ML13330A406
| ML13330A406 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/18/1981 |
| From: | Baskin K Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TAC-44652 NUDOCS 8111200582 | |
| Download: ML13330A406 (15) | |
Text
Southern California Edison Company P. 0.
BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD. CALIFORNIA 91770 K. P. BASKIN TELEPHONE MANAGER OF NUCLEAR ENGINEERING, November 18 1981 (213) 572-1401 SAFETY, AND LICENSING 1v02 0 1981b Director, Office of Nuclear Reactor Regulation Attention:
D. M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Automatic Initiation of the AFWS - Amendment No. 97 San Onofre Nuclear Generating Station Unit 1
References:
(1) K. P. Baskin letter to D. M. Crutchfield, March 6, 1981 (2) Robert Dietch letter to H. R. Denton, May 7, 1981 Reference (1) submitted the analysis of plant transients and accidents impacted by the automation of the Auxiliary Feedwater System (AFWS) as required by the NRR Bulletins and Orders Task Force review of operating reactors following the accident at Three Mile Island, Unit 2 (TMI-2).
Using the minimum AFWS flow requirements determined in that analysis, new Technical Specifications for the automated AFWS were developed and submitted by Reference (2) as part of Amendment No. 97 to the San Onofre Unit 1 Operating License consisting of Proposed Change No. 102 to the Technical Specifications.
Since the analysis provided by Reference (1) was performed on an expedited schedule, some of the parameters used as input were conservative generic (standard plant) values. In particular, the value used for the Reactor Coolant Pump (RCP) heat input into the primary system was 5.0 Mwt/pump.
This is the value used by Westinghouse for calculations involving their standard plant design which includes larger pumps than those used at San Onofre Unit 1. The heat input from the RCPs at San Onofre Unit 1 was measured by Westinghouse to be 2.3 Mwt/pump.
PDR ADOCK 05000204
<P PDR'
Mr. D.
November 18, 1981 It was determined that in order to obtain a more plant specific value for the minimum flow requirements of the AFWS at San Onofre Unit 1, the limiting transients and accidents would be re-analyzed using a conservative value of 3.0 Mwt/pump. Accordingly, Enclosure 1 provides the results of the limiting cases as determined in Reference (1).
All other inputs and assumptions remain as discussed in Reference (1).
The two limiting cases were as follows:
Case 1 -
Loss of Main Feedwater, offsite power available, 165 gpm auxiliary feedwater actuated 3 minutes after reactor trip (Figures 1-5 of Enclosure 1).
Case 2 -
Main Feedline Break, offsite power available, 250 gpm auxiliary feedwater actuated 15 minutes after reactor trip (Figures 6-10 of Enclosure 1).
As indicated in the enclosed figures, the results of these two cases are acceptable, i.e., the pressurizer does not fill (Case 1) and the secondary heat sink remains effective in cooling the core and the core remains covered with water (Case 2).
These results demonstrate that for the design basis transients and accidents, the AFWS is of sufficient capacity to meet current day criteria and establishes the minimum flow requirements for the AFWS to be 165 gpm from either the motor driven or the steam driven auxiliary feedwater pump.
Since the minimum flow requirements for the AFWS pumps have been revised as a result of the re-analysis of plant transients and accidents, the Basis for the Proposed Technical Specification 4.1.9 "Auxiliary Feedwater Pumps and Valves", submitted by Reference (2) which discusses these flow requirements must also be revised. In addition, since the maximum steam generator pressure used in the analysis, as shown on Figures 5 and 10, is 1030 psia ( 1015 psig), this value in the Basis must also be revised.
The new version of the Basis for Technical Specification 4.1.9 is included as.
During the NRC site visit of July 8 and 9, 1981, the NRC staff provided for our review and comment the memorandum dated February 10, 1981 from the Auxiliary Systems Branch (ASB) regarding their review of the AFWS.
This document was discussed with the NRC staff resulting in three open items.
Responses to these open items are provided below. The items are identified by the numbering used in the memorandum of February 10, 1981.
B. Additional Short-Term Recommendations B.1. Recommendation - The licensee should provide redundant level indications and low level alarms in the control room for the AFW system primary water supply to allow the operator to anticipate the need to make up water or transfer to an alternate water supply and prevent a low pump suction pressure condition from occurring. The low level alarm setpoint should allow at least 20 minutes for operator action, assuming that the largest capacity AFW pump is operating.
Mr. D.
November 18, 1981 In a letter dated January 23, 1980, the licensee committed to installing an additional, redundant condensate storage tank level indicator and low level alarm. The low level alarm will allow at least 20 minutes for operator action, assuming that the largest capacity AFW pump is operating.
We have reviewed the licensee's response and conclude that the redundant indication and alarm circuitry must be redundant all the way from the detectors to the control room indicators including their power supplies.
The redundant indications and alarms should be powered by emergency busses with at least one circuit backed by a battery source. The licensee is requested to verify that the level indication and alarms are redundant as required.
We will report on the resolution of this matter in a supplement to this SER input.
Response - A review of the design and installation of the level indication and alarms from the condensate storage tank to the control room has verified that this instrumentation is redundant as required.
Independent redundant condensate storage tank level transmitter loops have been installed. One transmitter is aligned to train A, LT-6A, and the other to train B, LT-6B. LT-6A provides a signal to and is powered by LC-6A, which is powered by vital bus #1. LT-6B is likewise connected to LC-6B which is powered by vital bus #2. The train A indicator and alarm switch, LIS-6A is powered from vital bus
- 1. The train B indicator and alarm switch, LIS-6B is powered from vital bus #2. Separate alarm windows are provided for annunciation of low level for train A and train B. Thus, there is complete redundancy from transmitter to indicator for AFW water level.
The vital buses have backup battery power supplies.
B.4 Recommendation - Licensees with plants which require local manual realignment of valves to conduct periodic tests on the AFW system train, and there is only one remaining AFW train available for operation should propose Technical Specifications to provide that a dedicated individual who is in communication with the control room be stationed at the manual valves. Upon instruction from the control room, this operator would realign the valves in the AFW system train from the test mode to its operational alignment.
In response to this recommendation, the licensee stated in a letter dated January 23, 1980, that, "Auxiliary Feedwater pump testing will be performed such that local manual realignment will not be required."
Based on the information available including an October 16, 1980 letter detailing design modifications, we are unable to conclude that the licensee's statement provided in the January 23, 1980 letter is correct. We require that the licensee describe how the AFW system flow train is tested
Mr. D.
Novenber 18, 1981 without local manual realignment of valves. The description should include the present AFW system and the proposed modifications to the AFW system. We will report on the resolution of this matter in a supplement to this SER input.
Response - A description of the then proposed, now installed, AFWS was provided in our letter of October 16, 1980.
Included in that submittal was Sketch No. 10-14-80. As can be seen from the referenced sketch, AFWS Train A consists of the motor driven auxiliary feedwater pump (MDP),
discharge valve MOV-1202 and flow control valves FCV-2300 and 2301, AFWS Train B consists of the steam driven auxiliary feedwater pump, discharge valve CV-3203 and the flow control valves FCV-3300 and 3301. Either pump can supply flow through any of the 4 flow control valves. All required testing can be accomplished by remote manual control from the control room for the pumps, MOV-1202 and CV-3203. The preset position of the flow control valves will also be tested. No local manual realignment will be required, therefore the recommendation is no longer applicable.
C.
Long Term Recommendations C.4 Recommendation -
GL Licensees having plants with unprotected normal AFW system water supplies should evaluate the design of their AFW system to determine if automatic protection of the pumps is necessary following a seismic event or a tornado. The time available before pump damage, the alarms and indications available to the control room operator, and the time necessary for assessing the problem and taking action should be considered in determining whether operator action can be relied on to prevent pump damage. Consideration should be given to providing pump protection by means such as automatic switchover of the pump suction to the alternate safety-grade source of water, automatic pump trips on low suction pressure or upgrading the normal source of water to meet seismic Category I and tornado protection requirements.
In a letter dated October 16, 1980, the licensee proposed AFW system modifications which would be installed as part of the TMI Lessons Learned Requirements. In these modifications the licensee indicated that the AFW pumps would be provided with low suction pressure trips. The pumps would be tripped when in the automatic mode and a low suction pressure signal present for longer than 20 seconds.
We have reviewed the licensee's response and conclude that the response is incomplete. The licensee should provide low suction pressure trips for both modes of operation (manual and automatic) or demonstrate that when in the manual mode of operation the operator has sufficient time and information to take action to prevent pump damage following a seismic event or a tornado. We will report on the resolution of this matter in a supplement to this SER input.
Mr. D.
November 18, 1981 Response - The low suction pressure trip of the AFWS pumps described in our submittal of October 16, 1980 was not installed in order to comply with Recommendation GL-4 requiring pump protection from a seismic event or a tornado. This trip was installed as part of SCE's normal practice for new or backfitted pumping system installations. The means of protection described in GL-4 allow for means other than pump trip. If as a result of our evaluation of the AFWS it is concluded that recommendation GL-4 will. be met by the installation of low suction pressure trip of the AFWS pumps, the requirement for the trip to be functional in the manual mode or submittal of an appropriate analysis, will be addressed and resolved with the NRC staff at that time.
As stated in our letter dated January 23, 1980, and reiterated in our letter dated January 5, 1981, we deferred implementation of the "Long Term Recommendations" pending completion of the integrated assessment of potential modifications identified by review of applicable Systematic Evaluation Program topics.
If you have any questions or desire additional information regarding this subject, please contact me.
Very truly yours, Enclosure
ENCLOSURE 1 FIGURES 1-10 AFWS RE-ANALYSIS SAN ONOFRE UNIT 1
CORE HEAT FLUX FRACTION OF NOMINAL NUCLEAR POWER FRACTION OF NOMINAL Q***-.
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PRESSURIZER WATER VOLUME CUBIC FEET PRESSURIZER PRESSURE PSIA CD ru LA C
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LOOP 2 TEMPERATURE (COLD HOT SAT)
LOOP I TEMPERATURE(COLD HOT SAT)
DEGREES F DEGREES F CA 0nc)
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FIGURE 5 LOSS OF MAIN FEEDWATER 165 qpm @ 3 min.
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Figure 6:
Feedline Rupture 250 gpm @ 15 min.
PRESSURIZER WATER VOLUME CUBIC FEE I PRESSURIZER PRESSURE PSIA C3 IJ IJA C)
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LOOP 2 TEMPE RATURE(COLD HOT SAT)
LOOP I TEMPERATURE(COLD HOT SAT)
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Fi ure 9:
Feedline Rupture 250 gpm @ 15 min.