Problem 52075. Radioisotope Thermoelectric Generator (RTG)

Created by David Hill

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Given an isotope's atomic mass (in amu), half-life (in years(a) or days(d)), and average kinetic energy absorbed (of emitted decay alpha or beta particle and recoiled atom in MeV), output the power (watts) per gram (of the pure isotope) that could be achieved in an RTG with 100% efficiency (rounded to 5 decimal places). Output the time (in years) that 1 kilogram of the isotope could produce at least 100 watts (rounded to 3 decimal places). One year equals 365.25 days.
For example, Tritium (H-3) has an atomic mass of 3.01604928 amu, has a half-life of '12.32a' (a==years), and it's decay produces a Beta(-) particle that emits with an average kinetic energy (plus recoil KE of nucleus) of 0.005683 MeV.
Outputs:
p = 0.32412 (in watts/gram)
t = 20.901 (in years)

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Last Solution submitted on Jul 05, 2021

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William on 18 Jun 2021

David,
All my answer agree with your to many decimal places except problems 4 and 5, which are different by 1e-5 or 1e-6. I can't tell whether it is p or t that is different.

David Hill on 18 Jun 2021

Added tolerance

William on 18 Jun 2021

Thanks, but it didn't help. My results for 4 and 5 (and *only* for 4 and 5) are different by a *relative* error of 1e-5 and you put in an *absolute* tolerance of 1e-7. That is something like a relative error of nearly 1e-11. I don't think we're going to make it unless we figure out why the target values in those two cases are so far out of line with the others.

David Hill on 19 Jun 2021

I used the following constants:
Av=6.02214199e23;
1.6021773e-13(J/MeV);
1year=365.25 days

William on 19 Jun 2021

I see. I have checked on the web and there seems to be a wide disagreement on the conversion factor between amu and kg. After the first 4 digits, all bets are off. Using your value of Av makes the cases 4,5 work though. Thanks!

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Problem 52075. Radioisotope Thermoelectric Generator (RTG)

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Problem 52075. Radioisotope Thermoelectric Generator (RTG)

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