The most frequent concern in the public when it comes to nuclear energy is that a nuclear power plant suddenly can explode and explode like a nuclear bomb. The physical and thermodynamic response of this problem is certain: No. A nuclear power plant can not explode such as a nuclear weapon according to physics rules.
What is the main difference between nuclear reactor and atom bomb? What was the explosions in Çernobil and Fukuşima in the past and how did these risks completely eliminated in modern plants?
Why can not explode like nuclear bomb? Richization difference
For the explosion of a nuclear weapon, it is necessary to reach the critical mass in the microseconds of the fissil material and keep it together until the explosion moment of uncontrolled supercritic chaining reaction. This condition is only possible with very high enrichment rate and special blasting geometry.
- Nuclear Gun: About us 90% and above enriched by the ratio requires Uranium-235 (or almost pure Plutonium-239).
- Nuclear Power Plant: Only %3 to 5% uses low-rich uranium (LEU) which is enriched by the ratio.
95% of the rest of the Uranyum is Uranium-238, which is not fiscal. U-238 quickly cools the neutrons and slows down the reaction and makes it physically impossible to form a uncontrolled nuclear explosion. It is like to create a nuclear explosion with 3-5% enriched fuel, try to convert a beer into the flame ball, such as gasoline, which is 3% of alcohol rate; it can not take place physically.
| Comparison Criteria | Nuclear Gun (Bomba) | Nuclear Power Reactor (NGS) |
|---|---|---|
| U-235 Richization Rate | 90% and above (Silah Level) | %3 - 5% (Low Rich) |
| Response Speed | Microseconds (controlled supercritical) | Days/months (controlled criticality) |
| Purpose | Severe shock wave and sudden energy release | Stable, stable and predictable heat production Home |
| Physical Nuclear Explosion Probability | Basic function of design | 0% (Physically impossible) |
What was it to explode in Çernobil and Fukuşima?
The explosions in nuclear accidents in history are not nuclear explosions, chemical and thermal ( steam and hydrogen) explosions Tags:
- Steam Blast (Cherry - 1986): The positive gap coefficient of the old Soviet design RBMK reactor is flawed and the result of a faulty experiment, the water in the reactor suddenly overheated, a huge vapor pressure aired the upper cover of the reactor.
- Hydrogen Explosion (Fukuma - 2011): After Tsunami, the emergency diesel generators stopped cooling of the reactor while remaining under water. The zirconium sheaths of unfrigerated fuel bars have produced hydrogen gas by entering the chemical reaction with steam over 1000°C. Hydrogen gas in the roof of the reactor building led to a chemical explosion by contacting air. The protection shell is sturdy, has never been a nuclear explosion.
Modern (Gen-III+) How does reactors block these explosions?
The 3+ Generation (VVER-1200, AP1000, EPR) reactors such as Akkuyu built today are designed with courses extracted from all accident scenarios in the past:
- Negative Reactivity Coefficient: When the temperature of the reactor increases, the ability to swallow neutron by the physical properties of the fuel and moderator increases (Doppler expansion). When the temperature rises, the chain reaction automatically slows and stops itself.
- Passive Hydrogen Removers (PAR): Electrical energy-free passive catalytic recombinators combine hydrogen with oxygen with the help of the platin/paladium catalysts at the moment of hydrogen formed in the reactor, and convert it to water again; completely eliminates the risk of hydrogen explosion.
- Kor Holder (Core Catcher): The huge conical steel structure, located under the reactor pressure container, cools with special chemicals, taking into molten fuel (corium) in the worst scenario, and prevents contact of concrete ground or underground waters.
- Double Layer Protection Shell: The pre-stressed concrete structure of 1.5 meters thickness surrounding the entire reactor does not allow uncontrolled spread of any radioactive substance into the inside pressure pill and out.
Frequently asked questions
What spreads the environment if a nuclear power plant crashes?
In case of accident in modern reactors, the protection shell prevents leakage from external environment. A controlled ventilation is performed in extreme cases; these filters keep radioactive particles and iodine/sezium isotopes by 99.9%.
What happens if the nuclear reactor remains uncontrolled?
When the reactor goes out of operating parameters, the protection bars (SCRAM) drop into 2-3 seconds with gravity. In addition, emergency boron injections are instantly swallowed and the reaction is stopped.
Is the Chernobyl accident repeatable in today's reactors?
No. RBMK type reactors used in Çernobil have no positive gap coefficient and protection shell (containment). Today water cooled reactors have negative feedback and have double layer protection shells with meters thickness.
Resources
- IAEA, The Chernobyl Accident: Updating of INSAG-1 (Safety Series No. 75-INSAG-7.
- US Nuclear Regulatory Commission (NRC), Nuclear Reactors and Nuclear Weapons Differences: https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/reactor-risk-nx.html
- World Nuclear Association (WNA), Safety of Nuclear Power Reactors: https://world-nuclear.org/information-library/safety-and-security/safety-of-plants/safety-of-nuclear-power-reactors.aspx