Patent Description:
A reconversion process in a light water reactor fuel manufacturing process begins with a vaporization process, which is a unit process that converts solid UF<NUM> (uranium hexafluoride) into a gaseous state.

UF<NUM> is filled in a solid state in a cylinder and then stored in a reconversion plant, thereby being vaporized in the vaporization process and then introduced into a subsequent unit process such as a conversion process (for example, the case of a dry conversion (DC) process or an integrated dry route (IDR) process), a precipitation process (for example, the case of a ammonium uranyl carbonate (AUC) process), or a hydrolysis process (for example, the case of an ammonium uranate hydrate (AUH) process or an ammonium diuranate (ADU) process).

In the vaporization process, as shown in <FIG>, after charging a cylinder <NUM> filled with UF<NUM> into an autoclave <NUM>, and connecting the UF<NUM> gas transfer pipe (not shown) to the cylinder <NUM>, an inside of the autoclave <NUM> is heated to about <NUM> to vaporize UF<NUM>, and UF<NUM> is transferred to a reaction unit (not shown) in a subsequent process.

At this time, nitrogen gas is introduced into the autoclave <NUM> through a nitrogen supply pipe from a nitrogen supply unit <NUM>, and the nitrogen gas is heated by the heater <NUM> to heat the cylinder <NUM> and then discharged through a nitrogen discharge pipe <NUM>.

When UF<NUM> leaks to out of the cylinder <NUM>, the pipe, or process facilities during this process, it has a significant impact on safety of workers and the facilities due to generation of hydrogen fluoride (HF) that is a very toxic material in addition to uranium that is not only a radioactive material but also heavy metal.

That is, when UF<NUM> leaks and is exposed to the air, it reacts with water vapor in the air as follows to produce uranyl fluoride (UO<NUM>F<NUM>) or uranium oxyfluoride (F<NUM>OU), and hydrogen fluoride (HF).

UF<NUM>(g) + <NUM><NUM>O(g) → UO<NUM>F<NUM>(s) + 4HF(g).

In addition, UO<NUM>F<NUM> dissolves rapidly upon contact with water and generates HF as follows.

UO<NUM>F<NUM>(s) + nH<NUM>O(l) → UO2<NUM>+(aq) + 2F-(aq).

2F-(aq) + <NUM><NUM>O(l) ↔ 2HF(aq) + 2OH-(aq).

A UF<NUM> detector <NUM> configured to sense a leakage of UF6 in the vaporization process is installed at the nitrogen discharge pipe <NUM> and is able to sense whether UF6 leaks by sensing HF generated through the above reaction equations.

That is, in the case of a leak of UF<NUM> inside the autoclave <NUM>, the gas discharged through the nitrogen discharge pipe <NUM> reacts when passing through the UF<NUM> detector <NUM> with outside air that is injected into the UF<NUM> detector <NUM> to generate HF. At this time, the UF<NUM> detector <NUM> senses HF so that the administrator may recognize whether the UF<NUM> leaks.

In this process, the above-described system for sensing a UF<NUM> gas leak has a problem in that since a sensor <NUM> of the UF<NUM> detector <NUM> directly contacts highly corrosive HF, the sensor <NUM> corrodes. In addition, the above-described system has a problem in that UO<NUM>F<NUM> is also deposited on the sensor.

In order to minimize such problems, as shown in <FIG>, a bypass pipe <NUM> having an inner diameter smaller than an inner diameter of the nitrogen discharge pipe <NUM> is installed at the nitrogen discharge pipe <NUM>, and the UF6 detector <NUM> is installed at the bypass pipe <NUM>. As a result, the flow of gas flowing into the UF6 detector <NUM> may be minimized, thus minimizing damage to the UF6 detector <NUM>. However, there is a problem in that a structure becomes complicated because a separate nitrogen purge line is required to be built and the like.

In addition, there is a problem that the conduit of the bypass pipe <NUM> is narrow, whereby the conduit is blocked due to UO<NUM>F<NUM>.

In addition, since the gas discharged through the nitrogen discharge pipe <NUM> is a high-temperature gas having heated the cylinder <NUM>, there are problems that the gas causes a failure of the sensor <NUM> of the UF6 detector <NUM> and shortens a life time of the sensor <NUM>.

Accordingly, there is a problem in that the maintenance of the UF<NUM> detector <NUM> is troublesome and the maintenance cost is increased.

In order to resolve such problems, a method of allowing the gas discharged through the nitrogen discharge pipe <NUM> to react with water is also proposed, but the problem of the sensor <NUM> being corroded is not resolved, and there is a problem in that radioactive liquid waste (UO<NUM>F<NUM> aqueous solution) is generated.

Accordingly, the present disclosure has been made keeping in mind the above problems occurring in the related art, and an objective of the present disclosure is to provide a system for sensing a UF<NUM> gas leak in a nuclear fuel manufacturing process, wherein, in the case of a leakage of a UF<NUM> gas, the system allows UF<NUM> to react with UO<NUM>F<NUM> and HF by mixing outside air with the gas discharged through a nitrogen discharge pipe and senses whether UF<NUM> gas leaks by measuring UO<NUM>F<NUM> particles, a reaction product, in a non-contact manner. As a result, the system can prevent sensor failure and reduce a maintenance cost of the detector.

In order to accomplish the above objective, the present invention provides a system for sensing a UF<NUM> gas leak in a nuclear fuel manufacturing process according to claim <NUM>. The system includes: an autoclave provided with a cylinder, charged with uranium hexafluoride (UF<NUM>) in a solid state, disposed therein and with a nitrogen supply pipe and a nitrogen discharge pipe, through which nitrogen inflow and nitrogen discharge are accomplished, installed on one side and an opposite side, respectively, and vaporizing the UF<NUM> inside the cylinder through heating the nitrogen inside the autoclave; and a detection unit configured to sense whether the UF<NUM> is mixed with the nitrogen discharged after circulating inside the autoclave, thereby sensing whether the UF<NUM> leaks inside the autoclave, wherein the detection unit generates UO<NUM>F<NUM> and HF by allowing UF<NUM> to react with outside air and comprises a measuring instrument, and optically sense the generated UO<NUM>F<NUM> particles in a solid state, to allow non-contact UF<NUM> leak detection to be made.

At this time, the detection unit may include: an outside air injection pipe configured to inject outside air to be mixed with nitrogen, which is discharged from the autoclave to the nitrogen discharge pipe; and the measuring instrument configured to sense UO<NUM>F<NUM> generated when the UF<NUM> leaks.

In addition, the nitrogen discharge pipe may be provided with a filter configured to filter out the UO<NUM>F<NUM> having passed through the detection unit.

In addition, the nitrogen discharge pipe may be provided with an HF sensor configured to sense the HF having passed through the detection unit.

In addition, the measuring instrument may be a device configured to optically sense particles floating in the air.

A system for sensing a UF<NUM> gas leak in a nuclear fuel manufacturing process according to the present disclosure has the following effects.

First, there is an effect of simplifying a configuration of the system for sensing a UF6 gas leak by omitting a complicated configuration such as a bypass pipe and the like.

Second, since there is no need for direct contact between the gas discharged from an autoclave and a detection device (measuring instrument), there is an effect of preventing damage to the detection device even when there is a leak of UF<NUM> gas.

That is, the system is a non-contact type that senses UF<NUM> leakage by optically sensing solid particles of UO<NUM>F<NUM> generated through the reaction between UF<NUM> and outside air, so damage to the detection device due to corrosion and high temperature can be prevented so that a mechanical life time of the detection device can be extended, whereby there is an effect of reducing maintenance cost.

Terms and words used in present specification and claims are not limited to a conventional or dictionary meaning and should be interpreted as having a meaning and concept consistent with the technical idea of the present disclosure on the basis of the principle that an inventor may appropriately define a concept of terms in order to describe the disclosure in the best way.

Hereinafter, a system for sensing a UF<NUM> gas leak in a nuclear fuel manufacturing process according to an exemplary embodiment of the present invention will be described with reference to <FIG> and <FIG>.

Prior to the description, since a configuration and an operation of an autoclave <NUM> is a well-known technology, a detailed illustration and description will be omitted.

The system for sensing a UF<NUM> gas leak in the nuclear fuel manufacturing process is configured, as shown in <FIG> and <FIG>, to include a detection unit <NUM> and a filter <NUM> and may include an HF sensor <NUM>.

The detection unit <NUM> serves to sense in a non-contact manner whether UF<NUM> is contained in nitrogen discharged from the autoclave <NUM> and is installed at a nitrogen discharge pipe <NUM>.

The detection unit <NUM> may be installed at a main pipe of the nitrogen discharge pipe <NUM> as shown in <FIG>.

As the detection unit <NUM> is installed at the nitrogen discharge pipe <NUM>, nitrogen discharged through the nitrogen discharge pipe <NUM> is discharged via the detection unit <NUM>.

The detection unit <NUM> allows the nitrogen discharged from the autoclave <NUM> to react with the outside air, thereby sensing whether or not UF<NUM> leaks.

That is, when UF<NUM> is contained in the gas discharged through the nitrogen discharge pipe <NUM>, the UF<NUM> generates UO<NUM>F<NUM> and HF while reacting with outside air in the detection unit <NUM>.

To this end, the detection unit <NUM> includes a reaction unit <NUM> providing a reaction space, an outside air injection pipe <NUM>, which is a conduit through which injection of the outside air into the reaction unit <NUM> is accomplished, and a measuring instrument <NUM> for measuring UO<NUM>F<NUM> reacted in the reaction unit <NUM>.

The reaction unit <NUM> provides a space in which reaction of nitrogen and the outside air is accomplished in the process of discharging the high-temperature nitrogen discharged from the autoclave <NUM> through the nitrogen discharge pipe <NUM> as described above and is installed at the nitrogen discharge pipe <NUM>.

In this case, an outside air injection pipe <NUM> is installed at the reaction unit <NUM> so as to allow the outside air to be injected into the reaction unit <NUM> for the reaction of UF<NUM>.

According to the invention, the measuring instrument <NUM> serves to measure the UO<NUM>F<NUM> generated while the reaction is accomplished in the reaction unit <NUM>.

For the leakage of UF6 gas, while the sensor <NUM> electronically senses HF that is in a gaseous state conventionally, the present invention provides a technical configuration for optically measuring UO<NUM>F<NUM> that is in a solid state.

That is, in the reaction unit <NUM>, UO<NUM>F<NUM>, which is solid particles in a form of fumes, and liquid HF are generated through the reaction of UF<NUM> with outside air. At this time, by optically measuring the solid UO<NUM>F<NUM>, it is possible to sense whether UF<NUM> gas leaks.

In this case, the reaction unit <NUM> is provided of a transparent material so that an inside of the reaction unit <NUM> may be seen, and the measuring instrument <NUM> may be installed outside the reaction unit <NUM>.

Accordingly, the measuring instrument <NUM> senses whether the UF<NUM> leaks from the outside of the reaction unit <NUM> without contacting the material generated in the reaction unit <NUM>.

The measuring instrument <NUM> may be provided as a device for optically sensing particles floating in the air.

For example, the measuring instrument <NUM> may be provided as a floating particle counter or a photosensor.

Next, the filter <NUM> serves to filter out the UO<NUM>F<NUM> discharged through the nitrogen discharge pipe <NUM>, thereby preventing the conduit of the nitrogen discharge pipe <NUM> from being blocked.

That is, when UF<NUM> is contained in the nitrogen discharged through the nitrogen discharge pipe <NUM>, the conduit of the nitrogen discharge pipe <NUM> may be blocked by the UO<NUM>F<NUM> due to the generation of UO<NUM>F<NUM>, so UO<NUM>F<NUM> is filtered through the filter <NUM>, whereby the conduit of the nitrogen discharge pipe <NUM> is prevented from being blocked.

Accordingly, even when there is a leak of UF<NUM>, UO<NUM>F<NUM> particles pass through the detection unit <NUM> and are filtered by the filter <NUM>, and only nitrogen and HF are discharged passing through the filter <NUM>.

Next, the HF sensor <NUM> serves to sense the HF passing through the filter <NUM>.

The HF sensor <NUM> plays an auxiliary role in sensing whether UF6 leaks.

That is, the present invention optically senses UO<NUM>F<NUM> particles through the measuring instrument <NUM>, but when installation of the HF sensor <NUM> is parallelly established, even when a malfunction or failure of the measuring instrument <NUM> occurs, it may sense whether UF<NUM> leaks through the HF sensor <NUM>.

Hereinafter, a process of sensing a UF<NUM> leak is accomplished by the system for sensing a UF<NUM> gas leak in the nuclear fuel manufacturing process configured as described above will be described with reference to <FIG>.

The vaporization process is performed in S100 through the autoclave <NUM> of the nuclear fuel reconversion process.

Nitrogen is introduced into the autoclave <NUM>, and the nitrogen heated by the heater <NUM> heats the cylinder <NUM> filled with solid UF<NUM> to vaporize UF<NUM>.

Thereafter, the gas vaporized in the cylinder <NUM> is transferred to a subsequent process.

Next, the nitrogen that heated the cylinder <NUM> while circulating in the autoclave <NUM> is discharged in S200 through the nitrogen discharge pipe <NUM>.

At this time, the nitrogen is discharged through the reaction unit <NUM> of the detection unit <NUM> whereas the outside air is introduced into the reaction unit <NUM> in S300 through the outside air inlet pipe <NUM>.

Accordingly, the outside air and nitrogen are mixed in the reaction unit <NUM>.

At this time, when UF<NUM> leaks and being discharged with nitrogen together, UO<NUM>F<NUM> and HF are generated in S400 through the above-described reaction equations.

At this time, UO<NUM>F<NUM> is a particle in a solid state and is sensed in S500 through the measuring instrument <NUM> installed outside the reaction unit <NUM>.

In this way, when UO<NUM>F<NUM> is sensed through the measuring instrument <NUM>, the administrator is able to quickly recognize it through an alarm or light emission of warning light to perform a series of post-processing.

Meanwhile, the UO<NUM>F<NUM> and HF reacted in the reaction unit <NUM> are continuously discharged along the nitrogen discharge pipe <NUM>.

At this time, UO<NUM>F<NUM> is filtered out in S600 through the filter <NUM>, and nitrogen and HF are discharged through the filter <NUM>.

At this time, the HF sensor <NUM> senses in S700 the HF transferred through the nitrogen discharge pipe <NUM> and let the manager recognize it.

When the UO<NUM>F<NUM> is detected through the measuring instrument <NUM>, the HF will be detected also through the HF sensor <NUM>.

Even when the UO<NUM>F<NUM> is not detected due to the failure of the measuring instrument <NUM>, the UF<NUM> detection error does not occur as the HF sensor <NUM> senses the HF.

Hereby, the process of sensing the UF<NUM> leak is completed.

As described so far, the system for sensing a UF<NUM> gas leak according to the present disclosure may sense whether UF<NUM> leaks through the optical detection of the UO<NUM>F<NUM> by generating the UO<NUM>F<NUM> particles in a solid state through the reaction with the outside air.

As the UF<NUM> leak detection is performed through such a non-contact method, damage to the detection apparatus may be prevented, and the maintenance cost of the detection apparatus may be reduced.

In the above, the present invention has been described in detail with respect to the described embodiments, but it is obvious to those skilled in the art that various alterations and modifications are possible within the scope of the invention, which is defined in the appended claims.

Claim 1:
A system for sensing a UF<NUM> gas leak in a nuclear fuel manufacturing process, the system comprising:
an autoclave (<NUM>) provided with a cylinder (<NUM>), charged with uranium hexafluoride (UF<NUM>) in a solid state, disposed therein, the autoclave (<NUM>) further comprising a nitrogen supply pipe configured to provide a nitrogen inflow into the autoclave (<NUM>) and a nitrogen discharge pipe (<NUM>) configured for nitrogen discharge from the autoclave (<NUM>), wherein said nitrogen supply pipe and said nitrogen discharge pipe are installed on one side and an opposite side of the autoclave, respectively, wherein the autoclave (<NUM>) is configured to vaporize the UF<NUM> inside the cylinder (<NUM>) through heating the nitrogen inside the autoclave (<NUM>); and
a detection unit (<NUM>) installed at the nitrogen discharge pipe (<NUM>), such that nitrogen discharged through the nitrogen discharge pipe (<NUM>) is discharged via the detection unit (<NUM>), wherein the detection unit(<NUM>) is configured to sense whether the UF<NUM> is mixed with the nitrogen discharged after circulating inside the autoclave (<NUM>), thereby sensing whether the UF<NUM> leaks inside the autoclave (<NUM>),
wherein the detection unit (<NUM>) is adapted to generate UO<NUM>F<NUM> and HF by reacting UF<NUM> with outside air and wherein the detection unit (<NUM>) comprises a measuring instrument (<NUM>),
characterized in that the measuring instrument (<NUM>) is configured to optically sense the generated UO<NUM>F<NUM> particles in a solid state, to allow non-contact UF<NUM> leak detection to be made.