ML19256F613
| ML19256F613 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 12/13/1979 |
| From: | William Jones OMAHA PUBLIC POWER DISTRICT |
| To: | Harold Denton, Reid R Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0578, RTR-NUREG-578 NUDOCS 7912190565 | |
| Download: ML19256F613 (9) | |
Text
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m Omaha Public Power District TELEPHONE 536 4000 AREA CODE 402 1623 MARNEY 4
O M AH A. NEBRASKA 68102
- December 13, 1979 Director of Nuclear Reactor Regulaticn ATTN:
Mr. Robert W. Reid, Chief Operating Reactors Branch No. 1+
U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Reference:
Docket No. 50- 285 Gentlemen:
Please find attached the Omaha Public Power District's proposal for implementing section 2.1.7.a of IMREG-0578, The proposal des-cribes a means of providing control grade automation the auxiliary feedwater system at the Fort Calhoun Station. This nu a fication is scheduled for installation during the next refueling outage, which will begin in early January, 1980.
Sincerely,
., s W. C. Jones Division Manager Production Operations WCJ/KJM/BJH:jmm Attach.
cc:
Mr. K. V. Seyfrit, Director U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 LeBoeuf, Lamb, Leiby & MacRae 1333 New Hampshire Avenue, N. W.
E Washington, D. C.
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SECTION 2.1.7.a AUTOMATIC / MANUAL INITIATION OF AUXILIARY FEEDWATER The autcmatic/ manual auxiliary feedvater system being installed by 0=aha Public Power District, to meet the requirements of NUREG-0578 and the Co= mission's SER for the Auxiliary Feedvater System at Fort Calhoun Station letter of October 22, 1979, is provided with several redundant and diverse actuation methods to insure reliability and availability.
As designed, direct parameter monitoring is provided by two steam generator level channels. One channel is associated with each of the two steam generators. Each independent level channel and its associated initiation equipment vill auto-initiate the entire auxiliary feedvater system.
Also provided are bus undervoltage or Offsite Power Lov Signal interlocks, auxiliary feed sequential initiation on safety injection, and an auxiliary feedvater anticipatory initiation on last main feed pump trip. These interlocks and/or alternate initiations are required to auto-start the aul_11ary feedvater system under accident, transient, and onsite/offsite power situations.
The bus undervoltage interlock is provided to start the electric driven pump (FW-6) with either offsite or onsite power if no safety injection actuation signal is present.
If offsite power is available, FW-6 vill start on low level from either channel after the setpoint-time delay is satisfied. If offsite power is lost and the emergency diesel is required, the offsite power interlock (bus undervoltage relay) vill prevent the auxiliary feedvater pump (FW-6) from loading on the bus until the diesel-generator has restored power to the bus.
The steam driven auxiliary feed pump, FW-10, requires only in-strument power for initiation.
It vill therefore be started on low level without an offsite power interlock.
Auxiliary feedvater initiation on safety injection serves a dual purpose. It provides an anticipatory actuation of auxiliary feedvater and for the electric driven pump (FW-6) it sequentially loads the pump on diesel generater 1 vith the other safety equipment loads. If safety injection occurs with offsite power available, either lov steam generator level or the existing safety related sequencer circuitry will auto-initiate the auxiliary feedvater system. If offsite power is lost with a safety injection signal present, the electric driven pump (FW-6) vill be loaded on the diesel only by the sequencial loading circuit. The steam driven auxiliary feedvater pump (FW-10) will be started by either the safety panel sequencer circuitry (to be consistent with FW-6 cir-cuitry) or steam generator low level channels. The same lov voltage circuitry as previously described in paragraph 3 is used for FW-6; however, it is actuated by a lockout relay (the station safety grade offsite power lov system) rather than direct undervoltage actuation.
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. In addition, an anticipatory auxiliary feedvater actuation vill be provided, such that if the last main feedvater pump trips (three main feed pumps are provided at Fort Calhoun Station, two are required for full power, the third is on auto-standby), the system vill be started automatically, As designed, the last feed pump trip vill auto-start FW-10 under all offsite or onsite power configurations. FW-6 vill start if offsite power is available; however, FW-6 start vill be blocked if low bus voltage exists or if the diesel breaker is closed. Lov steam generator level vill initiate FW-6 as previously described. The last main feed pump trip auto-start vill be overridden during normal unit shutdown and startup.
It should be noted that auto-initiation of auxiliary feedvater consists of starting both pumps FW-6 and FW-10, and opening the steam generator supply valves HCV-110TA and HCV-110TB to steam generator A and supply valves HCV-1108A and HCV-1108B to steam generator B.
The auto-actuation of either auxiliary feedvater pump will open all steam generator supply valves. The steam generator supply valves are equipped with override circuitry (of the auto-opening signals) for long term level control. Although the analysis does not take credit for its actuation, the supply valves are provided with a containment isolation "open" signal as an additional anticipatory opening.
Manual initiation of the system is available at all times. Parallel initiation circuitry is used such that if the auta=atic system fails the manual initiation remains available.
As proposed, the auxiliary feedvater system will be automatically initiated. When normal level is restored, remote manual override of the supply valves vill be used. The valves vill then be throttled for long ters operation. This method of remote manual throttling vill be required at some time into the accident. Adequate time vill be available to prevent overfilling of the steam generator and potential overcooling.
If low level is sensed after throttling, the supply valves vill be auto =atically reopened (each throttling valve is opened by its associ-ated lov steam generator level).
The auxiliary feedvater system initiation circuits vill be provided with the capability of testing the lov level circuitry and the sequencer circuitry on line. The remainder of the control system vill be tested each refueling. The pumps will be tested quarterly, per the station's Technical Specifications.
In the October 30, 1979, letter of clarification, six items were addressed on the short term requirement.
Each of those are addressed specifically as follows:
1.
Provide automatic / manual initiation of AFWS.
See the above system description, piping diagram (Figure II),
and the attached logie diagram (Figure I).
2.
Testability of the initiating signal and circuits is required.
a.
Lov level signal testable on line, cne lov level channel)'2I to remain operable at all times. 1 6 2 4 2-9 F b. SIAS sequencer circuit testable on line, one sequencer to remain. operable at all times.
. c. Last feed pump trip tested after each refueling. d. Pump operability and valve cycling vill be done quarterly, per the Technical Specifications. 3. Initiating signals and circuits shall be povered from emer-gency bus, a. See the attached Table I, Table II, and Figure 8.1.1. All systems are povered from energency buses. 4. Hecessary pumps and valves shall be included in the automatic sequence of loads to the emergency buses. The loading of diesel generator 1 with FW-6 is being a. evaluated. When the review is completed, non-essential loads vill be shed as required. As of this time, no problem has been encountered in loading FW-6 on diesel generator 1. 5 Failure of the automatic circuits shall not result in the less of manual capability to initiate the AFWS from the control room. a. All manual initiatien circuits are operational irregard-less of the status of the automatic circuits. See the above system description. 6. For those designs where instrument air is needed for oper-ation, the electric power supply requirement should be capable of being manually connected to emergency power sources, a. On completion of the system, 'no electrically powered air supplies vill be required. As proposed, the primary initiating circuits will meet single failure criteria. The low level initiation circuit consists of two control grade systems which are completely independent (FWIS/FW-6 Train A, and FWLS/1045 Train B), see Figure I. Either circuit vill initiate the entire auxiliary feedvater system. The sensors vill detect all loss of feedvater transients with adequate time provided for initiation, see the attached logic diagram. In the case of a LOCA, the AFWS initiation is provided by the existing safety grade sequential loading circuit (low steam generator level may also start FW-10). This system meets all single failure criteria. The last main feed pump trip actuation is an independent anti-cipatory channel. As part of the Fort Calhcun Statica alternate shutdown system, the AFWS centrol is manually transferred to a local panel outside the con-trol recm for emergency shn+down in case of control roca fire. Since $2) )' ~g7_ the present transfer switcL aes not meet single failure criteria, a re-dundant transfer switch vil be added. j
.h. Setpoints The District is continuing its study of setpoints. At present, a level below the lov steam generator level reactor trip is planned, coupled with a time delay. This setpoint will insure that decay heat removal capacity will be available. A setpoint of low level with time delay will minimize spurious actuation en unit trip as a result of normal steam generator level shrink. As initially stated, this system meets the requirements of IRTREG-0578 and the NRR review letter of October 22, 1979 323 1624 192
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