PAGE 7-1 ANSWERS TO END-OF-CHAPTER QUESTIONS CHAPTER 7: THE FIRES OF NUCLEAR FISSION Emphasizing Essentials 1. Give two ways in which an atom of carbon can differ from another atom of carbon. Then give three ways in which all carbon atoms differ from all uranium atoms. Answer: One carbon atom can differ from another in the number of neutrons (such as C-12 and C-13) and in the number of electrons (we won’t be studying carbon ions, but these do exist). All carbon atoms differ from all uranium atoms in their number of p, n and e and also in their chemical properties. 2. Representations such as 14 N or 15 N give more information than simply the atomic symbol N. Explain. Answer: The symbol N represents the element nitrogen and stands for the naturally occurring mixture of all isotopes. The symbols 14 N and 15 N represent very specific isotopes with mass numbers of 14 and of 15, respectively. 3. a. How many protons does an atom of 94 239 Pu contain? b. What element contains one more proton than uranium? Two more? c. How many protons does radon-222 contain? Answer: a. 94 protons b. Np (neptunium), Pu (plutonium) c. 86 protons 4. Determine the number of protons and neutrons in each of these nuclei. a. C-14 (radioactive) b. C-12 (stable) c. H-3 (tritium, a radioisotope of hydrogen) d. Tc-99 (a radioisotope used in medicine) Answer: a. C-14 has 6 protons and 8 neutrons b. C-12 has 6 protons and 6 neutrons c. H-3 has 1 proton and 2 neutrons d. Tc-99 has 43 protons and 56 neutrons
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PAGE 7-1
ANSWERS TO
END-OF-CHAPTER QUESTIONS
CHAPTER 7: THE FIRES OF NUCLEAR FISSION
Emphasizing Essentials
1. Give two ways in which an atom of carbon can differ from another atom of carbon. Then give
three ways in which all carbon atoms differ from all uranium atoms.
Answer:
One carbon atom can differ from another in the number of neutrons (such as C-12 and C-13)
and in the number of electrons (we won’t be studying carbon ions, but these do exist). All
carbon atoms differ from all uranium atoms in their number of p, n and e and also in their
chemical properties.
2. Representations such as 14
N or 15
N give more information than simply the atomic symbol N.
Explain.
Answer:
The symbol N represents the element nitrogen and stands for the naturally occurring mixture of
all isotopes. The symbols 14
N and 15
N represent very specific isotopes with mass numbers of
14 and of 15, respectively.
3. a. How many protons does an atom of
94
239Pu contain?
b. What element contains one more proton than uranium? Two more?
c. How many protons does radon-222 contain?
Answer:
a. 94 protons
b. Np (neptunium), Pu (plutonium)
c. 86 protons
4. Determine the number of protons and neutrons in each of these nuclei.
a. C-14 (radioactive)
b. C-12 (stable)
c. H-3 (tritium, a radioisotope of hydrogen)
d. Tc-99 (a radioisotope used in medicine)
Answer:
a. C-14 has 6 protons and 8 neutrons
b. C-12 has 6 protons and 6 neutrons
c. H-3 has 1 proton and 2 neutrons
d. Tc-99 has 43 protons and 56 neutrons
PAGE 7-2
5. E = mc2 is one of the most famous equations of the 20th century. What do the symbols in the
equation represent?
Answer:
E represents energy, m represents mass lost in a nuclear transformation, and c represents the
speed of light.
6. Give an example of a nuclear equation and of a chemical equation. In what ways are the two
equations alike? Different?
Answer:
Nuclear equation:
Chemical equation: CH4 + 2 O2 CO2 + 2 H2O
In a chemical equation, the elements do not change their identities in the process of being
converted from reactants to products. Even though they are combined differently, the same
number of atoms of each kind must appear on both sides of the equation. Usually only the
symbols for the elements are given, not their atomic or mass numbers. In a nuclear equation,
the identity of the elements may change, or at least the mass number may change. The values
for both the atomic and mass numbers are often included.
7. This nuclear equation represents a plutonium target being hit by an alpha particle. Show that
the sum of the subscripts on the left is equal to the sum of the subscripts on the right. Then do
the same for the superscripts.
Answer:
Subscripts: 94 + 2 = 96 on the left, 96 + 0 = 96 on the right
Superscripts: 239 + 4 = 243 on the left; 242+1=243 on the right
8. For the nuclear equation shown in the previous question,
a. suggest how the
2
4He was produced.
b.
0
1n is a product. What does this symbol represent?
c. explain why curium-243 is written in square brackets. Hint: See equation 7.1.
Answer:
a. The alpha particle may have come from the radioactive decay of another radioisotope.
b. n1
0 represents a neutron.
c. Curium-243 represents an unstable intermediate in the nuclear reaction. This isotope has an
extremely short lifetime, decomposing immediately upon formation into Cm-242 with an
accompanying neutron.
9. Californium, element number 98, was first synthesized by bombarding an element with alpha
particles. The products were californium-245 and a neutron. What was the target isotope used
in this nuclear synthesis?
PAGE 7-3
Answer:
The target isotope must have been Cm-242. Here is the nuclear equation.
10. Explain the significance of neutrons in initiating and sustaining the process of nuclear fission.
In your answer, define and use the term chain reaction.
Answer:
Neutrons are needed to initiate the process of nuclear fission of U-235.
The fission products include 2 or 3 neutrons that can initiate more fission reactions. In this
manner, a self-sustaining chain reaction can be established in which the products of one
reaction initiate another.
11. Nuclear fission occurs through many different pathways. For the fission of U-235 induced by a
neutron, write a nuclear equation to form:
a. bromine-87, lanthanum-146, and more neutrons.
b. a nucleus with 56 protons, a second with a total of 94 neutrons and protons, and 2 additional
neutrons.
Answer:
a.
b.
12. This schematic diagram represents the reactor core of a nuclear power plant.
Match each letter with one of these terms.
fuel rods
cooling water into the core
cooling water out of the core
PAGE 7-4
control rod assembly
control rods
Answer:
A = control rod assembly, B = cooling water out of the core, C = control rods, D = cooling
water into the core, E = fuel rods
13. Identify the segments of the nuclear power plant diagrammed in Figure 7.6 that contain
radioactive materials and those that do not.
Answer:
The nuclear segment shown on the left in Figure 7.6 contains the reactor core, the heart of the
reactor where energy is produced. The non-nuclear portion is everything in the center and right
of the diagram, and includes the turbine and electrical generators. The non-nuclear portion also
contains the secondary and tertiary water systems, neither of which come into direct contact
with the reactor core.
14. Explain the difference between the primary coolant and the secondary coolant. The secondary
coolant is not housed in the containment dome. Why not?
Answer:
The primary coolant is the liquid surrounding the fuel bundles and control rods, a liquid that
comes in direct contact with the nuclear reactor to carry away heat. The heat from the primary
coolant is transferred to the secondary coolant, water in the steam generators that does not
come in contact with the reactor. The steam generators are separated from the nuclear reactor,
so the secondary coolant is not housed in the containment dome.
15. Boron can absorb neutrons.
a. Write the nuclear equation in which boron-10 absorbs a neutron to produce lithium-7 and an
alpha particle.
b. Boron, like cadmium, can be used in control rods. Explain.
Answer:
a. b. Boron can be used to make control rods because it is a good neutron absorber.
16. What is an alpha particle? How is it represented? Answer these same questions for a beta
particle and for a gamma ray.
Answer:
An alpha particle is a helium nucleus consisting of 2 protons and 2 neutrons. It carries a +2
charge and is represented by α or
2
4He .
A beta particle is an electron. It carries a negative one charge and is represented by the symbol
β or e0
1 .
PAGE 7-5
A gamma ray is a high energy photon emitted from the nucleus of an atom. It is represented by
the symbol γ or 0
0γ.
17. Plutonium-239 decays by alpha emission.
a. Write the nuclear equation.
b. Plutonium is most hazardous when inhaled in particulate form. Explain.
c. Would you expect a sample of Pu-239 to decrease to background level in hours, days, or
years? Explain.
Answer:
a. b. As a particulate, plutonium can be inhaled and become lodged in the lungs. If so, the
ionizing radiation it produces (alpha particles) can cause damage to lung cells. The product
U-235 also is radioactive and can damage tissue in the same way.
c. The half-life of Pu-239 is 24,110 years, so the timescale for a decrease to background level
would be on the order of years (actually more like centuries).
18. Iodine-131 decays by beta emission.
a. Write the nuclear equation.
b. Iodine, radioactive or not, accumulates in the body. Where?
c. Would you expect a sample of I-131 to decay in hours, days, or years? Explain.
Answer:
a. e0
1–
131
54
131
53 + XeI
b. Iodine accumulates in the thyroid gland.
c. The half life of I-131 is 8.5 days, so a sample of I-131 will decay on a timescale of days.
19. Radioactive decay is accompanied by a change in the mass number, a change in the atomic
number, a change in both, or a change in neither. For the following types of radioactive decay,
which change(s) do you expect?
a. alpha emission
b. beta emission
c. gamma emission
Answer:
a. An alpha particle (helium nucleus) consists of 2 protons and 2 neutrons. If a nucleus releases
an alpha particle, both its mass number and its atomic number change.
b. A beta particle is a high-speed electron emitted from the nucleus. This emission can be
thought of as the conversion of a neutron into a proton plus this high-speed electron. If a
nucleus releases a beta particle, the atomic number increases but no change occurs in the mass
number.
c. A gamma ray is a high-energy photon of light. Gamma emission causes no change in either
the atomic number or mass number of the emitting nucleus.
PAGE 7-6
20. In a fashion similar to U-238 (see Figure 7.13), U-235 goes through a series of alpha and beta
decays before reaching a stable isotope. For practice, write the first six, which will bring you to
an isotope of radon. In order, the steps in the full radioactive decay series are a, b, a, b, a, a, a, b,
a, b, a, ending in stable Pb-207. Some steps have accompanying γ radiation, but you may omit
this.
Answer:
235 231 4
92 90 2U Th + He
231 231 0
90 91 -1Th Pa + e
231 227 4
91 89 2Pa Ac + He
227 227 0
89 90 1Ac Th + e
227 223 4
90 88 2Th Ra + He
223 219 4
88 86 2Ra Rn + He
21. Given that the average U.S. citizen receives 3600 Sv of radiation exposure per year, use the
data in Table 7.3 to calculate the percentage of radiation exposure the average U.S. citizen
receives from each of these sources.
a. food, water, and air
b. a dental X-ray twice a year
c. the nuclear power industry
Answer:
a. 2400 Sv compared to a total of 3600 Sv = 67% from food, water, and air
b. 200 Sv compared to a total of 3600 Sv = 5.6% from a dental X-ray twice a year
c. 0.09 Sv compared to a total of 3600 Sv. This depends on proximity to a nuclear power
plant, but in any case is extremely low assuming that no nuclear accidents occur.
22. What percent of a radioactive isotope would remain after two half-lives, four half-lives, and six
half-lives? What percent would have decayed after each period?
Answer:
It may be helpful to construct a chart.
# of half-lives % remaining % decayed
0 100 0
1 50 50
2 25 75
3 12.5 87.5
4 6.25 93.75
5 3.12 97.88
6 1.56 98.44
23. Estimate the half-life of radioisotope X from this graph.
PAGE 7-7
Answer:
The half-life is 6 hours. The mass of the radioisotope falls from 100 mg to 50 mg in 6 hrs, and
then from 50 mg to 25 mg in the next 6 hours.
Concentrating on Concepts
24. The opening lines of this chapter connect acid rain and global warming to burning fossil fuels.
Explain the connection.
Answer:
Burning fossil fuels produces CO2, SO2, and NOx. (Remember, the NOx comes from the heat of
burning, not from the fossil fuels themselves.) SO2, and NOx dissolve in water to create acid
rain. CO2 is a greenhouse gas (see Chapter 3) that contributes to global warming.
25. In Consider This 7.1, you were asked to answer several questions about nuclear power. Ask the
same questions of someone at least one generation older than you and someone younger. In
comparison with your answer, what similarities and differences do you find?
Answer:
Older generations are more apt to remember the lessons of Chernobyl and the fears of Three
Mile Island. Younger generations may know nothing of either, and may have a variety of
opinions. All may be cognizant of the need to reduce carbon dioxide emissions and thus
rethinking nuclear power as an option. All generations may confuse nuclear power with
nuclear weapons.
26. The isotopes U-235 and U-238 are alike in that they are both radioactive. However, these two
isotopes have very different abundances in nature. List their natural abundances and explain
the significance of the difference.
Answer:
The natural abundances of U-238 and U-235 are 99.3% and 0.7%, respectively. U-235 can be
induced to undergo nuclear fission and thus is suitable for nuclear power plants and nuclear
weapons. Because U-235 is so rare, it is very difficult to procure in large quantities or in pure
form. This single fact has severely limited the number of nations that have nuclear weapons.
27. Consider the uranium fuel pellets used in commercial nuclear power plants.
a. Describe one way in which U-235 and U-238 can be separated.
b. Why is it necessary to enrich the uranium for use in the fuel pellets?
PAGE 7-8
c. The fuel pellets are enriched only to a few percent, rather than to 80–90%. Give three
reasons why.
d. Explain why it is not possible to separate the isotopes of uranium by chemical means.
Answer:
a. All means of separation exploit the tiny mass difference between U-235 and U-238. For
example, it is possible to separate them by converting the uranium sample to gaseous UF6 and
then use gas diffusion. A large high-speed centrifuge also can be used to separate these gas
molecules.
b. The uranium must be enriched to provide a critical mass of U-235 to sustain the chain
reaction responsible for energy production in the reactor.
c. First, the enrichment procedure is both expensive and energy intensive, so the minimum
enrichment level capable of sustaining a chain reaction is preferred. Second, reactors using
80-90% fuels have safety concerns due to the increased possibility of an uncontrolled chain
reaction. Third, such reactors would also have significant security issues. The highly enriched
fuel can be used directly in nuclear weapons, making the reactors potential terrorist targets.
d. The difference in the isotopes of uranium is in their nuclear masses. This difference is not
enough to significantly affect the chemical reactivity of the two isotopes. For chemical
separation, the isotopes of uranium would need to behave differently in a chemical reaction of
one sort or another.
28. a. Why must the fuel rods in a reactor be replaced every couple of years?
b. What happens to the fuel rods after they are taken out of the reactor?
Answer:
a. The fuel rods have to be replaced periodically because the fission products build up in them
over time. These fission products absorb neutrons, thus slowing the chain reaction.
b. Once fuel rods are removed, they are placed in pools to cool. If the reactor is in the United
States, the fuel rods are left in storage, usually in the vicinity of the reactor as there is no central
nuclear repository to accept nuclear waste. In many other parts of the world, they are
reprocessed into secondary nuclear fuels.
29. At full capacity, each reactor in the Palo Verde power plant uses only a few pounds of uranium
to generate 1243 megawatts of power. To produce the same amount of energy would require
about 2 million gallons of oil or about 10,000 tons of coal in a conventional power plant. How
is energy produced in the Palo Verde plant, compared with conventional power plants?
Answer:
The Palo Verde power plant produces energy through the process of nuclear fission. Coal and
oil burning plants generate energy by burning fossil fuels.
30. One important distinction between the Chernobyl reactors and those in the United States is that
those in Chernobyl used graphite as a moderator to slow neutrons, whereas U.S. reactors use
water. In terms of safety, give two reasons why water is a better choice.
PAGE 7-9
Answer:
Water is a better choice as a neutron adsorbent than graphite because water does not burn and
because it has a higher specific heat than graphite, and thus can more effectively adsorb and
help dissipate excess heat in the reactor.
31. If you look at nuclear equations in sources other than this textbook, you may find that the
subscripts have been omitted. For example, you may see an equation for a fission reaction
written this way.
a. How do you know what the subscripts should be? Why can they be omitted?
b. Why are the superscripts not omitted?
Answer:
a. The subscript for each element is its atomic number, which can be found in the periodic table
or in a list of elements. The subscript for the neutron is zero, which requires knowing or finding
the charge of a neutron in a reference table.
b. The superscripts cannot be omitted because nuclear equations must specify a specific
isotope and this is something that cannot be determined by looking at the periodic table or
other reference.
32. Using the model of a neutron presented in equation 7.6, explain how a high-speed electron can
be ejected from the nucleus in beta decay.
Answer:
A model for the process of beta decay is that a neutron is (somehow) transformed into a proton
and an electron. The electron is subsequently ejected from the nucleus as the beta particle,
leaving one more proton (and one less neutron) in the nucleus. Thus, the mass number does not
change since the number of protons and neutrons remains constant.
33. Coal can contain trace amounts of uranium. Explain why thorium must be found in coal as
well.
Answer:
Thorium is found with uranium because it found in the natural decay series of uranium.
34. Suppose somebody tells you that a radioisotope is “gone” after about seven half-lives. Critique
this statement, explaining both why it could be a reasonable assumption and why it might not
be.
Answer:
See question #22. After 7 half-lives, 99% of a sample has decayed (reasonably close to being
“gone”). However, the radioactivity actually is not gone, as 0.78% of the sample remains. Thus
if you start with a large amount of a radioactive substance (for example, 2000 pounds), after 7
half-lives have passed you have close to 10 pounds left. This could be considered a sizeable
amount.
PAGE 7-10
35. A website describing an X-ray procedure reports, “Despite its negative connotations, people
are exposed to more radiation on a daily basis than they may realize. For example, infrared
radiation is released whenever there is extreme heat. The sun generates ultraviolet radiation,
and a little exposure to it will tan a lighter skinned person. In addition, the body contains
naturally radioactive elements.” Examine the three examples given in this explanation. Do
they refer to nuclear or electromagnetic radiation?
Answer:
The third example, “naturally radioactive elements” is an example of exposure to nuclear
radiaton. In contrast, the first two examples, IR and UV “radiation” are not nuclear radiation.
Rather, they are electromagnetic radiation. While it may be true that “people are exposed to
more radiation on a daily basis than they may realize,” the explanation fails to differentiate
between nuclear (ionizing) radiation and electromagnetic radiation and thus is misleading.
36. Consider this representation of a Geiger–Müller counter (also called a Geiger counter), a
device commonly used to detect ionizing radiation. The probe contains a gas under low
pressure.
a. How does radiation enter the Geiger–Müller counter?
b. Why does this device only detect radiation that is capable of ionizing the gas contained in
the probe?
c. What are other methods for detecting the presence of ionizing radiation?
Answer:
a. Radiation enters through the thin window shown at the end of the tube.
b. When the gas is ionized, the ions allow an electric current to be established between the
anode and the cathode. If the radiation cannot ionize the gas, no current is generated (and no
radiation is detected).
c. Other methods of detecting radiation include film badges and scintillation counters.
37. Rapidly dividing cells are present in several places in the adult body. These include the skin,
the hair follicles, the stomach and intestines, the lining of the mouth, and the bone marrow.
Match the symptoms listed in Table 7.4 with the type of cell that was affected by the radiation.
PAGE 7-11
Answer:
Dose (rem) Dose (Sv) Likely Effect Cell Type Affected
0–25 0–0.25 No observable effect
25–50 0.25–0.5 White blood cell count
decreases slightly
Bone marrow
50–100 0.5–1 Significant drop in white
blood cell count, lesions
Bone marrow, skin
cells
100–200 1–2 Nausea, vomiting, loss of
hair
Stomach and intestines,
hair follicles.
200–500 2–5 Hemorrhaging, ulcers,
possible death
Skin, hair follicles,
stomach and intestines,
lining of mouth
>500 >5 Death All
38. Exposure to ionizing radiation can cause cancer. A beam of ionizing radiation also can be used
to cure certain types of cancer. Explain.
Answer:
Ionizing radiation can cause cancer by damaging the DNA of a cell. If the cell lives to
reproduce, the cell may be cancerous. However, a beam of strong ionizing radiation, when
directed at rapidly dividing cancer cells, this may kill the cancer cells.
39. Fluorine only has one naturally occurring radioisotope, F-19. If fluorine also occurred in nature
as F-18, would this necessarily complicate the separation of 238
UF6 and 235
UF6? Explain.
Answer:
The current separation is based on the difference in mass (=3) between 238
U19
F6 and 235
U19
F6. If
F-18 existed, two more compounds would be in the mix: 238
U18
F6 and 235
U18
F6. This would
complicate things, because 238
U18
F6 and 235
U19
F6 now only differ by 2 mass units, requiring an
even more careful separation.
40. a. Is depleted uranium (DU) still radioactive? Explain.
b. Is spent nuclear fuel (SNF) still radioactive? Explain.
Answer:
a. Depleted uranium is only weakly radioactive. It is primarily composed of U-238 which has a
half-life of 4.5 x 109 years and thus decays very slowly.
b. Spent fuel from a nuclear power plant is highly radioactive. It contains the fission products
of U-235 which tend to be beta emitters with relatively short half-lives. It also contains the
unburned uranium which is not very radioactive, as noted in part a.
41. It is generally believed that terrorists would be more likely to construct a nuclear bomb using
Pu-239 reclaimed from breeder reactors than using U-235. Use your knowledge of chemistry
to offer reasons for this.
PAGE 7-12
Answer:
Although uranium ore is readily available, the separation of U-235 from U-238 requires very
sophisticated technology such as gaseous diffusion or centrifugation. In contrast, plutonium
comes from spent reactor fuel. The separation of Pu-239 from uranium and other fission
products requires only chemical separations, which are far easier to carry out.
42. Weapons-grade plutonium is almost completely Pu-239. In contrast, the plutonium produced
in the normal operation of a water-cooled power reactor (reactor-grade plutonium) generally
has a higher concentration of heavier isotopes such as Pu-240 and Pu-241. Propose an
explanation for this observation.
Answer:
In a uranium reactor, U-238 absorbs a neutron to form U-239. This subsequently decays to
Np-239 which decays to Pu-239. Recall that there are a lot of neutrons present in the core of a
reactor. Pu-239 can capture one or two of these neutrons to become Pu-240.
43. a. What are the characteristics of high-level radioactive waste (HLW)?
b. Explain how low-level waste (LLW) differs from HLW.
Answer:
a. Besides being highly radioactive, high-level nuclear waste is often in chemical forms that
are highly acidic or basic. It may also contain toxic metals. Because it contains fissionable
plutonium that could be extracted and used to construct nuclear weapons, it is also a security
risk. This waste is a byproduct of the nuclear weapons industry and nuclear power plants.
b. Low-level radioactive waste is waste contaminated with smaller quantities of radioactive
materials than high-level waste, and specifically excludes spent nuclear fuel. Examples of
low-level waste are discarded smoke detectors, radioactive pharmaceuticals, and the waste
materials from medical tests involving radioactive isotopes.
Exploring Extensions
44. Alchemists in the Middle Ages dreamed of converting base metals, such as lead, into precious
metals—gold and silver. Why could they never succeed? Today could we convert lead to gold?
Explain.
Answer:
Alchemists were perhaps the first practical chemists, but they did not have the advantage of
knowing anything about atomic structure or nuclear reactions. No chemical reaction can
produce gold from another element; a nuclear reaction is required. Even if they had envisioned
a nuclear reaction that would produce gold from another isotope, they clearly did not have the
means to accomplish this .The situation has indeed changed, and modern day chemists could
design experiments to change lead into gold. The question now is why anyone would want to,
as the cost would be prohibitive.
PAGE 7-13
45. Make a time line of nuclear history, putting at least a dozen dates on your line. For
example, start with Becquerel’s discovery of radioactivity in 1896. Other candidates for
inclusion are Chernobyl, Hiroshima, the opening of the first commercial reactor, the discovery
of various medical isotopes, the use of uranium glazes in Fiesta ware, and the Nuclear Test Ban
Treaty.
Answer:
The Department of Energy website http://www.mbe.doe.gov/me70/history/doe_timeline.htm
is a ready source of this information. The site is divided into decades and students will find
ample events to enter onto their timelines.
46. The Tennessee Valley authority’s nuclear reactor, Browns Ferry 1, did not operate
between 1985 and 2007. As this book went to print, it was back on line. What are the current
news reports?
Answer:
The Browns Ferry 1 reactor was re-started on May 22, 2007. Check the Tennessee Valley
Authority (TVA) website at http://www.tva.gov/sites/brownsferry.htm.
Although the restart was hailed by many, the TVA did cite cost overruns. A news article in the
Huntsville Times on December 15, 2007 reported that “Unit 1 has been off-line five times
since it returned to operation and the Nuclear Regulatory Commission recently conducted an
enhanced inspection, trying to understand the reason for the unplanned shutdowns. The NRC
has not yet released the findings from that inspection.”
47. Explain the term decommission, as in “decommissioning a nuclear power plant.” What
technical challenges are involved? You might want to start by learning more about the
decommissioning of the Yankee Rowe facility (see Table 7.1). The resources of the Web can
help you.
Answer:
Decommissioning a nuclear power plant means shutting it down permanently. The Nuclear
Regulatory Commission’s website http://www.nrc.gov is a good source of information on the
status of nuclear power plants, functional or decommissioned, in the United States. Four stages
are involved with decommissioning:
1. removal of spent fuel from core and the spent fuel pools.
2. moving spent fuel to interim storage or reprocessing plant.
3. waiting until part of the radioactivity has decayed
4. dismantling of the plant
48. Einstein’s equation, E = mc2 applies to chemical changes as well as to nuclear reactions. An
important chemical change studied in Chapter 4 was the combustion of methane, which
releases 50.1 kJ of energy for each gram of methane burned.
a. What mass loss corresponds to the release of 50.1 kJ of energy?