Junior Operator Grade I key terms

A rapid, automatic or manual insertion of control rods and shutdown of the chain reaction to protect the fuel. It is triggered by protective logic when parameters exceed setpoints.

The mechanical and electrical assembly that moves control rods into or out of the core. It provides normal positioning, scram insertion, and rod position indication.

The safety-related instrumentation and logic that senses abnormal conditions and automatically initiates a scram or other protective action. It is designed to fail safe and is periodically tested.

The predetermined value of a measured parameter at which a protective or control action is initiated. Setpoints are established by analysis and verified during surveillance testing.

The closed piping circuit that carries heat from the reactor core to the steam generators or turbine. It includes pumps, valves, and instrumentation operating at reactor pressure.

A large pump that forces primary coolant through the core to remove heat. Loss of pump flow reduces heat removal capability and may require protective action.

A vessel connected to the primary loop that maintains coolant pressure using steam and water. Heaters and spray control pressure and limit pressure transients.

The difference between the actual coolant temperature and its saturation temperature at the prevailing pressure. A positive margin confirms the coolant is liquid and not boiling.

The boiling temperature of a fluid at a given pressure. It is used to determine subcooling margin and to interpret pressure and temperature indications.

Coolant flow driven by density differences rather than pumps, caused by heated fluid rising and cooler fluid descending. It provides passive heat removal after pump trips.

Heat produced by radioactive decay of fission products after the chain reaction stops. It continues for a long time and must be removed by cooling systems.

A system that removes decay heat from the primary coolant during shutdown and cooldown. It operates at lower pressure and temperature than normal cooling systems.

A set of safety systems that inject water into the core after a loss-of-coolant accident. It includes accumulators, low-pressure and high-pressure injection, and spray.

A design-basis event in which primary coolant escapes through a break, threatening core cooling. Operators respond by isolating the break and starting emergency injection.

The injection of borated water into the primary system to restore inventory and shut down the reactor. It is initiated automatically by low pressure or low level signals.

Adding boron, a neutron absorber, to the primary coolant to reduce reactivity. It is used for shutdown, xenon compensation, and controlling power during transients.

The degree to which a reactor is removed from criticality. Positive reactivity increases power, negative decreases it, and zero means steady-state critical operation.

The condition in which a reactor sustains a steady fission chain reaction with neutron production balanced by absorption and leakage. Power remains constant when critical.

The buildup of xenon-135, a strong neutron absorber, after power changes. It can cause reactivity swings and must be managed during startup and shutdown.

The sequence of operations that brings a reactor from shutdown to critical and then to normal power. It includes checks, rod withdrawal, and monitoring of reactivity.

Controlled reduction of primary coolant temperature and pressure toward shutdown conditions. It requires careful control of cooling rate to limit thermal stress.

Internal stress caused by uneven temperature changes across metal components. Excessive rates of heating or cooling can cause cracking or damage.

The piping, vessels, and components that contain reactor coolant under pressure. Its integrity is essential to prevent loss of coolant and release of radioactivity.

A design and analysis concept ensuring a crack would leak detectably before catastrophic failure. It supports inspection and monitoring of pressure boundaries.

Inspection methods such as ultrasonic, radiographic, and visual testing that detect flaws without damaging components. Results are compared to acceptance criteria.

A scheduled test that verifies safety systems and components meet required performance criteria. Results are documented and reviewed to confirm operability.

The documented evaluation that a system or component can perform its required safety function. It is required when equipment is degraded or found out of spec.

The regulatory limits and conditions under which a plant is licensed to operate. They define required equipment, action times, and surveillance requirements.

A technical specification condition that defines the minimum equipment and performance needed to operate safely. Failure requires prompt corrective action or shutdown.

The radiation protection principle of keeping doses and releases below regulatory limits by using practical, cost-effective measures. It guides work planning and shielding decisions.

A measure of radiation exposure to tissue that accounts for the biological effect of different radiation types. It is expressed in sieverts or rem.

A device worn by a worker to measure accumulated radiation dose. It is read periodically and recorded in the individual dose record.

Radioactive material present where it is not wanted, such as on surfaces, clothing, or skin. It is controlled by surveys, protective clothing, and decontamination.

Management of coolant and system chemistry to limit corrosion and radioactivity transport. It includes pH, dissolved oxygen, chloride, and boron concentration limits.

A formal tag and lock used to isolate equipment from energy sources before maintenance. It prevents accidental startup or release of hazardous energy.

The procedure of locking energy isolation devices and attaching warning tags. It protects workers from unexpected energization during maintenance or repair.

A short meeting before a task to review scope, hazards, roles, and contingencies. It improves situational awareness and reduces error.

A communication practice in which the sender states a message, the receiver repeats it back, and the sender confirms correctness. It prevents misunderstandings in operations.

The study and management of factors that affect worker error, such as attention, workload, and procedures. Tools like self-checking and peer-checking reduce mistakes.