JPH0452599A - Apparatus for treating gaseous waste - Google Patents

Abstract

PURPOSE:To suppress the discharge quantity of radioactivity at the time of an accident to the min. by making the total length of each of a plurality of activated carbon type rare gas hold-up towers arranged in series long toward the tower on the downstream side. CONSTITUTION:Activated carbon type rare gas hold-up towers 10 - 13 are successively connected in series and an exhaust particle filter 14 and an exhaust gas vacuum pump 15 are connected on the downstream side of the towers to discharge treated gas to the atmosphere through a main exhaust cylinder 16. In the region reaching the tower 13 from the tower 10, the body parts of the towers are successively made long from the tower 10 toward the tower 13 positioned on the downstream side in order to secure a long holding time because radioactive rare gas is decayed toward the downstream direction to be reduced in its radioactivity. By this constitution, the holding time of the rare gas required as a plant is distributed to the respective towers 10 - 13 in the optimum manner to equalize the holding quantity of the radioactive dilute gas. Even if the breakage in connection piping is supposed, the rare gas discharged to the outside becomes the same amount and the discharge amount of radioactivity at the time of an accident can be suppressed to the min.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a gaseous waste treatment device installed in a nuclear power plant.

(Conventional technology) Gaseous waste treatment equipment at nuclear power plants uses activated carbon to adsorb rare gases, which are nuclear fission products that move from the reactor to the turbine together with the main steam, and retains them for a certain period of time to remove radioactive rare gases over time. It is arranged to attenuate and reduce the amount of radioactive noble gas before releasing it to the outside. For this purpose, the total amount of activated carbon to be loaded is about 20 to 30.

In conventional gaseous waste treatment systems, this activated carbon is evenly distributed and loaded into multiple activated carbon hold-up towers.

(Problem to be solved by the invention) If activated carbon is loaded evenly into multiple activated carbon hold-up towers, the retention time of the rare gas in each tower becomes equal, but the decay of the radioactive rare gas is exponential. , the amount of radioactive noble gas retained in the first, most upstream column is greater than the amount of radioactive noble gas in the other downstream columns.

One of the safety evaluations of nuclear power plants is the evaluation of damage to gaseous waste treatment facilities. This assumes a rupture in the pipes of a gaseous waste treatment system, and evaluates the amount of exposure to the general public in the event that rare gases flowing out of the system are released into the environment.

A safety assessment is being conducted assuming that this accident was a rupture in the inlet piping of the first activated carbon holding up tower.
Since the amount of radioactive rare gas held in the first tower is larger than that in the other towers, if the inlet pipe of the first tower were to break, the rare gas held in the first tower would be desorbed from the activated carbon and piped into the pipe. This is because it is thought that it will appear in

Since the amount of rare gas held in activated carbon holding up towers differs depending on the tower, it is necessary to assume that the inlet piping of the tower that holds the most amount will be ruptured. Although the number was low enough, it was relatively high compared to other accidents.

The present invention aims to reduce the amount of rare gas that would be released in the event of a pipe rupture in a gaseous waste treatment system designed to equalize the amount of rare gas held in a plurality of activated carbon hold up towers. The aim is to reduce the amount of radiation exposure to the general public in the event of an accident.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the gaseous waste treatment apparatus of the present invention is characterized in that the total length of the activated carbon hold-up towers arranged in series is made longer as the towers are located on the downstream side. shall be.

(Function) In the gaseous waste treatment equipment configured in this way, the amount of radioactive rare gas held by each activated carbon holding up tower is equal, so even if any of the pipes connected to them is ruptured, the The amount of radioactive noble gas used can be made equal.

(Example) FIG. 1 is a system diagram showing an embodiment of the present invention.

A condenser air extractor 2 and a steam type air extractor 3 for starting and stopping are connected in parallel to a pipe 1 led from a turbine condenser. On the downstream side, there is an exhaust gas preheater 4. Exhaust gas recombiner5. Exhaust gas condenser6. Exhaust gas precooler7. Exhaust gas dryer8. Prefilters 9 are connected in sequence.

Furthermore, on the downstream side, there are activated carbon rare gas hold up towers: a first tower 10, a second tower 11. Third Tower 12. It is connected in series with the fourth column 13. Further, on the downstream side of this fourth tower 13, an exhaust gas particle filter 14. An exhaust gas vacuum pump 15 is connected. The treated gas is then released into the atmosphere through the main exhaust stack 16.

Note that the number of columns differs depending on each plant design, but in this example, the case of 4 columns is described. Of course it will be done.

Activated carbon type rare gas hold up towers are from the first tower 10 to the fourth tower.
Up to the tower 13, the barrel becomes longer as it is located downstream. This is because the radioactive noble gas decays as it goes downstream and decays as radioactivity.
This ensures a longer retention time. In this way, the rare gas retention time required by the plant is optimally distributed to each hold up tower, and the amount of radioactive rare gas retained is equalized.

The reason we changed only the length of the body of the activated carbon hold-up tower was because it was more economical to design and manufacture the container by making the upper and lower hemispheres the same, and also because it was more economical to design and manufacture the container. This is to make the cross-sectional area of the column the same in each column and maintain the optimum flow rate of the rare gas.

〔Effect of the invention〕

As mentioned above, according to the present invention, the amount of radioactive rare gas held in the activated carbon type rare gas holding up tower is uniform in each tower, and the amount of rare gas flowing out is the same regardless of which connecting pipe is assumed to be broken. amount. Therefore, the amount of radioactivity released in the event of an accident can be suppressed to a minimum.

[Brief explanation of drawings]

FIG. 1 is a schematic system diagram of a gaseous exhaust treatment device according to an embodiment of the present invention. 1... Piping, 2... Condenser air extractor,
3... Steam air extractor for start/stop, 4... Exhaust gas preheater, 5... Exhaust gas recombiner, 6... Exhaust gas condenser, 7... Exhaust gas precooler, 8... ... Exhaust gas dryer, 9... Prefilter, 10... Activated carbon rare gas hold up tower 1, 11... Activated carbon rare gas hold up tower 2, l2... Activated carbon rare gas hold up tower 3rd hold up column, 13... 4th activated carbon type rare gas hold up column, 14... Exhaust gas particle filter, 15... Exhaust gas vacuum pump, 16... Main exhaust stack.

Claims (1)

[Claims] In a gaseous waste treatment device in which gaseous waste extracted from a condenser is processed through rare gas holdup towers in which activated carbon is installed and connected in series, the length of each of the plurality of rare gas holdup towers is A gaseous waste treatment device characterized in that the gaseous waste treatment device is formed so that the downstream side is longer.