Registered Nuclear Safety Engineer key terms

The rate of nuclear transformations in a sample, distinguished from energy deposition in a person or a radiation protection dose quantity.

The time over which the expected number of undecayed nuclei is halved under the stated radioactive-decay model.

The parameter relating a radioactive population to its expected transformation rate in an exponential decay model, with inverse-time units.

The energy deposited by ionizing radiation per unit mass, measured in gray and not identical to activity.

A radiation protection quantity combining relevant weighted tissue contributions, not a direct patient-specific prediction of an individual health outcome.

The chain-reaction state in which successive neutron generations are sustained in balance, distinct from prompt criticality or an absence of heat.

The loss of neutrons across a system boundary, distinguished from neutron absorption inside the specified material or reactor model.

A measure related to departure from criticality, whose sign and numerical convention should be stated before comparisons or calculations.

A neutron emitted following decay of certain fission products, with an important role in the time response of reactor systems.

Heat generated by radioactive decay after operation, which does not disappear immediately when the chain reaction is shut down.

The receiving system or environment to which heat is ultimately transferred along the applicable removal path and boundary conditions.

A layered safety approach involving prevention, control and mitigation, rather than reliance on one apparently reliable protective device.

Provision of additional components for a function, which does not by itself establish independence from common-cause failures.

Use of differing principles or designs to reduce selected shared vulnerabilities, without guaranteeing that every dependency has disappeared.

Failure of multiple provisions because of a shared cause, which can defeat an analysis that assumes complete independence.

A provision that helps prevent or limit radioactive material release, assessed with its actual function, condition and dependencies.

A specified description of radioactive material available for release or transport in an analysis, with its time and assumptions identified.

Variation in observed radiation counts under the measurement model, distinguished from calibration, geometry and background-related systematic effects.

Unwanted radioactive material on or within a person, object or environment, distinguished from irradiation without transferred material.

The facility operator responsibility for nuclear safety, which is not transferred to the regulator merely because inspection occurs.