140305 - How to build a fission bomb

Nuclear fission bombs are based on Uranium-235 or Plutonium-239. At least one test has also been tested with Uranium-233. It is also possible to build nuclear bombs with Neptunium or Americium. It is a pretty simply comstruction. But the types are different depending on using U-235 or Pu-239. A U-235 is the easiest to build.

Lets start with the U-235 device. You will need about 60 kg of almost pure U-235 (over 90 %). Natural Uranium consists of only about 0,72 % U-235, the rests is U-238, wich not is fissionable.

Here is a drawing of the Uranium bomb "Little Boy" which was dropped on Hiroshima.

A Plutonium bomb is more complicated, it is built on a implosion of a Plutonium-sphere. But you will only be need of about 6 kg of Plutonium. Plutonium does not exist in the natur (exept for small traces), so it must be made in a reactor. The Plutonium is often alloyed with about 3 % Gallium.

Here is a drawing of the Plutonium bomb "Fat Man" which was dropped on Nagasaki.

The hard thing with this device is to get the explosive lenses to detonate exactly at the same time.

In both cases, the device is build to smash together a fissile material into a critical mass, with help of conventional explosives. Little Boy had a yield of about 15 kt, and Fat Man about 21 kt.

110514 - Introduction

My project is to build a working nuclear reactor. Not to gain electricity, just for fun and to see if it's possible to split atoms at home. I would be a breeder reactor, and my primary goals is to carry out two main reactions, which is;

Th-232 + n →Th-233 (T½ = 22,3 min) → β → Pa-233 (T½ = 27 days) → β → U-233
U-233 has a T½ of 1 590 000 years, and is fissionable.

And the second reaction;

U-238 + n →U-239 (T½ = 23,45 min) → β → Np-239 (T½ = 2,356 days) → β → Pu-239
Pu-239 has a T½ of 24 110 years, and is fissionable.


Some basic nuclear-physics

Th = Thorium, a naturally occuring element, atomic-number 90, and it is a weak α-emitter (the Th-232).
Pa = Protactinium, atomic-number 91.
U = Uranium, is also a naturally occuring element. Atomic-number 92. The most common isotope is U-238, wich is a weak α-emitter.
Np = Neptunium, atomic-number 93
Pu = Plutonium, atomic-number 94, the isotope Pu-239 is fissionable, and extremly poisonous.

With fissionable isotopes, you can also build nuclear weapons. But that needs huge amounts of the material, 6 kg of Pu-239 or 50 kg of U-235. In this experiment, we only will be able to produce less than a gram.

T½ stands for half-life. Every radioactive isotope has a half-life, and with thats means the time it takes for half of the atoms in the piece to decomposition to another isotope, with emitting their radiation. It can be between nanoseconds to billions of years.

Many of the substances we are going to handle is radioactive. And you should be careful with radiation. The radiation-types are;

α-radiation, contanis of 2 protons and 2 neutrons, it reaches some centimeters in air, and does not penetrate the skin. But it is very dangerous to ingest or inhale it! An α-decaying atom loses 2 in atomic-number, and 4 in total mass.

β-radiation endures of electrons and reaches some meters in air or is stopped by a glass or plate. A β-dacaying atom raises the atomic-number with 1, but the total mass is unchanged (a neutron is transforming into a proton).

γ-radiation is high-frequency electromagnetic radiation (photons), it reaches several meters but can be stopped by a thick concrete wall. γ-radiation occurs more or less in every decays.