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Introduction

SECTION 5. UNITS OF PROPERTY FOR NUCLEAR-POWERED POWER STATIONS

Internal Revenue Bulletin 2013-22 · 2026-10-03 edition · updated 2026-10-04 · United States

.01 In general . A nuclear-powered power station uses either a boiling water reactor (BWR) or a pressurized water reactor (PWR) to generate steam, but not both. Therefore, an individual nuclear-powered power station will not contain all of the units of property or major components listed below. For nuclear-powered power stations, the Service will not challenge any of the following unit of property or major component determinations for purposes of the application of § 263(a) and the regulations thereunder.

.02 Station property . (1) Station property serving a generating unit constitutes a single unit of property. Station property is each structure that physically supports and/or encloses the generating unit equipment, and associated systems and support facilities. It does not include accessory buildings (such as administrative, training, or laboratory buildings) or administrative office sections of the power station and systems that support administrative space (such as heating, air conditioning and ventilation, plumbing, and the electrical system within the administrative space). As noted in Appendix A, section 1.01 above, if a unit of property is shared by more than one generating unit, the unit of property is a single unit of property. However, in a power station with two generating units, if a single structure and its associated systems solely supports generating unit 1, another structure and its associated systems solely supports generating unit 2, and a third structure and its associated systems supports both generating units 1 and 2, there are three separate units of station property (the structure and its associated systems solely supporting generating unit 1, the structure and its associated systems solely supporting generating unit 2, and the structure and its associated systems supporting both generating units 1 and 2).

(2) Station property contains the following major components: (a) turbine building crane, (b) reactor building crane, (c) all other overhead cranes, and (d) all compressed air systems. .03 Containment Building . (1) Each containment building constitutes a single unit of property. The containment building is the structure enclosing a nuclear reactor.

(2) The containment building contains one major component: the containment building access doors. .04 Reactor emergency poison system . (1) Each emergency poison system for an individual reactor constitutes a single unit of property. The reactor emergency poison system is the equipment used to inject soluble neutron poison into the reactor coolant in the event of an emergency to terminate the heat generating nuclear reaction.

(2) The reactor emergency poison system contains the following major components: (a) storage tank, and (b) injection equipment. .05 Reactor vessel . (1) Each reactor vessel constitutes a single unit of property. The reactor vessel is the pressurized vessel containing the reactor coolant and the reactor core where the heat produced by nuclear fission is transferred to water in a process that creates steam.

(2) The reactor vessel contains the following major components: (a) reactor vessel head, (b) steam separator (BWR), (c) steam dryer (BWR), (d) reactor core plate assembly, and (e) instrumentation and controls. .06 Nuclear fuel system . (1) Each nuclear fuel system constitutes a single unit of property. The nuclear fuel system is the equipment that monitors and controls the nuclear fuel in a reactor vessel.

(2) The nuclear fuel system contains one major component: instrumentation and controls. .07 Reactor recirculation system (BWR) . (1) Each reactor recirculation system constitutes a single unit of property. The reactor recirculation system is the equipment in a boiling water reactor that returns condensed water to the reactor core to be heated into steam.

(2) The reactor recirculation system contains the following major components: (a) each recirculating pump, (b) each jet pump, and (c) instrumentation and controls.

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.08 Reactor coolant system (PWR) . (1) Each reactor coolant system constitutes a single unit of property. The reactor coolant system is the equipment in a pressurized water reactor that circulates liquid coolant through the reactor core, the pressurizer, and the steam generator.

(2) The reactor coolant system contains the following major components: (a) each steam generator, (b) pressurizer, (c) each reactor cooling water pump, (d) each loop of the water conveyance system, (e) each safety injection tank, and (f) instrumentation and controls. .09 Feed and steam cycle . (1) Each feed and steam cycle serving an individual reactor constitutes a single unit of property. The feed and steam cycle is the equipment that forms a closed loop through which the treated water circulates from the condenser to the reactor or steam generator, through the turbines, and back to the condenser.

(2) The feed and steam cycle contains the following major components, the number of which will vary depending on the reactor technology used:

(a) each reactor feed pump (BWR), (b) each feedwater pump (PWR), (c) each loop of the water conveyance system, (d) each condenser, (e) each condensate pump, (f) each demineralizer, (g) each heat exchanger or feedwater heater, (h) each moisture separator, and (i) instrumentation and controls. .10 Cooling water system . (1) Each cooling water system constitutes a single unit of property. The cooling water system is the equipment that removes heat from the feed and steam cycle. The removal of heat is accomplished by bringing in water from an outside source and using a cooling tower or other cooling device to remove heat.

(2) The cooling water system contains the following major components: (a) each cooling water pump, (b) each cooling tower, (c) each loop of the water conveyance system, (d) screens, and (e) instrumentation and controls. .11 High pressure core safety system (BWR) . (1) Each high pressure core safety system constitutes a single unit of property. The high pressure core safety system is the equipment that injects pressurized coolant into a boiling water reactor vessel in the event of an emergency.

(2) The high pressure core safety system contains the following major components: (a) each tank, (b) each high pressure core injection pump, (c) each loop of the water conveyance system, and (d) instrumentation and controls. .12 Automatic depressurization system (BWR) . (1) Each automatic depressurization system constitutes a single unit of property. The automatic depressurization system is the equipment that depressurizes a boiling water reactor vessel and allows lower pressure coolant injection systems to function.

(2) The automatic depressurization system contains the following major components: (a) each loop of the water conveyance system, and (b) instrumentation and controls. .13 Low pressure coolant injection system (BWR) . (1) Each low pressure coolant injection system constitutes a single unit of property. The low pressure coolant injection system is the equipment that injects coolant into a depressurized boiling water reactor vessel in the event of an emergency. This unit of property may not be in place where a low pressure core spray system is used.

(2) The low pressure injection system contains the following major components: (a) each residual heat removal exchanger, (b) each low pressure coolant injection pump, (c) each tank, (d) each loop of the water conveyance system, and (e) instrumentation and controls.

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.14 Low pressure core spray system (BWR) . (1) Each low pressure core spray system constitutes a single unit of property. The low pressure core spray system is the equipment that sprays water onto the nuclear fuel in a depressurized boiling water reactor vessel in the event of an emergency. This unit of property may not be in place where a low pressure coolant injection system is used.

(2) The low pressure core spray system contains the following major components: (a) each low pressure core spray pump, (b) each tank, (c) each loop of the water conveyance system, and (d) instrumentation and controls. .15 Core flood system (PWR) . (1) Each core flood system constitutes a single unit of property. The core flood system is the equipment used to flood the reactor vessel in a pressurized water reactor in the event of an emergency.

(2) The core flood system contains the following major components: (a) each core flood tank, (b) each loop of the water conveyance system, and (c) instrumentation and controls. .16 Turbine . (1) Each turbine constitutes a single unit of property. The turbine is the equipment that extracts thermal power from pressurized steam and converts the energy into a rotary motion, which motion is used to power the generator.

(2) The turbine contains the following major components: (a) complete set of turbine high-pressure section blades, (b) complete set of turbine mid-pressure section blades, (c) complete set of turbine low-pressure section blades, (d) shaft section in each section of the turbine ( i.e., since the turbine has high, medium, and low-pressure sections, there are three major components: one shaft for each section of the turbine),

(e) shell and casing, and (f) instrumentation and controls. .17 Generator . (1) Each generator constitutes a single unit of property. The generator is the equipment that converts the mechanical energy produced by the water turbine to electrical energy.

(2) The generator contains the following major components: (a) stator, including the windings, shell, and casing, (b) rotor, including core and windings, and (c) instrumentation and controls. .18 Water treatment system . (1) Each water treatment system constitutes a single unit of property. The water treatment system is generally the equipment that removes minerals and other impurities in the water, which is used in the reactor vessel, the reactor recirculation system (BWR), the reactor coolant system (PWR), the feed and steam cycle, the cooling water system, the high pressure core safety system (BWR), the automatic depressurization system (BWR), the low pressure coolant injection system (BWR), the low pressure core spray system (BWR), and the core flood system (PWR).

(2) The water treatment system contains the following major components: (a) filtration system, (b) desalinization system, (c) evaporator, (d) demineralization system, (e) disinfection system, (f) sedimentation system, and (g) instrumentation and controls. .19 Water supply system . (1) Each water supply system constitutes a single unit of property. The water supply system is the equipment that supplies water to the generation plant.

(2) The water supply system contains the following major components: (a) each storage tank, (b) water conveyance system, and (c) instrumentation and controls. .20 Wastewater system . (1) Each wastewater system constitutes a single unit of property. A wastewater system that integrates multiple treatment processes into one system is a single unit of property. Wholly separate and discrete wastewater systems are treated as separate units of property. The wastewater system is the equipment that treats and disposes of wastewater.

(2) The wastewater system contains the following major components: (a) each treatment tank, (b) wastewater conveyance system, and (c) instrumentation and controls.

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.21 Radioactive liquid treatment and disposal system . (1) Each radioactive liquid treatment and disposal system constitutes a single unit of property. The radioactive liquid treatment and disposal system is the equipment that decontaminates liquid radioactive waste prior to the release or recycling of the decontaminated liquid.

(2) The radioactive liquid treatment and disposal system contains the following major components: (a) each tank, (b) liquid conveyance system, (c) liquid concentrator, and (d) instrumentation and controls. .22 Radioactive gas treatment and disposal system . (1) Each radioactive gas treatment and disposal system constitutes a single unit of property. The radioactive gas treatment and disposal system is the equipment that decontaminates gaseous radioactive waste prior to the release of the decontaminated gas.

(2) The radioactive gas treatment and disposal system contains the following major components: (a) each tank, (b) gas conveyance system, (c) condenser, (d) each stack, and (e) instrumentation and controls. .23 Radioactive solid treatment and disposal system . (1) Each radioactive solid treatment and disposal system constitutes a single unit of property. The radioactive solid treatment and disposal system is the equipment that compacts or incinerates radioactive solids prior to storage or disposal.

(2) The radioactive solid treatment and disposal system contains one major component: the instrumentation and controls. .24 Fuel storage and handling system . (1) Each fuel storage and handling system constitutes a single unit of property. The fuel storage and handling system is the equipment that receives fresh nuclear fuel, stores fresh fuel, delivers it to the reactor, removes spent fuel from the reactor, and stores the spent fuel prior to dry cask storage.

(2) The fuel storage and handling system contains the following major components: (a) fuel pool, (b) fuel storage rack system, (c) fuel cranes, and (d) instrumentation and controls. .25 Dry cask facility . (1) Each dry cask facility constitutes a single unit of property. The dry cask facility is the equipment that temporarily stores spent nuclear fuel, where applicable.

(2) The dry cask facility contains the following major components: (a) each spent fuel cask prior to being filled, (b) each dry cask transfer vehicle, and (c) instrumentation and controls. .26 Auxiliary power system . (1) Each auxiliary power system constitutes a single unit of property. The auxiliary power system is the equipment that provides back-up electrical power for the generation plant, which is needed to restart the generating unit after a shutdown.

(2) The auxiliary power system contains one major component: each auxiliary generator. .27 Simulator . (1) Each simulator constitutes a single unit of property. The simulator is the equipment that is used to train plant personnel in the operations (including safety and rescue) of the power plant.

(2) The simulator has no major components. .28 Main step-up transformer . (1) Each main step-up transformer constitutes a single unit of property. The main step-up transformer is equipment that increases the voltage of the electricity generated at the generation plant to a voltage level needed for the transmission of the electricity.

(2) The main step-up transformer has no major components. .29 Heating, ventilation, and air conditioning (HVAC) system . (1) Each heating, ventilation, and air conditioning (HVAC) system serving a unit of station property, as defined in subsection 5.02 above, constitutes a single unit of property. The HVAC system is the equipment that conditions, circulates, and filters the air in the station property.

(2) No special rule is provided under this revenue procedure for the major components of the station electrical system. The major components of the HVAC system are determined under the general principles of § 263(a).

.30 Station electrical delivery system . (1) A power station’s electrical delivery system constitutes a single unit of property. The station electrical delivery system is the equipment that distributes electrical power in the power plant.

(2) No special rule is provided under this revenue procedure for the major components of the station electrical system. The major components of the station electrical system are determined under the general principles of § 263(a).

.31 Safety system . (1) A power station’s safety system constitutes a single unit of property. The safety system is the equipment that alerts power plant personnel to potentially hazardous conditions (including sirens, alarms, and evacuation systems).

(2) The safety system contains the following major components:

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(a) emergency evacuation system, and (b) radiological hygiene station. .32 Environmental radiation monitoring system . (1) A power station’s environmental radiation monitoring system constitutes a single unit of property. The environmental radiation monitoring system is the equipment that continuously monitors the environmental radiation levels inside and outside the generation plant.

(2) The environmental radiation monitoring system contains the following major components: (a) the water monitoring system, and (b) the air monitoring system. .33 Security system . (1) The security system at a power plant constitutes a single unit of property. The security system is the equipment used to provide security at the generation plant.

(2) The security system contains the following major components: (a) the explosive detection system, and (b) each guard tower. .34 Fire Protection System . (1) A power station’s fire protection system constitutes a single unit of property. The fire protection system is the equipment that detects, suppresses, and extinguishes fires.

(2) No special rule is provided under this revenue procedure for the major components of the fire protection system. The major components of the fire protection system are determined under the general principles of § 263(a).

.35 Accessory Buildings . (1) Each accessory building constitutes a single unit of property. An accessory building is a building located at a nuclear-powered power station that is not station property as defined in subsection 5.02 above. For example, laboratory buildings, training buildings, warehouses, administrative buildings, pre-admittance buildings, and maintenance shops are accessory buildings.

(2) No special rule is provided under this revenue procedure for the major components of the accessory buildings. The major components or substantial structural parts of an accessory building are determined under the general principles of § 263(a).

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APPENDIX B

Extrapolation Guidance

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▸Contents — Internal Revenue Bulletin 2013-22

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