce flow and initiate recirculation based on RWST level.
No mention is made of sump level.
Therefore, the operator relies on the two RWST level instruments discus sed above. Applicable portions of these procedures are attached.
-4 VI.
EVALUATION Assuming a single failure of one i'nstrument, the operator would be alerted to initiate switchover by the RWST low-low-level alarm CLS-69).
From Reference 5, the setpoint would be reached at 503.1 seconds when the volume remaining in the tank is 53,306 gallons Cassuming a flow rate of 22,405 gpm and initial tank volume of 241,172 gallons). At this time, the operator trips the feedwater and SI pumps and begins realignment of charging pump flow through SI injection lines. Assuming SY and feed pump flow is terminated within 30 seconds of the alarm, it would take about 5.1 minutes to reach an RWST level of 12% (32,472 gal.), assuming flow rate of 1877 gpm, which corresponds to two refueling water pumps and 330 gpm of charging flow. The operator starts the second charging pump as part of this sequence of actions, which would increase charging flow to 600 gpm. There are over twenty individual valve manipulations and other actions that must be done during this 5 minute period including some local actions.
The operator is instructed to monitor RWST level and, when the level has dropped to 12%, to establish recirculation flow from the sump.
However, given a failure of LI-950, this indication would not be available for the operator. Other indications of a large break LOCA extst, such as increasing sump level, which would suggest that switch over is needed; however, the operator could act at the wrong time. A switch to sump suction either too early or too late could result in damage to the pumps.
The coTd-leg recirculation initiation procedure requires that the re circulation pumps be run against closed discharge valves for two minutes. Other valve and pump manipulations are also specified. During this sequence, one of two refueling water pumps is tripped, which re duces the flow rate out of the tank and thus increases the available time.
To ensure adequate NPSH and vortex suppression, suction from the RWST should be terminated before the level drops below 7% (18,644 gal.).
The time to reduce RWST from 12% to 7% would range between 5.8 minutes and 10 minutes depending on the flow rate assumed.
The following cases were considered:
TIME:
2 charging pumps, 2 refueling water pumps (2147 gpm) 5.8 min.
1 charging pump, 2 refueling water pumps (1877 gpm) 6.7 min.
2 charging pumps, 1 refueling water pump* (1373 gpm) 10.0 min.
- Flow rate corresponding to 1/2 of 2 pumps flow was assumed.
-5 VII. CONCLUSION To summarize, from receipt of the low-low RWST level alarm until the tank level drops to 7% will take on the order of 10 - 15 minutes, assuming the feed pumps are tripped within 30 seconds of the alarm. During this time, many operator actions must be performed. In particular, the operator is directed to proceed with a given sequence of actions when RWST level drops to 12%; however, given a single failure, this indication may not occur. Considering the number of actions that must be performed, the time frame available, and the potential consequences of failure, we cannot conclude that the present design provides adequate assurance that manual switchover will be accomplished on a timely basis. Therefore, we recommend that automatic features be provided to terminate injection flow and initiate switchover on low tank level.
VII. REFERENCES
- 1. Letter to R. Dietch (SCE), from D. M. Crutchfield (NRC),
dated July 24, 1981.
- 2. Letter to R. Dietch (SCE), from D. M. Crutchfield (NRC),
dated September 4, 1981.
- 3. Letter to D. M. Crutchfield (NRC), from R. Krieger (SCE),
dated January 26, 1982.
- 4. Letter to D. M. Crutchffeld (NRC), from K. P. Baskin (SCE),
transmitting San Onofre 1 Emergency Operating Instructions, dated September 13, 1982.
- 5. Letter to Stan Nowicki (NRC), from W. C. Moody (SCE),
"ECCS Switchover to Recirculation," dated August 18, 1980.
FIC~~-cuTr el I cL'T~C7ip\\
LooC t~IA OF~
.4V
'R A
N S i
Mt~
CL 6 FXVikMDV 1-41 0 ~~
~ ~
f_
oL~OGP A.-
Mx.IN----tvx/v1100--3 CLGV~'
RIEGL401PTILJG IIlle LC V ~O 1 LQHXO~
- TAMjK, sp~vcvii c L
- 1+
CV11 (A-M04Trn CL..
mK tI~ l
+~ recbc
-IV\\ On~o rZ reue pe cauJItk
'4AT4<
TArJ V Accl Cviii ICL~
CuG Mo'I3_
fcfIIADCARQI' CL
~~MOV-14M 1
A~A
TRANSFER TO COLD LEG INJECTS REV 0 AND RECIRCULATION PURPOSE The purpose of this instruction is to provide a method to terminate safety injection after a LOCA where the RWST level has dropped below 27% and to provide recirculation of the spilled coolant from the containment sump back to the RCS and containment sprays.
I of 9
Sol-1.1-9 TRANSFER TO COLD LEG INJECTION REV 0 AND RECIRCULATION ACTION/EXPECTED RESPONSE RESPONSE NOT OBTAINED I
VERIFY SI RESET:
- a. Verify SLSS surveillance
- a.
Reset SI at SLSS panel load group lights surveillance panels.
ON.
- b. Verify lockout switches
- b.
Manually reset
- RESET.
lockout switches.
2 STOP Feed And SI Pumps:
- a. Stop both feed pumps.
- b. Stop both SI pumps.
2 of 9
501-1.1-9 TRANSFER TO COLD LEG INJECTION REV 0 AND RECIRCULATION
,,,,ACTION
/E XPEC TED RESPONSE REPNENOT OBTAIE 3
ALIGN SI Yalving To Standby Status:
- a.
lMOV 850 A - CLOSE.
MOV 850 B - CLOSE.
MOV 850 C - CLOSE.
- b. KV 851 A - CLOSE.
HV 851 B - CLOSE.
- c.
HV 853 A - CLOSE.
HV 853 B - CLOSE.
- d. CV 875 A - CLOSE.
CV.875 B - CLOSE.
- e.
SV 2900 -
CLOSE.
SV 3900 - CLOSE.
- f.
Locally close bonnet vent block valves:
HY 853 A - CLOSE.
HV 853 B - CLOSE.
3 of 9
501-1.1-9 TRANSFER TO COLD LEG INJECTION REV 0 AND RECIRCULATION S..
,ACTION/EXPECTED RESPONSE NOT OBTAINED 4
STOP Automatic Make Up:
- a. Depress automatic make
- a. IF automatic make up up stop pushbutton.
NOT stopped, THEN place boric acid selector switch out of AUTO.
CAUTION Do not exceed 600 GPM with two charging pumps or 330 GPM with one charging pump to avoid potential damage to the charging pumps.
5 ALIGN Charging Flow Path Through the S5 Cold Leg injection Lines:
- a.
Place RCP seal supply flow controllers in MANUAL AND maintain previous valve position.
- b. Align cold leg injection flowpath:
MOV 356 - OPEN.
MOV 357 - OPEN.
MOV 358 - OPEN.
MOV 18 -
OPEN.
MOV 19 -
OPEN.
4 of 9
TRANSFER TO COLD LEG INJECTION REV 0 AND RECIRCULATION 2P ACTIO/EXPCTED ESPOSE RESPONSE NOT OBTAIE 6VERIFY Charging Flow Lapability:
- a. Verify reset non running charging pump lockout.
- b. Start second charging
- b. IF second charging pup pump.
pump NOT available, THEN go to step 7 c.
5 of 9
TRANSFER TO COLD LEG INJECTION REV 0 AND RECIRCULATION
- fACTION /EXPECTED RESPONSE11 RESPONSE NOT OBTAINED 7
ESTABLISH Flow Through The 51 Cold Leg Injection Lines:
- a. With two charging pumps
- IF unable to establish running:
flow due to instrument
- air, Isolate normal charging:
CLOSE FCV 1112 THEN.place backup seal CLOSE CV 304 supply flow AND controllers in service ThrottlieTCP seal supply flow For each controller:
controllers to achieve if possible:
- 1. Place aux nitrogen Three injection lines s
switch -
ON.
200 GPM PER LINE,
- 2. Place aux position OR control switch - ON.
Two injEtion lines 300 GPM PER LINE
- 3. Adjust aux controller to obtain desired
- b. Go to step 8.
flow.
- c. With one charging pump
- 4. Place aux position running:
control switch - OFF.
Isolate normal charging:
- 5. Repeat 2, 3, AND 4 for CLOSE FCV 1112 any further flow CLOSE CV 304 adjustments.
AND ThrottlTCP seal supply controllers to achieve if possible:
Three injection lines 110 6PM PER LINE.
OR Two injec!Ton lines 165 GPM PER LINE.
6 of 9
S01-1.1-9 TRANSS TO COLD LEG INJECTION EV 0' AND RECIRCULATION STEP ACTION/EXPECTED RESPONSE NOT OBTAINED 8
DISABLE Residual Heat Exchanger Inlet MUVs:
- a. Open MOV 822 A AND locally open breaker 42-1164.
- b. Open MOV 822 B AND locally open breaker 42-1266.
9 MONITOR RWST Level:
- a. Check RWST level - LESS
- a. IF RWST level -
GREATER THAN OR EQUAL TO 12%.
THAN 12%
THEN wait until RWST level decreaies to 12%
AND go to stej7O of this procedure.
7 of 9
01-1.1-9 TRANSFER TO COLD LEG INJECTION REY 0 AND RECIRCULATION ACIO/XPCEDREPNS ESPONSE NOT OBTAINED 10 Establish Cold Leg Recirculation:
- a. Start both recirculation pumps AND run for twoT2) minutes against closed discharge valves.
- b. Adjust cold leg injection flow to 330 GPM.
- c. Verify two CCW pump C.
Manually start pumps.
breakers - CLOSED.
- d. Verify one saltwater
- d.
Manually start pump.
cooling pump breaker
- CLOSED.
- e. Open recirculation heat
- e.
Locally trip open exchanger CCW valves CV 737 A and B.
CV 737 A and B.
- f. Close CV 577 and
- f.
Locally trip closed CV 518.
CV 517 and CV 518.
- g. Verify one (1) refueling
- g. IF both refueling water water pump running.
pumps are running, THEN stop one (R) pump.
- h. Open recirculation pump discharge valves MOY 866 A and B.
- f.
Close NOV 883.
- 1.
Locally close NOV 883.
8 of 9
SOl-1.1-9 TRANSFIWTO COLD LEG INJECTION VEE 0 AND RECIRCULATION A CTION / EX PE C T ED R E SPON S E R
RESPON SE NO078T BA IN ED 11 REDUCE Intection Flow Dne Hour After 51 Recirculation Is Established:
- a. Throttle seal supply flow controllers to maintain:
Three injection lines
- 70 GPM PER LINE.
OR Two injectTin lines 105 GPM PER LINE.
12 SUBSEQUENT Action:
- a. Continue with procedure in effect.
-END H. E. MORGAN MANAGER, STATION OPERATIONS 025A 9 of 9