Contamination, radioactive fixed

Non-Fixed Radioactive Contamination (Radioactive Material Only). Radioactive contamination that can be removed from a surface by wiping with a dry smear. lATA App. A... 

Since the disaster with the reactor at Chernobyl in May 1986, the contamination of drugs with radioactive substances has regularly been the subject of research reports. In the meantime, in the Huropean Community, the maximum value has been fixed at 600 Bq/kg, a figure which also guides the drug... 

The first term on the right-hand side of equation (2.14), termed the rate factor, represents the direct contamination of herbage by fallout during the growing season. The second term, lag rate factor, is the contribution from the previous year s fallout. This includes the contribution of uptake from the surface soil and matt and also the effects of carry-over of silage and other feeding stuffs from one year to the next. The third term, soil factor, represents the contribution of root uptake, allowing for radioactive decay and reduced availability as nuclides move down the soil profile and become fixed to clay minerals. 

Contamination in the laboratory must be avoided. This is controlled by smear tests i.e., a filter psqier is wiped over the surface and the paper is checked with a suitable instrument. In a so-called "clean area, the fixed contamination should not exceed 2 Bq for a, and 4 Bq for 8-7 on a surface of 100 cm. For an "active area" the rules are a maximum of 20 Bq for a per 100 cm, and 0.01 mGy h from j5-y at a distance of 2 cm from the surface. Radioactive aerosols ate monitored by air samplers in which a certain amount of air is drawn through a ftne filter paper after which the paper activity is measured. 

Contamination. The presence of a radioactive substance on a surface in quantities in excess of 0.4 Bq/cm (0.01 nCi/cm ) for beta and gamma emitters and low toxicity alpha emitters, or 0.04 Bq/cm (0.001 nCi/cm ) for all other alpha emitters. This is either Fixed contamination -contamination other than non-fixed contamination or Non-fixed contamination — contamination that can be removed from a surface during normal handling. ICAO 2-7.2, lATA App. A... 

Non-fixed radioactive contamination means radioactive contamination that can be readily removed from a surface by wiping with an absorbent material. Non-fixed (removable) radioactive contamination is not significant if it does not exceed the limits specified in Sec. 173.443. US 173.403... 

Contamination includes two types of radioactive material on surfaces or embedded in surfaces, namely fixed contamination and non-fixed contamination. There is no definitive distinction between fixed and non-fixed contamination, and various terms have been used to describe the distinction. For practical purposes a distinction is made between contamination which, during routine conditions of transport, remains in situ (i.e. fixed contamination) and, therefore, cannot give rise to hazards from ingestion, inhalation or spreading, and non-fixed contamination which may contribute to these hazards. The only hazard from fixed contamination is that due to external radiation exposure, whereas the hazards from non-fixed contamination include the potential for internal exposure from inhalation and ingestion as well as external exposure due to contamination of the skin should it be released from the surface. Under accident conditions, and under certain use conditions such as weathering, fixed contamination may, however, become non-fixed contamination. 

Conveyances may become contaminated during the carriage of radioactive material by the non-fixed contamination on the packages. If the conveyance has become contaminated above this level, it should be decontaminated to at least the appropriate limit. This provision does not apply to the internal surfaces of a conveyance provided that the conveyance remains dedicated to the transport of radioactive material or surface contaminated objects under exclusive use (see para. 514.1). 

Empty packagings which once contained radioactive material present little hazard provided that they are thoronghly cleaned to reduce the non-fixed contamination levels to the levels specified in para. 508 of the Regulations, have external surface radiation levels below 5 pSv/h (see para. 516) and are in good condition so that they may be securely resealed (see para. 520(a)) under these conditions the empty packaging may be transported as an excepted package. 

According to paras 241(a)(iii) and 523(c), SCO-1 is allowed to have non-fixed contamination on inaccessible surfaces in excess of the values specified in para. 241(a)(i). Items such as pipes deriving from the decommissioning of a facility should be prepared for unpackaged transport in a way to ensure that there is no release of radioactive material into the conveyance. This can be done, for example, by using end caps or plugs at both ends of the pipes (see also para. 241.7). 

Except as provided in para. 514, any conveyance, or equipment or part thereof which has become contaminated above the limits specified in para. 508 in the course of the transport of radioactive material, or which shows a radiation level in excess of 5 gSv/h at the surface, shall be decontaminated as soon as possible by a qualified person and shall not be re-used unless the non-flxed contamination does not exceed the limits specified in para. 508 and the radiation level resulting from the fixed contamination on surfaces after decontamination is less than 5 pSv/h at the surface. 

A. 1207. This section shall describe the radiation and contamination monitoring stations, including fixed hand and foot monitors, portal monitors (if used) and portable activity monitors located at these stations. The portable and laboratory equipment and instrumentation for performing radiation and contamination surveys, for contamination control between different access zones, for airborne radioactivity monitoring/sampling and for personnel monitoring shall also be described. 

Everyone who uses radioactive materials in research has a major responsibility to check for the presence of contamination in the work area after each experiment is completed. In addition, the entire laboratory must be surveyed at periodic intervals, the length of which is dictated by the isotopes used, the frequency of use, and their total activity. The purpose of the survey is to locate areas of radioactive contamination. Contamination can be either removable or fixed (nonremovable). Removable contamination is radioactivity that can be transferred from a surface to a smear test paper by rubbing with moderate pressure. Fixed contamination is radioactivity that remains... 

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