|  | G |
SECTION G — PHYSICS

|  | G |
Note(s) In this section, the following term is used with the meaning indicated: "variable" (as a noun) means a feature or property (e.g., a dimension, a physical condition such as temperature, a quality such as density or colour) which, in respect of a particular entity (e.g., an object, a quantity of a substance, a beam of light) and at a particular instant, is capable of being measured; the variable may change, so that its numerical expression may assume different values at different times, in different conditions or in individual cases, but may be constant in respect of a particular entity in certain conditions or for practical purposes (e.g., the length of a bar may be regarded as constant for many purposes). Attention is drawn to the definitions of terms or expressions used, appearing in the notes of several of the classes in this section, in particular those of "measuring" in class Fulltext... Hierarchy... Expanded...G01 and "control" and "regulation" in class Fulltext... Hierarchy... Expanded...G05. Classification in this section may present more difficulty than in other sections, because the distinction between different fields of use rests to a considerable extent on differences in the intention of the user rather than on any constructional differences or differences in the manner of use, and because the subjects dealt with are often in effect systems or combinations, which have features or parts in common, rather than "things", which are readily distinguishable as a whole. For example, information (e.g., a set of figures) may be displayed for the purpose of education or advertising (Fulltext... Hierarchy... Expanded...G09), for enabling the result of a measurement to be known (Fulltext... Hierarchy... Expanded...G01), for signalling the information to a distant point or for giving information which has been signalled from a distant point (Fulltext... Hierarchy... Expanded...G08). The words used to describe the purpose depend on features that may be irrelevant to the form of the apparatus concerned, for example, such features as the desired effect on the person who sees the display, or whether the display is controlled from a remote point. Again, a device which responds to some change in a condition, e.g., in the pressure of a fluid, may be used, without modification of the device itself, to give information about the pressure (Fulltext... Hierarchy... Expanded...G01L) or about some other condition linked to the pressure (another subclass of class Fulltext... Hierarchy... Expanded...G01, e.g., Fulltext... Hierarchy... Expanded...G01K for temperature), to make a record of the pressure or of its occurrence (Fulltext... Hierarchy... Expanded...G07C), to give an alarm (Fulltext... Hierarchy... Expanded...G08B), or to control another apparatus (Fulltext... Hierarchy... Expanded...G05). The classification scheme is intended to enable things of a similar nature (as indicated above) to be classified together. It is therefore particularly necessary for the real nature of any technical subject to be decided before it can be properly classified.

NUCLEONICS

|  | G21 |
NUCLEAR PHYSICS; NUCLEAR ENGINEERING

|  | G21D |
NUCLEAR POWER PLANT (electric or magnetic analogue computers, e.g. simulators, for nuclear physics Fulltext... Hierarchy... Expanded...G06G 7/54)

P:40 |  | G21D 1/00 |
Details of nuclear power plant (control Fulltext... Hierarchy... Expanded...G21D 3/00)

|  | G21D 1/02 |
· | Arrangements of auxiliary equipment

|  | G21D 1/04 |
· | Pumping arrangements (by means within the reactor pressure vessel Fulltext... Hierarchy... Expanded...G21C 15/24; electrodynamic pumps Fulltext... Hierarchy... Expanded...H02K 44/02)

P:0 |  | G21D 3/00 |
Control of nuclear power plant (control of nuclear reaction in general Fulltext... Hierarchy... Expanded...G21C 7/00)

|  | G21D 3/02 |
· | Manual control

|  | G21D 3/04 |
· | Safety arrangements (emergency protection of reactor Fulltext... Hierarchy... Expanded...G21C 9/00)

|  | G21D 3/06 |
· · | responsive to faults within the plant (in the reactor Fulltext... Hierarchy... Expanded...G21C 9/00)

|  | G21D 3/08 |
· | Regulation of any parameters in the plant

|  | G21D 3/10 |
· · | by a combination of a variable derived from neutron flux with other controlling variables, e.g. derived from temperature, cooling flow, pressure

|  | G21D 3/12 |
· · | by adjustment of the reactor in response only to changes in engine demand

|  | G21D 3/14 |
· · · | Varying flow of coolant

|  | G21D 3/16 |
· · · | Varying reactivity

|  | G21D 3/18 |
· · | by adjustment of plant external to the reactor only in response to change in reactivity

P:20 |  | G21D 5/00 |
Arrangements of reactor and engine in which reactor-produced heat is converted into mechanical energy

|  | G21D 5/02 |
· | Reactor and engine structurally combined, e.g. portable

|  | G21D 5/04 |
· | Reactor and engine not structurally combined

|  | G21D 5/06 |
· · | with engine working medium circulating through reactor core

|  | G21D 5/08 |
· · | with engine working medium heated in a heat exchanger by the reactor coolant

|  | G21D 5/10 |
· · · | Liquid working medium partially heated by reactor and vaporised by heat source external to the core, e.g. with oil heating

|  | G21D 5/12 |
· · · | Liquid working medium vaporised by reactor coolant

|  | G21D 5/14 |
· · · · | and also superheated by reactor coolant

|  | G21D 5/16 |
· · · · | superheated by separate heat source

P:10 |  | G21D 7/00 |
Arrangements for direct production of electric energy from fusion or fission reactions (obtaining electric energy from radioactive sources Fulltext... Hierarchy... Expanded...G21H 1/00)

|  | G21D 7/02 |
· | using magneto-hydrodynamic generators

|  | G21D 7/04 |
· | using thermoelectric elements (structural combination of fuel element with thermoelectric element Fulltext... Hierarchy... Expanded...G21C 3/40; thermoelectric elements per se Fulltext... Hierarchy... Expanded...H01L 35/00, Fulltext... Hierarchy... Expanded...H01L 37/00)

P:30 |  | G21D 9/00 |
Arrangements to provide heat for purposes other than conversion into power, e.g. for heating buildings