ML20072J420
| ML20072J420 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 06/27/1983 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Clark R, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 078, 78, NUDOCS 8306300096 | |
| Download: ML20072J420 (4) | |
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VINGINIA ELECTHIC AND POwEH COMPANY RIcIrwown,VINGINIA 2006I W.L.SrawAar Vaca Passios=r wuci.=42 o,= =* tion =
June 27, 1983 Mr. Harold R. Denton, Director Serial No. 078 Office of Nuclear Reactor Regulation N0/TAH:acm Attn:
Mr. Robert A. Clark, Chief Docket Nos. 50-338 Operating Reactors Branch No. 3 50-339 Division of Licensing License Nos. NPF-4 U. S. Nuclear Regulatory Commission NPF-7 Washington D. C. 20555 Gentlemen:
SAFETY CONCERN RESULTING FROM HUMAN FACTORS CONTROL ROOM MODIFICATION NORTH ANNA UNITS 1 AND 2 During March 1980, Essex Corporation performed a human engineering evaluation for the NRC of the North Anna Unit 2 Control Room.
The Essex Corporation objective for the review was ".... to identify features in the Control Room design that were contrary to human engineering principles and practices and would contribute to operator error".
We feel that the majority of the corrective actions resulting from the NRC/
Essex review resulted in enhancements that improved overall safety and reliability in the North Anna Control Room.
However, we have identified a potential source of operator error that resulted from the Hagan process controller modification. Under Item 12 of the Essex Corporation Report to the NRC dated March 27, 1980, it was stated that "There are some specific problem Hagan controllers.
The nonregulated (nonregenerative) heat exchange outlet temperature control reduces temperature by increasing the meter value.
The Master Pressurizer (Pressure) Controller increases to decrease pressure. Both of these are violations of stereotype and convention.
If a control is increased, the display being effected by the control should also increase.
In moments of strass, this inverse relationship could induce operator error.
(Category 1)".
To address this Category 1 Human Engineering Discrepancy (HED), Vepco with the assistance of a Human Factor (HF) consultant identified additional Hagan controllers that exhibited similar inverse control action /
process effect function and instituted a design modification to correct this item (see Table A).
Unkncun to the HF consultant or to the Vepco design modification personnel, Essex had investigated the additional Hagan controllers and did not addreas them as an HED Item because the action of the manual pushbutton did fit the stereotype of the operator's perceived function of the controller (i.e. in operating the Pressurizer Pressure Master Controller, the operator perceives a direct effect of pressure change. Therefore the UP pushbutton should cause an increase in Pressurizer pressure. However in operating the Atmospheric Steam
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LVenuswA Enacresc Awa Pows Commwr To - Harold R. Denton Dump Valve ' Controller, th'e operator's perception is of opening or closing a valve to affect Steam Generator pressure. Therefore the UP pushbutton should cause the ' Atmospheric Steam Dump Valve to open).
This was not stated but implied in the Essex Report.
The affected controllers (see Table B) exhibit a perceived function similar to that of the Atmospheric Steam Dump Valves such that the operators considered the controller as moving a valve in order to affect a process variable.
By modifying the action of these controllers to match the effect of the process variable, the operators have been required to modify their perception of the controller's function.
-In discussions with newly licensed and veteran licensed operators, we have determined that. the controller modification has caused au increase in the operator's mental workload in terms of the need to remember the particular unconventional Hagan controller operation.
Further, if the operator fails to recognize that an improper operation of the controller has caused an adverse impact on - the plant, it is probable that another error of equal or more serious consequences may be committed by the.. operator in an effort to recover from the original error.
The affected controllers perform safety important functions which may mitigate the' consequences of.an accident.
Due to the importance of the affected systems and potential consequences, Vepco intends to institute a design change to eliminate the " inverse' acting" feature of these controllers. Vepco intends to modify the subject Hagan controllers during the next refueling outage of
'each unit.
If there are any' questions regarding this matter, please contact us.
Very truly yours,,
/# A W. L. Stew t
.cc:
Mr. Richard C. DeYoung, Director Office:of Inspection and Enforcement Washington, D. C. 20555 i=
Mr. James P. O'Reilly Regional Administrator Region II j
Atlanta, Georgia'30303-i--
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A TABLE A P
HAGAN PROCESS CONTROLLERS-MODIFIED BY DESIGN PACKAGE 80-S15
- NORTH ANNA UNITS 1 AND 2
- 1. : Steam Header Pressure Controller 2.
Pdessurizer' Spray Valve Controller.
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Pressurizer Master Pressure Controller
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- 4. 1 Low Pressure Letdown'Line Presr:re Controller 5.
Atmosphere Steam Dump Valve Controller 6.
Non-Regenerative Heat Exchanger Outlet Temperature Controller i
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HACAN PROCESS 'ONTROLLERS TO DE RESTORED TO ORIGINAL DESIGN C
NORTH ANNA UNITS 1 AND 2 1.-
Steam Header. Pressure Controller I2.
Pressurizer Spray Valve Controller.
~ 3. -Los Pressure Letdown Line Pressure Controller 4..AtmosphereSteamDumpValveController
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