B-8 Strontium 90 Source

Hi, It’s Xmas season so I figured I’ll give myself a little present, a strontium 90 check source! It is a B-8 check source from 1984 with the activity of 200kBq at the start. Today, 1.5 half-lives later, the activity of the check source is around 80.6kBq but it still is very radioactive!

B-8 Sr90 source sealed in an epoxy inside of DP-5V’s beta shield

During fission, like in nuclear bombs or reactors, around 6% of U-235 turns into Strontium 90. Unlike Cesium which emits beta and gamma radiation, Strontium emits only beta radiation which makes it much harder to detect. Strontium 90 has a half-life of around 29 years and it decays into Yttrium 90 that has half-life of 64h which then decays into stable Zirconium 90.

What makes Strontium 90 dangerous is the fact that it is chemically very similar to calcium. This means that if it is ingested, our body thinks strontium is calcium and it accumulates in our bones which in the long run can cause bone cancer. Because of this Strontium 90 is one of the most dangerous elements found in nuclear fallout.

My source comes from a DP-5V geiger counter. B-8 sources have been used also on DP-5A, DP-5B, DP-63-A to name a few.

B-8 Sr90 source with some epoxy left

When measured with my Polaron Pripyat, the source has maxed out the scale on my meter which is 200uSv/h so I reached for my trusty Terra-P. The reading seemed to be around 420uSv/h which if you ask me is pretty hot.

Luckily Strontium 90 is a beta only source meaning it is relatively easy to stop it. Here you can see that a simple beta shield made from steel pipe stops all radiation.


  • Hi,

    was there a reason why you kept the Sr-90 source partially covered in dried resin? I’ve heard you could either remove it using hot air gun, in almost boiling water or by soaking in acetone.


  • you should better blcvk betas with low Z material! to avoid turning the beta-energy into gamma-energy(bremsstrahlung) better take plexiglass, perspex, instead of steel.

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