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DOSES DUE TO THE REUSE OF VERY SLIGHTLY RADIOACTIVE STEEL

Objective

The scope of the study is the determination of doses due to the reuse or recycling of very slightly contaminated radioactive steel in case of mechanical and thermo-mechanical treatments applied to scrap when exempted from regulations.

The study will mainly be based on already available data both in the nuclear field and in the conventional scrap industry. Experimental investigations will be performed, as far as possible, on radioactive samples coming from nuclear installations being dismantled. The various treatments applied to scrap before its melting have not yet been studied and are of great interest. In particular, techniques used in scrapyards should be studied in the view of inhalation and external exposure injuries.

This study applies to a large quantity of steel arising from dismantling of nuclear installations (EUR 10052).

Benefits are expected as regards management and cost of radioactive waste arisings, protection still being secured. The results concerning contamination dispersion during cutting of scrap will be useful for the evaluation of future large-scale decommissioning operations.
The metal scrap from a nuclear installation is released to a scrapyard where it is sorted and cut to adequate size before melting. A number of methods are used to reduce the scrap size including shredding, shearing, power saw, grinding and torch cutting. During these processes the workers can be submitted to metal dust emission. It is the goal of this project to study the different steps of scrap conditioning, evaluate the associated nuisances due to dust emission from a potential residual surface activity on the scrap and quantify the potential radiation dose for a person handling the scrap. An economical and technical overview of the scrap market was done, a scrapyard was visited and the most used cutting means were compared: shearing, the most commonly used, and grinding which is going to get a large importance because steriles are separated from scrap by this means.

Taking into consideration the results of bibliographic studies, realization of representative experiments of scrapyard working conditions seemed to be necessary. The different methods used for cutting metals in industry can be divided into 2 basic categories: mechanical means and thermal means. In this contract, a mechanical system, a shear and a thermal system, a cutting torch are considered. These 2 cutting means were tested in a first experiment in inactive conditions.

Caesium chloride was deposited on stainless steel, on carbon steel and on oxidized carbon steel.
The cutting experiments began with a 20 tonnes shear. Preliminary tests showed that the shear did not produce enough dust to work in a large cell; the experiments will be continued in a glove box. Another work performed was to establish and evaluate a first set of experiments for orientation purposes with respect to experimental conditions and the test equipment chosen for cutting with an acetylene torch.

A rough estimation of inhalation risk for torch cutting was calculated based on preliminary data which gives an idea of the expected range in which the doses fall.

The preliminary data was used in a stochastic model to estimate the doses and the number of individuals exposed due to the processing of alpha contaminated scrap.
WORK PROGRAMME

1. Discussion and documentation of the present regulatory situation. (BS-CEA)

2. Performance of steel cutting and aerosol sampling experiments observing industrial conditions. (CEA-Siemens)

3. Evaluation of inhalation risk in realistic situations.(all)

4. Determination of the radiological impact based either on bibliographic data or on experimental results. (BS-CEA)

5. Development of a stochastic programme to obtain the individual dose distribution. (BS)

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Commissariat à l'Energie Atomique (CEA)
Address
Centre D'études De Fontenay-aux-roses 60-68 Avenue Du Général Leclerc
92265 Fontenay-aux-roses
France

Participants (2)

Brenk Systemplanung
Germany
Address
Heinrichsallee 38
52062 Aachen
Siemens AG
Germany
Address
Rodenbacher Chaussee 6
63457 Hanau