Views
3 years ago

Safety_Series_025_1968 - gnssn - International Atomic Energy ...

Safety_Series_025_1968 - gnssn - International Atomic Energy ...

This publication is no

This publication is no longer validPlease see http://www.ns-iaea.org/standards/As a matter of fact, detectors used under normal conditionsare usually saturated by such high doses. Therefore, detectors forelectromagnetic, electron and neutron radiation must be used, witha range of sensitivity corresponding to these potential high exposures.4. 1. 2. 2. Monitoring of radioactive contamination4. 1. 2. 2. 1. Factors governing the organization of monitoring. Themeasurement of the radioactive contamination of an individual stillremains one of the most difficult problems in the field of radiologicalprotection. While it is relatively easy to evaluate skin contamination,it is a very tricky matter to estimate internal contaminationby either direct or indirect methods. In addition, the methods usedcall for highly specialized equipment and personnel. Therefore onlyoccasional individual monitoring for radioactive contamination canbe regarded as a practical possibility. It should be twofold innature:on the one hand, any normal work with unsealed radioactive sourcesshould be accompanied by periodical measurements of external orinternal contamination, the results of which should be compared withthose obtained from area monitoring at the work place; on the otherhand, individual monitoring should be carried out whenever an incidentor an accident involving the risk'of radioactive contaminationhas occurred. The results then provide a final answer to the questionto what extent, if any, contamination has affected the workerspresent.(1) Spatial distribution. As with external irradiation, it is importantin any case of radioactive contamination to know the spatial distributionof the dose. This can be determined very easily for skin contamination,but the spatial distribution of internal contamination isgoverned by the physico-chem ical properties and the metabolismof the radionuclide. Acquaintance with the nature of the contaminatingnuclide is therefore a prerequisite for determining the degreeof irradiation of the different organs of the body.(2) Time distribution. Various factors affect the time distributionof the dose. These include the physico-chemical form in which thecontaminating substance occurs and the radioactive properties, particularlythe half-life, of the radionuclides. Thus, in the case ofskin contamination, a distinction must be made between the initial94

This publication is no longer validPlease see http://www.ns-iaea.org/standards/contamination and the residual contamination after treatment. Inthat of internal contamination, the radioactive substances move inthe organism in accordance with their metabolism. The biologicalhalf-life may be defined as the time necessary for half the radionuclideto be eliminated from a given organ or from the wholeorganism. The contaminating nuclides have also a radioactive halflifewhich is the time necessary for half their atoms to decay. Itis the combination of these two half-lives which represents the timenecessary for the radioactivity in the organ or organism concernedto fall to half its original amount; this is termed the effective halflife.It is therefore logical that particular attention should be devotedto evaluating contamination by radioactive substances whichbecome fixed in the organism for a considerable length of time andhave a long radioactive half-life. Irradiation extending over severalyears or even over the life-time of the individual may indeed occur,as is the case with the most toxic radionuclides, such as strontium,plutonium, radium, etc.(3) Nature of radionuclide. Sometimes the contamination is dueto one radionuclide only, but it is very often multiple. A correctappraisal of the degree of irradiation of the organism and an accuratededuction of the probable consequences are possible only if the natureof the contaminating radionuclides is known. In dealing with skincontamination this is less important and it is often thought sufficientto estimate the contamination in term s of alpha and beta/gammaemitting substances. This simplified procedure can also be adoptedwith internal contamination, but here there is every advantage tobe gained from determining the respective contribution of each ofthe contaminating nuclides.(4) Extent of contamination. From the foregoing remarks it willbe apparent that the measurement of radioactive contamination re ­mains an extremely intractable problem. The interpretation ofreadings depends on a number of arbitrary hypotheses regardingthe geometrical conditions, in the case of direct measurement ofinternal contamination, and regarding the basic laws of metabolism,in the case of indirect measurement from the excreta. Moreover,the radioactivity levels to be detected under normal working conditionsare extremely low; while it is relatively easy to detect accidentalcontamination, it is very difficult to evaluate correctly regularcontamination lower than the maximum permissible body burdensin the organism.95

Safety_Series_013_1965 - gnssn - International Atomic Energy ...
Safety_Series_006_1961 - gnssn - International Atomic Energy ...
Radiation Protection Procedures - gnssn - International Atomic ...
Safety_Series_041_1975 - gnssn - International Atomic Energy ...
Safe Handling of Radioisotopes - gnssn - International Atomic ...
Safety_Series_008_1962 - gnssn - International Atomic Energy ...
Safety_Series_016_1966 - gnssn - International Atomic Energy ...
Safety_Series_024_1967 - gnssn - International Atomic Energy ...
Safety_Series_015_1965 - gnssn - International Atomic Energy ...
Safety_Series_019_1966 - gnssn - International Atomic Energy ...
Safety_Series_004_1961 - gnssn - International Atomic Energy ...
Safety_Series_005_1961 - gnssn - International Atomic Energy ...
safety series - gnssn - International Atomic Energy Agency
SAFETY ST; NDARDS - gnssn - International Atomic Energy Agency
No.6-Suppl 1988 - gnssn - International Atomic Energy Agency
Safety_Series_035-S-1_1992 - gnssn - International Atomic Energy ...
LEVEL 3 - gnssn - International Atomic Energy Agency
SAFETY PR A CTICES - gnssn - International Atomic Energy Agency
1 - gnssn - International Atomic Energy Agency
Level 2 - gnssn - International Atomic Energy Agency
SAFETY P R A C TIC E S - gnssn - International Atomic Energy Agency
SAFETY P R A C TIC ES - gnssn - International Atomic Energy Agency
Safety_Series_028_1968 - gnssn - International Atomic Energy ...
Safety_Series_050-SG-S2_1979 - gnssn - International Atomic ...
Safety_Series_010_1963 - gnssn - International Atomic Energy ...
Notes on Certain Aspects of the Regulations - gnssn - International ...
Research Reactor - gnssn - International Atomic Energy Agency
Borchardt - gnssn - International Atomic Energy Agency
Principles for Establishing Limits for the Release of ... - gnssn
INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA 1958 - gnssn