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Title: Treatment of Magnesium-Thorium Alloy Used in Military Defence Equipment by Separation of Thorium and/or Thermal Oxidation - 17009

Abstract

Magnesium-alloys doped with thorium (Th, 3% by weight and with a total activity content in the alloy of 120 Bq/g) to improve mechanical properties has been used in, among other applications, military equipment such as in the jet-engines in military aircraft. The material cannot, due to the presence of the radioactive Th, be handled as an ordinary scrap metal. It needs to be treated to render a more stable waste form prior to final disposal in which the amount of disposed metallic magnesium is limited due to the pyrophoric properties of such type of materials. By thermally treating the material it is possible to transform the alloy into oxide form (MgO and ThO{sub 2}) which is a much more stable form than metallic. This itself enables a form suitable for final disposal of the material. The oxidation step does however lead to an increase in volume and is therefore not an optimal treatment method. It is possible to treat the metal oxide powder in order to get a better volume reduction such as by super compaction but a better result can be obtained by separating the Th from the alloy, leaving a much smaller volume for final disposal. One waymore » of separating the Th from the metal is by dissolution of metallic material in acid followed by directed precipitation of Th as Th-oxalate. Several parameters such as the choice of acid, metal concentration in the acid solution, pH prior to precipitation and amount of added oxalic acid have been investigated. Another method to separate Th from Mg is to perform a selective dissolution of MgO from an MgO/ThO{sub 2} mixture with HNO{sub 3} leaving only ThO{sub 2} as a residue. These tests had to be preceded with an oxidation of the alloy. The tests show that it is possible to separate Th from the metal alloy by either dissolution followed by precipitation or selective dissolution of MgO from an MgO/ThO{sub 2} mixture. This leads to very effective volume reduction of the waste. For the direct dissolution and precipitation tests typically > 95% of the magnesium can be found in the acid solution while 99.5 % of the Th is found as a solid in the filters. For the oxide dissolution tests typically 98% of the Th can be separated from the bulk material, leaving the acid solution possible to free release and dispose of in the same way as for the previous method. (authors)« less

Authors:
 [1]
  1. Studsvik Consulting AB, SE-611 82 Nykoeping (Sweden)
Publication Date:
Research Org.:
WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
OSTI Identifier:
22794445
Report Number(s):
INIS-US-19-WM-17009
TRN: US19V0118038664
Resource Type:
Conference
Resource Relation:
Conference: WM2017 Conference: 43. Annual Waste Management Symposium, Phoenix, AZ (United States), 5-9 Mar 2017; Other Information: Country of input: France; refs.; available online at: http://archive.wmsym.org/2017/index.html; This record replaces 50038664
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DISSOLUTION; DOPED MATERIALS; MAGNESIUM ALLOYS; MAGNESIUM OXIDES; MECHANICAL PROPERTIES; MILITARY EQUIPMENT; OXALIC ACID; THORIUM ALLOYS; THORIUM OXIDES

Citation Formats

Oesterberg, Carl. Treatment of Magnesium-Thorium Alloy Used in Military Defence Equipment by Separation of Thorium and/or Thermal Oxidation - 17009. United States: N. p., 2017. Web.
Oesterberg, Carl. Treatment of Magnesium-Thorium Alloy Used in Military Defence Equipment by Separation of Thorium and/or Thermal Oxidation - 17009. United States.
Oesterberg, Carl. Sat . "Treatment of Magnesium-Thorium Alloy Used in Military Defence Equipment by Separation of Thorium and/or Thermal Oxidation - 17009". United States.
@article{osti_22794445,
title = {Treatment of Magnesium-Thorium Alloy Used in Military Defence Equipment by Separation of Thorium and/or Thermal Oxidation - 17009},
author = {Oesterberg, Carl},
abstractNote = {Magnesium-alloys doped with thorium (Th, 3% by weight and with a total activity content in the alloy of 120 Bq/g) to improve mechanical properties has been used in, among other applications, military equipment such as in the jet-engines in military aircraft. The material cannot, due to the presence of the radioactive Th, be handled as an ordinary scrap metal. It needs to be treated to render a more stable waste form prior to final disposal in which the amount of disposed metallic magnesium is limited due to the pyrophoric properties of such type of materials. By thermally treating the material it is possible to transform the alloy into oxide form (MgO and ThO{sub 2}) which is a much more stable form than metallic. This itself enables a form suitable for final disposal of the material. The oxidation step does however lead to an increase in volume and is therefore not an optimal treatment method. It is possible to treat the metal oxide powder in order to get a better volume reduction such as by super compaction but a better result can be obtained by separating the Th from the alloy, leaving a much smaller volume for final disposal. One way of separating the Th from the metal is by dissolution of metallic material in acid followed by directed precipitation of Th as Th-oxalate. Several parameters such as the choice of acid, metal concentration in the acid solution, pH prior to precipitation and amount of added oxalic acid have been investigated. Another method to separate Th from Mg is to perform a selective dissolution of MgO from an MgO/ThO{sub 2} mixture with HNO{sub 3} leaving only ThO{sub 2} as a residue. These tests had to be preceded with an oxidation of the alloy. The tests show that it is possible to separate Th from the metal alloy by either dissolution followed by precipitation or selective dissolution of MgO from an MgO/ThO{sub 2} mixture. This leads to very effective volume reduction of the waste. For the direct dissolution and precipitation tests typically > 95% of the magnesium can be found in the acid solution while 99.5 % of the Th is found as a solid in the filters. For the oxide dissolution tests typically 98% of the Th can be separated from the bulk material, leaving the acid solution possible to free release and dispose of in the same way as for the previous method. (authors)},
doi = {},
url = {https://www.osti.gov/biblio/22794445}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2017},
month = {7}
}

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