ML20042G252

Responds to Generic Ltr 89-19, Request for Action Re Resolution of USI A-47, 'Safety Implication of Control Sys in LWR Nuclear Power Plants.'

ML20042G252
Person / Time
Site:	River Bend
Issue date:	05/04/1990
From:	Odell W GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-GTECI-A-47, REF-GTECI-SY, TASK-A-47, TASK-OR GL-89-19, RBG-32793, NUDOCS 9005110277
Download: ML20042G252 (4)

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May 4,'1990 RBG- 32793 File Nos. G9.5, G9.33.4 U. S. Nuclear Regulatory Commission Document Control Desk Washington,.D. C. 20355 Gentlemen:

River Bend Station - Unit 1 Docket No.-50-458

.This letter provides Gulf States Utilities Company's (GSU) response to Generic letter 89-19, Request for Action Related to Resolution of Unresolved-Safety Issue A-47 " Safety Implication of. 1 Control Systems in LWR Nuclear Power Plants." Pursuant to 10 CFR 50.54(f), all GE BWR plants were requested to provide automatic

~ reactor vessel overfill protection. It was stated that this (

aesinn should:.be- sufficiently separate from the main feedwater (MFW) control-systemtoensurethattneMFW pump will trip on- ,

reactor high-water-level. signal when required. -In addition it was recoranended that- all plants reassess their operating procedures and operator training.ared modify them if necessary to ,

ensure that= operators can mitigate reactor vessel overfill events during reduced' pressure operation.

The- NRC in the generic letter recommended that plant procedures and technical specifications include provisions to verify periodically the . operability of overfill protection and ensure that auto:natic overfill protection to mitigate main feedwater-overfeed events is. operable during power operation. (

GSU is a member of the Boiling Water Reactor Owners' Group ,

(BWROG) committee which responded to Generic Letter 89-19. GSU l endorses this BWROG response (BWROG-9048 from S. D. Floyd to J.

G. Partlow dated April 2, 1990) and agrees with the conclusions- 't made :therein. GSU has reviewed that report and concludes that i River' Bend Station (RBS) provides adequate automatic RPV overfill :l protection. Furthermore, GSU has concluded that the RBS overfill j protection system is consistent.with the NRC -requirements for 1 closure of USI A-47. As stated in the BWR0G report, the NRC has a recognized that the safety benefits gained by installing

-additional RPV_ protection system redundancy and independence from 0

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.g NRC --Page 2 May 4, 1990 existing MFW control system equipment is not significant, and that modifications costing in excess of $100,000 would -not be cost beneficial. Our preliminary estimates indicate that RBS would well exceed this figure.. A review conducted to respond to '

this generic letter did not identify any MFW system overfill ,

event subsequent to installation of automatic overfill protection  !

in BWR plants. In addition, the review did not identify the occurrence of any common-mode.MFW control system failure that would have.~resulted in RPV overfill. As discussed in the BWROG-Report, to fully implement the requirements of Generic Letter 89-19 would require substantial plant modifications with little safety benefit, therefore GSU does not consider the modifications to be cost beneficial.

In addition, GSU performed a plant specific review of the vessel overfill protection sys tem : at River Bend Station. The RBS feedwater control system uses a 3 element process for 1 intermediate and high reactor power.rangas. The 3 elements are used in combination to control the feedwater control valves. The 3 elements used are steam flow, feedwater flow and reactor water  :

level. Steam flow is measured by 4 differential pressure transmitters which. provide signals to the feedwater control system. Feedwater flow is measured by 2 differential pressure 3

-transmitters which provide signals _to- the feedwater control system. Reactor water level is measured by 3 narrow range and I wide range differential pressure transmitters. Each measurement is independent from each other in terms of tubing, pressure vessel. taps' and condensing pots and the 3 narrow range transmitters are located in 3 separate panels and provide signals _

I to 3 alarm trip units to provide annunication and output to a 2 out of 3 trip logic for main turbine trip and.feedwater_ pump trips. Two of these three transmitters are also used for MFW control. The wide range transmitter provides a signal for control room recording and is not included in the control or trip

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The River. Bend Station feedwater control and trip systems do provide adequate automatic, overfill protection. To achieve' pure separation for the- sensing circuitry would require the installation of two additional vessel taps and two additional level transmitters dedicated to feedwater level control. In addition, extensive control room modifications would be required to separate the feedwater control and overfill sensing electrical systems into totally independent cabinet locations. These physical modifications to further separate the control and trip functions are not considered cost beneficial as previously discussed.

• GSU operations pesonnel reviewed procedures used to control )

reactor water level. No modifications to these procedures were determired to be necesso n e a result of this review. l si .__ _._

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. NRC_ Page 3 May 4, 1990 The RBS training requirements for operator-qualification include several. scenarios'_for' conditions which may challenge the reactor

~ pressure vessel limits. Training is performed for each of the following events:

-Manual control of feedwater l'h 2 Malfunctions of reactor pressure / volume control system

3) Excess feedwater to power In addition, operators receive extensive classroom and simulator training in implementation of Emergency Operating Procedure E0P-0001, Reactor Pressure Vessel Control, which would be entered during a reactor-pressure vessel overfill event. A lesson plan on Emergency _ Operating Procedures discusses the basis for maintaining water level within control bands. GSU personnel, through performance of a review of the training program, concluded that adequate operator training is in place to mitigate overfill events at River Bend Station.

The RBS Technical Specification 3/4.3.9 requires that the feedwater system / main turbine trip system-reactor vessel water level-high (level 8) trip be operable and requires surveillances of a channel check, channel functional test and channel calibration for a minimum of 3 channels on the following frequencies:

Channel Check Daily Channel Functional Test Monthly Channel Calibration 18 Months

-I In conclusion, GSU has determined that the present RBS design, operational procedures, established training and surveillance requirements are adequate to preclude a reacter pressure _ vessel overfill event.

If you L. haveatany(questions Dietrich 504) 381-4866. on this response, please contact Mr. L.

Sincerel ,

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V. W . Odell I Manager-0versight River Bend Nuclear Group TFP/WH0/LAE/LLD/WJS/pg

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i-UNITED STATES OF AMERICA b

NUCLEAR REGUL3 TORY COMMISSION. -

o STATE OF-LOUISIANA )

F  : PARISH OF-WEST FELICIANA )

i uccket-No. 50-458  ;

In the Matter of- ) ,

' GULF' STATES UTILITIES-COMPANY )

(River Bond Station - Unit 1) r AFFIDAVIT .

W. H. Odell, being duly sworn, states that:he is.a Manager-

- Oversight for Gulf' States Utilities Company; that he is-authorized on the part of said company to sign and file with the. Nuclear -Regulatory- Commission the documents-- attached i hereto; and that' all'such documents are true and correct ~to I the best of'his knowledge, information and belief. ,

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W. H.'Odell  !

r Subscribed and sworn to before me, a Notary Public in and si for the State and Parish above named, this N b '# . day of s

d , 19 9 0 . . My- Coramission expires with Life. _;

i e i 010ALdlCL d luws36 Claudia F. Hurst Notary Public in and for West Feliciana Parish, Louisiana f

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