FR2546332A1 - METHOD OF DECONTAMINATING IRON MITRAIL AND / OR RADIOACTIVITY CONTAMINATED STEEL - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS A PROCESS FOR THE DECONTAMINATION OF IRON AND OR STEEL MITRAIL WHICH HAS BEEN CONTAMINATED BY RADIOACTIVITY, BY MELTING THE MITRAIL IN THE PRESENCE OF SCORING AGENTS OF THE FUSION BATH. IN ORDER TO FURTHER REDUCE THE RESIDUAL RADIOACTIVITY, IT IS OPERATED, IN ACCORDANCE WITH THE INVENTION, BY ADDING IN ADDITION INACTIVE ISOTOPES OF RADIOACTIVE ELEMENTS IN THE BATH AND BY SUBJECTING THEM ALSO TO THE MELTING PROCESS AS A FUNCTION OF THE SPECIFIC SOLUBILITY OF THE ELEMENTS, THE RADIOACTIVE ISOTOPES OF THE ELEMENTS ARE DISCHARGED FROM THE FUSION BATH AND TRANSFERED TO THE DAIRY WHICH IS SEPARATED FROM THE BATH. IN THIS MANNER AN IRON OR STEEL BATH WITH SUFFICIENT RESIDUAL RADIOACTIVITY IS OBTAINED FOR THE IRON OR STEEL TO BE REUSED.

Description

Method for decontaminating iron and / or steel scrap

contaminated by radioactivity.

  The present invention relates to a method for decontaminating iron and / or steel scrap which has been contaminated by

  radioactivity, by melting the grape

  the presence of scarification agents in the iron / steel melt. According to the article "Treatment of Metallic Wastes by Smelting" by JH Cavendish in IAEA SM 234/14, a method of decontaminating steel scrap, contaminated with fluorinated uranium compounds, neptunium, is already known. plutonium and tehnecium, by fusion after chemical purification

  Beforehand, a melting agent is added to the melt.

  the uranium, neptunium and plutonium are collected for the most part in the slag which is then removed by this process, the disposal of waste is simplified by the reduction of volume obtained in the form of non-reusable pieces of scrap.

  the reuse of the low-level radioactive material

  both in the melt. We have also already proposed a method for the decontamination of lead, according to Cerré P, Mestre E, Courtauld J; the

  decontamination of lead; "Scientific news bulletin

  69, pages 49 to 58 (1963) In a known manner, lead is used most of the time in the form of lead bricks to stop a rich radiation.

  in energy in laboratories and similar

  Because of the high material costs, we have already looked for

  in the past to reuse contaminated lead.

  When discharging fuel from stopped nuclear power plants, relatively strong components must be removed from the reactor core area, which require a thick protective shield for transport to final storage. In addition, large quantities of parts are required. contaminated steel must be evacuated

  proposed to smelt these contaminated steel parts and

  from them protective shields which can be used for the disposal of highly radioactive waste, see "Atomenergie / Kerntechnik", volume 41 (1982),

  pages 279 280 This is a way to reduce strong-

  the waste volume and, consequently, the discharge costs in the final storage place and this opens up a

  possibility of efficient use of waste.

  The present invention relates only to steel scrap that has been surface contaminated by radioactivity, as occurs for example in

  In this respect it should be noted that large

  Smooth faces can be quickly decontaminated while cavities, corner pieces, slots, tubing and closed tube ends require more work.

  superficial features a deep distribution of

  exponential thread, we can find a point from which the

  conventional decontamination costs are no longer in a relationship

  economically favorable port with an additional reduction

  radioactive radiation The steel scrap possesses

  then also residual radioactivity

  radioactive waste is defined according to the use of

  free limit (the limit value between a waste

  radioactive material and inactive waste) on the basis of the

  corresponding regulatory requirements.

  Residual radioactivity generally prevents the direct reuse of steel scrap

  grape can be treated as a lightly radioactive

  active in order to be transported to a final storage location or it must be decontaminated

  to be recycled properly.

  The object of the present invention is to create an improved process

  for melting decontamination of iron scrap

and / or steel.

  This problem is solved by the fact that additional inactive isotopes

  of radioactive elements in the bath of

  merge, are added and submitted to the merger process.

  The decontamination process according to the invention is based on the method, known and cited above, of melting steel

  contaminated iron and scarification of radioactive

  assets by which the surface of the steel or iron is contaminated

  In this known metallurgical smelting

  scarification occurs in most radioactive elements.

  the radioactive elements fall into intermetallic combinations which are lighter than the base material and which consequently

  the slag on the surface of the melt The slag contains

  radioactive elements can then be removed from the bath surface and converted into fats.

  radioactive waste storage In this process of decon-

  known contamination, there is, however, still a radio-

  residual activity that can be problematic

  for reuse of "decontaminated" steel scrap.

  The components of the slagging agents mentioned, such as those used, for example, in a blast furnace smelting process, are, for example, 40% SiO 2 O 1% SiO 2 40% Na 2 O 0.1% Al 203 5 13% KO 2% Mg O 2 13% Fe O 1% Mn O 10% in which case it is used for one ton of crude steel from 300 to

800 kg of slagging agents.

  With the means according to the invention, in particular the addition

  inactive isotopes, we obtain that, depending on the solubili-

  of the elements, the radioactive isotopes of the elements are discharged out of the melt and are collected in the slag. It is thus possible to obtain a significant reduction in the residual radioactivity of the

  so that we get a molten steel bath with a radio-

  activity-practically negligible.

  Since the amount of scrap contaminated by radio-

  activity and from nuclear facilities immobilized and repair is very large and requires significant costs because of the volume to be treated as radioactive waste to be removed little active, the process according to the invention represents an important progress because, thanks to decontamination of the melt produced in accordance with the invention, it is possible to obtain

  a significant reduction in the volume of radioactive waste to be

  The steel obtained from the melt can be recycled and reused. The radioactive slag is conditioned for the transport of waste and it requires a much smaller storage volume than the initial contaminated steel shot.

  By the process according to the invention, it is essential to

  components consisting of strontium, barium, cerium, europium and zirconium.

  cesium and antimony vaporize during the process.

  above fusion and are stopped by filtering fumes.

  According to other features of the invention: the inactive isotopes are introduced into the melt; inactive isotopes are added as minerals; inactive isotopes of strontium are added,

  barium, cerium, europium and zirconium.

  The separated slag which, as indicated above, contains the radioactive elements or the fission products is conditioned,

  as already stated, in the form of a product constituting

  radioactive waste to be evacuated and can be introduced into containers that can be made from

steel or decontaminated iron.

Claims (4)

claims   A method for the decontamination of iron scrap and / or steel which has been contaminated by radioactivity, by melting the scrap in the presence of scarification agents of the iron / steel melt, characterized in that adds a supplement of inactive isotopes of the radioactive elements found in the bath of   merger and subject them to the merger process.   Process according to Claim 1, characterized in that the inactive isotopes are added to the melt.   Process according to any one of claims 1 and 2,   characterized in that the inactive isotopes are added under the form of minerals.   Process according to one of Claims 1 to 3,   characterized by the addition of inactive isotopes of   consisting of strontium, barvum, cerium, auropium and zirconium.   Use of iron and / or decontaminated steel   according to the method according to one of claims 1 to 4   for the manufacture of containers for waste storage radioactive.