A radiation worker is to perform radiological work on Cs137

A radiation worker is to perform radiological work on Cs-137 source. a) Wliat particles does this source emit? b) Wliat is the range of charged particles emitted from this source in iron? c) What fraction of gamma ray flux emitted by Cs-137 is blocked by 1 nun iron slab?

Solution

a. About 95 percent decays by beta emission to another metastable nuclear isomer of barium: barium-137m (137mBa, Ba-137m). The remainder 5 percent directly populates the ground state of barium-137, which is stable.

b. Theoretically the range is infinite. The particles would go till infinity. with facing decrease in the intensity. If there is any other specific characteristic say decrease in the intensity by 50% or some other parameter like this please feel free to ping me back.

c. I_x=I_o*exp(-mu*x)
So x = 1mm, and mu = linear attenuation coefficient of Cs-137 (.655 for iron at 500 keV)
and beta decay is precisely of 512 keV
therefore calculating the ratio of Ix/Io = exp(-.655*0.001)
so it is equal to 99.93 % so only a 0.07 % decrease in the intensity of beta decay.

Please refer this page to get a better understanding:
1. https://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/Attenuation_of_Gamma-Rays
2. https://en.wikipedia.org/wiki/Caesium-137

If you have additional doubt about the same question, feel free to reach out to me at shivenrastogi@gmail.com