Despite a great deal of theoretical research on the subject, achieving inherent safety remained a major engineering difficulty. Wang decided to have his team focus on the subject, as he believed safety was the key to the future development of nuclear energy.
In 1982, Wang and his colleagues began to research Low Temperature NHR (nuclear heating reactors). It was his wish that any reactor they developed should not only be safe, but also able to generate district heating to help solve China's energy problems. The team spent a year discussing proposals, visiting and investigating different types of heating reactors in Europe, before finalizing their own design.
Their 5MW Nuclear Heating Reactor (NHR-5) went into operation in 1989. Low temperature, low pressure and low power density, it featured a natural circulation mechanism to remove residual heat, as well as the hydraulic-driven design of control rods. Many key technological breakthroughs were made.
The NHR-5 is considered to be forward-looking, as using natural circulation in a water cooled nuclear energy system later became one of the main technological trends of the 21st century. The project also won first prize of China's State Scientific and Technological Progress Award in 1992.
In 1981, Wang was working in Germany's Juelich Nuclear Research Centre as a visiting scholar, when he came across the modular High Temperature Gas-Cooled Reactor (HTGR), a newly developed concept proposed primarily in Germany, which was based on the lessons learned from the Three Mile Island accident. Its design aimed to greatly improve nuclear safety by eliminating the possibility of a core meltdown.
In 1982, he returned to China and was appointed deputy director of the Institute of Nuclear Energy Technology at Tsinghua University. While developing the Low Temperature NHR, he also began to plan the research and development of HTGR.
Wang decided to focus on a modular reactor based on what is called "pebble bed technology", which is characterized by the use of spherical fuel elements known as pebbles. As its name suggests, these pebbles are piled up to form a bed, which serves as the reactor core.
