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標題: 關(guān)于源比活度大小的問題 [打印本頁]
          

          
作者: tabu    時間: 2011-8-25 12:23
          
標題: 關(guān)于源比活度大小的問題
          按照教科書 強天鵬老師主編《射線檢測》第二版 第一章1.2.7中提到源比活度大小排列順序為：Se75(1.45×10000 Ci/g)>Tm170(
          
1000 Ci/g)>Ir192(350 Ci/g)>Co60(50 Ci/g)>Cs137(25Ci/g).而第二章2.2.1 射線源的特性參數(shù)表 提到Se75源的比活度為中。前后矛盾了 請問下強老師 到底那個對   了 而且10年的射線考試題上也考核。請回答 謝謝 強老師。[attach]302[/attach]
          
作者: 強天鵬    時間: 2011-9-2 22:35
          
 本帖最后由 強天鵬 于 2011-9-2 22:36 編輯 
          

          
您說得對，書上是錯了。
          
查了很多數(shù)據(jù)庫，沒有找到權(quán)威數(shù)據(jù)。
          
哈佛大學資料庫中關(guān)于Se75的詞條也沒有比活度數(shù)據(jù)。
          

          
現(xiàn)給出一組權(quán)威性待考證的比活度數(shù)據(jù)：
          
Co60實際比活度約為50Ci/g(1850X10Bq/g)
          
Ir192實際比活度約350Ci/g，(13000×109Bq/g)。
          
Se75比活度約為148Ci/g(5500×109Bq/g)，
          

          
又：以下資料可能有用，有興趣不妨看一看：
          
RADIONUCLIDE SAFETY DATA SHEET
          
NUCLIDE: Se-75 FORMS: ALL SOLUBLE
          
________________________________________________________________
          
PHYSICAL CHARACTERISTICS:
          
HALF-LIFE: 119.78 days TYPE DECAY: e- capture
          
no significant beta- ; gamma: 0.066 MeV (1.02 %)
          
0.097 MeV (3.41 %)
          
0.121 MeV (16.7 %)
          
0.136 MeV (59.2 %)
          
0.265 MeV (59.8 %)
          
0.401 MeV (11.4 %)
          
Hazard category: C- level (low hazard ) : .10 uCi to 1 mCi
          
B - level (Moderate hazard) : > 1 mCi to 100 mCi
          
A - level (High hazard) : > 100 mCi
          
EXTERNAL RADIATION HAZARDS AND SHIELDING:
          
The exposure rate at 1 cm from 1 mCi is 1985 mR/hr. (ignoring photons less than 11 KeV).
          
The exposure rate varies directly with activity and inversely as the square of the distance. The
          
mount of lead necessary to reduce the exposure rate by a factor of ten is 0.5 cm.
          
HAZARDS IF INTERNALLY DEPOSITED:
          
The annual limit on oral intake (ALI) of Se75 corresponding to a whole-body gamma
          
exposure rate of 500 mrem/year is 54 uCi.
          
DOSIMETRY AND BIOASSAY REQUIREMENTS:
          
Film badges and dosimeter rings are required if 5 millicuries are handled at any one time
          
or 1 millicurie levels are handled on a frequent (daily) basis.
          
Urine assays may be required after spills or contamination incidents.
          
SPECIAL PROBLEMS AND PRECAUTIONS:
          
1. When 1 millicurie is used, work behind lead shielding. Handle stock solution vials in
          
shields or use tongs or forceps.
          
2. Change gloves often and survey frequently. Smear surveys in uncontrolled areas
          
required.
          
3. Segregate wastes to those with half-lives greater than 90 days ( but not with H3 and/or
          
C14).
          
4. Dilute aqueous wastes may be disposed to the sewer system in amounts of up to 10 uCi
          
daily per lab.
          
6/90
          

          
作者: xcb526    時間: 2011-9-2 22:38
          

          
感謝強總！
          
作者: Nan168    時間: 2012-2-29 10:57
          
感謝強總。您這種實事求是的作風令人猶然起敬。
          
作者: 心心    時間: 2012-3-3 11:20
          
學習下，需要
          
作者: 浮屠灘主    時間: 2014-9-2 09:57
          
強老師，版主說的這個問題既然知道敘述矛盾，又沒有更改版本也沒有聲明，怎么三級考試還出這樣的試題啊




          

          

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