Procedures
General Description
ADS-IDAC includes the capability to represent both the structure and content of many types of plant procedures. Procedure step execution follows the standard format of action execution followed by expectation verification. If the action expectations are not met, a mitigative action can be performed.
Four general types of procedural actions can be executed:
- Changing the component operating mode (e.g., automatic vs. manual mode)
- Setting a specific control value for a component (e.g., throttling control valve to 50% open)
- Incrementing the control setting of a component (e.g., throttling open a control valve by an additional 10%)
- Setting a control value based on a perceived parameter (e.g., setting the steam dump target pressure equal to the perceived main steam header pressure)
Generally, a written procedure is continued until the procedure is completed. However, the procedure flow may be interrupted by procedure transfers, activation of an instinctive response action, or abandonment of the "Follow Written Procedure" strategy. Two types of procedure transfers can be modeled: a permanent procedure transfer and a temporary transfer to an auxiliary procedure followed by resumption of the initial procedure.
Procedure Types
ADS-IDAC supports six procedure type categories. Each procedure type is assigned a skip multiplier in Procedures.txt to reflect operator adherence tendencies.
| Prefix | Procedure Type | Code |
|---|---|---|
| (none required) | Normal Operating Procedure (NOP) | VNOP = 3151 |
| (none required) | Abnormal Operating Procedure (AOP) | VAOP = 3152 |
E_ (recommended) | Emergency Operating Procedure (EOP) | VEOP = 3153 |
FRG_ (reserved) | Functional Recovery Guideline (FRG) | VFRG = 3154 |
ECA_ (recommended) | Emergency Contingency Action (ECA) | VECA = 3155 |
MPBG_ (reserved) | Mental (Memorized/Instinctive) Procedure | VMENTAL_PROCEDURE = 3156 |
INFO
The prefixes FRG_ and MPBG_ are reserved and must be used for functional recovery guidelines and mental procedures respectively, as these types require special handling by ADS-IDAC. The prefixes ECA_, E_, and ES_ are recommended but not required.
Mental procedures are memorized skill-based actions carried out without reference to written procedures. They are identified by the MPBG_ prefix on the procedure name.
Branching Types in Procedures
Four types of event sequence branches can be generated during procedure execution:
Mental procedure activation time branches — model variations in the time delay between activation of a mental belief and initiation of the associated memorized mental procedure. Configured in
MentalProcedureActivationTimeBranches.txt.Action execution time branches — generate multiple event sequence branches to model crew-to-crew variability in the time taken to perform procedure actions. Configured in
ProcedureActionTimeBranches.txt.Action control value branches — model variations in control inputs such as control valve positioning and target setpoint settings. Configured in
ProcedureControlValueBranches.txt.Step skipping branches — model omissions of procedure actions based on the relevance of the step to the operator's situational assessment. The step skipping model is described in
Procedures.txt.
Procedure Input Files
| File | Description |
|---|---|
MentalProcedureActivationTimeBranches.txt | Defines Weibull-partitioned timing branches for mental/instinctive procedure activation |
ProcedureActionTimeBranches.txt | Defines Weibull-partitioned timing branches for individual procedure step action execution |
ProcedureControlValueBranches.txt | Defines discrete branches for operator-selected quantitative control values |
Procedures.txt | Master procedure index; specifies global step-transfer times and all step skipping multipliers |
ZProcedure_{procedure}_{step}.txt | Individual procedure step files defining actions, expectations, and non-response contingency actions (one file per step) |
How a Branch Alternative Executes
When the branching rules produce several alternatives at a procedure step, the running sequence continues with the first alternative and the engine opens one child sequence for each of the others. A child sequence restarts from the plant and crew state saved at the branch point and then receives the content of its own alternative, so it behaves differently from the branch point onward:
| Rule file | What the child sequence receives |
|---|---|
ProcedureControlValueBranches.txt | The step's action with that alternative's control value, limited to the control's fully closed and fully open values |
ProcedureActionTimeBranches.txt | The step's action at that alternative's time |
MentalProcedureActivationTimeBranches.txt | The mental procedure activated at that alternative's time |
A step's skip alternative is combined with these. With K time strata, each control value alternative has the probability control_probability x (1 - skip_probability) / K.
A sequence whose probability falls below Truncation_probability in ZCtrlPar.txt ends with consequence code 2 and is kept as an end state. An alternative below the branch floor, when a floor is set, is not opened at all; its probability is added to the first alternative.