Physics

How has nuclear energy modified since Chernobyl?


Poignant and bleak, the critically acclaimed HBO sequence Chernobyl revisits a troublesome chapter in historical past to inform an essential story concerning the function of science in society. Whereas parts of the plot and characters have been embellished for TV, its an distinctive portrayal of what can occur when a neighborhood ignores the indicators of an impending catastrophe (i.e. local weather change) and contains surprisingly correct and accessible explanations of nuclear physics. 


On twitter, the present has additionally reignited an essential dialogue on nuclear energy and its related hazards. It’s essential to acknowledge that whereas some dangers will at all times be there, nuclear energy is definitely safer than ever, and importantly, it might assist curb our insatiable urge for food for fossil fuels.


To study extra about this funky world of radioactive physics, we’re going to reply some questions on how our nuclear panorama has modified since 1986 (I’d say spoiler alert, however that’s not likely relevant to historic occasions that occurred a long time in the past). 

Picture credit score: HBO/Chernobyl

How a lot nuclear vitality can we use right this moment?

As of July 2019, 416 nuclear reactors are working in 34 international locations, they usually’re producing about 10.three% of the world’s electrical energy. That’s a marked drop from their peak share of 17.5% of worldwide electrical energy in 1996. Excluding China, the world’s nuclear manufacturing has really been slowly, however steadily declining, maybe as a consequence of elevated contributions from wind, photo voltaic, and different renewable vitality sectors. So, nuclear energy nonetheless contributes a good portion of energy to extra developed international locations, however it’s positively not rising on the price it was within the 80s, partially as a result of international locations will not be investing in constructing extra reactors. With pushes in direction of fossil-free vitality, maybe nuclear energy will turn into extra standard, however the international vitality panorama is rising more and more complicated.

Are Chernobyl-like reactors nonetheless in use right this moment, and are reactor cores nonetheless made from graphite?

The kind of reactor used on the Chernobyl plant known as an RBMK-1000 reactor (it stands for Reaktor Bolshoy Moshchnosti Kanalnyy/Excessive Energy Channel-type Reactor). Whereas human error, coverage failures, and a lack of know-how all performed a job within the catastrophe, design flaws within the RBMK reactor are additionally in charge. One of many principal points with some of these reactors is that they have what’s known as a “optimistic void coefficient”. Which means when the coolant is misplaced, the speed of fission would improve. Through the accident, an overproduction of steam led to extra fission, an enormous temperature and stress improve, which ultimately led to an explosion.

After 1986, all remaining RBMK-1000 reactors underwent design updates to repair these flaws, discovering 58 particular person points with the system. All RBMK-1000 reactors have graphite cores, which comprise mazes of cavities that maintain the radioactive uranium gas rods. Nearly all of adjustments made concentrate on the reactor’s graphite core. They added extra absorbers in order that reactions would stay secure at low energy, they elevated the variety of management rods within the core, and elevated the gas enrichment of uranium required at energy crops. These reactors aren’t constructed anymore, however 10 are nonetheless working in Russia.

Piece of graphite from the reactor core. Credit score: HBO/Chernobyl

Within the HBO sequence, one of many first harbingers of catastrophe post-explosion had been small chunks of graphite proven strewn alongside the bottom whereas firefighters labored to extinguish a blazing inferno.  If the fabric that’s purported to separate folks from extremely radioactive uranium gas is now not there, that’s a reasonably large downside. 

So, why graphite? Graphite is an inexpensive materials, and it allowed the Russians to make use of lower-grade uranium as gas. The management rods, that are purported to decelerate the speed of fission contained in the core, had been made from boron tipped with graphite. The boron slowed down the response as deliberate, however when the graphite interacted with the gas because the rods are eliminated, it really elevated the speed of fission. So when the employees tried to decelerate the response earlier than the catastrophe, they inadvertently sped it up. 

As a substitute of utilizing graphite cores, reactors these days are designed utilizing water as each a coolant and a moderator (a moderator helps decelerate neutrons with a view to make the fission course of simpler). In these reactors, both gentle or heavy water, that are distinguished by their relative proportions of deuterium and hydrogen, are cycled by means of the core construction. Whereas nothing is 100% protected, some of these reactors have faired higher than the RBMK-1000.

Diagram exhibiting the circulation of water in a reactor Picture Credit score: Union of Involved Scientists

Do folks nonetheless dwell in Chernobyl? Is it protected?

Whereas greater than 1,000 sq. miles round Chernobyl is formally designated as uninhabitable, and whereas it is technically unlawful to dwell throughout the exclusion zone, about 100 persons are estimated to be dwelling there right this moment. Its present residents moved again through the weeks and months after the catastrophe as a result of regardless of the radiation dangers, it is nonetheless dwelling. 

Whereas some argue it is an ecologic paradise, the soil remains to be closely contaminated with radiation. From the soil, radioactive ions enter the meals chain, spreading to crops and animals, predator and prey. Whereas animals have been discovered with mutations, research present that their inhabitants numbers are thriving. In a means, the advantages of a human-less atmosphere far outweighs the hazards of nuclear contamination. So Chernobyl nonetheless isn’t a protected place to dwell for people or animals, however then once more, any location has its drawbacks. 

Will we nonetheless use iodine tablets to guard towards radiation poisoning? 

Other than those that died from acute radiation poisoning on the energy plant, most deaths after the Chernobyl catastrophe had been the results of radiation-induced thyroid most cancers. Individuals who ingested iodine tablets, nonetheless, had been much less prone to be impacted by this radiation. To supply hormones, your thyroid wants to soak up iodine, however in a traditional atmosphere, this iodine isn’t radioactive. The explosion at Chernobyl launched the most important ever quantity of a radioactive isotope known as iodine-131 into the air. As soon as this radioactive iodine enters the human system, it is absorbed by means of the thyroid, dispersing radiation all through the physique. The concept for iodine tablets is that if sufficient nonradioactive iodine-127 is ingested, then it will stop the radioactive iodine from being absorbed. 

Picture credit score: HBO/Chernobyl

As a result of nuclear disasters are uncommon (fortunately), there may be not a whole lot of information exhibiting how ingesting iodine tablets reduces publicity to radiation. We do know that whereas it could defend the thyroid towards iodine-131, it doesn’t defend different organs, and it doesn’t defend towards different radioactive isotopes. It isn’t a catch-all “anti-radiation drug”. After the 2011 Fukushima catastrophe, iodine tablets had been distributed to residents inside a 10-mile radius of the reactor, however the effectiveness of this technique is but to be seen. Nonetheless, the US Nuclear Regulatory Fee is ready to distribute iodine tablets within the occasion of a nuclear catastrophe. 

Do you have got any questions on Chernobyl or nuclear physics? Ask within the feedback beneath!

–Lissie Connors

Lissie Connors (@LissieOfficial) does social media and writes about science for Physics Central. Uranium is certainly one of her favourite components. 


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