Commander revives 'American shell, Russian guts' nuclear reactor

From the nuclear reactor built by the US and abandoned in 1975, Professor Pham Duy Hien and his colleagues successfully restarted the Dalat nuclear reactor using a Soviet technology core.

Nearly 40 years ago, Professor Pham Duy Hien (88 years old), former Director of the Dalat Nuclear Research Institute, was directly assigned by the late General Vo Nguyen Giap to preside over the project of restoring the Dalat Nuclear Reactor, with the help of the Soviet Union. This is a nuclear reactor built and operated by the US since 1961. In March 1975, before Dalat was liberated, the Americans withdrew all the fuel rods - the "heart" of the reactor - and brought them back to the country, making the reactor unable to operate.

From an abandoned project, Professor Hien and a team of Soviet officials and experts restored the reactor, successfully put it into operation, and increased its capacity from 250 to 500 kW - laying the foundation for the development of Vietnamese nuclear science .

Prof. Dr. Pham Duy Hien, former Director of the Dalat Nuclear Research Institute, shared with VnExpress about the process of restoring the reactor. Photo: Phung Tien

"American oven, Russian intestines"

- Immediately after the country's reunification, Vietnam decided to restore the Dalat Nuclear Reactor. How did this task begin, sir?

- In October 1975, I was sent by my agency to Da Lat to study and examine the current status of the nuclear reactor built by the US. At that time, I was the Head of the Nuclear Research Department - Institute of Physics, Vietnam Academy of Science (now Vietnam Academy of Science and Technology), and had defended my doctoral thesis on nuclear at Lomonosov University.

From Hanoi, I flew by military plane to Ho Chi Minh City, then was escorted by military vehicles to Da Lat. At that time, the reactionary Fulro organization was still causing trouble in the Central Highlands, so there were soldiers carrying guns to protect it. The reactor was being managed by a military unit. After several days of observing and researching, I returned to Hanoi and submitted a report on the current situation, as well as a proposal for restoring the reactor. At the end of 1975, the Soviet Union also agreed to support Vietnam in restoring the Da Lat reactor.

The responsibility of leading this project was officially assigned to me in a meeting at General Vo Nguyen Giap's house in April 1976, even though I was not a Party member. At that time, he was concurrently holding the positions of Minister of National Defense and Deputy Prime Minister , in charge of science and technology.

In the meeting with many other leaders and generals present, the General directly mentioned me: "The most important and urgent matter now is to restore the Da Lat reactor. Mr. Tu (Professor Nguyen Dinh Tu, the first Director of the Vietnam Atomic Energy Institute) is busy with the Ministry of Universities in Hanoi, so I and my colleagues in the Government suggested that Mr. Hien take care of this matter first."

Accepting the task, I felt it was a heavy responsibility, and also full of newness and challenges.

On April 26, 1976, the Government decided to establish the Nuclear Research Institute (Da Lat), under the State Committee for Science and Technology (now the Ministry of Science and Technology).

Nuclear human resources at that time in Vietnam was not difficult. Right under my command at that time, there was a team of leading nuclear experts including 10 PhDs trained in countries such as France and the Soviet Union. We also invited some former employees who had worked at the previous reactor to join.

The Da Lat nuclear reactor (Lam Dong) first operated in 1963, has a closed circular shape, designed by architect Ngo Viet Thu. Photo: Hoang Truong

The first time I saw the kiln lying alone on a hill in the middle of Da Lat, I was very impressed with its beauty. Compared to kilns in many countries I have been to, Da Lat kiln is relatively small, but has a unique circular architecture, not seen anywhere else, designed by architect Ngo Viet Thu.

Except for the core that the US removed, the structure of the reactor remained almost the same. Despite the loss of fuel, the radiation level at the bottom of the reactor was still quite high, so the reactor vessel still contained purified water to block radiation and keep the materials at the bottom from corroding.

The furniture inside the furnace is neatly stored, reports and records of the previous construction process are carefully kept in cabinets, becoming a useful source of documents for us.

Professor Pham Duy Hien (left) discussed with the head of the Soviet expert delegation about the project implementation plan. Photo: Institute of Nuclear Research

- The furnace was designed by the US, but restored with the help of Soviet experts. How to resolve the technological differences between the two countries?

- This is the first time in the world that there is a hybrid reactor "American shell - Russian core". Reactor technology between the two countries is very different, from the operating principle to the physical nature of the fuel - the heart of the reactor.

The reactor built by the US has a homogeneous structure, the uranium fuel is mixed evenly with the neutron moderator to form U-ZrH crystals, thus having high intrinsic safety. Meanwhile, the Soviet Union applied a heterogeneous structure, the neutron moderator is interspersed between the fuel layers, the intrinsic safety is lower, but the power is easily increased. Therefore, the Soviet Union had to equip other, more complex auxiliary technical systems to ensure safety.

In the end, we agreed on a new 500 kW reactor - double the capacity of the US operation (250 kW).

- Did the furnace start-up process proceed as originally planned?

- The restoration phase of the reactor took place from 1981 to 1984, before which there was a survey period. Soviet experts expected to start the physics before the anniversary of the October Revolution, which was November 7, 1983. However, before loading fuel into the new reactor, I flew in from Hanoi when Da Lat had just experienced a storm. Trees and electric poles had fallen down, the work on the reactor was in disarray, and the water at the bottom of the reactor was very dirty.

I decided to stop for a few days to clean the reactor, the Soviet experts were not happy, but still accepted. After cleaning, we loaded fuel to start the physics, bringing the reactor to the critical state, that is, there was a chain reaction, but the power was only zero.

After completing the physical start-up process, the Soviet delegation went on vacation to Nha Trang, planning to turn on the power when they returned, increasing the reactor's capacity to 500 kW. However, I was still worried about the dirty water of the reactor, so before turning on the power, I asked to remove a fuel rod to check. Surprisingly, it was gray instead of the original bright color.

Staff of the Dalat Nuclear Research Institute and Soviet experts in the control room preparing for the reactor start-up process. Photo: Nuclear Research Institute

The plan to increase the capacity had to be postponed, the head of the Soviet expert team had to bring the gray fuel rods and reactor water bottles back to Moscow for inspection. I also flew to Hanoi to consult with other experts. The remaining members of the Soviet team planned to return home for the New Year when the capacity increase was successful, but because of that trouble, they agreed to stay in Da Lat.

The reactor was only officially started in March 1984 when the Soviet side replied that the graying of the fuel rods did not affect the operation of the reactor. This was the first time they encountered this phenomenon, so they did not give a specific cause. We speculated that it could be due to an electrochemical phenomenon because the reactor contained both old metal from the previous reactor and new metal.

The furnace's inauguration was delayed by three months to resolve this issue, but safety during operation was ensured.

Chernobyl fears in Vietnam

- As one of the key projects of Vietnam at that time, how did the restoration process of the Dalat Nuclear Reactor receive attention from the leaders?

- Thanks to the special attention of senior leaders, we received a lot of support during our work.

The first phase was the time for surveying and reporting, from which we had a basis for discussion with Soviet experts so that they could come up with calculation and design plans. I remember that in the years 1976-1980, life was very difficult, everyone had to measure rice with ration stamps. The brothers from the North who went to Da Lat to survey had to eat more bo bo instead of rice.

I "had to risk" going directly to General Vo Nguyen Giap, asking for instructions for Lam Dong to provide rice for the delegation. The General smiled humorously and said: "Why do people say that they love their husbands and cook bobo porridge?" Having said that, he immediately signed the rice supply paper and sent me to the Lam Dong Province Food Department.

The General was very close to the lives of the brothers, visiting many times. One time, when the furnace was already in operation, he asked me to take him to the dining room. At that time, it was evening, the brothers had finished eating and gone out, only a female employee from the Project Management Board remained. Looking at the plate of rice with a few vegetables and a few pieces of meat and fish, he said: "Eating like this, where will we get the strength to work on the furnace?"

Or like Prime Minister Pham Van Dong, after visiting the Dalat Nuclear Reactor, asked Phan Rang to provide fresh fish every week for the brothers.

We also received many special privileges such as two-day weekends off, increased radiation allowance, and weekly milk supply from the farm in Lam Dong. That is why there was a joke at that time: "In Da Lat, no one is richer than the Nuclear Institute."

General Vo Nguyen Giap visits the Institute of Nuclear Research, March 1984. Photo: Institute of Nuclear Research

- What results did the research and production activities of the Dalat Nuclear Reactor bring to Vietnam at that time?

- In addition to preparing radioactive pharmaceuticals for hospitals, we also develop irradiation technology, applying it to many aspects of life such as sterilizing plastic medical instruments, vulcanizing latex into rubber by gamma irradiation.

Another research that has created a big buzz is the use of radioactive tracers to mark the transport of sediment in Hai Phong port channel. At that time, the waterway for ships entering and leaving Nam Trieu port, Hai Phong port was always silted up, requiring regular and costly dredging. Many solutions have been proposed but have not been effective. We propose to use radioactive tracers to monitor the transport of sand and mud.

To do that, the research team went to Hai Phong port to collect bottom mud, analyzed it, and created an artificial sand made of scandium with the same grain size as natural sand in Hai Phong. This sand was then put into a reactor to activate it into radioactive isotopes.

We took it to Hai Phong port, pumped radioactive sand to the bottom of the channel, and used a ship equipped with a positioning device to determine the direction and speed of sand movement. Thanks to that, the research team knew the law of sediment transport over time and redrawn a map of its movement.

Later, Japanese experts also used the research results to help design new waterways for Hai Phong port.

- The Dalat nuclear reactor had been operating for two years when the Chernobyl nuclear power disaster occurred (in 1986). How did this event affect the reactor's activities and research afterward?

- After the Chernobyl nuclear disaster, the atmosphere of panic and anxiety prevailed. Even when implementing the project of marking the transportation of radioactive sediments in Hai Phong port, the city leaders initially did not agree to let us release radioactive materials into the sea, because they were worried that "the consequences would be no different from Chernobyl". It was not until 10 days later that they agreed to grant the license.

The old furnace and some of the furnace bottom components were corroded in many places, leaving dark brown stains that could be seen through the water layer more than 6 meters high. Even if the furnace was operating safely, I always wanted to take every opportunity to find out if the furnace bottom corrosion was continuing to progress.

In 1987, a group of foreign experts came to Da Lat under a technical cooperation project sponsored by the International Atomic Energy Agency. They saw corrosion at the bottom of the reactor and concluded that the Da Lat reactor would be breached in two years, before 1990, and expressed their desire to return to Da Lat for research.

I disagreed. They immediately sent a report saying that the Dalat reactor would be breached in two years to the International Atomic Energy Agency (IAEA).

The Vietnamese delegation here received information and reported back to the country. In the post-Chernobyl context, the leaders were very worried. I had to fly to Hanoi to report to the Council of Ministers experts and prove that the reactor was still operating normally.

In fact, the corrosion had existed before and I had noticed it since the survey to restore the furnace in 1976. From then until the foreign expert group issued a warning, it had been more than 10 years, but the corrosion had not expanded. I also researched and read many books on corrosion, and at the same time connected and worked with domestic electrochemical experts to make sure that the corrosion did not affect the safe operation of the furnace.

However, the arguments and gossip around make me tired.

That evening I was called to see General Vo Nguyen Giap before flying to Da Lat. I expressed my intention to resign, he suddenly became serious:

- Does that mean you surrender?

- Yes!

- Do you know what military law considers surrendering as a crime? Treason. At least you'll go to jail!

I had to keep quiet and leave.

In fact, more than 30 years have passed since then and the reactor is still operating well and safely. During his visit to the Institute in 1991, the then Director General of the International Atomic Energy Agency, Hans Blix, commented: "The Dalat Nuclear Research Institute is the place that has used the International Atomic Energy Agency's Technical Cooperation Projects most effectively in the world."

I continued working until the end of 1991, then resigned and was invited by the International Atomic Energy Agency to be the Chief Expert for the Asia-Pacific cooperation project, handing over the responsibility of operating the reactor to the next generation.

According to VnExpress Newspaper

Source: https://mst.gov.vn/nguoi-chi-huy-lam-song-lai-lo-phan-ung-hat-nhan-vo-my-ruot-nga-197250926082931155.htm