The core of this nuclear fuel ball is uranium dioxide particles, which are smaller than the lead of a pencil and the products produced after the reaction are firmly sealed, and the highest temperature of 1600 °C must be resisted, and the shell material and preparation process of the particles are extremely difficult.

After West Germany sent the nuclear fuel production line to Unigroup, the latter has been working on this pebble-bed reactor high-temperature gas-cooled reactor technology.

There are a lot of failures on the two pebble-bed reactor nuclear high-temperature gas-cooled reactor experimental reactors built by Germany, the main defect is that the circuit is seriously polluted by metal fission products mixed with graphite dust, originally these nuclear elements should not run out of the fuel balls, but this German-designed pebble bed reactor is based on the very small flow friction of graphite balls, but the lubrication characteristics of graphite balls in the helium environment are not very thorough.

When the two experimental reactors were established, there was a lack of in-reactor measurement devices in the core, so it was impossible to accurately measure the temperature and neutron flux rate in the reactor.

At that time, this measurement problem had not been solved until the experimental reactor was shut down, and the temperature could only be measured by using nearly 200 temperature monitoring balls containing a set of fuses into the reactor.

Of course, these balls can only record the highest temperature they have experienced, and cannot give a spatial and temporal distribution of the temperature of the fuel balls in the core, and the first alarm results are not available until more than a year after the balls are released.

Examination of the monitoring balls flowing out of the core found that a significant part of the in-ball fuses had been completely blown out, indicating that the local temperature of the core had exceeded 1,700 degrees, far exceeding the previously calculated values. It is this high temperature that allows the nuclear elements inside the nuclear fuel ball to escape, and if this problem of uneven core temperature is not solved, no amount of shell to the nuclear fuel ball package is useless.

In order to solve this problem, Unigroup University has also developed a set of experimental device for measuring the equivalent thermal conductivity of the full-size pebble bed of the core of the high-temperature gas-cooled reactor, which can carry out the equivalent thermal conductivity measurement experiment of the static graphite pebble bed under vacuum and helium conditions.

In addition, Ziguang University has also redesigned and developed the nuclear fuel ball itself, during which Ziguang University has also customized a lot of special equipment to Huaxing Technology Group Company, and also participated in the formulation of some process technologies.

The two parties have jointly developed an all-ceramic triple isotropic coating technology, which is also the most advanced coating technology at present.

The core of uranium dioxide should be coated with four layers of material by chemical vapor deposition, the innermost layer is a loose pyrolytic carbon layer, which is responsible for absorbing gaseous nuclear reaction products and relieving stress, and there are two layers of dense pyrolytic carbon layer and one layer of silicon carbide.

Huaxing Technology Group Co., Ltd. is the most powerful technology in China in terms of high-precision machining technology, and has provided high-purity graphite and silicon carbide materials for Unisplendour University.

Through experiments, the core after this coating process can be kept intact without damage under the continuous test of 450 hours at a high temperature of 1800 degrees, effectively preventing the leakage of radioactive materials.

This new process is much higher than the performance of the nuclear fuel core developed by the previous German process, and the safety of the nuclear core in the nuclear fuel is ensured to the greatest extent.

After "dressing", the coated particles and the matrix graphite powder are injected into the mould and pre-pressed into a core ball with a diameter of 5 cm. After that, it is encased in a 5 mm thick graphite spherical shell, which is finally shaped into a fuel ball with a diameter of 6 cm. This graphite spherical shell, known as the "fuel-free zone", is another barrier against the leakage of radioactive material from the core.

After a series of technological processing, the nuclear fuel ball can withstand more than 1,800 drops from a height of 4 meters, which is far greater than the technical index requirements of 50 times, ensuring the reliable sealing of the internal nuclear fuel.

The coating technology of the core is only one of the steps, a large number of core cores also need to be wrapped into a core ball, and the outside is also wrapped with a layer of reinforced graphite shell, the process is also very complex, and the pressure of 300 megapascals is used isostatic pressing equipment, vacuum furnaces, high-precision turning machine tools, robot arms and other equipment.

These equipment are basically donated by Huaxing Technology Group Company.

Of course, Unisplendour University has also provided a lot of nuclear technical talents and technical patents for Huaxing Technology Group Company.

Compared with the vast majority of countries, the technology of Ziguang University in high-temperature gas-cooled reactors has reached a very high level, especially in terms of power and combustion efficiency, which has completely reached or even exceeded the level of western developed countries, which is very advantageous.

Although the high-temperature gas-cooled reactor technology Eagle Sauce was the most advanced in the 80s of the last century, after the construction of Eagle Sauce domestic nuclear power plants stalled, Eagle Sauce's technology research and development in this area also stagnated.

Yang Jie was also lucky to get a technical team that continued to develop thorium-based molten salt reactor nuclear power technology, and successfully brought it to China, forming a situation in which there are two mature fourth-generation nuclear power technologies in China.

Although Eagle Sauce also clamored a few years ago to develop the fourth generation of nuclear power technology, including thorium-based molten salt reactors and high-temperature gas-cooled reactors, the real money was not much, and the previous technical team was scattered.

Compared with the nuclear power technology of thorium-based molten salt reactors, Unigroup University immediately solved some of the technical shortcomings of high-temperature gas-cooled reactors, but it still has to face a big problem in the design of pressure vessels.

Although the efficiency of the high-temperature gas-cooled reactor designed by Unigroup University is much higher than before, the core is still very large, and the pressure vessel is still very large and heavy.

Previously, when Tsinghua Unigroup developed a high-temperature gas-cooled reactor, it originally wanted to use the helium main loop to directly drive the turbine to generate electricity, so as to obtain better thermal efficiency, but at that time, the helium-propelled turbine had no ready-made application, so the second loop was chosen to drive the steam turbine.

However, after seeing that Huaxing Technology Group has made great progress in carbon dioxide supercritical generator sets, it has now cut off the steam generator and changed to the design of carbon dioxide supercritical generator sets, and it is also compatible with Huaxing Technology Group's high-temperature electrolysis hydrogen production equipment.

Despite this, the cost of high-temperature gas-cooled reactors is much higher than that of thorium-based molten salt reactors.