ML19340D317
| ML19340D317 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/18/1980 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8012300265 | |
| Download: ML19340D317 (13) | |
Text
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L NSEs NORTHERN 5TATES POWER COMPANY M I N N E A PO L.l S. M I N N E S OTA 55401 December 18, 1980 5
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- n Director of Nuclear Reactor Regulation f2 U S Nuclear Regulatory Commission 1y Washington, DC 20555
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PRAIRIE ISLAND NUCLEAR GENERATING PLANT j
Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Additional Information Relating to Auxiliary Fecdwater System On October 24, 1980 our Project Manager in the Division of Licensing forwarded to us five questions related to the Prairie Island Auxiliary Feedwater System. These questions arose during NRC Staff review of our response to Items 2.1.7.a and 2.1.7.b of NUREG-0578 and our responses to the Bulletins and Orders Group review of the Auxiliary Feedwater System.
At tachment I contains the additional information requested by the Staff.
Please contact us if you have any questions or if more information is needed to complete NRC review of this issue. is a correction to our letter dated November 21, 1979. Our initial response to NRC Recommendation GS-4 indicated that procedures C-28 and E-17 would be revised. Further review indicated that changes to another procedure were more appropriate.
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1 L 0 Mayer, PE Manager of Nuclear Support Services LOM/DMM/jh cc: J G Keppler G Charnoff l
NRC Resident Inspector Attachments l
8012300Qf$
o Director of NRR December 18, 1980 ADDITIONAL INFORMATION PRAIRIE ISLAND UNITS 1 & 2 AUXILIARY FEEDWATER SYSTEM AUTOMATIC INITIATION AND FLOW AND STEAM GENERATOR LEVEL INDICATION 1.
FSAR Section 6.6.4 states that the active components (valves, pumps, pump drives and lube-oil pumps) of the AFWS car ' a tested at any time, a.
What are the test intervals for these components?
b.
Which of the AFWS automatic initiation signals are used during these tests for starting the motor driven AFW pump; turbine driven AFW pump?
Response
The following components are tested on a monthly basis:
Motor valves from each AFW pump to each steam generator Main steam isolation valves from each steam generator to the TDAFW pump:
Main steam isolation valve to the TDAFW pump Both TDAFW pumps (output pressure) plus auxiliary lube oil pumps Both MDAW pumps (discharge pressure) plus auxiliary lube oil pumps Cooling Water Supply Valve to lube oil cooler TDAFW overspeed trip alarm On a yearly basis, the following items are checked:
I Full' flow cap bility of each AFW pump Steam supply available from each steam generator to the TDAFW pump Shutoff capability of discharge valves from each AFW pump to each steam generator In each of the above tests, a normal start signal from the control room is used to start each pump.
Once a year, during the integrated safety injection (SI) test, the SI signal is used to start each AFW pump.
2.
Dwg. NF-40312-2F, " Interlock logic diagram aux-feedwater system - Unit 1",
l indicated that the AFWS can be put in local centrol from the Hot shutdown panel, thus bypassing the automatic initiation circuitry.
Is this operation done under administrative control and what indication of bypass of this auto initiation function is available in the control room?
Response
The local switch position is annunciated, with an alarm, in the control room.
The component is considered out of service when in local control.
There is no particular administrative procedure for placing the control switch in local.
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Are there any operating bypasses associated with the automatic inicia-tion logic / circuitry (including sensors used for auto signals) during start-up or operation of the reactor? If so, how are these bypasses removed (automatically, etc.)?
Response
The only operating bypass is that provided by the " shutdown auto" position of the operating mode selector switch. This position is used during hot standby, hot shutdown, cooldown, cold shutdown and heatup operations.
This position blocks the automatic start of the auxiliary feedwater pumps when both main feedwater pumps are of f.
The purpose of the position is to allow operation of only one auxiliary feedwater pump during operations when one is more than sufficient, but to allow the safety related automatic start signals (safety injection and low steam generator level) to remain operational if needed to start both pumps.
" Shutdown Auto" does not bypass the safety related start signals.
The switches are positioned in either " auto" or " shutdown auto" in accordance with unit shutdown and unit startup procedures C1.3 and C1.2 at the times when the main feedwater is removed from or returned to se rvice.
4.
Process analog channels and logic channels of the automatic initiation circuits are tested periodically. What indication is available to the operator in the control room which displays at the system level the inoperable status of an AFW train during these tests?
Response
The analog channels and the subsequent logic channels which provide the safety reint 4 automatic start functions are subsets of the Engineered Safeguards and Reactor Protection systems.
In the case of the analog channels, redundant channels are distributed among the four protection channels referred to as protection sets.
For example, see the distribution of the steam generator level channels into Channel I, Channel II, Channel III and Channel IV in the response l
to question 5.
Each protection channel has an associated annunciator on the main cone.rol board. This. annunciator alarms whenever any of the test features for any of the analog channels in that protection channel are placed in the test mode including opening of any test panel cover or test jack switch or placing any bistable test switch in test.
In the case of the reactor protection logic, which contains the low steam generator level logic, there are two redundant trains.
In order to test the logic an associated reactor trip bypass breaker must be placed in service. This actuates a control room annunciator indicating that thac train is in test.
I In the case of the engineered safeguards logic, which contains the safety injection logic, there are two redundant trains. A train is placed in test by depressing a test button which interrupts the logic output stage. This actuates a control room annunciator stating that the train is in test.
A manual safety injection actuation will remove the train from test and actuate the logic outputs.
1-2
5.
Describe the steam generator level instrumentation at the Prairie Island facility.
This description should include:
a.
Type and number of level channels per steam generator ' including the range of each channel, b.
The specific source (vital bus) from which each of these channels is powered.
c.
Capability for testing and calibration including the interval between tests.
d.
The type of indication available in the control room for each channel (indicator, recorder, etc.).
Response
a.
Type and number of level channels per steam generator including the range of each channel, l
Four channels of indication are provided for each steam generator.
There are three narrow range channels and one wide range channel. The narrow range channels are used for indicating protection functions and in the automatic control system. They indicate in the normal operational range for the steam generator. The wide range channel is used only for indication. Table 1 and Figure 1 summarize the indications provided and the level reference points for steam generator 1avel instrumentation.
All channels measure level as a function of the difference in pressure between the weight of water in the steam generator and a reference leg using a condensate pot.
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TABLE 1 STEAM GENERATOR #11 & #12 (#21 and #22 SIMILAR) INDICATION Flow Diagram NF-39218 & 19 Nominal Capacity 43899 Gal (Full)
X-Hiaw Print 1-1 (Tech Manual Also)
Calculated Capacity 43899 Gal (Full)
Level Instrumentation Readout:
Location Instrument Range SG #11:
Remote (Control Rm)
LI-461,-46 2,-463 0-100%
(Narrow Ranges)
LI-460 (Wide Range) 0-100%
LR-460,-461 0-100%
(Recorders)
Local (Shutdown Pnl)
LI-18016 (Wide Range) 0-100%
Computer LT-24080, LT-24081, 0-100%
LT-24082 (Narrow)
LT-24083 (Wide) 0-100%
_SG #12:
Remote (Control Rm)
LI-471,-472,-473 0-100%
(Narrow Range)
LI-470 (Wide Range) 0-100%
LR-461,470 0-100%
(Recorders)
Local (Shutdown Pnl)
LI-18012 (Wide Range) 0-100%
Computer LT-24084, LT-24085, 0-100%
LT-24086 (Narrow)
LT-24087 (Wide) 0-100%
NOTE: Narrow Range Calibrated for Water at Operating Temp Wide Range Calibrated for Water at STP.
1-4
b.
The specific source (vital bus) from which each of these channels is powered.
Each steam generator level channel is powered from one of four instrument inverters. Each inverter is powered from one of the Class IE DC power systems. Power to the DC busses is normally supplied through the battery charger. The battery charger is fed from the 480VAC vital bus with diesel backup. Upon a loss of vital AC supply to the battery charger the inverter is powered from the associated battery (See Figures 2 and 3).
The power supplies are divided into trains A and B associated with diesel generaters #1 and #2 respectively.
Instrument busses are numbered I, II, III, and IV.
Protection channels are labeled red, white, blue and yellow. Table 2 lists the source supplies for each steam generator level channel.
N TABLE 2 POWER FEEDS TO STEAM GENERATOR LEVEL CHANNELS Tag Protection Instrument Power No Function Channel Bus Train i
460 Wide Range Level None I
B l
461 Narrow Range Level Red I
B 462 Narrow Range Level Blue III A
463 Narrow Range Level Yellow IV B
470 Wide Range Level None III A
471 Narrow Range Level Yellow IV B
472 Narrow Range Level Red I
B 473 Narrow Range Level Wh it e II A
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c.
Capability for testing and calibration including the interval between tests.
Our leter of December 29, 1979 titled, " Auxiliary Feedwater System Information, Lessons Learned Recommendations 2.1.7a and b" included the following statement on testing capability which is applicable to the narrow range steam generator level channels:
The design provides for controlled access to all trip settings, module calibration adjustments, test point s, and signal injection points.
FSAR Section 7.2.2, " System Design", details the testing provisions:
Provisions are made, for process variables, to manually place the output of the bistable in a tripped condition for "at power" testing.
The basic arrangement of elements comprising a representative analog pro-tection channel is shown in Figure 7.2-5 attached. These elements include a sensor or transmitter, power supply, bistable, bistable trip switch and proving lamp, test-operate switch, test annunciator, test signal injection jack, and test points. A portion of the logic system is also included to illustrate the overlap between the typical analog channel and the corresponding logic circuits.
The analog system symbols are given in Figure 7.2-9 attached. Each process protection rack includes a test panel containing those switches, tes t jacks, and related equipment needed to test the channels contained in the rack.
Testing of process analog protection channels requires that the bistable output relays of the channel under test be placed in the tripped mode prior to proceeding with the analog channel tests.
Thus, for the channel under test, the relay elements in the two-out-of-four coincident matrices will be in the tripped mode during the entire tese f d2at channel. It is observed that the remaining channels of th o-out-of-three or the two-out-of-four protective functions meet the.
gle failure criterion when a channel.is bypassed or tripped. Placing the bistable trip switch in the tripped mode de-energizes (trips) the bistable output relays and connects a proving lamp to the bistable output circuit.
This permits the electrical operation of the bistable to be observed and the bistable set point relative to the channel analog signal to be verified. Upon completion of test of the analog channel, the bistable trip switches are manually reset to their operate mode.
Process Analog channel test and calibration is accomplished by simulating a process measurement signal, varying the simulated signal over its signal span and checking the correlation of bistable set points, channel readouts, and other loop elements with precision portable read-out equipment.
See Figure 7.2-5.
Test jacks are provided in the test panel for injection of the simulated process signal into each process analog protection channel. Test points are provided in the channel to facilitate an independent means for precision measurement and correlation of the test signal.
Cogic Channel testing is similarly described in FSAR Section 7.2.2.
1-6
Transmitter calibration is accomplished by isolating the transmitter from the steam generator by means of an instrument manifold, applying a differential pressure to the transmittar, and measuring the transmitter output.
Calibration of the narrow range channels is performed annually in accordance with SCP 1002A (2002A for Unit 2) for the instrument channel and SCP1002B (2002B) for the transmitter. The channel is tested monthly by SCP 1003 (2003). The wide range channel is calibrated annually by SCP 1002B (2002B) for the transmitter and SCP 1548 (2548) for the instrument channel.
d.
The type of indication available in the control room for each channel (indicator, recorder, ets.).
See Table 1.
FIGURE 1 Steam Generator Level Ranges
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FIGURE 7.2-5 PROCESS SENSOR PT ANNUN.
CH. TEST SIGNAL :
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l BASIC ELEMENTS OF A PROCESS CONTROL ANALOG CHANhEL 1-10 i
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FIGURE 7.2-9 ANALOG SYSTEM SYMBOLS Alarm Al Buffer Buf Special Function (such as a pressure compensation unit or lead / log f
conpensation)
FC
- Flow controller (off-on unless output signal is shown)
Flow Indicator FI Flow Transmitter FT High Level Reactor Trip
!!L LRT High Pressure Reactor Trip
!!i PRT Isolation Current Repeater I/I Isolation (other than I/I)
ISOL L'evel controller (off-on unless output signal is shown)
LC Level Indicator LI Lead / Lag L/L Low Level
- Low: LOL Low Level Reactor Trip Lo LRT Low Pressure Reactor Trip Le PRI L,g Programmed Reference Level Level Transmitter LI Nuclear Flux Controller NC Nuclear Flux Detector
'!E Nuclear Flux Indicator NI Nuclear Flux Signal Modifier NM Nuclear Power Supply NQ Pressure Controller (off-on unless output signal is shown)
PC Pressure Indicator PI Pressure Signal Modifier PM Programmed Reference Pressure P
ref Power Supply PS Pressure Indicator PI Pressure Transmitter PT Nuclear Flux Signal Modifier QM ANALOG SYSTEM SIGNALS 1-11
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Att.chment 2 Director of NRR December 18, 1980 CORRECTION TO NSF RESPONSE IV NRC RECOMMENDATION GS-4 CONTAINED IN A LETTER DATED NOVEMBER 21, 1979 FROM L 0 MAYER TO DIRECTOR, NRR, USNRC 2.3 Recommendation GS-4 Emergency procedures for transferring to alternate sources of AFW supply should be available to the plant operators.
These procedures should include criteria to inform the operators when, and in what order, the transfer to alternate water sources should take place. The following cases should be covered by the procedures:
The case in which the primary water supply is not initially available.
The procedures for this case should include any operator actions required to protect the AFW system pumps against self-damage before.
water flow is initiated; and, The case in which the primary water supply is being depleted. The procedure for this case should provide for transfer to the alternate water sources prior to draining of the primary water supply.
Response
Emergency procedure (ES) " Loss of Feedwater Flow" was rewritten to include the concerns as recommended in GS-4 above. A review of other procedures such as C28 "Feedwater Condensate" and E17 " Emergency Cooldown" did not result in procedure changes.
8 2-1 L