EPRI UPDATED 2026 EXAM SCRIPT QUESTIONS AND
ANSWERS GRADED A+
✔✔Define the design basis accident types - ✔✔· Mechanical failure of a single
component leading to the release of radioactive material from one or more barriers. The
components referred to here are not those that act as radioactive material barriers.
Examples of mechanical failure are breakage of the coupling between a control rod
drive and the control rod, and failure of a spring used to close an isolation valve.
· Arbitrary rupture of any single pipe up to and including complete severance of the
largest pipe in the nuclear system process barrier: This type of accident is considered
only under conditions in which the nuclear system is pressurized.
✔✔Define PRA - ✔✔Probabilistic Risk Assessment (PRA), also known as Probabilistic
Safety Assessment (PSA), is a quantitative assessment of the risk associated with plant
operation and maintenance. This risk is measured by how often different events that
lead to severe core damage occur. The original goal of PRA was to analyze and
understand severe accident behavior, and then identify and fix the plant vulnerabilities.
✔✔Define PRA's attributes - ✔✔Some of the attributes of a PRA are:
· It realistically models plant design, plant procedures, and human performance
· It is a best estimate
· It is not a safety-related tool
· It is a mathematical model of all important plant systems using plant-specific data for
critical components
· It models the plant response for various initiating events using calculated system
reliabilities
· It takes into account realistically usable mitigating equipment
PRA evaluates internal initiating events such as a LOCA and station blackout, and
external events such as earthquakes, flooding, or a hurricane. PRA calculates the
probability of a specific event that leads to core damage.
✔✔Which engineering groups support PRA - ✔✔Design engineers
Systems engineers
PRA engineers
✔✔Identify how PRA supports various engineering activities, including examples
(design engineers) - ✔✔Use PRA when:
· Installing new safety-related equipment to the plant
· Adding a backup cooling supply to a piece of safety-related equipment
· Changing control room indications
· Replacing an AOV with an MOV
,· Changing failure mode of equipment
· Evaluating the impact of a modification on safety margin and reliability
✔✔Identify how PRA supports various engineering activities, including examples
(systems engineers) - ✔✔Use PRA when:
· Supporting justifications for continued operation
· Incorporating Maintenance Rule (10CFR50.65)
· Determining the Mitigating Systems Performance Index (MSPI)
· Determining risk factors for on-line work activities
· Providing input for plant testing
✔✔Identify how PRA supports various engineering activities, including examples (PRA
engineers) - ✔✔Use PRA when:
· Using the Significance Determination Process
· Using the Mitigating Systems Performance Index (MSPI)
· Using the Reactor Oversight Process
· Providing basis for Equipment out of Service (EOOS)
· Providing basis for risk-informed Technical Specifications
✔✔Define safety limits - ✔✔Safety limits are limits on the specific nuclear process
variables imposed by technical specifications (the actual values at your plant may
differ). These limits are set to ensure the integrity of the fission product barriers.
✔✔Examples of safety limits for a BWR are (4) - ✔✔· Maintain Thermal Power less than
some maximum Reactor Thermal Power (RTP) with low reactor coolant system
pressure and low core flow
· Minimum Critical Power Ratio (MCPR) greater than some minimum limit with higher
reactor coolant system pressure and core flows above some minimum value
· Reactor water level greater than the top of active irradiated fuel
· Reactor steam dome pressure less than a maximum limit
✔✔Examples of safety limits for a PWR in modes 1 or 2 are (3) - ✔✔· Fuel pin
centerline temp less than some maximum limit
· Departure from Nucleate Boiling Ratio (DNBR) greater than some minimum value
· RCS pressure less than some maximum value
✔✔Define limiting conditions for operation (LCOs) - ✔✔LCOs specify the minimum
acceptable levels of system performance necessary to assure safe operation of the
facility.
✔✔A typical LCO has the following four major sections: - ✔✔a. Statement- This is the
requirement. An example statement is: "A recirculation loop Flow Control Valve (FCV)
shall be OPERABLE in each operating recirculation loop."
, b. Applicability- This section lists the reactor modes when the requirements of the LCO
must be met. Modes are specific plant conditions based on reactor coolant system
temperature, reactor power or criticality, and reactor vessel head integrity
c. Actions
· Specify the actions that must be met
· The time limits for completing those actions when limited conditions of operation
(LCOs) are not satisfied
d. Surveillance Requirements- Surveillance requirements are testing or verification
activities performed on a specified frequency that ensure the LCO requirements
continue to be met
✔✔State the hierarchy of limits on safety parameters (7) - ✔✔(When considering plant
equipment, there are several layers of protection for the safety-significant parameters.)
1. Normal Automatic Controls
2. Alarms/Operator Actions
3. Automatic Trips/Relief
4. Emergency Operating Procedure/Operator Action
5. Technical Specification Limit
6. Design/Test Limit
7. Break Point
✔✔Normal Automatic Controls - ✔✔Most plant parameters have controls that should
keep them within established setpoints
✔✔Alarms/Operator Actions - ✔✔Alarms are typically initiated to let the operator know
when a parameter has deviated from where it should be maintained by the automatic
controls. This will allow the operators to take action before the trip or relief setpoint is
reached. Those actions will be guided by procedures such as normal operating
procedures, alarm response procedures, and abnormal operating procedures.
✔✔Automatic Trips/Relief - ✔✔If safety significant parameters deviate too far from
normal, the equipment can take two actions to protect itself. In the case of over
temperature, voltage, pressure, etc. the equipment can automatically trip to stop the
addition of more energy. In the case of pressure, the equipment can additionally relieve
the energy through the use of relief valves. It is possible for the equipment to be
designed to either relieve or trip first. Then if the condition doesn't improve, it could
perform the other.If safety significant parameters deviate too far from normal, the
equipment can take two actions to protect itself. In the case of over temperature,
voltage, pressure, etc. the equipment can automatically trip to stop the addition of more
ANSWERS GRADED A+
✔✔Define the design basis accident types - ✔✔· Mechanical failure of a single
component leading to the release of radioactive material from one or more barriers. The
components referred to here are not those that act as radioactive material barriers.
Examples of mechanical failure are breakage of the coupling between a control rod
drive and the control rod, and failure of a spring used to close an isolation valve.
· Arbitrary rupture of any single pipe up to and including complete severance of the
largest pipe in the nuclear system process barrier: This type of accident is considered
only under conditions in which the nuclear system is pressurized.
✔✔Define PRA - ✔✔Probabilistic Risk Assessment (PRA), also known as Probabilistic
Safety Assessment (PSA), is a quantitative assessment of the risk associated with plant
operation and maintenance. This risk is measured by how often different events that
lead to severe core damage occur. The original goal of PRA was to analyze and
understand severe accident behavior, and then identify and fix the plant vulnerabilities.
✔✔Define PRA's attributes - ✔✔Some of the attributes of a PRA are:
· It realistically models plant design, plant procedures, and human performance
· It is a best estimate
· It is not a safety-related tool
· It is a mathematical model of all important plant systems using plant-specific data for
critical components
· It models the plant response for various initiating events using calculated system
reliabilities
· It takes into account realistically usable mitigating equipment
PRA evaluates internal initiating events such as a LOCA and station blackout, and
external events such as earthquakes, flooding, or a hurricane. PRA calculates the
probability of a specific event that leads to core damage.
✔✔Which engineering groups support PRA - ✔✔Design engineers
Systems engineers
PRA engineers
✔✔Identify how PRA supports various engineering activities, including examples
(design engineers) - ✔✔Use PRA when:
· Installing new safety-related equipment to the plant
· Adding a backup cooling supply to a piece of safety-related equipment
· Changing control room indications
· Replacing an AOV with an MOV
,· Changing failure mode of equipment
· Evaluating the impact of a modification on safety margin and reliability
✔✔Identify how PRA supports various engineering activities, including examples
(systems engineers) - ✔✔Use PRA when:
· Supporting justifications for continued operation
· Incorporating Maintenance Rule (10CFR50.65)
· Determining the Mitigating Systems Performance Index (MSPI)
· Determining risk factors for on-line work activities
· Providing input for plant testing
✔✔Identify how PRA supports various engineering activities, including examples (PRA
engineers) - ✔✔Use PRA when:
· Using the Significance Determination Process
· Using the Mitigating Systems Performance Index (MSPI)
· Using the Reactor Oversight Process
· Providing basis for Equipment out of Service (EOOS)
· Providing basis for risk-informed Technical Specifications
✔✔Define safety limits - ✔✔Safety limits are limits on the specific nuclear process
variables imposed by technical specifications (the actual values at your plant may
differ). These limits are set to ensure the integrity of the fission product barriers.
✔✔Examples of safety limits for a BWR are (4) - ✔✔· Maintain Thermal Power less than
some maximum Reactor Thermal Power (RTP) with low reactor coolant system
pressure and low core flow
· Minimum Critical Power Ratio (MCPR) greater than some minimum limit with higher
reactor coolant system pressure and core flows above some minimum value
· Reactor water level greater than the top of active irradiated fuel
· Reactor steam dome pressure less than a maximum limit
✔✔Examples of safety limits for a PWR in modes 1 or 2 are (3) - ✔✔· Fuel pin
centerline temp less than some maximum limit
· Departure from Nucleate Boiling Ratio (DNBR) greater than some minimum value
· RCS pressure less than some maximum value
✔✔Define limiting conditions for operation (LCOs) - ✔✔LCOs specify the minimum
acceptable levels of system performance necessary to assure safe operation of the
facility.
✔✔A typical LCO has the following four major sections: - ✔✔a. Statement- This is the
requirement. An example statement is: "A recirculation loop Flow Control Valve (FCV)
shall be OPERABLE in each operating recirculation loop."
, b. Applicability- This section lists the reactor modes when the requirements of the LCO
must be met. Modes are specific plant conditions based on reactor coolant system
temperature, reactor power or criticality, and reactor vessel head integrity
c. Actions
· Specify the actions that must be met
· The time limits for completing those actions when limited conditions of operation
(LCOs) are not satisfied
d. Surveillance Requirements- Surveillance requirements are testing or verification
activities performed on a specified frequency that ensure the LCO requirements
continue to be met
✔✔State the hierarchy of limits on safety parameters (7) - ✔✔(When considering plant
equipment, there are several layers of protection for the safety-significant parameters.)
1. Normal Automatic Controls
2. Alarms/Operator Actions
3. Automatic Trips/Relief
4. Emergency Operating Procedure/Operator Action
5. Technical Specification Limit
6. Design/Test Limit
7. Break Point
✔✔Normal Automatic Controls - ✔✔Most plant parameters have controls that should
keep them within established setpoints
✔✔Alarms/Operator Actions - ✔✔Alarms are typically initiated to let the operator know
when a parameter has deviated from where it should be maintained by the automatic
controls. This will allow the operators to take action before the trip or relief setpoint is
reached. Those actions will be guided by procedures such as normal operating
procedures, alarm response procedures, and abnormal operating procedures.
✔✔Automatic Trips/Relief - ✔✔If safety significant parameters deviate too far from
normal, the equipment can take two actions to protect itself. In the case of over
temperature, voltage, pressure, etc. the equipment can automatically trip to stop the
addition of more energy. In the case of pressure, the equipment can additionally relieve
the energy through the use of relief valves. It is possible for the equipment to be
designed to either relieve or trip first. Then if the condition doesn't improve, it could
perform the other.If safety significant parameters deviate too far from normal, the
equipment can take two actions to protect itself. In the case of over temperature,
voltage, pressure, etc. the equipment can automatically trip to stop the addition of more
