Procedure Following Strategy

This page describes Figure 8 of the ADS-IDAC manual: the Procedure Following Process flowchart. The procedure following process is activated when the Decision Maker selects the "Follow Written Procedure" strategy. A similar process is also applied when any operator executes a memorized mental procedure.

Figure 8 from original manual: "Procedure Following Process"

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Overview

Procedure following is a structured problem-solving strategy. Step sequencing is controlled by two separate tracking systems:

Tracking System	Scope	Maintained By
Procedure status queue	Tracks which procedure steps are active, paused, completed, or interrupted	Each operator's memory (per operator)
Detailed procedure step check-off list	Executes each individual step element (substep)	Shared — one copy for the entire crew

Exclusive Step Access

Only one operator may access the detailed procedure step check-off list at a time. If two operators attempt to perform the same step simultaneously, the second operator is blocked until the first completes the step and the check-off list is reset. This prevents crew members from interfering with each other's step sequencing.

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Flowchart

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Procedure and Substep Status Categories

Procedure Status (in Operator Memory Queue)

Status	Identifier	Description
None	VNONE	Procedure step has not been performed
Active	VACTIVE	Procedure step is in progress
Paused	VPAUSE	Temporarily suspended to permit execution of a higher-priority step
Interrupted	VINTERRUPT	Permanently suspended
Completed	VDONE	Procedure step has been completed

Completion Does Not Imply Success

A VDONE status indicates the step was executed, not that its objectives were achieved. Equipment failures, information filtering or biasing, or step-skipping could result in the failure of the step to accomplish its stated objectives.

Substep Status (in Detailed Check-off List)

Status	Identifier	Description
None	VNONE	Substep has not been performed
Active	VACTIVE	Substep is in progress
Completed	VSUCCEED	Substep has been completed

Each procedure step consists of one or more substep triples: an action, an expectation check, and a contingency (non-response) action.

Substep Expectation Status

Status	Identifier	Description
None	VNONE	Expectations not yet evaluated
Active	VACTIVE	Expectation verification in progress (may require multiple checks due to Boolean operators)
Succeed	VSUCCEED	Expectations evaluated and met
Failure	VFAILURE	Expectations evaluated and not met

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Block Descriptions

Block 1 — Start Follow Procedure Strategy

Activated when the Decision Maker selects the "Follow Written Procedure" strategy, or when any operator begins executing a memorized mental procedure.

Block 2 — Active Procedure in Memory?

The operator's procedure queue is searched for a step in VACTIVE status. If multiple active steps exist, the last active step in the queue is selected (last-in, first-out).

Block 3 — Paused Procedure in Memory?

If no active step is found, the queue is searched for steps in VPAUSE status. If multiple paused steps exist, the last paused step is selected (last-in, first-out).

Block 4 — Has Entry Procedure Been Executed?

For plants using symptom-based procedures, operators are directed to a single emergency procedure entry point (e.g., the E-0 Reactor Trip procedure for a Westinghouse plant). ADS-IDAC assumes this entry point is the first procedure step listed in the Procedures.txt input file.

If the operator has not yet performed the entry procedure step (VNONE status), the entry step is added to the memorized queue.

Block 5 — End

If the queue contains no active or paused procedures and the entry procedure step has already been executed, procedure following is terminated. This does not preclude reactivation if a new step is later added to the queue.

Block 6 — Activate Procedure

The procedure step status is set to VACTIVE in the operator's queue list (if not already active).

Block 7 — Is There an Active Substep Available?

The detailed procedure step check-off list is searched for either:

• A substep that is currently in progress (VACTIVE), or
• A substep that has not yet been performed (VNONE)

If all substeps have been completed (VSUCCEED), the operator proceeds to get the next procedure step name.

Block 8 — Has Substep Action Been Completed?

Substep actions consist of a single interaction with the reactor plant control panel (e.g., opening a valve, starting a pump, actuating a control switch).

• If the substep has not been performed (VNONE), the action is executed and the substep status is set to VACTIVE.
• If the substep status is already VACTIVE, the action has been completed and the process moves to expectation evaluation.

Block 15 — Check for Timing or Control Value Branches

Prior to performing a substep action, a check is made for any timing or control value branch options specified for the action. These are defined in:

• ProcedureActionTimeBranches.txt
• ProcedureControlValueBranches.txt

Block 16 — Skip Substep Action?

Prior to performing any substep action, the probability of skipping the step is dynamically calculated. If the skip probability exceeds the threshold in ActionTaker.txt or DecisionMaker.txt, two branches are generated:

1. One branch where the action is performed
2. One branch where the entire substep is skipped

Block 17 — Mark Action as Completed (Skipped)

If the substep action is to be skipped, the action is not performed and the entire substep is marked as completed (VSUCCEED). The operator will not evaluate expectations nor perform the contingency action for this substep.

Block 18 — Execute Substep Action

If the substep action is to be executed (not skipped), the action is performed. After execution, the process evaluates whether the action's expectations have been checked.

Block 9 — Have Action Expectations Been Evaluated?

If the substep action has been performed (status VACTIVE), the expectation status is verified.

Expectations will be evaluated if their status is VNONE (not yet evaluated) or VACTIVE (evaluation in progress). A status of VSUCCEED or VFAILURE indicates that expectations have been fully evaluated.

If the substep has no expectations, the substep is marked as completed directly.

Block 19 — Evaluate Expectations

The operator obtains the necessary data from the reactor plant to determine the status of the substep expectations. Expectations can include parameter values, alarms, mental beliefs, or component status verifications.

Because expectations can consist of multiple elements combined with Boolean operators (AND/OR), it may be necessary for the operator to verify more than one element to completely assess the expectation status.

Block 10 — Are Expectations Met?

• Yes (VSUCCEED): The substep is marked as completed.
• No (VFAILURE): The contingency (non-response) action branch is taken.

Block 20 — Check for Timing or Control Value Branches (Non-Response Action)

Prior to performing the substep contingency action (the non-response action), a check is made for any timing or control value branch options. These are also defined in ProcedureActionTimeBranches.txt and ProcedureControlValueBranches.txt.

Block 21 — Skip Non-Response Action?

Prior to performing the contingency action, the probability of skipping it is dynamically calculated. If the skip probability exceeds the threshold in ActionTaker.txt or DecisionMaker.txt, two branches are generated:

1. One branch where the contingency action is performed
2. One branch where the contingency action is skipped

Block 22 — Mark Non-Response Action as Complete (Skipped)

If the contingency action is to be skipped, both the contingency action and the entire substep are marked as completed (VSUCCEED).

Block 23 — Execute Non-Response Action

If the contingency action is to be executed (not skipped), the action is performed.

Block 24 — Mark Substep as Completed

At this point, all substep activities have been completed:

• Substep action has been performed (or skipped)
• Expectations have been evaluated (if applicable)
• Contingency action has been performed (or skipped)

The substep status is updated to VSUCCEED.

Block 11 — Get Next Procedure Step Name

When all substeps are complete, the operator:

1. Updates the current procedure step status to VDONE in the memory queue
2. Resets the detailed procedure step check-off list
3. Retrieves the next procedure step name

The next step is typically the next sequential step in the procedure (e.g., E-0 Step 1 references E-0 Step 2).

Block 12 — Is Next Procedure Step Valid?

A verification check ensures the next step is listed in Procedures.txt and that an associated ZProcedure_<procedure_name>_<step_name>.txt input file exists. If the step is invalid, an error message is generated in error messages.txt.

Block 13 — Activate Next Procedure in Memory

If the reference to the next procedure step is valid, the next step is added to the operator's procedure queue list with VACTIVE status.

Block 14 — End

If the next procedure step is invalid or identified as NONE, the procedure following process terminates. This does not preclude reactivation if a new step is later added to the operator's procedure queue list.

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Procedure Step Structure

Each procedure step defined in a ZProcedure_*.txt file consists of:

Step
├── Substep 1
│   ├── Action (single control panel interaction)
│   ├── Expectation (parameter/alarm/component verification; optional)
│   └── Non-response action (contingency if expectation fails; optional)
├── Substep 2
│   └── ...
└── Reference to next step name (or NONE)

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Procedure Transfers

When the active procedure step is completed and the next step pointer references a step in a different procedure (e.g., transitioning from E-0 to E-1), the procedure transfer is handled through the step name reference mechanism in the ZProcedure_*.txt file. If the referenced step name is valid and present in Procedures.txt, the operator transitions to the new procedure seamlessly through Block 13 (Activate Next Procedure in Memory).