KB_OAT_System_Decomposition.txt

Purpose

The KB_OAT_System_Decomposition.txt input file provides a functional decomposition of reactor plant systems and components. It maps every control panel indicator, control, and alarm to the high-level plant functions that item supports. This functional map serves as the operator's mental model of the plant, linking components within a shared functional framework.

The system decomposition supports two main ADS-IDAC features:

1. Procedure step skipping — actions associated with items relevant to the current plant state assessment are less likely to be skipped; actions associated with non-relevant items are more likely to be skipped.
2. Scan queue management — the priority of relevant scan queue items remains high and those items are more likely to be retained in the monitoring list.

Relevance is determined by the diagnostic score for the functional imbalance(s) associated with a component. If an operator has diagnosed a specific imbalance, items associated with that imbalance receive a high relevance score (0.0–1.0).

Functional Categorization Scheme

ADS-IDAC uses a flow-based categorization:

• The reactor plant is viewed as a collection of mass, energy, and momentum flow paths, each containing sources and sinks.
• Energy flow imbalances are indicated by changes in temperature (subcooled single-phase) or pressure (saturated two-phase).
• Mass flow imbalances are indicated by net inventory changes (e.g., tank or vessel levels).
• Momentum imbalances are indicated by changes in flow rates.

Plant system groups define the flow path boundaries. Boundaries should be made as broad as possible to maximize component linkage, while constraining the system groups to maintain diagnostic clarity.

Recommended PWR System Groups (Table 5)

System Group	Flow Paths Modeled
Reactor Coolant System	Energy, Mass, Momentum
Pressurizer	Energy, Mass
Steam Generator A	Energy, Mass
Steam Generator B	Energy, Mass
Steam Generator C (if applicable)	Energy, Mass
Secondary (Turbine, Main Steam, Main Feed, Condenser)	Energy, Mass
Containment	Energy

Notes from Table 5:

• Each steam generator is treated as a separate system group.
• The secondary system group encompasses the turbine, main steam, main feed, and condenser systems.

Input File Format

"text_description_of_functional_decomposition"
Number_of_Functional_Items   number_of_functions
function_name_1              function_code_1
.
function_name_n              function_code_n

Control_Panel_Decomposition
item_name_1
item_function_1 .... item_function_j   999
.
item_name_m
item_function_1 .... item_function_j   999

Input Description

Parameter	Type	Description	Example Value
text_description_of_functional_decomposition	String	Free-text description of the functional decomposition, enclosed in double quotes. Quotation marks may not appear within the text. Supply empty quotes " " if no description is provided.	"Functional Decomposition: ..."
number_of_functions	Integer	Number of function entries. Range: > 0.	11
function_name	String	Unique descriptive name for each function. Should match an imbalance event in KB_OAT_Event_Matrix.txt. The reserved name Not_Applicable assigns a relevance factor of 1.0 to any item using it.	Mass_Imbalance_PZR_Low
function_code	Integer	Unique integer code for each function name. No two function names should share the same code. Recommend a structured multi-digit scheme.	121
item_name	String	Name of a control panel control, indicator, component, or alarm. Every item in ControlPanel.txt must have a functional description entry.	PZR_Level
item_function	Integer	One or more function codes assigned to the item. Multiple codes may be listed per item. Items with no codes are assigned a relevance score of 0.0. Items assigned the Not_Applicable code receive a relevance factor of 1.0.	111 121 211

Item Entry Termination

Each item_name data entry line must be terminated with the integer code 999. This signals ADS-IDAC that the list of function codes for that item is complete. A 999 terminator is required even if no function codes are assigned to the item.

Three-Digit Function Code Scheme

A recommended three-digit integer coding framework uses each digit position for a defined purpose:

Function Type (First Digit)
  1 - Mass Imbalance
  2 - Energy Imbalance
  3 - Momentum Imbalance

System Type (Second Digit)
  1 - Reactor Coolant System
  2 - Pressurizer
  3 - Steam Generator A
  4 - Steam Generator B
  5 - Steam Generator C
  6 - Secondary System (Turbine, Condenser)
  8 - Containment

Imbalance Trend (Third Digit)
  1 - Decrease
  2 - Increase

Special Codes
  900 - Not Applicable

Example interpretation: code 241 = decreasing energy trend in Steam Generator B.

For a complete three-function, eight-system-group, two-trend decomposition, the full set requires 3 × 8 × 2 = 48 separate functional entries.

Sample Input

"Functional Decomposition:
Function Type (First Digit)
1 - Mass Imbalance
2 - Energy Imbalance
3 - Momentum Imbalance
System Type (Second Digit)
1 - Reactor Coolant System
2 - Pressurizer
3 - Steam Generator A
4 - Steam Generator B
5 - Steam Generator C
6 - Secondary System (Turbine, Condenser)
8 - Containment
Imbalance Trend (Third Digit)
1 - Decrease
2 - Increase
Special Codes
900 - Not Applicable"
Number_of_Functional_Items
11
Mass_Imbalance_RCS_Low
111
Mass_Imbalance_PZR_Low
121
Mass_Imbalance_SG_A_Low
131
Mass_Imbalance_SG_B_Low
141
Mass_Imbalance_SG_C_Low
151
Energy_Imbalance_RCS_Low
211
Energy_Imbalance_PZR_Low
221
Energy_Imbalance_SG_A_Low
231
Energy_Imbalance_SG_B_Low
241
Energy_Imbalance_SG_C_Low
251
Not_Applicable
900
Control_Panel_Decomposition
Time
900 999
Watchdog_Timer
900 999
PZR_Level
111 121 999
PZR_Level_Setpoint
111 121 999
ECCS_Flow
111 121 211 999

Sample Explanation

The sample defines 11 functional items using three-digit codes. The text description field serves as a plain-language "roadmap" between the integer codes and their meaning.

The special function Not_Applicable (code 900) is assigned to Time and Watchdog_Timer — executive control items that should always have a relevance factor of 1.0.

ECCS_Flow is associated with three functions:

• 111 — low mass in the reactor coolant system
• 121 — low mass in the pressurizer
• 211 — low energy in the reactor coolant system

If the operator diagnoses a low-mass pressurizer condition, ECCS_Flow receives a high relevance score. As a result, actions involving ECCS_Flow are less likely to be skipped, and ECCS_Flow is more likely to be retained in the scan queue.