Is it useless to seal the sarcophagus? More neutrons, nuclear fission strengthens, Chernobyl may explode again

Fission reactions surge in concrete sarcophagus at Chernobyl nuclear power plant, risking another explosion. Thirty-five years after the nuclear accident, the number of neutrons picked up by on-site sensors has increased dramatically, a signal of fission that scientists have reason to believe is at risk of another runaway nuclear reaction. Scientists are evaluating the problem, however, and no alarm has been issued yet.

On April 25, 1986, Unit 4 of the Chernobyl nuclear power plant was shut down normally for routine maintenance. They will also use the shutdown for testing, but the reactor was left in an unstable state because engineers were blindly confident and violated safety regulations. Finally, in the early hours of April 26, the nuclear reactor melted and exploded catastrophically.

The uranium fuel rods, zirconium cladding, control rods and sand in the reactor core become lava-like radioactive material at high temperature, and then flow into the basement of the reactor hall, where they combine with steel and concrete to harden into a fuel-containing material structure. A year after the accident, they built a sheltering structure, commonly known as the Chernobyl sarcophagus, for the accident nuclear power plant to prevent nuclear leakage.

However, this sarcophagus was unreliable and rainwater could seep into it. As we all know, the occurrence of nuclear fission requires the "assist" of neutrons. But if neutrons are moving too fast, radioactive nuclei have difficulty capturing them. The infiltration of rain acts as a moderator, slowing the neutron so that it can hit the nucleus more efficiently, increasing the intensity of the fission reaction.

A heavy rain in June 1990 caused a dramatic increase in the number of neutrons in the sarcophagus, a phenomenon tracked by a Chernobyl scientist who came here risking exposure to radiation and sprinkled a solution of gadolinium nitrate . The solution absorbs neutrons, weakening the intensity of the nuclear reaction. A few years later, engineers installed gadolinium nitrate sprinklers on the roof, which could be controlled remotely to spray the liquid. However, these sprays can only exist on the surface and cannot effectively penetrate the surface.

In November 2016, Chernobyl built a new sarcophagus on the basis of the old one. The new sarcophagus is able to keep out the wind and rain, and the neutron count inside the sarcophagus has been dropping steadily since it was built. The rainwater accumulated in the sarcophagus in the early stage is also slowly receding under the condition of the heat released by nuclear fission.

While the situation in most places is beginning to be optimistic, the number of neutrons in one reaction chamber is slowly rising. Its peak neutron emissions have increased by 40 percent since 2016. Scientists' models suggest that the drying of the fuel would in some cases make neutrons play a greater role in nuclear fission, but the mechanism remains unclear.

If neutron counts continue to rise, then it's a real concern, and scientists need to figure out a way to intervene. Spraying a solution of gadolinium nitrate has proven to be ineffective because it cannot penetrate deep into the concrete. Another method is to use a robot to drill a hole and then insert a cylinder of boron, which acts like a control rod to absorb neutrons and weaken the strength of the nuclear fission reaction. But the problem is that the robot needs to be redesigned to survive high levels of nuclear radiation for a long time.

In fact, the smoldering smoldering of nuclear fission isn't Chernobyl's only problem. Plagued by intense radiation and humidity, the concrete in the sarcophagus was decomposing, producing more fallout. We hope that scientists will solve these problems as soon as possible, so as to save mankind from the plight of nuclear pollution.