Empirical investigation of workloads of operators in advanced control rooms

Figures & data

Table 1. Operator's activities of the COCOA framework.

Dimension	Activity	Description
Cognitive activity	COMPARE	Comparing two or more entities of system states.
	DIAGNOSE	Recognizing or determining the cause of the system states by signals or parameters.
	EVALUATE	Checking a system state with consideration of other system parameters or states.
	EXECUTE	Performing a single prescribed action (e.g. open, close, turn on, etc.).
	MAINTAIN	Sustaining a specific system state by executing or regulating systems.
	MONITOR	Continuously observing the system states or parameter.
	RECORD	Writing down or logging the system states or events.
	REGULATE	Changing the quantity, speed, or direction of the system parameters or states.
	VERIFY	Checking an entity of system states.
	SCAN	Briefly reviewing specific system states by displays or other information.
	PLAN	Formulating a path to achieve specific goals.
	IDENTIFY	Recognizing the overall state of a specific system.
Communicative activity	COMMAND	Ordering an operator to execute or regulate a system or component.
	COMMAND-ACK	Informing whether a listener understood a command.
	INQUIRY	Asking about system states or parameters.
	REPLY	Answering a question.
Operative activity	SWITCH---SCR	Altering a display screen to read or operate specific parameters or states.
	OPEN---CTRLPNL	Opening a control panel to operate a specific system.
	CLOSE---CTRLPNL	Closing a control panel that has been opened.
	CLICK---EXECUTE	Pushing a button to operate a single entity (e.g. opening a valve).
	CLICK---REGU---UPDN	Pushing a direction button to regulate a system parameter or state (ex. opening a valve).
	CLICK---REGU---FASTUPDN	Pushing a double-direction button to regulate a system parameter or state (ex. opening a valve).
	CLICK---ENABLED	Pushing a button to enable a control panel to be usable.
	CLICK---MANNUAL	Pushing a button to manually operate a single entity.
	CONF---STEP	Clicking a button confirming that all instructions of a step have been completed.
	CONF---SUBSTEP	Clicking a button confirming that an instruction of a step has been completed.
	ACK---ALARM	Checking and silencing a notifying alarm.
	CONF---CHANN	Pushing a button to verify the channel of an entity to be operated.

Table 2. An example of discourses and behaviors of operators in APR 1400.

Procedure instruction	SS	BO (RO)
LOCA step # 4.1) Is the pressure of the pressurizer less than 127.3 kg/cm^2A?	‘RO, is the pressure of the pressurizer lower than 127.3 kg/cm^2A?’	‘Yes’
		<Checks the pressure> ‘Yes, the pressure is lower than 127.3 kg/cm^2.’
	‘Yes, I confirmed’ <Clicks an instruction confirmation button of CBP>
LOCA step # 4.2) Confirm that the safety injection actuation signal (SIAS) was initiated.	‘RO, was the SIAS initiated?’	‘Yes’
		<Checks the SIAS> ‘Yes, the SIAS was initiated.’
	‘Yes, I confirmed’ <Clicks an instruction confirmation button of CBP>

Table 3. F ratios of ANOVA conducted to compare activity frequencies between operator roles.

	F ratio
Dimension	LOCA	SGTR
Cognitive	414.5^***	368.9^***
Communicative	87.58^***	401.2^***
Operative	3.463	6.009^*

^***p < 0.001; ^*p < 0.05.

Figure 1. COCOA activity frequency during LOCA scenario.

Figure 2. COCOA activity frequency during SGTR scenario.

Table 4. Standard deviations of activities for each activity type and operator role.

		SS	RO	TO	EO
LOCA	Cognitive	2.9	6.8	1.2	2.6
	Communicative	8.4	5.7	2.4	0.8
	Operative	9.9	16.0	12.3	47.5
SGTR	Cognitive	6.6	2.6	1.4	0.5
	Communicative	1.7	0.8	3.6	0.8
	Operative	9.9	39.0	14.7	24.2