Patent Description:
The disclosed and claimed concept relates generally to nuclear power equipment and, more particularly, to a Dry Cask Storage System (DCSS) for storing Spent Nuclear Fuel (SNF) and having a detection apparatus.

In many state-of-the-art nuclear reactor systems, in-core sensors are employed for directly measuring the radioactivity within the core at a number of axial elevations. Thermocouple sensors are also located at various points around the core at an elevation where the coolant exits the core to provide a direct measure of coolant outlet temperature at various radial locations. These sensors are used to directly measure the radial and axial distribution of power inside the reactor core. This power distribution measurement information is used to determine whether the reactor is operating within nuclear power distribution limits. The typical in-core sensor used to perform this function is a self-powered detector that produces an electric current that is proportional to the amount of fission occurring around it. This type of sensor is generally disposed within an instrument thimble within various fuel assemblies around the core, does not require an outside source of electrical power to produce the current, is commonly referred to as a self-powered detector, and is more fully described in <CIT>, and assigned to the Assignee of this invention.

Another type of sensor capable of measuring various parameters of the core, and which is typically disposed within the instrument thimbles in various fuel assemblies around the core, is described in <CIT>. This type of sensor employs a transmitter device that includes a self-powered neutron detector structured to detect neutron flux, a capacitor electrically connected in parallel with the neutron detector, a gas discharge tube having an input end and an output end, and an antenna electrically connected to the output end in series with a resonant circuit. The input end of the gas discharge tube is electrically connected to the capacitor. The antenna is structured to emit a signal comprising a series of pulses representative of the intensity of the neutron flux monitored by the self-powered detector. Other core parameters can also be monitored by their effects on altering the values of the inductance and capacitance of the resonant circuit.

Still another in-core sensor, one which does not require signal leads to communicate its output out of the reactor, is disclosed in <CIT>, which describes an anomaly diagnosis system for a nuclear reactor core having an anomaly detecting unit incorporated into a fuel assembly of the nuclear reactor core, and a transmitter-receiver provided outside the reactor vessel. The transmitter-receiver transmits a signal wirelessly to the anomaly detecting unit and receives an echo signal generated by the anomaly detecting unit wirelessly. When the anomaly detecting unit detects an anomaly in the nuclear reactor core, such as an anomalous temperature rise in the fuel assembly, the mode of the echo signal deviates from a reference signal. Then the transmitter-receiver detects the deviation of the echo signal from the reference signal and gives an anomaly detection signal to a plant protection system. The sensor actually monitors coolant temperature around the fuel assembly in which it is mounted.

<CIT> discloses a detection apparatus that is usable with a fuel rod and an instrument timble, wherein temperature, physical elongation and ambient pressure within the fuel rod are detected.

Other difficulty has been encountered when Spent Nuclear Fuel (SNF) needs to be stored, such as after use in a nuclear reactor. It has been known to provide dry cask storage systems within which the SNF is stored. Such dry cask storage systems typically have included some type of a metallic vessel within which the SNF is situated, with the metallic vessel then being situated within a concrete overpack. Thermocouples have been situated between the vessel and the overpack in order to ascertain the temperature of the vessel, but such systems have experienced difficulty because a measurement of a temperature of a vessel from an exterior of the vessel does not necessarily provide an accurate description, for instance, a temperature within the interior of the vessel.

While each of the foregoing sensors directly monitors conditions related to a core of a nuclear reactor or a vessel of a dry cask storage system, such sensor have not been without limitation. Improvements thus would be desirable.

None of the aforementioned sensors directly monitors conditions within a nuclear fuel rod in the core during reactor operation. Before advanced fuel cladding materials can be put into commercial use they have to be rigorously tested to receive regulatory approval. The existing methodology for testing advanced fuel cladding materials requires fuel rods to be tested over several fuel cycles and examined at the end of the irradiation test. This is a lengthy process that takes several years during which time fuel cladding data is not available. In the existing method, critical data is only obtained during the post irradiation examination activities. What is desired is an in-pile sensor that can be placed within a fuel rod, endure the hazardous conditions over several fuel cycles, and does not require penetrations into the cladding of the fuel rod.

This invention achieves the foregoing objective by providing a nuclear fuel rod real-time passive integral detection apparatus with a remote inductive or magnetic interrogator (also known as pulse induction). The detection apparatus includes a resonant electrical circuit configured to be supported within an interior of a nuclear fuel rod and structured to generate a generally sinusoidal response pulse in response to an incoming excitation pulse and transmit the response pulse in the form of a magnetic wave that travels through a cladding of the nuclear fuel rod to another location within a reactor in which the nuclear fuel rod is housed, wherein a characteristic of the generated pulse is indicative of a condition of the fuel rod. The detection apparatus also includes a transmitter structured to be positioned outside the cladding, in the reactor, in the vicinity of the fuel rod and configured to generate the excitation pulse and transmit the excitation pulse through the cladding to the resonant electrical circuit, and a receiver structured to be supported within the reactor outside of the cladding, in the vicinity of the nuclear fuel rod, and configured to receive the response pulse and, in response to the response pulse, communicates a signal to an electronic processing apparatus outside of the reactor.

Preferably, the resonant circuit is supported within a plenum of the nuclear fuel rod. In one such embodiment the characteristic of the response pulse is indicative of the centerline fuel pellet temperature. In another such embodiment the characteristic of the response pulse is indicative of fuel pellet elongation. In still another such embodiment the characteristic of the response pulse is indicative of fuel rod internal pressure. Furthermore, the characteristic of the response pulse may be configured to be simultaneously indicative of a plurality of conditions of the fuel rod.

An additional resonant electrical circuit can also be located in a bottom portion of the fuel rod in order to provide measurements at two different axial locations. Preferably, the resonant circuit comprises a plurality of circuit components whose properties such as capacitance and inductance are selected to create a response pulse having a unique frequency, which can be interpreted to identify the particular nuclear fuel rod from which the generated pulse emanated.

In addition, the detection apparatus may include a calibration circuit that is configured to be supported within the interior of the nuclear fuel rod and structured to generate a static calibration signal when interrogated by the excitation pulse from the transmitter, which can be received by the receiver and used to correct the response pulse received by the receiver for any signal change associated with component degradation or temperature drift.

A further advantage is obtained by providing a dry cask storage system (DCSS) that is structured to contain therein an amount of Spent Nuclear Fuel (SNF) and which includes a detection apparatus having a resonant electrical circuit, with resonant electrical circuit being situated within an interior region of a metallic vessel wherein the SNF is situated. The detection apparatus includes a transmitter that generates an excitation pulse and transmits the excitation pulse through a metallic wall of the vessel and into the interior region. The excitation pulse causes the resonant circuit to resonate and to generate a response pulse that is in response to the excitation pulse and to transmit the response pulse through the wall to a receiver. Advantageously, the resonant circuit includes an inductor that is formed with a core whose magnetic permeability varies in a well understood fashion with temperature, with the result that the frequency of the resonant circuit varies as a function of temperature within the interior of the vessel. The frequency of the response pulse is then used to determine the temperature within the interior of the vessel where the SNF is situated.

Accordingly, an aspect of the disclosed and claimed concept is to provide an improved dry cask storage system (DCSS) structured to contain therein an amount of spent nuclear fuel (SNF). The DCSS can be generally stated as including a vessel having a wall that is formed of a metallic material and that is formed to have a first interior region, the first interior region being structured to receive therein the SNF, a overpack that is formed of a cementitious material and that is formed to have a second interior region, the vessel being received in the second interior region, a detection apparatus that is cooperable with an electronic processing apparatus that is situated outside of the DCSS, the detection apparatus can be generally stated as including a transmitter, an electrical circuit apparatus, and a receiver, the transmitter being positioned inside the second interior region and outside the vessel and being structured to generate an excitation pulse and to transmit the excitation pulse through the wall and into the first interior region, the electrical circuit apparatus having a resonant electrical circuit that is situated within the first interior region and that is structured to generate a response pulse in response to the excitation pulse and to transmit the response pulse in the form of a magnetic field signal that is structured to travel from the first interior region and through the wall, the resonant electrical circuit can be generally stated as including a plurality of circuit components, at least one circuit component of the plurality of circuit components having a property which is structured to vary in response to a condition within the first interior region and which, responsive to a change in the condition, is structured to cause the property and the response pulse to vary with the change in the condition and to be indicative of the condition, and the receiver being situated inside the second interior region and outside the vessel, the receiver being structured to receive the response pulse and to communicate to the electronic processing apparatus an output responsive to the response pulse.

A further understanding of the invention can be gained from the following Description when read in conjunction with the accompanying drawings in which:.

Similar numerals refer to similar parts throughout the specification.

An improved detection apparatus <NUM> in accordance with the disclosed and claimed concept is depicted generally in <FIG>. The detection apparatus <NUM> is usable with a fuel rod <NUM> and an instrument thimble <NUM>, such as are included in a fuel assembly <NUM> (<FIG>) of a nuclear reactor that is depicted schematically in <FIG> at the numeral <NUM>, which signifies a containment of the nuclear reactor <NUM>.

The detection apparatus <NUM> is situated within the containment of the nuclear reactor <NUM>, and the detection apparatus <NUM> is cooperable with an electronic processing apparatus <NUM> that is situated external to the containment of the nuclear reactor <NUM>. The detection apparatus <NUM> is thus intended to be situated within the harsh environment situated within the interior of the containment of the nuclear reactor <NUM> whereas the electronic processing apparatus <NUM> is situated in a mild environment external to the containment of the nuclear reactor <NUM>.

As can be understood from <FIG>, the electronic processing apparatus <NUM> can be seen as including a transceiver <NUM> and a signal processor <NUM>. The transceiver <NUM> is connected with a wired connection with an interrogation apparatus <NUM> that is situated in the instrument thimble <NUM>. The signal processor <NUM> includes a processor and storage <NUM>, with the storage <NUM> having stored therein a number of routines <NUM>, and the storage <NUM> further having stored therein a number of data tables <NUM>. The routines <NUM> are executable on the processor to cause the detection apparatus <NUM> to perform various operations, including receiving signals from the transceiver <NUM> and accessing the data tables <NUM> in order to retrieve values that correspond with aspect of the signals from the transceiver <NUM> that are representative of conditions inside the fuel rod <NUM>.

As can further be understood from <FIG>, the fuel rod <NUM> can be said to include a cladding <NUM> and to have an interior region <NUM> situated within the cladding <NUM> and a number of fuel pellets <NUM> situated within the interior region <NUM>. As employed herein, the expression "a number of" and variations thereof shall refer broadly to any non-zero quantity, including a quantity of one. The fuel rod has a plenum <NUM> in generally a vertically upper end of the fuel rod <NUM>.

The detection apparatus <NUM> can be said to include an electrical circuit apparatus <NUM> that is supported within the plenum <NUM> of the fuel rod <NUM> within the interior region <NUM> thereof The detection apparatus <NUM> further includes the interrogation apparatus <NUM>, which can be said to be situated within an interior of the instrument thimble <NUM>. As is schematically depicted in <FIG>, the electrical circuit apparatus <NUM> is situated within the interior region <NUM> and communicates with the interrogation apparatus <NUM> without any breaches or other openings being formed in the cladding <NUM>, thereby advantageously keeping the cladding <NUM> intact and advantageously keeping the fuel pellets <NUM> fully contained within the interior region <NUM>.

As can be further understood from <FIG>, and as will be set forth in greater detail below, the electrical circuit apparatus <NUM> and the interrogation apparatus <NUM> communicate wirelessly with one another. Conditions within the interior region <NUM> of the fuel rod <NUM> can be said to include a temperature of the fuel pellets <NUM>, an extent of physical elongation of the fuel pellets <NUM>, and the ambient pressure within the interior of the fuel rod <NUM>, by way of example. These three conditions are directly detectable by the electrical circuit apparatus <NUM> and are communicated through the interrogation apparatus <NUM> to the electronic processing apparatus <NUM>. As will likewise be set forth in greater detail below, various embodiments are disclosed wherein the temperature and elongation of the fuel pellets <NUM> are detected in various ways, and wherein the ambient pressure within the interior region <NUM> of the fuel rod <NUM> is detected in various ways. It is understood that these properties are not intended to be limiting.

As can be understood from <FIG>, the electrical circuit apparatus <NUM> can be said to include a resonant electrical circuit <NUM> that operates as a sensor and that includes a plurality of circuit components that include a capacitor <NUM> and an inductor <NUM>. The circuit components have values or properties, such as the capacitance of the capacitor <NUM> and the inductance of the inductor <NUM>, by way of example, which are selected to impart to the resonant electrical circuit <NUM> a unique nominal frequency which, when detected by the interrogation apparatus <NUM>, is usable to identify the particular fuel rod <NUM> within which the electrical circuit apparatus <NUM> is situated.

In this regard, it is understood that a plurality of instances of the electrical circuit apparatus <NUM> can be situated in a plurality of corresponding fuel rod <NUM> of the fuel assembly <NUM>. During operation of the detection apparatus <NUM>, the interrogation apparatus <NUM> interrogates the electrical circuit apparatus <NUM> in order to receive a signal from the electrical circuit apparatus <NUM> that can be interpreted as being indicative of one or more of the properties or conditions within the interior region <NUM> of the fuel rod <NUM>, such as temperature and/or elongation of the fuel pellets <NUM>, ambient pressure within the interior region <NUM> of the fuel rod <NUM>, etc., and by way of example. The fuel assembly <NUM> includes a large number of the fuel rods <NUM>, and a subset of the fuel rods <NUM> of the fuel assembly <NUM> are envisioned to each have a corresponding electrical circuit apparatus <NUM> situated therein. When the interrogation apparatus <NUM> sends out its interrogation signal, the various electrical circuit apparatuses <NUM>
will responsively output a signal that is transmitted through the cladding <NUM> or the corresponding fuel rod <NUM> and is received by the interrogation apparatus <NUM>. The various signals from the various electrical circuit apparatuses <NUM> each has a unique nominal frequency that is selected by selecting the various properties of the capacitor <NUM> and the inductor <NUM>, by way of example, of the electrical circuit apparatus <NUM> in order to provide such a signature frequency. The electric processing apparatus <NUM> is thus able to use the frequencies of the various detected signals to determine which signal corresponds with which fuel rod <NUM> of the fuel assembly <NUM>.

As can further be understood from <FIG>, the electrical circuit apparatus <NUM> additionally includes a resonant electrical circuit <NUM> that is usable as a calibration circuit. That is, the resonant electrical circuit <NUM> is usable as a sensor circuit that senses the property or condition within the interior region <NUM> of the fuel rod <NUM>, and the resonant electrical circuit <NUM> is usable as a calibration circuit to compensate the signal from the resonant electrical circuit <NUM> for component degradation, temperature drift, and the like. In this regard, the resonant electrical circuit <NUM> includes a capacitor <NUM> and an inductor <NUM> that are selected to have the same material properties as the capacitor <NUM> and the inductor <NUM> of the resonant electrical circuit <NUM>. However, and as will be set forth in greater detail below, the resonant electrical circuit <NUM> is exposed to the condition that is being measured within the interior region <NUM>, such as the temperature and/or elongation of the fuel pellets <NUM>, and/or the ambient pressure within the interior region <NUM>, by way of example. The resonant electrical circuit <NUM>, being usable as a calibration circuit, is generally not so exposed to the condition being measured. Such calibration is provided by employing a ratiometric analysis such as will be discussed in greater detail elsewhere herein.

As can further be understood from <FIG>, the interrogation apparatus <NUM> can be said to include a transmitter <NUM> and a receiver <NUM>. The transmitter <NUM> is configured to output an excitation pulse <NUM> which is in the form of a magnetic field signal that is capable of being transmitted through the cladding of the instrument thimble <NUM> within which the interrogation apparatus <NUM> is situated and is further capable of being transmitted through the cladding <NUM> of the fuel rod <NUM>. The excitation pulse <NUM> is thus receivable by the inductor <NUM> and the inductor <NUM> of the resonant electrical circuits <NUM> and <NUM>, respectively, to induce a resonant current in the resonant electrical circuits <NUM> and <NUM> in a known fashion. The induced currents in the resonant electrical circuits <NUM> and <NUM> result in the outputting of a response pulse <NUM> from the resonant electrical circuit <NUM> and a response pulse <NUM> from the resonant electrical circuit <NUM>. The responses pulses <NUM> and <NUM> are in the form of magnetic field signals, which are not merely radio frequency signals, and which can be transmitted from the electrical circuit apparatus <NUM> through the cladding <NUM> and through the cladding of the instrument thimble <NUM> and thus be received on the receiver <NUM>.

The excitation pulse <NUM> is of a generally sinusoidal configuration. The response pulses <NUM> and <NUM> are likewise sinusoidal pulses, but they are decaying sinusoidal signals, and it is noted that <FIG> depict a pair of traces that are representative of two different response pulses <NUM>. In this regard, the frequency of the response pulse <NUM> may correlate with one parameters within the fuel rod <NUM>, such as temperature, the peak amplitude of the response pulse <NUM> may correspond with another parameter within the fuel rod <NUM>, such as elongation of the fuel pellets <NUM>, and a decay rate of the response pulse rate <NUM> may correlate with yet another parameter within the fuel rod <NUM>, such as ambient pressure within the interior region <NUM>. As such, the response pulse <NUM> may be correlated with a plurality of parameters or conditions within the interior region <NUM> of the fuel rod <NUM> within which the electrical circuit apparatus <NUM> is situated.

The aforementioned ratiometric analysis of the response pulses <NUM> and <NUM> typically involves taking a ratio of the response pulse <NUM> to the response pulse <NUM> or vice versa, in order to eliminate the effects of component degradation and temperature drift. For instance, the resonant electrical circuits <NUM> and <NUM> may degrade over time thus affecting the signal that is output therefrom. Likewise, the signals that are output from the resonant electrical circuits <NUM> and <NUM> can vary with temperature of the nuclear reactor <NUM>. In order to compensate for these factors, it is assumed that the resonant electrical circuit <NUM> and the resonant electrical circuit <NUM> will degrade at substantially the same rate over time. Furthermore, the resonant electrical circuits <NUM> and <NUM> will be exposed to the same gross, i.e., overall, temperature within the interior of the nuclear reactor <NUM>. By taking the ratio of the response pulses <NUM> and <NUM>, such as the ratio of the frequencies, by way of example, and by using the ratio to look up in the data tables <NUM> a corresponding value for temperature, elongation, and/or pressure, the individual effects of component degradation and temperature drift in the resonant circuit <NUM> are eliminated. This is because the ratiometric signal is independent of component degradation and temperature drift since the resonant electrical circuits <NUM> and <NUM> are assumed to both experience the same component degradation and temperature drift.

As is best shown in <FIG>, the electrical circuit apparatus <NUM> further includes a elongation transmission apparatus <NUM> that is situated within the interior region <NUM> of the fuel rod <NUM>. The elongation transmission apparatus <NUM> includes a support <NUM> that is formed of a ceramic material in the depicted exemplary embodiment and which is abutted against the stack of fuel pellets <NUM>. The support <NUM> has a receptacle <NUM> formed therein, and the elongation transmission apparatus <NUM> further includes an elongated element that is in the form of a ferritic rod <NUM> and that is received in the receptacle <NUM>. The inductor <NUM> includes a coil <NUM> that is situated about and exterior surface of a tube <NUM> that is formed of a ceramic material. The tube <NUM> has an interior <NUM> within which an end of the ferritic rod <NUM> opposite the support <NUM> is receivable.

As the fuel pellets <NUM> increase in temperature, they thermally expand, thus causing the fuel pellets <NUM> to push the support <NUM> and thus the ferritic rod <NUM> in a rightward direction in <FIG>, and thus to be received to a relatively greater extent within the interior <NUM>, which alters the inductance of the inductor <NUM>. Such an alteration of the inductance of the inductor <NUM> adjusts the frequency of the resonant electrical circuit <NUM>, which is detectable when the excitation pulse <NUM> excites an electrical resonance in the resonant electrical circuit <NUM>. The response pulse <NUM> from the resonant electrical circuit <NUM> thus has a frequency that is indicative of the extent of elongation of the fuel pellets <NUM>. The response pulses <NUM> and <NUM> are received by the receiver <NUM>, and the receiver <NUM> responsively sends a number of signals to the electronic processing apparatus <NUM>. The electronic processing apparatus <NUM> uses the ratio of the response pulses <NUM> and <NUM>, or vice versa, to retrieve from the data tables <NUM> an identity of the fuel rod <NUM> within which the electrical circuit apparatus <NUM> is situated, based upon the signature nominal frequency of the response pulses <NUM> and <NUM>, and additionally retrieves from the data tables <NUM> a value that corresponds with the extent of elongation of the fuel pellets <NUM> as exemplified by the response pulse <NUM>. These data can then be sent into a main data monitoring system of the nuclear reactor <NUM>, by way of example, or elsewhere.

In this regard, it is noted that the calibration circuit represented by the resonant electrical circuit <NUM> is not strictly critical for the detection of the properties or conditions such as fuel elongation, center line fuel temperature, and ambient pressure, within the interior of the various fuel rods <NUM>. As such, it is understood that the calibration circuit <NUM> is optional in nature and is usable in order to simplify the data gathering operation and to overcome limitations associated with component degradation and temperature drift, but the calibration circuit <NUM> is not considered to be necessary to the operation of the detection apparatus <NUM>. As such, it is understood the various other types of electrical circuit apparatuses in the various other embodiments that are described elsewhere herein may or may not include a calibration circuit without departing from the spirit of the instant disclosure. In this regard, it is noted that the calibration circuit <NUM> is described only in terms of the electrical circuit apparatus <NUM>, but it is understood that any of the other embodiments of the other electrical circuit apparatuses herein may incorporate such a calibration circuit.

As suggested above, the response pulse <NUM> is a decaying sine wave that has properties such as a peak amplitude, a frequency, and a rate of decay. <FIG> depicts a trace 96A of one such response pulse <NUM>, and <FIG> depicts another trace 96B of another such response pulse <NUM>. It can be understood from <FIG> that the trace of <FIG> has a greater peak amplitude, a higher frequency (as indicated by the shorter period 98A compared with the period 98B in <FIG>), and further has a higher rate of decay than the trace 96B of <FIG>. As such, while any one of temperature, pressure, and elongation can be directly measured from the frequency of either of the traces 96A and 96B, it is understood that a plurality of such parameters can be simultaneously derived from each such trace 96A and 96B depending upon the configuration of the routines <NUM> and the data tables <NUM>, by way of example.

It thus can be said that elongation of the fuel pellets <NUM> can affect the inductance value of the inductor <NUM> by virtue of the relative movement of the ferritic rod <NUM> with respect to the coil <NUM>. This affects the frequency of the response pulse <NUM> that is output by the resonant electrical circuit <NUM>, and which is therefore detectable by the electronic processing apparatus <NUM> through the use of the routines <NUM> and the data table <NUM>.

<FIG> depicts an improved electrical circuit apparatus <NUM> in accordance with a second embodiment of the disclosed and claimed concept. The electrical circuit apparatus <NUM> includes a resonant electrical circuit <NUM> having a capacitor <NUM> and an inductor <NUM>, and is thus similar in that fashion to the electrical circuit apparatus <NUM>. However, the electrical circuit apparatus <NUM> includes a temperature transmission apparatus <NUM> that enables measurement of the center line fuel pellet temperature within the fuel rod <NUM>. Specifically, the temperature transmission apparatus <NUM> includes a modified fuel pellet <NUM> that is modified to have a receptacle <NUM> formed therein. The temperature transmission apparatus <NUM> further includes a tungsten rod <NUM> that is an elongated element and that is received in the receptacle <NUM>. While the elongated element <NUM> is depicted in the exemplary embodiment described herein as being formed of tungsten, it is understood that any of a wide variety of other refractory metals and alloys such as molybdenum and the like can be used in place of tungsten. The temperature transmission apparatus <NUM> further includes a ferritic rod <NUM> that is abutted against the tungsten rod <NUM>, it being understood that the tungsten rod <NUM> is abutted with the modified fuel pellet <NUM>. The inductor <NUM> includes a coil <NUM> that is situated directly on the ferritic rod <NUM>.

During operation, the heat that is generated by the fuel pellets <NUM> and the modified fuel pellet <NUM> is conducted through the tungsten rod <NUM> and thereafter through the ferritic rod <NUM>, thereby causing the temperature of the ferritic rod <NUM> to correspond with the temperature of the fuel pellets <NUM> and the modified fuel pellet <NUM>. The permeability of the ferritic rod <NUM> changes as a function of temperature, and the change in permeability with temperature is depicted in a graph that is shown generally in <FIG>. A portion of the graph of <FIG> is encircled and demonstrates the temperature that is typically seen by the ferritic rod <NUM> after the heat from the modified fuel pellet <NUM> is transferred to the ferritic rod <NUM> by the tungsten rod <NUM> and demonstrates, due to the steepness of the curve at the indicated location in <FIG>, the correlation between temperature of the ferritic rod <NUM> and permeability thereof.

The permeability of the ferritic rod <NUM> which, as noted, varies as a function of temperature, affects the inductance of the inductor <NUM> with the result that the frequency of the response pulse <NUM> that is output by the resonant circuit <NUM> varies directly with the permeability of the ferritic rod <NUM> and thus with the temperature of the fuel pellets <NUM> and the modified fuel pellet <NUM>. As such, the temperature of the fuel pellets <NUM> and the modified fuel pellet <NUM> can be measured by detecting the response pulse <NUM> that is output by the resonant electrical circuit <NUM> through the use of the routines <NUM> and the retrieval from the data tables <NUM> of a temperature that corresponds with the detected frequency of the response pulse <NUM>.

An improved electrical circuit apparatus <NUM> in accordance with a third embodiment of the disclosed and claimed concept is depicted in <FIG> and is usable in a fuel rod in a fashion similar to the electrical circuit apparatus <NUM>. The electrical circuit apparatus <NUM> is receivable in the interior region <NUM> of the fuel rod <NUM> and includes a resonant electrical circuit <NUM> and a temperature transmission apparatus <NUM> that detect the temperature of a set of modified fuel pellets <NUM>. The modified fuel pellets <NUM> each have a receptacle <NUM> formed therein. The temperature transmission apparatus <NUM> includes an amount of liquid metal <NUM> that is liquid during operation of the nuclear reactor <NUM>. The temperature transmission apparatus <NUM> further includes a ferritic rod <NUM> that is engaged with the liquid metal <NUM> and is buoyantly floated thereon and is receivable in the interior of a coil <NUM> of an inductor <NUM> of the resonant electrical circuit <NUM>. The liquid metal <NUM> expands and contracts with temperature increases and decreases, respectively, of the modified fuel pellets <NUM>. The position of the ferritic rod <NUM> with respect to the coil <NUM> is thus directly dependent upon the centerline temperature of the modified fuel pellets <NUM>. Such position of the ferritic rod <NUM> with respect to the coil <NUM> affects the inductance of the inductor <NUM> and therefore correspondingly affects the frequency of the resonant electrical circuit <NUM>. The response pulse <NUM> that is generated by the resonant electrical circuit <NUM> thus is receivable by the receiver <NUM> and is communicated to the electronic processing apparatus <NUM>, and the routines <NUM> and the data tables <NUM> are employed to determine a corresponding temperature of the modified fuel pellets <NUM> and thus of the corresponding fuel rod <NUM>.

<FIG> depicts an improved electrical circuit apparatus <NUM> in accordance with a fourth embodiment of the disclosed and claimed concept. The electrical circuit apparatus <NUM> is usable inside a fuel rod <NUM> and includes a resonant electrical circuit <NUM> and a pressure transmission apparatus <NUM>. The pressure transmission apparatus <NUM> is configured to enable measurement of the ambient pressure within the interior of the fuel rod <NUM> and includes a support <NUM> that abuts the stack of fuel pellets <NUM>. The pressure transmission apparatus <NUM> further includes a ferritic rod <NUM> and a vessel in the form of a bellows <NUM> having a hollow cavity <NUM> and further having a plurality of corrugations <NUM> formed therein. The hollow cavity <NUM> is open and is therefore in fluid communication with the interior region of the fuel rod <NUM>. Moreover, an end of the bellows <NUM> opposite a ferritic rod <NUM> is affixed to the support <NUM>.

The resonant electrical circuit <NUM> includes a capacitor <NUM> and further includes an inductor <NUM> having a coil <NUM> that is formed about the exterior of a hollow tube <NUM> having an interior <NUM> within which a ferritic rod <NUM> is receivable. The bellows <NUM> and the ferritic rod <NUM> are movably received on a support <NUM> and are biased by a spring in a direction generally toward the fuel pellets <NUM>.

As is understood in the relevant art, as the nuclear reactor <NUM> is in operation, fission gases are produced that include one or more noble gases. Such fission gases increase the ambient pressure within the interior region of the fuel rod <NUM>. Since the hollow cavity <NUM> is in fluid communication with the interior region of the fuel rod <NUM>, the increased pressure in the interior region <NUM> bears upon bellows <NUM> within the hollow cavity <NUM> and causes the bellows <NUM> to expand axially, thereby moving the ferritic rod <NUM> with respect to the coil <NUM> and thereby affecting the inductance of the inductor <NUM>. An increase in ambient pressure within the interior region <NUM> of the fuel rod <NUM> thus expands the bellows <NUM>, thereby resulting in an incremental further reception of the ferritic rod <NUM> into the coil <NUM>, which results in a corresponding change in inductance of the inductor <NUM>.

The corresponding change in inductance of the inductor <NUM> affects in a predictable fashion the frequency of the resonant electrical circuit <NUM> and thus likewise affects the frequency of the response pulse <NUM> that is output by the resonant electrical circuit <NUM>. As a result, when the response pulse <NUM> from the resonant electrical circuit <NUM> is received by the receiver <NUM> and is communicated to the electronic processing apparatus <NUM>, the routines <NUM> and the data tables <NUM> are employed to obtain a corresponding value for the ambient pressure within the interior region <NUM> of the fuel rod <NUM>. Such value for the ambient pressure can then be communicated to an enterprise data system of the nuclear reactor <NUM>.

An improved electrical circuit apparatus <NUM> in accordance with a fifth embodiment of the disclosed and claimed concept is depicted generally in <FIG>. The electrical circuit apparatus <NUM> is situated within an interior region <NUM> of a fuel rod <NUM> and includes a resonant electrical circuit <NUM> that includes a capacitor and an inductor <NUM>.

The electrical circuit apparatus <NUM> further includes a pressure transmission apparatus <NUM> that includes a vessel in the form of a Bourdon tube <NUM> which, in the depicted exemplary embodiment, includes a hollow tube that is formed in a helical shape. The hollow tube of the Bourdon tube <NUM> forms a hollow cavity <NUM>, except that an inlet <NUM> is formed in an end of the Bourdon tube <NUM> and thus permits fluid communication with the interior of the Bourdon tube <NUM>. More specifically, the electrical circuit apparatus <NUM> further includes a support <NUM> in the form of a seal that extends between the edges of the Bourdon tube <NUM> adjacent the inlet <NUM> and extends to an interior surface of the interior region <NUM> of the fuel rod <NUM>. The support <NUM> thus divides the interior region <NUM> into a main portion <NUM> within which a number of fuel pellets <NUM> are situated and a sub-region <NUM> within which the Bourdon tube <NUM> and the inductor <NUM> are situated. The Bourdon tube <NUM> is also supported on the support <NUM>. The support <NUM> resists fluid communication between the main portion <NUM> and the sub-region <NUM>, except for the inlet <NUM> which permits fluid communication between the interior of the Bourdon tube <NUM> and the main portion <NUM>.

The pressure transmission apparatus <NUM> further includes a ferritic rod <NUM> that is situated on the Bourdon tube <NUM> at an end thereof opposite the inlet <NUM>. The inductor <NUM> includes a coil <NUM>, and movement of the ferritic rod <NUM> in relation to the coil <NUM> changes the inductance of the inductor <NUM> such that the frequency of the response pulse <NUM> that is generated by the electrical circuit apparatus <NUM> changes corresponding to the ambient pressure within the main portion <NUM> of the interior region <NUM>. More specifically, as fission gases accumulate in the main portion <NUM> of the interior region <NUM>, the ambient pressure within the main portion <NUM> increases, as does the ambient pressure within the hollow cavity <NUM> of the Bourdon tube <NUM>. Since the sub-region <NUM> does not experience the increased ambient pressure that is experienced by the main portion <NUM>, and increase in the ambient pressure within the hollow cavity <NUM> of the Bourdon tube <NUM> results in expansion of the Bourdon tube <NUM> and resultant movement of the ferritic rod <NUM> in the direction of the arrow <NUM> with respect to the coil <NUM>. This results in a corresponding change in the frequency of the response pulse <NUM> that is generated by the electrical circuit apparatus <NUM>.

It thus can be seen that changes in ambient pressure within the main portion <NUM> of the interior region <NUM> result in a change in inductance of the inductor <NUM> and a corresponding change in the nominal frequency of the resonant electrical circuit <NUM> and a resultant change in the frequency of the response pulse <NUM> that is generated by the electrical circuit apparatus <NUM>. When such response pulse <NUM> is received by the receiver <NUM>, a corresponding signal is communicated to the electronic processing equipment <NUM>, and the routines <NUM> and the data tables <NUM> are used to obtain a corresponding value for the ambient pressure within the interior region <NUM> for output as desired.

An improved electrical circuit apparatus <NUM> in accordance with a sixth embodiment of the disclosed and claimed concept is depicted generally in <FIG>. The electrical circuit apparatus <NUM> is similar to the electrical circuit apparatus <NUM> in that a Bourdon tube <NUM> is employed as a vessel having a hollow cavity <NUM>. In the electrical circuit apparatus <NUM>, however, the Bourdon tube <NUM> includes a plug <NUM> at an end thereof opposite a ferritic rod <NUM> such that the hollow cavity <NUM> of the Bourdon tube is not in fluid communication with the interior region <NUM> of the fuel rod <NUM>, and an increase in ambient pressure within the interior region <NUM> causes the Bourdon tube <NUM> to contract. The Bourdon tube <NUM> is supported on a support <NUM> in the vicinity of the plug <NUM>, and a contraction of the Bourdon tube <NUM> due to increased ambient pressure within the interior region <NUM> thus moves the ferritic rod <NUM> in the direction of the arrow <NUM> with respect to the coil <NUM>.

The electrical circuit apparatus <NUM> includes a resonant electrical circuit <NUM> having a capacitor and an inductor <NUM>, and movement of the ferritic rod <NUM> with respect to the coil <NUM> of the inductor <NUM> changes the inductance of the inductor <NUM> and thus changes the nominal frequency of the resonant electrical circuit <NUM>. The electrical circuit apparatus <NUM> thus includes a pressure transmission apparatus <NUM> that is similar to the pressure transmission apparatus <NUM>, except that the pressure transmission apparatus <NUM> includes a Bourdon tube <NUM> whose hollow cavity <NUM> is not in fluid communication with the interior region <NUM> and thus contracts in the presence of an increased ambient pressure within the interior region <NUM>.

An improved electrical circuit apparatus <NUM> in accordance with a seventh embodiment of the disclosed and claimed concept includes a resonant electrical circuit <NUM> having a capacitor <NUM> and an inductor. The capacitor <NUM> includes a pair of plates 652A and 652B that are separated by a dielectric material <NUM>. The electrical circuit apparatus <NUM> is receivable within the interior region <NUM> of a fuel rod <NUM> in order to output a response pulse <NUM> whose frequency is adjusted responsive to a change in ambient pressure within the interior region <NUM> of the fuel rod <NUM>.

More specifically, the dielectric <NUM> is hygroscopic in nature and is configured to absorb at least some of the fission gases that are generated during operation of the nuclear reactor <NUM>. Such absorption of the fission gases by the dielectric <NUM> changes the dielectric constant of the dielectric <NUM>, which adjusts the capacitance of the capacitor <NUM>, with a corresponding effect on the frequency of the response pulse <NUM> that is generated by the resonant electrical circuit <NUM>. As such, a change in the ambient pressure within the interior region <NUM> of the fuel rod <NUM> correspondingly affects the capacitance of the capacitor <NUM> and thus likewise correspondingly affects the frequency of the response pulse <NUM> that is generated by the resonant electrical circuit <NUM>. When the response pulse <NUM> is received by the receiver <NUM>, the receiver <NUM> responsively provides to the electronic processing apparatus <NUM> a signal which is used by the routines <NUM> in conjunction with the data tables <NUM> to obtain and output a value for the ambient pressure within the interior region <NUM> of the fuel rod <NUM> within which the electrical circuit apparatus <NUM> is situated.

An electrical circuit apparatus <NUM> in accordance with an eighth embodiment of the disclosed and claimed concept is depicted generally in <FIG> as being situated within an interior region <NUM> of a fuel rod <NUM>. The electrical circuit apparatus includes a resonant electrical circuit <NUM> that includes a capacitor <NUM> and an inductor <NUM>.

The electrical circuit apparatus <NUM> includes a pressure transmission apparatus <NUM> that includes a support <NUM> upon which the capacitor <NUM> is situated in a stationary fashion and further includes a flexible seal <NUM>. More specifically, the capacitor <NUM> includes a pair of plates 752A and 752B with a dielectric material <NUM> interposed therebetween. The plate 752A is situated on the support <NUM>, and the flexible seal extends between the plate 752B and an interior surface of the fuel rod <NUM> to divide the interior region <NUM> into a main portion <NUM> within which a number of fuel pellets <NUM> are situated and a sub-region <NUM> within which the inductor <NUM>, the plate 752A, the support <NUM>, and the dielectric <NUM> are situated. The support <NUM> is rigid but has a number of openings formed therein such that an increase or decrease in the ambient pressure within the main portion <NUM> will result in movement of the flexible seal <NUM> with respect to the support <NUM>. The flexible seal <NUM> thus resists fluid communication between the main portion <NUM>, which is the location where the fission gases are generated, and the sub-region <NUM>.

When the main portion <NUM> experiences a change in the ambient pressure within the main portion <NUM>, this causes the flexible seal <NUM> and the plate 752B to move with respect to the plate 752A which, being situated on the support <NUM>, remains stationary. The dielectric material <NUM> is configured to be at least partially flexible in response to movement of the plate 752B with respect to the plate 752A. However, such movement of the plate 752B with respect to the plate 752A results in a change in the capacitance of the capacitor <NUM>. This results in a corresponding change in the frequency of the response pulse <NUM> that is generated by the resonant electrical circuit <NUM> as a result of a change in the ambient pressure within the main portion <NUM>. It thus can be understood that a change in ambient pressure within the main portion <NUM> of the interior region <NUM> correspondingly changes the frequency of the response pulse <NUM> that is received by the receiver <NUM> and which resultantly communicates a signal to the electronic processing apparatus <NUM>. The electronic processing apparatus <NUM> then employs its routines <NUM> and its data tables <NUM> to determine a pressure value that corresponds with the frequency of the response pulse <NUM> and which is indicative of the ambient pressure within the main portion <NUM> of the interior region <NUM>.

It thus can be seen that various electrical circuit apparatuses are provided that are able to directly measure parameters such as ambient pressure, centerline fuel pellet temperature, and fuel pellet elongation within the various fuel rods <NUM> of the fuel assembly <NUM>. As noted, any of the electrical circuit apparatuses can include the calibration circuit that is usable to compensate for component degradation and temperature drift. In addition to the direct measurement of the parameters such as centerline fuel pellet temperature, fuel pellet elongation, and ambient pressure within the interior region of the fuel rods <NUM>, it is reiterated that the response pulse <NUM> in certain circumstances can be analyzed in terms of its peak amplitude, frequency, and rate of decay in order to indirectly and simultaneously indicate a plurality the same parameters of the fuel rods <NUM>. Other variations will be apparent.

A first embodiment of an improved dry cask storage system (DCSS) <NUM> in accordance with the disclosed and claimed concept is depicted generally in <FIG>. The DCSS <NUM> includes a detection apparatus <NUM> that shares some similarity with the detection apparatus <NUM>. The detection apparatus <NUM> is situated internal to the DCSS <NUM> and is structured to provide an output signal to an electronic processing apparatus <NUM> that is situated external to and likely remote from the DCSS <NUM>.

The DCSS <NUM> is configured to store therein an amount of Spent Nuclear Fuel (SNF) <NUM>. More particularly, the DCSS <NUM> includes, in addition to the detection apparatus <NUM>, a vessel <NUM> within which the SNF <NUM> is situated and an overpack <NUM> that encloses therein the vessel <NUM>. The vessel <NUM> is of a roughly cylindrical configuration and is formed from a wall <NUM> that is manufactured out of a metallic material and which has a cylindrical lateral wall component and a pair of circular end wall components which are affixed together to form a sealed enclosure. In particular, the vessel <NUM> is configured to include a first interior region <NUM> that is sealed from communication with the atmosphere surrounding the DCSS <NUM>. The SNF <NUM> is received, stored, and enclosed within the first interior region <NUM>.

The overpack <NUM> can be said to include a body <NUM> that is formed of a cementitious material such as concrete and which includes a lateral annular wall component and a pair of circular end wall components that together form the body <NUM>. The overpack <NUM> is formed to have a second interior region <NUM> within which the vessel <NUM> is received. As can be understood from <FIG>, however, an annulus <NUM>, which is a region of empty space, is formed between the body <NUM> and the wall <NUM>. The body <NUM> has a number of openings <NUM> formed therein that provide communication between the annulus <NUM>, which is a part of the second interior region <NUM>, and the exterior of the overpack <NUM>.

As is best shown in <FIG>, the detection apparatus <NUM> can be said to include a transmitter <NUM> having a transmitter antenna <NUM>, a receiver <NUM> having a receiver antenna <NUM>, and an electrical circuit apparatus <NUM> that includes a resonant electrical circuit <NUM>. The resonant electrical circuit <NUM> is situated with the SNF <NUM> within the first interior region <NUM> and is enclosed therein within the vessel <NUM>. The resonant electrical circuit <NUM> includes a number of circuit components including a capacitor <NUM> and an inductor <NUM> that together form a resonant circuit when the inductor <NUM> is energized by an excitation pulse <NUM> that is generated by the transmitter <NUM> and which is similar to the excitation pulse <NUM>. Specifically, the excitation pulse <NUM> is transmitted by the transmitter antenna <NUM> through the wall <NUM> and energizes a coil <NUM> of the inductor <NUM> and, together with the capacitor <NUM>, forms a resonant circuit. It is noted, however, that the inductor <NUM> additionally includes a core <NUM> that is advantageously formed of a particular perminvar material having a high magnetic permeability and a high Curie point. In the depicted exemplary embodiment, the perminvar material used to form the core <NUM> is a high temperature NiZn perminvar ferrite material that is manufactured and sold by National Magnetics Group, Inc. , of Bethlehem, Pennsylvania, USA under the name "M3". This particular type of perminvar advantageously has a magnetic permeability that varies in a known fashion in response to a change in temperature. This relationship is similar to that depicted in <FIG> in the context of the ferritic rod <NUM>, but which is equally applicable to the core <NUM>. Since the magnetic permeability of the core <NUM> varies with temperature, the frequency of the resonant electrical circuit <NUM> advantageously correspondingly varies with temperature within the first interior region <NUM>.

When the resonant electrical circuit <NUM> is energized by the excitation pulse <NUM> that is generated by the transmitter <NUM> and that is transmitted through the wall <NUM> by the transmitter antenna <NUM>, the resonance of the resonant electrical circuit <NUM> is directly responsive to and is indicative of the temperature within the first interior region <NUM> of the vessel <NUM> where the SNF <NUM> is situated. In response to the excitation pulse <NUM> from the transmitter <NUM>, the resonant electrical circuit <NUM> becomes energized and generates a response pulse <NUM> whose frequency is based upon the resonant frequency of the resonant electrical circuit <NUM> which, as noted hereinbefore, is based upon the temperature of the first interior region <NUM> due to variable magnetic permeability of the core <NUM>. The response pulse <NUM> that is generated by the resonant electrical circuit <NUM> is similar to the response pulse <NUM> and is in the form of a decaying sine wave having properties such as peak amplitude, frequency, and rate of decay, such as is depicted generally in <FIG> in the context of the electrical circuit apparatus <NUM>. The response pulse <NUM> is transmitted in the form of a magnetic field signal that travels through the wall <NUM>, which is metallic, and is received by the receiver antenna <NUM>, which is situated within the second interior region <NUM>, but which is situated external to the vessel <NUM>. The frequency of the response pulse is optimized for transmission through the wall <NUM> and for detection by the receiver <NUM> in order to determine a temperature within the first interior region <NUM>, and in the depicted exemplary embodiment the response pulse <NUM> has a frequency that is approximately in the range of about <NUM>-<NUM>, although other frequencies can be employed without departing from the spirit of the instant disclosure.

The receiver <NUM>, in response to having received the response pulse <NUM> with the receiver antenna <NUM>, generates an output that is communicated to the electronic processing apparatus <NUM>. The output has a characteristic such as frequency that is based upon the properties of the capacitor <NUM> and the inductor <NUM>, i.e., upon the frequency of the resonant circuit that is, itself, based upon the temperature within the first interior region <NUM>. This enables a determination by the electronic processing apparatus <NUM> and from the output a temperature that exists within the first interior region <NUM>. The temperature is then communicated by the electronic processing apparatus <NUM> to, for instance, an enterprise data system or is otherwise utilized. In this regard, it is understood that the variation of the magnetic permeability of the core <NUM> as a function of temperature typically would be an undesirable property of the perminvar material from which the core <NUM> is formed, but in the instant application such variability of the magnetic permeability with temperature is advantageously employed in order to vary the resonant frequency of the resonant electrical circuit <NUM> in order to advantageously indicate the temperature within the first interior region <NUM>.

It can be understood that the receiver antenna <NUM> will receive the excitation pulse <NUM> in a fashion similar to the way in which the resonant electrical circuit <NUM> receives the excitation pulse <NUM>, except that the receiver antenna <NUM> will receive it earlier due to its closer proximity with the transmitter antenna <NUM>. The excitation pulse <NUM> is generally of much greater magnitude and energy than the detected response pulse <NUM>, and the detection apparatus <NUM> is advantageously configured to avoid destruction of the receiver <NUM> and its associated electronics due to the excitation pulse <NUM> being received by the receiver antenna <NUM>. In particular, the receiver <NUM> advantageously additionally includes a variable gain amplifier in the exemplary form of a gating circuit <NUM>, indicated at "G" in <FIG>, that is switchable between an OFF state and an ON state. The gating circuit <NUM> in the OFF state attenuates the signal that is received by the receiver antenna <NUM> by three orders of magnitude in the depicted exemplary embodiment such that if the excitation pulse <NUM> when received by the receiver antenna <NUM> would ordinarily result in an output on the order of one volt, such attenuation of that signal by three orders of magnitude would result in an attenuated signal that is on the order of a millivolt. The gating circuit <NUM> thus advantageously avoids destruction of the detection apparatus <NUM> in response to the excitation pulse <NUM>.

The gating circuit <NUM> is then advantageously switched from the OFF condition to the ON condition a predetermined period of time after initiation of the excitation pulse <NUM>. In the depicted exemplary embodiment, the gating circuit <NUM> is switched from the OFF condition to the ON condition <NUM> microseconds after the initiation of the excitation pulse, although it is understood that other predetermined periods of time greater than or less than this aforementioned period of time can be employed without departing from the spirt of the instant disclosure. After this predetermined period of time, at which point the gating circuit <NUM> is switched from the OFF condition to the ON condition, the response pulse <NUM> that is received by the receiver antenna <NUM> is communicated as an output signal to the electronic processing unit <NUM> for use in determining the temperature within the first interior region <NUM>. It thus can be seen that the gating circuit <NUM> attenuates a portion of the output from the receiver <NUM> that corresponds with the excitation pulse <NUM> but then ceases such attenuation a predetermined period of time after the excitation pulse <NUM> in order to permit the response pulse <NUM> to be detected by the receiver antenna <NUM> and to be provided as an output signal from the receiver <NUM>, with such output signal being employed as an input into the electronic processing apparatus <NUM> in order to determine the temperature within the first interior region <NUM>.

As can be understood from <FIG>, the electrical circuit apparatus <NUM>, designated with the letter "S" in <FIG> and <FIG>, is situated approximately centrally within the vessel <NUM>, and it can be understood from <FIG> that it is situated near the upper end of the SNF <NUM>. The transmitter <NUM> and receiver <NUM> are positioned within the annulus <NUM> at an optimum position with respect to the electrical circuit apparatus <NUM>. A wire <NUM> extends through one of the openings <NUM> between a transceiver that is formed by the transmitter <NUM> and the receiver <NUM> and the electronic processing apparatus <NUM>. As such, while the electrical circuit apparatus <NUM> is sealed within the first interior region <NUM> of the vessel <NUM>, the transmitter <NUM> and receiver <NUM> are situated within the annulus <NUM>, which is in communication with the exterior of the DCSS <NUM>. The electrical circuit apparatus <NUM> thus serves as a self-powered sensor that generates the response pulse <NUM> that is representative of the temperature within the first interior region <NUM>.

In contrast with the DCSS <NUM> of <FIG>, it is noted that a second embodiment of a DCSS <NUM> is depicted generally in <FIG> as including a detection apparatus <NUM> that communicates with an electronic processing apparatus <NUM>, but the detection apparatus <NUM> includes a plurality of transmitters, receivers, and electrical circuit apparatuses. More specifically, <FIG> depicts the detection apparatus <NUM> as including a plurality of transmitters that are indicated at the numerals 948A, 948B, 948C, and 948D, which may be collectively or individually referred to herein with the numeral <NUM>. The detection apparatus <NUM> further includes a plurality of receivers that are indicated generally at the numerals 956A, 956B, 956C, and 956D, and which may be collectively or individually referred to herein with the numeral <NUM>. The detection apparatus <NUM> additionally includes a plurality of electrical circuit apparatuses that are indicated at the numerals 964A, 964B, 964C, and 964D, and which may be collectively or individually referred to herein with the numeral <NUM>. Each electrical circuit apparatus <NUM> is similar to the electrical circuit apparatus <NUM> and is paired with a particular one of the transmitters <NUM> and a particular one of the receivers <NUM>. When a particular transmitter <NUM> generates an excitation pulse, similar to the excitation pulse <NUM>, its corresponding electrical circuit apparatus <NUM> generates a response pulse that is similar to the response pulse <NUM> and that is communicated in the form of a magnetic field signal through a metallic wall <NUM> of a vessel <NUM> of the DCSS <NUM> and is detected by the corresponding receiver <NUM> which generates a corresponding output that is communicated to the electronic processing apparatus <NUM>. For instance, an excitation pulse that is generated by the transmitter 948A energizes the resonant electrical circuit of the electrical circuit apparatus 964A which, in turn, generates a response pulse that is detected by the receiver 956A. In this regard, it is understood that the transmitters <NUM> will be sequentially triggered to generate the excitation pulse, one after the other, which will sequentially result in the generation of response pulses by the corresponding electrical circuit apparatuses <NUM> and resultant detection of the response pulses by the corresponding receivers <NUM> for communication to the electronic processing apparatus <NUM>. In this regard, it can be understood that the electrical circuit apparatuses <NUM> are depicted in <FIG> as being situated at various locations within the vessel of the DCSS <NUM> and are designated with "S1", "S2", "S3", and "S4". The transmitter/receiver pairs <NUM> and <NUM> are situated in the annulus between the vessel and an overpack of the DCSS <NUM>.

The detection apparatus <NUM> can employ any of a wide variety of devices and methodologies to distinguish from one another the various response pulses that are detected at the receivers <NUM>. For instance, each of the receivers <NUM> could additionally include a gating circuit, similar to the gating circuit <NUM>, which can be switched between an OFF condition and an ON condition at predetermined times with respect to the excitation pulse that was generated by the corresponding transmitter <NUM> in order to detect and communicate to the electronic processing apparatus <NUM> only the signal that was received from the corresponding electrical circuit apparatus <NUM>. Other methodologies based upon timing, signature frequency, and the like can be employed in order to distinguish the various signals that are detected by the receivers <NUM>. The positioning of the various electrical circuit apparatuses <NUM> across the vessel <NUM> advantageously permits different temperatures to be detected at different locations within the interior of the vessel <NUM>.

A third embodiment of an improved DCSS <NUM> is depicted generally in <FIG>, with an alternative configuration of a portion thereof being depicted in <FIG>. The DCSS <NUM><NUM> includes a detection apparatus <NUM> that is internal to the DCSS <NUM> and that communicates signals to an electronic processing apparatus <NUM> that is external to the DCSS <NUM>. The detection apparatus <NUM> includes a transmitter <NUM> having a transmitter antenna <NUM> and a receiver <NUM> having a receiver antenna <NUM>. The detection apparatus <NUM> further includes a plurality of electrical circuit apparatuses that are indicated generally at the numerals 1064A, 10064B, 1064C, and 1064D, and which may be collectively or individually referred to herein with the numeral <NUM>. The electrical circuit apparatuses <NUM> are similar to the electrical circuit apparatuses <NUM> and the electrical circuit apparatus <NUM>. The transmitter antenna <NUM> and the receiver antenna <NUM> together form an antenna apparatus <NUM>.

As can be understood from <FIG>, the transmitter antenna <NUM> is in the form of a number of first windings <NUM> of wire, with the first windings <NUM> being of an annular configuration. In a similar fashion, the receiver antenna <NUM> is in the form of a number of second windings <NUM> of wire that are likewise of an annular configuration, with the first and second windings <NUM> and <NUM> overlying one another. In the depicted exemplary embodiment, the transmitter antenna <NUM> is formed of a relatively thicker wire with relatively fewer windings whereas the receiver antenna <NUM> is formed of a relatively thinner wire with relatively more turns. When the antenna apparatus <NUM> is installed over a vessel <NUM> of the DCSS <NUM>, such as is depicted in <FIG>, the antennal apparatus <NUM> circumscribes a portion <NUM> of the vessel <NUM>.

As can be understood from <FIG>, the electrical circuit apparatuses <NUM> are situated at various positions within the vessel <NUM>. When the transmitter antenna <NUM> transmits an excitation pulse that is generated by the transmitter <NUM> and that is similar to the excitation pulse <NUM>, the excitation pulse energizes the resonant electrical circuits in each of the electrical circuit apparatuses <NUM>, causing each of them to generate response pulses that are similar to the response pulse <NUM> and that are communicated as magnetic field signals through a wall <NUM> of the vessel <NUM> and are detected by the receiver antenna <NUM>. The receiver <NUM> in turn generates an output that is provided to the electronic processing apparatus <NUM> and that is indicative of the various temperatures at the locations where the various electrical circuit apparatuses <NUM> are situated within the interior of the vessel <NUM>. Since the signals from the plurality of electrical circuit apparatuses <NUM> are being received by the single receiver antenna <NUM>, various techniques may be employed to distinguish one response pulse from another in order to determine which electrical circuit apparatus <NUM> generated which response pulse. For instance, frequency signatures may be employed in the various electrical circuit apparatuses <NUM>, or known time lags between generation of the excitation pulse and reception of the response pulses, or still other techniques, may be employed. It is also noted that the receiver <NUM> may include a gating circuit like the gating circuit <NUM> as needed in order to avoid destruction of the detection apparatus <NUM> due to the excitation pulse being received by the receiver antenna <NUM>.

<FIG> depicts an alternative antenna apparatus <NUM> that can be employed in the DCSS <NUM> in place of the antenna apparatus <NUM>. The antenna apparatus <NUM> includes a number of first windings <NUM> that are usable as a transmitter antenna and a number of second windings <NUM> that are usable as a receiver antenna, but the first and second windings <NUM> and <NUM> are situated side-by-side rather than overlying one another. As such, the first windings <NUM> circumscribe one portion 1174A of the vessel <NUM> whereas the second windings <NUM> circumscribe another portion 1174B of the vessel <NUM> when the antenna apparatus <NUM> is installed on the vessel <NUM>. Such a configuration can provide even greater distinction between the electrical circuit apparatuses <NUM> that are employed in the DCSS <NUM>, two of which are depicted in <FIG>.

Further advantageously, the DCSS <NUM>, the DCSS <NUM>, and the DCSS <NUM> can each incorporate any of the aforementioned structures for measuring pressure. For instance, the capacitor <NUM> can be used in place of the capacitor <NUM>, or the capacitor <NUM> can be employed in a separate resonant circuit with an inductor whose capacitance does not vary with temperature in order to provide a response pulse that is indicative of an ambient pressure within the first interior region <NUM>. Likewise, any of the aforementioned pressure transmission apparatuses <NUM>, <NUM>, <NUM>, and <NUM>, by way of example, may be incorporated into any of the detection apparatuses <NUM>, <NUM>, and <NUM> for the purpose of detecting an ambient pressure within the first interior region <NUM>. Again, such pressure transmission apparatuses <NUM>, <NUM>, <NUM>, and <NUM> could be provided, for instance, as separate devices additional to the electrical circuit apparatus <NUM>, <NUM>, and <NUM>, and which generate a separate response pulse responsive to the excitation pulse. These can be incorporated in any of a variety of fashions, such as by providing characteristic frequencies for each such pressure transmission apparatus, by way of example, or by providing separate excitation pulses that separately excite the pressure transmission apparatuses. Other examples will be apparent.

It thus can be seen that the advantageous use of the core <NUM> with a magnetic permeability that varies in a known fashion with temperature in order to detect a temperature within the interior of a vessel of a DCSS is highly advantageous. Furthermore, the incorporation of capacitor <NUM> or any of the pressure transmission apparatuses <NUM>, <NUM>, <NUM>, and <NUM> advantageously enables the detection of an ambient pressure within the interior of a vessel of a DCSS is likewise highly advantageous. Other advantages will be apparent.

Claim 1:
A dry cask storage system (DCSS) structured to contain therein an amount of spent nuclear fuel (SNF), the DCSS comprising:
a vessel having a wall that is formed of a metallic material and that is formed to have a first interior region (<NUM>), the first interior region being structured to receive therein the SNF;
a overpack (<NUM>) that is formed of a cementitious material and that is formed to have a second interior region (<NUM>), the vessel being received in the second interior region (<NUM>);
a detection apparatus (<NUM>) that is cooperable with an electronic processing apparatus (<NUM>) that is situated outside of the DCSS, the detection apparatus (<NUM>) comprising a transmitter (<NUM>), an electrical circuit apparatus (<NUM>), and a receiver (<NUM>);
the transmitter (<NUM>) being positioned inside the second interior region (<NUM>) and outside the vessel and being structured to generate an excitation pulse (<NUM>) and to transmit the excitation pulse through the wall and into the first interior region (<NUM>);
the electrical circuit apparatus (<NUM>) having a resonant electrical circuit (<NUM>) that is situated within the first interior region (<NUM>) and that is structured to generate a response pulse (<NUM>) in response to the excitation pulse (<NUM>) and to transmit the response pulse (<NUM>) in the form of a magnetic field signal that is structured to travel from the first interior region (<NUM>) and through the wall;
the resonant electrical circuit (<NUM>) comprising a plurality of circuit components, at least one circuit component of the plurality of circuit components having a property which is structured to vary in response to a condition within the first interior region (<NUM>) and which, responsive to a change in the condition, is structured to cause the property and the response pulse to vary with the change in the condition and to be indicative of the condition; and
the receiver (<NUM>) being situated inside the second interior region (<NUM>) and outside the vessel, the receiver (<NUM>) being structured to receive the response pulse (<NUM>) and to communicate to the electronic processing apparatus (<NUM>) an output responsive to the response pulse (<NUM>).