Physics for Scientists and Engineers with Modern Physics, Technology Update
9th Edition
ISBN: 9781305401969
Author: SERWAY, Raymond A.; Jewett, John W.
Publisher: Cengage Learning
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Chapter 45, Problem 5OQ
To determine
The consequences of removing the moderator from a nuclear reactor.
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Students have asked these similar questions
The Canadian CANDU reactor uses natural uranium, with the moderator consisting
of heavy water (deuterium oxide). If the moderator were removed, what would
happen to the uranium in the reactor?
Nothing. The reactor would continue to run normally.
The fission reactions would stop.
The reactor would blow up like an atomic bomb.
As explained in the previous section, if you want to have a nuclear reaction chain starting into
your reactor, you need to enrich the uranium to have more uranium 235 available. It is assumed
that you need to have about 4% of uranium 235 in order to maintain the reaction chain and to
produce enough neutrons. Those neutrons are, however, too energetic to induce another fission
reaction, it is needed first to reduce their energy. In most reactors, this is the role of the water
located inside.
1) Explain how the energy is stored inside the neutrons
2) How can the water reduce this energy?
3) Is the water the only thing able to act as moderator?
4) What is the effect of the moderator on the cross-section of the atoms of uranium 235?
In order to have the fission reaction to start a nuclear reactor, you need to be able to produce as
many neutrons needed in order to maintain the reaction stable during the time. If you have too
few fissions, then there will be a lack of neutrons and this will turn off the reaction chain. If
you have too many fissions, then there will be an excess of neutrons, and you will end up with
a Chernobyl-like issue. This is called the criticality of the reactor. Hence, you need to compute
the exact amount of fuel to put inside your reactor, in order to maintain the reaction chain. Such
a calculus of criticality is very complex, and out of reach for this class. It is, however, possible
to estimate it, with the Oklo reactor.
The Oklo reactor is located near Franceville, in Gabon. It is the only natural nuclear reactor
known so far. At some point in history, what would become the mining pit of Oklo was a place
containing a lot of uranium and water, which acted as a moderator, hence allowing the…
Chapter 45 Solutions
Physics for Scientists and Engineers with Modern Physics, Technology Update
Ch. 45.1 - When a nucleus undergoes fission, the two daughter...Ch. 45.2 - Prob. 45.2QQCh. 45.3 - Prob. 45.3QQCh. 45.4 - Prob. 45.4QQCh. 45 - Prob. 1OQCh. 45 - Prob. 2OQCh. 45 - Prob. 3OQCh. 45 - Prob. 4OQCh. 45 - Prob. 5OQCh. 45 - Prob. 6OQ
Ch. 45 - Prob. 7OQCh. 45 - Prob. 8OQCh. 45 - Prob. 9OQCh. 45 - Prob. 1CQCh. 45 - Prob. 2CQCh. 45 - Prob. 3CQCh. 45 - Prob. 4CQCh. 45 - Prob. 5CQCh. 45 - Prob. 6CQCh. 45 - Prob. 7CQCh. 45 - Prob. 8CQCh. 45 - Prob. 1PCh. 45 - Prob. 2PCh. 45 - Prob. 3PCh. 45 - Prob. 4PCh. 45 - Prob. 5PCh. 45 - Prob. 6PCh. 45 - Prob. 7PCh. 45 - Prob. 8PCh. 45 - Prob. 9PCh. 45 - Prob. 10PCh. 45 - Prob. 11PCh. 45 - Prob. 12PCh. 45 - Prob. 13PCh. 45 - Prob. 14PCh. 45 - Prob. 15PCh. 45 - Prob. 16PCh. 45 - Prob. 18PCh. 45 - Prob. 19PCh. 45 - Prob. 20PCh. 45 - Prob. 21PCh. 45 - Prob. 22PCh. 45 - Prob. 23PCh. 45 - Prob. 24PCh. 45 - Prob. 25PCh. 45 - Prob. 26PCh. 45 - Prob. 27PCh. 45 - Prob. 28PCh. 45 - Prob. 29PCh. 45 - Prob. 30PCh. 45 - Prob. 31PCh. 45 - Prob. 32PCh. 45 - Prob. 33PCh. 45 - Prob. 34PCh. 45 - Prob. 35PCh. 45 - Prob. 36PCh. 45 - Prob. 37PCh. 45 - Prob. 41PCh. 45 - Prob. 42PCh. 45 - Prob. 43PCh. 45 - Prob. 44PCh. 45 - Prob. 45PCh. 45 - Prob. 46APCh. 45 - Prob. 47APCh. 45 - Prob. 48APCh. 45 - Prob. 49APCh. 45 - Prob. 51APCh. 45 - Prob. 52APCh. 45 - Prob. 53APCh. 45 - Prob. 54APCh. 45 - Prob. 55APCh. 45 - Prob. 56APCh. 45 - Prob. 57APCh. 45 - Prob. 58APCh. 45 - Prob. 59APCh. 45 - Prob. 60APCh. 45 - Prob. 61APCh. 45 - Prob. 62APCh. 45 - Prob. 63APCh. 45 - Prob. 64APCh. 45 - Prob. 65APCh. 45 - Prob. 66APCh. 45 - Prob. 67APCh. 45 - Prob. 68APCh. 45 - Prob. 69APCh. 45 - Prob. 70APCh. 45 - Prob. 71APCh. 45 - Prob. 72APCh. 45 - Prob. 73AP
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- Which of the following quantities represents the reaction energy of a nuclear reaction? (a) (final mass initial mass)/c2 (b) (initial mass final mass)/c2 (c) (final mass initial mass)c2 (d) (initial mass final mass)c2 (e) none of those quantitiesarrow_forwardAnother series of nuclear reactions that can produce energy in the interior of stars is the cycle described below. This cycle is most efficient when the central temperature in a star is above 1.6 × 107 K. Because the temperature at the center of the Sun is only 1.5 × 107 K, the following cycle produces less than 10% of the Sun’s energy. (a) A high-energy proton is absorbed by 12 C. Another nucleus, A , is produced in the reaction, along with a gamma ray. Identify nucleus A decays through positron emission to form nucleus B. (c) Nucleus B absorbs a proton to produce nucleus C and a gamma ray. Identify nucleus C absorbs a proton to produce nucleus D and a gamma ray. Identify nucleus D. (e) Nucleus D decays through positron emission to produce nucleus E. Identify nucleus E. (f) Nucleus E absorbs a proton to produce nucleus F plus an alpha particle. What is nucleus F ? Note: If nucleus F is not 12C—that is, the nucleus you started with—you have made an error and should review the sequence…arrow_forwardGiven that 10,000 neutrons exist at the beginning of a generation. The values for each factor of thesix factor formula are listed in the table below. Calculate:(a) Number of neutrons that exist after fast fission. (b) Number of neutrons that start to slow down in the reactor. (c) Number of neutrons that reach thermal energies. (d) Number of thermal neutrons that are absorbed in the reactor.(e) Number of thermal neutrons absorbed in the fuel.(f) Number of neutrons produced from thermal fissionarrow_forward
- For the fusion reaction shown below, find the amount of energy (Q) released. (Enter your answer in MeV.) H+ C- N +Y MeVarrow_forward33. The core of a thermal reactor consists of a sphere, 50cm in radius, that contains a homogeneous mixture of 25°U and ordinary H,O. This core is surrounded by infinite thick H2O reflector. (a) What is the reflector savings ? (b) What is the critical mass? (c) If the maximum thermal flux is 1 x 1013 neutrons/cm2-sec, at what power is the reactor operating? [ Hint: compute the M2 for core assuming the reactor is bare and of radius 50 cm. Use this value of M to estimate & and then compute new M assuming reactor is bare and of radius 50 + 6. Interate until convergence is obtained.]arrow_forwardIn a nuclear power generating plant, heat from a reactor is used to generate steam for turbines. The rate of the fission reaction determines the amount of heat generated, and this rate is controlled by rods inserted into the radioactive core. The rods regulate the flow of neutrons. If the rods are lowered into the core, the rate of fission will diminish; if the rods are raised, the fission rate will increase. By automatically controlling the position of the rods, the amount of heat generated by the reactor can be regulated. Draw a functional block diagram for the nuclear reactor control system shown in the figure below. Show all blocks and signals.arrow_forward
- a) Calculate the energy in joules released by the fusion of a 1.75 -kg mixture of deuterium and tritium, which produces helium. There are equal numbers of deuterium and tritium nuclei in the mixture. b) If this process takes place continuously over a period of a year, what is the average power output in units of megawatts?arrow_forwardWhich of the following statements about the uranium used in nuclear reactors is or are true? (i) Natural uranium has too little 235U to be used as a fuel. (ii) 238U cannot be used as a fuel because it forms a supercritical mass too easily. (iii) To be used as fuel, uranium must be enriched so that it is more than 50% 235U in composition. (iv) The neutron-induced fission of 235U releases more neutrons per nucleus than fission of 238U.arrow_forwarda) Write down the nuclear reaction for Deuterium-Tritium fusion and answer the following questions:arrow_forward
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