ML20237B999
| ML20237B999 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/14/1987 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| GL-83-28, NUDOCS 8712180034 | |
| Download: ML20237B999 (9) | |
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- 'e TENNESSEE VALLEY AUTHORITY
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CH ATTANOOGA, TENNESSEE 37401 SN 157B Lookout Place j
DE!C 141987 4
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U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington,'D.C.
20555 Centlemen:
In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - GENERIC LETTER (GL) 83-28, ITEM 1.2, POSTTRIP REVIEW The purpose of this letter is to inform NRC of SQN's current efforts for satisfying the requirements of item 1.2 of CL 83-28.
By a November 7, 1983 letter from L. M. Mills to E. Adensam of NRC, TVA provided its initial response to CL 83-28.
Following TVA's initial response, Science Applications International Corporation, under contract with NRC, reviewed TVA's initial-response to CL 83-28, item 1.2, and issued a Technical Evaluation Report (TER) on SQN units 1 and 2.
The TER identified several areas where TVA either failed to meet certain criteria or provided insufficient information.
In response to these deficiencies, TVA, in a May 2, 1986 letter, made a cammitment to change SQN's process computer storage capacity for time history recorders and also provided additional information with regard to how SQN plant parameters are recorded for posttrip review.
The May 1986 letter (reference enclosure 1, item 3) also stated that SQN's data retention procedures meet the criteria for ensuring that information recorded for posttrip review is maintained in an acceptable manner for the life of the plant.
A July 9, 1986 telephone conference call between NRC and SQN's staff was held to discuss TVA's May 2, 1986 response. NRC's staff indicated that itet.s 1.C.
1.D, 2, 3, and the commitment to change the process computer storage capacity were all acceptable. NRC staff was not satisfied with SQN's position that posttrip review requirements are limited only to Condition 11 events.
In addition, NRC stated that in lieu of the Sequence of Events (SOE) recorder, other plant recorders (i.e., alarm printers with " time tagging," Safety Parameter Display System [SpDS) computer, Technical Support Center [TSC], and chart recorders with uninterrupted power) wera more than sufficient for gathering posttrip data. Mutual agreement was reached that SQN would submit another response to item 1.2.
TVA staff asked the NRC staff if this response would be a restart item. NRC's staff agreed that TVA's response would not be needed before restart.
Based on the above information,~ enclosure 1 addresses the following open items:
1.
Unrecorded plant parameters; 2.
Time history recorders that did not meet the minimum performance
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characteristics; 8712180034 871214
'b PDR ADOCK 05000327 P-DCD An Equal Opportunity Employer
f [lEiG 141987 U.S. Nuclear Regulatory Commission 3.
Time history sampling intervals for SQN's TSC Computer; 4.
NRC concern with SQN's previous position that CL 83-28 posttrip review requirements are limited only to Condition II events.
Closure of these items by NRC will confirm SQN's satisfactory completion of the requirements of GL 83-28, item 1.2.
If you have any questions concerning this issue, please telephone D. V. Goodin, of the SQN Site Licensing Staff, at (615) 870-7734.
Very truly yours, i
TENNESSE V LLEY AUTHORITY l
R.
- ridley, irector Nuclear Licensing and Regulatory Affairs Enclosures cc (Enclosures):
Mr. G. G.
Zech, Assistant Director for Inspection Programs Office of Special Projects U.S. Nuclear Regulatory Commission 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. J. A. Zwolinski, Assistant Director for Projects 1
Division of TVA Projects Office of Special Projects U.S. Nuclear Regulatory Commission 4350 East-West Highway IGN 322 Bethesda, Maryland 20814 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379
4 ENCLOSURE 1 Item 1 i
Unrecorded plant parameters Many of the parameters that were identified'in the Technical Evaluation Report (TER) as not recorded have been added to Sequoyah Nuclear Plant's (SQN's)
Technical Support Center (TSC) computer for historical data storage..(Refer to attachment 1 for a list of these parameters.) The TSC computer accepts digital and analog input from up to 1600 data points.
Data is continuously monitored and displayed on color cathode ray tube (CRT) terminals in'the TSC and the control room.
The TSC computer provides control room personnel with plant overview displays showing the current status and recent history (up to 30 minutes) of various major systems, as well as providing a ready means of identification of any deviation from normal.
Refer to attachment 2 for the historical data durations and sample intervals of all TSC computer parameters.
Power for the TSC computer equipment is supplied from the TSC l
distribution board. Normal 480-volt power is supplied through an inverter to the TSC distribution board.
Backup power is supplied from 250-volt batteries through the inverter.
A.
CONTAINMENT ISOLATION Containment isolation is not a reactor trip causal function.
The containment isolation function exists in two phases:
phase A or phase B.
The phase A signal, which closes the majority of the containment isolation valves, is caused by a safety injection (SI) signal, which precipitates a reactor trip.
The phase B signal that closes the remaining containment isolation valves is caused by a high-high containment pressure signal.
Both of these containment isolation signals have been added to SQN's TSC computer for historical data storage.
B.
CONTROL ROD POSITION As stated in the May 2, 1986 submittal, the reacto'r trip causal functions associated with control rod malfunctions (i.e., overpower excursions, startup excursions, and rate trips) are monitored by the nuclear-instrumentation system and recorded by the sequence of events (SOE) program on the plant process computer.
Rod bottom lights are verified as an immediate operator action following a reactor trip-to ensura s.et all control rods are fully inserted.
Since the trip functions associi.ted with control rod malfunctions are monitcred and recorded and the proper tripped condition is verified, recording individual control rod positions as a function of time would not provide significant benefits over SQN's existing system.
During an anticipated trip without a scram event, the immediate action steps require the operator to physically open the reactor trip breakers in the auxiliary building.
The SOE program records the time the trip breakers are opened, and the operator verifies tne " rods at bottom" lights.
Because of the high level of confidence that rods reach their "at-bottom" condition following the opening of the reactor trip breakers, recording individual control rod positions as a function of time would not provide significant additional information for analyzing the root cause of the trip or proper equipment operation.
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_ C.
SI; FLOW, PUMP / VALVE STATUS SI flows (A and B train) have been added to SQN's TSC computer for-historical data storage.
The following three flows have been added:
1.
high head injection flow 2.
intermediate head injection flow go.
3.
low head injection flow Since flow is indicative of pump status (on/off), no historical data exists within the TSC computer for recording pump. status.
Since historical pump flow data is available, addition of pump status would not-provide significant benefits for determining the root cause of the reactor trip or for analyzing proper. equipment operation.
Valve status data is available on SQN's TSC for.the high head SI flow path-and the low head SI flow path.
Valve status information for the intermediate head SI flow path is not provided on SQN's TSC historical data base. Valves within this flow path are not required to~ change-positions upon an SI or reactor trip signal.
SQN's emergency procedures only require these valves to be operated 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> after switchover to the containment sump following a loss of coolant accident (LOCA).
The addition of these valves to the historical data base would not aid in identifying improper valve operation following a reactor trip, nor would it support an analysis for determining the root cause'of a reactor trip.
D.
MAIN STEAM ISOLATION VALVE (MSIV) POSITION Individual MSIV positions (open/ closed) have been added ixi SQN's TSC computer for historical data storage.
E.
AUXILIARY FEEDWATER (AFW) SYSTEM; FLOW, PUMP / VALVE" STATUS AFW flows have been added to SQN's TSC computer for historical data storage.
Total AFW flow (motor-driven flow plus turbine-driven flow) is recorded for each of SQN's four steam generators (SG).
Because total pump flows are indicative of pump status, no historical data' exists within the TSC computer for recording pump status. Addition of individual pump status would not provide significant benefits for determining the root cause of a reactor trip or for analyzing proper equipment operation.
AFW valve status information (closed / modulating) is available on the TSC computer for each of the eight SG level control valves.
These valves 1
modulate to maintain SG level when the AFW system is in service.
F.
AC/DC SYSTEM STATUS (BUS VOLTAGE)
The ac buses associated with safety equipment at SQN are the 6900-volt' buses within the 6900-volt shutdown boards.
The dc buses associated with safety equipment are the 125-volt vital-power-buses'within SQN's 125-volt battery boards.
Both sets of buses are monitored and are provided with-
" time tagged" alarms. Any abnormal condition (overvoltage, undervoltage, or failure) on these sets of buses is recorded on SQN's electrical board' Terminet 300 printer located.in the main control room.
The' printer records the time of the event and identifies the bus that is experiencing the abnormal condition.
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Once the vol_tage of the bus underg fag the abnormal condition is restored--
to normal' status, the printer w' 1 ;;ain record the-time and ideniify the bus that was restored.
The adt.d n of ac/dc voltages on a time history recorder would not provide signH 8 a t benefits over SQN's existing time tagged alarm printer system.
The power supply for the logic system that inputs to the printer,xis the 48-volt dc plant battery board. The control room printer receives power j
from the 120-volt ac preferred power system with battery backup power.
Both power supplies provide norinterrupted power.
G.
DIESEL GENERATOR (DG) STATUS (START /STOP: ON/0FF)
DG status is provided on SQN's electrical. board Terminet 300 printer, similar to the ac/dc system status.
The printer records the time when a DG starts or stops as well as 13 abnormal DG conditions (cooling water-abnormal, lube oil abnormal, overload, overspeed trip, etc.).
The addition of DG status to a time history recorder would not provide significant benefits over SQN's existing time tagged alarm printer system.
H.
PRESSURE-OPERATED RELIEF VALVE (PORV) POSITION SQN does not have PORV position indication on its SOE recorder or the. time-history recorder: however, five other parameters, which are indicative of PORV position, are stored on.the TSC computer.
The following five signals are received by the TSC computer for historical data storage.
i 1.
Acoustic Monitoring:
single point digital 2.
Tailpipe Temperatures:
Two analog signals--one for each line downstream of.each POR,V.
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3.
Pressurizer Relief Tank (PRT) Temperatures: One analog signal provides indication of i
PRT temperature.
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4.
PRT Level: One analog signal provides indication of PRT level.
5.
PRT Pressure: One analog signal provides indication of PRT pressure.
Each of these five parameters is an indirect function of PORV position.
The addition of direct PORV position indication to the SOE recorder or a time history recorder would not provide significant benefits over SQN's existing set of parameters.
I.
CONTAINMENT SUMP LEVEL Containment sump level has been added to SQN's TSC computer for historical data storage.
Four level transmitters provide analog signals to the TSC computer.
. J.
PRIMARY SYSTEM FLOW Reactor coolant system flow has been added to SQN's TSC computer for historical data storage.
Four flow transmitters provide analog signals to the'TSC computer.
Item 2
_.o Time history recorders that did not meet the minimum performance characteristics.
Response
Sequoyah's plant computer storage capacity for pretrip and posttrip history recorders has been extended to 5 and 10 minutes, respectively.
This commitment, as contained in enclosure 2 of the May 2, 1986 letter, was completed on July 31, 1986.
Item 3 Time history sampling interval for SQN's TSC computer.
Response
Section 2.0 of the August 1985 TER contained review criteria developed for the requirements of item 1.2 of GL 83-28. One recommended-guideline was a-10-second sample interval for analog time history data. SQN's sample interval and time history capabilities for the TSC computer are outlined on attachment 2.
A 10-second sample interval extends 5 minutes pretrip'and 5 minutes posttrip. A 1-minute sample interval extends 30 minutes pretrip and 30.
minutes posttrip. Additionally, a 24-hour time history exists posttrip with a S-minute sample interval.
Based on these current capabilities, SQN finds ~that an additional 5 minutes of posttrip data with a 10-second sample-interval would not significantly support the posttrip analysis for determining the cause of the trip.
Item 4 NRC concern with SQN's previous position that GL 83-28 posttrip review requirements are limited only to Condition II events.
Response
In TVA's May 2,1986 letter, it was stated that SQN's SOE recorder and time history recorders were programmed to respond on a reactor trip, which is a.
Condition II event in the Final Safety Analysis Report (FSAR).
Additionally, it was stated that there was no intent on the part of TVA to utilize these two i
systems alone to analyze all Chapter 15 accidents.
The basis for these statements stemmed from the fact that many of the plant parameters, identified for posttrip review, were not reactor trip (Condition II) causal functions and would, therefore, not play an integral part in analyzing the root cause of the-trip or proper equipment operation.
These parameters were circled and identified as not recorded on sheet 12 of the TER.
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, Since SQN has added the majority of these missing parameters to its TSC computer, a posttrip analysis now encompasses Conditions I, II, III, and IV events as described in Chapter 15 of SQN's FSAR.
The means of verifying that these parameters have reached their accident condition, when required, is now recorded pre-and posttrip.
Conclusion o
SQN's recent efforts to comply with the guidelines of GL 83-28, item 1.2, for j
posttrip review have now been completed.
The capability of recording, l
recalling, and displaying information to permit a posttrip analysis for diagnosing the cause of unscheduled reactor shutdowns before restart and for ascertaining the proper functioning of safety-related equipment now exists for SQN units 1 and.2.
This additional data /information is displayed in a form that permits ease of assimilation and analysis by persons trained in-the use of systematic safety assessment procedures, i
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ATTACHMENT 1 SQN PARAMETERS FOR POSTTRIP REVIEW Circled parameters indicate those identified in TER as not Recorded Circled parameters with an "A" indicate NRC acceptance by the May 1986 response and July 1986 telephone conference call.
TIME PARAMETER SOE RECORDER HISTORY RECORDER 1.
2.
SI Signal X(1) 3.
Containment Isolation 4.
Turbine Trip X(1) 5.
Control Rod Position h
6.
Neutron Flux, Power X(1)
X 7.
Containment Pressure X
X 8.
Containment Radiation
@A 9.
Containment Sump Level h
10.
Primary System Pressure X(1)
X 11.
Primary System Temperature X(1)
X 12.
Pressurizer Level
@(1)A 13.
Reactor Coolant Pump Status X(1) 14.
Primary System Flow X(1) 15.
SI Flow, Pump / Valve Status 16.
MSIV Position
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17.
SG Pressure X
X 18.
SG Level X(1)
X
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19.
Feedwater Flow X
X 20.
Steam Flow X
X 21.
AFW Flow Pump / Valve Status 22.
AC/DC System Status (Bus Voltage)
{
23.
DG Status (Start /Stop; on/off) 24.
PORV Position (1) Trip Parameters (2) Parameter may be monitored by either an SOE or time history recorder.
(3) Acceptable recorder options are:
(a) system flow recorded on an E9E recorder, (b) system flow recorded on a time history recorder, or (c) equipment status recorded on an SOE recorder.
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e ATTACHMENT 2 HISTORICAL DATA DURATIONS AND SAMPLE INTERVALS FOR SQN's TSC COMPUTER Reactor Trip V//////////A 5 minutes 5 minutes 10-second sample 10-second sample interval interval V////////////////////////////////A 30 minutes 30 minutes 1-minute 1-minute sample sample interval interval
//////////////////////////////////////A 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 5-minute sample intervals time = 0 i
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