Dalat nuclear reactor: Use low-enriched uranium

On September 15, Da Lat nuclear reactor officially switched to using " low-rich " uranium fuel, confirming Vietnam's goal of atomic energy application for peace. This is also a successful cooperation " three hands ": Vietnam-US-Russia.

A special event took place at the Da Lat Nuclear Reactor: bringing new uranium fuel rods and bringing unused fuel rods. What this means in terms of technology makes international public attention, and what it means to the whole world political life, so that the three countries from the three earths such as Vietnam, the United States and Russia agree handshakes?

Convert uranium: old ' alcohol ' returns to the old ' vase '

In front of the console of Da Lat Nuclear Reactor (Photo: VARANSAC)

Da Lat nuclear reactor, built and put into operation by the United States in 1963. After 20 years of sinking because of the war, 1983 was resurrected with the investment of the Vietnamese government, the support of the country. Russia (the former Soviet Union) on technology and the help of the International Atomic Energy Organization IAEA. Since then, over 20 years, Vietnamese nuclear scientists have safely operated and successfully exploited this nuclear device into peaceful goals in the life and construction of the country.

Over the past 20 years, how many times have you changed the uranium fuel bar on the Da Lat kiln, how many times have the fuel rods swept from the outer zone to the inside of the furnace, replacing the burning rods with new ones. But all of it is the fuel of the generation of former Soviet reactors, with the same level of uranium.

And now, the conversion of fuel rods conducted in Da Lat furnace is different, different in terms of richness, uranium content of fuel .

In contrast to the recently mentioned poor uranium concept, rich uranium is the fuel used in most nuclear reactors, including the Dalat kiln. However, rich uranium is also divided into two types: low-rich uranium and high-enriched uranium.

The uranium fuel, produced in Russia, has been used since the 1980s until recent days at the Da Lat kiln containing U235 content of 36%, known as High-enriched uranium (HEU). As for the fuel that has just arrived in Da Lat, it was put into the kiln and exchanged with some used old bars, containing U235 content of nearly 20%, called Low-enriched uranium (LEU). .

Looking back over the past 40 years of Vietnam's first nuclear reactor, it is interesting to see. The initial fuel rods of the Da Lat furnace were also "low-rich" uranium fuel (LEU) with a wealth of about 18% shipped from the US, brought into the heart of the furnace from 1963 and to 1975, the US took home country. The reactor, of course, is the US TRIGA-Mark 2 furnace.

After more than 30 years, the LEU fuel is now placed in this furnace, replacing the active HEU fuel rods. Is it a transposition, the old ' wine ' eventually returns to the old ' vase '.

" Handshake " does not disseminate nuclear weapons

Worldwide there are 160 research reactors such as Da Lat furnace. Most are Russia (62), followed by the United States (54), Japan (18), France (15), Germany (14) and China (13). Many small or developing countries also have, such as Bangladesh, Algeria, Colombia, Ghana, Jamaica, Libya, Thailand and Vietnam.

Da Lat nuclear reactor research reactor (Photo: Nuclear Research Institute)

The fuel richness of the above-mentioned research facilities is also very diverse. Many kilns have U235 richness to 80-90%, only a few use LEU fuel with 20% richness.

High-fuel fuels (HEU), theoretically, may be at great risk of being mined to process fuel for nuclear weapons. Many countries, first of all the United States, have been concerned for many years.

From the 1980s of the last century, a UN-sponsored international project proposed reducing uranium fuel richness in research reactors to concentrations below 20%. And this conversion was carried out within the framework of RERTR programs (Program to reduce nuclear fuel richness for research reactors and experimental reactors) of Russia and the United States.

Although the capacity of Lo Da Lat (500 kilowat), lower than 1000 kilowatts, is also the object of interest in the general trend that many countries have been implementing.

In March of this year, 2007, the National Nuclear Security Agency (NNSA) of the US Department of Energy signed a written agreement with the Vietnam Atomic Energy Institute (VAEC) under the Ministry of Science and Technology of Vietnam. in Washington, where the Vietnamese Dalat reactor will be converted from a 36% high enriched uranium fuel (HEU) to low enriched uranium fuel below 20% (LEU). .

On the other hand, between JSC TVEL (Russian Federation), Vietnam Atomic Energy Institute and Service Center (under NNSA, US Department of Energy) have signed contracts on manufacturing and supplying fuel with a degree Low uranium enrichment for Dalat Nuclear Reactor. Thus, the new LEU fuel supplied to Lo Da Lat was not produced in the United States, but was ordered by the United States for Russian TVEL in Novosibirsk. The company also supplied LEU fuel for the Czech Republic's VR-1 reactor in Prague and the reactor at Libya's Tajoura Nuclear Research Center recently.

At the same time, it also signed a contract between the International Atomic Energy Agency (IAEA), " SOSNY " Research and Development Company (Russian Federation) and the Vietnam Atomic Energy Commission on the introduction of fuel rods. Unused high levels of uranium at the Russian-supplied Da Lat Nuclear Reactor previously returned to the Russian Federation.

These contracts are the steps to complete the commitments made in the Vietnam-US Joint Statement announced during President Bush's visit to Vietnam in November 2006.

With the careful and careful preparation mentioned above, finally, the process of receiving new LEU fuel rods, and delivering unused fuel HEU bars to Russia has been carried out smoothly in the Reactor. Da Lat nuclear, in the middle of September 2007. This is a memorable time not only in the history of a reactor but also in the relationship between the three countries that have special relationships in the history of world politics.

With the above mentioned event, Vietnam has affirmed its goal of using nuclear energy for peaceful purposes, taking actions in the international commitment of non-proliferation of nuclear weapons, working closely with Mechanical International Atomic Energy Agency IAEA and cooperated with Russian and American nuclear powers in the era-shaking handshake.

Low enriched uranium, high richness

Uranium metal is composed of two major isotopes, U-238 and U-235.In particular, U-238 accounted for 99.3% of the overwhelming amount.The U-235 isotope is too poor, accounting for only 0.7% (3 thousand).Rare and precious U-235 because only fission occurs with U-235.

In the fission reaction, under the action of neutrons, the U -235 nucleus is split into two pieces, emitting a large energy of 200 MeV (200 million electron volts), and releasing 2-3 new neutrons.It is these neutrons that form the chain reaction that is necessary to sustain the operation of nuclear reactors or create an explosion of nuclear bombs.Therefore, the method of raising U235 content in uranium material, called the uranium enrichment method (or technique), plays a very important role in nuclear technology.These are centrifugal methods, gas diffusers ., can raise U235 content from 0.72% (in nature) up to 40% (used in reactors), or higher than 90% (used in atom bomb).

It is these refined uranium products called rich uranium.Thus, depending on the level of isotope content U235, people classified into: poor uranium (U235 content less than 0.72%), natural uranium (U235 content of 0.72%) and rich uranium (function The amount of U235 is greater than 0.72%, from a few% to over 90%).In rich uranium, it is divided into: Low-enriched uranium (LEU) and High-enriched uranium HEU.

Model of nuclear fission reaction U235
(Source: ffden-2.phys.uaf.edu)

Minh Tran