LESSONS FROM HIROSHIMA

June 16, 2021

LESSONS FROM HIROSHIMA

Nikunja Bihari Sahu

Before the US Bomber Enola Gay detonated the world’s first nuclear device that flattened the Japanese city of Hiroshima on 6^th August, 1945, little did humanity know about the lethality of nuclear warfare. We are convinced again of the awesome power of nuclear energy when a second device was unleashed over Nagasaki three days later. The devastations caused by these twin blasts were immense and unparalleled in history as evident from the fact that more than 2,00,000 people, mostly civilians, were killed within the first two months of the explosion with half of the casualties resulting almost instantly.

WORLD ON THE BRINK OF NUCLEAR WAR

Since then, the cloud of a nuclear war loomed over the world all the time reaching its peak during the Cold War period. The world probably came closest to the brink of a nuclear war on October 27, 1962 when a Soviet submarine B-59 was about to fire a nuclear torpedo at the US Navy during the Cuban naval blockade which was averted at the last minute by the wise decision of a Soviet officer named Vasili Akhipov aboard the ship.

LITTLE BOY AND FAT MAN

While the bomb dropped over Hiroshima was code-named as the Little Boy, the bomb detonated over Nagasaki was called Fat man. The Little Boy measures 10 ft in length and 28 inches in diameter weighing about 4400 kg. It contained 64 kg of enriched Uranium (U-235) as the fissile material with a blast yield of 15 kilotons of TNT.

Similarly, the Fat Man measures 128 inches in length and 60 inches in diameter weighing about 4670 kg. It was an implosion type nuclear weapon with a solid plutonium core weighing about 6.4 kg. Its blast yield was equivalent to 21 kilotons of TNT.

HOW DOES A NUCLEAR BOMB WORK

Uranium and Plutonium are the two common fuels used for making nuclear weapons with the fissile isotopes being U-235 and Pu-239 respectively. While U-235 isotope is a naturally occurring substance with an abundance of only 1% of the total Uranium reserve on Earth, Plutonium, on the other hand, is not at all found in nature. Hence, the biggest challenge in making a nuclear weapon is producing enough quantity of these isotopes from their elements available in nature.

A Uranium bomb requires converting refined Uranium into gaseous form and then spinning it at very high speed in Centrifuges to separate fissile U-235 isotopes. This has to be done repeatedly through cascades of centrifuges to ensure a very high order of enrichment. While Uranium, used in nuclear power reactors for generating electricity, is required to be enriched up to only 3% - 4%, weapon grade Uranium is more than 90% enriched to ensure a very high rate of fission. However, building enough number of centrifuges and getting them to spin very fast in unison to isolate enough quantity of weapon grade Uranium is the greatest technical challenge in this process.

On the other hand, although Plutonium (Pu-239) is not found naturally, it is produced in appreciable quantities by extracting it from irradiated Uranium fuel through a reactor. Because it is more fissile, less Plutonium fuel is required for making a weapon.

Once enough fissile material is mobilized, the atoms are then forced close enough to one another to trigger the Chain reaction. In a Chain reaction, the free neutrons released by splitting a nucleus are utilized for causing further splitting of nuclei thus multiplying the splitting process at a very brisk rate. This ensures release of vast amount of energy within a very short period of time. There are basically two types of bomb designs to achieve the Chain reaction.

The simplest design is the Gun type device which involves firing of one chunk of fissile material into another at a very high speed using conventional explosives. The Little Boy weapon dropped on Hiroshima was primarily a Gun type device with about 64 kg of highly enriched Uranium fuel.

A more sophisticated design, which requires less fissile material, is the Implosion type device in which a core of Plutonium is surrounded by an array of explosives assembled to go off simultaneously to compress the core strong enough to ensure triggering of the Chain Reaction. The Fat Man weapon dropped on Nagasaki was an implosion type device with nearly 6 kg of Plutonium fuel.

NUCLEAR PROLIFERATION

In the mean time, the nuclear nation states, instead of cutting down their arsenals, have rapidly stepped up their production in order to gain supremacy. As of now, around 15,000 nuclear warheads exist with 9 countries of the world (i.e. Russia, United States, France, UK, China, Pakistan, India, North Korea and Israel) with more than 90% of the world's nukes owned by just two countries: the United States and Russia. Most of these weapons are many times powerful than the bombs dropped over Japan. Coming to our Indian scenario, we are surrounded by two nuclear neighbours (i.e. China and Pakistan), and interestingly, a small country like Pakistan has more number of nuclear weapons than India.

DAMAGE AND DEVASTATIONS

The heart of a nuclear explosion instantly reaches a temperature of several million degrees similar to the temperature inside the Sun’s core vaporizing all human tissues leaving their shadows only to be captured in photographs. Most casualties, about 90%, occur just aftermath the explosion as people are killed by the heat and blast effects and by violent hurricane like winds. Survivors will be affected within a few days by radioactive fall-out leading to biological complications like hair loss, bleeding from the mouth and gums, internal bleeding and hemorrhagic diarrhea, gangrenous ulcers, vomiting, fever, delirium and terminal coma for which there is no effective treatment. In the long term effect, cancer is induced by radiation exposure. Besides this, our fragile environment will also be greatly affected with the destruction of the Ozone layer and the onset of nuclear winter. It is estimated that it would take only 100 super bombs to wipe out the entire human population from the face of our planet. As Einstein has rightly stated, “I do not know with what weapons World War III will be fought, but World War IV will be fought with sticks and stones.”

NUCLEAR FREE WORLD

Some of the world’s leaders are tempted to advocate the possession of nuclear weapons owing to their effective role as deterrents. However, most nuclear powers like the USA and Russia are responsible nations and have robust mechanism in place to avoid a nuclear war. The prime concern today is the chance of passing of nuclear weapons to wrong hands like international terrorist groups and oppressive regimes that do not care for the dignity of human life. Although the leaders of some nuclear armed nations have expressed their desire for arms control and nuclear disarmament through various treaties like NPT, CTBT our destination for a completely nuclear free world has not been reached.

LESSONS FROM HIROSHIMA

In this background, the lesson learned from Hiroshima is loud and clear. The only guarantee against the spread and use of nuclear weapons is to completely eliminate them without delay before they really cause any catastrophe. However, our quest for harnessing nuclear power for peaceful purposes, like generation of electricity through nuclear reactors, should continue as we should not be deprived ever to exploit the vast source of nature’s energy locked inside the nuclei of atoms.