Patent Application
20130272469
1. Field
This disclosure relates generally to monitoring conditions in and around nuclear reactors during normal and off-normal operating conditions.
2. Description of Related Art
During a severe accident, a nuclear reactor, for example a boiling water reactor (BWR), may experience significant fuel damage. The fuel damage may occur as a result of a loss of coolant accident (LOCA). The damage sustained by the reactor may impede attempts to monitor environmental conditions in and around the reactor even after water is applied to cool the reactor. Presently, methods for determining conditions in and around reactors which have experienced an accident include the use of robots. It is desirable to receive information regarding the state of a reactor even after a severe accident has occurred.
One or more embodiments relate to a device for monitoring a reactor during normal and off-normal operating conditions; a reactor system including the reactor monitoring device; and/or a method of operating the reactor monitoring device.
According to at least one example embodiment, a device for monitoring a reactor may include a case formed of a rigid material, the case including a shielding layer configured to insulate an internal portion of the device from external heat and radiation; a coupling unit configured to adhere the case to a surface location of a reactor; a sensing unit configured to generate environmental measurements by measuring environmental conditions in the vicinity of the device; a data processing unit configured to generate measurement data by processing the environmental measurements; a transmitter configured to transmit the measurement data externally from the device; and a power unit configured to power the device independently of an external power source.
According to at lest one example embodiment, a reactor system may include a nuclear reactor; and one or more monitoring devices each attached to a respective surface location of the nuclear reactor. Each monitoring device may include a case formed of a rigid material, the case including a shielding layer configured to insulate an internal portion of the monitoring device from external heat and radiation; a coupling unit configured to adhere the case to a surface location of a reactor; a sensing unit configured to generate environmental measurements by measuring environmental conditions in the vicinity of the device; a data processing unit configured to generate measurement data by processing the environmental measurements; a transmitter configured to transmit the measurement data externally from the device; and a power unit configured to power the device independently of an external power source.
According to at least one example embodiment, a method of operating a reactor monitoring device affixed to a reactor structure, the reactor including a sensing unit, a transmitter and a controller, may include initializing, at the controller, an operation mode of the reactor monitoring device in a standby mode. Standby mode may be a mode in which the sensing unit performs intermittent environmental measurements of the reactor structure and sends the environmental measurements to the controller. The method may further include determining, at the controller, whether normal or an off-normal operating conditions exist in the reactor structure based on at least one of the environmental measurements and movement measurements indicating movement of the reactor monitoring device. The method may further include maintaining the operation mode as the standby mode if normal operating conditions exist; and changing the operation mode of the reactor to an active mode if off-normal operating conditions exit. The active mode may be a mode in which the sensing unit performs continuous environmental measurements of the reactor structure, the sensing unit sends the environmental measurements to the transmitter, and the transmitter wirelessly transmits the environmental measurements to an external location.
The various features and advantages of the non-limiting embodiments herein may become more apparent upon review of the detailed description in conjunction with the accompanying drawings. The accompanying drawings are merely provided for illustrative purposes and should not be interpreted to limit the scope of the claims. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. For purposes of clarity, various dimensions of the drawings may have been exaggerated.
It should be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “covering” another element or layer, it may be directly on, connected to, coupled to, or covering the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout the specification. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It should be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments.
Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like) may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Located on the reactor structure 110 are one or more monitoring devices 130. In the example embodiment illustrated in
First through third monitoring devices 130A-C are each configured to generate environmental measurements by monitoring environmental conditions of the reactor structure 110 in and around the positions at which the first through third monitoring devices are located. The monitoring devices 130A-C are also capable of measuring movement conditions including, for example, speed and/or acceleration. First through third monitoring devices 130A-C are each located at different positions in the reactor structure 110 so that environmental and/or movement measurements may be generated from different locations within the reactor structure 110. The first through third monitoring devices 130A-C are each configured to transmit data representing the environmental and/or movement measurements to the receiver station 120 where a plant operator can review the environmental and/or movement measurements. For example, according to at least one example embodiment, the first through third monitoring devices 130A-C may each generate environmental data by digitizing the environmental measurements. The first through third monitoring devices 130A-C may then broadcast the environmental data, using low-frequency radio waves, for reception at one or more locations outside the reactor structure including, for example, the receiving station 120.
Further, first through third monitoring devices 130A-C are each structured to operate during normal and off-normal operating conditions. As used herein, normal operating conditions refer to operating conditions during which none of the movement or environmental measurements generated by the first through third monitoring device 130A-C are above threshold values determined according to the preference of a plant operator. As used herein, off-normal operating conditions refer to conditions in which any of the movement or environmental measurements generated by first through third monitoring devices 130A-C are above the threshold values determined according to the preference of a plant operator. Off-normal operating conditions may be associated with any of a number of plant transients ranging from less severe events, including elevated reactor pressure or temperature, to very severe events including, for example, a loss of coolant accident (LOCA).
First through third monitoring devices 130A-C each include independent power units, and are each configured to resist the extreme amounts of heat, radiation and/or physical force associated with severe off-normal operating conditions including, for example, conditions during a LOCA. Accordingly, first through third monitoring devices 130A-C are configured to generate and transmit data representing the environmental conditions in the reactor structure 110 even during or after a reactor accident. The structure and operation of the first through third monitoring devices 130A-C will be discussed in greater detail below with reference to
Returning to
Consequently, using the reactor system 100 according to at least one example embodiment, operators at locations outside the reactor structure 110, including for example the receiving station 120, can receive valuable information regarding conditions at multiple locations inside the reactor structure 110, even during or after a reactor accident including, for example, a LOCA. An example of the reactor structure 110 and locations within the reactor structure 110 where the first through third monitoring devices 130A-C can be located will now be discussed in greater detail with reference to
First through third positions 270A-270C illustrated in
Referring to
According to at least one example embodiment, the case 305 encloses and holds the movement measurement unit 312, sensing unit 315, data processing unit 320, transmitter 325, power unit 330, and controller 335. The case 305 may be formed of any rigid material capable of resisting deformation while experiencing extreme physical force including, for example, stainless steel, aluminum, lead, uranium, or similar material.
The shielding material 307 may be part of the case 305 or may be affixed to the inside of the rigid case 305. The shielding material 307 may be any material which insulates the inner portion of the first monitoring device 130A from external heat and/or radiation. For example, the shielding material 307 may include one or more of uranium, tungsten, lead, and sintered nanoparticles.
The coupling unit 310 affixes the case 305 to a surface of a reactor structure being monitored by the first monitoring device 130A. For example, in
The movement measurement unit 312 includes hardware and/or software for making measurements regarding movement of the first monitoring device 130A including, for example, speed and/or acceleration. According to at least one example embodiment the movement measurement unit 312 is configured to output a movement signal 316. According to at least one example embodiment, the movement measurement unit 312 may compare movement measurements of the first monitoring device 130A to a movement threshold and output the signal 316 as an excessive movement signal indicating whether or not the movement measurements of the first monitoring device 130A exceed the movement threshold. Alternatively, the movement signal 316 may be a movement value signal indicating a speed and/or acceleration value of the first monitoring device 130A. The movement threshold may be stored in the movement measurement unit 312. The movement threshold may be set, for example, according to the preference of a plant operator. For example, the movement measurement unit 312 may include an element having the structure and/or operation of any know accelerometer for determining the speed and/or acceleration value of the first monitoring device 130A.
According to at least one example embodiment the movement measurement unit 312 may be connected to the controller 335 and provide the movement signal 312 to the controller 335. Additionally, the measurement unit 312 may also be connected to the data processing unit 320.
The sensing unit 315 includes hardware and/or software for performing environmental measurements. The environmental measurements the sensing unit 315 is capable of measuring may include, for example, any of a surface temperature of the first monitoring device 130A, a surface temperature of the surface location of the reactor, a radiation level around the first monitoring device 130A, and air pressure around the first monitoring device 130A.
For example, the sensing unit 315 may include any of one or more B-type thermo couples configured to measure a surface temperature of the monitoring device 130A, an infrared (IR) temperature measuring device configured to measure the surface temperature of the surface location of the reactor to which the first monitoring device 130A is affixed, a radiation collimator configured to measure at least one of gamma rays and neutrons, and a pressure gauge configured to measure air pressure in the vicinity of the device. Further, the case 305 and shielding layer 307 may include ports 350 and 355 to facilitate the taking of measurements by the instrumentation included in the sensing unit 315. For example, ports 350 may include openings and/or indentations in the case 305 and shielding layer which facilitate the measurements of radiation, surface temperature and local reactor temperature. As another example, the case 305 and shielding layer 307 may include an opening 355 to facilitate the taking of pressure measurements by the sensing unit 315. For example, the port 355 could be connected to a bourdon tube pressure gauge 360.
According to at least one example embodiment each of the one or more monitoring devices 130 may include sensing units 315 configured to take the same types of environmental measurements (e.g., radiation measurements, reactor temperature measurements, surface temperature measurements, pressure measurements, etc). Alternatively, according to at least one other example embodiment, each of the monitoring devices 130 may be configured to monitor different types of environmental data based on a region within a reactor structure at which the monitoring device is to be located. For example, referring to
As is illustrated in
The data processing unit 320 processes received measurements and outputs processed measurement data 322. For example, the data processing unit 320 may process the environmental measurements 317 received from the sensing unit 315. The processing performed by the data processing unit 320 may include, for example, at least one of analog-to-digital conversion, and encryption. According to at least one example embodiment, the data processing unit 320 includes hardware and/or software capable of performing analog-to-digital conversion. For example, the data processing unit 320 may include an analog-to-digital function which converts the environmental measurements 317, which may be received from the sensing unit 315 in analog form, to digital form. The analog-to-digital function may also organize the generated digital data according to the type of measurement the data is associated with such that the different types of digital data (e.g., radiation data, reactor temperature data, surface temperature data, pressure data, etc) are represented in a uniform and organized manner. Further, according to at least one example embodiment, the data processing unit 320 may also include hardware and/or software capable of performing data encryption. For example, the data processing unit 320 may include an encryption function which encrypts the digital measurement data generated by the analog-to-digital conversion function. According to at least one example embodiment, the measurement data may be encrypted to help ensure that only intended recipients are able to read the measurement data. Intended recipients include, for example, the receiving station 120 illustrated in
The transmitter 325 transmits the measurement data 322 outward from the first monitoring device 130A wirelessly. The transmitter 325 may transmit the measurement data 322 using radio signals. For example, the transmitter 325 may transmit the measurement data 322 using low frequency (LF) or ultra low frequency (ULF) radio signals ranging from 300 Hz to 300 kHz. The transmitter 325 may include, for example, any known device capable of transmitting data using low frequency radio waves. Low frequency radio waves may be any radio waves low enough to penetrate the infrastructure of a reactor structure to which the first monitoring device 130A is affixed.
The power unit 330 provides any power necessary for the operation of the sensing unit 315, data processing unit 320, transmitter 325 and controller 335. According to at least one example embodiment, the power unit 330 is capable of operating independently from any power source external to the first monitoring device 130A. For example, the power unit 330 may include one or more batteries and/or fuel cells.
According to at least one example embodiment, in order to prolong the lifespan of the power unit 330, one or more elements within the first monitoring device 130A are capable of operating in at least two operation modes: standby and active. The operation modes may be controlled by, for example, the controller 335.
The controller 335 includes hardware and/or software for generating control signals 340 to control an operation mode of one or more of the sensing unit 315, data processing unit 320, transmitter 325 and power unit 330. The operation modes include at least a standby mode for operation during normal, operating conditions, and an active mode for operation during off-normal operating conditions. The controller 335 is capable of selecting an operation mode based on whether or not the reactor structure to which the first monitoring device 130A is affixed is experiencing off-normal conditions including, for example, a LOCA. For example, the controller 335 may receive environmental measurement data 322 from the data processing unit 320, and/or movement signal 316 from the movement measurement unit 312 and determine whether or not off-normal conditions exist based on the measurement data 322 and/or the movement signal 316. The controller 335 may then set the operating condition to standby if normal conditions exist, and set the operation mode to active if off-normal operating conditions exist. The controller 335 may determine whether or not off-normal conditions exist by comparing the measurement data 322, and/or movement measurement indicated by the movement signal 316, to threshold values internally stored in the controller 335. The threshold values may be set according the preference of a plant operator.
Further, if the movement signal 316 generated by the movement measurement unit 312 exceeds the movement threshold stored in the movement measurement unit 312, the controller 335 may change the operating condition from standby to active, for example, based on the movement signal 316 without comparing the movement signal 316 to an internal threshold stored in the controller 335.
Accordingly, the controller 335 is capable of changing the operating state of the first monitoring device 130A from standby to active based on either of the movement signal 316 and the measurement data 322.
In standby mode the controller 335 may control one or more elements within the first monitoring device 130A to operate less often or intermittently in order to conserve power during normal operating conditions. In active mode, the controller 335 may control one or more elements within the first monitoring device 130A to operate more often or continuously. Accordingly, in active mode, the first monitoring device 130A may provide, for example, constant, real-time measurement data to, for example, plant operators at external locations including the receiving station 120 illustrated in
According to at least one example embodiment, in standby mode, the sensing unit 315 may operate intermittently providing environmental measurements 317, for example, once every 1-5 minutes, and the data processing unit 320 may operate intermittently corresponding to the operation of the sensing unit 315. Further, in standby mode, the data processing unit may provide data only to the controller 335 and not the transmitter 325, and the transmitter 325 may not transmit data at all. Further, in standby mode the power unit 330 may be configured to produce a lower power output in comparison to active mode. Additionally, the movement measurement unit 312 may operate continuously even in standby mode.
According to at least one example embodiment, in active mode, the sensing unit 315 may operate continuously generating environmental measurements 317 constantly, and the data processing unit 320 may operate continuously constantly processing the environmental measurements 317 to generate the measurement data 322. Further, in active mode, the data processing unit 320 may provide the measurement data 322 to the transmitter 325, and the transmitter 325 may continuously transmit the measurement data using, for example, low frequency radio waves. Further, in active mode the power unit 330 may be configured to produce a higher power output in comparison to the standby mode. Additionally, the movement measurement unit 312 may maintain a continuous manner of operation in active mode.
Accordingly, by utilizing the standby and active modes of operation, the first monitoring device 130A may function for extended periods of time even while using an independent power source. According to at least one example embodiment, the sensing unit 315, data processing unit 320, transmitter 325, controller 335, and power unit 330 are configured to provide a standby life span equal to at least 1.5 times the length of a refueling cycle of a reactor being monitored by the first monitoring device 130A.
The operations and functional processes discussed above with respect to the movement measurement unit 312, the sensing unit 315, data processing unit 320, transmitter 325, controller 335, and power unit 330 may be implemented using hardware including, for example, one or more digital signal processors (DSPs), application-specific-integrated-circuits, field programmable gate arrays (FPGAs) or the like. A method of operating the first monitoring unit 130A will now be discussed in greater detail below with reference to
Referring to
After initialization, the first monitoring device 130A detects the presence of off-normal operating conditions by monitoring environmental measurements generated by the sensing unit 315 and/or movement measurements generated by the movement measurement unit 312. The process of monitoring environmental measurements will be discussed below with reference to steps S420 and S430. The process of monitoring movement measurements will be discussed below with reference to steps S432 and S435. According to at least one example embodiment, steps S420 and S430 are executed in parallel with steps S432 and S435. Accordingly, the presence of off-normal operating conditions can be determined based on either the environmental measurements generated by the sensing unit 315 or the movement measurements generated by the movement measurement unit 312, for example, independently of one another.
In step S420, the first monitoring device 130A performs intermittent environmental measurements. For example, because, in step S410, the controller 335 outputs control signals 340 controlling the sensing unit 315 and data processing unit 320 to operate in a standby operation mode, as is discussed above with reference to
In step S430, the first monitoring device 130A determines whether or not the measurement data indicates the existence of off-normal operating conditions in the reactor structure 110. For example, the controller 335 may store threshold values corresponding to each type of measurement data (e.g., reactor surface temperature, monitoring device surface temperature, radiation level, pressure level, etc.). Further, the controller 335 may compare one or more of the types of measurement data received from the data processing unit 320 to corresponding threshold values stored within the controller 335.
According to at least one example embodiment, if no value of any of the one or more compared types of measurement data exceeds the corresponding threshold value stored in the controller 335, the first monitoring unit 130A returns to step S420, maintains the standby state as the operating state of the first monitoring device 130A, and continues generating and processing the measurement data 317 intermittently.
According to at least one example embodiment, if a value of any of the one or more compared types of measurement data does exceed the corresponding threshold value stored in the controller 335, the first monitoring unit 130A proceeds to step S440.
In step S432, the first monitoring device 130A performs movement measurements. For example, the movement measurement unit 312 may perform measurements regarding the movement of the first monitoring device 130A and generate the movement signal 316 based on the measurements. The movement measurement unit 312 may output the movement signal 316 to the controller 335.
In step S435, the first monitoring device 130A may determine whether or not movement measurements performed by the movement measurement unit 312 indicate off-normal operating conditions. For example, the movement signal 316 may be a measurement signal which includes data indicating a value of the movement measurements performed by the movement measurement unit 312. The controller 335 may compare the values indicated by the movement signal 316 to a threshold value stored in the controller 335 and determine that off-normal operating conditions exist if the values exceed the threshold. Alternatively, the movement measurement unit 312 may compare the movement measurements to a threshold value stored in the movement measurement unit 312, and generate the movement signal 316 as an excessive movement signal based on the comparison. The excessive movement signal may have, for example, two values including a first value indicating that the movement measured by the movement measuring device 312 does not exceed the movement threshold, and a second value indicating that the movement measured by the movement measuring device 312 exceeds the movement threshold. The controller 335 may determine that off-normal operating conditions exist if the value of the movement signal 316 indicates that the measured movement exceeds the movement threshold.
According to at least one example embodiment, if the measured movement indicated by the movement signal 316 does not exceed the corresponding threshold value stored in the controller 335, or the movement signal 316 has a value indicating that that the movement measured by the movement measuring device 312 does not exceed the movement threshold stored in the movement measurement unit 312, the first monitoring unit 130A returns to step S432, and maintains the standby state as the operating state of the first monitoring device 130A, and continues monitoring the movement measurements performed by the movement measurement unit 312.
According to at least one example embodiment, if the measured movement indicated by the movement signal 316 does exceed the corresponding threshold value stored in the controller 335, or the movement signal 316 has a value indicating that that the movement measured by the movement measuring device 312 does exceed the movement threshold stored in the movement measurement unit 312, the first monitoring unit 130A proceeds to step S440.
In step S440, the first monitoring device 130A changes the operation state of the first monitoring device 130A from standby to active. For example, the controller 335 ceases outputting standby control signals and starts outputting active control signals as control signals 340.
In step S450, the first monitoring device 130A performs continuous environmental measurements and transmits measurement data to the receiving station 120. For example, because, in step S440, the controller 335 began outputting active signals as control signals 340, each of the sensing unit 315, data processing unit 320, transmitter 325, controller 335, and power unit 330 are controlled to be in an active operation mode as is discussed above with reference to
While a number of example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
