ISO 18075:2018 パワーリアクター分析のための定常状態ニュートロニクス法 | ページ 6

3.1.1

application-dependent multigroup

discrete energy-group structure that is intermediate between the application-independent multigroup structure and a few-group structure

Note 1 to entry: The application-dependent multigroup structure can be such that the group constants are dependent on reactor composition through an estimated neutron energy spectrum. An application dependent Multigroup data set is one type of averaged data set.

3.1.2

application-independent multigroup

discrete energy-group structure that is sufficiently detailed that the group constants may be considered as being independent of reactor composition, geometry, or spectrum for a wide range of reactor analysis

Note 1 to entry: The application-independent multigroup structure can be employed directly in reactor-design spectrum calculations, or it can be employed to generate group constants in an application- dependent multigroup structure. An application-independent multigroup data set is one type of averaged data set.

3.1.3

cell

one or more reactor sections with associated coolant (and possibly additional moderator and structural material) which, for computational purposes, are assumed to form a spatially repeating array in the reactor

Note 1 to entry: The simplest example of a cell is the “pin cell” in which a single fuel rod or pin is surrounded by coolant (e.g. light water, heavy water, or sodium). Another example is a bundle of fuel rods cooled by heavy water within a housing, surrounded by a heavy water moderator space.

Note 2 to entry: More complex geometric configurations are also used for some applications. These are often referred to as “supercells”, or sometimes “(fuel) assembly cells”, although the exact definition of the term varies greatly between reactor types and is even somewhat subjectively defined for a particular reactor type. Supercells, in the context of this document, represent more complex “cell” configurations which involve a collection of contiguous cells forming an assumed repeating array within the reactor, or augmented cells incorporating additional regions to serve as a computational artifice, e.g. to account for significant spectrum effects due to compositions outside the cell, or cell configurations including a reactivity device in addition to fuel, coolant, moderator and poison.

3.1.4

data set

collection of microscopic cross-sections and nuclear constants encompassing the range of materials and reaction processes needed for the application area of interest

3.1.4.1

averaged data set

data set prepared by averaging an evaluated data set or a processed continuous data set with a specified weighting function over a specified energy group structure

Note 1 to entry: The group structure and weighting functions may be selected to be application dependent. Application-independent averaged data sets for a wide range of reactor analysis, e.g. light water reactors, are dealt with in American National Standard Nuclear Data Sets for Reactor Design Calculations, ANSI/ANS-19.1-2002 (R2011)^[1].

3.1.4.2

evaluated data set

data set which is completely and uniquely specified over the ranges of energy and angles important to reactor calculations

Note 1 to entry: Such a data set is based upon available information (experimental measurement results and nuclear theories) and employs a judgment as to the best physical description of the interaction process.

Note 2 to entry: An evaluated data set is intended to be independent of reactor composition, geometries, energy group structures, and spectra.

3.1.4.3

processed continuous data set

data set prepared by expansion or compaction of an evaluated data set using specified algorithms

Note 1 to entry: Such a data set is intended to be independent of reactor compositions, geometries, energy-group structures, and spectra.

3.1.5

experimental data

any experimentally measured quantity or quantities

Note 1 to entry: As such it is applied herein to both differential cross-section measurements and integral measurements (e.g. control-rod worth) obtained from reactor experiments or operations.

3.1.6

few-group

energy-group (typically 2-group) structure that is adopted for a particular application

Note 1 to entry: The few-group constants for a region are dependent on a specific reactor composition and geometry through a calculated energy spectrum, and are also dependent on temperature.

3.1.7

lattice

lattice cell

normally refers to a fuel-assembly cell with its associated immediate environment, such as the volume of moderator associated with it

3.1.8

calculation method

mathematical equations, approximations, assumptions, associated numerical parameters, and calculational procedures that yield the calculated results

Note 1 to entry: When more than one step is involved in the calculation, the entire sequence of steps comprises the “calculation method”.

3.1.9

reactivity

property of the whole reactor, not just of a given material composition, is the ratio of the net production rate of neutrons (excess of neutrons produced by fission over those absorbed) to the production rate due to fissions

Note 3 to entry: The effective multiplication factor k_eff is the inverse of λ. Reactivity is a unitless, pure number. It is, however, often written in terms of smaller “units”, such as milli-k = 0,001, pcm = 0,000 01 = 10⁻⁵ or “dollars” (and cents) ここで, 1 dollar is taken as the value of the delayed-neutron fraction in the system of interest.

3.1.10

validation

process of determining the degree to which a model is an accurate representation of the real world from the perspective of the intended uses of the model

3.1.11

verification calculation

process of determining that a model implementation accurately represents the developer’s conceptual description of the model and the solution to the model