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Chapter 21: Problem 84

In 1997 a scientist at a nuclear research center in Russia placed a thin shell of copper on a sphere of highly enriched uranium-235. Suddenly, there was a huge burst of radiation, which turned the air blue. Three days later, the scientist died of radiation damage. Explain what caused the accident. (Hint: Copper is an effective metal for reflecting neutrons.)

Short Answer

Expert verified
The cause of the accident was a criticality incident, a uncontrolled nuclear chain reaction, triggered by placing copper, a reflector of neutrons, on a sphere of uranium-235, a fissionable material. This led to the reflection of neutrons back into the uranium, inducing more fission and producing a huge, lethal burst of radiation.

Step by step solution

01

Understanding the Material Involved

First, it's crucial to understand the materials involved. Uranium-235 is a radioactive isotope used in nuclear reactors and weapons. When a slow-moving neutron hits it, it can split, releasing energy and additional neutrons which can then cause other uranium-235 atoms to split, creating a chain reaction. Copper, on the other hand, is a reflector of neutrons. When a neutron hits a copper atom, it can bounce back, similar to light reflecting from a mirror.
02

Analyzing the Incident

By placing a shell of copper around a sphere of uranium-235, the neutron-firing uranium atoms were encased. As a result, many neutrons that would have escaped into the surrounding environment instead reflected back into the uranium sphere.
03

The Cause of the Accident

These reflected neutrons caused more uranium-235 atoms to split, increasing the rate of fission, and causing a rapid chain reaction. This reaction released a large amount of radiation energy, which manifested as a burst of radiation, turning the air blue. This is known as a criticality incident. The scientist was exposed to this high-intensity, short-term radiation which ultimately led to lethal radiation damage.

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Most popular questions from this chapter

Write balanced nuclear equations for these reactions and identify \(\mathrm{X}:\) (a) \(\mathrm{X}(\mathrm{p}, \alpha){ }_{6}^{12} \mathrm{C},\) (b) \({ }_{13}^{27} \mathrm{Al}(\mathrm{d}, \alpha) \mathrm{X}\) (c) \({ }_{25}^{55} \mathrm{Mn}(\mathrm{n}, \gamma) \mathrm{X}\)

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Both barium (Ba) and radium (Ra) are members of Group \(2 \mathrm{~A}\) and are expected to exhibit similar chemical properties. However, \(\mathrm{Ra}\) is not found in barium ores. Instead, it is found in uranium ores. Explain.

(a) Calculate the energy released when a \({ }^{238} \mathrm{U}\) isotope decays to \({ }^{234} \mathrm{Th} .\) The atomic masses are given by: \(^{238} \mathrm{U}: 238.0508 \mathrm{amu} ;{ }^{234} \mathrm{Th}: 234.0436 \mathrm{amu} ;{ }^{4} \mathrm{He}\) 4.0026 amu. (b) The energy released in (a) is transformed into the kinetic energy of the recoiling \({ }^{234} \mathrm{Th}\) nucleus and the \(\alpha\) particle. Which of the two will move away faster? Explain.

Define nuclear fission, nuclear chain reaction, and critical mass.
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