JPH0527089A - Emergency gas processing device for atomic reactor building - Google Patents

Abstract

PURPOSE:To improve the faculty of an activated carbon filter by adjusting the humidity of the exhaust gas passing through the activated carbon filter, in an emergency gas processing device which poocesses the exhaust gas supplied from a nuclear reactor building. CONSTITUTION:The exhaust gas supplied from a nuclear reactor building 1 is allowed to pass through a filter train 5 including an activated carbon filter 5e. An outside air take-in flow passage 7 which takes in the outside air into the filter train 5 on the upstream side of the activated carbon filter 5e during the above described passing and mixes the outside air with the exhaust gas is installed. Accordingly, the faculty of the activated carbon filter 5e can be improved by reducing the humidity of the exhaust gas passing through the activated carbon filter 5e.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emergency gas treatment device provided in an engineering safety facility of a nuclear reactor, and more particularly to an improvement for enabling its operation under optimum ventilation conditions.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional emergency gas treatment system (SGTS) for a nuclear reactor plant filters pollutant gas, that is, exhaust gas (hereinafter, also referred to as exhaust gas) introduced from a reactor building 1. It is designed to be discharged from the exhaust stack to the outside through the train 5 and the exhaust fan 6. The filter train 5 includes a moisture removing device 5a and a heating coil 5 from the upstream side.
b, pre-filter 5c, high-performance particle filter 5d, activated carbon filter 5e, and high-performance filter 5d.

The moisture removing device 5a and the heating coil 5b are provided for humidity adjustment and temperature adjustment. Further, the prefilter 5c and the high performance particle filter 5d are provided for removing particulate radioactive substances. The activated carbon filter 5e is mainly activated carbon impregnated with iodine,
It is provided to remove radioactive iodine. A device related to this type is disclosed in, for example, Japanese Patent Laid-Open No.
No. 48598 and the like can be mentioned.

The iodine-impregnated activated carbon used in the activated carbon filter 5e is used to adsorb radioactive iodine contained in the exhaust gas. However, iodine is a radioactive iodine in the exhaust gas, but contains an iodine compound and an organic material form an iodine compound such as various iodine compounds of the inorganic form, the iodine compound to reach the activated carbon filter, and an inorganic iodine (I ₂₎ It is known that methyl chloride (CH ₃ I) is the main component. It is known that inorganic iodine is directly adsorbed and removed on activated carbon, but methyl iodide has a small adsorption ability on activated carbon. Therefore, as shown in formula (1), the attached non-radioactive iodine Radioactive iodine is adsorbed on the activated carbon by performing an isotope exchange reaction with.

CH ₃ I ^* + C−I → CH ₃ I + C−I ^* (1) Here, CH ₃ I ^* represents radioactive methyl iodide, and C−I
Represents non-radioactive iodine impregnated with activated carbon, and CH ₃ I
Indicates non-radioactive methyl iodide, and C-I ^* indicates activated carbon and radioactive iodine adsorbed.

In this reaction, when the temperature rises, the reaction proceeds,
As the humidity increases, the reaction slows down. In addition, the higher the flow rate, the lower the adsorption performance of activated carbon. Therefore, in order to bring the performance of the activated carbon filter to an appropriate capacity, equipment such as a moisture separator, a heating coil, a dehumidifier, etc. are provided in order to adjust the temperature, humidity, and flow velocity of exhaust gas to appropriate values. A device related to this type is disclosed in, for example, JP-A-60-19.
8496 and JP-A-61-71399.

On the other hand, an apparatus provided with means for taking in outside air in the middle of the flow of the apparatus to cool the activated carbon when the apparatus stops due to a failure or the like is disclosed in, for example, Japanese Patent Laid-Open No. 186098/1983.

[0008]

SUMMARY OF THE INVENTION In the above-mentioned prior art emergency gas treatment apparatus, the ventilation conditions such as the temperature, humidity and flow velocity of the exhaust gas passed through the activated carbon filter do not necessarily exhibit the performance of the activated carbon filter. There was a problem that the thickness of the activated carbon filter became thicker because it was not operated as described above.

On the other hand, the apparatus shown in the above-mentioned Japanese Patent Laid-Open No. 58-186098, which has means for taking in outside air in the middle of the flow of the apparatus, takes in outside air when the apparatus is stopped and is used for cooling activated carbon. However, since the outside air is not taken in and mixed with the exhaust gas during the normal operation of the device, it does not act to reduce the humidity of the exhaust gas during the normal operation of the device.

An object of the present invention is to make it possible to appropriately lower the humidity of the exhaust gas that is ventilated in order to improve the performance of the activated carbon filter in the emergency gas treatment device that treats the exhaust gas introduced from the reactor building. To do.

[0011]

In order to achieve the above object, the present invention relates to an emergency gas treatment apparatus for a reactor building, wherein activated carbon is activated during exhaust gas ventilation from the reactor building to a filter train including an activated carbon filter. An outside air intake channel for mixing outside air with the exhaust gas is provided on the upstream side of the filter,
As a result, the humidity of the exhaust gas introduced to the activated carbon filter is reduced,
It is designed so that it can be operated under the ventilation conditions that give the best performance of the activated carbon filter.

[0012]

In the past, the performance of the impregnated activated carbon with respect to changes in exhaust gas temperature, humidity, and flow velocity was known only qualitatively. Therefore, the inventors of the present invention conducted detailed experiments on this, and the following properties were obtained. I found out.

(1) The adsorption coefficient increases as the temperature rises (FIG. 3).

(2) The adsorption coefficient increases as the humidity decreases (FIG. 4).

(3) The adsorption coefficient increases as the flow velocity decreases (FIG. 5).

In particular, since the property of (2) is remarkable, it has been found that reducing the humidity of exhaust gas is effective for improving the performance.

The following method can be considered as a method of dehumidifying exhaust gas.

(1) Raise the exhaust gas temperature by using a heater or the like.

(2) Removing moisture in exhaust gas with a dehumidifier or the like.

(3) Mixing dry air with exhaust air.

The method (1) is effective as a dehumidifying method and is also suitable as a method of bringing about an effect of improving the performance by raising the temperature. However, since the activated carbon used is iodine impregnated activated carbon, There is a problem that it cannot be used for a long time because of volatilization, and the temperature cannot be raised unnecessarily. The method (2) has a problem in that the apparatus becomes large in size for effective dehumidification with respect to a large exhaust flow rate.

On the other hand, in the method (3), since the absolute humidity of the outside air is low, it is possible to easily lower the humidity of the exhaust gas by mixing it with the exhaust gas, and the optimum temperature can be obtained. It is possible to treat at temperature. Therefore, this method is used in the present invention.

FIG. 6 shows the relationship between the mixture ratio of the exhaust gas and the outside air and the humidity of the exhaust gas after mixing. FIG. 6 shows a case where exhaust gas having a temperature of 66 ° C. and a relative humidity of 70% is mixed with outside air having a temperature of 20 ° C. and a relative humidity of 50% and treated at a temperature of 66 ° C.
As shown in FIG. 6, it can be seen that the relative humidity decreases as the mixing ratio increases. The adsorption coefficient showing the performance of activated carbon under this condition is 2.0 under the conventional treatment conditions, whereas it is 2.27 when the exhaust gas and the outside air are mixed at a mixing ratio of 0.35, which is the highest. Become. The reason why the adsorption coefficient decreases at a mixing ratio higher than this is because the flow velocity increases.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. Exhaust gas taken in from the reactor building 1 and the reactor containment vessel 2 has been conventionally sent directly to the filter train 5 of the emergency gas treatment device (see FIG. 2).
An outside air intake port 7 is provided at the inlet nozzle of the filter train 5 of the emergency gas treatment device, and the exhaust gas and the outside air are supplied at 0.2 to
It was made possible to mix at a mixing ratio of 0.5 (outside air / exhaust air).
The structure of the filter train 5 is the same as that described with reference to FIG.

According to this embodiment, the relative humidity of the exhaust gas aerated in the filter train 5 is lowered by mixing the outside air, so that the filter train 5 of the emergency gas treatment system is reduced.
The performance of the activated carbon filter 5e can be improved. Since only the outside air intake port 7 is provided, the structure is simple and the safety is high. Moreover, the valve of the outside air inlet 7 can be installed outside the building so that a person can easily approach it and operate the valve, and even if there is no power supply, it can be operated manually and is safe. is there.

For transient changes in exhaust conditions (changes in humidity, temperature, etc.) immediately after the reactor accident and changes in weather conditions of the outside air, a more precise mixing ratio of the exhaust gas entering the filter train 5 and the outside air Control is required. For this reason, an embodiment provided with a control device is shown in FIG. The data measured by the exhaust gas temperature / humidity detector 9 and the outside air temperature / humidity detector 10 are sent to the control device 8, and the exhaust flow rate adjusting valve 11 and the outside air flow rate adjusting valve 12 are controlled, whereby the filter train 5 The mixing ratio between the exhaust gas entering and the outside air is set to an appropriate value. According to the present embodiment, highly safe processing can be performed without being affected by a transitional change in exhaust gas state and weather conditions.

Depending on changes in weather conditions, the temperature of outside air may be low or the humidity may be high. Therefore, in still another embodiment shown in FIG. 8, the outside air intake port 7 is provided with the outside air preheater 13 so that it can be operated under optimum temperature conditions. The outside air preheater 1 based on the measurement data of the exhaust temperature / humidity detector 9 and the outside air temperature / humidity detector 10.
The heating at 3 is controlled by the controller 8.

As a result, the activated carbon filter 5e can be operated under more optimal conditions. Also, the heating coil 5
Backup in case of failure of b is also possible, and the device has higher safety.

[0029]

According to the present invention, since the exhaust gas relative humidity can be reduced by mixing the outside air with the exhaust gas entering the filter train, there is an effect that the performance of the activated carbon can be improved.

[Brief description of drawings]

FIG. 1 is a flow sheet of an embodiment of the present invention.

FIG. 2 is a flow sheet of a conventional device.

FIG. 3 is a diagram showing a relationship between an aeration temperature of activated carbon and an adsorption coefficient of radioactive iodine.

FIG. 4 is a diagram showing the relationship between the ventilation humidity of activated carbon and the adsorption coefficient of radioactive iodine.

FIG. 5 is a diagram showing a relationship between an aeration rate of activated carbon and an adsorption coefficient of radioactive iodine.

FIG. 6 is a diagram showing a relationship between a mixing ratio of outside air and exhaust gas and an adsorption coefficient of radioactive iodine.

FIG. 7 is a flow sheet of another embodiment of the present invention.

FIG. 8 is a flow sheet of still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor building 2 ... Reactor containment vessel 3 ... Reactor pressure vessel 4 ... Suppression chamber 5 ... Emergency gas treatment device filter train 5a ... Dehumidifier 5b ... Heating coil 5c ... Prefilter 5d ... High performance particle filter 5e ... Activated carbon filter 6 ... Exhaust blower 7 ... Outside air intake 8 ... Control device 9 ... Exhaust air temperature / humidity detector 10 ... Outside air temperature / humidity detector 11 ... Exhaust air flow rate adjusting valve 12 ... Outside air flow rate adjusting valve 13 ... Outside air preheater

Continued front page    (72) Inventor Yasuo Kidoguchi             3-1-1 Sachimachi Hitachi City, Ibaraki Prefecture Stock Association             Hitachi, Ltd.Hitachi factory (72) Inventor Fumio Nakashita             3-2 Sachicho, Hitachi City, Ibaraki Prefecture Stock Association             Inside Hitachi Engineering Service (72) Inventor Kiiko Nagayama             Hitachi, 3-10-3 Bentencho, Hitachi City, Ibaraki Prefecture             Kyowa Industry Co., Ltd.

Claims (4)

[Claims] 1. A reactor building emergency gas treatment device comprising a filter train including an activated carbon filter through which exhaust gas from the reactor building is ventilated, an exhaust fan, and an exhaust flow path connected to a downstream side of the filter train. An emergency gas treatment device for a nuclear reactor building, wherein an outside air intake passage for mixing outside air with the exhaust gas is provided upstream of the activated carbon filter during aeration of the exhaust gas into a filter train. 2. The emergency gas treatment for the reactor building according to claim 1, wherein the mixing ratio of the outside air and the exhaust gas from the reactor building is 0.2 to 0.5 (outside air / exhaust gas). apparatus. 3. A means for detecting the temperature, humidity or flow rate of the outside air and the exhaust gas from the reactor building, and a control means for controlling the exhaust gas and the outside air to an optimum mixing ratio in accordance with changes in the detected amounts. 2. The method according to claim 1, further comprising:
Alternatively, the emergency gas treatment device for the reactor building according to 2. 4. The emergency gas treatment device for a reactor building according to claim 1, wherein an outside air preheating device is provided in the outside air intake passage.