Rate of Nuclear Disintegration
403
NUCLEAR ENERGY
In all the nuclear equations we have just written, we have shown that there is no
change in the sum of the mass numbers. However, there actually is a small
change in mass, and this change is one of the most important properties of
nuclear reactions. Consider the nuclear fusion of hydrogen and tritium:
!H + ?H -» £He
The sum of the weight (per mole) of the products is 0.0246 g less than the sum of
the weights of the reactants. In the Bethe cycle (the series of reactions in the
sun by which solar energy is produced), 4 moles of protons weighing 4.03228 g
are converted to 1 mole of helium weighing 4.00336 g, a loss of 0.02892 g. In the
nuclear fission of
2 iJjU,
2
i|U + in —* fission products + 2 or 3 Jn
there is a loss of 0.205 g/mole. The weight that is lost is converted to energy,
according to the Einstein equation:
E = me
2
where E is the energy (in ergs) liberated by converting mass to energy, m is the
mass (in grams) converted to energy, and c is the velocity of light (3 x 10
10
cm/sec).
The ergs of energy may be expressed as calories if we remember that 1 cal =
4.184 x 10
7 ergs.
1. In nuclear fusion, 0.0246 g gives 5.29 x 10
11 cal = 0.529 Teal.
2. In the Bethe cycle, 0.02892 g gives 6.22 x 10
11 cal = 0.622 Teal.
3. In the nuclear fission, 0.205 g gives 4.41 x 10
12 cal = 4.41 Teal.
RATE OF NUCLEAR DISINTEGRATION
Radioactive substances vary in their activity—that is, in the rate at which they
disintegrate. Each radioactive isotope disintegrates at a rate that is unaffected
by temperature, pressure, or external conditions. As discussed on pp. 232-234,
this rate of disintegration
_ dN_
dr
403
NUCLEAR ENERGY
In all the nuclear equations we have just written, we have shown that there is no
change in the sum of the mass numbers. However, there actually is a small
change in mass, and this change is one of the most important properties of
nuclear reactions. Consider the nuclear fusion of hydrogen and tritium:
!H + ?H -» £He
The sum of the weight (per mole) of the products is 0.0246 g less than the sum of
the weights of the reactants. In the Bethe cycle (the series of reactions in the
sun by which solar energy is produced), 4 moles of protons weighing 4.03228 g
are converted to 1 mole of helium weighing 4.00336 g, a loss of 0.02892 g. In the
nuclear fission of
2 iJjU,
2
i|U + in —* fission products + 2 or 3 Jn
there is a loss of 0.205 g/mole. The weight that is lost is converted to energy,
according to the Einstein equation:
E = me
2
where E is the energy (in ergs) liberated by converting mass to energy, m is the
mass (in grams) converted to energy, and c is the velocity of light (3 x 10
10
cm/sec).
The ergs of energy may be expressed as calories if we remember that 1 cal =
4.184 x 10
7 ergs.
1. In nuclear fusion, 0.0246 g gives 5.29 x 10
11 cal = 0.529 Teal.
2. In the Bethe cycle, 0.02892 g gives 6.22 x 10
11 cal = 0.622 Teal.
3. In the nuclear fission, 0.205 g gives 4.41 x 10
12 cal = 4.41 Teal.
RATE OF NUCLEAR DISINTEGRATION
Radioactive substances vary in their activity—that is, in the rate at which they
disintegrate. Each radioactive isotope disintegrates at a rate that is unaffected
by temperature, pressure, or external conditions. As discussed on pp. 232-234,
this rate of disintegration
_ dN_
dr