The government of India is promoting nuclear energy as a solution to the country’s future energy needs and is embarking on a massive nuclear energy expansion




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3. Is Nuclear Energy Clean?


During President Obama's visit to India in November 2010, he and Prime Minister Manmohan Singh committed themselves to spurring the “development of clean and safe nuclear energy in India.”12

From US to India, politicians and leading intellectuals are repeatedly asserting that nuclear energy is a safe and clean form of energy. They are all blithely lying. They believe that if you lie frequently and with conviction, people will believe you.

Even if nuclear power plants are operating normally, the entire nuclear cycle from uranium mining to nuclear reactors routinely emits huge quantities of extremely toxic radioactive elements into the atmosphere every year. The environmental costs of the deadly radiation emitted by these elements and its impact on human health are simply horrendous. What is infinitely more worse, since these radioactive elements will continue to emit radiation for tens of thousands of years, therefore, its effects will continue to plague the human race not just for the present, but for thousands of generations to come. And if there is a major accident, and nuclear reactors are inherently prone to accidents, the consequences will be cataclysmic! In the words of Dr. Helen Caldicott, the renowned Australian physician turned anti-nuclear activist who has worked tirelessly to expose the threat this technology from hell poses to human survival:

As a physician, I contend that nuclear technology threatens life on our planet with extinction. If present trends continue, the air we breathe, the food we eat, and the water we drink will soon be contaminated with enough radioactive pollutants to pose a potential health hazard far greater than any plague humanity has ever experienced.13

In this chapter, we discuss the radiation emitted during each stage of the nuclear fuel cycle and its consequences for the human race. In the next chapter, we discuss the possibility of a major accident occurring in nuclear reactors and its probable impact, in the light of Chernobyl and the very recent Fukushima nuclear accident.

Part I: What is Radiation?

Radioactive decay: Stable and unstable atoms


Most atoms found in nature are stable, that is, they do not undergo changes on their own. For instance, if we put an atom of aluminium in a bottle, seal it, and open it after a million years, it would still be an atom of aluminium. Aluminium is therefore called a stable atom.

Many stable atoms also have unstable isotopes. An unstable atom is one whose nucleus undergoes some internal change spontaneously. In this change, the nucleus emits radiation in the form of subatomic particles, or a burst of energy, or both. This emission of radiation is called radioactivity, and the nucleus is said to have undergone radioactive decay. In this process, the nucleus changes its composition and may actually become an entirely different nucleus. The process continues till the nucleus achieves stability.

To give an example: most carbon (C-12) atoms are stable, with the nucleus having six protons and six neutrons. Carbon has an unstable isotope, C-14, whose nucleus consists of six protons and eight neutrons. In its attempt to achieve stability, its nucleus gives off a beta particle (an electron). After emitting the beta particle, the C-14 nucleus now consists of seven protons and seven neutrons (one neutron has decayed into an electron and a proton, and the electron has been emitted as a beta particle). But a nucleus consisting of seven protons and seven neutrons is no longer a carbon nucleus, it is the nucleus of a nitrogen atom. By emitting a beta particle, the C-14 atom has changed into a N-14 atom.

Types of Radiation


Radioactive isotopes emit three types of radiation:

  1. Alpha radiation: Alpha particles are composed of two protons and two neutrons. Being heavy (as compared to beta particles), these particles do not travel very far. Therefore, they are not able to penetrate dead cells in the skin to damage the underlying living cells. However, when inhaled into the lungs or ingested into the gastrointestinal tract, they come into contact with living cells and severely damage them. The consequences for human health can be serious, including the possibility of causing cancer. For instance, plutonium is an alpha emitter, and no quantity inhaled has been found to be too small to induce lung cancer in animals.

  2. Beta radiation: This is composed of electrons. How does a nucleus emit an electron? The answer: a neutron breaks up into a proton and an electron, and the latter is emitted. Beta particles are lighter than alpha particles, and so while they travel farther than alpha particles in body tissues, the biological damage caused by them is less—like a bullet compared to a cannon ball. They can penetrate the outer layer of dead skin and damage the underlying living cells. If inhaled or ingested to enter into the blood stream, they can damage tissues and cause cancer. Thus, iodine-131 is a beta emitter. It concentrates heavily in the thyroid gland, increasing the risk of thyroid cancer and other disorders.

  3. Gamma radiation: This is akin to X-rays. It has great penetrating power and can travel large distances. Gamma radiation goes straight through human bodies. As gamma rays pass through the body, they can damage the body cells.

When people are exposed to radiation, it may or may not lead to disease—it depends upon whether the body's cellular repair mechanisms are able to repair the damage or not. But, as we see below, what is definite is that there is no minimum safe dose of radiation.

Units of Radiation


Becquerel and Curie: This unit applies to the strength of the source, that is, the radioactive isotope. In the International System of units (SI), it is measured in becquerel (Bq). One Bq is defined as one disintegration per second. Becquerel is a very small unit. An older, non-SI, and much larger unit of radioactivity is curie (Ci), defined as: 1 curie of radiation = 3.7 × 1010 disintegrations per second.

Rad and Gray: The radiation emitted by a radioactive element is not the same as the radiation absorbed by the body. The difference between the two is like a boxer who hits at his opponent, but he may or may not strike him. The radiation dose absorbed by the body is measured in a unit called rad. In the SI system of units, the unit is gray. A dose of 1 gray means the absorption of 1 joule of radiation energy per kilogram of absorbing material. The conversion factor is: 1 gray = 100 rad.

Rem and Sievert: Even for the same amount of absorbed radiation, different types of radiation have different biological effects. Thus, the same rad of alpha particles when absorbed cause much more damage than beta particles. This difference is measured by a unit called rem. To determine rem, the absorbed dose in rad is multiplied by a quality factor (Q) that is unique to the type of incident radiation. For gamma rays and beta particles, 1 rad of exposure results in 1 rem of dose, while for alpha particles, 1 rad of exposure is equivalent to 20 rems of dose. Another unit for measuring biological impact of absorbed radiation is sievert or Sv: 1 sievert = 100 rem.

Some examples of radiation doses:

Radiation dose

Source

0.1 mSv

X-ray (chest)

0.4 mSv

Mammography

1.5 mSv

X-ray (spine)

2 mSv

CT scan (head)

15 mSv

CT scan (abdomen and pelvis)

Radiation is often measured in dose rates, such as millisievert per hour. Dose rates are important because faster delivery of radiation can have a relatively stronger impact; getting the same dose in 1 hour is usually worse than getting the same dose stretched out over the course of a year. Some important dose rates are:

  • In the US (and several other countries), maximum radiation exposure limit for members of the public is 1 mSv/year.

  • The maximum exposure limit for employees of nuclear facilities in most countries, including India, is 20 mSv/year; this limit is 50 mSv/yr in the US.

Half-life


Each radioactive isotope has a specific half-life. Half-life of an isotope is the amount of time it takes for the half the number of atoms of that isotope to decay. For example, radioactive iodine-131 has a half-life of eight days. This means that in eight days it loses half its radioactive energy, in another eight days it decays again to one quarter of the original radiation, ad infinitum. The amount of time taken by a radioactive isotope to decay to a harmless level can be obtained by a simple thumb rule: multiply the half-life by 20. (There is of course no unanimity on this; many experts say that radiation becomes harmless in 10 half-lives.) Thus, in the case of iodine-131, its radioactive life is 8 x 20 = 160 days. Some isotopes created during the fission reaction in a nuclear reactor have very short half-lives (less than a second), and some extremely long (millions of years).
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