Soviet Beta Radiometer KRB-1 (КРБ-1)

Hello together, I´m Stanislav, Lucian´s friend, and today we are talking about some soviet stuff 🙂

Fig.1: KRB-1

Just found this jewel on a local auction in Ukraine for 20€!
It’s a KRB-1 beta radiometer made for soviet nuclear fleet back in 1986. It comes in a stylish black case and utilizes a big SI-8B and a tiny SI-19BGM pancake,
it is one of the most sensitive soviet made radiometers. You can see both counters on the picture below:

Fig.2: Probe without beta shield

Fig.3: Probe with a beta shield

I say radiometer, because it measures only beta radiation and indicates gamma. In soviet physics school all particle radiations like alpha, beta and neutrons were handled as fluxes an measured in particles/min*cm² (or decays/min*cm²). This device has a darn high range: from 10 to 10⁷ decays/min*cm², which is enough for almost everything, starting with low active rocks and ending at Chornobyl echo, where most pocket dosimeters freak out.

Fig.4: Radioactive background in my room, gamma.


I’ve looked inside to fix the arrow being stuck in the middle of the scale. Check all those golden IC’s and transistors, as well as tantalum K53-1 and palladium KM series capacitors! People didn’t have enough toilet paper in that time, but military had everything… Anyway, the schematics is rather easy, it´s a classic integrating device with different RC nets and a blocking generator for HV production.

Fig.5: Inside the radiometer

It detects K-40 beta’s from a rock crystal bowl, which is twice higher than background! And it notices pretty inactive uranium glass from around 20 cm. Take a look:

Fig.6: Beta-radioactivity of my rock crystal bowl

Fig.6: Beta-radioactivity of my uranium glass bowl. Notice that it´s x10 scale!

A bit more active sources make SI-8B to glow orange in the darkness. Darn, it´s first time I can directly measure activity of that Б-8 checksource (Sr-90/Y-90) from a DP-5 series dosimeter! 20000 imp/min*cm².

Fig.7: Glowing SI-8B

This device, like DP-5 series, needs originally A336 type batteries which are no longer being produced. I found 3 of them completely destroyed in it´s battery holder. There is actually a way to find such elements: a flat 4,5V battery contains 3 such elements, just enough for these geigers. But they are rather rare, so I used 3 AA batteries and 10 cent coins to make the batteries longer.

Fig.8: A336 battery and battery holder

The sad part is that it doesn’t have a reset button, so you need to wait 200 seconds at x1 range to settle the readings. And no clicker Well, at least, SI-8B clicks pretty loud 🙂

Author: Stanislav Prytuliak