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Lanthanum in NiMH Batteries

Posted: 13 May 2018, 20:41
by Hans-Jörg

A short time ago I found that lanthanum is used in NiMH batteries. As lanthanum contains a small amount (about 0.09 %)
of an instable isotope (La-138) with a half-life of 1011 years, I tried to detect it in the batteries. It is similar to potassium-40, where the half-life is shorter (1.3*109 years), but the amount smaller (0.01 %). La-138 gives two peaks, 789 keV (35%) and 1436 keV (65%).
So I put some batteries of different brands and sizes, about 600 gram, in my shield In front of the scintillator.

My system: 2’X2’ NaI(Tl), GS-1100A, shield 20-40 mm Pb, 2mm Sn, 2mm Cu

The peak at 789 keV comes from La-138, but the peak at 1430 keV can (at least partially) come from K-40.
My calibration is not very precise.

Greetings from Germany,


Re: Lanthanum in NiMH Batteries

Posted: 14 May 2018, 16:11
by Steven Sesselmann

Well spotted, it's always interesting when someone finds another unexpected source.


Re: Lanthanum in NiMH Batteries

Posted: 15 May 2018, 22:19
by Peter-1
A very interesting post. In order to know the intensity of La138 i made the following calculation.
100 gram La2O3 has 85% of La. In La there are 0,09% of La138. This results in 76,5 mg La138 from 100 gr La2O3.
The activity from La138 is 939 kBq / kg. So the activity from 100gr La2O3 is 72 Bq. I hope i did not make a mistake in the calculation. Is this ok ?


Re: Lanthanum in NiMH Batteries

Posted: 18 May 2018, 22:57
by Peter-1

I bought a few grams of lanthanum oxide and wanted to see whether the spectrum is.
I think the spec is well and the peak at 1435,8 keV is exact and not to to be confused with K40.


Re: Lanthanum in NiMH Batteries

Posted: 07 Nov 2019, 07:02
by gwgw
50g of "high purity (99.9%)" Lanthanum. Has some weak photopeaks from thorium byproducts though (notably Pb-212)