Safe Handling and Reduction of Low-Level Radioactive Waste from Radioisotope-Handling Facilities of Universities.

1996 Fiscal Year Final Research Report Summary

• Project/Area Number: 07308045
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 総合
• Research Field: 環境保全
• Research Institution: THE UNIVERSITY OF TOKYO
• Principal Investigator: MAKIDE Yoshihiro The University of Tokyo, Radioisotope Center, Professor, アイソトープ総合センター, 教授 (40011746)
• Co-Investigator(Kenkyū-buntansha): NOGAWA Norio The University of Tokyo, Radioisotope Center, Assistant, アイソトープ総合センター, 助手 (60208311) ; SAITO Tadashi Osaka University, Radioisotope Center, Assoc. Professor, ラジオアイソトープ総合センター, 助教授 (50153812) ; OHNISHI Toshiyuki Hokkaido University, Radioisotope Center, Professor, アイソトープ総合センター, 教授 (00000943) ; OSAKI Susumu Kyushu University, Radioisotope Center, Professor, アイソトープ総合センター, 教授 (90037276) ; NISHIZAWA Kunihide Nagoya University, Radioisotope Center, Professor, アイソトープ総合センター, 教授 (30022809)
• Project Period (FY): 1995 – 1996
• Keywords: Radioisotope, / Radioactive Waste, / Isotopes, / Liquid Scintillator, / Radioactive Liquid Waste, / Combustion, / Volume Reduction

Research Abstract

Radioisotopes are often used as inevitable tools in many advanced scientific researches at universities. Most of the isotope is recovered after the use and must be transferred to Japan Radioisotope Association for disposal with paying the high cost or must be stored in the waste disposal facilities in the universities by the Law Concerning Prevention from Radiation Hazards due to Radioisotopes, etc. even at very low level radioactivity. In this research, were studied the improvement of safe handling of such low level radioactive waste disposed at university facilities and the reduction of the waste volume by several methods following the Law by cooperation of the researchers belonging to the Radioisotope Centers of the National Universities.
Combustible waste such as paper, cloth and plastics with extremely low level activities were tested to reduce the volume by combustion, low temperature ashing, or dry distilllation, and the behaviors of radioisotopes during the treatment under vaiou s conditions were studied. The improvement of efficiency and the prevention of dispersion and the safe recovering of isotopes were preliminarily achieved.
Combustion of the liquid scintillator cocktail solution after the measurement of 5 kind betaray emitting nuclides (H-3, C-14, P-32, S-35, Ca-45) were investigated under the permission of Science and Technology Agency. The behaviors of these unclides during and after the combustion, their distribution and chemical forms in the exhausted gas and treated water, their remaining fraction in the furnace were investigated under the various combusting conditions. The obtained results gave the guideline for the safe combustion of higher concentration liquid scintillation cocktail.
Other possibilities of the reduction of the radioactivity in the waste solution or reduction of the volume were studied by the removal of radioisotopes from liquid organic and/or inorganic waste solutions by precipitation, absorption, ion-exchange, and distilllation, etc. and by the re-use of the radioisotope-used apparatus by several kind washing methods.