HK1226552B - Actuating a nuclear reactor safety device - Google Patents

Description

Actuating a nuclear reactor safety device

Cross Reference to Related Applications

The present application claims priority from U.S. provisional patent application serial No. 61/921,041 entitled "Shunt trip actuator (Shunt actuator)" filed on 26.12.2013 and U.S. patent application serial No. 14/455,348 entitled "Actuating Nuclear Reactor Safety device" filed on 8.8.2014, both of which are incorporated herein by reference in their entirety.

Technical Field

The present disclosure describes a protection device for a nuclear reactor system.

Background

Nuclear reactor systems may be designed with various safety systems. For example, a nuclear reactor system may include a reactor protection system designed to remotely cause a rapid shutdown of one or more reactors (e.g., a SCRAM) if an abnormal operating condition is detected. In some configurations, the reactor protection system may be configured to trigger a remote trip of a reactor trip breaker to initiate a fast reactor shutdown. Further, the remote trip device may be powered by an active power source, but this may not be available for reactor emergencies. For example, an emergency situation may occur in which the active power source supplying power to the remote trip device of the reactor trip breaker is lost (e.g., due to equipment failure, fire, etc.). If the active power source of the remote trip device is lost, the remote trip device may not trip the reactor trip circuit breaker if a reactor trip signal is subsequently received. Thus, the loss of power to the remote trip device reduces the reliability of the reactor protection system and places the nuclear reactor system in a potentially hazardous attitude.

Disclosure of Invention

In a general embodiment, a nuclear reactor trip apparatus includes a remote circuit breaker trip device operably connected to a reactor trip breaker to release a control rod into a nuclear reactor core; an active power source electrically coupled to energize the remote circuit breaker trip device; a passive power source electrically coupled to energize the remote circuit breaker trip device based on a loss of active power source; and a local circuit breaker trip device operatively connected to the reactor trip breaker, including a sensor to trigger the local circuit breaker trip device upon sensing a predefined condition.

In a first aspect combinable with the general implementation, the passive power source includes at least one of a capacitor or a battery.

In a second aspect combinable with any of the preceding aspects, the remote circuit breaker trip device includes a shunt trip coil.

In a third aspect combinable with any of the preceding aspects, the local circuit breaker trip device includes an under-voltage trip assembly.

In a fourth aspect combinable with any of the preceding aspects, the nuclear reactor trip apparatus includes a logic device having a first terminal electrically coupled to the remote circuit breaker trip device and a second terminal electrically coupled to both the active power source and the passive power source.

In a fifth aspect combinable with any of the preceding aspects, the logic device is communicatively coupled to a reactor protection system.

In a sixth aspect combinable with any of the preceding aspects, the logic device is a contactor or a solid state device.

In a seventh aspect combinable with any of the preceding aspects, the nuclear reactor trip apparatus includes a first logic device having a first terminal electrically coupled to the remote circuit breaker trip device and a second terminal electrically coupled to the active power source; and the nuclear reactor trip apparatus includes a second logic device having a first terminal electrically coupled to the remote circuit breaker trip device and a second terminal electrically coupled to the passive power source.

In an eighth aspect combinable with any of the preceding aspects, the first logic device and the second logic device are communicatively coupled to a reactor protection system.

In a ninth aspect combinable with any of the preceding aspects, the first and second logic devices are contactors or solid state devices.

In a tenth aspect combinable with any of the preceding aspects, the nuclear reactor trip includes a first diode electrically coupled between the active power source and the remote circuit breaker trip device and a second diode electrically coupled between the passive power source and the remote circuit breaker trip device.

In an eleventh aspect combinable with any of the preceding aspects, the predefined condition is a condition of voltage loss.

In a general embodiment, a nuclear reactor trip apparatus includes a remote circuit breaker trip device including a shunt trip coil operatively connected to a reactor trip breaker to release a control rod into a nuclear reactor core; a common power source powered from an active power source and electrically coupled to energize the shunt trip coil; and a capacitor acting as a passive power source electrically coupled to energize the shunt trip coil based on a loss of the ordinary power source.

In a first aspect combinable with the general embodiment, the nuclear reactor trip apparatus includes a first logic device having a first terminal electrically coupled to the shunt trip coil and a second terminal electrically coupled to both the common power source and the capacitor.

In a second aspect combinable with any of the preceding aspects, the first logic device is communicatively coupled to a reactor protection system.

In a third aspect combinable with any of the preceding aspects, the first logic device is a contactor or a solid state device.

In a fourth aspect combinable with any of the preceding aspects, the nuclear reactor trip apparatus includes a first logic device having a first terminal electrically coupled to the remote circuit breaker trip device and a second terminal electrically coupled to the active power source; and the nuclear reactor trip apparatus includes a second logic device having a first terminal electrically coupled to the remote circuit breaker trip device and a second terminal electrically coupled to the passive power source.

In a fifth aspect combinable with any of the preceding aspects, the first logic device and the second logic device are communicatively coupled to a reactor protection system.

In a sixth aspect combinable with any of the preceding aspects, the first and second logic devices are contactors.

In a seventh aspect combinable with any of the preceding aspects, the nuclear reactor trip apparatus includes a first diode electrically coupled between the active power source and the remote circuit breaker trip device and a second diode electrically coupled between the passive power source and the remote circuit breaker trip device.

In a general embodiment, a method for providing a backup power source for remotely tripping a nuclear reactor trip circuit breaker includes providing a shunt trip coil operably coupled to a reactor trip circuit breaker, the reactor trip circuit breaker electrically coupled to a reactor control rod drive assembly; electrically coupling a common power source to the shunt trip coil; and electrically coupling a stored energy source to the shunt trip coil.

In a first aspect combinable with the general implementation, the method includes electrically decoupling the common power source from the shunt trip coil based on a power loss of the common power source.

In a second aspect combinable with any of the preceding aspects, the method includes closing a circuit between the stored energy source and the shunt trip coil based on a reactor trip signal.

In a third aspect combinable with any of the preceding aspects, the method includes charging the stored energy source from the common power source.

A fourth aspect combinable with any of the preceding aspects further includes charging the stored energy source from the common power source in a standby mode.

A fifth aspect combinable with any of the preceding aspects further includes maintaining a charge of the stored energy source during the standby mode.

A sixth aspect combinable with any of the preceding aspects further includes detecting a loss of the common power source.

In a seventh aspect combinable with any of the preceding aspects, the common power source is associated with a power source for withdrawing one or more control rods coupled to the reactor control rod drive assembly from a reactor core.

An eighth aspect combinable with any of the preceding aspects further includes activating a first shutdown system; and inserting the one or more control rods into the reactor core based on the activation.

In a ninth aspect combinable with any of the preceding aspects, the inserting is based at least in part on a gravitational force acting on the one or more control rods.

A tenth aspect combinable with any of the preceding aspects also includes detecting improper or incomplete insertion of the one or more control rods into the reactor core.

An eleventh aspect combinable with any of the preceding aspects further includes discharging the stored energy source.

A twelfth aspect combinable with any of the preceding aspects further includes actuating the shunt trip coil.

In a thirteenth aspect combinable with any of the preceding aspects, discharging the stored energy source includes discharging the stored energy source based on detecting improper or incomplete insertion of the one or more control rods into the reactor core.

A fourteenth aspect combinable with any of the preceding aspects also includes operating the reactor trip breaker with the shunt trip coil to move one or more control rods.

In a fifteenth aspect combinable with any of the preceding aspects, the one or more control rods are inserted into the reactor core.

In another general embodiment, a nuclear reactor shutdown system includes a reactor trip breaker; a control rod drive; an under-voltage trip assembly (UVTA) configured to detect a loss of power to a first power source of at least one of the control rod driver or the reactor trip breaker and operate the control rod driver or the reactor trip breaker based at least in part on the detection; and a Shunt Trip Coil (STC) actuated by a passive power source and configured to operate the control rod drive or the reactor trip breaker based at least in part on a failure of the UVTA.

In a first aspect combinable with the general implementation, the passive power source includes a capacitor electrically coupled with the STC.

In a second aspect combinable with any of the preceding aspects, the capacitor is electrically coupled with a second power source through a first diode and with the STC through a second diode.

In a third aspect combinable with any of the preceding aspects, the second power source is configured to charge the capacitor during a normal operating state.

In a fourth aspect combinable with any of the preceding aspects, the second power source is configured to trickle charge the capacitor during a standby state.

In a fifth aspect combinable with any of the preceding aspects, the first power source is electrically coupled to the STC through a third diode, the first power source coupled to the UVTA to provide power to the UVTA.

In a sixth aspect combinable with any of the preceding aspects, the capacitor is discharged based on a detected loss of power from the second power source to the UVTA.

In a seventh aspect combinable with any of the preceding aspects, the first and second power supplies comprise active power supplies.

An eighth aspect combinable with any of the preceding aspects also includes a first set of one or more contacts electrically coupled between the second diode and the STC to control at least one of a discharge of the capacitor to the STC or a charge of the capacitor.

A ninth aspect combinable with any of the preceding aspects also includes a second set of one or more contacts electrically coupled between the first power source and the capacitor to control at least one of discharge of the STC or charge of the capacitor.

Various embodiments according to the present disclosure may also include one, some, or all of the following features. For example, the described embodiments may improve the reliability of remote tripping of reactor trip breakers, and, related, the reliability of reactor protection systems during reactor emergencies. In addition, the embodiments can ensure that the backup power source for the remote trip of the reactor trip breaker remains at a desired state of charge.

The details of one or more embodiments of the presently disclosed subject matter are set forth in the accompanying drawings and the description below

And (5) clearing. Other features, embodiments, and advantages of the subject matter will be apparent from the description, the drawings, and the claims.

Drawings

FIG. 1A illustrates a block diagram of an example embodiment of a nuclear power system including at least one nuclear power reactor and a power distribution system;

FIG. 1B illustrates an example nuclear power system including at least one nuclear power reactor;

FIG. 2 illustrates an example embodiment of a nuclear reactor control rod drive system;

fig. 3A and 3B illustrate circuit diagrams of an exemplary embodiment of a remote trip of a reactor trip breaker with a passive power source;

FIG. 4 illustrates an example reactor core configuration including a neutron source;

FIG. 5 illustrates an example reactor shutdown system; and

FIG. 6 illustrates an example process for performing a reactor shutdown.

Detailed Description

As referred to herein, an active power source is generally an AC or DC power source that actively generates power (e.g., as compared to a stored energy power source). In addition, the active power source is generally a power source that supplies power to the electrical devices under normal operating conditions (e.g., when all power sources in a nuclear reactor power plant are functioning properly). Power from an active power source is primarily derived from a machine type power source (e.g., a generator) and is supplied to an electrical load through one or more electrical buses. In the case of a dc electrical device, the active power source may be powered by a machine type power source, i.e., converted from ac to dc (e.g., through a power rectifier or motor generator) before the power is supplied to the dc bus and ultimately to the electrical load.

As referred to herein, a passive power source is generally a stored energy power source (e.g., a battery, a capacitor, or an Uninterruptible Power Supply (UPS)). The passive power source generally serves as a backup power source for the electrical device.

FIG. 1A illustrates an example embodiment of a nuclear power system 100 including a plurality of nuclear reactor systems 150 and a power distribution system. In some embodiments, the system 100 may provide a Reactor Protection System (RPS) operable to automatically cause a remote fast shutdown of the reactor.

In fig. 1A, the example system 100 includes a plurality of nuclear reactor systems 150 and a nuclear instrumentation and control (I & C) system 135. Although only three nuclear reactor systems 150 are shown in this example, there may be fewer or more systems 150 (e.g., 6, 9, 12, or other numbers) included within the nuclear power system 100 or coupled to the nuclear power system 100. In a preferred embodiment, there may be twelve nuclear reactor systems 150 included within the system 100, with one or more of the nuclear reactor systems 150 including a modular light water reactor, as described further below.

With respect to each nuclear reactor system 150, the reactor core 20 is placed at a bottom portion of the cylindrical or capsule-shaped reactor vessel 70. The reactor core 20 contains a quantity of fissile material that produces a controlled reaction that may occur over a period of potentially several years or more. Although not explicitly shown in fig. 1A, control rods may be used to control the fission rate within the reactor core 20. The control rods may comprise silver, indium, cadmium, boron, cobalt, hafnium, dysprosium, gadolinium, samarium, erbium, and europium, or alloys and compounds thereof. However, these are only a few of the many possible control rod materials. In nuclear reactors designed with passive operating systems, the laws of physics are employed to ensure that safe operation of the nuclear reactor is maintained during normal operation or even in emergency conditions, at least for some predefined period of time, without operator intervention or supervision.

In an example embodiment, a cylindrical or capsule shaped containment vessel 10 surrounds the reactor vessel 70 and is partially or completely submerged in the reactor pool, such as below the waterline 90, within the reactor compartment 5. The volume between reactor vessel 70 and containment vessel 10 may be partially or completely evacuated to reduce heat transfer from reactor vessel 70 to the reactor pool. However, in other embodiments, the volume between reactor vessel 70 and containment 10 may be at least partially filled with a gas and/or liquid that increases heat transfer between the reactor and containment. Containment vessel 10 may rest on a skirt (not shown) at the base of reactor bay 5.

In an example embodiment, the reactor core 20 is submerged within a liquid, such as water, which may include boron or other additives, which rises into the channels 30 after coming into contact with the surface of the reactor core. In fig. 1A, the upward movement of the heated coolant within the passage 30 is represented by arrows 40. The coolant travels over the top of the heat exchangers 50 and 60 and is drawn down the inner walls of the reactor vessel 70 by convection, thus allowing the coolant to apply heat to the heat exchangers 50 and 60. After reaching the bottom portion of the reactor vessel, contact with the reactor core 20 produces heating of the coolant, which rises again through the channels 30.

Although the heat exchangers 50 and 60 are shown as two distinct elements in FIG. 1A, the heat exchangers 50 and 60 may be represented as any number of helical coils that encircle at least a portion of the channel 30. In another embodiment, different numbers of helical coils may encircle the channel 30 in opposite directions, with, for example, a first helical coil spiraling in a counterclockwise direction and a second helical coil spiraling in a clockwise direction. However, use of differently configured and/or differently oriented heat exchangers is not precluded, and embodiments are not limited in this regard. Further, while the water tubes 80 are shown as being placed just above the upper portions of the heat exchangers 50 and 60, in other embodiments, the reactor vessel 70 may contain a lesser or greater amount of water.

In fig. 1A, normal operation of the nuclear reactor module is in the form of heated coolant rising through the passage 30 and coming into contact with the heat exchangers 50 and 60. After contacting the heat exchangers 50 and 60, the coolant falls toward the bottom of the reactor vessel 90 in a manner that induces a thermosiphon process. In the example of fig. 1A, the coolant within the reactor vessel 70 is maintained at a pressure above atmospheric pressure, thus allowing the coolant to remain at a high temperature without vaporizing (e.g., boiling).

As the temperature of the coolant within the heat exchangers 50 and 60 increases, the coolant may begin to boil. When the coolant in the heat exchangers 50 and 60 begins to boil, the vaporized coolant (e.g., steam) may be used to drive one or more turbines that convert the thermal potential energy of the steam into electrical energy. After condensation, the coolant returns to a location near the base of the heat exchangers 50 and 60.

During normal operation of the reactor module of FIG. 1A, various performance parameters of the illustrated nuclear power system 150 may be monitored by means of sensors (e.g., sensors of the I & C system 135) placed at various locations within the module, which are coupled to an interface panel of the I & C system 135 with a communication channel. Sensors within the reactor module may measure reactor system temperature, reactor system pressure, containment pressure, level of reactor primary and/or secondary coolant, reactor core neutron flux, and/or reactor core neutron fluence. Signals representing these measurements may be reported to the outside of the reactor module by means of pipes to a reactor bay interface panel (not shown).

One or more of the components and sensors of each nuclear reactor system 150 may be critical loads, such as active ESF loads, such as containment isolation valves, Decay Heat Removal (DHR) valves, other actuatable valves and devices, and sensors. In some embodiments, such ESF components may be designed to fail in their safe position when the power source or power source is out of control.

In general, the illustrated I & C system 135 provides activation signals (e.g., automatic), automatic and manual control signals, and monitoring and indicator displays to prevent or mitigate the consequences of a fault condition and/or failed components in the system 100. The I & C system 135 provides normal reactor control and protection against unsafe reactor operation of the nuclear power system 150 during steady state and temporary power operations. During normal operation, the instruments measure various process parameters and transmit the signals to the control system of the I & C system 135. During abnormal operation and accident conditions, the instruments transmit signals to portions of I & C system 135, such as Reactor Trip System (RTS)147 and Engineered Safety Features Actuation System (ESFAS)148 (e.g., to mitigate the effects of the accident) that are part of RPS 145 to initiate protective actions based on predetermined set points.

In general, the illustrated RPS 145 triggers a security action to mitigate the consequences of the design ground-up event. In general, the RPS 145 includes all of the equipment (including hardware, software, and firmware) needed to initiate a reactor shutdown, from the sensors to the final actuating devices (power supplies, sensors, signal conditioners, startup circuitry, logic, bypasses, control boards, interconnects, and actuating devices).

In the example implementation, RPS 145 includes RTS 147 and ESFAS 148. In some embodiments, the RTS 147 contains four separate independent sets (e.g., physical grouped process channels with the same class 1E electrical channel designation (A, B, C or D)) that are provided with separate and independent power feeds and process instrumentation transmitters, each of the sets being physically and electrically independent of the other sets, each with an independent measurement channel to monitor plant parameters that can be used to generate reactor trips. Each measurement channel trips when the parameter exceeds a predetermined set point. The consensus logic of the RTS 147 can be designed such that a single failure cannot prevent a reactor trip when needed, and a failure in a single measurement channel cannot generate an unnecessary reactor trip. (Category 1E is a safety scheme approved by RG 1.32 under IEEE Standard 308-2001 section 3.7, which defines the safety classification of electrical equipment and systems essential for emergency reactor shutdown, containment isolation, reactor core cooling, and containment and reactor venting, or otherwise essential in preventing the release of radioactive material in large quantities into the environment.)

In some embodiments, the RPS monitors various nuclear reactor system parameters to detect an abnormal or emergency condition requiring one or more reactor shutdowns. Further, in some implementations, the RPS transmits a trip signal to one or more remote trip devices associated with one or more reactor trip circuit breakers (RTBs). The one or more remote trip devices trip their associated RTBs causing control rods of the reactor to be inserted into the reactor core, thereby quickly shutting down the reactor. Further, in some implementations, the one or more remote trip devices include both active and passive power sources that may improve the reliability of the RPS by maintaining power to the remote trip devices in the event one of the power sources is lost during an emergency.

The system 100 may include four defensive fleets, e.g., a particular application of the principles of deep defense to the arrangement of instrumentation and control systems attached to a nuclear reactor for the purpose of operating the reactor or shutting down and cooling the reactor, as defined in NUREG/Cr-6303. In particular, the four fleets are the control system, the reactor trip or scram system, the ESFAS, and the monitoring and indicator system.

The reactor trip system echelon typically includes an RTS 147, such as a safety device designed to rapidly reduce the reactivity of the reactor core in response to an uncontrolled offset. This echelon is typically comprised of instrumentation for detecting potential or actual excursions, equipment and procedures for rapid and complete insertion of the reactor control rods, and may also contain certain chemical neutron mitigation systems (e.g., boron injection).

In addition to including the four defensive ladders, the system 100 also includes multiple levels of diversity. In particular, I & C diversity is the principle of using different technologies, logic or algorithms to measure variables or provide actuation means to provide different ways of responding to assumed plant conditions.

Additionally, the power system 110 may provide both ac and dc power to the entire electrical load of the nuclear reactor system 150. For example, ac power (e.g., 120VAC, 1 phase, 60Hz) may be provided to the nuclear reactor system 150 via one or more ac buses. The ac bus may be divided into a critical ac bus and a non-critical ac bus. The critical ac bus may provide ac power to critical loads (e.g., ESF loads). The ac power may also be provided to non-critical loads of the nuclear reactor system 150 via one or more non-critical ac buses. Direct current power (e.g., 125VDC) may be provided to the nuclear reactor system 150 through one or more alternating current buses.

Turning briefly to FIG. 1B, an example of a nuclear power system including at least one nuclear reactor module 1 is shown. The nuclear reactor module 1 includes a reactor core 6 surrounded by a reactor vessel 2. The coolant 13 in the reactor vessel 2 surrounds the reactor core 6. The reactor core 6 may be located in a shroud 22 that surrounds the sides of the reactor core 6. As the coolant 13 is heated by the reactor core 6 due to a fission event, the coolant 13 may be directed from the shroud 22 up into a ring 23 located above the reactor core 6 and out of the risers 24. This may cause additional coolant 13 to be drawn into the shroud 22, which in turn is heated by the reactor core 6, such that more coolant 13 may be drawn into the shroud 22. The coolant 13 emerging from the riser 24 may be cooled down and directed to the outside of the reactor vessel 2 and then returned to the bottom of the reactor vessel 2 by natural circulation. As the coolant 13 is heated, pressurized steam 11 (e.g., steam) may be generated in the reactor vessel 2.

The heat exchanger 35 may be configured to circulate feedwater and/or steam in the secondary cooling system 31 to generate electricity with the turbine 32 and the generator 34. In some examples, the feedwater passes through a heat exchanger 35 and may become superheated steam. The secondary cooling system 31 may include a condenser 36 and a feedwater pump 38. In some examples, the feedwater and/or steam in the secondary cooling system 31 remains isolated from the coolant 13 in the reactor vessel 2 such that they cannot mix or come into direct contact with each other.

The reactor vessel 2 may be surrounded by a containment vessel 4. In some examples, containment vessel 4 may be placed in a pool of water, for example, positioned below ground level. Containment vessel 4 may be configured to inhibit release of coolant 13 associated with reactor vessel 2 from escaping into the environment outside and/or surrounding containment vessel 4. In an emergency, the vapor 11 may be vented from the reactor vessel 2 into the containment vessel 4 through the flow limiter 8, and/or the coolant 13 may be released through the purge valve 18. The rate at which the vapor 11 and/or coolant 13 is released into the containment vessel 4 may vary depending on the pressure within the reactor vessel 2. In some examples, decay heat associated with reactor core 6 may be at least partially removed by a combination of condensation of vapor 11 on the inner walls of containment vessel 4 and/or suppression of release of coolant 13 through purge valve 18.

The containment vessel 4 may be generally cylindrical in shape. In some examples, containment vessel 4 may have one or more ellipsoidal, hemispherical, or spherical ends. Containment vessel 4 may be welded or otherwise sealed from the environment such that liquids and/or gases are not allowed to escape from containment vessel 4 or enter containment vessel 4. In different examples, reactor vessel 2 and/or containment vessel 4 may be bottom supported, top supported, supported about its center, or any combination thereof.

The inner surfaces of the reactor vessel 2 may be exposed to a humid environment comprising the coolant 13 and/or the vapor 11, and the outer surfaces of the reactor vessel 2 may be exposed to a substantially dry environment. The reactor vessel 2 may comprise and/or be made of stainless steel, carbon steel, other types of materials or composites, or any combination thereof. Additionally, the reactor vessel 2 may include cladding and/or insulating materials.

Containment vessel 4 may substantially surround reactor vessel 2 within containment region 14. In some examples and/or modes of operation, the containment region 14 may include a dry, voided, and/or gaseous environment. The containment region 14 may include a quantity of air, an inert gas such as argon, other types of gases, or any combination thereof. In some examples, the containment region 14 may be maintained at or below atmospheric pressure, such as at a partial vacuum. In other examples, the containment region 14 may be maintained at a substantially complete vacuum. Any gas or gases in containment vessel 2 may be evacuated and/or removed prior to operation of reactor module 1.

Certain gases may be considered non-condensable when subjected to operating pressures within a nuclear reactor system

In (1). These non-condensable gases may for example comprise hydrogen and oxygen. During emergency operation, steam may chemically react with the fuel rods to produce high hydrogen levels. This may form a combustible mixture when hydrogen is mixed with air or oxygen. By removing a substantial portion of the air or oxygen from the containment vessel 4, the amount of hydrogen and oxygen allowed to mix may be minimized or eliminated.

Any air or other gas trapped in the containment region 14 may be removed or voided upon detection of an emergency condition. The gas voided or evacuated from the containment region 14 may include non-condensable gases and/or condensable gases. The condensable gases may include any steam that is vented into the containment region 14.

During emergency operations, although steam and/or steam may be vented into containment region 14, only a negligible amount of non-condensable gases (e.g., hydrogen) may be vented or released into containment region 14. From a practical standpoint, it is possible that substantially no non-condensable gases are released into the containment region 14 along with the vapors. Thus, in some examples, substantially no hydrogen is vented into the containment region 14 along with the vapors such that the level and/or amount of hydrogen that may be present within the containment region 14 along with any oxygen is maintained at a non-flammable level. In addition, this non-flammable level of the oxygen-hydrogen mixture may be maintained without the use of a hydrogen reformer.

Convective heat transfer removal from air occurs primarily at about 50 torr (50mm Hg) absolute pressure, but a decrease in convective heat transfer at approximately 300 torr (300mm Hg) absolute pressure is observed. In some examples, the containment region 14 may be provided with or maintained at a pressure below 300 torr (300mm Hg). In other examples, the containment region 14 may be provided with or maintained at a pressure below 50 torr (50mm Hg). In some examples, containment region 14 may be provided with and/or maintained at a pressure level that substantially inhibits all convective and/or conductive heat transfer between reactor vessel 2 and containment vessel 4. A full or partial vacuum may be provided and/or maintained by operating a vacuum pump, a steam-air ejector, other types of evacuation devices, or any combination thereof.

By maintaining the containment region 14 at a vacuum or partial vacuum, moisture within the containment region 14 may be eliminated, thereby protecting electrical and mechanical components from corrosion or failure. Additionally, during emergency operations (e.g., an over-pressurization or over-heating event), the vacuum or partial vacuum may operate to draw or pull coolant into the containment region 14 without the use of a separate pump or elevated sump. The vacuum or partial vacuum may also operate to provide a way to flood or fill the containment region 14 with coolant 13 during the refueling process.

A flow restrictor 8 may be placed on the reactor vessel 2 for venting coolant 13 and/or vapor 11 into the containment vessel 4 during emergency operation. The flow restrictor 8 may be attached or mounted directly to the outer wall of the reactor vessel 2 without any intervening structure, such as piping or connections. In some examples, the flow restrictor 8 may be welded directly to the reactor vessel 2 to minimize the possibility of any leaks or structural failures. The flow restrictor 8 may comprise a venturi flow valve configured to release the gas 11 into the containment vessel 4 at a controlled rate. The condensation of vapor 11 may reduce the pressure in containment vessel 4 at approximately the same rate that vented vapor 11 adds pressure to containment vessel 4.

The coolant 13 released as vapor 11 into containment vessel 4 may condense as a liquid, such as water, on the inner surface of containment vessel 4. Condensation of vapor 11 may cause a pressure reduction in containment vessel 4 as vapor 11 transitions back to a liquid coolant. By condensation of vapor l1 on the inner surface of containment vessel 4, a sufficient amount of heat may be removed to control the removal of decay heat from reactor core 6.

The condensed coolant 13 may descend to the bottom of the containment vessel 4 and pool as a pool of liquid. As more vapor 11 condenses on the inner surface of containment vessel 4, the level of coolant 13 within containment vessel 4 may gradually rise. The heat stored in the vapor 11 and/or coolant 13 may be transferred to the ambient environment through the walls of the containment vessel 4. By substantially removing gas from containment region 14, the initial rate of condensation of vapor l1 on the interior surface of containment vessel 4 may be increased by the evacuated gas. Due to natural convection of coolant 13, gases that typically accumulate on the inner surface of containment vessel 4 to inhibit condensation of coolant 13 are at low levels or are swept away from the inner surface so that the rate of condensation may be maximized. Increasing the rate of condensation may in turn increase the rate of heat transfer through containment vessel 4.

During normal operation of the reactor module, the vacuum within the containment region 14 may act as some type of thermal insulation, thereby retaining heat and energy in the reactor vessel 2 that may be continued to be used to generate electricity. Thus, the design of the reactor vessel 2 may use less material insulation. In some examples, reflective insulation may be used instead of, or in addition to, conventional thermal insulation. Reflective insulation may be included on one or both of the reactor vessel 2 or containment vessel 4. The reflective insulation may be more resistant to water immersion than conventional thermal insulation. Additionally, the reflective insulation may not impede the transfer of heat from the reactor vessel 2 during an emergency as conventional thermal insulation. For example, the exterior stainless steel surface of the reactor vessel 2 may directly contact any coolant located in the containment region 14.

Neutron detection device 25 is shown mounted outside containment vessel 4. The neutron detection device 25 may be placed at a height close to the core. The neutron detection device 25 may be configured to detect neutrons generated at or near the reactor core 6. The detected neutrons may include fast neutrons, slow neutrons, thermalized neutrons, or any combination thereof. In some examples, the neutron detection device 25 may be separated from the neutron source by the containment region 14. Neutrons generated by and/or emitted from the neutron source may pass through containment region 14 before being detected by neutron detection device 25.

The reactor shutdown system may have one or more mechanisms, systems, apparatuses, devices, methods, operations, modes, and/or means for removing and/or reducing power in the reactor core 6. For example, the reactor shutdown system may be configured to insert one or more control rods 16 into the reactor core 6, or to allow control rods 16 to be inserted into the reactor core 6. Control rods 16 may be inserted into the reactor core 6 as part of the operation of shutting down the reactor module 1 for maintenance, refueling, detection, certification, transportation, high and/or high temperature readings in the reactor vessel, power surges, elevated levels of critical conditions and/or the number of detected fission events, emergency operation, other types of operation, or any combination thereof. In some examples, the reactor shutdown system may be configured to insert the control rods 16 in response to information provided by the neutron detection device 25.

Fig. 2 illustrates an example embodiment of a nuclear reactor control rod drive system 200, shown in a portion of a nuclear reactor system (e.g., nuclear reactor system 100). As shown, the control rod drive system 200 includes a drive mechanism 205, a drive actuator 220, and a drive shaft 210. Although a single drive mechanism 205, drive actuator 220, and drive shaft 210 are shown in fig. 2, a nuclear reactor control rod drive system 200 for a nuclear reactor may have multiple drive mechanisms 205, drive actuators 220, and drive shafts 210. As shown, the drive system 200 is shown housed in the reactor vessel 70 and coupled to the control rods 45. The control rods 45 in this figure are shown at least partially inserted into the core 20 of the nuclear reactor system.

In the illustrated embodiment, the actuator 220 of the drive mechanism 205 is communicatively coupled to the control system 225 through a Reactor Trip Breaker (RTB) 235. In general, the control system 225 may receive information (e.g., temperature, pressure, flux, valve status, pump status, or other information) from one or more sensors of the nuclear reactor system 100 and, based on this information, control the actuator 220 to energize or de-energize the drive mechanism 205. In some embodiments, the control system 225 may be a master controller (e.g., a processor-based electronic device or other electronic controller) of the nuclear reactor system. For example, the master controller may be a master controller communicatively coupled to slave controllers at respective control valves. In some embodiments, the control system 225 may be a proportional-integral-derivative (PID) controller, an ASIC (application specific integrated circuit), a microprocessor based controller, or any other suitable controller. In some embodiments, the control system 225 may be all or part of a distributed control system.

The illustrated drive mechanism 205 is coupled (e.g., threadably coupled) to the drive shaft 210 and is operable to adjust the position of the control rods 45 in the reactor vessel 70 (e.g., within the core 20) in response to operation of the actuator 220 by raising or lowering the control rods 45 using the drive shaft 210. In some embodiments, the drive mechanism 205 controls the movement of the drive assembly 200 and the control rods 45 only during normal operation.

In the event of an abnormal reactor operating condition, by securing power to the drive mechanism 205, the RTB235 may be tripped (i.e., disconnected) to quickly shut down the reactor system 150. With power secured to the drive mechanism 205, the drive mechanism 205 releases the drive shaft allowing the control rods 45 to be inserted into the reactor core 20 under gravity, thereby rapidly reducing core reactivity and shutting down the reactor system 150. In the illustrated embodiment, RTB235 is represented as a single block component; however, RTB235 may represent multiple RTBs.

The RTB235 can be tripped by one of three different methods: manual trip, local automatic trip, and remote trip 240. The local automatic trip is typically an under-voltage trip that causes the RTB235 to open and the control rod 45 to drop when a supply voltage is lost (e.g., power from the control system 225 to the drive mechanism 205). The manual trip provides a direct trip of the RTB 235. The under-voltage trip may include a sensor monitoring the supply voltage and tripping the circuit breaker at a predetermined voltage or at a predetermined change in the supply voltage. For example, the under-voltage trip may be a spring-loaded mechanical device that includes a solenoid connected to the power supply side of the RTB235 that is designed to hold the RTB235 in a closed position as long as the power supply voltage delivered by the power supply is above a threshold (e.g., 0V), thereby tripping the RTB235 when voltage is lost.

In some embodiments, the remote trip device 240 is controlled by the RTS 147 and is powered from one or more active power sources 245 (e.g., a dc power bus) under normal conditions (e.g., a common power source for the remote trip device 240). When the remote trip device 240 receives a trip signal from the RTS 147, the remote trip device 240 trips the RTB235 open. In general, RPS 145 includes a plurality of separate sets of sensors and detectors; a plurality of signal conditioning and signal conditioner separation groups; a plurality of trip determination separation groups; and a plurality of RTS voting divisions and RTBs 235. The trip inputs are combined in RTS voting logic such that more than one reactor trip input from the trip determination is required to produce an automatic reactor trip output signal that actuates the remote trip device 240 for all of the RTBs 235 or a subset of all of the RTBs 235 associated with the respective bay.

In addition, the remote trip unit 240 includes a passive power source (e.g., 305 as shown in fig. 3A-3B). The passive power source improves the reliability of remote trip device 240, and, in turn, RPS 145, during a reactor emergency. For example, without a passive power source, an emergency situation may arise where the active power source 245 (e.g., a normal power source) supplying power to the remote trip device 240 is lost, but the RTB235 is not actuated. Loss of power to the remote trip device 240 reduces the reliability of the RPS 145 and places the reactor system 150 in a potentially hazardous position. Because of the loss of active power 245 to the remote trip device 240, the remote trip device 240 will not trip the RTB235 if a reactor trip signal is received from the RTS 147.

Fig. 3A and 3B illustrate circuit diagrams of exemplary features of reactor trip breaker remote trip devices 240a and 240B with passive power sources. The RTB remote trip device 240 shown includes a passive power supply 305, a shunt trip coil 310, diodes (e.g., any electrical device with asymmetric conductivity) 315a-315c, an RTS logic device 320, and active power connections 325a and 325b (e.g., for connection to an active power supply 245). The passive power source 305 serves as a backup power source for the RTB remote trip devices 240a and 240 b. The passive power source 305 is typically a capacitor, but may also be a battery or other device for storing electrical energy.

The shunt trip coil 310 is operably connected to the RTB235 and, when energized, causes the RTB to trip open. RTS logic 320 is communicatively coupled to the RTS 147 and energizes the shunt trip coil 310 upon receiving a trip signal from the RTS 147. RTS logic device 320 is typically a normally open contactor or relay. In some implementations, the RTS logic device can be or contain one or more high power solid state switches, such as high power transistors, e.g., Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). Generally, the two sets of RTS logic devices 320 operate in tandem, that is, receive the same signal from the RTS 147 and both synchronously open or close the circuit path to the shunt trip coil 210.

In example operation, and referring to fig. 3A, prior to receiving the trip signal, the RTS device 320 acts as an open switch and no (or negligible) current flows through diodes 315b and 315 c. Current is permitted to flow from the active power supply connection 325a via diode 315a to charge the passive power supply 305. The passive power source 305 is then held at a peak charge while it receives voltage from 325a (e.g., the active power source 245). When RTS logic device 320 receives the trip signal, RTS logic device 320 acts as a closed switch, thereby allowing current to flow from active power connection 325b to shunt trip coil 310 via diode 315c and from active power connection 325a to shunt trip coil 310 via diodes 315a and 315 b.

The energized shunt trip coil 310 causes the RTB235 to trip open and the control rod 45 to drop. Diodes 315a-315c prevent the power supply connected to active power connections 325a and 325b from shorting by allowing only unidirectional power flow (e.g., away from connections 325a and 325 b). Active power connections 325a and 325b are primarily connected to the same power source (e.g., active power source 245), but in some embodiments they may be connected to different power sources, in which case the diodes prevent cross-connection of two different power sources.

If the RTS logic device receives a trip signal at a time when power is unavailable to either of the active power connections 325a or 325b (e.g., when the active power supply 245 fails), the shunt trip coil 210 is energized by power supplied from the passive power supply 305. Current flows from the passive power supply 305 to the shunt trip coil 310 via 315b to trip open the RTB 235. Diodes 315a and 315c prevent energy stored in the passive power source 305 from being lost to circuitry external to the RTB remote trip device 240a and ensure that all (or a substantial amount) of the energy is transferred to the shunt trip coil 305. In other words, diodes 315a and 315c are used to electrically decouple the active power source (e.g., connection 325a or 325b) from the passive power source 305 and the shunt trip coil 310 in the event of a loss of the active power source. This ensures that the energy stored in the passive power source 305 is not transferred to other electrical components connected to the power bus associated with the active power source.

Fig. 3B shows an alternative embodiment of an RTB remote trip unit 240B with a passive power source 305. RTB remote trip device 240b contains only one RTS logic device 320 that controls the flow of current to the shunt trip coil 310 from the active power connection 325b and from either the active power connection 325a or the passive power supply 305.

In this configuration, diodes 315a-315c are still operable to prevent a short circuit between the power supplies connected to connections 325a and 325b during normal operation. By preventing any current from the passive power source 305 from flowing through the connections 325a and 325b, the diodes 315a-315c ensure that all of the energy stored in the passive power source 305 is transferred to the shunt trip coil 310 in the event of a loss of active power to the RTB remote trip device 240 b. In other words, diodes 315a and 315b are used to decouple the active power source (e.g., connection 325a or 325b) from the passive power source 305 and the shunt trip coil 310 in the event of a loss of the active power source.

This ensures that the energy stored in the passive power source 305 is not transferred to other electrical components connected to the power bus associated with the active power source. The passive power source 305 charging operation for the RTB remote trip device 240b is identical to the passive power source 305 charging operation described above with respect to the RTB remote trip device 240 a.

FIG. 4 illustrates an example reactor core configuration 400 including a neutron source 450. The neutron source 450 may comprise a device configured to provide a stable and reliable neutron source for initiating nuclear chain reactions, such as when the reactor contains a new fuel rod whose neutron flux from spontaneous fission may not otherwise be sufficient for reactor startup purposes. The neutron source 450 may be configured to provide a constant amount of neutrons to nuclear fuel when the reactor is restarted (e.g., for maintenance and/or inspection) during startup or after being shut down. In some examples, the neutron source 450 may be configured to prevent power excursions during reactor startup.

The neutron source 450 may be positioned such that the neutron flux it produces is detectable by reactor monitoring instrumentation. For example, the neutron source 450 may be inserted at regularly spaced locations inside the reactor core, for example in place of one or more fuel rods 410. Upon shutdown of the reactor, the neutron source 450 may be configured to provide a signal to the reactor monitoring instrumentation. In some examples, the steady state level of neutron flux in a subcritical reactor may depend on the intensity of neutron source 450. The neutron source 450 may be configured to provide a minimum level of neutron radiation to keep the reactor under control in a subcritical state, such as during reactor startup.

Control rods and/or fuel rods 410 may be configured to initiate reactor startup based at least in part on the inferred power level of the reactor. One or more of the control rods may be removed from the fuel rods 410 during reactor startup, causing the reactor core to become critical. In some examples, the power level of the reactor may be inferred at least in part from the number of neutrons radiated from the neutron source 450.

FIG. 5 illustrates an example reactor shutdown system 500. In some examples, the reactor shutdown system 500 may include a Reactor Trip Breaker (RTB). A power source may be used to provide power to the control rod drives and/or to the RTBs to maintain one or more control rods in a withdrawn position, such as suspended or at least partially suspended above a reactor core. The reactor shutdown system 500 may include two or more mechanisms, systems, devices, apparatuses, methods, operations, modes, and/or measures for removing power from control rod drives. The control rod drive may be configured to drive, place, insert, and/or withdraw control rods.

The reactor shutdown system 500 may be configured to lower, disconnect, release, insert, and/or drop control rods into the reactor core. In a first mode of operation, reactor shutdown system 500 may include an under-voltage trip assembly (UVTA) configured to detect, generate, notify, instruct, and/or receive a loss of voltage and/or a loss of power to the control rod drive and/or to the RTB. In some examples, loss of voltage and/or power may cause the control rod drive and/or the RTB to disconnect and/or release such that the control rod may be allowed to fall and/or otherwise be inserted into the reactor core due to gravity pulling the control rod downward.

In a second mode of operation, the reactor shutdown system 500 may include a Shunt Trip Actuator (STA) and/or a Shunt Trip Coil (STC) configured to lower, disconnect, release, insert, and/or drop a control rod into the reactor core. The shunt trip coil STC can include a circuit breaker and/or a built-in magnetic coil that can be configured to energize and trip the circuit breaker. The shunt trip coil STC may be energized by an external power source.

The shunt trip coil STC may be used as a backup shutdown system, for example, when the UVTA, the RTB, and/or the control rod drive fails to insert the control rod into the reactor core in response to a loss of voltage and/or power. For example, in response to detecting a loss of power during an active reactor trip condition, such as indicated by a Reactor Protection System (RPS), the shunt trip coil STC may be actuated to insert the control rod. In some examples, the actuation of the shunt trip coil STC may be performed using a passive energy source.

An electrical storage device, such as capacitor C1, may be used to store energy, such as electrical energy. The power storage device may include a battery, a capacitor, an ultracapacitor, other types of storage devices, or any combination thereof. In some examples, the capacitor C1 may be used to provide energy to one or more other components in the reactor shutdown system 500, such as the shunt trip coil STC.

The capacitor C1 may be configured to be charged and/or hold a charge. For example, the power supply may charge capacitor C1 during normal operation of the reactor module. Additionally, the capacitor C1 may be configured to hold a charge during the standby mode. In some examples, the power source may be configured to trickle charge capacitor C1 during the standby mode and/or otherwise ensure that capacitor C1 maintains a minimum threshold level of stored energy if a loss of power occurs and/or is detected.

The capacitor C1 may be configured to provide an alternative and/or passive source or power to actuate the shunt trip coil STC, for example, in response to a loss of normal power to the reactor shutdown system 500. In response, the shunt trip coil STC may be configured to operate the RTB to lower, drop, and/or release the control rod into the reactor core.

The reactor shutdown system 500 may include example control circuitry associated with one or more diodes, contacts, and/or capacitors that may be configured to provide a passive energy source for reactor shutdown operations. Capacitor C1 and shunt trip coil STC are shown connected to ground. In addition to the capacitor C1 and the shunt trip coil STC, the reactor shutdown system 500 may also include a first diode D1, a second diode D2, and a third diode D3.

The first diode D1 may be connected to a first voltage source Vcc. In some examples, the capacitor C1 may be charged by the first voltage source Vcc via the first diode Dl. In addition, the capacitor C1 may be discharged through the second diode D2. In some examples, the capacitor C1 is discharged in response to a loss of power at the second voltage source Vbb.

In some examples, one or both of the first diode D1 and the third diode D3 may be configured to prevent and/or protect one or more components from releasing charge stored on the capacitor Cl. Any charge discharged from the capacitor C1 may instead be directed toward the shunt trip coil STC.

The reactor shutdown system 500 may include one or more contacts, such as a first contact 510, a second contact 520, a third contact 530, a fourth contact 540, a fifth contact 550, a sixth contact 560, other contacts, or any combination thereof. In some examples, the one or more contacts may comprise Normally Closed (NC) contacts. Some or all of the contacts may be controlled by the reactor power system RPS. The RPS may be configured to open and/or close the one or more contacts in order to control charging and/or discharging of capacitor C1.

FIG. 6 illustrates an example process 600 for performing a reactor shutdown. At operation 610, a power storage device, such as a capacitor, ultracapacitor, battery, other storage device, or any combination thereof, may be charged.

At operation 620, the charge on the power storage device may be maintained during the standby mode.

At operation 630, a loss of normal operating power may be detected. In some examples, the loss of operating power may be associated with a power source used to withdraw one or more control rods from the reactor core.

At operation 640, a first shutdown system may be activated to insert the control rod. In some examples, the first shutdown system may be configured to insert the control rod into the reactor core due to gravitational pull of the control rod.

At operation 650, the reactor shutdown system may detect that the control rods have not been properly and/or fully inserted into the reactor core. For example, the control rods may remain at least partially suspended above the reactor core despite having been released by the first shutdown system at operation 640.

At operation 660, the storage device may be discharged in response to the reactor shutdown system detecting that the control rod is not inserted into the reactor core. In some examples, the charge stored in the storage device may be discharged into a shunt trip coil as part of a second shutdown system.

At operation 670, the shunt trip coil may be activated and/or powered by the storage device discharging. The shunt trip coil may in turn operate the reactor trip breaker to lower, disconnect, release, insert, and/or drop one or more control rods into the reactor core.

At operation 680, the one or more control rods may be inserted into the reactor core to shut down the reactor.

Specific embodiments of the subject matter have been described. Other embodiments, modifications, and substitutions of the described embodiments are within the scope of the appended claims, as will be apparent to those of skill in the art. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. Further, examples provided herein may be described in connection with and/or compatible with pressurized water reactors, as well as other types of power systems as described, or some modifications thereof. For example, the examples or variations thereof may also be operable for boiling water reactors, liquid sodium metal reactors, pebble bed reactors, or reactors designed to operate in space, such as a propulsion system with limited operating space. Other examples may include various nuclear reactor technologies, such as nuclear reactors employing uranium oxide, uranium hydride, uranium nitride, uranium carbide, mixed oxides, and/or other types of radioactive fuels. It should be noted that the examples are not limited to any particular type of reactor cooling mechanism, nor to any particular type of fuel used to generate heat within or associated with a nuclear reactor. Any rates and values described herein are provided as examples only. Other rates and values may be determined experimentally, for example, from the construction of a full scale or scaled model of the nuclear reactor system.

Thus, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure.

Claims (42)

1. A nuclear reactor trip apparatus, comprising:

a remote circuit breaker trip device operatively connected to the reactor trip breaker to release the control rod into the nuclear reactor core;

an active power source electrically coupled to energize the remote circuit breaker trip device;

a passive power source electrically coupled to energize the remote circuit breaker trip device based on a loss of the active power source; and

a local circuit breaker trip device operatively connected to the reactor trip breaker, including a sensor to trigger the local circuit breaker trip device upon sensing a predefined condition.

2. The nuclear reactor trip apparatus of claim 1, wherein the passive power source comprises at least one of a capacitor or a battery.

3. The nuclear reactor trip apparatus of claim 1, wherein the remote circuit breaker trip device comprises a shunt trip coil.

4. The nuclear reactor trip apparatus of claim 1, wherein the local circuit breaker trip device comprises an under-voltage trip assembly.

5. The nuclear reactor trip apparatus of claim 1, further comprising a logic device comprising:

a first terminal electrically coupled to the remote circuit breaker trip unit, an

A second terminal electrically coupled to both the active power source and the passive power source.

6. The nuclear reactor trip apparatus of claim 5, wherein the logic device is communicatively coupled to a reactor protection system.

7. The nuclear reactor trip apparatus of claim 5, wherein the logic device comprises a contactor or a solid state device.

8. The nuclear reactor trip apparatus of claim 1, further comprising:

a first logic device comprising:

a first terminal electrically coupled to the remote circuit breaker trip unit, an

A second terminal electrically coupled to the active power source; and

a second logic device comprising:

a first terminal electrically coupled to the remote circuit breaker trip unit, an

A second terminal electrically coupled to the passive power source.

9. The nuclear reactor trip apparatus of claim 8, wherein the first logic device and the second logic device are communicatively coupled to a reactor protection system.

10. The nuclear reactor trip apparatus of claim 8, wherein the first and second logic devices comprise contactors or solid state devices.

11. The nuclear reactor trip apparatus of claim 8, further comprising:

a first diode electrically coupled between the active power source and the remote circuit breaker trip unit; and

a second diode electrically coupled between the passive power source and the remote circuit breaker trip unit.

12. The nuclear reactor trip apparatus of claim 1, wherein the predefined condition comprises a loss of voltage condition.

13. A nuclear reactor trip apparatus, comprising:

a remote circuit breaker trip device comprising a shunt trip coil operatively connected to a reactor trip breaker to release a control rod into a nuclear reactor core;

a common power source powered from an active power source and electrically coupled to energize the shunt trip coil;

a capacitor acting as a passive power source electrically coupled to energize the shunt trip coil based on a loss of the ordinary power source; and

a first logic device including a first terminal electrically coupled to the shunt trip coil, and a second terminal electrically coupled to both the common power source and the capacitor.

14. The nuclear reactor trip apparatus of claim 13, wherein the first logic device is communicatively coupled to a reactor protection system.

15. The nuclear reactor trip apparatus of claim 13, wherein the first logic device comprises a contactor or a solid state device.

16. The nuclear reactor trip apparatus of claim 13, further comprising:

a second logic device comprising:

a first terminal electrically coupled to the remote circuit breaker trip unit, an

A second terminal electrically coupled to the passive power source.

17. The nuclear reactor trip apparatus of claim 16, wherein the first logic device and the second logic device are communicatively coupled to a reactor protection system.

18. The nuclear reactor trip apparatus of claim 16, wherein the first and second logic devices comprise contactors or solid state devices.

19. The nuclear reactor trip apparatus of claim 16, further comprising:

a first diode electrically coupled between the active power source and the remote circuit breaker trip unit; and

a second diode electrically coupled between the passive power source and the remote circuit breaker trip unit.

20. A method for providing a backup power source for remotely tripping a nuclear reactor trip circuit breaker, comprising:

providing a shunt trip coil operatively coupled to a reactor trip circuit breaker, the reactor trip circuit breaker electrically coupled to a reactor control rod drive assembly;

electrically coupling a common power source to the shunt trip coil;

electrically coupling a stored energy source to the shunt trip coil; and

discharging the stored energy source.

21. The method of claim 20, further comprising decoupling the common power source from the shunt trip coil based on a loss of power from the common power source.

22. The method of claim 20, further comprising closing a circuit between the stored energy source and the shunt trip coil based on a reactor trip signal.

23. The method of claim 20, further comprising charging the stored energy source from the common power source.

24. The method of claim 23, further comprising charging the stored energy source from the common power source in a standby mode.

25. The method of claim 24, further comprising maintaining a charge on the stored energy source during the standby mode.

26. The method of claim 20, further comprising detecting a loss of the common power source.

27. The method of claim 26, wherein the common power source is associated with a power source for withdrawing one or more control rods coupled to the reactor control rod drive assembly from a reactor core.

28. The method of claim 27, further comprising:

activating a first shutdown system; and

inserting the one or more control rods into the reactor core based on the activation.

29. The method of claim 28, wherein the inserting is based at least in part on a gravitational force acting on the one or more control rods.

30. The method of claim 27, further comprising detecting improper or incomplete insertion of the one or more control rods into the reactor core.

31. The method of claim 22, further comprising actuating the shunt trip coil.

32. The method of claim 22, wherein discharging the stored energy source comprises discharging the stored energy source based on detecting improper or incomplete insertion of one or more control rods into a reactor core.

33. The method of claim 22, further comprising operating the reactor trip breaker with the shunt trip coil to move one or more control rods.

34. The method of claim 33, wherein the one or more control rods are inserted into a reactor core.

35. A nuclear reactor shutdown system, comprising:

a reactor trip circuit breaker;

a control rod drive;

an under-voltage trip assembly configured to detect a loss of power to a first power source of at least one of the control rod drive or the reactor trip breaker and operate the control rod drive or the reactor trip breaker based at least in part on the detection; and

a shunt trip coil actuated by a passive power source including a capacitor electrically coupled with the shunt trip coil and configured to operate the control rod drive or the reactor trip breaker based at least in part on a failure of the under-voltage trip assembly;

wherein the capacitor is electrically coupled to a second power source through a first diode and to the shunt trip coil through a second diode.

36. The nuclear reactor shutdown system of claim 35, wherein the second power source is configured to charge the capacitor during a normal operating state.

37. The nuclear reactor shutdown system of claim 35, wherein the second power source is configured to trickle charge the capacitor during a standby state.

38. The nuclear reactor shutdown system of claim 35, wherein the first power source is electrically coupled to the shunt trip coil through a third diode, the first power source coupled to the under-voltage trip assembly to provide power to the under-voltage trip assembly.

39. The nuclear reactor shutdown system of claim 38, wherein the capacitor is discharged based on the detected loss of power from the second power source to the under-voltage trip component.

40. The nuclear reactor shutdown system of claim 35, wherein the first and second power sources comprise active power sources.

41. The nuclear reactor shutdown system of claim 35, further comprising a first set of one or more contacts electrically coupled between the second diode and the shunt trip coil to control at least one of a discharge of the capacitor to the shunt trip coil or a charge of the capacitor.

42. The nuclear reactor shutdown system of claim 41, further comprising a second set of one or more contacts electrically coupled between the first power source and the capacitor to control at least one of a discharge of the capacitor to the shunt trip coil or a charge of the capacitor.