CS240907B1 - Device for removing radionuclide from waste gas - Google Patents

Abstract

A device for removing radionuclides from waste gas, which reduces the radionuclide content in the waste gas to a concentration permissible for release into the surrounding atmosphere. The device uses the principle of absorption, adsorption and filtration for gas purification. The entire purification device consists of several elements in the following arrangement: condenser (1), condenser sump (2), coarse fabric filter (3), adsorption column (4), pre-filter (5) and two highly efficient aerosol filters (6, 7). The device can reduce the radionuclide concentration in the gas by up to 6 orders of magnitude. This device is effective for removing radionuclides from gas in both aerosol and vapor form and can be used for purification of waste gas generated during solidification of high-level waste, or generated during incineration of radioactive waste. When using the waste gas purification device, only a small amount of liquid radioactive waste is generated.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for the capture of radionuclides from the off-gas generated by solidification of radioactive waste.

For the purification of waste gas resulting from the reprocessing of spent nuclear fuel or the solidification of highly active wastes and which contains radionuclides in the form of gases, vapors and aerosols ^, the principle of absorption, adsorption, filtration and mechanical separation on relevant technological equipment such as capacitors , adsorption columns, absorbers, scrubbers, cyclones, filters, etc. These devices are used to remove radionuclides from the gas in series, mostly in the following order: cyclone - condenser -> scrubber -> moisture separator - * adsorber -> aerosol filter. Various combinations of engagement of individual technological elements are reported by J * D.Christian and D.T.Pence in a review report PNL-2486 (1977) and the book Control of Semivolatile Radionuclides in Gaseous Effluents at Nuclear Pacilities, Tech. Rep. Ser., No. 220, IAEA, Vienna 1982. For example, a purification system of calcination gases at a chemical processing plant in Idaho, USA, which consisted of the following elements: cyclone—>

cooling tank — 5 »Venturi scrubber-5 ·· scrubber -> moisture separator—> preheater—> aerosol filter (TC" Thompson, GE Lohse, BRWheeler, Nucl.Technol. 16 (1972) 396) · The equipment used contains a high number of individual separators and are relatively complex.

In contrast, the gas-phase radionuclide removal apparatus of the present invention is simpler and at the same time achieves high radionuclide removal efficiency.

It utilizes the process of absorption, adsorption and filtration in the following arrangement of the individual cleaning elements.

240 907

- 2 coarse fabric filter - adsorption column -> pre-filter and two high-performance aerosol filters connected in series. Absorption takes place in condensate formed from water vapor. The higher effect of the invention is due to the fact that the device is simpler than the hitherto used and thus more economical, while the removal of radionuclides from the gas is high. Two-stage high-efficiency filtration ensures safe removal of alpha plutonium emitter. The higher armor efficiency according to the invention results from the following examples:

Example 1

Waste gas from a laboratory solidification containing Cs konT37 centration of 0.03 .mu.g / 1 labeled ^J 0s was led to room cleaning device consisting of a capacitor 1, condensate trap comprising a two-filter punched fabric filter (Pinet PES-4) adsorption column with glass sinter of 0.4 mm, 63 mm impregnated PegO ^ 4 »pre-filter with asbestos and glass fiber filter paper (AEROS-A), two high-performance filters with glass microfibre filter paper (RA-λ 61) . · diagram a in Fig. 1. gas throughput apparatus was 0.5 1 / b, gas temperature 20Í2 ^p C.Koncentrace cesium in the waste gas was reduced to the apparatus of tfřádů.

Example 2

Waste gas from laboratory solidification containing RuO2

6 with a concentration of 0.7 µg / l labeled Ru was fed to the laboratory purification apparatus described in Example 1 under the same experimental conditions as in Example 1. On said apparatus, the RuO 2 concentration in the waste gas was reduced by 6 orders.

Example 3

Waste gas from laboratory solidification containing Sr at a concentration of 0.15 ~ 4 ng / l labeled with ^ ° Sr was fed to the laboratory

3,240,907 the purification apparatus described in Example 1 under the same experimental conditions as Example 1. On said apparatus, the strontium concentration in the off-gas was reduced by 5 orders of magnitude.

When Sr is in the form of aerosol, Ru is in the form of vapors and aerosols, the apparatus of the present invention is therefore capable of removing both aerosols and radionuclide vapors from the off-gas. An advantage of the device according to the invention is also that in its use radioactive liquid waste is produced only to a small extent during condensation, as opposed to wet processes using scrubber scrubbers to capture radionuclides from the waste gas.

Claims (1)

Object of the invention 240 907 Device for removing radionuclides from waste gas, characterized in that it consists of a condenser (1), a condensate sump (2), a coarse filter (3), an adsorption column (4), a pre-filter (5) and two high-efficiency aerosol filters (6,7).