Decision-Making Process: Decision Maker (ODM)

This page describes Figure 4 of the ADS-IDAC manual: the Decision-Making Process for the Decision Maker (ODM). The decision-making process immediately follows information processing. The ODM evaluates the current goal and strategy, selects a problem-solving strategy, and issues ordered activities to the Action Taker via the blackboard.

Figure 4 from original manual: "Decision-Making Process (Decision Maker)"

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Key Characteristics of the Decision Maker

The Decision Maker (ODM) is the cognitive lead of the control room crew model. Key distinctions from the Action Taker (OAT):

• The ODM performs independent goal selection (see Goal Selection Process)
• The ODM is the only operator capable of the Knowledge-Based Reasoning strategy
• The ODM issues orders to the OAT via the blackboard; the OAT executes the physical control manipulations
• The ODM monitors OAT compliance by checking whether ordered activities have been completed (via blackboard confirmation packets)
• Before performing further decision-making activities, the ODM checks whether the OAT is busy to prevent overloading the Action Taker

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Flowchart

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Block Descriptions

Block 1 — Start Decision-Making Process

The decision-making process immediately follows information processing. During this process, the operator:

1. Evaluates the current goal and strategy
2. Identifies actions in accordance with the selected problem-solving strategy
3. Implements memorized mental procedures

Block 2 — Abnormal Signal Detected?

An abnormal signal indicates a condition incompatible with continued power operation. Either of two conditions triggers this detection:

1. Activation of the Reactor_Tripped mental belief (see KB_ODM_HardWired_Diagnosis.txt)
2. The fuzzy logic diagnostic engine accident relationship value exceeding a preset threshold (see Decision_Maker.txt and KB_OAT_Event_Matrix.txt)

Detection of an abnormal condition shifts the crew into accident response mode.

Block 3 — Interrupt Low Priority Mental Procedures

Certain memorized mental procedures incompatible with a post-trip condition are permanently suspended once an abnormal signal is detected. For example, a procedure to reduce turbine load is no longer appropriate after a reactor trip.

One-Time Interruption

The interruption of low-priority mental procedures can occur only once per simulation. Once an abnormal signal is detected, newly identified low-priority mental procedures can still be added to the operator queue and implemented.

The low-priority procedure threshold is specified in Decision_Maker.txt. Priority levels are defined in KB_ODM_HardWired_Diagnosis.txt (lower priority values indicate higher priority procedures).

Block 4 — Pause Activity Flag Active?

Each operator has two separate Boolean pause activity flags:

Pause Flag	Suspends
Mental procedure flag	Activities associated with mental procedure execution
General activity flag	All other operator activities

If any pause flag is active (true), the operator is already engaged in an ongoing activity and further decision-making activities are bypassed until the flag clears.

Block 5 — Mental Procedure in Queue?

The mental procedure queue is checked for any procedures awaiting execution. A check is also made to ensure the Action Taker is not simultaneously performing the same mental procedure step (two operators cannot perform the same step simultaneously).

If a waiting mental procedure exists (and is not being performed by a different operator), execution takes priority over goal and strategy selection.

Block 6 — Perform Mental Procedure Step

The Decision Maker executes the mental procedure actions.

Block 7 — New Branch Generated?

Some mental procedure actions require interaction with the reactor plant or crew coordination. These tasks require time to complete, necessitating a branch to temporarily suspend decision-making.

Block 8 — Activate Pause Activity Flag (Mental Procedure)

If a new branch is generated, the pause activity flag is set to true. Further decision-making is suspended until the flag is reset during later information processing.

Block 9 — Evaluate Goal

The appropriateness of the current high-level goal is evaluated. See the Goal Selection Process (Decision Maker) flowchart.

Block 10 — New Goal Selected?

If the goal evaluation indicates the current goal must change, further decision-making is suspended and the goal is updated.

Block 11 — Activate Pause Activity Flag (Goal Update)

If the goal is to be updated, a new goal branch is generated and the pause flag is activated. When the new goal is perceived during subsequent information processing, the pause flag is cleared and decision-making resumes.

Block 12 — Evaluate Strategy

The appropriateness of the current problem-solving strategy is evaluated. See the Strategy Selection Process (Decision Maker) flowchart.

Block 13 — New Strategy Selected?

If the strategy evaluation indicates the strategy must change, further decision-making is suspended and the strategy is updated.

Block 14 — Activate Pause Activity Flag (Strategy Update)

If the strategy is to be updated, a new strategy branch is generated and the pause flag is activated. When the new strategy is perceived during subsequent information processing, the pause flag is cleared and decision-making resumes.

Block 15 — Action Taker Busy?

Before the ODM can execute the results of further decision-making activities, it is likely that orders will need to be issued to the OAT. To prevent overloading the Action Taker, a check is made:

The Action Taker is considered busy if:

• The OAT has a queued mental procedure waiting to be executed, or
• Any of the OAT's pause activity flags are active (indicating another activity is already in progress)

If the OAT is busy, further ODM decision-making activities are bypassed for this time step.

Block 16 — Current Strategy?

Depending on the Decision Maker's current problem-solving strategy, three possible execution paths exist:

Strategy	Next Step
Follow Written Procedure	Block 17
Knowledge-Based Reasoning	Block 19
Wait & Monitor	Skip to Block 22 (no further action)

Block 17 — Follow Written Procedure Strategy

The Decision Maker implements the Follow Written Procedure strategy. See the Procedure Following flowchart for details.

During this strategy, the ODM reads procedure steps, issues ordered actions to the OAT via the blackboard, and monitors OAT compliance through blackboard confirmation packets.

Block 18 — New Branch Generated? (Procedure Following)

Certain procedure-following actions require either:

1. Interaction with another operator or the reactor plant control panel, or
2. A time delay

In these cases, a new branch is generated to temporarily suspend decision-making until the action is complete.

Block 19 — Knowledge-Based Reasoning Strategy

The Decision Maker implements the Knowledge-Based Reasoning strategy. See the Knowledge-Based Action Execution flowchart for details.

During this strategy, the ODM uses a fuzzy logic diagnostic engine and an imbalance diagnosis framework to identify functional degradations in the reactor plant and select appropriate corrective actions from the KB_ODM_Diagnosis_Actions.txt knowledge base. These corrective actions are then issued to the OAT as ordered activities via the blackboard.

Block 20 — New Branch Generated? (Knowledge-Based Reasoning)

Certain knowledge-based reasoning actions require either:

1. Interaction with another operator or the reactor plant control panel, or
2. A time delay

In these cases, a new branch is generated to temporarily suspend decision-making until the action is complete.

Block 21 — Activate Pause Activity Flag (Strategy Execution)

When a new branch is generated during either strategy execution path, the pause activity flag is activated to temporarily suspend further decision-making until the associated activity is completed.

Block 22 — End Decision-Making Process

The Decision Maker's decision-making process is complete for this time step.

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ODM Strategy Summary

Strategy	Activation Condition	Key Input Files
Wait & Monitor	Goal is Normal Operation or Monitoring	—
Knowledge-Based Reasoning	Goal is Troubleshooting	KB_ODM_Diagnosis_Actions.txt, KB_ODM_Event_Matrix.txt, KB_ODM_System_Decomposition.txt
Follow Written Procedure	Goal is Maintain Global Safety Margin (or procedure queued)	Procedures.txt, ZProcedure_*.txt