Unit for removing contaminants from hydrogen gas and isotopes of hydrogen gas with features that resist damage from repeating thermal cycles

A hydrogen separator having a first end plate, a second end plate, and a cylindrical support extending from the second end plate. A permeable tube support plate is suspended by the cylindrical support, wherein the second end plate, cylindrical support and permeable tube support plate define a collection chamber. A hydrogen permeable tube is coupled to the permeable tube support plate. A housing surrounds the cylindrical support. An exhaust tube support plate is within the housing and external of the collection chamber, wherein an exhaust chamber is defined between the exhaust tube support plate and the first end plate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In general, the present invention relates to units that are used to purify hydrogen gas and isotopes of hydrogen gas in a fuel clean-up system of a nuclear reactor.

2. Prior Art Description

Nuclear fusion reactors produce various wastes as they operate. One such waste is the plasma exhaust. The plasma exhaust contains highly valuable hydrogen isotopes in addition to hydrogen and a variety of contaminants, such as oxygen, nitrogen, and carbon dioxide. Nuclear facilities use clean-up systems to recycle the hydrogen isotopes.

One widely used method of reclaiming hydrogen isotopes is through cryogenic rectification. However, the effectiveness of the cryogenic rectification can be improved if the impurities are separated from the hydrogen and the hydrogen isotopes. The removal of impurities is typically achieved by passing the subject gases through a hydrogen separator. A hydrogen separator contains a hydrogen permeable membrane made from a palladium alloy. The membrane is permeable to hydrogen and isotopes of hydrogen, but is non-permeable to contaminants. Thus, as the hydrogen and hydrogen isotopes pass through the hydrogen permeable membrane, these gases are separated from contaminants.

One of the most effective hydrogen separators available is the micro-channel separator manufactured by Power+Energy, Inc. of Ivyland, Pa. The workings of this separator are disclosed in U.S. Pat. No. 7,396,385 and its progeny. However, such hydrogen separators are not specifically designed for use in nuclear reactor clean-up subsystems. In such subsystems, there are extreme temperature fluctuations as the subsystems are brought on and off line. Such temperature fluctuations can cause slight deflections in the structure of a traditional hydrogen separator that can reduce its effectiveness and compromise its integrity over time. Any possible compromise of integrity is unacceptable when applied to a subsystem of a nuclear reactor.

A need therefore exists for an improved hydrogen separator that is better designed for use in a nuclear reactor subsystem, wherein the hydrogen separator is more robust and less susceptible to damage from thermal fluctuations. This need is met by the present invention as described and claimed below.

SUMMARY OF THE INVENTION

The present invention is a robust hydrogen separator assembly suitable for use in the reclamation of hydrogen isotopes from the plasma exhaust of a nuclear reactor. The assembly is formed as a unit having a first end plate and a second end plate. A housing extends between the first end plate and the second end plate. Inside the housing is an exhaust tube support plate. The housing has two sections that are divided by the exhaust tube support plate.

A first housing section extends from the first end plate to the exhaust tube support plate. This defines an exhaust chamber within the first housing section between said first end plate and said exhaust tube support plate. The second housing section extends from the second end plate to the exhaust tube support plate. This defines a collection chamber within the second housing section between the second end plate and the exhaust tube support plate.

Hydrogen permeable tubes are provided. The hydrogen permeable tubes have interior and exteriors. The exteriors of the hydrogen permeable tubes are exposed to the collection chamber and the interiors of said hydrogen permeable tubes are exposed to a gas intake port.

Exhaust tubes are provided that extend as cantilevers from the exhaust tube support plate. The exhaust tubes extend into the interiors of the hydrogen permeable tubes. The unit is accessed by various gas ports. An exhaust port accesses the exhaust chamber. A collection port accesses the collection chamber.

DETAILED DESCRIPTION OF THE DRAWINGS

Although the present invention unit can be embodied in many ways, only one exemplary embodiment is shown. This embodiment is selected in order to set forth one of the best modes contemplated for the invention. The illustrated embodiment, however, is merely exemplary and should not be considered a limitation when interpreting the scope of the appended claims.

Referring toFIG. 1, an overview of the unit10is shown. The unit10receives an input gas12, which is a mixture of hydrogen gas, hydrogen isotopes and various contaminant gases. The purpose of the unit10is to separate the hydrogen gas and its isotopes from the various contaminants in an efficient manner. This separation is performed by the unit either with or without the use of an inert sweep gas, such as helium.

The unit10runs at temperatures in excess of 300 degrees Celsius. The various gas tubes used to lead gases into and away from the unit10can be curved and otherwise shaped to preheat the gases leading into the unit10and cool the gases exiting the unit10. However, the unit10is often turned off, wherein it returns to ambient temperature. The cycling of temperatures creates thermal stresses in the unit10that can cause malfunctions over time. The unit10has an enhanced design that minimizes the effects of thermal cycling, therein producing a more reliable and robust unit.

Referring toFIG. 2andFIG. 3in conjunction withFIG. 1, it can be seen that a matrix of hydrogen permeable tubes16is provided. The hydrogen permeable tubes16are preferably fabricated from a palladium alloy, such as a palladium silver alloy or a palladium copper alloy. Although only two hydrogen permeable tubes16are illustrated, it should be understood that dozens or hundreds of such hydrogen permeable tubes can be manufactured into a single unit.

Each of the hydrogen permeable tubes16has a first open end18that is brazed to a hole in a tube support plate20. The first open end18leads to an interior of each hydrogen permeable tube16. The second ends22of the hydrogen permeable tubes16are sealed. The hydrogen permeable tubes16extend as cantilevers from the tube support plate20. The hydrogen permeable tubes16touch no other objects. As such, each of the hydrogen permeable tubes16is free to expand and contract with changes in temperature, without causing any significant stresses in the structure of the hydrogen permeable tubes16.

The housing of the unit10has a lower tube section26and an upper tube section28. The lower tube section26and the upper tube section28are concentrically aligned and are joined together at an exhaust tube support plate36. The upper tube section28has a length L1. The upper tube section28is covered in a top end plate30. An exhaust port32is formed through the top end plate30.

The exhaust tube support plate36is a distance D1from the top end plate30. An exhaust chamber40is disposed between the top end plate30and the exhaust tube support plate36. The exhaust port32communicates with the exhaust chamber40.

Holes are formed in the exhaust tube support plate36. Exhaust tubes44are welded to the holes. The exhaust tubes44are preferably made of stainless steel or another metal that does not react with hydrogen. The exhaust tubes44are open to the exhaust chamber40. The exhaust tubes44extend as cantilevers down into the hydrogen permeable tubes16.

A bottom end plate46seals the bottom of the lower tube section26. A collection port48extends through the bottom end plate46. A third support plate50is positioned within the lower tube section26near the bottom end plate46. The area between the third support plate50and the bottom end plate46defines an output chamber52. The collection port48communicates with the output chamber52.

Openings54are formed in the third support plate50. The hydrogen permeable tubes16pass into the openings54without touching the third support plate50. The hydrogen permeable tubes16extend into the openings54but not beyond the openings54. As such, the presence of the hydrogen permeable tubes16partially obstructs each of the openings54. This leaves small flow gaps55that control the flow rate of gases across the third support plate50.

An inner tubular element56extends upwardly from the bottom end plate46. The length of the inner tubular element56approaches the exhaust tube support plate36, but is shy, therein leaving a gap space58between the inner tubular element56and the exhaust tube support plate36. The tube support plate20is attached to the interior of the inner tubular element56. As such, the inner tubular element56supports the tube support plate20and the hydrogen permeable tubes16that extend from the tube support plate20. The space between the tube support plate20and the exhaust tube support plate36creates a supply chamber42. The supply chamber42communicates with the open tops18of the hydrogen permeable tubes16.

The inner tubular element56divides the area within the lower tube section26into two concentric chambers. They include an outer chamber60and an inner chamber62. The outer chamber60communicates with the supply chamber42. The outer chamber60is disposed between the inner tubular element56and the lower tube section26. The inner chamber62is within the inner tubular element56. The hydrogen permeable tubes16extend through the inner chamber62. An intake port64communicates with the outer chamber60.

Two helical coils are provided. The helical coils includes a first coil that is affixed to the lower tube section26and a second coil that is affixed to the exterior of the inner tube element56. The two helical coils interlace during assembly so as to become interposed between the lower tube section26and the inner tube element56within the outer chamber60. The two coils combine to create a helical baffle.

In operation, the unit10is heated to its operating temperature. Input gas12enters the outer chamber60through the intake port64. The input gas12passes through the helical baffles, wherein the input gas12is heated. The input gas12flows across the gap space58and into the supply chamber42. Once in the supply chamber42, the input gas12flows through the open tops18of the hydrogen permeable tubes16. The input gas12then flows into the gap space between the hydrogen permeable tubes16and the exhaust tubes44. This gap space is very small, therein inducing any hydrogen gas contained within the input gas12to pass through the hydrogen permeable tubes16. The contaminants remain and flow into the exhaust chamber40. The exhaust chamber40vents waste gas through the exhaust port32.

The hydrogen gas that permeates through the hydrogen permeable tubes16is collected within the inner chamber62. The hydrogen gas passes through the gaps in the third support plate50and exits the unit10through the collection port48. To reduce the partial pressure of hydrogen gas in the inner chamber62, the inner chamber62can be swept by an inert sweep gas, wherein the inert sweep gas would move any collecting hydrogen gas to the output chamber52.

As the unit10cycles between its operating temperature and ambient temperature, the various components expand and contract. These thermal cycles causes fatigue in the various components. In particular, the hydrogen permeable tubes16are particularly susceptible to damage from the stresses of thermal cycling.

The structure of the unit10is designed to minimize thermal stresses that act upon the hydrogen permeable tubes16. The hydrogen permeable tubes16are attached as cantilevers to the tube support plate20. No other strictures physically touch the hydrogen permeable tubes16. As such, the hydrogen permeable tubes16are free to expand and contract along its entire length beyond the tube support plate20. The hydrogen permeable tubes16extend into the openings54of the third support plate50but not beyond the openings54. This protects the bottom ends22of the hydrogen permeable tubes16from damage should the bottom of the unit10buckle or dent from being dropped.

The exhaust tubes44extend inside the hydrogen permeable tubes16. The exhaust tubes44extend as cantilevers from the exhaust tube support plate36. The supply tubes44are symmetrically affixed to the exhaust tube support plate36. As such, they remain straight and parallel as the exhaust tube support plate36expands with heat. Furthermore, the exhaust tube support plate36is suspended from a cylindrical wall that is uniformly round. As such, it does not cause any tilting of the exhaust tube support plate36as it heats and cools.

As the exhaust tubes44heat, they elongate. This moves the exhaust tubes44deeper into the hydrogen permeable tubes16. However, the upper tube section28also elongates. This lengthens the length L1and pulls the exhaust tubes44out of the hydrogen permeable tubes16. The net movement is close to zero. Thus, as temperatures change, the exhaust tubes44remain relatively stationary within the hydrogen permeable tubes16.

It will be understood that the embodiment of the present invention that is illustrated and described is merely exemplary and that a person skilled in the art can make many variations to that embodiment. All such embodiments are intended to be included within the scope of the present invention as defined by the appended claims.