Glossary of Terms in PRIS Reports

A

Advanced Gas-cooled Reactor

AGR	An advanced gas-cooled reactor (AGR) is a type of nuclear reactor. It is a second generation of British gas-cooled reactor, that uses graphite as the neutron moderator and carbon dioxide as a coolant.

B

Boiling Water Reactor

BWR	A Boiling Water Reactor (BWR) is a light-water-cooled and light-water-moderated reactor. In a BWR, the reactor core heats water directly, causing it to boil and produce steam, which drives a turbine connected to an electrical generator.

C

Cancelled Construction

	When the construction of a reactor was cancelled before completion.

Cancelled Plan

	The planned reactor project was cancelled before construction began.

Capacity Factor

CF	Capacity factor is the ratio of the actual energy output of an electricity-generating device divided by the energy output that would be produced if it operated at its rated power output (Reference Unit Power) for the entire year. It is generally expressed as percentage. In PRIS a term Load Factor...
		Full Description Close Capacity Factor Capacity factor is the ratio of the actual energy output of an electricity-generating device divided by the energy output that would be produced if it operated at its rated power output (Reference Unit Power) for the entire year. It is generally expressed as percentage. In PRIS a term Load Factor (LF) is instead of CF.

Commercial Operation

	In PRIS, commercial operation of a reactor begins on the Commercial Date. The period from the first grid connection to the Commercial Date is called 'trial operation'. Performance Indicators reported by PRIS are calculated for the commercial operation period, while electricity production is...
		Full Description Close Commercial Operation In PRIS, commercial operation of a reactor begins on the Commercial Date. The period from the first grid connection to the Commercial Date is called 'trial operation'. Performance Indicators reported by PRIS are calculated for the commercial operation period, while electricity production is reported with the first grid connection.

Commercial Operation Start

	The date when the plant is handed over by the contractors to the owner and declared to have officially entered commercial operation.

Construction Start Date

	The date when the first major placement of concrete for the reactor building base mat begins. For floating nuclear power plants, the construction start date is the beginning of platform construction. From this date, the reactor is considered to be under construction.

Country Nuclear Power Profiles

CNPP	The CNPP compile background information on the status and development of nuclear power programmes. They include organizational and industrial aspects of nuclear power programmes and provide information about the relevant legislative, regulatory, and international frameworks for each country.

D

Decommissioning Completed

	This status indicates that the reactor site has been released from regulatory control. The Decommissioning End Date is required for this status. This status was newly added in DAVA.

Desalination

	Desalination is the artificial process by which salt water (generally sea water) is converted to fresh water. More generally, desalination is the removal of salts and minerals from a substance.

Design Net Capacity

	The original Design Net Capacity (electrical power) is the electrical output in the original unit design after deducting the unit's own electrical consumption, regardless of whether this value has been routinely achieved during operation. It does not reflect subsequent power uprates or deratings.

District Heating

	District heating is the heat provided to space heaters installed at houses, buildings and facilities outside the power plant for warming the living environment. In some cases supply of hot water for living is combined with this system. Enter the thermal energy provided during the reference period...
		Full Description Close District Heating District heating is the heat provided to space heaters installed at houses, buildings and facilities outside the power plant for warming the living environment. In some cases supply of hot water for living is combined with this system. Enter the thermal energy provided during the reference period for district heating delivered in the form of heat (steam or hot water) measured as the difference between the plant feed (outlet) and return (inlet) headers. If it is difficult to provide individual data for (PDH), the total delivery data for (PDH+PPH) are acceptable. If monthly data are difficult to provide, the annual total data are acceptable.

E

Electricity Supplied

	Net electrical energy produced during the reference period as measured at the unit outlet terminals, i.e. after deducting the electrical energy taken by unit auxiliaries and the losses in transformers that are considered integral parts of the unit. Also called Net Energy Generated. It is measured...
		Full Description Close Electricity Supplied Net electrical energy produced during the reference period as measured at the unit outlet terminals, i.e. after deducting the electrical energy taken by unit auxiliaries and the losses in transformers that are considered integral parts of the unit. Also called Net Energy Generated. It is measured in MWh.

Energy Availability Factor

EAF	The energy availability factor over a specified period, is the ratio of the energy that the available capacity could have produced during this period, to the energy that the reference unit power could have produced during the same period. The energy availability factor is determined for each...
	More info: http://www-pub.iaea.org/MTCD/Publications/PDF/TRS428_web.pdf	Full Description Close Energy Availability Factor The energy availability factor over a specified period, is the ratio of the energy that the available capacity could have produced during this period, to the energy that the reference unit power could have produced during the same period. The energy availability factor is determined for each period as shown below: EAF (%) = (REG - PEL - UEL - XEL) / REG x 100 Where: - REG = reference energy generation for the period - PEL = total planned energy losses - UEL = total unplanned energy loss - XEL = total external energy losses (beyond the plant management control)

Energy Unavailability Factor

EUF	The energy unavailability factor for a specific period is calculated as: EUF = 100 - EAF over a specific time period Where: EAF = energy availability factor

Extension of Planned Loss

EPL	EPL is the total energy loss resulting from unplanned extensions of planned outages during a one-year period.

External Energy Loss

XEL	XEL is the total energy loss resulting from external factors beyond the control of plant management.

External Unavailabilty Factor

XUF	The External Unavailability Factor is the ratio of the energy that could have been produced during a specific period but was lost due to external constraints (such as grid restrictions or environmental conditions), compared to the total maximum energy the plant could have generated running at full...
		Full Description Close External Unavailabilty Factor The External Unavailability Factor is the ratio of the energy that could have been produced during a specific period but was lost due to external constraints (such as grid restrictions or environmental conditions), compared to the total maximum energy the plant could have generated running at full capacity during that same period. It is a performance indicator which can be calculated in the DAVA system.

F

Fast Breeder Reactor

FBR	These reactors use fast neutrons to sustain fission in their fuel. They do not use a neutron moderator and typically employ coolants with low neutron-moderating properties.
	More info: http://www-pub.iaea.org/MTCD/Publications/PDF/te_1531_web.pdf

First Criticality Date

	The date when the reactor is made critical for the first time.

Forced Energy Loss

FEL	FEL is the amount of energy lost due to unplanned forced outages during a one-year period.

Forced Loss Rate

FLR	Operating period forced loss rate is defined as the ratio of the unplanned energy losses during a given period of time, considering only the operating period, to the reference energy generation minus energy losses corresponding to planned outages and their possible unplanned extensions, during the...
	More info: http://www-pub.iaea.org/MTCD/Publications/PDF/TRS428_web.pdf	Full Description Close Forced Loss Rate Operating period forced loss rate is defined as the ratio of the unplanned energy losses during a given period of time, considering only the operating period, to the reference energy generation minus energy losses corresponding to planned outages and their possible unplanned extensions, during the same period, expressed as a percentage. Unplanned forced energy loss during the operating period is energy that was not produced during that period because of unplanned shutdowns, or unplanned load reductions due to causes under plant management control. FLR (%) =FEL/( REG - (PEL+EPL)) x100 % Where: - FEL = amount of energy lost due to unplanned forced outages during a one-year operating period - REG = reference energy generation for one year - PEL = planned energy losses for one year - EPL = unplanned extensions of planned outages energy loss for a one-year period This indicator reflects the effectiveness of plant programs and practices in maintaining systems available for safe electricity generation when the plant is expected to be at the grid dispatcher's disposal.

G

Gas-Cooled Reactor

GCR	A gas-cooled reactor is a nuclear reactor that uses graphite as a neutron moderator and carbon dioxide as a coolant. In some designs, helium is used instead of carbon dioxide.

Gigawatt

GW	The gigawatt is equal to one billion (10^9) watts or 1 gigawatt = 1000 megawatts. In the electric power industry, gigawatt electrical (abbreviation: GWe or GW(e)) is a term that refers to electrical power, while megawatt thermal or thermal megawatt (abbreviations: GWt, GW(th) refers to thermal...
		Full Description Close Gigawatt The gigawatt is equal to one billion (10^9) watts or 1 gigawatt = 1000 megawatts. In the electric power industry, gigawatt electrical (abbreviation: GWe or GW(e)) is a term that refers to electrical power, while megawatt thermal or thermal megawatt (abbreviations: GWt, GW(th) refers to thermal power.

Gigawatt-hour

GWh	A gigawatt hour (GWh or GW.h) is a unit of electrical energy equal to 1000 megawatt hours (MWh) and equal to one billion (10^9) watt hours, 3.6 terajoules, or 3.41 billion British thermal units (Btu).

Grid Connection Date

	The date on which the plant is first connected to the electrical grid for the supply of power. After this date, the plant is considered in operation.

Gross Capacity

	Reference gross electrical power of the plant expressed in MW(e). The maximum (electrical) power that could be maintained continuously throughout a prolonged period of operation under reference ambient conditions. The gross electrical power is measured at the output terminals of the turbine...
		Full Description Close Gross Capacity Reference gross electrical power of the plant expressed in MW(e). The maximum (electrical) power that could be maintained continuously throughout a prolonged period of operation under reference ambient conditions. The gross electrical power is measured at the output terminals of the turbine generator.

H

Heavy-Water-Moderated, Boiling Light-Water-Cooled Reactor

HWLWR	An HWLWR typically uses slightly enriched uranium or MOX (Mixed Oxide) fuel (a blend of plutonium and uranium). While standard heavy water reactors can run on natural uranium, the introduction of ordinary "light" water as a coolant absorbs more neutrons, requiring the fuel to be slightly enriched...
		Full Description Close Heavy-Water-Moderated, Boiling Light-Water-Cooled Reactor An HWLWR typically uses slightly enriched uranium or MOX (Mixed Oxide) fuel (a blend of plutonium and uranium). While standard heavy water reactors can run on natural uranium, the introduction of ordinary "light" water as a coolant absorbs more neutrons, requiring the fuel to be slightly enriched to sustain the nuclear chain reaction. The moderator is heavy water and the coolant is ordinary light water.

Heavy-Water-Moderated, Gas-Cooled Reactor

HWGCR	An HWGCR primarily uses natural uranium. Because the reactor is highly efficient at preserving neutrons, it does not require the expensive enrichment process used for standard light-water reactors. The moderator is heavy water and the coolant is a gas, most commonly carbon dioxide. The gas is...
		Full Description Close Heavy-Water-Moderated, Gas-Cooled Reactor An HWGCR primarily uses natural uranium. Because the reactor is highly efficient at preserving neutrons, it does not require the expensive enrichment process used for standard light-water reactors. The moderator is heavy water and the coolant is a gas, most commonly carbon dioxide. The gas is pumped through the reactor core at high pressure to absorb the heat generated by nuclear fission, which it then transfers to a steam generator to produce electricity.

High-Temperature Gas-Cooled, Graphite-Moderated Reactor

HTGR	This type of reactor uses an inert gas, typically helium, as a coolant and graphite as a moderator. Because it operates at exceptionally high temperatures, it achieves much higher thermal efficiency than traditional water-cooled reactors. Additionally, these reactors frequently utilize TRISO fuel...
		Full Description Close High-Temperature Gas-Cooled, Graphite-Moderated Reactor This type of reactor uses an inert gas, typically helium, as a coolant and graphite as a moderator. Because it operates at exceptionally high temperatures, it achieves much higher thermal efficiency than traditional water-cooled reactors. Additionally, these reactors frequently utilize TRISO fuel particles, which can withstand extreme heat without melting and provide robust passive safety features. Beyond generating electricity, the high-temperature output makes HTGRs highly valuable for industrial applications, including efficient hydrogen production and chemical processing.

L

Light Water Cooled Graphite Moderated Reactor

LWGR	Light water cooled graphite moderated reactor. Also known as RBMK. Using light water for cooling and graphite for moderation, it is possible to use natural uranium for fuel.

Load Factor

LF	Load Factor, also called Capacity Factor, for a given period, is the ratio of the energy which the power reactor unit has produced over that period divided by the energy it would have produced at its reference power capacity over that period. Reference energy generation (net) is the energy that...
	More info: http://www-pub.iaea.org/MTCD/Publications/PDF/TRS428_web.pdf	Full Description Close Load Factor Load Factor, also called Capacity Factor, for a given period, is the ratio of the energy which the power reactor unit has produced over that period divided by the energy it would have produced at its reference power capacity over that period. Reference energy generation (net) is the energy that could be produced during a given time period if the unit were operated continuously at reference unit power. The unit load factor is calculated for each period as shown below: LF (%) = EG / REG x 100% Where: - EG = net energy generation (MW.h) for the period - REG = reference energy generation (net) (MW.h) for the period. This indicator reflects the actual energy utilization of the unit for electricity production.

M

Megawatt

MW	The megawatt is equal to one million (10^6) watts. In the electric power industry, megawatt electrical (abbreviation: MWe or MW(e) is a term that refers to electric power, while megawatt thermal or thermal megawatt (abbreviations: MWt, MWth) refers to thermal power.

Megawatt-hour

MWh	A megawatt hour (MWh or MW.h) is equal to 1000 kilowatt hours (kWh). It is an energy equal to 1000 kilowatts of electricity used continuously for one hour.

N

Non-electrical Application

NEA	Some power reactor units produce a portion of their output energy in the form of heat/steam for non-electrical applications (desalination, district heating and industrial heat). This energy is also reported into PRIS.

Nuclear Power Plant

NPP	A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.

Nuclear Share

	The percentage of a country's total electricity generation that is produced from nuclear power. It is calculated as the ratio of nuclear electricity generation to total electricity generation from all sources.

Nuclear Steam Supply System

NSSS	The NSSS consists of the nuclear reactor and all components necessary to produce high pressure steam, which is used to turn the turbine for the electrical generator.

O

On-line Hours

	Total number of hours in the reporting period during which the unit was operated with at least one main generator connected to the grid.

Operating Factor

OF	The operating factor is defined as the ratio of the number of hours the unit was on-line to the total number of hours in the reference period, expressed as a percentage. It is a measure of the unit time availability on the grid and does not depend on the operating power level (UNIPEDE denotes this...
	More info: http://www-pub.iaea.org/MTCD/Publications/PDF/TRS428_web.pdf	Full Description Close Operating Factor The operating factor is defined as the ratio of the number of hours the unit was on-line to the total number of hours in the reference period, expressed as a percentage. It is a measure of the unit time availability on the grid and does not depend on the operating power level (UNIPEDE denotes this as the time utilization factor). On-line hours are the total clock hours during the reference period in which the unit operated with its breakers closed to the unit bus. Reference period hours are the total number of hours in the predefined calendar time. The Operation Factor is calculated as follows: OF (%) = t/T x 100% T Where: - t = number of hours on-line (h) - T = reference period in hours (h)

Operational Reactor

	In PRIS, a reactor is considered as 'operational' or 'in operation' from its first grid connection until permanent shutdown. Thus, when a reactor is temporarily not generating electricity because of outages for, e.g. refuelling, maintenance, repair, large refurbishment or political decision,...
		Full Description Close Operational Reactor In PRIS, a reactor is considered as 'operational' or 'in operation' from its first grid connection until permanent shutdown. Thus, when a reactor is temporarily not generating electricity because of outages for, e.g. refuelling, maintenance, repair, large refurbishment or political decision, the reactor is still categorized as operational. The only exception to this classification is when the reactor’s status is declared as 'long-term shutdown', in which case it is excluded from the operational reactor category until operation resumes or the reactor is permanently shut down.

Operator

	It is the company which currently operates the nuclear power plant

Organic Moderated Reactor

OMR	Organic moderated reactors use an organic hydrocarbon fluid, such as terphenyl, as a coolant, a neutron moderator, or both. In some designs, the organic coolant also serves as the neutron moderator, similar to the role of water in a pressurized water reactor (PWR). In other designs, a separate...
		Full Description Close Organic Moderated Reactor Organic moderated reactors use an organic hydrocarbon fluid, such as terphenyl, as a coolant, a neutron moderator, or both. In some designs, the organic coolant also serves as the neutron moderator, similar to the role of water in a pressurized water reactor (PWR). In other designs, a separate moderator, such as graphite or heavy water, is used. Other possible moderator materials include beryllium, beryllium oxide, and zirconium hydride. These reactors have used a variety of fuel types, including highly enriched uranium (HEU) and slightly enriched uranium dioxide (UO2). In some designs, the uranium dioxide is dispersed in a stainless-steel matrix and fabricated into thin fuel plates.

Outage

	For PRIS coding purposes, an outage is defined as any period during which the actual output power of a reactor unit is lower than its Reference Unit Power. Under this definition, an outage includes both power reductions and complete unit shutdowns.

Outage Coding System

	The PRIS outage coding is primarily focused on reporting power production losses. The coding includes only those aspects of the outage events that can be useful in analyses focused on elimination of unnecessary power losses. The coding consists of three major codes: • The first code identifies...
	More info: http://www-pub.iaea.org/MTCD/Publications/PDF/TRS428_web.pdf	Full Description Close Outage Coding System The PRIS outage coding is primarily focused on reporting power production losses. The coding includes only those aspects of the outage events that can be useful in analyses focused on elimination of unnecessary power losses. The coding consists of three major codes: • The first code identifies outage date and duration and amount of energy lost due to the outage. • The second code (Type Code), identifies the kind and extent of the outage and provides technical information about the outage. • The third code (Cause Code), covers the causes of the outage and the system that was significantly involved in the outage. To include supplementary information of the outage, a description field is also provided. The outage coding system clearly refers to a statistical (with “codification” and figures) and not to an event approach (with descriptions and root cause analysis). It constitutes a first level tool for plant performance benchmarking.

Owner

	The company that currently owns the nuclear power plant majority.

P

Pebble Bed Modular Reactor

PBMR	PBMR is a type of HTGCR. Each sphere is made of pyrolytic graphite (acting a a moderator). Instead of water, inert helium gas is pumped downward through the loose bed of pebbles.

Permanent Shutdown Date

	The date when the plant is officially declared by the owner to be taken out of commercial operation and shut down permanently without any intention to restart the unit.

Planned Energy Loss

PEL	PEL is the planned energy loss for a one-year period.

Planned Unavailability Factor

PUF	The Planned Unavailability Factor is the ratio of the energy that could have been produced during a given period by a plant's capacity shut down due to planned outages, compared to the maximum energy that could have been produced if the plant had operated continuously at its reference power level...
		Full Description Close Planned Unavailability Factor The Planned Unavailability Factor is the ratio of the energy that could have been produced during a given period by a plant's capacity shut down due to planned outages, compared to the maximum energy that could have been produced if the plant had operated continuously at its reference power level over that same period. It is a performance indicator which can be calculated in the DAVA system to determine quality control.

Power

	Power is the rate at which energy is produced, transferred, or consumed. It is most commonly associated with electricity and is measured in watts (W), typically expressed in kilowatts (kW) or megawatts (MW).

Power Reactor

	A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. In a power reactor, the energy released is used as heat to make steam to generate electricity.

Pressurized Heavy Water Reactor

PHWR	A pressurised heavy water reactor (PHWR) is a nuclear power reactor, commonly using unenriched natural uranium as its fuel, that uses heavy water (deuterium oxide D2O) as its coolant and moderator.

Pressurized Water Reactor

PWR	Pressurized light water moderated and cooled reactor. In a PWR, the reactor core heats water, which does not boil. This hot water then exchanges heat with a lower pressure water system, which turns to steam and drives the turbine.

PRIS Statistics

PRISTA	A web-based reporting application that enables registered users to produce reports and statistics from PRIS.
	More info: prisweb.iaea.org

Process Heating

	Process heating is the heat provided as an energy source to chemical processes for producing commodities. Typical products are paper (cardboards), concrete, heavy water and saltern. Utilization of waste heat in the form of warm water or steam for fish industry or green houses can also be included...
		Full Description Close Process Heating Process heating is the heat provided as an energy source to chemical processes for producing commodities. Typical products are paper (cardboards), concrete, heavy water and saltern. Utilization of waste heat in the form of warm water or steam for fish industry or green houses can also be included but usually excluded because they do not pay the penalty to the heat balance of the power plant. Enter the thermal energy provided during the reference period for process heat delivered in the form of heat (steam or hot water) measured as the difference between the plant feed (outlet) and return (inlet) headers. If it is difficult to provide individual data for (PPF), the total delivery data for (PDH+PPH) are acceptable. If monthly data are difficult to provide, the annual total data are acceptable.

R

Reactor Considered

	The initial status assigned to a reactor that is proposed for construction in the near future. Apart from the basic fields (such as Unit Name and Site), all other data fields are optional.

Reactor Model

	The reactor model identifies a specific reactor design series (e.g. Magnox, AGR, VVER V-213, Konvoi, EPR, BWR-6, etc.) within a particular reactor type (GCR or PWR respectively). All models of the same reactor type usually have the same basic design characteristics (moderator and coolant type and...
		Full Description Close Reactor Model The reactor model identifies a specific reactor design series (e.g. Magnox, AGR, VVER V-213, Konvoi, EPR, BWR-6, etc.) within a particular reactor type (GCR or PWR respectively). All models of the same reactor type usually have the same basic design characteristics (moderator and coolant type and form).

Reactor Name/Unit

	The reactor name/unit is a word or phrase used to identify or designate a reactor.

Reactor Planned

	A reactor is considered planned from the Construction License Application Date until the Construction Start Date, when the first major placement of concrete, typically for the foundation of the reactor building, is carried out.

Reactor Status

	One of the stages of a power reactor during its lifecycle: - Under construction - Operational - In long-term shutdown - Permanently shut down

Reactor Type

	Classification of power reactors by coolant and moderator material: BWR -- Boiling Light-Water-Cooled and Moderated Reactor; FBR -- Fast Breeder Reactor; GCR -- Gas-Cooled, Graphite-Moderated Reactor; HTGR -- High-Temperature Gas-Cooled, Graphite-Moderated Reactor; HWGCR...
		Full Description Close Reactor Type Classification of power reactors by coolant and moderator material: BWR -- Boiling Light-Water-Cooled and Moderated Reactor; FBR -- Fast Breeder Reactor; GCR -- Gas-Cooled, Graphite-Moderated Reactor; HTGR -- High-Temperature Gas-Cooled, Graphite-Moderated Reactor; HWGCR -- Heavy-Water-Moderated, Gas-Cooled Reactor; HWLWR -- Heavy-Water-Moderated, Boiling Light-Water-Cooled Reactor; LWGR -- Light-Water-Cooled, Graphite-Moderated Reactor; PHWR -- Pressurized Heavy-Water-Moderated and Cooled Reactor; PBMR -- Pebble Bed Modular Reactor; PWR -- Pressurized Light-Water-Moderated and Cooled Reactor; SGHWR -- Steam-Generating Heavy-Water Reactor.

Reference Energy Generation

REG	Reference energy generation (MWh or GWh) is the net electrical energy that would be produced during a given period if the reactor unit operated continuously at its Reference Unit Power throughout the entire period.

Reference Unit Power

RUP	The reference unit power expressed in units of megawatt (electrical) is the maximum (electrical) power that could be maintained continuously throughout a prolonged period of operation under reference ambient conditions. The power value is measured at the unit outlet terminals, i.e. after deducting...
	More info: http://www-pub.iaea.org/MTCD/Publications/PDF/TRS428_web.pdf	Full Description Close Reference Unit Power The reference unit power expressed in units of megawatt (electrical) is the maximum (electrical) power that could be maintained continuously throughout a prolonged period of operation under reference ambient conditions. The power value is measured at the unit outlet terminals, i.e. after deducting the power taken by unit auxiliaries and the losses in the transformers that are considered integral parts of the unit. The reference unit power is expected to remain constant unless, following design changes, or a new permanent authorization, the management decides to amend the original value.

S

Scram

	A reactor scram is a rapid reactor shutdown achieved by the insertion of negative reactivity into the reactor core. A scram may be initiated either manually or automatically by the reactor protection system.

Sodium Graphite Reactor

SGR	Sodium graphite reactors use sodium metal as a coolant, which can operate at higher temperatures than high-pressure water, enabling higher thermal efficiency. They also use graphite as a moderator. Graphite moderators allow reactors to operate with relatively little fissile material and low levels...
		Full Description Close Sodium Graphite Reactor Sodium graphite reactors use sodium metal as a coolant, which can operate at higher temperatures than high-pressure water, enabling higher thermal efficiency. They also use graphite as a moderator. Graphite moderators allow reactors to operate with relatively little fissile material and low levels of enrichment, making it possible to use natural or low-enriched uranium as fuel. In contrast, sodium-cooled fast reactors typically require uranium enriched to approximately 12% or higher to achieve startup and sustain a neutron chain reaction.

Steam-Generating Heavy-Water Reactor

SGHWR	SGHWR is a type of HWLWR. The reactor primarily uses low-enriched uranium dioxide, encased in a zirconium alloy. Because light water is used as the coolant and absorbs neutrons, natural uranium cannot easily sustain the chain reaction in this design, making slight enrichment necessary. The coolant...
		Full Description Close Steam-Generating Heavy-Water Reactor SGHWR is a type of HWLWR. The reactor primarily uses low-enriched uranium dioxide, encased in a zirconium alloy. Because light water is used as the coolant and absorbs neutrons, natural uranium cannot easily sustain the chain reaction in this design, making slight enrichment necessary. The coolant is ordinary light water.

Supplier

	The supplier consists of one or more vendors that are designated as providers.

Suspended Construction

	When the construction of a reactor has been suspended, and no new construction restart date has been specified.

Suspended Operation

Susp. Op	A reactor is considered in the suspended operations status, if it has been shut down for an extended period (usually more than one year) and there is the intention to re-start the unit but: 1. Active efforts to restart the unit are not underway (there is no vigorous onsite activity to...
		Full Description Close Suspended Operation A reactor is considered in the suspended operations status, if it has been shut down for an extended period (usually more than one year) and there is the intention to re-start the unit but: 1. Active efforts to restart the unit are not underway (there is no vigorous onsite activity to restart the unit) or 2. No firm restart date or recovery schedule has been established when the unit was shut down. Suspended operations may be due to technical, economical, strategic or political reasons. This status does not apply to long-term maintenance outages, including unit refurbishment, if the outage schedule is consistently followed, or to long-term outages due to regulatory restrictions (licence suspension), if restart (licence recovery) term and conditions have been established. Such units are still considered "operational" (in a long-term outage). If an intention not to restart the shutdown unit has been officially announced by the owner, the unit is considered "permanently shut down".

Suspended Plan

	The planned reactor project has been suspended, and no new Construction Start Date has been specified.

T

Terawatt-hour

TWh	A terawatt hour (TWh or TW.h) is a unit of electrical energy equal to 1000 gigawatt hours (GWh).

Thermal Capacity

	The Reference thermal power of the plant expressed in MW(th). The reactor thermal power is the net heat transferred from the fuel to the coolant.

Trial Operation

	In PRIS, a reactor is in trial operation from its first grid connection until the date when it is officially declared in commercial operation (Commercial Operation Date)

U

Under Construction

	A reactor unit is considered under construction from the Construction Start Date until the First Grid Connection Date.

Unit Capability Factor

UCF	Unit capability factor is defined as the ratio of the available energy generation, during a given period to the reference energy generation during the same period, expressed as a percentage. Both of these energy generation terms are determined relative to reference ambient conditions. Available...
	More info: http://www-pub.iaea.org/MTCD/Publications/PDF/TRS428_web.pdf	Full Description Close Unit Capability Factor Unit capability factor is defined as the ratio of the available energy generation, during a given period to the reference energy generation during the same period, expressed as a percentage. Both of these energy generation terms are determined relative to reference ambient conditions. Available energy generation is the energy that could have been produced under reference ambient conditions considering only limitations within control of plant management, i.e., plant equipment and personnel performance, and work control. Reference energy generation is the energy that could be produced if the unit were operated continuously at full power under reference ambient conditions. Reference ambient conditions are environmental conditions representative of the annual mean (or typical) ambient conditions for the unit. The unit capability factor is determined for each period as shown below: value for a unit: UCF (%) = (REG - PEL - UEL)/REG x 100 % Where: - REG = reference energy generation for the period - PEL = total planned energy losses for the period - UEL = total unplanned energy losses for the period The purpose of this indicator is to monitor progress in attaining high unit and industry energy production reliability. This indicator reflects effectiveness of plant programs and practices in maximizing available electrical generation, and provides an overall indication of how well plants are operated and maintained.

Unplanned Capability Loss Factor

UCL	The ratio of the unplanned energy losses during a given period of time, to the reference energy generation, expressed as a percentage. Unplanned energy loss is the energy not produced because of unplanned shutdowns, outage extensions, or unplanned load reductions resulting from causes under the...
	More info: http://www-pub.iaea.org/MTCD/Publications/PDF/TRS428_web.pdf	Full Description Close Unplanned Capability Loss Factor The ratio of the unplanned energy losses during a given period of time, to the reference energy generation, expressed as a percentage. Unplanned energy loss is the energy not produced because of unplanned shutdowns, outage extensions, or unplanned load reductions resulting from causes under the control of plant management. An energy loss is considered to be unplanned if it was not scheduled at least four weeks in advance. Reference energy generation is the energy that could have been produced if the unit had operated continuously at full power under reference ambient conditions throughout the period. The unplanned capability loss factor is determined for each period as follows: UCL(%) = UEL / REG x 100% Where: - UEL = total unplanned energy losses for the period - REG = reference energy generation for the period

Unplanned Energy Loss

UEL	UEL is the total unplanned energy loss during the reporting period.

Unplanned Unavailabilty Factor

UUF	The Unplanned Unavailability Factor is the ratio of the energy that could have been produced during a specific period but was lost due to unplanned outages, sudden equipment failures, or emergency power reductions, compared to the total maximum energy the plant could have produced running at full...
		Full Description Close Unplanned Unavailabilty Factor The Unplanned Unavailability Factor is the ratio of the energy that could have been produced during a specific period but was lost due to unplanned outages, sudden equipment failures, or emergency power reductions, compared to the total maximum energy the plant could have produced running at full capacity during that same period. It is a performance indicator which can be calculated in the DAVA system.

W

Web-Enabled Data Acquisition System

WEDAS	A web-based application used by PRIS data providers to enter operational data into the PRIS database online.
	More info: prisweb.iaea.org/wedas