# Difference between revisions of "Solutions 2"

1:

1. 1000g Th(NO3)4 = 2.083 mol arrow N(Th)= 1.25 1024 atoms. This is natural thorium, where the equilibrium in Th-series will lead to equal aktivity of 232Th and 228Th. Since 232Th has a incredibly long half-life and 228Th is short compared to this and we can approximate N(Th)N(232Th)=1.25 10^24 The disintegration for both is 1.96106Bq.
2. 6.43 10-8g
3. 10000 Bq 228Ra = 2.62 1012 atoms = 90% arrow 100% 2.92 1012 atoms. If 232Th is N1 and 228Ra is N2 we can use the formulas for mother/daughter realations: Alternatively it can be solved by using D(228Ra) = 11 111Bq:
4. 224Ra is created from 228Th immeasurable amounts of 228Th is created in three days, creation of new 224Ra can therefore be ignored. D0(224Ra)=D0(228Th)=1.36106 Bg, and we get a normal decay:
5. 228Ac, 220Rn,216Po, 212Pb, 212Bi, 212Po.

2:

1. When T= 0 it's only the natural isotopes of uranium: 238U, 235U and 234U.
2. D(238U)=D(234U) 12.5 kBq, D(235U) = 575 Bq.
3. When t = 23.5 h there is created some 234Th and some 234Pa, but creation of other daugthers from 238U is negligible. From the 235U there is created231Th
4. D(238U) = D(234U) =D0,
D(234Th) = D(234Pa) = 376 Bq,
D(235U) = D0,
D(231Th) = 287.5 Bq.
5. When t = 23 days the same radionuclides are present.
6. D(238U) = D(234U) =D0,
D(234Th) = D(234Pa) = 6250 Bq,
D(235U) = D0,
D(231Th) = D(235U) =575 Bq.
7.  when t = 1.0 y the same radionuclides are present.
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