Apparatus to switch ultrasonic signal paths in a moderately high radiation area

Abstract

The invention relates to an apparatus and methods for operation in relatively high radiation fields to remotely switch signal devices through a shared single main umbilical signal cable. The invention is particularly suitable for use in a nuclear reactor, such as a boiling water reactor, and in difficult to access areas in the reactor pressure vessel. One or more main umbilical cables connect a control station to an enclosure housing a signal switching device. The signal switching device allows several signal generating/receiving devices, such as cameras and ultrasonic probes, to be controlled by the one or more main umbilical cables.

Claims

1. An apparatus to remotely switch a signal switching device in a light water nuclear reactor, the apparatus comprising: an underwater immersible junction box, comprising: an outer surface; a cavity formed by the outer surface; a cover attachable to, and removable from, the outer surface; one or more input connectors mounted to the outer surface; and one or more output connectors mounted to the outer surface, wherein the junction box houses the signal switching device, comprising: at least one printed circuit board; and a plurality of relay switches mounted to the at least one printed circuit board; a control station remotely located from the junction box; more than one signal generating/receiving devices remotely located from the junction box and the control station; one or more output cables coupled to the one or more output connectors to connect the junction box to the more than one signal generating/receiving devices; one or more main umbilical signal cables correspondingly coupled to the one or more input connectors to connect the control station to the junction box, wherein each of the one or more main umbilical signal cables serves as a bi-directional signal cable input to the signal switching device and serves as a bi-directional signal cable output from the control station, each of the one or more main umbilical signal cables comprising a plurality of coaxial cable conductors that connect to the plurality of relay switches, wherein the control station is configured to send a single signal through the one or more umbilical signal cables to the plurality of relay switches, the single signal being configured to switch all of the plurality of relay switches mounted on each of the at least one printed circuit board, and in turn, the more than one signal generating/receiving devices, and wherein, said more than one signal generating/receiving devices are located in a radiation field of the light water nuclear reactor.

2. The apparatus of claim 1, wherein the relay switches are mounted in parallel.

3. The apparatus of claim 1, wherein the at least one printed circuit board utilizes stripline or microstrip impedance matching technology.

4. The apparatus of claim 1, wherein the more than one signal generating/receiving devices are selected from the group consisting of a camera and ultrasonic sensor.

5. The apparatus of claim 4, wherein the ultrasonic sensor is one or more phased array ultrasonic probes.

6. The apparatus of claim 1, wherein there are three input connectors mounted to the enclosure and three main umbilical signal cables correspondingly connected to the three input connectors.

7. The apparatus of claim 1, wherein there are five output connectors mounted to the enclosure and five signal generating/receiving devices correspondingly connected to the five output connectors.

8. The apparatus of claim 1, wherein the light water reactor is a boiling water reactor.

9. The apparatus of claim 1, wherein the switching device is Double Pole Double Throw (DPDT) signal switches.

10. The apparatus of claim 1, wherein the switching device is fifty ohm matched impedance signal switches.

11. The apparatus of claim 1, wherein the at least one printed circuit board contains board mounted coaxial conductor connectors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A further understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:

(2) FIG. 1 is a schematic showing an elevational view of pertinent portions of a conventional BWR;

(3) FIG. 2 is an enclosure for housing a signal switching device, in accordance with certain embodiments of the invention; and

(4) FIG. 3 is a schematic of a circuit for use in a signal switching device, in accordance with certain embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) The invention relates to apparatus and methods to remotely switch signal devices through a shared main umbilical signal cable. A main umbilical connects a control station to an enclosure, e.g., a junction box, which houses a signal switching device. The signal switching device allows several signal generating/receiving devices, e.g., cameras, ultrasonic sensors, phased array ultrasonic probes and the like, to be controlled by a main umbilical cable. Further, the device can be operated in relatively high radiation fields in which conventional multiplexer devices may not be operable.

(6) In certain embodiments, a single main umbilical cable may be employed. In other embodiments, more than one main umbilical cable can be employed.

(7) Referring to FIG. 2, there is illustrated an enclosure 10 in accordance with certain embodiments of the invention. The enclosure 10 has four walls including a first wall 12a and a second wall 12b (two of the walls are not shown), a bottom surface 14, and a top cover 16, which form a cavity 18 therein.

(8) In alternate embodiments, the enclosure can include a wide variety of shapes, such as but not limited to pyramids, octagonal, hexagonal, and cylindrical or the like. For example in the embodiment wherein the enclosure is cylindrical in shape, the enclosure includes a cylindrical tube, a removable cover, an opposing cover, a cavity formed by this structure, one or more input connectors mounted to at least one surface, and one or more output connectors mounted to at least one other surface.

(9) The enclosure 10 (as shown in FIG. 2) can be constructed of a material that is suitable for use in light water nuclear reactors, such as boiling water reactors. Therefore, the enclosure 10 is suitable for use in areas of radiation and also is suitable for immersion underwater. A signal switching device (not shown) is disposed within the cavity 18. Suitable signal switching devices for use in the invention include those known in the art which include at least one printed circuit board and a plurality of relay switches.

(10) In certain embodiments, the switching devices can include coiled relays, and can be designed for high frequency radio waves. Further, the switching devices can be Double Pole Double Throw signal switches, and can be 50 ohm matched impedance signal switches.

(11) Furthermore, the at least one circuit board can contain board-mounted coaxial conductor connectors.

(12) The top cover 16 is attachable to the four walls and is removable to insert and remove the signal switching device. The first wall 12a has mounted thereto three input connectors 20. It is contemplated that more or less input connectors 20 may be employed. One end of umbilical signal cables 24 is attached to each of the input connectors 20 and the other end of the umbilical signal cables 24 is attached to a signal control and generating console 25. The second wall 12b has mounted thereto five output connectors 22. It is also contemplated that more or less output connectors 22 may be employed. The output connectors 22 are connected to at least one signal generating/receiving device 28, such as a camera or ultrasonic sensor, via output cables 26. Also, a switch control cable 30 connects the console 25 with a connector 32 on the enclosure 10.

(13) Each main umbilical cable assembly serves as a bi-directional signal cable input to the signal switching device and serves as a bi-directional signal cable output from equipment in the control station. Each main umbilical cable can contain a plurality of coaxial cable conductors with contact dense overmolded connectors.

(14) The enclosure also facilitates a transition from small flexible micro coaxial cabling connected to the signal device, to larger coaxial cables connected to the control console. The micro-coaxial cables can be connected between the enclosure switch box and the signal device (e.g. phased array ultrasonic probe) to allow for compact design and flexible manipulator movement. However, these micro-coaxial cables results in severely attenuated excitation pulses and returning signals if utilized for long cable lengths. Therefore, larger coaxial cables may be connected between the enclosure and the control console to minimize overall signal attenuation and obtain an acceptable signal to noise ratio.

(15) The signal switch device can be of various designs and configurations known in the art. Referring to FIG. 3, there is illustrated an example of a circuit that may be utilized in the signal switching device and contained within the enclosure 10 of the invention.

(16) In certain embodiments, the invention includes the following features. There is employed an enclosure to house a signal switching device. The enclosure is suitable for use in relatively high radiation areas and can be immersed underwater. The signal switching device includes three printed circuit boards, each containing thirty-two coaxial microchip relay switches with pluggable coaxial connectors which are soldered to the printed circuit boards. The printed circuit boards utilize stripline technology and relays that match impedance for phased array applications. Metal can relay may also be used to provide shielding from outside electromagnetic interference. Individual coaxial connections at the printed circuit boards may also be utilized to provide the impedance matching and minimize the signal run lengths on the printed circuit boards. Three coaxial cables are connected to each of the relays with the opposing ends of the cables soldered to contact dense underwater connectors mounted and sealed within the enclosure. In certain embodiments, three main umbilical cable assemblies are connected to the underwater enclosure. Each main umbilical cable contains thirty-two coaxial cable conductors with contact dense overmolded under water connectors. The signal switching device also includes five contact dense underwater connectors utilized as the output from the signal switching device. These contact dense connectors are attached to the signal output device (e.g., ultrasonic sensors).

(17) The relay switches of the signal switching device are controlled remotely from the control station. The relay switches can be wired in parallel or in series to provide additional outputs for a given input. In certain embodiments, the relay switches are wired in parallel to create two outputs per each input and to minimize the risk of signal attenuation associated with each relay. In alternate embodiments, the relay switches are wired in series to split each output into an input into another relay. If two layers of relays are utilized in series, each input would utilize three relays and create four outputs. If three layers of relays are utilized in series, each input would utilize seven relays and create 8 outputs. The relays switch controls are tied together such that a single control signal will switch all of the relays on each of the printed circuit boards. Thus, only four conductors are required to control three individually controlled printed circuit boards each with 32 coaxial signal relay switches. There is one conductor for each individual control contact per board and one shared conductor for power. In an alternative embodiment, a single control conductor can be utilized to switch all relays together

(18) The signal switch device above-described illustrates an embodiment of the invention whereby three inputs, three printed circuit boards, thirty-two switches per board, five outputs are utilized and wired in parallel, and contained within an enclosure. However, it is contemplated that a wide variety of combinations of inputs, outputs, switches, or wiring in series can be utilized to accommodate the needs of specific manipulators, in accordance with other embodiments of the invention.

(19) The types of components utilized in this signal switch device are passive components with coiled relays because they are not as susceptible to radiation induced failures. Modern technology may utilize transistor-based components which are more susceptible to radiation failures. However, modern technology has reduced the size and increased the robustness of relay and printed circuit board technology which made the development and deployment of this device more feasible given the operating conditions within a nuclear reactor, such as one or more of temperature, size, power requirements and cost.

(20) While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.