It Was Another Misunderstanding Or Another Joke?

@Northwest thats how Trump administration picture it .

@Khenpal1 That the "official" explanation? Ye Gods!

@ArishMell well, its just him 🍌

@Khenpal1 The two main radioactive isotopes used are

Pu-239, which (as @Northwest pointed out), has a "half-life" of 24,110 yrs.

U-235, with a half-life of 7.04E8 years.

To make use of the exponential decay form, we use these λ-parameters by defining

e^{-λ_s t_{s, 1/2}} ≡ 1/2 = 2^{-1}

for any given "species" s of radioactive nuclide.

Taking the natural logarithm of both sides

-λ_s t_{s, 1/2} = -ln(2)

so

λ_s = ln(2) / t_{s, 1/2}

(The factor "ln(2)" gives rise to the 0.693 which one often sees in textbooks, an approximation to the value.)

This allows us to estimate the fraction of UN-fissioned nuclei of species s which are left over; the decay follows

N_s(t) = N_s(0) * e^{-λ_s t}

where N_s(0) = the original number of nuclei (at time t = 0). So the FRACTION of UN-fissioned nuclei is estimated as

fraction ≡ N_s(t)/N_s(0) = e^{-λ_s t}

For

Pu-239
λ_{Pu-239} = ln(2) / 24,110 yr
≈ 2.875E(-5)/yr

So after 20 yrs,
fraction_{Pu-239} = e^{-(2.875E(-5)/yr)*20 yr}
≈ 0.999425 * 100% = 99.9425%

Since U-235 has a half-life over FOUR orders of magnitude bigger, there is FAR less difference.

You could also solve for when the fraction would be 99%; for Pu-239

e^{-(2.875E(-5)/yr)*t} = 0.99
t = -ln(0.99) / (2.875E(-5)/yr)

or

t = 349.58 yr

A bit more than 20...

@SomeMichGuy The reason sovjets did testing their nukes was in theory you have calculation , but in pracice nukes were never used as weapon. Whats freak Putin is by blowing one nuke once a year is reasuring the things work.

@SomeMichGuy [media=https://www.youtube.com/watch?v=IxPuho_9FwE]

@jefferson huh