KB_OAT_Bias_Factors.txt

Purpose

KB_OAT_Bias_Factors.txt simulates failed or biased control panel instrumentation as perceived by the Operator Action Taker. Under normal conditions the OAT perceives the actual parameter value directly from the RELAP thermal-hydraulic model. This file overrides that behavior by applying a bias factor to the value the operator sees, while leaving the underlying simulation value unchanged.

When a parameter is biased, the OAT may use inaccurate data when:

• Evaluating procedure step expectations.
• Evaluating knowledge-based action prerequisites.
• Evaluating activation criteria for hard-wired mental beliefs.

Supported failure modes include: stuck indicators, indicators that cannot read above or below a threshold, proportional (gain) errors, and constant additive offsets.

INFO

The parameter name entered in this file must exactly match a parameter defined in ControlPanel.txt. Spaces are not permitted in parameter names; use the underbar character _ as a substitute.

Parameters Per Entry

Parameter	Type	Description	Example Value
number_parameters	Integer (>= 0)	Total count of biased parameter entries in the file. If set to 0, the remainder of the file is ignored. If > 0, exactly that many data lines must follow.	2
parameter_name	String	Name of the control panel parameter to be biased. Must match an entry in ControlPanel.txt. No spaces allowed.	SG_A_WR_Level
activation_time	Double (>= 0.0)	Simulation time in seconds at which the bias becomes active. Before this time the operator perceives the actual parameter value; after this time the bias is applied.	0.0
option_code	Integer	Integer code specifying the type of bias to apply. See the option code table below.	3007
bias_factor	Double	The reference value or scaling factor used by the selected option code. Units and range must be consistent with the normal output range of the indicator.	0.16

Option Codes

Code	Mnemonic	Integer	Behavior
VGT	Greater-Than Clamp	3006	Perceived value is always > bias_factor. If actual > bias_factor, actual is perceived. If actual <= bias_factor, operator perceives bias_factor. Models an indicator that cannot read below a threshold.
VGE	Greater-Than-or-Equal Clamp	3007	Perceived value is always >= bias_factor. Functionally similar to VGT. If actual >= bias_factor, actual is perceived. If actual < bias_factor, operator perceives bias_factor.
VEQ	Stuck / Fixed Value	3008	Operator always perceives bias_factor regardless of actual value. Models an indicator stuck at a constant reading.
VLE	Less-Than-or-Equal Clamp	3009	Perceived value is always <= bias_factor. If actual <= bias_factor, actual is perceived. If actual > bias_factor, operator perceives bias_factor. Models an indicator that cannot read above a threshold.
VLT	Less-Than Clamp	3010	Perceived value is always < bias_factor. Functionally similar to VLE. If actual < bias_factor, actual is perceived. If actual > bias_factor, operator perceives bias_factor.
VPROPORTIONAL	Proportional (Gain) Error	3111	Perceived value = actual value × bias_factor. Models a constant percentage error (e.g., bias_factor = 1.10 for a +10% high-reading indicator).
VADDITIVE	Additive (Offset) Error	3112	Perceived value = actual value + bias_factor. Models a constant offset bias on the indicator.

File Format

Number_of_biased_parameters    NUMBER_PARAMETERS
PARAMETER_NAME_1
ACTIVATION_TIME_1              OPTION_CODE_1
                               BIAS_FACTOR_1
PARAMETER_NAME_2
ACTIVATION_TIME_2              OPTION_CODE_2
                               BIAS_FACTOR_2

Line layout

Each biased parameter occupies one data line consisting of: a parameter name string, an activation time (double), an option code integer, and a bias factor double. In the sample input format used in the manual, the activation time and option code appear on the same line separated by whitespace, and the bias factor follows on the next line. Ensure the count declared in Number_of_biased_parameters matches the actual number of entries.

Sample Input

Number_of_biased_parameters    2
SG_A_WR_Level
0.0                            3007
                               0.16
SG_C_WR_Level
100.0                          3112
                               0.15

Explanation of the Sample

SG_A_WR_Level — Starting at simulation time 0.0 seconds, option code 3007 (VGE) is applied with a bias factor of 0.16. The SG A wide-range level indicator will read no lower than 0.16 (16%). When the actual value exceeds 0.16 the actual value is perceived; when the actual value falls below 0.16 the operator perceives 0.16.

SG_C_WR_Level — Starting at simulation time 100.0 seconds, option code 3112 (VADDITIVE) is applied with a bias factor of 0.15. A constant additive offset of +0.15 is added to the SG C wide-range level reading perceived by the operator. Before 100.0 seconds no bias is active.

WARNING

An incorrect number_parameters count will cause an input file processing error. If no bias factors are needed, set number_parameters to 0 and leave the remainder of the file empty.

Modeling a stuck indicator

To simulate a pressurizer level indicator stuck at 0.50 from the start of the simulation:

Number_of_biased_parameters    1
PZR_Level
0.0                            3008
                               0.50