Environmental Engineering FOURTH EDITION

Chapter 16

Radioactive Waste

This chapter presents a background discussion of the interaction of ionizing radiation

with matter, as well as a discussion of the environmental effects of nuclear generation

of electricity and of radionuclides that are accessible to humans in the environment.

The chapter focuses on radioactive waste as an environmental pollutant, discusses

the impact of ionizing radiation on environmental and public health, and summarizes

engineering options available today for the management and disposal of radioactive

waste.

RADIATION

X-rays were discovered by Wilhelm Roentgen toward the end of the year 1895. Almost
immediately thereafter, Henri Becquerel observed radiation similar to X-rays emanat-
ing from certain uranium salts. In 1898, Marie and Pierre Curie studied radiation from
two uranium ores, pitchblende and chalcolite, and isolated two additional elements
that exhibited radiation similar to that of uranium but considerably stronger. These
two elements were named radium and polonium. The discovery and isolation of these
radioactive elements mark the beginning of the “atomic age.”
The Curies classified the radiation from radium and polonium into three types,
according to the direction of deflection in a magnetic field. These three types of radia-
tion were called alpha (a), beta (B), and gamma (y) radiation. Becquerel’s observation
correlated gamma radiation with Roentgen’s X-rays. In 1905, Ernest Rutherford iden-
tified alpha particles emanating from uranium as ionized helium atoms, and in 1932,
Sir James Chadwick characterized as neutrons the highly penetrating radiation that
results when beryllium is bombarded with alpha particles. Modem physics has sub-
sequently identified other subatomic particles, including positrons, muons, and pions,
but not all of these are of equal concern to the environmental engineer. Management
of radioactive waste requires understanding of the sources and effects of alpha, beta,
gamma, and neutron emissions.

Radioactive Decay

An atom that is radioactive has an unstable nucleus. The nucleus moves to a more stable
condition by emitting an alpha or beta particle or neutron; this emission is frequently

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