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/Recently the ICRP has issued a report where the problem ofdose evaluation from internally deposited radionuclides is discussed,to which the reader is referred for more detailed information [17].4. 1. 2. 2. 2. Organization of monitoring in practice. (1) Externalcontamination. As regards skin contamination, the work is relativelyeasy and the detectors already described can be used for evaluatingcontamination by both alpha and beta/gamma emitters. The fr e ­quency of this monitoring should be governed by the extent of thecontamination hazard. Wherever unsealed radioactive sources liableto produce an appreciable amount of surface contamination are handled,monitoring should be carried out daily or even twice daily, aftereach half-day's work. Workers should normally wash before beingmonitored in order to safeguard the monitoring instruments fromcontamination, and the measurement made is therefore of residualcontamination after washing. When normal washing procedures areineffective in removing the contamination, and decontamination undermedical supervision has been resorted to, the exposure readingsobtained must be entered in the records. Maximum perm issiblelevels have not been definitively established by the InternationalCommission on Radiological Protection; however, the tables appearingin Appendix II to the IAEA Manual [15] may be referred to as anindication.(2) Internal contamination. For internal contamination, monitoringshould be carried out periodically, the frequency again dependingon the extent of the hazard. Thus, for work with radionuclides usedas tracers, annual monitoring is sufficient, while for operationsinvolving substantial quantities of radioactivity twice-yearly, quarterlyor even more frequent surveys should be undertaken. As hasalready been seen, various direct or indirect methods may be used.Gamma spectrometry makes it possible to carry out periodic surveysfairly easily so as to evaluate the body burden of gamma-emittingnuclides. It should, however, be noted that this is a rather expensivemethod. Radiochemical analyses of the excreta, particularlythe urine, are therefore preferred.A knowledge of the radionuclides with which the given individualis working makes it possible to determine the kind of examinationrequired. However, these examinations need only be made at presentin respect of persons exposed to considerable internal contaminationhazards. In certain cases, as has been described above,96

This publication is no longer validPlease see http://www.ns-iaea.org/standards/it is possible to determine the quantities of radionuclides likely tohave been inhaled on the basis of the contamination of the atmosphereand the conditions of work. All these readings for internal contaminationof the worker should permit the calculation of total annualfigures, indicating the dose received by the organism as a wholeand by particular organs. Obviously this can be done only if thenumber of contaminating radionuclides and the contribution of eachto the dose is known.(3) Accidental exposure. Any incident or accident where appreciableradioactive contamination is suspected or has occurred must befollowed by monitoring. If gamma emitters are concerned, gammaspectrometryprovides an easy and quick means of evaluating thebody burden. If alpha or beta emitters are concerned, radiochemicalanalyses of blood and excreta (particularly urine) will make itpossible to estimate the body burden. This estimate can be madeon the basis of a study of the contamination of blood, urine and faecesas a function of time. In any case interpretation proves rather difficult,however, with regard to the mathematical models chosen forradionuclide elimination (usually an exponential function or lessoften a power function).4. 1. 3. Estimation of the absorbed dose4. 1. 3. 1. Summation of exposuresThe preceding paragraphs contain a description of methods ofevaluating irradiation, both from external radiation and radioactivecontamination. It is no easy matter to add together the dose valuesdue to the various types of irradiation, but an attempt to do so shouldbe made whenever practicable, though there is a great differencebetween the readings for external irradiation and those for radio -active contamination. It is relatively easy, with the help of continuouslyoperating dosim eters, to obtain approximate estimatesof the total exposure dose due to external radiation. Data on radioactivecontamination on the other hand, are highly unsatisfactoryand indicate only the body burden of radionuclides at a given moment.In theory, therefore, considerable interpretation work is neededin connection with internal irradiation, although in practice suchwork is undertaken only if the exposure exceeds about 1 0 % of theperm issible concentration. Be that as it may, the various expo­97

Safety_Series_013_1965 - gnssn - International Atomic Energy ...
Safety_Series_006_1961 - gnssn - International Atomic Energy ...
Radiation Protection Procedures - gnssn - International Atomic ...
Safety_Series_008_1962 - gnssn - International Atomic Energy ...
Safety_Series_041_1975 - gnssn - International Atomic Energy ...
Safe Handling of Radioisotopes - gnssn - International Atomic ...
No.6-Suppl 1988 - gnssn - International Atomic Energy Agency
Safety_Series_015_1965 - gnssn - International Atomic Energy ...
Safety_Series_016_1966 - gnssn - International Atomic Energy ...
Safety_Series_004_1961 - gnssn - International Atomic Energy ...
Safety_Series_024_1967 - gnssn - International Atomic Energy ...
Safety_Series_019_1966 - gnssn - International Atomic Energy ...
Safety_Series_005_1961 - gnssn - International Atomic Energy ...
safety series - gnssn - International Atomic Energy Agency
Safety_Series_035-S-1_1992 - gnssn - International Atomic Energy ...
SAFETY PR A CTICES - gnssn - International Atomic Energy Agency
SAFETY ST; NDARDS - gnssn - International Atomic Energy Agency
LEVEL 3 - gnssn - International Atomic Energy Agency
Level 2 - gnssn - International Atomic Energy Agency
1 - 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_050-SG-S2_1979 - gnssn - International Atomic ...
Safety_Series_010_1963 - gnssn - International Atomic Energy ...
Safety_Series_028_1968 - gnssn - International Atomic Energy ...
Research Reactor - gnssn - International Atomic Energy Agency
Notes on Certain Aspects of the Regulations - gnssn - International ...
Principles for Establishing Limits for the Release of ... - gnssn
INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA 1958 - gnssn
Borchardt - gnssn - International Atomic Energy Agency