Page 535 - Instrumentation Reference Book 3E

518 Nuclear ~nstrumentation technology

Table 22.1 Radiation sources in general use
__
Emissions
(urzd energies- hk V)
Bern Gnnzrna .4@h
E,,
c______- __I_LI__
12.16yr 0.018 0.006 Nil Nil
5730yr 0.15 0.049 Nil Nil
2.6 yr 0.55 0.21 1.28 Nil Also 0.41 I MeV amiihilation
i5h 1.39 1.37 2.15
14.3 d 1.71 0.69 Nil Nil Pure beta emitter
3x10'yr 0.71 0.32 Nil Nil Betas emitted simulate fission products
5.3yr 0.31 0.095 1.17 (100) Nil Used in radiography. etc.
1.33 (100) Nil
qosr 28 S;r 0.54 0.196 Nil Nit Pure beta emitter
9017 64.2 h 2.25 0.93 Nil Nil
1311 8.O?d 0.6t-l- 0.181- 0.36 (79)+ Nil Used in medical app~~~a~i~ns
137fS 30 yr os+ 0.191- 0 66 (86) Nil Used as standard gamma
calibration source
"'Au 2.7d 0.991- 0.3$ 0.41 (96) Nil Gammas adopted recently as universal
standard
2XRa 1600 yr - .. 0.61 (22) Earliest radioactive source isolated
by Mme Curie-still used in medical
1.13 (13) applications
1.77 (25)
+ others
241 Am 4STyrr - 0 059 (35) 5 42 (12)
source
___ ~--- others 5.48 (85) Alpha X-ray ca~ibra~ion
_-___I.-_ I___-
Note: Figures in pwentlieses show the percentage of priinary disirltegration that goes into that particular emission (is.: the abundance).
-t iiidicates other radiation of lower abundance.
Table 22.2 Neurron sources
Source and type Neuetltron wnissioir Hdfilfe energles of mufrons
nls per wzit emitted
activity oi" ??iass
'"SLBG (*j, PZ) 5 X 10-5mq 60 dyas Low: 30keV For field assay of be~yllinm ores
"6Ra-Be (ct,~) 3 x IO-'/Bq lh32 yr Max 13MeV Eafly n source, now replaced by AdBe
Av: 3 MeV
21@Po--Be (a. n) 7 x 10-5/Bq 138 days Max. 10.8 MeV Short life is disadvantage
Av: 42MeV
24'Am-Be (a,n) 6 x I0 5/Bq 433 yr Max: 11 MeV Most popular iieturon source
AX 3-5 MeV
"'Cf fission 2.3 x f06ifig 2.65 yr Simulates reactor Short We and high cost
iieutron spectrum

By propagation-o~-e~or methods, the siandard devices as ~ti-co~cidc~~ce counters, and as large
deviation of R can be calculated as follows: a sample as possible.
The optimum division of a given time period
for counting source and background is given by
(22.5)
(22.4)
where tl and f2 are the times over which source-
plus-background and background counting rates
were measured, respectively. Practical counting
times depend on the activity of the source and 22.f. 1.1 ~~~~-~~~~~~~~ t?F!YyDI"S
For
of the ~ack~round. low-level counting one These may be due to faults in the counting equip-
has to reduce the backgromd by the use of nzas- ment, personal errors in recording results or oper-
sive shielding, careful material selection for the ating the equipment, or errors in preparing the
components of the counter, the use of such sample. The presence of such errors may be