Collecting a spent nuclear fuel fragment at Chernobyl

**Please watch in HD format for best results**

The area surrounding the incomplete natural-draft cooling towers at ChNPP's Unit 5 construction site is littered with local hot spots that are easy to find with a scintillation detector. In this video, I dig up one of these hot spots, and learn that the object responsible for the prominent radiation is a hard black fleck a mere 0.5 mm on a side.

What is it? I collected the specimen and brought it back to the Interinform hotel for further explorations. The CDV-700 Geiger probe measures 35-40,000 cpm on contact with the beta window closed, translating into about 60 milliroentgen / hr and an activity of about 40 microcuries by comparison with other, known Cs-137 sources. Next I illustrate a rudimentary form of scintillation gamma spectrometry making use of my netbook's sound card and a clever piece of free pulse analysis software called PRA, written by Australian physicist Marek Dolleiser. This spectrometer arrangement works on the AC-coupled linear scintillation pulses from the Ludlum 12 preamp, and displays a pulse-height spectrum that conclusively identifies the medium-lived fission product Cs-137 as the nuclide responsible for all the gamma radiation from this particle. No surprise.

About the only reasonable assumption based on the high activity (~20 mCi / g) is that this particle is a fragment of spent fuel that was ejected from Unit 4 at the time of the accident there. In color and appearance it is consistent with sintered uranium dioxide fuel, and the activity is broadly consistent as my calculation at the end of the video shows.

Category:

Science & Technology

Tags:

• nuclear
• radioactive
• geiger counter
• scintillation
• scintillator
• gamma spectroscopy
• gamma spectrometry
• gamma
• cs-137
• cesium
• radiation
• radioactivity
• hot particle
• chernobyl
• chornobyl

[overunitydotcom]

P.S: Can you feel the radiation, if you have this fragment on your finger tip ? Does it give some kind of tickling sensation on your skin ?

Many thanks.

Regards, Stefan.

[Thallium208]

@overunitydotcom There is no sensation from radiation at this low intensity.

[overunitydotcom]

I wonder how many atoms this small fragment have and why does it all radiate so long at all

these years. As each click on your geiger counter is probably one or more atoms splitted and releasing gamma or alpha or beta radiation, it surely must have trillions of atoms in this small piece, if it has 20.000 splits per second ??

otherwise after 26 years these splitting of atoms should have already stopped ? WHat half life

does it have ?

[Thallium208]

@overunitydotcom As the video shows, I estimated the Cs-137 activity to be ~40 microcuries, or 1.5 million decays per second. Sr-90 is the other major medium-lived nuclide present in spent fuel. It probably accounts for a similar activity in this piece, but emits no gamma rays. Both Sr-90 and Cs-137 have 30-year half lives.

[overunitydotcom]

Couldn´t you get skin cancer by placing this on your finger ?

What is the probability to get skin cancer for how long of an exposure to your skin of this hot

UO2 fragment ?

[Thallium208]

@overunitydotcom It's possible to get cancer, sure. A formal calculation of the risk would be too complicated to get into here, because it would entail modeling the shallow dose from poly-energetic beta particles.

[marmaladekamikaze]

@Thallium208

were you wearing a dosimeter? I'd love to know your total man!

[81lmc7101]

Great! I want to find something like this!

[MassimoC86]

Hi, Interesting video. Could you have shipped that little fragment to yourself in a lead container?