DECONTAMINATION AROUND CHERNOBYL

As a consequence of the Chernobyl accident, a lot of various contaminated materials were generated, mostly considered as radioactive waste. In order to deal with this problem a pool of 17 stationary and movable waste disposal plants were requested. Within the framework of this TACIS project, five plants were selected as top priority pilot projects.
In view of this situation, the feasibility study was initiated within the TACIS programme on the conception of these movable waste disposal plants.
Main objectives of the feasibility study were the decontamination of vehicles, the combustion of organic radioactive waste, compaction and cementation in containers suitable for intermediate or final storage and decontamination of soil. The basic designs, radioactive protection as much as cost estimation were described in the realization concept.
The project was contracted to the Kraftwerks und Anlagenbau AG (K.A.B AG).

The study had the primary objective of developing five plants that comprises:
Movable decontamination plant for utility vehicles
Movable combustion plant for organic radioactive waste
Movable cementation plant for radioactive waste
Unmanned soil treatment system
Small size machinery for removal of small contaminated upper soil layers
The support from K.A.B AG was given considering the design, licence planning, installation configuration and proposals for the implementation of the installations taking into account the movability and radiation protection aspects.

K.A.B AG developed a concept for each module of the movable plant complex. Technical solutions were proposed and cost assumptions provided. This project was to be involved in a larger project concerning the solving of Chernobyl problem by the "Vector" programme as described in 1991.
Movable decontamination plant
The concept included planning design, erection, commissioning and test of a movable decontamination plant for utility vehicles.. The plant may be installed in a 36 hours period and required up to 12 units container for transport. The size of the object to be treated according to the basic design should fit the following requirements (below 20 tons, shorter than 12 m, height smaller than 4 m and width smaller than 3 m).
The treatment of the object was mainly automatic and included the use of brush and high-pressure water jet. The wash solution resulting from the decontamination and removed waste solids were collected and transferred to the water conditioning facility. For economic reasons, water could be reused under the assumption that all substances (oil, solid substances, fat or undissolved oil) as much as radioactivity was decreased by two orders of magnitude.
Most of the components were enclosed in a single lightweight tent (30 x 15m with 7.4 m height) equipped with an exhaust air purification system. The interior of the tent was designed to operate with a small underpressure from 0.3 to 0.5 mbar. The decontamination area with the high pressure spray facility was separated from the whole room by an interior tent (20 x 6). Inside the main tent, a control room, fresh water storage tanks and an equipment container took place. The water conditioning facility and a power generator unit were located outside the main tent. Due to the heating up of decontamination solutions (up to 50 oC), the plant could operate below freezing point.
Movable Combustion plant for organic waste
The concept included planning, design, construction, commissioning and test of a movable combustion plant for organic radioactive waste.
The combustion took place at 900 C in a fluidized-bed furnace for 600 kg/h combustion capacity. The firing method guaranteed a complete and stable combustion even in case of widely varying material composition. Screw conveyors charged the combustion chamber and removed the bed-ashes.
The generated heat was used to cover auxiliary heat and served as power supply for the whole plant and possible adjacent plants.
The combustion gas was filtered through high efficiency submicron particulate air filters and then released through the stack. The ashes and filter elements were deposited in barrels and further treated as incombustible radioactive waste. For radioactivity monitoring and staff protection purposes, the plant modules were situated in a radiation protection controlled area. Continuous measuring and recording of the remaining activity ensured that all the actions are within the legal limits.
The plant has been designed as a movable system on the basis of container components with their measures and weight meeting the standard for rail, road and water transportation.
Movable cementation plant
The concept included planning, delivery, trial assembly and cold commissioning of a cementation plant.
The following raw waste could be treated in the plant:
Sludge coming from the decontamination mobile equipment
Decontamination drains coming from the decontamination mobile equipment
Resins and filtering material used for decontamination of water
Ashes coming from the combustion plant
Rumble issued from the contaminated buildings demolished
Sludge, waste water and resins were conveyed in 1 m3 container to the plant and were delivered in receiving containers used in the cementation process. Ashes were conveyed to the plant in 200 l drums.
Unmanned soil treatment system
The concept considered the use of an unmanned tractor equipped with tracked soil treatments devices (harrowing, ploughing, sowing, manuring devices). Gamma exposition dose rate due to the expected soil contamination was in the range 2 to 100 G/h.
To operate this tractor additional equipment as servo-motors, converters and radio communication devices were necessary. A remote control system allowed the operator to drive the tractor with the help of TV monitor displays.
Small-size machinery
The main objective of this machinery was to clear away and to remove the contaminated upper soil layer on small areas. This consisted mainly in light weight, convenient and manoeuvrable equipment (small tractors, self propelled vehicles and trailers)

Conclusions and recommendations

At the end of the project, a cost evaluation sheet has been provided dealing with the concept of a plant complex (i.e. decontamination plant, combustion plant, cementation plant). It became obvious at that point that some substantial funding was required considering that the proposed plant were only a small part of the Chernobyl problem according to the Vector programme.
The final report proposed to include a related project into the scope of TACIS programme concerning the complex of combustion/cementing, special treatment plants. The pilot plant could be manufactured by European manufacturers and subsequent series manufactured in Ukraine. Such an approach could be a reasonable continuation of ESU 0042 Project to be implemented in the framework of TACIS programme 1992/1993.