Environmental Engineering FOURTH EDITION

Radioactive Waste 339

of iodine is 15 days and a patient injected with 1-131 produces about 3.5 L of urine a
day, what will be the specific activity (in BqL) of the patient’s urine on the 10th day
after injection? What will be the specific activity in curies per liter (Ci/L)?
16.4 Write nuclear reactions for the following, identifying the product elements
and particles:

a. Fusion of two deuterium atoms to form He-3,

b. Beta decay of Sr-90,

c. Beta decay of Kr-85,

d. Neutron emission from Kr-87, and

e. Decay of Th-230 to Ra-226.

16.5 The dose in Problem 16.3 is adjusted not to exceed 0.5 Gy in 24 h. Calculate
the somatic risk in LCF from this dose. If there were a threshold of adverse effect at
0.2 Gy, would there still be somatic risk?
16.6 How many gams of Cs-137 are produced during each 24-h day of operation
by a nuclear power plant that has an electrical output capacity of 750 MW,? How
many grams would be left if this amount were allowed to decay for 100 years?
16.7 From Table 16-4, calculate the energy absorbed by a 130-lb female in
one year from natural (nonanthropogenic) sources of ionizing radiation. Repeat the
calculation for a 175-lb male. What assumptions did you make?
(one in a million) per source of radioactivity
per year acceptable. Calculate the dose, in sieverts of low-level gamma radiation that
corresponds to this risk, assuming the linear nonthreshold theory.
16.9 ’The EPA has set a standard for the WIPP TRU waste repository as follows:
in the first 10,OOO years after closure, the probability that 1/10,000 of the plutonium
activity in the repository can leak out is 0.1, and the probability that 10 times this amount
of plutonium activity can leak out is 0.001. Show this standard in a two-dimensional
graph. What leak rate would have a probability of l? (Hint: plot probability on the
vertical axis and leak rate on the horizontal axis.)

16.8 The EPAconsiders arisk of

16.10 The first three steps in the 238PU decay chain are

238 94Pu +. 2;;u +. 2;;Th.

The half-lives of these three radionuclides are Pu-238 87 years, U-234 248,000 years,
and Th-230 73,400 years. Solving a series of equations like Eq. (16.1), and starting
with 10 g of PU-238, write an equation for the amount of Th-230 formed as a function
of time. This is not a trivial problem! If you cannot solve the problem analytically, try
solving by iteration using a spreadsheet program, and plot the results.
16.11 Analysis indicates that 99% of the risk from spent nuclear fuel is due to
three radionuclides: Sr-90, (3-137, and CO-60. As much as 99.7% is due to these three
plus Pu-238. What analyses would have been done to arrive at these estimates? What
do these estimates suggest about long-term disposition of spent nuclear fuel? (There
is no “right answer” to this question.)