Safety_Series_025_1968 - gnssn - International Atomic Energy ...

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This publication is no longer validPlease see http://www.ns-iaea.org/standards/A dm inistrative cla ssifica tio n o f w ork ersF o r ad m in istra tive p u rp oses it is convenient to c o n s id e r twocon ditions under w hich w o rk e rs are exposed to radiation in thecou rse o f th eir w ork. T his distinction depends on the p ossib ility ofa certain level o f dose being exceed ed , rather than the actual le v e lobserved, and w ill have an influence on arrangem ents for health su rveillance and radiation protection as w ell as on the design and o p e ration of an installation.The two conditions are:(i) Conditions such that the resulting d oses might exceed threetenths of the annual maximum perm issible doses. This working con d ition sh all re q u ire that the w o rk e rs be su b ject to s p e c ia l healthsu pervision and person nel m onitoring. F o r these w ork ers the dosea sse ssm e n t w ill u su ally be a ch ieved by individual m on itorin g fo rexternal radiation o r internal contamination as appropriate, althoughthey may som etim es be made by indirect m ethods.(ii) Conditions such that the resulting d oses are m ost unlikelyto exceed three tenths o f the annual m axim um p e rm issib le d ose.W ork ers w orking under this condition would not requ ire individualm onitoring and special health supervision. F or these w orkers m onitorin g o f the w orking environm ent w ill u su ally be su fficien t, eventhough in som e ca ses individual m on itorin g m ay be d esira b le, e.g.to obtain statistical inform ation on the exp osu re.3.2.2. Standards applying to w orkers engaged in radiation w ork3. 2. 2. 1. E xposu re o f the whole body, gonads o r red bone m a rro wThe m axim um p e rm is s ib le d ose to the w hole body, gonads o rred bone m arrow of an individual shall be five rem s in any one year.A lso sin ce it is now estim ated that a w o rk e r should not r e c e iv e adose in e x ce ss o f 200 - 300 rem s fo r the whole span o f his w orkinglife , the follow in g form u la has been establish ed:D = 5(N- 18) remw here D is the d ose and N the w o r k e r 's age.6 8
This publication is no longer validPlease see http://www.ns-iaea.org/standards/E ighteen has been ch osen sin ce people do not n o rm a lly beginw orking b e fo re 18. T his form u la sets an upper lim it fo r the in d ivid u al's accum ulated d ose at a given age. The radiation protectionstan dards m ake use o f th is fo rm u la to p rovid e fle x ib ility to m eetsom e p ra ctica l situations (these ca s e s , how ever, are felt to be in frequ en t). In such c a s e s , the total accum ulated d ose to the w holebody, gonads o r red bone m arrow of an individual shall not exceedthe maximum p erm issib le doses derived from the form ula. In otherw ords, the dose can exceed , if the form ula allow s, the yea rly lim ito f fiv e r e m s . H ow ever, the form u la m ight lead to a b u ses. F o rin stan ce, a w ork er starting at the age o f 50 yea rs - o r , in extrem eca ses, 58 years - would reckon 40 years of working life without anyexposu re. Consequently, if he had started work at 18 years old, hecould be exposed to 40 X 5 = 200 rem s and thus, without contradictingthe form ula, he could be subjected to 200 rem s during the first year,even during the first w eek. A s such a state o f a ffairs cannot beallow ed, the ru le establish ed by m eans o f the above form u la issupplem ented by another sp ecify in g that exp osu re shall in no ca seexceed three rem s in any con secu tive 13 w eeks. T his is an im portant lim itation as it m eans fo r instance that exposu re sh all notexceed 12 rem s in any one y ea r, whatever the w ork er's age and thetim e when he was first engaged in radiation w ork.S evera l s p e cia l p ro b le m s m ay a r is e when an in d ivid u a l'sp reviou s exp osu re is not known. In such a ca se the individual isassum ed to have receiv ed the m axim um dose; thus a person havingbeen engaged in radiation work at the age o f 28 years but whosep reviou s exposu re h istory is not known, w ill be con sid ered to havere ce iv e d a total d ose o f 50 re m s.T hese standards have varied with tim e. T here are people whohave been m onitored and have received higher exposu res than thosenow p erm itted. In this ca se, as the w ork er has been exp osed in am anner con form ing to previou s recom m endation s, no breach of theregulations is regarded as having o c c u r r e d . When new regulationsare brought into fo r c e , it is th erefore supposed that people have a ccumulated the maxim um d ose.It should be noted, h ow ever, that in the ca se o f w om en o f r e productive capacity o r pregnant wom en sp ecia l p rov ision s are indicatedas w ill be m entioned la ter (see section 3. 2. 2. 8). A lso undersp e cia l conditions (see planned sp ecia l exp osu re, section 3. 2. 2. 3)an exp osu re o f up to 10 rem s fo r ca re fu lly scru tin ized individualsm ay be allow ed in one ex p osu re.6 9
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