Humanity has always been in search of new sources of energy that can solve many problems. However, they are not always safe. So, in particular, although nuclear reactors that are widely used today, although they are capable of generating just a colossal amount of the electric energy so needed by everyone, still carry a mortal danger. But, in addition to using nuclear energy for peaceful purposes, some countries of our planet have learned to use it in the military, especially to create nuclear warheads. This article will discuss the basis of such destructive weapons, the name of which is weapons-grade plutonium.
Quick reference
This compact metal form contains at least 93.5% of the 239Pu isotope. Weapon-grade plutonium was named so that it could be distinguished from the "reactor counterpart". In principle, plutonium is always formed in absolutely any nuclear reactor, which, in turn, operates on low enriched or natural uranium containing, for the most part, the 238U isotope.
Military application
Weapon-grade plutonium 239Pu is the basis of nuclear weapons. At the same time, the use of isotopes with mass numbers of 240 and 242 is irrelevant, since they create a very high neutron background, which ultimately complicates the creation and construction of highly efficient nuclear ammunition. In addition, plutonium isotopes 240Pu and 241Pu have a significantly shorter half-life compared to 239Pu, so plutonium parts become very hot. It is in connection with this that engineers are forced to add elements to remove excess heat in nuclear munitions. By the way, 239Pu in its pure form is warmer than the human body. One cannot ignore the fact that the products of the decay process of heavy isotopes expose the crystal lattice of metal to harmful changes, and this quite naturally changes the configuration of plutonium parts, which, in the end, can cause a complete failure of a nuclear explosive device.
By and large, all these difficulties can be overcome. And in practice, explosive devices based on precisely “reactor” plutonium have already been tested many times. But it should be understood that in nuclear munitions far from the last position is taken by their compactness, low dead weight, durability and reliability. In this regard, they exclusively use weapons-grade plutonium.
Design features of production reactors
Almost all of the plutonium in Russia was produced in reactors equipped with a graphite moderator. Each of the reactors was erected around cylindrically assembled blocks of graphite.
The assembled graphite blocks have special slots between them to ensure continuous circulation of the cooler, which is used as nitrogen. The assembled design also has vertically arranged channels created for the passage of water cooling and fuel through them. The assembly itself relies heavily on a structure with openings under the channels used to dispatch already irradiated fuel. Moreover, each of the channels is located in a thin-walled pipe cast from lightweight and extra-strong aluminum alloy. Most of the described channels have 70 fuel rods. Cooling water flows directly around the fuel rods, removing excess heat from them.
Increased production reactor power
Initially, the first Mayak reactor operated with a capacity of 100 thermal MW. However, Igor Kurchatov , the head of the Soviet program for the development of nuclear weapons, made a proposal that the reactor should operate with a capacity of 170-190 MW in winter and 140-150 MW in summer. This approach allowed the reactor to produce nearly 140 grams of precious plutonium per day.
In 1952, full-scale research work was carried out with the aim of increasing the production capacity of functioning reactors by such methods:
- By increasing the flow of water used for cooling and flowing through the active zones of a nuclear installation.
- By increasing the resistance to the phenomenon of corrosion occurring near the liner of the channels.
- A decrease in the rate of oxidation of graphite.
- By increasing the temperature inside the fuel cells.
As a result, the capacity of the circulating water increased significantly after the gap between the fuel and the channel walls was increased. They also managed to get rid of corrosion. To do this, they chose the most suitable aluminum alloys and began to actively add sodium dichromate, which ultimately increased the softness of the cooling water (the pH became about 6.0-6.2). Oxidation of graphite ceased to be an urgent problem after nitrogen was used to cool it (before that, air was used exclusively).
At the end of the 1950s, the innovations were fully implemented in practice, which made it possible to reduce the extremely unnecessary swelling of uranium caused by radiation, significantly reduce the thermal hardening of uranium rods, improve the shell resistance and increase the quality control of production.
Production at the Mayak
Chelyabinsk-65 is one of the very secret plants where weapons-grade plutonium was created. The enterprise had several reactors, each of which we will get to know more closely.
Reactor A
The installation was designed and created under the guidance of the legendary N. A. Dollezhal. She worked with a capacity of 100 MW. The reactor had 1,149 vertically arranged control and fuel channels in a graphite block. The total mass of the structure was about 1050 tons. Almost all channels (except 25) were loaded with uranium, the total mass of which was 120-130 tons. 17 channels were used for control rods, and 8 - for experiments. The maximum design heat release of the fuel cell was 3.45 kW. At first, the reactor produced about 100 grams of plutonium per day. Metal plutonium was first produced on April 16, 1949.
Technological disadvantages
Almost immediately, quite serious problems were identified, which consisted in the corrosion of aluminum liners and the coating of fuel cells. Uranium rods also swelled and damaged, and cooling water flowed directly into the core of the reactor. After each leak, the reactor had to be stopped for up to 10 hours in order to dry graphite with air. In January 1949, the liners in the canals were replaced. After that, the installation started on March 26, 1949.
Weapon-grade plutonium, the production of which at reactor A was accompanied by all sorts of difficulties, was produced in the period 1950-1954 with an average unit power of 180 MW. The subsequent operation of the reactor began to be accompanied by its more intensive use, which quite naturally led to more frequent shutdowns (up to 165 times a month). As a result, in October 1963, the reactor was stopped and resumed operation only in the spring of 1964. He completely completed his campaign in 1987 and produced 4.6 tons of plutonium over the entire period of many years of operation.
AB reactors
At the Chelyabinsk-65 enterprise, it was decided to build three AB reactors in the autumn of 1948. Their production capacity was 200-250 grams of plutonium per day. The chief designer of the project was A. Savin. Each reactor totaled 1996 channels, 65 of them were control. A technical novelty was used in the installations - each channel was equipped with a special coolant leak detector. Such a move allowed changing the liners without stopping the operation of the reactor itself.
The first year of operation of the reactors showed that they produced about 260 grams of plutonium per day. However, already from the second year of operation, the capacity was gradually increased, and already in 1963 its indicator amounted to 600 MW. After the second overhaul, the problem with liners was completely resolved, and the capacity was already 1,200 MW with an annual production of 270 kilograms of plutonium. These figures remained until the reactors were completely shut down.
AI-IR reactor
The Chelyabinsk enterprise used this installation from December 22, 1951 to May 25, 1987. In addition to uranium, the reactor also produced cobalt-60 and polonium-210. Initially, tritium was produced at the facility, but later plutonium was also produced.
The weapons-grade plutonium processing plant also had heavy water reactors and a single light-water reactor (its name is Ruslan).
Siberian giant
"Tomsk-7" - this is the name the plant had, which housed five reactors to create plutonium. Each of the units used graphite to slow down neutrons and ordinary water to ensure proper cooling.
The I-1 reactor worked with a cooling system in which water passed once. However, the remaining four units were equipped with closed primary circuits equipped with heat exchangers. Such a design made it possible to additionally generate steam, which in turn helped in the production of electricity and heating of various residential premises.
Tomsk-7 also had a reactor called EI-2, which, in turn, had a dual purpose: it produced plutonium and generated 100 MW of electric power as well as 200 MW of thermal energy from the generated steam.
Important information
According to scientists, the half-life of weapons-grade plutonium is about 24,360 years. A huge number! In this regard, the question becomes particularly acute: "How to deal with the waste products of this element?" The most optimal option is the construction of special enterprises for the subsequent processing of weapons-grade plutonium. This is explained by the fact that in this case the element can no longer be used for military purposes and will be controlled by man. This is how weapons-grade plutonium is disposed of in Russia, but the United States has taken a different path, thereby violating its international obligations.
Thus, the US government proposes to destroy highly enriched nuclear fuel not in an industrial way, but by diluting plutonium and storing it in special containers at a depth of 500 meters. It goes without saying that in this case, the material can easily be removed at any time from the ground and again put into military use. According to Russian President Vladimir Putin, initially the countries agreed to destroy plutonium not by this method, but to dispose of it at industrial facilities.
Special attention is paid to the cost of weapons-grade plutonium. According to experts, tens of tons of this element may well cost several billion US dollars. And some experts at all estimated 500 tons of weapons-grade plutonium as much as $ 8 trillion. The amount is really impressive. To make it clearer how much money this is, let's say that in the last ten years of the 20th century, Russia's average annual GDP was $ 400 billion. That is, in fact, the real price of weapons-grade plutonium was equal to twenty annual GDP of the Russian Federation.