An experimental study on decontamination by surface conditions

Lee, Y H

Abstract

Surface decontamination is one of the very important problem to be completely solved in the isotope laboratorywhere there is always the possibility of radioactive contamination, i.e., on the floors, walls, working talbes andbenches etc., Isotope laboratories require surface covering of material which can be easily and effectivelydecontaminated. These experiment were done to find an effective decontamination procedure for kind of surfaceswhich usually are found in radioisotope laboratories and the best type of surface material, that is , one which iseasily decontaminated from the point of view of radiation health and safety. This study is presented to guideradioisotope laboratories in Korea which may need to renovate existing unsafe facilities. In some contaminatedfacilities entirely new installations may be required. Twelve types of surface materials are used for study inthis experiment. These include 10cm square of stainless steel, aluminum, ceramic and mosaic tiles, glass ,acrylic, formica board, asphalt tile and coated wood with 4 kinds of paints. Stepwise decontaminiation wasperformed with various decontamination procedures following a spill of I131 on the center of the surface materialbeing tested. Twelve different decontamination procedures were tested. These include wet wiping with water anddetergent, or dry wiping, or removing with gummed paper. Additional chemical proceures used 10% solution ofhydrochloric acid, or sulfuric acid, or ammonium citrate, or potassium iodide, or acetone or carbonetetrachloride. The final testing method was abrasion of the test surfaces. Brief analysis of experimental resultson the decontaminability on the tested surfaces showed; 1. Metallic surfaces such as stainless steel or aluminum,or glass, or a piece of ceramic tile ro acrylic are recommended as the surface materials for isotope laboratoriesbecause these are easily decontaminated by wet wiping only. 2. Formica board, asphalt tile and wood are not easilydecontamiated and only effective decontamination method is abrasion. However, decontamination procedures with thefollowing chemicals are more effective than wet wiping; use hydrochloric acid on the surface of asphalt tile andformica board; acetone on the surface of asphalt tile, varnished and lacquered wood. 3. Whenever a surface iscontaminated with liquid radioactive materials, day wiping is the first step to prevent spreading and flowing butis imcomplete. Dry wiping does wiping does not decontaminated the area to a permissible to safe level. The secondnecessary stip in decontamination is a thorough wet wiping. Thirdly the area must be checked for residualcontamination and chemical or physical decontamination used if still contaminated. 4. Laboratory floors and tablesmust present a smooth, continuous surface without scratches or cracks to prevent contamination which can not bedecontaminated. 5. A protective coating is recommended for porous covering surface such as wood, asphalt tile orformica board. These can not be easily decontaminated.