ML19338B860
| ML19338B860 | |
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|---|---|
| Site: | Crane  |
| Issue date: | 06/30/1979 |
| From: | Pack R ELECTRIC POWER RESEARCH INSTITUTE |
| To: | |
| References | |
| TASK-TF, TASK-TMR ERPI-NP-1118-SY, NUDOCS 8001200079 | |
| Download: ML19338B860 (55) | |
Text
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Human Factors M3thods for Nuclaar gl
. Control Room Design EPRI NP-1118-SY Koywords:
Project 501-3 Human Factors Engineering Summary Report Control Room Design June 1979 Nuclear Power Plants n:7w -
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.l Pr:p:rsd by t Lockbred Missiles & Space Co., Inc.
i Sunnyvale, California 8001200OH i
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Human Factors Methods for Nuclear Control Room Design NP-1118-SY Research Project 501-3 1.*.
Summary Report, June 1979 t.
Prepared by LOCKHEED MISSILES & SPACE CO., INC.
i P.O. Box 504 Sunnyvale, California 94086 Principal Investigators l
Joseph L. Seminara L
Sharen K. Eckert Sidney Seidenstein Wayne R. Gonzalez Richard L. Stempson Stuart O. Parsons i
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i Prepared for i
Electric Power Research Institute 3412 Hillview Avenue Palo Alto, California 94304 EPRI Project Manager l
Randall W. Pack Nuclear Power Division
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I ORDERING INFORMATION Requests for copies of inis report should be d:rected to Research Reports Center (RRC), Box 50490, Palo Alto, CA 94303. (415) 961-9043. There is no charge for reports requested by EPRI member utihties and affikates, contnbuting nonmembers, U S utility associations, U S government agencies (fedorar. state. and local). mede and foreign organizations with which EPRI has an informa n exchange agreement O. request.
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RRC will send a catalog of EPRI reports j
l Copynght C 1979 Electnc Power Research Institute inc EPHI authonzes the reproduction and distribution of all or any portion of this report and the preparat on of any denvative work based on this report in each Case on int
- Condition that any such reproduction.
distrat>utron. and preparation shall acknowledge Inis report and EPRI as the source NOTICE This report was prepared by the organizatiori(s) named below as an account of work sponsored by the Electric Power Research inst.tute Inc (EPRI) Neither EPRt members of EPRI the organizateon(s) n=med below. nor any person acting on their beha!f (a) makes any warranty or representation, express or emphed with respect to the accuracy Completeness. or usef ulness of the information Contained in this report. or that the use of any information. apparatus method or process disclosed in this report may not infringe privately owrwx1 nghts or (b) assumes any habihties with respect to the use of. or for damages resulting from the use of any information. apparatus, method. or process disclosed in this report Prepared by Lockheed Missites & Space Co, Inc.
Sunnyvale, Califomia x. - -
EPRI PERSPECTIVE 6.*
An earlier review of the control rooms of operating nuclear power plants uncovered many design problems having potential for degrading operator per formance.
As a re s ul t, the formal application of human factors principles was found to be needed.
This repor t demonstra te s the use of human fac tors in the design of power plant
- ontrol rooms.
The approaches shown in the report can be applied to operating power plants, as well as to those in the design stage.
This study documented human f ac tors techniques required to provide a sustained l
concern for - the man-machine interface from control taom <:oncept de finition to sy stem implementation.
It goes f ar beyond present control board design practic-es.
However, control board de signers intending to use this report as a design model should be aware of three limitations of the study.
First, although design 1
l engineers supported the human fac tors analyses, the depth of the study was limited l
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by the lack of their participation as an integral part of a design team.
- Second, the use of only three selected subsystems limited the study scope, so that overall l
l control room layout and sy s tems integration aspects we re scarcely addressed, l
l Third, the designs were based on analyses of startup, change of power level, and shutdown operations, and were modified by less detailed analyses of a few emergen-cy sequences. A more thorough design approach would include detailed analyses of all events shown to be significant by safety and reliability studies and by t;-
views of plant operating histories.
The suunary report will be of interest to anyone involved in control room design I
or ir. operator perf ormance. The full report will be of interest to anyone deeply involved in the design c 2 power plant control rooms. Designers of other types of i
control rooms, such as dispatch centers or process plants, may also benefit from the report.
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k Three closely related projects are in progress.
Publication of the final report I
for RPil26,. " Human Fac tors Review of Power Plant Maintainability," is expected in late 1979.
Completion of an improved approach for p rocedu res, RP1396, " Test of Job Performance Aids for Power Plants," is scheduled for early 1980. Final report publication for RP769, " Performance Measu rement System for Training Simulators,"
i is planned for late 1980.
These studies address both nuclear and fossil fuel power plants.
Randall W. Pack, Project Manager i
Nuc1 car Power Division 4
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ABSTRACT Human f ac tors engineering is an interdisciplinary specialty concerned with influ-encing the design of equipment systems, fac ili ties, and operational environments P*
to promote safe, e f ficient, and re liable ope ra tor performance.
Human factors approaches were applied in the design of representative nuclear power plant con-trol panels.
First, method s for upgrading existing ope rational control panels were examined.
Then, based on detailed human factors analyses of operator infor-mation and control requi rements, designs of reac tor, feedwater, and turbine-generator control panels were developed to improve the operator-control board interf ace, thereby reducing the potentini for operator errors.
In addition to examining present generation concepts, human fac tors aspec ts of advanced sy stems and of hybrid combinations of advanced and conventional designs were investigated. Special attention was given to warning system designs.
- Also, j
a survey was conducted among control board designers to (1) develop an overview of design practices in the indu st ry, and (2) establish appropriate mea sure s leading to a more systematic concem for human factors in control board design.
'Ihe study concludes that there is an urgent need for a human fac tors engineering design l
.7 guide, tailored to the special demands of the utility industry. Similarly, there is a need for a human fac tors standard which the utilities could use in specify-ing, developing, or evaluating new control room designs. The study also provides suggestions for future research directions.
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ACKNOWLEDGMENTS We are indebted to many individuals and organizations for their assistance, guid-ance, and cooperation in the design and execution of this study. While we were le fortunate in obtaining the cooperation of all major reac tor vendor organizations i
and several Arch itec t-Enginee ring (A-E)
- firms, the Westinghouse Corporation assumed a lead vendor role in providing the study team with sy s tems information required for human f ac tors analyses.
Also, Westinghouse made available its Training Center and staff for operational reviews of many of the design concepts presented in this re por t.
Joe Franz, Manager of the Process Computer Activity, and John O'Brien, a menber of the Human Sciences organization, were our primary contac ts with Westinghouse, l-(
Several consultants participated in the study.
Jeff Barnum, of the NUS Corpora-tion, provided the study team with the initial system familiarization training and insights into operational prac tices. Tom Sheridan, of the Massachusetts Institute of Technology, served as a consultant in the areas of human performance modeling and computer automation.
Joseph L. Seminara, IRSC Randall W. Pack, EPRI June 1979 l
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Section 1 INTRODUCTION AND SI'MMARY This study explored the feasibility and value of applying human fac tors engineer-ing methods developed in the aerospace and military contexts to the design of selected nuclear power plant control panels.
Human fac tors aspects of both con-ventional and advanced control and display approaches we re considered. The study also re viewed pre sent control board design prac tice s to determine how best to incorporate human f actors concerns in the design process.
This study was the direct outgrowth of an earlier eighteen month study identified as EPRI RP (Research Project) 501-1 and entitled, " Human Fac tors Review of Nuclear Power Plant Control Room Design." In the earlier effort, a Lockheed Missiles & Space Company human f ac tors team reviewed five present-generation operational control rooms and their correspxding simulators.
By means of extensive structured interviews with operators in operational plants and with tra iners associated with simulator-based operator training centers, a number of operational problems were uncovered. Human f ac tors checklists, based on aerospace standards and design criteria, were applied in evaluating man-machine interf aces ~ in the '~ five ~ con' trol ' rooms' review 2 The study ~~
Elso sp'ent' many
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team
' 5ours~~direc tly observing operator tasks in both operational and simulated control rooms.
Analyses of representative operator emergency tasks were conducted along with procedure evaluations.
Reported operational errors were probed for human factors implications and a variety of physical measures were taken in defining the operational environment and in evaluating anthropometric fea ture s of control rooms.
The human f ac tors problems revealed by these methods were extensively photo-documented for post-site visit analysea and to illustrate the problems observed in the ' final reporte.
The study revealed both major and minor problems in the design of control rooms, which inc reas ed the potential for operational errors and unnecessarily added to the training burden and the rigor of selection criteria for operator candidates.
The re sults of this; initial study are d cumented in a sununary report (EPRI NP 1-1
.~ _
r 309SY, dated November 1976) and an extensive 400 page final report (EPRI NP 309, dated November 1976).
! Although human f ac tors engineering has a history of over thirty years, the human f ac tors design principles initially developed for military and space p rograms to
. ensure operator e ffec tivene ss and reliability have not been gene ra lly or consis-
- i tently applied to the design of power plant operational work spaces. For example, four ou t o f the five control rooms reviewed revealed serious violations of anthro-
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pome tric standards where iMications were placed beyond viewing limits and controls j
were located beyond acceptable reach limits.
Control room configurationa varied widely, with some designs making for awkward ope rations necessitating additional l
manning when compared with more efficient con fi gu ra tions.
The extensive use of l
backrack areas which take operators away f rom the primary sphere of control end the practice of mirror-imaging control boards in multi-unit control rooms were found to be particularly disadvantageous from the human f ac tors sta ndpoint.
Control board designs were genera lly found to be excessive in size, lacking in func tional 4
arrangement of elements (sometimes necessitating a two-man operation of a control i~
and its associated display), and generally lacking in clarity of interrelationships 4
between panel elements.
In short, the control b oards reviewed had not been j
de signed to promote error-free operation, especially during potentially st re ss ful 3
circumstances.
The number and ragnitude of problems revea led in the initial human fac tors effort clearly indicated the need for additional research and led to the follow-on e f fort, EPRI RP 501-3, described in this re por t. The present study applied human fac tors
~
engineering approaches in deriving solutions and recommendations pertaining to the problems highlighted in the earlier study. The study scope ranged from an investi-gation of means for upl;rading existing operational control rooms to an examination of human fac tors concerns in advanced control rooms of the future.
METHOD 014CY This study applied well-established methodologies in developing and evaluating var-f ous control board design concepts. Figure 1-1 depicts typical human factors pro-gram elements extending from the initial concept development phase to system opera-tion.
The p resent study simulated an actual control board development program
~ including (1) system analysis, (2 ) ' func tion s and task analysis, (3) pre liminary board desi.gn e fforts, and (4) design verification efforts using mockups and rep re-sentative mesbers of the operator population. It was beyond the scope of this study to implement dynamic simulations. for test and evaluation purposes.
In addition, 1
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Figure 1-1.
Human Fac tors Program Elements the study was aimed not at developing hardware designs ready fcr p roduc tion, but rather at showing how to incorpora te human f ac tors methods and design principles into control board designs for nuclear power plant control rooms.
Subsystem Selection
- A review of control and display approaches for the entire nuclear power plant con-trol room is beyond the scope of the present study.
It was therefore necessary to j
limit the study to a set of representative subsystems within the bounds of project fu nding. Selected subsystems had to be those that, in combination, would represent the design problems that typify the control board design proceEs, and those that had evoked general operator and trainer - concern in EPRI RP 501-1.
The subsystems l
selec ted were reac tor control, steam gene ra tor. feedwa te r control, and the turbine-gene ra tor.
j 1-3
Study Tasks Subsequent to a review of the re levant literature, the following tasks were conduc t ed:
Analyses of Control and Display Requirements. A series of analy-e ses, f rom broad systems analyses to detailed task analyses, were conduc ted to identify and examine relevant man-machine inter-faces. The end product of this series of analytic efforts was a determination of the operator's informational needs and control
- options, Upgrading Existing Control Boards. The first concern in investi-e
,.j gating control b oard design approaches was to enhance control board designs that are currently operational or those that are near-operational and consequently difficult to modify in any sub-stantial way.
Recognizing that a 40 year li fe span is projected for nuclear power plants, the study explored measures that might be taken to upgrade the existing configurations from the human fac tors standpoint, without interrupting or delaying power generation.
o Fuman Engineering Conventional Control Board s.
This task in-volved the development of new conventional control board designs.
Starting with the control and display requirements identified in the analysis task, human f ac tors panel-design prin-ciples were applied in arriving at panel layouts for the three systems of concern in this study.
e Warning System App roaches.
Problems with existing annunciator warning designs were reviewed and candida te approaches were i
developed to re solve observed deficiencies.
Charac teris tics of
)
visual and auditory cueing devices we re reviewed and a number of candidate audio-visual warning concepts were advanced, e
Design Verification.
The human f ac tors design approaches devel-oped in the preced ing tasks were subjec ted to the scrutiny of board design personnel and trainers with operational b ack-ground s.
Designe rs reviewed the proposed arrangements from the standpoint of such constraints as separation and seismic require-ments, while reviewe rs with operational experience examined the
.anel layouts in terms of the demands of a representative set of nornal and off -prmal operational scenarios.
e Advanced Computer-Based Cathode-Ray Tube (CRT) Approaches.
Each of the uajor control room design organizations was visited to determine future trends in control room design. A detailed exam-ination of the major directions being followed in CRT formatting was conducted in the light of human factors considerations.
o Hybrid Systems. A readily discernible future trend is the inte-gration of advanced computer-based CRT capability with conven-tional board designs.
The advantages and potential drawbacks of these "hyb rid" concepts were examined.
1 Design' Prac tices Sur7ey.
In order to establish the feasibility e
of incorporating human f ac tors principles and considerations in control board designs, it was necessary to develop some 1
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h.
't appreciation of current ciesign practices and an understanding of 3
the constraints facing the designer.
Accordingly, a 30-item structured interview was developed and administered to 20 designers from major design organizations.
e Fu ture Study Needs.
This study revealed a number of possible extensions to the work conducted to date, including the neel for human factors design guides and standards. Also, research topics are advanced for developing empirical data bearing on a number of pressing design issues raised in this effort.
This brief outline of study tasks.is intended to serve as a road map through the remainder of this report.
ANALYSES OF CONTROL AND DISPLAY REQUIREMENTS A necessary initial phase of the human fac tors approach to equipment design is to i
develop a detailed understanding of the man-machine interface. This requires the application of a variety of analytic techniques based on a comprehensive under-
]
standing of the system and its func tional ch arac ter ist ic s, and a delineation of operator information needs and associated control options.
Systems Analysis Systems analysis was initiated with an intensive review of nuclear power plant con figu ra tions, the physical hardware and basic elements of the systems selected for study, control system characteristics, control board elements for a Pressur-ized Water Reac tor (PWR) plant, and operational practices associated with normal and o ff-normal operations.
In the course of this review and analysis of the selected systems, repres entative system schematics for a generic plant were devel-oped.
A func tional inter face sequence analysis wa s also performed, as shown in Table 1-1, to interrelate the operations of the three selected systems.
In addition to these preliminary systems analysis activities, the study team visited the Nuclear Steam Supply Systems (NSSS) vendor organizations in order to 1
expand the base of system inputs required for analysis. While all the major NSSS 7
vendors supported t' e study at various stages of the program, it was still neces-n sary to select a lead vendor for the primary source of systems data.
Analysis
- could not be performed expeditiously on all vendor designs because of variations in system design app roache s.
Westinghouse assumed the role of lead vendor and invited the study team to spend one week in detailed discussions with the various 5
func tional system designers. Westinghouse also provided relevant system descrip-tion documentation required for subsequent analytic efforts.
1-5
Table 1-1 SEGMENT OF FUNCTIONAL INTERFACE SEQUENCE FOR START-UP 4
Turbine-Generstor Reactor Control System Feedwater System System Pull' shutdown rods k.'
Prepare to go critical Take-the reae tor eritical Increase to baseline Transfer control of Prepare for roll stesm-genera tor wa ter Increase to 5% power level from auxiliary Begin roll feedwater to main feedwater regulating Increase speed bypass valves Control coolant tenve r-Perform trip tests ature while turbine is i
brought up to speed and Achieve operating generator is synchronized speed l
J Begin to pull rods Establish operating j
and increase power with voltage turbine load Synchronize to grid Transfer control to Increase load (1%/ min) main feedwater regu-t lating valves l,
Place in automatic Trans fer main steam control gene ra tor feedwa te r control to automatic control Monitor steam gener-7 ator level, steam flow, pressure, and feedwater pumps i
l Warm-up standby main Achieve desired load feedwater pump and level place standby pump in operation On going monitoring On going monitoring On going monitoring i
Functions and Task Analyses
.' Based.on the' systems analysis, the study team was able to identify the major func-
. tions' and subfunctions that the operator must perform in the course of monitoring and regulating the system.
Operator involvement in these subfunc tions 4
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wa s further broken down into discrete tasks.
In analyzing each specific task or man-machine interaction, the following f ac tors were considered:
e Decisions to be made e
Ac ti ons to be taken Ongoing plant processes e
e Control parameters j
e Control limits This proce ss re sul ted in the listings illustrated in Table 1-2.
This systematic examination of sequential opera tor-control board interf aces was intended to reveal display requirements and control options to be included on the control boards.
Decision-Making Analyses In the course of conduc ting func ti on s and task analyses, the more important or complex decialons f acing the opera tor were singled out for more detailed decision-making analysis.
A graphic logic flow for use by the operator in arriving at a dec ision was developed.
For example, the decision-making process requi red to determine if the rods are moving proper ly is illustrated in Figure 1-2.
At each step in the process, the analysis a t temp ted to determine the informational needs of the operator to allow him to resolve the problem appropriately.
Precautions Analysis Plant operating procedu re s sometimes provide the operator with separate listings of special precautions. These listings proved to be a use ful source of analytic data.
Each pre cau tion re la ting to s pec ific subsystems was examined in terms of error potential a nd possible means for ensuring e rror-f ree operation.
In some instances, it wa s apparent that a suitable indication or alarm was required to potential operation error.
In other cases, reliance on p rocedu res p revent a appeared adequate.
In still other instances, the possibility for error seemed suf ficient ly great that mechanical or elec trical interlocks to " design out" errors appeared worthy of further investigation.
Table 1-3 provides a segment of the precautions analysis performed for the reactor control system.
Control-Display Requirements Based on the series of ana ly se s described above, lists of control and display requi rements we re developed, some of which a re p re s ent ed in Table 1-4.
These requirements served as the foundation for the designs presented in this re por t.
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Table 1-2 SECMENT OF THE FUNCTIONS AND TASK ANALYSIS FOR REACTOR CONTROL SYSTEM Task ID Function Process Process Control Sub func tion Decisions Actions
Response
Parame te rs Parameters 4
Increase Power to Baseline Power Level (10-8 amps)
Establish start-SUR less than Pull rods Rods withdraw LVDT Digital up rate (SUR) 1 DPM7 CR increases position counter less than 1 SUR increases CR trend decade per SUR minute (DPM)
Monitor inter-IR level IR level mediate range greater than (IR) level to 10-II?
determine when on range Switch nuclear i decade Reposition Switch instrumentation overlap?
NIS position system (NIS) record er IR level recorder from switch lowest source range (SR) to IR level IR level on highe s t IR displayed?
recorder
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Continuously SUR less than CR trend; monitor SUR 1 DPM7 SUR IR and SR level Switch second I decade Reposition Switch NIS recorder overlap? IR switch position level'reater IR level
)
pen to IR g
ch ann,.1 than 5 x displayed
~II 10 7
IR displayed?
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It is important to note that, for economy of e ffort, the analyses were based on three operational modes:
start-up, change of load, and shut down.
'Ihe s e mod e s,
however, do not begin to describe the full range of normal and off-normal opera-tional scenarios.
Consequently, at a later date, when the first cut at panel de signs was completed, a visit was made to the We stinghouse Training Center to review the initial analytic conclusions with respect to a more varied series of l
normal and emergency operations.
These activities will be d iscuss ed further in the context of the design verification task.
1-8
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igital =
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moving?
oving?
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N N
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Decision-Making Analysis: Are Rods Moving Properly?
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Table 1-3 SEGMENT OF THE PRECAUTIONS ANALYSIS FOR THE REAC'IT)R CONTROL SYSTEM PRECAl*TIONS AND 1.INITATINS SYSTFM DESICM 8:'CfMENTMTIONS 3.
Criticality smet be anticipated any time the The estimated critical position could be tr:put, and control rods are being withdrawn or when boron a computer could examine this ECF and the actual dilution operations are in progress.
rod position. An interlock could be provided to prevent rod withdrawal if an ECp is not input.
4.
If criticality is to occur at conditions (i.e.,
This is currently handled procedurally. It is temperature, menon, and boron concentrations) good practice to always ut111:e an inverse
, dif ferent from those for which previous criticality count rate curve. If this were done automatically data is available and the differences are such as by the computer, it could always be plotted to to cause an increase of 0.5T AK/K (500 cpm) or monitor approach to criticality, more la core reactivity (as determined by procedure F. " Estimated Critical Rod Position Calculation" of (hapter 50), the approach to criticality must be guided by plotting an inverse count rate versus I
control rod position.
5.
Do not exceed a startup rate (SUR) of one decade The NIS tripe would probably prevent reactor per minute (1 DPM) unless authorised for special start-up such faster than 1 DPM.
It may tests.
be beneficial to have a separate trip on SUR.
6.
When the reactor is subcritical, positive reactivity This is currently handled procedurally. An shall not be added by more than one method at a interlock could prevent rod withdrawal time.
staultaneously with d!!ution when subcritical.
h The rod withdrawal and insertion progres shall be There are currently rod blockages and trips to followed except during low power physics tests, ensure the rod program is being followed.
control rod exercises and special approved teste.
A direct display of rod program position and actual rod position would assist the operator in satisfying this precaution, tJPCRADING EXISTING CONTROL BOARDS In addressing control board design approaches in terms of human factors considera-tions, our first concern was with the modifications that can be made to existing control boards that are operational or near-operational.
Dere are pre sently
'about seventy operational plants and more than an equal number of new plants where the control boards either have been designed or are in various stages of assembly and checkout. In applying human factors to existing operational designs, however, a number of compromises must be made, since. there is little opportunity to change the - position of - components, rewire panel elements, change circuitry logic, etc.
Consequently, much of the analytical work described above could not be applied to existing boards, because interruption of plant operation may not be allowed, nis groundrule limited us to a variety of' surface or " cosmetic" approaches which, if implemented, would considerably improve board operation, but would not fundamen-tally optimize che boards.
Board Enhancement Possibilities
- Problems consnonly observed in the course of earlier control room reviews were categorized as follows:
(1) those that could be addressed on a b ack fit basis 1-10
Table 1-4 DISPLAY REQUIREMENTS FOR THE REACTOR CONTROL SYSTEM
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E Parame te r Unite Range Accuracy a
y Comments NUCLEAR INSTRUMENTATION 1.
Source' Range (2 channels) a.
Count rate Counts 1 to 106
+7% of the X
Need quanti-per Tinear tative display second full scale plus trending analog capability voltage b.
Startup rate Decades
-0.5 to 5.0
+7% of the X
per linear minute full scale analog voltage 2.
Intermediate Range (2 channels) a.
Plux level Ampe re s 10-11 to
+7% of the X
Need quanti-(A) 10-3 linear tative display P us trending l
full scale capability analog voltage and +3% of the linear full scale voltage in the range of 10-4 to 10-3 A b.
Startup rate Dec ade s
-0.5 to 5.0
+7% of the X
per Tinear minute full scale analog voltage 3.
Power Range (4 channels, 2 chambers-each) a.
Calibrated ion Percen-0 to 125%
+2% full X
Need quanti-charnber tage of power tative display current (top full current of all 8 and bottom power values, plus uncompensated current trending lon chambers) capability 1
b.
Flux differ-Percent
-30 to +30%
34%
X ence of the dif-top and ferent bottom ion chambers c.
Average flux Percent 0 to 120%
+3% of full X
i of the top of full power for and bottom power indication ion chanber
+2% for racording l-11
while the plant remained operational, (2) those that could be remedied during an ex t e nd ed planned outage, and (3) those that did not lend themselves to back fit remedies.
'Ihe firs t category is of imediate interest here and included the following concerns and remedial measures:
e Functional Demarcation of Related panel Elements.
While related panel elements a re often grouped in meaningful clu s te rs on the b oa rd s, these clusters of controls and displays are usually not func tionally demarca ted such that the relationships
.4 re imedi-ately apparent to operators. Figure 1-3 shows a massive array of u nd i f f e rentia ted panel elements which force a " hunt and peck"
. j search for spec ific controls imbedded in a mass of many other identical controls. Whe re the panel elements have been arranged in a logical operational format (though this is not always the case), taped lines of demarcation can be added to highlight sub-groups of panel components.
e Labeling. Demarcation of panel groupings should be supplemented by a system of labeling that accentuates func tional subdivisions and avoids the re pet i tivene ss of pre sen t labeling practices.
Each subpanel area should be provided with a d istinc tive summary
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Massive array of identical control and display units with no clearly identified subpanel groupings or sumary labeling.
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label, larger 1 than labels applied to individual' panel elements.
Labels should also be placed consistently in relatiori to panel
-components, preferably above the components. Label coding prac-tices should be in stitu ted uniformly, such as using red b ack-1 grounds for important controls; the consistency and clarity of abbreviations should also be reviewed.
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.e coding of controls. One of the most serious problems with coding is of controls is the presence of large arrays of undifferentiated s
or identical controls collocated in a given area of the control b oard s.
Such. arrangements have caused inadvertent operation of improper controls.
Existing control boards should be examined
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shape coding, color cod-ing, or combinations of such coding practices.
Substitutions of control bandles c' different shapes can generally be accomplished with little at
..a impact on operations.
e Meters.
Meter limits should be reviewed for each panel and a
-consistent cod ing prac tice should be developed, such as green i
normal operating band, amber marginal bands on either side of I
normal, and red ou t-o f-limit band s on the high and low side as j.
appropriate. These color. bands should be af fixed directly to the meter scale where it is poraible to do so by easy removal of the meter cover. Meter scales which do not conform to human factors principles ' of design should be re placed, and room illumination should be modified where glare and re flec tions from meter faces obscures their readability.
s e-Indicator Lights. The color coding of indicator ligh ts should be reviewed to ensu re consistency.
Coding possibilities for the annunciator system should ' be - examined to differentiate between major problems and less significant information displays.
e Chart Recorders.
Some - of the chart recorders currently in use are overloaded and largely illegible. Some parameters of insnedi-ate -interest to the operator are buried and not available for as
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j much as four minutes.- Either additional recorders must be added, or meters should be sub stituted for important parameters, or a fast rec order cycle provision should be added to existing 4
recorders.
.This list of possibilities for improving current operational control rooms is not complete because each control room is a unique situation and should be reviewed on an.-individual basis for specific human fac tors reconenendations.
For example, multi-unit control rooms where two units have been mirror-imaged offer special problems ' and no easy solutions.
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It -is -important to note.that operators have been quick to discover the above-eentioned control room deficiencies. They have attempted to make " quick fixes" to
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the board s to improve the ir operability and avoid operational errors.
For fexample, adj acent identical control knobs have been painted different colors for coding purposes. Many such - fixes have, unfortunately, been prompted by an opera-tional mishap.< Also, remedial measures -have not been applied systematically to i'
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Proper enhancement of existing control rooms will require a care fully planned and concerted effort between plant opera-tions, engineering, and management.
Human Factors Enhancement: Examples To provide examples of methods for retrofitting existing operational panels, sev-eral representative panels were selected for study. An analysis was made of human fac tors p roblems, and. modification possibilities were considered.
The cases illu stra ted reveal a number of surface changes possible within the limits de scribed in the introduc tory remarks for this section. Applying human fac tors on an "af ter-the-f act" basis is generally a compromise and not always satisfying from either a human fac tors or aesthetic viewpoint.
Figu re 1-4 shows a Steam Gene ra tor Feedwa ter System control panel.
The panel allows monitoring and control of three steam generators having two motor driven main feedwa ter pumps and one steam driven auxiliary pump.
The most striking observation in reviewing this panel is the lack of apparent relationships between discrete panel elements. The operator must examine the legend on each individual switch, indicator, or meter to make any sense out of the panel.
Figu re 1-5 shows an a t tempt to functionally demarcate the panel shown in Figure 1-4.
The various functional groups of panel elements are bound together by taped lines. Within each grouping, sununary labels are introduced, thereby reducing the time required in scanning each individual panel element label.
Space constraints made it impossible to place labels consistently above or consistently below com-ponents. Furthermore, a white / black / gray coding approach is adopted for controls associated respectively with Steam Generators A, B, and C.
In assigning this code to the panel elements, it readily becomes apparent that no consistency was obs erved in the ordering of A, B,
C Steam Generator elements.
In some cases, a top-to-bottom A, B, C orientation is observed, such as MAIN FEEDWATER ISOLATION.
In other cases, a contradic tory b o t tom-to-top A,
B, C order exists, s uch as AUXILIARY FEEDWATER THROTTLE VALVES.
In other cases, a left-to-right A,
B, C
order is presented. In addition to coding the controls by color or shape, meters i
l should be color-banded to highlight normal and out-of-tolerance readings.
i Reorganization of Existing Control Boards In the preceding paragraphs, a number of surface changes to the existing boards were propos ed for consideration in an a ttempt to improve the operator-control b'oard. inter face.
Since we established as a groundrule the avoidance of disrupting 1-14 l
plant operations, such retro fits were minor in nature and the improvements achiev-able were correspondingly limited.
In this subsection we will consider more extensive modifications to existing operational boards, assuming that the plant will be down for several months and that this outage has been planned for some time.
This planned down-time provides an opportunity to upgrade control board s that have p roven especially troublesome from an operational or training s ta nd-point, in some cases because of extensive backfits over the years.
Redesign of control boards under the circumstances described will, in addition to all the fac tors considered earlier in this sec tion, allow freedom to regroup panel elements in more logical functional relationships than might have originally been the case.
Also, panel elements that have proven useless or obsolete can be removed from the boards to eliminate unnecessary clutter or distractions.
Suffi-cient space may be saved on benchboards to allow room for resting procedures on the board without risking inadvertent activation of controls.
Figures 1-6 and 1-7 provide an example of the possible modifications. Techniques of outlining, bordering, color c oding, and labeling we re incorporated into the revisions.
Panel elements were re ta ined within their re spec tive major console sections and the primary organization of major elements was not changed. A major change accomplished is the vertical alignment of the series of control-dis play elements associated with each of four steam generators.
HUMAN ENGINEERING CONVENTIONAL CONTROL BOARDS Up to this point, the focus has been on human f ac tors A proaches for upgrading existing operational control boards.
In this section, new ver, conventional con-trol panel designs were developed based on the requirements of a totally new plant.
During the analysis, control and display requirements for the operator to safely moni tor and control the plant we re identified.
The decision-making and task activities of the operator were examined to ascertain the actual usage of these data.
From this information, any adjacency requirements and appropriate presenta-tion modes were alsa identified.
For example, in the decision making analysis i
presented in Figure 1-2, we find that the operator is required to compare the rod positions indicated on the digital counters with the LVDT position indicators. It would be operationally desirable to present these displays in the same f orm and in the same general area on the control panel. However, in most operational plants, the digital counters are placed on the benchb oard while the LVDT's are on the vertical panel and pre sent rod position in analog form.
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Existing Feedwater Control Configuration engineered design, the two position i nd ica tors we re co lloca t ed in the same panel area and p re sen t ed rod pos i t ion s in the same form.
Similarly, in the precautions analysis presented in Table 1-3 (Item 7 ),
it is requi red that rod movement follow the withdrawal and insertion program. A direc t p re sen ta t ion of the program posi-tion would help meet this requi rement. The re f ore, a direct display of actual bank position versus p rog ram limits was incorporated in the human-enginee red reactor control panel.
Control Console Design As a fi rs t step, a control console con figura tion was requi red that (1) allowed enough space for nece ss ary panel elements and (2) add re ss ed the anthropometric l
charac ter is tic s of the operator. Unfortunately, comprehensive data describing the operator po po' _;i on is lacking.
The re f ore, reliance on military data was con-sidered to be a necessary and suitable expedient.
It was also necessary to l
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Teorganized Feedwater Control Panel (to be compared with Figure 1-6) consider that. a higher percentage of female operators may enter the control room in the fu ture.
Present generation control consoles have been found to violate anthropome tric limits for male operators, and would obviously present even greater problems in acconinodating the generally smaller female operators. Figure 1-8 pro-vides the configurations and dimensions for a stand-up console designed to accom-modate the anthropometric range extending from the 5th percentile female operator to the 95th percentile male.
The dimensions given are based on dynamic or ex-tended motion capabilities rather than static operator pos ture s.
Mockup evalua-tions were conducted with suitably sized test subjects to verify these dimensions.
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Control and Display Selection Given the console dimensions, it was necessary to selec t the panel elements that would be used to form the th ree s ubsy s tem panel con figu ra tions.
Human factors criteria for control-display se lec tion were reviewed against current ly available panel components. Bas ed on the analysis, determinations were made on the need for qualitative, quanti t a tive, or combinations of these display forms. When quantita-tive data was requi red, the best format for presenting s uch data was considered:
meters, chart recorde rs, counters, or variable format displays.
Similarly, re-qui red control options we re examined in terms of the need for continuous versus d is c re te settings, and in term 1 of the most appropriate device:
pushbutton, toggle switch, rotary selec tor switch, knobs, etc.
Many instances of improper control device selec tion had been uncovered in EPRI RP501-1.
Also, the earlier study revealed that the use of excessively large controls unnecessarily increased panel size.
The re fore, an e f f or t was made to select panel elements that took as li ttle space as possible, but still satisfied other operational requirements.
Panel Arrangements Five basic principles of control panel arrangement were reviewed for application:
sequential ordering of panel elements, mimic or graphic pictorial p resenta tions,
prime loca tion s for important or critical displays, location preference based on f requency of use, and functional grouping of related panel elements into distine-tive sub pane ls.
Also, where it was a consideration, location pre ference was given to right-handed operation. These panel layout principles am not mutually exclu-sive and all were used to some extent.
However, the predominant layout principle, as will be shown below, was the functional grouping approach. Mimic arrangement s,
which operators tend to pre fer in comparison with their existing b oa rd s, were a t temp ted but generally use up too much panel space a nd o f fer no substantial advantages over a well organized panel grouped by func tion.
Other major concerns in the development of pancl arrangement included (1) use of c learcu t labeling prac tices to aid rapid and accurate identification of panel ele-ments, (2) review of control locations to determine what measures we re requi red to sa feguard critical controls from accidental activation, (3) allowance of room for p rocedu res on the bench boards, and (4) determination of the best control-display coding p rac tice s.
The latter de si gn topic raised questions which were difficult to resolve. The study team concluded that the military " green board" display cod-ing and logic approach has many merits, even though its use of colors is in direct conflict with the tradition of the power i ndu s try which uses red for a normal
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We military operator is trained to re s pond to exceptions to the normally g reen pa t te rn of panel displays.
Such exceptions would be amber lights for cautions or the early states of a mal f unc tion trend, and red Indica-ti ons for a more serious ma l func ti on.
Fu r thermore, p re s ent dedicated control boards do not incorporate the circuitry logic to inform the operator when a red-open condition or a g reen-clos ed condition is either a normal or abnormal con-dition which the operator should attend to.
Some feel that it would be extremely di f ficult to forsake the traditional color code and that retraining of experienced operators would pre sent too many problems.
We study team feels, however, that the.meri ts of a " green board" a pp roach to display codi ng strongly outweigh the disadvantages of this break with tradition.
Human Engineered Panel Layouts Based on the foregoing analyses and applica t ion s of human f ac tors design princi-ples, layouts we re developed for the th ree subsystems dealt with in this study.
Several versions of these layouts were developed as will be described below in the context of a discussion of design evaluation methods.
Figure 1-9 depicts the reac tor control panel and reveals the layout of functional groups of control and display elements. Similarly, Figure 1-10 presents the feed-water control panel and provides the underlying framework of subpanel groupings.
These panels should be compared with cu r rent operational panel designs shown in Figures 1-1 and 1-11.
The most salient difference is the amorpho in charac ter of-existing designs as compared to the c l ea r-cu t, func tionally demarcated panels resulting from the human f ac tors effort. nis difference accounts for the numer-ous attempts made by ope ra tors to modi fy existing b oards using taped lines of demarca tion to clarify panel relationships and facilitate rapid identification of individual controls and displays.
WARNING SYSTEM APPROACllES A primary task of the operator is to maintain cognizance over plant status and
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Beyond this, he nus st con firm the e f fec tivene ss of his actions and re store the warning system to a state of readiness to re s pond to any subsequent p roblems.
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Undifferentiated Panel Design Which Operators Later Modified by Adding Taped Lines of Demarcation The earlier survey of five p re s ent-gene ra ti on control rooms (EPRI RP 501-1) revealed significant problems with existing sarning systems.
Briefly, anywhere f rom 400 to more than 2000 annunciator lights are typically arrayed in matrices running along the upper periphery of the control boards as shown in Figure 1-12.
l Some of the major problems with these systems are the following:
e Operators are given far more information than they can reasonably assimilate when a major anomaly occdrs.
I The annunciator panels have become a catch-all for a wide variety
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A horizontal band of indicator lights above the control boards plus associated auditory cues constitutes the warning system.
e Annunciator legend s are not sized to be read re liably from the opera tor's normal station.
Spec ifi c annunciators are not always located above or in clear e
proximity to their associated quantitative displays and controls on the control board panels below the annunciator matrices.
o Opera tors are plagued by false or nuisance alarms which tend to induce the " cry wolf" phenomenon.
In view of the special icport ance of the warning system, it was isolated for l
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First, general human fac tors 1-26
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(1) alerting signals must a t trac t the operator's attention regardle ss of his position in the control room, including backrack areas, (2) while commanding the - opera tor's attention,' alerting signals should not be so startling or disrup-
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Visual Warning Approaches f
Seven candidate visual warning approaches were ' examined and are briefly described as follows:
o Integration of Warning Signals Into Primary Control Panels.
Rather than isolating all qualitative warning displays into a separate annunciator panel, it is possible to integra te such qualitative displays with associated qualitative-read-outs and con tro ls, his requires that such warning displays be highly d istinc tive, such as flashing red warning lights incorporated in a well-designed " green board" panel layout.
e Master Warning Displays. To reduce the visual scan time assocl-ated with the first approach, a master or sununary alarm indica-tion could be a ssigned to each major system or corresponding board segment. Each summary indication, which would flash on and off when ac tiva ted, could be placed above the panel segment of direc t re levance (see Figure 1-13), or the sununary annunciators could be integrated into one centrally located annunciator panel shaped to provide geographic correspondence with the control board layout as shown in Figure 1-14.
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Redundant Warning Information. One method for providing an over-view of plant status via an a; inciator band of qualitative i ndi-cators and also satisfying the requirement of functionally group-j ing qualitative and quantitative information is to provide redundancy of information on the upper and lower areas of control b oard s.
21s approach is already being followed to some extent in some plants.
e Prioritized Annunciator Displays.
Rather than assigning all indications to the traditional annunciator panel
. qualitative location, a review of such indications reveals that a fraction of
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di rectly into the Control Board panels below.
Ris prioritiza-s tion re flects the need to be-able to oversee, at a glance, plant and process status while relegating lesser or more detailed indi-cations to the 'subpanels where system diagnosis and control can be e f f ec ted.
The feedwater annunciator panel shown in Figure 1-10 represents this approach.
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Correlated Annunciator Panel and Control Board Arrangements.
Pre sent day annunciator panels give no clue as to the re la tion-ship of a given annuncia tor light to the location of its related quantita tive displays below.
The operator learns such associ-ations through experience. However, by configuring the annunci-ator panel so that its arrangement is correlated with the arrangement of the subpanels below, using the same logic as was illustrated in Figure 1-14, the transition from annunciator to the control boards.is le ss likely to produce errors of misassoci-
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As in the p receding pa rag ra ph, only summary indications would be included.
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Generally, such arrangements require more panel space than desirable and do not offer clear advantages over a well-designed panel based on prin-ciples of clearly demarcated func tional group ug of panel ele-ments.
However, there may be an application for mimic arrange-ments of annunciator panels.(see Figure 1-15).
Such panels would provide some insight into the relationship of a given malfunction indication to the system or subsystem in which the problem occurs and should, thereby, aid diagnosis and control of the problem.
1-28
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e Hierarchical Annunciators Panels. Another variation of the pri-oritized annunciator concept described ~ above is to arrange the annuncia tors in a hierarchical or py ramidal order f rom the most i- . general L to the nost ' specific.. At the apex of the py ramid we might have FEEDWATER SYSTDf. The next level might include indi-vidual susumary STEAM CENERATOR lights, followed by a third tier of STEAM CENERATOR FIDW, LEVEL,. and STEAM alarms for each steam generator, etc.. A hierarchical atrangement based ' on importance is also possible. Such an arrangement might be useful in allow-ing the operatur to address the more important problem when con-fronted with simultaneous alarms. Auditory Warning Signals Visual warning systems may suffice when an operator is confined to a fixed station and his control panels are always in view. Such is certainly not the case in a nuclear. power plant control room where the board s are relatively large and the opera tor must constantly move around, sometimes outside the primary control sphere. Con sequen t ly, visual alerts, which are highly direc tional, must he sup-plemented with auditory cues which are omni-directional, that is, capable of ac-quiring - the operator's attention regardless of his location within the control +. While all the control roome visited by the study team use auditory cues in room. I association ' with visual annunciator systems, the Information pre sent ly conveyed via the auditory channel is generally limited to a distinctive sound, directing the operator 's attention to. the boards. e {, This study examined a variety of possible auditory signals that can be used in conjunction with the visual wa rning candida tes outlined above. The aim was to expand the information contenc 'of the auditory warning system so that board scan time could be reduced, correspondingly reducing the time requi red to identify the nature of the al,trm. The auditory candidates considered were as follows: General Auditory Alert. Generally, one distinctive sound can be e u sed simply 'to direc t the operator's vis u,41 attention to the j boa rds. A variation of this approach, observed at one plant, is to have the warning signal emanate from only one o f a number o f - j speakers, the one located in association with the affected annun-j- clator matrix. Two-Level Auditory Alert. A two-tone auditory alert system could e be devised to differentiate between urgent warnings and less l significant cau tions or advisory in forma tion. - 'Ih i s two-level { sound code would allow the opera tor to determine whether he should. stop what he 'is doing at the moment of the alert,.or continue what' may be. a more critical task until possible to leave. This system could : also be correlated with color coded. annunciator displays, e.g., -red for najor warnings, and amber for cau ti ons. 1 1-30
e Coded Non-Verbal Signals. Six to ten distinc tive. sounds could be employed for c oding purposes. For example, warnings associated with the various major plant systems could be coded auditorily so that the operator would insnediately direct h is eyes to the appro-priate sec tion of th board s. Alternatively, distinctive sounds could be associated with major emergencies, such as MAIN STEAM TUBE RUPTURE, assuming that the warning system logic (a disturbance analysis sy stem) was capable of signalling a major disturbance direc tly. Since such emergencies would be so infrequent, periodic rehearsals of code meanings would be necessary. o Verbal Warning Systems. Considering that present day control rooms can have f rom _ 400 to 2000 visual annunciations, c oded auditory signals may not be the best supplement to a visual warning system. Verbal warning approaches, initially developed for airc raf t appli-cations, may hold greater promis e. Such warning systems could p re s ent taped or synthetic speech messages over a control room s peaker. Such messages would be prioritized so that i-the case of simultaneous warnings the most importarx would be delivered first. Preferred Audio-Visual Candidates It is apparent from the foregoing that numerous alternative combinations of audio and visual warning approaches are posrtble. Research is insufficient to allow the selection of the one best audio-visual warning system. De most promising audio-visual candidates were selected by applying the following criteria: e The operator should be alerted to the onset of a cautionary trend, system malfunction, unsafe condition, or process distur-bance in the shortest possible time. e The operator should be provided the means to correla te qualita-tive alerting ' information with associated quantitative displays, in order to allow an accurate determination, in the shortest pos-sible time, of the nature and cause of changes in system or proce ss status e
- Ihe operator should be able to identify and associate available control options.with specific disturbances quickly and accurately so that appropriate control actions can be effected manually or the initiation of au tomatic sy s tem response can be easily verified.
The opetrator should be able to identify the gravity of any alert-e ing signal from any position in the control room so that he can determine whether to interrupt or. continue on-going tasks. e The operator, watch foreman, and other intere sted parties who f requent. the control room should be able to make sununary judg-ments regarding plant status 17 ' means of the annunciator-warning system, without having to make a detailed scrutiny of all or most disc rete control panel elements. Using these evaluation criteria,.the following audio-visual combinations appear most promising: e Correlated annunciator panel and control - board arrangements coupled with a verbal warning system 1-31'
. = -. f a Correlated annunc iator panel and control board arrangements coupled with coded non-verbal auditory signals I -Mimic annunciator panels coupled with a verbal warning system e o Mimic annunciator panels coupled with coded non-verbal auditory signals These pre ferred candida te s were chosen because of operational efficiency, with insufficient consideration of design complexity factors. 'the se judgmental evalu- .1 atior.s should be substantiated by empirically derived mearure s of the re lative effectiveness of alternative audio-visual warning approaches. For example, there is some concern that operators might object to the chattering of a verbal warning system if the alarm rate were excessive. CONTROL BOARD DESIGN EVALUATIONS t An essential step in the human fac tors approach to control board design is design evaluation or verification. Analytic app roache s, no matter how systematic or thorough, can overlook or fail to anticipate operational realities or deep-seated operator preferences. There is always the concern that long established opera-tional response patterns may lead to a negative transfer of training when the opera tor is confronted with new board configurations that depart from traditional designs. It is, therefore, important to interface with operational personcel, not only when establishing p reliminary design requi rements, but also at periodic intervals during the design proce ss. The use of three-dimensional mockups of candida te design concepts are an indispensible aid in verifying the adequacy of man-machine in te r face s. Such mockups permit static simulations or walk-throughs of operational s equ ence s,' both normal and o ff-normal. These so-called static simulations allow evaluations of anthropometric fac tors, panel layout efficiency, sufficiency 'of displayed information, and adequacy of control options, among a j host of other variables. In fac t, a human factor design checklist (see Figure ~ l-16) is. advisable to ensure thtt no significant f ac tors are overlooked. Such r checklists should be used, not only by human fac tors specialists on the design team, but more importantly by the customer to ensure compliance with human f actors standards. 1-32
HUMAN FACTORS ENGINEERING DESIGN CHECKLIST FACILITY _ CONSOLE (5)/ PANEL (S) I DEVICE (S) 13 o r a x 42 5.2.2.1.16 Lamp Removal, Method. Where possible, have provisions been made for laap removal from the front of the display panel without the use of tools, or by some other equally rapid and convenient means? NOTES: 43 5.2.2.1.17 Lamp Removal. Sa fety. Have display circuits been designed so that bulbs may be removed and replaced while power is applied without causing failure of indicator circuit components or imposing personnel safety hazards? NOTES: 44 5.2.2.1.18 Indicator Covers. Are legend screen or indicator covers designed to prevent inadvertent interchange? NOTES: 45 5.2.2.1.19 Color Coding. With the exception of etrcrew statio*) signals which shall conform to MIL-STD-411, and Air Force training equipment which shall conform to MIL-T-27474, do te gnsillumirated ines.ndescent displays conform win the following color cc ding scheme, in accordance with Type I - Aviation lors of MIL-C-250507: (a) Is RED used to alert an operitar that the system or any portion of the system is inoperative? (b) 15 FLASHING RED used only tt denote emergency conditions which require operator action to be take. without undue delay, to avert impeding personnel injury, equipment damags, or both? (c) Is YELLOW or AMBER used to idvise an operator that a condition exists which is marginal, or to a.ert the operator to situations where caution, rech ec ic, or unexpected d alay is necess:ry? (d) Is GREEN used to indicate t'ist the monitored equipment is in tolerance or a condition is sat D f actory and that it ie all right to proceed? (e) Is WHITE used to indicate s f atem conditions thct do not have "right" or " wrong" implications, such as alternative functions or transitory conditions provided such indicat on dws not imply success or failure of opera tions? (f) Is BLUE used for an advisccy light, and avoided wherever possible? NOTES: j l' Figure 1-16. Sample page from a military human factors design evaluation checklist, g,33 1 1 -e, --n.
he pre sent study provided for two forms of design reviews or evaluations: the first with a group of operationally oriented trainers at the Westinghouse Operator Training Center, Zion, Illinois, and the second with a sample of 25 control board designers d is tribu ted ac ross the major Nuclear Steam Supply Sys tem (NSSS) and Architec t-Engineering (A-E) fi rms. The operational review took place when the con-trol panel designs presented in the preceding sections were at a preliminary stage of development. He reviews by boa rd designers were scheduled subsequent to refinements made to the panels as a result of the operational critique. Operational Review The "first-cut" at the three major panel layouts developed was based on an analysis of control-display requi rements casociated with start-up, load change, and shut-down operations. Analyses of these three modes served as a good beginning for study purposes but fell far short of the analytic foundation required for an actual design and development program. To more fully explure the range of operator activities, a week was spent with four trainers havi ng extensive operational b ackground on We stinghouse systems. The tra ine.rs first revle. red the panel layouts in terms of the opera tional modes on which the analyses were p red ica ted. Subsequently, the panels we re reviewed in ] terms of a series of standard major emergency sequences used in the training pro-grams at the Zion training centers main steam line b reak, loss of a feedwa ter pump, a dropped rod, and condenser vacuum problems. The number of emergency opera-tional scenarios reviewed had to be constrained by the time and budget limitations of the study. The study team felt that a fairly comprehensive evaluation of design c oncepts was ob tained from these wa lk-th rough s. Had th is been an actual board development effort, however, an attempt would have been made to walk-through all or most normal and off-normal operational sequences. Se setting for these operational reviews proved very favorable. The mockups to be evaluated were placed in a special training room that included a half-scale mockup of the Zior. plant control room. When some questionn arose as to current opera-tional or design practices, a ready comparison to the Zion control room design was available. Also, when the dynamic training simulator was not in use for training purposes,. the study team was invited to witness the patteen of indications and con-trol manipulations associated with the selected emergency operations in a realistic real-time mode. 1-34 \\'
Bqsed on these reviews, a number of changes to the initial panel designs were indi-cated. A comparison of Figures 1-17 and 1-18 provides an indication of the modifi-cations made to accomodate operator judgment and experience. The initial arrange-ment of Nuclear In s trumenta tion System (NIS) and control rod position information on the veritical panel is shown in Figure 1-17. This arrangment was based on the operational anayises that preceded the panel design effort. During the walk-through of start-up operations, the test operators found this arrangement to be awkward. Wen moving control rods, the operators initially check the rod position in formation to verify movement, and subsequently check the NIS displays. To pro-mote a more natural le f t-to-right p rog re s sion, it became apparent that the rod positional information should be placed to the left and the NIS information to the right as shown in Figure 1-18. The opera tiona lly oriented trainers who reviewed the proposed designs appeared totally sympathetic to the aims of the study team in introducing human f ac tors con-siderations in panel design. It was their general consensus that improved fune-tional groupings of panel elements, enhanced labe ling, and the simplified warning system proposed would ease the task of the trainer and tend to reduce operational errors. Design Engineering Review Human factors specialists typically make their contributions to equipment design in a design team setting. Day-to-day interactions with other designers, each with a special f ocu s, allows re solution of numerous trade-off decisions typical of most design and development e f f or t s. The p re s ent study lacked such constant inter-ac tions with other design specialists, periodic reviews with management personnel, or expre ssions of client p re f e rence s. To partially compensate for the absence of these crucial tests of design app roaches, visits were made to the major control room design organizations for critiques. The 25 designers who participated in these reviews were invited to coment on such design 'ac tors as (1) compliance with seismic and separation criteria, (2) produc-ibility of the panel designs, (3) operational characteristics of the panels, and (4) the value and feasibility of incorporating human f actors engineering principles into panel designs. The designers were helpful in raising concerns over instances was inadequate or whe re seismic criteria we re only whe re separation of components marginally satisfied. Wif e recomended design fea ture s such as "g re en board" logic coding of indicator ligh ts we re perceived as introducing added design com-plexity and costs, all of the human fac tors recomendations were felt to be both 1-35
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well within the state of tha art and successfully applied in other industries. On the whole, the response of designers, as was the case with the trainers, was essen-tially and uniformly positive. One designer noted with some envy in his voice that the study team was allowed to create human enginee red designs due to the lack of changes introduced by the client and the absence of last-minute additions made by functional system designers af ter the layout was supposedly "f rozen." ADVANCED COMPUTER-BASED CRT APPROACHES There is a marked trend towards advanced computer-based CRT control rooms. As one . ] advanced system designar observed, "This is the last major industry to move in the direc tion of advanced control-display techniques!" Each of the major NSSS vendor organizations is developing advanced control rooms, with some on the drawing boards, others in mockup or prototype form, and still others being assembled and prepared for operation within a year or two. To obtain an overview of developments and trends in future control room design, a tour was made of the primary advanced control room design organizations. Discus-sions with design engineers and design reviews permitted the study team to delin-este the key issues involving human f actors concerns discussed in this section. General Characteristics of Advanced CRT Approaches Advanced control room concepts are defined as those designs that incorpora te CRTs as the primary display interface - instead of conventional hardwired indicators and l i rec orders, thus allowing for much more flexibility in the presentation of informa-tion to the operator. This increased flexibility provides the greatest inherent potential for improved operations. At the same time, if the man-machine interface is not human engineered, this flexibility can create, and in some cases has created the setting for a degraded operator-control console interface. In addition to this inc reased flexibility of the man-machine interfaces in an advanced control room, the mode of presentation is different from that of a con-ventional control room where information is presented in parallel. With dedicated in s trumentation, all information is continuously available to the ope ra tors, and based upc their training and experience, they extrac t specific infori ition and data depending on the situation. In a CRT-based display system, the information is pre sented primarily in a sequential manner. The _ designer predetermines what spe-cific group of data to present on a given display page, and the operators take spe-cific actions to retrieve the display page of interest. The ease with which the opera tor can retrieve pertinent data in-the advanced control room depends to a 1-38
large extent on the degree to which the designe r (1) considered the operational interf ace and accessing strategy when structuring the information, and (2) organ-ized it in terms of display pages. The information structure and accessing scheme should be developed primarily to aid operational use, rather than to minimize design or so f tware requirements. The human fac tors engineering effort required to ensure an operationally efficient interf ace is more extensive for the advanced control room. It is easier to compen-sate for a poorly human-engineered conventional control room through extra training and staffing e ff orts than it will be for an advanced system with a cumbersome ac:.assing strategy or excessively high-density displays. Analytic Requirements The analytic foundation for the advanced control room is necessar ily more extensive than that for a conventional control room. Whereas the designer of a conventional control room has to decide only once what information to include on the panel, in what form, a nd whe re, the advanced control room designer addre sses these issues over and over for a multitude of display pages. The re fore, the analyses must be conducted at a much more detailed task level for the advanced control room. Information Accessing Schemes One of the grea te st challenges confronting de signers of advanced control rooms is the development of schemes to enable the opera tor to access required information e ff ec tively. Advanced CRT displays provide a narrow window into the system, pre-senting at any given time no more than 5 to 10 percent of the total available in formation. Ideally, it should be as easy and natural for operators to extract information from the computer as it is for them to scan the conventional control room to obtain pertinent in formation. During a major transient, it is extremely important to provide the operator with means to focus on diagnosis of the problem and identification of appropriate corrective ac tion. At such times, the operator should not be p reoccupied with the intricacies of the display system logic to retrieve desired information. Two accessing schemes were examined, both of which are being developed by NSSS sup-pliers. The first organizes the information by system and then by the level of det. ail within a system. The second technique also is organized by system, but the subgrouping is based upon the plant operating sta te and the information set required by the operator for each particular mode. 1-39
Although an organization based upon the information requirements of a particular state offers the _ opportunity f or a very smooth and ef ficient interface, it is only as good as the operational analyses that determined the information requirements for each state. If time and effort a re not inve sted in operational analyses early in display development, the potential for a degraded interface is high. Organizing by information detail leaves the operator with the task of searching out required information from the indexing structure. However, as the operator becomes inc reasingly familiar with th is s truc tu re, he will probably be able to find the de sired information quickly in the same way that he can find a particular control or indicator on a massive conventional control board. In all likelihood, some com-bination of the two information-accessing approaches will be most e f fec tive. Response time is an important c onside ration in developing an information accessing system. If an operator requests a particular display, it should be on the screen within 2 to 3 seconds. If the system does not respond within one second, an "in-progress" message should be provided to the operator. Interfacing Hardware Having developed an information s t ruc ture and accessing scheme, the actual inter-f acing hardware requirements can be addressed. Once an operator has determined the display page desired, this selectim information must be input to the system. A communication s t ra te gy and operational plan encompassing the entire control room with its multi-CRTs shotid be developed. Some of the items to consider include the following: (1) Should there be a dedicated interf ace device assigned to each CRT or is one device for every two or three CRTs sufficient? (2) Should there be a master interface device fr9m which all CRTs can be controlled? An swers to such questions regarding the overall operational interfaces will influence the selection of the actual interface devices. Several al terna tive hardware options reviewed include the followings alpha-numeric keyboards, light pens, cursor controls, joy-s'icks, acoustic pens, and trackballs. Information Coding With a system as complex as a nuclear power pic? and its associated instrumenta-tion, the c oding of information to aid op era tor processing and i nterp reting is essential. The best format should be developed for presenting the information to the operator prior to including the coding features; coding shoutd not be expected to " crutch". a poorly formatted display, but should enhance an otherwise acceptable ' display ' format. the designer should optimize use of all coding techniques (e.g., 1-40
intensity, reverse video, symbology, line texture s, size) and not rely exclusively on color, which is the most frequently used coding dimension with the CRT display syst e ms. In fac t, because most color CRT systems furnish eight colors, it is f re-quently overused and may well result in degraded, rather than improved, operation. Color should only be used where a func tional need exists to differentiate two - items. Frequent ly a designer will group similar things (examples are labels, units, system titles, and components) and assign a different color to each one, even though in actual operations there is no functional requirement for an operator to discriminate among these variour items. The use of color in this way may result in a more aesthetically pleasing display with all things clearly categorized, but the color is irrevelant to actual operations, complicates the operator's task, and may in f act degrade operations. Figure 1-19 illustrates a preliminary display for-mat where color has not been used to its best advantage. Figure 1-20 shows how the CRT format might be enhanced through more effective use of color coding. Color is a very strong coding dimension and is best re served for items of greatest func-tional importance, such an dy nsmic information and alarm conditions. Other coding dimensions should be incorporated for the mora rou tine differentiations in the display. Interactive Techniques Coding technique s are not the only means available to aid operator processing and interpretation of complex CRT displays. Inte rac tiu capabilities can be incorpo-rated into the system design, enabling operators t. mcdify and amplify displays to reduce clu t ter. Experienced ope ra tors will only if requently need to refer to parameter labels and engineering units; therefore, this information could be sup-r re ss ed on the display page unless reque s ted. Limits could be provided inter-actively at the operator's reque st, but would be supp re ss ed at other times to reduce clutter in the display. Grid-lines and scales on graphical displays could on request only. On trend or graphic displays, an operator could De provided interactively request a digital display on the coordinate of some specific point on a cu rve. Interactive trend graphs could be provided when an operator suspec ts a D developing problem. 'Ihe operator could input the desired time period for the trend and specify other variables for simultaneous trending if he suspects there is a relationship between them and wishes to compare them. Although inte rac tive fea-tu re s require extra efforts for developing the supporting data structures and soft-ware, they will provide a smoother, less frustrating interf ace for the life of the system. i 1-41
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Alarms One of the major unsolved. issue's con fronting the designe r of an advanced control room is the presentation of alarm information to alert the ope ra tor to a system anomaly or pending problem. Integrating alarn information into regular CRT display pages by changing the color of the display parameter and blinking the value to attrac t the operator's attention to the change is fairly straight-forward. While this can e f fec tively handle the situations whe re a handful of alarm conditions occu r, such a strategy will soon become overburdened when confronted with the ,ss of alarms generated almost simultaneously during a major casualty. Although CRT-based alarm displays can present a lot of information in a small space, care must be tak en to develop the appropria te mix of dedicated and CRT-besed alarm i nd ica-tions. - The use of CRT-based alarming may not eliminate the need for dedicated annunciators in the advanced control room. Integration of Controls and Displays As with conventional control rooms, the de signe r is confronted with the problem of functional integration of controls and displays. With CRTs as the primary source of display information, it is impossible to locate all associated controls adjacent to the affected parameter displays. Other schemes for achieving readily apparent control and display re la tion ships, without the benefit of actual geographie group-ing, must be devised. Two control arrangements were examined: mimic or flow lay-outs and func tional grouping arrangements, both helping the operator to quickly ' and accurately locate a specific control of interest and associate it with the related CRT display A computer-based display system can further assist the operator in associating a control action with the a f fec ted parame tric display by highlighting that display on the CRT screen when an operator inputs a change in valve position or switch status. Thus, by systematically arranging the controls and by highlight- -ing the.affec ted parameter, the impac t of the physical separation of controls and displays can be minimized. Also, some approaches allow interactive control directly on the screen, as with light pens. 1.* Procedural Integration In the advanced riulti-CRT control room, it is possible to display procedural infor-mation on a CRT, allowing operators in different locations to access the same pro-ced u re. During an emergency, the procedure ' could be displayed automatically, or a - functional keyboard could be: provided so that _ the emergency operating procedures are one keystroke away. A section of each display page could also be used to l .1-43 t I
pre sent re levant procedural information direc tly to the operator; however, one designer indicated that there were legal liability reasons preventing the implementation of this approach by the vendor. Environmental Considerations There are.many fac tors to consider when designing an integrated, advanced control room. Two of these that can significantly impact operability are viewing distance and viewing angle for CRTs. The distance from which an operator can read a CRT is a function of the CRT size, ambient illumination, contrast, and specified character size and configuration. A control room should be designed with maximum and minimum viewing distances and line of sight angles to the display surface. Clare is another problem to consider when designing both the console configuration and ambient illumination system for an advanced control room. Although there are some surface measures that can reduce glare from the CRT surface, there is no sub-stitute for an integrated approach to control room illumination design. Clare min-imization should be a design goal when determining the control room illumination source and the positions of the CRT display units within the control board. Display System Parameters In developing the specification for an advanced CRT control room, there are many l display system parameters affecting the interf ace with the operator. From a human f ac tors stand point, it is important that these parameters be defined with consider-ation for the operational use of the system and the limitations and capabilities of the human operator. Character attributes that affect operability include character height, re solu tion, viewing angles, strokewidth, aspect ratio, case, spacing, and character matrix con figura tion. Hardware features that impact operability include ref resh rate, misregistration, response time, and contrast ratio. The parameters in Table 1-5 re pre sent the reconsnended values based on available ~ research data for a human engineered CRT based display system. Shown are the most desirable values for each parameter in terms of the man machine inte r face. In the process of actual display design, trade-offs will be required which may force com-promise s. The value of these guidelines is that compromises become visible and the relative degradations introduced by alternative compromises can be evaluated. 1-44
Table 1-5 RECOMMENDED VALUES FOR SELECTED DISPLAY SYSTEM PARAMETERS Parameter Rec onssenda tica Charreter Height 21 min of visual are for color (1/6 in at 28 in. viewing distance) min. ; 50 minutes maximum 30 min. for off-axis viewing (1/4 in at 28 in. viewing distance) Resolution Alphanumeries 9 to 10 lines minimum 14 lines for off-axis viewing Symbolic 17 lines minimum 25 lines for eff-axis viewing Strokewidth 1:10 maximum Narrower lines okay because of irradiation on CRT Aspect Ratio 5:7 to 2:3 minimum lit for off-axis viewing Character Case Capital Letters Spacing 75% Intercharacter and Inter: ne Character Matrix System Dependent (picture element dimensions determine desirable matrix configuration) Refresh Rate 60 Hertz minimum Misregistration 50% maximum Response Time 2 to 3 seconds maximum (operator request / 1 second desirable action) Contrast Ratio 10:1 minimum (variable operator control) Display Formatting ~ Little hard research exists regarding the most effective way to format information on a CRT screen. We know in general what information an operator needs to be able to access, bu t we have little empirical or operational data to determine whether the inf ormation is be st displayed on mimic diagrams, in digital form, on analog bar charts, on trend diagrams, or in other formats. There are, however, some genet.:1 principles _ and guidelines for display f orma tting that should be observed when arranging information for an opet stor to interpret: e The density of a display page should be managed so that informa-tion is not too tightly packed on the page. Empirical evidence shows that an operator will scan the upper right quadrant of a CRT display significantly more often than the other quadrants. The upper le f t quadrant is the next most frequently scanned 1-45
s 4 ' quadrant,.followed by : the lower left and lower right. There fore, the designer. should attempt to ' pl ace important information, like alarm status-. information, in the upper righ t hand quadrant to decrease operator response time. 8 e e' The approximate effective visual field for detail is 50 cone about the focal line - of sight. At a 28-inch viewing distance, l~ the resulting field is a circle of 2.4 inches in diameter ongthe CRT face. Field size impacts label and numeric length in the format.and placement of re lated or unrelated groups of information on the screen. e Where it is impossible to provide sufficient ' open space between ~ - groups of information, it is recommended that boxes a nd lines be used to group the data into clearly defined areas on the display page..Although less e ffec tive than open space, a box arou nd a set of data tends to - focus the operator's attention and remove some of the distractions from adjacent data and information. 1 Every display page should have a header; every header should con-I l e l-tain the same set of information about the display, and the information should be positioned in the same general location on the display page. The header format should be established early j in system development, and it should be consistently used for all display pages on both the primary and the secondary sides of the plant. ,e Nomenclature should be standardized early in system development . and should - be consistently applied on all display pages. A standard ized list of abbreviations should be developed and i j rigorously applied. e Consistent coding techniques should be used for every. display i page. A symbol set should be selected and used throughout. One a color coding scheme should be used for every display page on both the primary and the secondary sides of the plant, a nd color should not be overused or misused just bacause it is an available coding technique. i - Lack of Standardization In reviewing - the advanced design direc tions being pursued by the various NSSS vendors, it is-apparent that future control rooms will not be any more standardized , y than present generation control boards. For example, ' console designs incorporating ' CRTs.' run [the gamut from sit-down to si t-s tand to stand-up operation. Similarly, color ~ ~ coding prac tices vary from vendor. to vendor. Some vendors. are using the traditional industry red-green color coding scheme for active passive designations - of ; the status of valves and breakers, as well as the status. of flow in intercon-necting piping.' One. vendor is t. sing. symbology, rather than color, to designate-n -active.versus passive devices and is reserving red for presenting alarm information - to - the - opera tor. One - vendor uses -cyan to ' designate dynamic, real-time. data;- 1-another ' uses auber': fora this. function. As discussed earlier, the information 1-46 4-o ?'*s i u- )t ,.W w gy g ,i,-.w.c w ,.p-yaq. ~ m.-- qg;.- +y -tg,- q e e-- .y. --&e-.*
accessing schemes vary from vendor to vendor. The interactive strategies and devices employed f or accessing inf ormation also vary widely. An obvious case can be made for s t a nda rd iz a t i on in terms of reduced training needs a nd the transfer of skills as ope ra t ors aove from one advanced control room to another. Iloweve r, perhaps an even more important conce rn is the lack of an empir-ical data base to favor one approach w rus another among the widely divergent i courses being pursued. IfYI! RID SYSTD1S While the re is an unmistakable trend toward computer-based control and display designs, t he re a re also indications that many plants will take a middle ground between the conven t iona l and advanced control rooms. We have chosen the term "hyb r id sy s tems" to re f er to combinations of conventional a nd a dva nc ed designs. This section will explore various possible hyb rid systems and some of the human f ac tors implications a ssocia ted with these control room con figurations. As noted
- earlier, conventional hard-wired instrumentation (meters, charts a parallel p re s ent a tion of informa-rec ord e rs, counters, a nd i nd ica t ors) provides tion in a fixed display mode.
The in forma t ion is continuously available to opera-t ars and all those who f requent the control room. An electronic display device, on the other hand, presents information serially to the operator in a variety of pres-entation mode s or formats. The information is available on reque st a nd can be incorporated on more than one display page providing a dynamic set of relationships among variables. Hybrid control room arrangements can build on the characteristics and st reng th s of both conventional and advanced electronic displays and hence have potential for providing the most e f f ec tive control-room alternative in the near f u t u re. Advanced Computer capabilities That May Be Added to Conventional Control Rooms Mo st existing conventional control rooms a l ready encompass a process compu ter and associated readou t s : either a CRT display or a printout device or both. The com-pu te rs generally supplement the hard-wi red boards by, for example, assisting with complex calculations or automatic logging of events. These capabilities could be extended in the following ways: e Disturbance Diagnosis. There is a serious problem with present board designs: when a maj or transient of disturbance occurs, the operator is overwhelmed by a large number of visual indications accompanied by successive auditory alerting signals, all of which 1-47 i
must be acknowledged and silenced. There is simply too much information displayed to be readily absorbed end integrated. The addition of advanced computer capability to existing control rooms may take the form of improved diagnostic techniques. Two levels of alarm handling are currently being developed for use in advanced CRT-based control rooms, and these capabilities, when available, could be integrated into existing control rooms. e Improved Plant Monitoring. Advanced computer capabilities can be used to s truc tu re the presentation of information in a way that assists an operator in monitoring the plant and anticipating anomalous conditions. Plant status information can be p resented alphanumerically in digital form or in analog form as bar graphs for ope ra tor surveillance. Key parameters can be p re s ented together on one display page rather than being physically dispers ed about the control room. For periodic, procedural reviews, information can be presented in a form that permits insnedia te reading without requiring the operator to wander about the control room. Thus, the flexibility of formatting and pre s-entation modes with electronic display devices may enable an operator to perform routine monitoring tasks more e f f ec tively. Mimic arrangements, which operators favor, can be readily incor-porated in CRT formats. e Improved Plant Control. Present control board designs sometimes separate controls and associated displays, requiring the operator to be in two places at the same time. If the control board allows f or the incorporation of CRT displays at disc rete spatial intervals, raquired display information could be called up in the vicinity of the :ontrol being actuated. This redundancy of 1 information would " shrink" the control room size and also aid multi-opera tor tasks such as startup. I Human Factors Concerns and Issues The development of hyb rid arrangements, both those involving modifications to existing plants and thone involving futu re plants, introduces some basic questions regarding the best integration of conventional and advanced control display capa-bili ty within one control room. How should ope ra tors divide their attention between advanced CRT displays and conventional boards? Should the advanced dis-plays and controls be integrated into the same console with conventional instrumen-tation, or should an auxiliary console be provided with the advanced capability? There is always the possibility of conflicting information from the conventional and ' advanced displays, pre senting the operator with the dilensna of deciding which displays to believe. j i The development. of a thorough operacional concept is the first task to undertake either when adding advanced computer capability to existing control rooms or when developing a hybrid control room from the outset. During normal operations, will an operator be primarily interfacing with the conventional display, the advanced 1-48 u
displays,. or both forms of display? Similarly, operational reqeirements associated with start-up, shutdown, and plant disturbances need to be de fined. Some control rooms are designed for one-man operation. With the addition of advanced capa-bility, manning requirements may correspondingly inc rease depending on the manner in which the advanced control and display features are integrated into an existing control room. One approach tak en in the oil re fining indu stry has considerable appeal from a human fac tors standpoint: to incorporate the advanced capability in a separate console and assign a more senior control room operator or supervisor to it while the control room operator continues to monitor the conventional displays as per normal p rac t ice s. In multi-unit plants, the center desk operator might assume responsibility for the advanced console. If the operational analysis indica tes that one ope ra tor can r,imultaneously handle the workload imposed by both the conventional and advanced coraponents of the con-trol room, then it might be best to integrate both capabilities i n to one maj or c on-trol boa rd. Integra tion would allow a func tiona l grouping of conventional and advanced displays with a ssocia ted controls. Othe rwise, the ope ra tor would be one conventional and the required to alternate his attention between two consoles: other advanced. While the potential bene fits for hyb rid systems are clear, there are many unre-solved human f ac tors issues in attempting to design the most effective hybrid capa-bility. Control room simulator-based research is required to resolve some of the pressing design and operational issues raised. DESIGN PRACTICES SURVEY To help implementa tion of human fac tors approaches in the power industry, some understanding is needed of the existing control board design process and con-straints. Accordingly, a survey was conduc ted, based on interviews with a sample of board designers. A 30-item structured interview form, requiring about two hours to administer, was developed with questions spanning a variety of design issues ranging f rom control room dimensions and control board configuration, to the design review p roce ss. The questions were designed to address the major human fac tors de ficiencies noted in the earlier review of control rooms (EPRI RP 501-1). The interview sample consisted of 20 designers, with half of them in a supervisory or lead engineer role. These designers we re selec ted from six firms, with eight employed by A-E. companies and the remaining 12 associated with NSSS firms. 'Ihe major findings and conclusions that emerged from this survey are presented below. .-49
Lack of Systematic Concern for Human Factors Human fac tors considera tims are not applied to the dete rmina tion of control room size, location, or con figu ra tion. No systematic functions and task analyses are conduc ted as prerequisites to establishing the manning concept, control display requi rement s, tra f fic pa t te rns, or an overall initial control room concept. Rather, the designer is faced with a set of " givens" he must acconsoodate, and which are, with the exception of advanced compu ter-ba s ed concepts, standard re ference control boards or the most recent proj ec t worked on. These precedents, likewise, not based on human f ac tors concerns, are so the same set of problems persist from generation to generation. In the course of the detailed design process, no individual or group is dedicated to concern for the ope rational aspects of the boards. Responsibility is di f fuse and assumed to be a consnon concern of all parties involved. The designers, whose e ff orts are of ten directed by " client preference" either directly, or through A-E project management acting as the client's agent, may lose any sense of responsi-bility for operational aspects of the design. After all, the client has to operate the board s, so why not leave all such decisions to the client? One designer expressed these sentiments as follows: "I have no pride of authorship in the lay-out of the board s. The client has to live with them. Nobody here cares that much. The PRC is only interested in knowing whether or not a certain function is covered on the boards - either in front or back, and is it separated. Besides, we wen't be here when the boards become operational." In short, the operator does not have a stead fast and dedicated representative at the design table or in the design review. Lack of an Integrated Human Factors Approach to Control Room Design Various systems designers are each responsible for a segment of the overall plant de sign. and each one impac ts the control room and control board design where the systems all come together for monitoring and control functions. However, there is lit t le cross-talk between the individuals. The facility design people establish the size and con figuration of the control room anr! do not consult with the control board designers. The designers of the reactor systems do not cross-check with the l turbine designers; there may be inadequate consnunication between the client's engi-neering organization ar.d the operations group; and the NSSS control board designer may never talk to the client directly but only through the A-E firm representing the clients. The board designer is given lists of disparate instrumentation . requi rements from a host of participants in the design process. There is no inter-mediate systems-integration func tion setting consnon groundrules for all subsystem 1-50 i
de si gne rs. Furthermore, in at least half o r' the cases, there is no full-scale mockup to serve as a design integ ration tool. In many military and space system developments, a human factors and industrial design team assumes the responsibility for the integration of control and display requi rement s, panel design prac tice s, and operational evaluations of candidate approaches. Lack of Human Factors Design Guidelines i The designers interviewed are severely limited both in possession of human factors Information and in access to human f ac tors spec ia lis t s. While scattered articles on such subjects as anthropometries are accumulated, none of the common human engi-neering re fe rences or standards used in the aerospace indu stry we re in evidence. Human fac tors guidelines tailored to the need s of the power industry are urgently requi red. However, for the present, designers should rely on existing guides: e M IL-ST&-1472 B, Human Engineering Design Criteria for Military Systemn, Equipment and Facilities, 1974. e Van Cott and Ki nkade, Human Engineering Guide to Equipment Design, 1972. McCormick, Human Factors Engineering, 1976. e Woodson and Conover, Human Engineering Guide for Equipment Designers, 1973. More importantly, utilities generally have no formal procedures for ensuring the adoption and implementation of human factors principles and methods in control room design. Such attention to human factors is a matter of contractual requirements in the development of military systems. The most repetitive phrase heard during the interviews was " client preference." If the client indicates a preference for human-engineered control rooms, and has the means to evaluate proposed designs, design organizations will follow suit as did all of the major aerospace firms when the military insisted on human-engineered weapon systems. 4 Overreliance on the Operator The utilities, in varying degrees, attempt to human-engineer control rooms by rely-ing on the operations department to either design the boards or revamp proposed re ference board s submitted by the contractors. While it is essential to consult the operators in the design and evaluation process, operators are not equipped by training or experience to design control rooms. The designer need s to tap the operator's experience and preference as an important input to design rather than turning over this responsibility to the operator. The design organization should acquaint the opera tors with the operational features of candidate control room i I 1-51 {
designs and use them in performance evaluation studies of the candidates. In the p re s ent survey, it wa s learned that the designer is generally far too remo te from the operational environmentl many have never set foot in an opera tional control room. Mockups, Simulators, and Demonstrations More extensive use should be made of mockups and simulators because, as noted above, they serve as important desi n integration aids. In addition, mockups pro-F vide an essential evaluation tool through which the utilities can review a partic-ular design for human f ac tors concerns before any metal is bent. Ilowever, mockups were used in only 40 to 50 percent of the projects covered by our sample. Simula-tion is even ra rer and only used in some instances of advanced systems develop-ment. On many aerospace developments the contractor is required to demonstrate the operability of the boards against contractual obligations set by the client. Mock-ups can later serve as valuable training aids, so the cost can be justified beyond design costs. Similarly, where new and untested advanced control room concepts are being procured, dynamic simulation is often required to provide the assurance that the man-machine interface will be effective and reliable. Lack of Feedback The designe rs get no formal feedback from the plants regarding the adequacy of their control board designs. They may hear informally of problems that surfaced during plant start-up. However, there are no formal procedu re s for accumulating user reaction to guide future design efforts. For one reason, th ree or more years may elapse between the times that the design work is completed and the board s b ecome operational. Typically, a sepa ra te field service group, and not the de signe r, oversees the console through assembly, test, and start-up. By the time feedback might be available, the designer has long since moved to another project, is employed by another company, or has retired. + CONCLUSIONS AND FUTURE STUDY NEEDs This study has examined the applicability of human fac tors engineering methods in resolving problems noted in an earlier study of nuclear power plant control room 1 designs. In developing control board concepts based on human factor principles and in exposing these candida tes to the scrutiny of operational and design personnel, it became evident that the human fac tors principles and methods developed in the military-aerospace context are applicable and relevant to the needs and concerns of the power indu st ry. While board designers might que st ion the development cost or schedule inpact of some reconsnenda tions, overall the re was good acceptance of 1-52
underlying human fac tors principles. Operational personnel were even quicker to perce ive and endorse the proposed design features aimed at improved ope ra tor-control board interfaces. In comparing human fac tors appreaches with current board design practices, certain salient differences emerge. First, human f ac tors specialists place greater empha-systematic analyses of the man-machine inter faces to determine control and sis on p re requisi tes to design. Also, these spe-display requirements and groupings as cialists have evolved a set of rules or guidelines based on laboratory experimenta-tion and field evaluations that are consistently applied in the layout of control panels. Additionally, a great deal of emphasis is placed on verification of design concepts by means of mockups and simulators using representative test subjects. The general acceptance for human fac tors impact on control board design observed in this study, coupled with a highly responsive reaction to the findings of the ante-cedent study (EPRI RP501-1), impels a consideration of steps that should be teken to ensu re a more sy stematic concern for human factors in fu ture design efforts. First, and foremos t, there is an urgent need for a human fac tors design guide tailored to the needs of the power industry. A corollary need exists for a human factors standard to be invoked for control room procurement purposes. The survey of current control board design practices revealed that design organizations asso-ciated with A-E and NSSS firms are extremely responsive to " client pre ference" in the development of new control room designs. However, the utilities presently pro-vide little or no formal guidance in ensuring that human factors considerations are taken into account by the designer. With the emergence of human f ac tors design guides and standards, it can be anticipated that more of the attention of the 3,000 or so human fac ters specialists in this country would be focussed on human f ac tors problems in the powe r indu stry. At pre sent, less than a handful of such special-ists, with bons fide c redentials, are participating direct ly in solving power industry problems. Beyond the high priority measures described above, the following research avenues ) have been identified as leading to a significant expansion of the human factors data base to aid control roam designers acd utility decision-makers: e The p esent study has identified a variety of measures for up-1 grad ing existing operational control rooms both to improve the operator-control board interface and to minimize the potential for human error. The feasibility and value of such mea sure s 1-53 =.
should be examined in greater depth in the operational eviron-ment. Several nuclear power plant control rooms, where a corre-spond ing training simulator exists, should be reviewed in detail with the objective of modifying the boards systematically without interruption of power production. Human fac tors reconsnenda tions for up-g rading each control room should be formulated and dis-cussed with plant operations, engineering, and management person-net. These modifications should first be attempted and evaluated in the contro l room simulators. Sub sequent ly, specific backfit reconsnenda ti ons should be o ffered to each plant, and general reconenenda tions should be offered to plants not participating in this study. A review of existing control rooms has revealed a number of major e de ficiencies with p resent annuncia tor wa rning systems. Bis study has de fined a number of possible alternatives to existing designs. De candidate audio-visual annunciator warning approaches developed should be evaluated experimentally to ensure that they offer substantial operational bene fi ts over existing operational approaches. De candida te s that prove most effective from the human factors standpoint should be examined in terms of design complexity and cost fac tors. e Advanced CRT formatting and color usage approaches being devel-oped vary widely from vendor to vendor. Research is needed to determine the relative e ffec tivene ss of competing advanced con-trol and display concepts and to provide human factors guidelines for future developments. Much might also be learned from a human f ac tors review of foreign approaches to advanced control room design. Significant advances are being made in Japan, Sweden, 1 Germany, the USSR, Great Britain, Denmark, and Norway. %e util-ity industry might avoid needless duplication of effort and learn from the experiences of other countries. For example, the British ran into serious prnblems in the advanced control room area ; the operators experienced severe information re trieval problems. e Each of the major NSSS vendors is focussing on advanced computer-based control room designs as an option to the present generation hard-wired control ro)ms. A trend towards advanced systems exists, even though the operational benefits of the advanced sys-te ms have not been demonstra ted with hard evidence within the utility industry. When the first advanced control room simulator becomes available in 1980, the opportunity will be at hand for a detailed human f ac tors review of initial operational experiences with advanced systems. Consideration should also be given to extending EPRI RP 769 (Performance Measurement System For Train-ing Simulators) to an advanced control-room simulator. The per-formance measurement methods being developed by EPRI RP 769 could provide comparative human performance data on conventional versus advanced systems. e he ana ly tic e fforts conducted in the pre sent study revealed instances in which a particular display might profitably be added to the cu rrent reper tob of information provided to operntors, or in which an interlock might have been included in the design to preclude the possibility of operator error in conduc ting a specific task. These and other control board design enhancement i 1-54 1 i
possibilities should be pursued further in a design team setting so that appropriate engineering trade-offs can be conducted to establish c os t-b ene fit f ac tors in evaluating individual human f ac tors proposals. e The conventional hard-wired panels developed in the pre sent study, and based on human f ac tors methods and principles, should be compared experimentally with their current operational counterparts within existing control room simula tors and by recruiting re pre sentative operators as test sub jec ts. Dynamic simulation would have to be supplied to the existing mockups of feedwa ter, reac tor, and turbine generator control panels. Opera-tor performance measures associated with existing and proposed designs should be obtained under both normal and degraded opera-tional conditions, such as excessive operator fa tigue or the first graveyard shif t after four days off work. e A review of control-display coding p ractices in pres ent day nuclear power plants indicate s that available coding dimensions are applied inconsistently or are underused. Color coding prac-tices, such as the green board concept, should be compared exper-imentally with conventional display c odes in terms of operator per formance mea sure s. Uniquely shape-coded controls should be developed to minimize the potential for inadvertent control activation. The complexity ~ and feasibility of adapting coding techniques developed in space and military contexts should be assessed in design engineering terms. e It was indicated in this study that many utilities will opt for hybrid control rooms or some middle ground between advanced con-trol rooms and the dedicated control-display conventional control rooms. Hyb rid concepts ra ise significant human fac tors issues regarding the division of operational. attention between advanced and conventional components of the hybrid control room. Research is needed to evaluate alternative ways of integrating advanced and conventional components of hybrid control rooms, such as a separate console for advanced displays versus the physical inte-gration of CRTs within conventional control boards. As prototype advseced system elements are developed, alternative methods for interating their capabilities in a conventional control room can be asLessed using existing control-room simulators. -s 1-55 L .}}