Table of Nuclides

Frequently Asked Questions

  Back to Home
2.1: Decay Data
Decay heat (137Cs decay)

I have a question about the decay mode of 137Cs. You state in the periodic table that:


Cs-137 is usually separated from rad waste of nuclear fuels. This nucide is useful for a level gauge, a gamma radiography.

But you list beta decay as the decay mode for 137-Cs not gamma decay. I presume gamma decay comes from 137-Ba with the energy given below of 661.657 kev?

Thanks for your help! I am actually interested in computing the heat released by decay of 137-Cs (or probably 137-Ba).

Beta ray:

   Max.E(keV)    Avg.E(keV)     Intensity(rel)
     1176( 1)   416.264(72)       5.6( 2)
    892.1( -)   300.570(68)    5.8E-4( 8)
   514.03(23)   174.320(61)      94.4( 2)

Gamma ray:
  Energy(keV)    Intensity(rel)
    283.5( 1)    5.8E-4( 8)
  661.657( 3)      85.1( 2)

Cs-137 decay with 514 keV beta (with 94.4 64d850rob.). Then transit to
ground state of Ba-137 with emission of 662 keV gamma.
The gamma ray is usually emitted after beta- or alpha-decay.
If the nuclide emits only gamma ray, the nuclide was in meta-state and
fall into ground state. In this case we denote IT (internal transition).
For, Cs-137 heating, the most dominant contribution is from beta
(or electron). Since the electron has very short range compare with
(or photon). The heat corresponding to gamma will be transfered to long
distance with the gamma-ray. Again, other will be by neutrino which will
transfer heat.
So, the heat generated per disintegration will be about
 (174.3 x 0.944 + 416.3 x 0.056) keV
For more detailed caluclation, you need
 - beta energy distribution
 - electron-photon transport calculation with real geometry.
However the above thumb estimation will be exact within 10 - 20 0.000000e+00rror.

Best Regards,
> Beta ray:
>     Max.E(keV)    Avg.E(keV)     Intensity(rel)
>       1176( 1)   416.264(72)       5.6( 2)
>      892.1( -)   300.570(68)    5.8E-4( 8)
>     514.03(23)   174.320(61)      94.4( 2)
> Gamma ray:
>    Energy(keV)    Intensity(rel)
>      283.5( 1)    5.8E-4( 8)
>    661.657( 3)      85.1( 2)

Seek Word:

Back to Full List       Send e-mail: