ISO 12749-5:2018
(Main)Nuclear energy, nuclear technologies, and radiological protection — Vocabulary — Part 5: Nuclear reactors
Nuclear energy, nuclear technologies, and radiological protection — Vocabulary — Part 5: Nuclear reactors
ISO 12749-5:2018 encompasses the collection of terms, definitions, notes and examples corresponding to nuclear reactors, excluding quantitative data. It provides the minimum essential information for each nuclear reactor concept represented by a single term. Full understanding of concepts requires background knowledge of the nuclear field. It is intended to facilitate communication and promote common understanding. The scope of ISO 12749-5:2018 covers the whole field of nuclear reactors at a broad surface level.
Énergie nucléaire, technologies nucléaires, et radioprotection — Vocabulaire — Partie 5: Réacteurs nucléaires
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 12749-5
First edition
2018-02
Nuclear energy, nuclear technologies,
and radiological protection —
Vocabulary —
Part 5:
Nuclear reactors
Énergie nucléaire, technologies nucléaires, et radioprotection —
Vocabulaire —
Partie 5: Réacteurs nucléaires
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
Annex A (informative) Methodology used in the development of the vocabulary .34
Bibliography .46
Alphabetical index .47
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
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on the ISO list of patent declarations received (see www .iso .org/ patents).
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URL: www .iso .org/ iso/ foreword .html.
This document was prepared by ISO/TC 85, Nuclear energy, nuclear technologies, and radiological
protection.
A list of all the parts in the ISO 12749 series can be found on the ISO website.
iv © ISO 2018 – All rights reserved
Introduction
This document provides terms and definitions for main concepts in the whole area of nuclear reactor
science, technology, engineering, projects and operations, excluding quantitative data. Terminological
data are taken from ISO standards developed by TC 85/SC 6, from other technically validated documents
issued by international organizations, especially IAEA and IEC, while a number of definitions have been
drafted by WG 1 experts on the basis of their experience and after detailed discussions on concept
characteristics, the best wording for their designations and definitions, as well as the most important
links between concepts.
In most cases, international consensus exists among the communities of nuclear reactor specialists
world-wide, on the most relevant concepts in the nuclear reactor area. Nevertheless, clear and
unambiguous terms for these concepts are also needed.
The foregoing needs also to be considered together with the fact that a large number of people are
involved in the broad nuclear reactor area, having different scopes and levels of scientific and
technical knowledge and frequently having very specific activities within that broad field. Thus,
there can be different understandings and assumptions about concepts. Hence, the result could be a
poor communication that might lead into unexpected, different risky situations or consequences, if a
conceptual difference is behind.
Conceptual arrangement of terms and definitions is based on concepts systems that show corresponding
relationships among nuclear reactors concepts. Such arrangement provides users with a structured
view of the nuclear energy sector and will facilitate common understanding of all related concepts.
Besides, concepts systems and conceptual arrangement of terminological data will be helpful to any
kind of user because it will promote clear, accurate and useful communication.
Structure of the vocabulary
The terminology entries are presented in the conceptual order of the English preferred terms. Both
a systematic index and an alphabetical index are included at the end of the standard. The structure
of each entry is in accordance with ISO 10241-1. See also Annex A for the methodology used in the
development of the vocabulary.
All the terms included in this document deal exclusively with nuclear reactor technology. When selecting
terms and definitions, special care has been taken to include the terms that need to be defined, that is
to say, either because the definitions are essential to the correct understanding of the corresponding
concepts or because some specific ambiguities need to be addressed. The notes appended to certain
definitions offer clarification or examples to facilitate understanding of the concepts described.
According to the title, the vocabulary deals with concepts belonging to the general nuclear energy field
within which concepts in the nuclear reactors sub-field are taken into account.
Looking for an easier presentation of the required large number of defined concepts, the content of this
document has been split into nine headings as shown below, which makes easier any search of terms or
relationships between concepts.
vi © ISO 2018 – All rights reserved
INTERNATIONAL STANDARD ISO 12749-5:2018(E)
Nuclear energy, nuclear technologies, and radiological
protection — Vocabulary —
Part 5:
Nuclear reactors
1 Scope
This document encompasses the collection of terms, definitions, notes and examples corresponding
to nuclear reactors, excluding quantitative data. It provides the minimum essential information for
each nuclear reactor concept represented by a single term. Full understanding of concepts requires
background knowledge of the nuclear field. It is intended to facilitate communication and promote
common understanding.
The scope of this document covers the whole field of nuclear reactors at a broad surface level.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1 General terms related to nuclear reactors
3.1.1
nuclear fission
process by which a nucleus undergoes a partition in two, infrequently in three, main fission fragments,
releasing energy
Note 1 to entry: There are two types of nuclear fission: “spontaneous” and “induced” ones.
Note 2 to entry: The nucleus usually has a high mass number A, together with an intermediate or low average-
binding-energy-per-nucleon; hence, an inherent instability exists, and the fission fragments are usually highly
unstable.
Note 3 to entry: According to their capability for undergoing fission, a nucleus and its associated nuclide can be
qualified as fissionable or eventually fissile.
3.1.1.1
induced nuclear fission
nuclear fission (3.1.1) initiated by a nucleus when an external colliding particle is absorbed
Note 1 to entry: The absorption of the external colliding particle, usually a neutron, generates a strong increase
in the compound nucleus internal energy and, hence, increases the compound nucleus instability, favouring a
large energy release by means of a nucleus partition.
3.1.1.2
spontaneous nuclear fission
nuclear fission (3.1.1) produced in a nucleus, having an inherent instability, that develops itself in a
purely stochastic way and without intervention of any external colliding particle
3.1.2
fissionable nuclide
nuclide capable of undergoing fission by interaction with a neutron of some energy
Note 1 to entry: The definition may be restricted to significant capability, e.g. to a nuclide that is capable of
supporting a self-sustaining nuclear chain reaction (3.1.9).
3.1.3
prompt fission neutron
neutron released out from a fission fragment in a stochastic way, with high kinetic-energy just following
initiation of a nuclear fission (3.1.1) process
Note 1 to entry: The number of prompt neutrons released per fission, is stochastic as indicated, with an average
value in the range 2,5 to 3 for most of concerned nuclides.
Note 2 to entry: Prompt fission neutron kinetic-energies form a continuum, between 0 and around 10 MeV, for a
population of prompt fission neutrons released, with an average value usually close to 2 MeV.
3.1.4
prompt fission radiation
gamma and/or beta radiations released in a stochastic way, out from each decaying fission fragment
just following initiation of a nuclear fission (3.1.1)
Note 1 to entry: These gamma and beta radiations are released in cascades, reflecting the high internal energy
level of most of fission fragments just after fission initiation.
3.1.5
fission product
nuclide produced from nuclear fission (3.1.1) or from subsequent radioactive decay of such a nuclide
[SOURCE: ISO 12749-3:2015, 3.1.5]
3.1.5.1
fast neutron
neutron with kinetic energy greater than its surroundings when released during fission
3.1.5.1.1
delayed fission neutron
neutron emitted in few particular fission product (3.1.5) decays, typically with half-lives roughly in the
range 0,1 s to 1 min, following initiation of a nuclear fission (3.1.1)
Note 1 to entry: Such decay occurs between two energy levels of a fission product-namely precursor-favouring
a neutron release, hence, the emitted neutron will have a quite defined kinetic-energy at its release, typically
below 1 MeV.
Note 2 to entry: In a fission neutron population, since delayed neutrons have kinetic evolutions dictated by those
rather long periods, as compared to the extremely fast evolutions of prompt neutrons, the first ones provide an
important contribution to the kinetic control of that neutron population.
3.1.5.1.1.1
thermal neutron
neutron that has, by collision with other particles, reached an energy state equal to that of its
surroundings
Note 1 to entry: on the order of 0,025 eV (electron volts).
[SOURCE: United States Nuclear Regulatory Commission Glossary (Retrieved: 8 August 2017) https://
www .nrc .gov/ reading -rm/ basic -ref/ glossary .html], modified.
2 © ISO 2018 – All rights reserved
3.1.5.2
delayed fission radiation
gamma and/or beta, in certain cases also alpha radiations released in a stochastic way, from a
radioactive fission product (3.1.5)
Note 1 to entry: Every possible fission product decay has extremely diverse half-lives, covering the range around
0.1 s up to more than a billion years.
Note 2 to entry: These “delayed” released gamma, beta and alpha radiations, after interactions with neighbouring
atoms, are mainly absorbed by the surrounding materials and then finally converted into heat: they are the
source of what is designated as decay-power or decay-heat or residual-heat.
3.1.6
fissile nuclide
nuclide capable of undergoing fission by interaction with neutrons
[SOURCE: ISO 12749-3:2015, 3.1.2]
3.1.7
fertile nuclide
nuclide that after absorbing a neutron becomes a fissile nuclide (3.1.6)
238 239 240
Note 1 to entry: In practice, the main fertile nuclides are: U (producing the fissile Pu), Pu (producing the
241 232 233
fissile Pu) and Th (producing the fissile U), in all cases after the absorption of one neutron and the fast
emission of some gamma photons.
3.1.8
fission energy
energy released in the fission process, which is primarily in the form of the kinetic energy of the fission
fragments
3.1.9
nuclear chain reaction
successive generations of induced nuclear fissions (3.1.1.1) by neutrons, these mainly
released, in turn, in previous fissions in fissionable nuclides (3.1.2)
Note 1 to entry: The free neutron population in a system is multiplied by fissions releasing several neutrons
per fission, compensating partially or totally, or exceeding the total neutron losses by capture and leakage
from the system.
Note 2 to entry: A nuclear chain reaction can be initiated by a pre-existent small neutron population (like that
resulting from photo-neutrons in particular materials for this purpose), or by neutrons released by spontaneous
fissions, or by a specific “neutron source” emitting neutrons.
3.1.9.1
controlled nuclear chain reaction
chain reaction for which there are adequate and reliable physical means or systems to safely govern
the value of the effective neutron multiplication factor (3.1.11) at any time, and under all possible
circumstances
Note 1 to entry: The just mentioned physical means and/or systems form the available reactivity (3.1.12) control
elements, which are usually parts of the reactor regulation system (3.7.2.1.2). Other systems and elements can
assist this one for safety aspects.
Note 2 to entry: A nuclear chain reaction (3.1.9) is controlled by taking advantage of the delayed fraction of fission
neutrons. This fraction depends on the properties of the fissionable nuclides (3.1.2) in the system. An uncontrolled
chain reaction may be non-destructive due to negative contributions from the initial energy increase. The
delayed neutrons allow more time for such negative feedback.
3.1.10
neutron multiplicative configuration
geometrical disposition of materials, one or more containing fissionable nuclides (3.1.2), the whole
configuration being capable of maintaining a multiplicative chain reaction of neutron-induced nuclear
fissions (3.1.1.1)
3.1.11
effective neutron multiplication factor
k
eff
ratio between current to previous generation of neutron population in
multiplicative medium
Note 1 to entry: The total number of produced neutrons per unit time includes all prompt and delayed neutrons
released in fissions; while, the total number of lost neutrons are the sum of all absorbed neutrons (in fission and
capture reactions), plus all leaking neutrons escaping.
Note 2 to entry: There are three possible circumstances:
a) k > 1: fission power increases in time;
eff
b) k = 1: fission power remains constant in time;
eff
c) k < 1: fission power decreases in time.
eff
When k > 1, system is called supercritical; when k = 1, system is called critical; and finally when k < 1, then
eff eff eff
system is called subcritical.
3.1.12
reactivity
ρ
measure of the deviation from criticality of a nuclear chain reacting medium:
ρ = 1 − 1/k
eff
where k is the ratio between the number of fissions in two succeeding generations (later to earlier) of
eff
the chain reaction
Note 1 to entry: A measure of the reactivity is typically defined such that a positive value corresponds to a
supercritical state and a negative value corresponds to a subcritical state.
[SOURCE: INTERNATIONAL ATOMIC ENERGY AGENCY. “IAEA Safety Glossary: Terminology used
in nuclear safety and radiation protection. 2016 Edition”. IAEA, Vienna, 2016. (Retrieved: 11 August
2016). p. 219, http:// www -ns .iaea .org/ downloads/ standards/ glossary/ iaea -safety -glossary -rev2016
[11]
.pdf , modified — Addition at the beginning of the definition of the wording stated in one comment.]
3.1.13
poison
substance used to reduce reactivity (3.1.12), typically in a reactor core (3.1.23.1), by virtue of its high
neutron absorption cross-section
[SOURCE: INTERNATIONAL ATOMIC ENERGY AGENCY. “IAEA Safety Glossary: Terminology used in
nuclear safety and radiation protection. 2016 Edition”. IAEA, Vienna, 2016. (Retrieved: 11 August 2016).
p. 219, http:// www -ns .iaea .org/ downloads/ standards/ glossary/ iaea -safety -glossary -rev2016 .pdf]
3.1.14
nuclear reactor kinetics
time evolution of the neutron population in a reactor core (3.1.23.1)
4 © ISO 2018 – All rights reserved
3.1.15
nuclear criticality
state of a nuclear chain reacting system when the chain reaction is just self-sustaining
[SOURCE: ISO 12749-3:2015, 3.1.1.4]
3.1.16
nuclear chain reaction extinction
action that terminates a nuclear chain reaction (3.1.9)
Note 1 to entry: Termination is caused by an operator-decided and manually executed action, or by automatic
signal trips, normally provoking in both cases a significant insertion of neutron absorbers inside the reactor core
(3.1.23.1).
3.1.17
nuclear reactor installation
set of a nuclear reactor (3.1.22), its authorities, operation (3.9.1)-maintenance (3.9.12), administrative-
support staff, associated and dedicated plants, buildings, systems and all surrounding infra-structure
and services, up to the installation perimeter fences
Note 1 to entry: Frequently, the concept is oriented to provide some specific products, like electric energy,
radioactive isotopes, irradiation services, infra-structure for research and development.
Note 2 to entry: Usually, reactor systems, dedicated plants and associated infra-structure are very specially
designed according to the reactor purposes.
Note 3 to entry: The most important buildings in a nuclear reactor installation are: the containment (3.7.5)
building, that houses the nuclear reactor (3.1.22) and the primary coolant (3.1.23.4) system equipment, the
turbine building (only present in nuclear power plants (3.2.5) or nuclear reactors coupled to a turbine-generator)
that houses the turbine generator (3.4.4), the auxiliary building that houses support equipment and sometimes
emergency equipment, the diesel generator building, that houses the diesel generator and the fuel building,
where the spent fuel is stored.
3.1.18
radiation protection organization
installation staff sector that has radiation protection functions and duties both regarding site personnel,
visitors and the public
Note 1 to entry: The radiation protection organization performs its duties with the aid of a number of check-
stations, a large and well distributed gamma or other radiation detector network for radiation surveillance,
appropriate radiation protection laboratory, personal dose management system, and implements the process of
optimization of protection for plant personnel.
3.1.19
controlled area
defined area in which specific protection measures and safety provisions are or could be required for
controlling exposures or preventing the spread of contamination in normal working conditions, and
preventing or limiting the extent of potential exposures
[SOURCE: INTERNATIONAL ATOMIC ENERGY AGENCY. “IAEA Safety Glossary: Terminology used in
nuclear safety and radiation protection. 2016 Edition”. IAEA, Vienna, 2016. (Retrieved: 28 November,
2016). p. 219, http:// www -ns .iaea .org/ downloads/ standards/ glossary/ iaea -safety -glossary -rev2016 .pdf]
3.1.20
radiation shield
material interposed between a source of radiation and persons, or equipment or other objects, in order
to attenuate the radiation
Note 1 to entry: The radiation shield is designed either as fixed or movable installation structures (3.7.1) or
elements, and placed between large plant radioactive inventories and the authorized personnel working in a
controlled area (3.1.19), or the off-site public and the environment, or some sensitive equipment.
3.1.21
radiation monitoring
measurement and surveillance of the main radiation types, neutrons, gamma and
beta, and their amounts
Note 1 to entry: The main radiation types are neutrons, gamma and beta rays; sometimes also their energy
distribution is monitored.
Note 2 to entry: The radiation monitoring is performed around and near the nuclear reactor (3.1.22) (especially
neutrons), as well as in all controlled areas (3.1.19) and other locations inside and even beyond plant borders (by
means of an extended detector network).
3.1.22
nuclear reactor
special device having an inventory of nuclear fuel material containing fissionable nuclides (3.1.2) and
often neutron moderating, neutron absorbing and cooling materials, all of them geometrically arranged
in a particular neutron multiplicative configuration (3.1.10) designed and built for having the capability
of initiating, maintaining and extinguishing a controlled, self-sustaining nuclear fission (3.1.1) chain
reaction, under adequate safety conditions
3.1.23
nuclear island
part of the nuclear power plant (3.2.5) that consists of the containment (3.7.5), auxiliary and fuel building
[SOURCE: IAEA NUCLEAR ENERGY SERIES, No. NP-T-2.5. Construction technology for nuclear power
plants – Vienna: International Atomic Energy Agency, 2011]
3.1.23.1
reactor core
part of a nuclear reactor (3.1.22), where the fissionable nuclides (3.1.2) sustaining the fission chain
are located
Note 1 to entry: In most cases, moderator (3.1.23.1.2) and coolant are also included in the reactor core (3.1.23.1).
3.1.23.1.1
core reflector
material placed around the reactor core (3.1.23.1), totally or partially enveloping it, in order to scatter
most of leaking neutrons back into the core, improving neutron economy
Note 1 to entry: Since most of nuclear reactors (3.1.22), have a preferred vertical cylinder geometry, they have 3
different reflectors: upper axial, lower axial and radial.
Note 2 to entry: The most used materials as reflectors in front of:
a) slow-or thermal-neutrons (3.1.5.1.1.1), are: H O (light or ordinary water), D O (heavy water), Be (beryllium),
2 2
C (carbon, graphite);
b) fast-neutrons (3.1.5.1), are: SS (stainless steel).
3.1.23.1.2
moderator
material capable of slowing down fast neutrons (3.1.5.1) and, in this process, absorbing a relatively low
amount of neutrons
EXAMPLE The most preferred moderators have been up to now:
— H (A = 1, or ordinary H);
— H (A = 2, or deuterium);
— C (A = 12, or graphite).
The two first are respectively employed as:
6 © ISO 2018 – All rights reserved
a) “ordinary or light water”, using the symbols “LW or H O”;
b) “heavy water”, using the symbols “HW or D O”.
3.1.23.2
reactor internals
any of the different structural parts inside the nuclear reactor (3.1.22), covering various functions,
either as part of the nuclear reactor itself or as part of reactor-associated systems
Note 1 to entry: Some of these functions are:
a) to support and provide adequate alignment to fuel assemblies (FAs), the reactor core (3.1.23.1) as a whole
and one or more core reflectors (3.1.23.1.1);
b) to direct inlet and outlet primary coolant (3.1.23.4) flow and its distribution among all reactor heat sources,
similar structures (3.7.1) for other fluids inside the reactor (like liquid moderator (3.1.23.1.2) and/or
reflectors);
c) to provide in-core locations and protection for in-core instrumentation (3.7.6.1.1) and for elements and
components (3.7.3) related to reactivity (3.1.12)/power control and safety systems (3.7.2.7) for fast reactor
(3.2.3.1) extinction.
3.1.23.3
reactor vessel
enveloping structure (3.7.1) for harboring all elements of a nuclear reactor (3.1.22)
Note 1 to entry: Main elements usually allocated inside the reactor vessel, are as follows:
a) the reactor core (3.1.23.1) and its reflectors;
b) all structures (3.7.1) and tubes of reactor internals (3.1.23.2).
Note 2 to entry: The reactor vessel additionally serves as confining structure for the primary coolant (3.1.23.4).
Moreover, in most cases this vessel is also part of a high-pressure boundary for the primary coolant, mainly
encompassing the reactor core (3.1.23.1) and the primary heat transport system (3.7.2.5); in these cases, it is
called “reactor pressure vessel or RPV”.
3.1.23.4
primary coolant
fluid circulating through the reactor core (3.1.23.1), in order to cool all fuel assemblies, receiving all
their fission power
Note 1 to entry: The primary coolant normally removes instantaneous fission and decay powers generated in
the reactor core (3.1.23.1) and is able for removing abnormal excessive heat. It circulates within the primary
heat transport system (3.7.2.5), and transfers all reactor thermal power to a final heat sink. Such thermal power
transfer can be either “direct”, or more usually “indirect”, by means of chained circuits circulating appropriate
fluids, between the nuclear reactor (3.1.22) and that final heat sink.
Note 2 to entry: The primary or main coolant is always a fluid and then it can be, either: a liquid in single phase,
or a boiling two-phase fluid, or a gas. The most widely employed are:
a) liquid-state ordinary or light water (H O) at atmospheric or high pressure;
b) liquid-state heavy water (D O) at atmospheric or high pressure;
c) boiling H O at high pressure;
d) CO or He gases.
Note 3 to entry: The final heat sink usually can be either: the atmosphere, a river, a lake, a sea or an ocean. In a
nuclear power plant (3.2.5) one of such sinks shares its function with a turbine-generator (3.4.4) set, where part of
the total thermal power is converted to kinetic power and immediately to electric power.
3.2 Terms related to nuclear reactors types
3.2.1
nuclear reactor
(See 3.1.22)
3.2.1.1
power reactor
nuclear reactor (3.1.22) conceived to produce electrical power
3.2.1.2
multiple-purpose reactor
nuclear reactor (3.1.22) conceived for fulfilling several main purposes together, providing different
services, except electric energy supply
EXAMPLE Reactors that produce radioisotopes, provide irradiation boxes and positions, irradiated material
studies, neutron beams for research and development work, personnel training, etc.
3.2.1.3
special-purpose reactor
nuclear reactor (3.1.22) conceived with a particular target
EXAMPLE Prototype reactors (3.6.1.3), demonstration reactors (3.6.1.2), naval propulsion reactors,
desalination reactors (3.6.1.5), material testing reactors (3.5.1.5), hydrogen production reactors (3.5.1.3).
3.2.2.1
breeder reactor
nuclear reactor (3.1.22) conceived for producing more fissile nuclides (3.1.6) than it uses, being the
conversion ratio greater than one
3.2.2.2
converter reactor
nuclear reactor (3.1.22) conceived for producing less fissile nuclides (3.1.6) than it uses, being the
conversion ratio smaller than one
3.2.2.3
transmutation reactor
nuclear reactor (3.1.22) conceived for the purpose of eliminating partially the radioactive wastes
contained in other reactors spent nuclear fuel
3.2.3.1
fast reactor
nuclear reactor (3.1.22) designed and operated mainly using a predominantly fast neutron (3.1.5.1)
energy spectrum
Note 1 to entry: The main contribution to fission power typically from neutrons with energies above 100 keV.
3.2.3.2
thermal reactor
nuclear reactor (3.1.22) designed and operated mainly using a predominantly thermal neutron
(3.1.5.1.1.1) energy spectrumNote 1 to entry: The main contribution to fission power typically from
neutrons with energies below 1 eV.
3.2.4.1
gas-cooled reactor
GCR
nuclear reactor (3.1.22) that uses gas as primary coolant (3.1.23.4)
Note 1 to entry: A gas cooled reactor can be either a thermal gas-cooled reactor or a gas cooled fast reactor
(3.2.3.1).
Note 2 to entry: The gas is usually helium (He) or carbon dioxide (CO ).
8 © ISO 2018 – All rights reserved
3.2.4.2
light water reactor
LWR
thermal nuclear reactor (3.1.22) cooled and moderated by light water
3.2.4.2.1
boiling water reactor
BWR
nuclear reactor (3.1.22) with water as a coolant and as a moderator (3.1.23.1.2), boiling in the core
Note 1 to entry: In a boiling water reactor the generated heat is removed from the core by evaporation.
[SOURCE: Koelzer, Winfried. “Glossary of Nuclear Terms”. Karlsruher Institut für Technologie,
Karlsruhe, 2013. ISBN 3-923704-32-1. (Retrieved: 26 aug 2016). p. 180, http:// www .euronuclear
.org/ info/ encyclopedia/ pdf/ Nuclear _Glossary -%202013 -02 -13 .pdf and GOST 23082-1978, modified.]
3.2.4.2.2
pressurized water reactor
PWR
power nuclear reactor (3.1.22) in which the heat is dissipated from the core using highly pressurized water
[SOURCE: Koelzer, Winfried. “Glossary of Nuclear Terms”. Karlsruher Institut für Technologie,
Karlsruhe, 2013. ISBN 3-923704-32-1. (Retrieved: 26 aug 2016). 180p. http:// www .euronuclear
.org/ info/ encyclopedia/ pdf/ Nuclear _Glossary -202013 -02 -13 .pdf]
Note 1 to entry: The coolant in form of pressurized water serves also a moderator (3.1.23.1.2).
3.2.4.3
heavy water reactor
nuclear reactor (3.1.22) cooled and/or moderated with heavy water (D O)
[SOURCE: Koelzer, Winfried. “Glossary of Nuclear Terms”. Karlsruher Institut für Technologie,
Karlsruhe, 2013. ISBN 3-923704-32-1. (Retrieved: 26 aug 2016). 180p. http:// www .euronuclear
.org/ info/ encyclopedia/ pdf/ Nuclear _Glossary -202013 -02 -13 .pdf]
3.2.4.3.1
pressurized heavy water reactor
PHWR
thermal nuclear reactor (3.1.22) cooled and moderated by heavy water (D O), having a pressurized D O
2 2
coolant to be kept permanently in the liquid state
3.2.4.4
liquid metal reactor
liquid metal fast reactor
LMFR
fast nuclear reactor (3.1.22) using as coolant a liquid metal, like sodium, lead, or some alloy
3.2.4.4.1
sodium fast reactor
fast nuclear reactor (3.1.22) cooled by liquid sodium
Note 1 to entry: For the fact that sodium becomes active in the presence of a neutron field, these reactors may
possess an intermediate heat transport system.
Note 2 to entry: The reactor is commonly fueled with mixed plutonium-uranium oxides (MOX), with an
232 233
enrichment in the fissile isotope of the order of 15 %; although Th- U based fuels have also been used.
3.2.4.4.2
lead fast reactor
fast nuclear reactor (3.1.22) cooled by liquid lead
3.2.4.5
molten salt reactor
nuclear reactor (3.1.22) where the fuel is a molten salt mixed with a carrier molten salt that acts as
primary coolant (3.1.23.4)
Note 1 to entry: Molten salt is typically uranium, plutonium and thorium fluorides. Carrier molten salt is typically
lithium fluorides.
3.2.5
nuclear power plant
NPP
nuclear reactor installation (3.1.17) that produces electrical and/or heat energy
Note 1 to entry: Nuclear power plant is a nuclear reactor (3.1.22) or reactors together with all structures (3.7.1),
systems and components (3.7.3) necessary for safety and for the production of power, i.e. heat or electricity.
3.2.6
nuclear power plant technology generation
NPP technology generation
each of the main waves of new conceptual designs within historic nuclear power plant (3.2.5) technology
evolution, since generation I (3.2.6.1) up to generation IV (3.2.6.5)
3.2.6.1
generation I
gen I
commercial power reactor (3.2.1.1) that started civilian nuclear power programs and was constructed
during the 1950 and 1960 decades
Note 1 to entry: Almost all these reactors have already been closed down.
3.2.6.2
generation II
gen II
commercial power reactors (3.2.1.1) mostly designed and constructed during the 1970 and 1980
decades, to be reliable from a safety point of view and economically attractive for a typical operational
lifetime of 30 years to 40 years
Note 1 to entry: Many of these reactors have implemented life extension programs and received approval from
their nuclear regulator (3.3.9) to extend their operating lifetimes (3.9.8) beyond the original license (3.3.13) limits.
3.2.6.3
generation III
gen III
generation II (3.2.6.2) reactor including evolutionary, state-of-the-art design improvements
Note 1 to entry: These improvements are manifested in the areas of fuel technology, thermal efficiency,
modularized construction, safety systems (3.7.2.7) and standardized design. Improvements in Gen III reactor
technology have aimed at a longer operational life, typically 60 years of operation (3.9.1) and thus at being
economically more competitive.
3.2.6.4
generation III+
gen III+
either an evolutionary development of generation III (3.2.6.3) reactors or an innovative one, offering
improvements mainly in the field of safety over Gen III reactor designs
Note 1 to entry: Safety improvements comprise: containment (3.7.5) improvements, radioactive inventory release
minimization, emphasis on passive systems (use of gravity potential energy rather than electrical energy, very
high pressure differences, springs, natural convection).
10 © ISO 2018 – All rights reserved
3.2.6.5
generation IV
gen IV
novel design concepts of reactors that are expected to be built after year 2030 and to outpace the
performance of the Gen III (3.2.6.3) and Gen III+ (3.2.6.4) reactor
3.3 Terms related to nuclear projects
3.3.1
nuclear project
unique process, consisting of a set of coordinated and controlled activities with start and finish dates,
undertaken to achieve an objective conforming to specific requirements, including the constraints of
time, cost and resources related to nuclear reactor installations (3.1.17)
[SOURCE: ISO 9000:2015, 3.4.2, modified — The wording “related to nuclear reactor installations” has
been added.]
3.3.2
project stage
each part in which the execution of a whole nuclear project (3.3.1) can be divided
3.3.3
engineering stage
each of the relevant parts in the engineering development for a system or civil work, or for a set of
systems or civil structures (3.7.1) or buildings, or for the whole plant
3.3.4
project management area
activity space that constitutes the project management
Note 1 to entry: Such constituents usually are licensing, administration, commercial and contracts, legal,
financing, project command and follow-up, quality management, design and engineering, procurement,
construction, erection and plant commissioning.
3.3.5
design basis
DB
range of conditions and events (3.8.2) taken explicitly into account in the design of structures (3.7.1),
systems and components (3.7.3) and equipment of a facility, according to established criteria, such that
the facility can withstand them without exceeding authorized limits
[SOURCE: INTERNATIONAL ATOMIC ENERGY AGENCY. “IAEA Safety Glossary: Terminology used in
nuclear safety and radiation protection. 2016 Edition”. IAEA, Vienna, 2016. (Retrieved: 11 August 2016).
p. 219, http:// www -ns .iaea .org/ downloads/ standards/ glossary/ iaea -safety -glossary -rev2016 .pdf]
3.3.6
equipment specification
technical document prepared by a high-level contractor (3.3.17) to specify technical and quality
assurance requirements to the subcontractors
[SOURCE: ISO 18229:2018, 3.6, modified — Notes were deleted and the terminology slightly modified.]
3.3.7
design life
period of time during which a facility or component (3.7.3) is expected to perform according to the
technical specifications to which it was produced
[SOURCE: INTERNATIONAL ATOMIC ENERGY AGENCY. “IAEA Safety Glossary: Terminology used in
nuclear safety and radiation protection. 2016 Edition”. IAEA, Vienna, 2016. (Retrieved: 11 August 2016).
p. 219, http:// www -ns .iaea .org/ downloads/ standards/ glossary/ iaea -safety -glossary -rev2016 .pdf]
3.3.8
plant lifetime limiting factor
specific physical or chemical process producing a degradation or modification on some component
(3.7.3) per second or equipment of the nuclear reactor installation (3.1.17)
3.3.9
nuclear regulator
nuclear regulatory body
body or system of bodies designated by the government as having legal authority for conducting
the regulatory process and thereby regulating the safety of nuclear reactor installations (3.1.17) by
establishing safety requirements and conducting oversight regarding implementation
3.3.10
responsible entity
formal entity acting at any moment in front of the nuclear regulator (3.3.9), as representative of a nuclear
project (3.3.1) under execution, or of an existing nuclear reactor installation (3.1.17)
Note 1 to entry: In the first case, a nuclear project (3.3.1), the responsible entity is normally the project
management. In the second case, an existing nuclear reactor installation (3.1.17), the responsible entity is
normally the operation (3.9.1) organization.
3.3.11
licensee
holder of a current authorization granted by the nuclear regulator (3.3.9) to an organization that has the
responsibility for the siting, design, construction, commissioning, operation (3.9.1) or decommissioning
of a nuclear installation
3.3.12
licensing basis
set of regulatory requirements applicable to a nuclear installation
Note 1 to entry: The licensing basis, in addition to a set of regulatory requirements, may also include agreements
and commitments made between the nuclear regulator (3.3.9) and the licensee (3.3.11).
[SOURCE: INTERNATIONAL ATOMIC ENERGY AGENCY. “IAEA Safety Glossary: Terminology used in
nuclear safety and radiation protection. 2016 Edition”. IAEA, Vienna, 2016. (Retrieved: 11 August 2016).
p. 219, http:// www -ns .iaea .org/ downloads/ standards/ glossary/ iaea -safety -glossary -rev2016 .pdf.]
3.3.13
license
legal document issued by the nuclear regulator (3.3.9) granting authorization to perform specified
activities relating to a facility or activity
[SOURCE: INTERNATIONAL ATOMIC ENERGY AGENCY. “IAEA Safety Glossary: Terminology used in
nuclear safety and radiation protection. 2016 Edition”. IAEA, Vienna, 2016. (Retrieved: 11 August 2016).
p. 219, http:// www -ns .iaea .org/ downloads/ standards/ glossary/ iaea -safety -glossary -rev2016 .pdf]
3.3.14
mandatory documentation
set of all most relevant technical documentation associated to the installation, established by the
nuclear regulator (3.3.9), to be fulfilled by the responsible entity (3.3.10), covering the whole area of
nuclear safety (3.8.1), in order to obtain a nuclear license (3.3.13)
3.3.15
third-party inspection body
organization, company or body, that performs inspections on any granted-by-contract service or
supplies required by standards and being independent of the manufacturer (3.3.18), contracting party,
owner or user
[SOURCE: ISO 18229:2018, 3.19, modified — Wording slightly changed.]
12 © ISO 2018 – All rights reserved
3.3.16
prime contractor
legal entity that receives a major contract from the owner or project management for providing all main
components (3.7.3) or a full provision of either the nuclear island (3.1.23) or the balance of plant (3.4.1.3)
[SOURCE: ISO 18229:2018, 3.11, modified — Wording slightly changed.]
3.3.17
contractor
supplier in a contractual situation
[SOURCE: ISO 10795:2011, 1.61]
3.3.17.1
subcontractor
any contractor (3.3.17), except for a prime contractor (3.3.16), providing supplies and/or services
through a contract passed with other project contractor or eventually with the project management for
specific items
[SOURCE: ISO 18229:2018, 3.15, modified — Note 1 to entry deleted.]
3.3.18
manufacturer
legal entity responsible for the final design, manufacturing, engineering and the
construction of any component (3.7.3) of the nuclear reactor installation (3.1.17)
[SOURCE: ISO 18229:2018, 3.9, modified — The field was added and “nuclear reactor” was replaced by
“nuclear reactor installation”.]
3.4 Terms related to nuclear power plants
3.4.1
nuclear power plant
NPP
(See 3.2.5)
3.4.1.1
single-unit nuclear power plant
single-unit NPP
nuclear power plant (3.2.5) having a single electric production line
3.4.1.2
multiple-unit nuclear power plant
multiple-unit NPP
nuclear power plant (3.2.5) having on a common site, two or more electric production lines
Note 1 to entry: The nuclear reactors (3.1.22) and the electric production lines can be either almost identical
or different between them, though usually sharing various support or auxiliary installations, systems and/or
supplies.
3.4.1.3
balance of plant
BOP
part of the nuclear power plant (3.2.5) that consists of a set of a main turbine generator (3.4.4) unit and
all associated systems, structures (3.7.1) and components (3.7.3) necessary to produce electric power
3.4.1.3.1
gas turbine balance of plant
gas turbine BOP
balance of plant (3.4.1.3) type that produces electric energy associated to a nuclear high temperature gas
supply system (3.4.6)
3.4.1.3.2
steam turbine balance of plant
steam turbine BOP
balance of plant (3.4.1.3) type that produces electric energy associated to a nuclear steam supply
system (3.4.5)
3.4.1.4
nuclear island
(See 3.1.23)
3.4.1.5
turbine island
part of the nuclear power plant (3.2.5)that consists of the turbine building
[SOURCE: IAEA NUCLEAR ENERGY SERIES, No. NP-T-2.5. Construction technology for nuclear power
plants – Vienna: International Atomic Energy Agency, 2011]
3.4.2
reference unit power
maximum (electrical) power that could be maintained continuously throughout a prolonged period of
operation (3.9.1)
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