Definitions - s3007cn10011

DOE-STD-3007-93

BIAS - A measure of the systematic disagreement between the results calculated by a method and

experimental data. The uncertainty in the bias is a measure of both the precision of the

calculations and the accuracy of the experimental data.

CALCULATIONAL METHOD - The mathematical equations, approximations, assumptions,

associated numerical parameters (e.g., neutron cross sections), and calculational procedures that

yield the calculated results.

CONTINGENCY - A possible but unlikely change in a condition/control important to the

nuclear criticality safety of a fissionable material operation that would, if it occurred, reduce the

number of barriers (either administrative or physical) that are intended to prevent an accidental

nuclear criticality.

CRITICALITY SAFETY EVALUATION (CSE) - A documented process that establishes the

technical basis for nuclear criticality safety and provides subcritical operating values.

CREDIBLE - Offering reasonable grounds for being believed on the basis of commonly

acceptable engineering judgment. Assigning a numerical probability that defines credible is not

required when demonstrating compliance with the double contingency principle.

DESIGN FEATURES - Passive or active features that are necessary to prevent or reduce the

probability of a criticality accident.

DOUBLE-CONTINGENCY PRINCIPLE [Per DOE 5480.24 7a(2)(a)*] - Process designs

shall incorporate sufficient factors of safety to require at least two unlikely, independent, and

concurrent changes in process conditions before a criticality accident is possible. Protection shall

be provided by either:

The control of two independent process parameters (which is the preferred approach, if

practical) or

A system of multiple (at least two) controls on a single parameter.

In all cases, no (credible) single failure shall result in the potential for a criticality accident.

*NOTE: DOE 5480.24 has been replaced by DOE O 420.1, Section 4.3.

PROCESS PARAMETER - A physical property whose value affects the nuclear reactivity of a

system. Parameters include the mass, density, and isotopic enrichment of fissionable material; the

geometry, reflection, and interaction conditions of the system; and the moderation, composition

and neutron absorption characteristics of the fissionable material mixture and other system

materials.