ISO 17873:2004 原子力施設—原子炉以外の原子力施設の換気システムの設計と運用の基準 | ページ 6

3.1

aerosol

solid particles and liquid droplets of all dimensions in suspension in a gaseous fluid

3.2

air-change rate

ratio between the ventilation air-flow rate of a containment enclosure or a compartment, during normal operating conditions, and the volume of this containment enclosure or compartment

3.3

air conditioning

arrangements allowing the sustainment of a controlled atmosphere (temperature, humidity, pressure, dust levels, gas content, etc.) in a closed volume

3.4

barrier

structural element, which defines the physical limits of a volume with a particular radiological environment and which prevents or limits releases of radioactive substances from this volume

3.5

balancing damper

control valve

adjustable device inserted in an aerodynamic duct allowing balancing of the fluid flow and/or the pressure of the fluid during plant operation

3.6

cell

or shielded enclosure

term generally used to designate an enclosure equipped with a shielding structure, of fairly large dimensions, possibly leaktight

3.7

containment

confinement

arrangement allowing users to maintain separate environments inside and outside an enclosure, blocking the movement between them of process materials and substances resulting from physical and chemical reactions which are potentially harmful to workers, the external environment, or to the handled products

Note 1 to entry: The word “confinement” is used in several IAEA documents to mean the function of confining radioactive or toxic products whereas “containment” is used to mean the physical barrier that achieves the objective of confinement, i.e. a confined area.

3.8

containment compartment

CC

compartment of which the walls (or the nearest walls of a volume that includes one or several fire compartments) are able to contain radioactive substances that would be generated by any plausible fire that could break out in one of the fire compartments included

Note 1 to entry: It is often more practicable to limit the spread of a fire by fire-resistant walls, and to prevent the spread of contamination in the adjacent volumes.

3.9

containment enclosure

enclosure designed to prevent either the leakage of products contained in the pertinent internal environment into the external environment, or the penetration of substances from the external environment into the internal environment, or both simultaneously

Note 1 to entry: This is a generic term used to designate all kinds of enclosures, including glove boxes, leaktight enclosures and shielded cells equipped with remotely operated devices.

3.10

containment system

system constituted by a coherent set of physical barriers and/or auxiliary dynamic systems intended to confine radioactive substances in order to ensure the safety of the workers and the public and the protection of the environment

3.11

contamination

presence of radioactive substances on or in a material or a human body or any place where they are undesirable or could be harmful

3.12

decontamination factor

measure of the efficiency achieved by a filtration system and corresponding to the ratio of the radiological contents of the inlet and outlet of the filtration system

3.13

discharge stack

duct (usually vertical) at the termination of the ventilation system, from which the air is discharged to atmosphere

3.14

dynamic confinement

action allowing, by maintaining a preferential air-flow circulation, the limitation of back-flow between two areas or between the inside and outside of an enclosure, in order to prevent radioactive substances being released from a given physical volume

3.15

filter

conventional term used to designate a device intended to trap solid or liquid particles suspended in gases or fluids or to trap gases themselves

Note 1 to entry: A particle filter consists of a filtering medium, generally made of a porous or fibrous material (i.e. glass fiber or paper) fixed within a frame or casing. During the manufacturing process, the filter is mounted in a leaktight manner in this frame, using a lute. Gas filters are generally found in physical or chemical process units where the primary aim is to trap certain gases.

3.16

fire compartment

FC

reference volume delimited by construction elements for which fire resistance has been chosen according to the plausible fire that could break out within this volume or penetrate into it

3.17

fire damper

fire blocking valve

device which is designed to prevent, generally by automatic action under specified conditions, the ingress of fire through a duct or through the walls of a room

3.18

fire load

heat energy that could be released by the complete combustion of the whole combustible contents of a volume, including the surfaces of the walls, partitions, floors and ceilings

3.19

gas cleaning

action (sometimes called “scrubbing”) that consists of decreasing the content of undesirable constituents in a fluid

Note 1 to entry: Aerosol filtration and iodine trapping are examples of gas cleaning.

3.20

iodine trap

scrubbing device, usually based on activated carbon, intended to remove volatile radioactive components such as radioactive iodine from the air or the ventilation gases

3.21

negative pressure or depression

pressure difference between the pressure of a given volume, which is maintained lower than the pressure in a reference volume or the external ambient pressure

3.22

negative pressure system

regulated ventilation system, which ensures a negative pressure between the ventilated area and an adjoining zone or the external ambient pressure

3.23

prefilter

filter fitted upstream of the main air filters to minimize, by removal of large particles, the dust burden on the latter

3.24

pressure drop

pressure loss in an air stream due to its passing through a section of ductwork, or a filter or fittings

3.25

process ventilation system

ventilation system that deals specifically with the active gases and aerosols arising within process equipment (such as reaction vessels, piping networks, evaporators and furnaces) but excludes the ventilation of the containment enclosures in which such equipment is generally located (e.g. hot cells, glove boxes, fume cupboards or high-radioactivity plant rooms)

3.26

safety flow rate

flow rate that guarantees air flow through any occasional or accidental opening, sufficient to either limit the back-flow of contamination (radioactive or other) from the working volume, or to avoid the pollution of products handled within the working volume

3.27

ventilation

organization of air-flow patterns within an installation

3.28

ventilation duct

envelope, generally of rectangular or circular section, allowing air or gas flow to pass through

3.29

ventilation system

totality of network components, such as ducts, fans, filter units and other equipment, that ensures ventilation and gas-cleaning functions as defined in the present document