Today, I would like to discuss one of the many specific problems I have with energy production. For too long our nation has relied on fossil fuels to supply energy. There are many technologies available that can produce far more energy with far less waste. Unfortunately, some of those energies aren’t progressing with the times as I believe they should be. One of the biggest offenders is nuclear power. Right now, most nuclear energy produced in the world is from pressurized water reactors. Which are widely used because their method of fission relies on delayed neutrons. The fuel in civilian nuclear power plants is usually enriched to no more than six percent U-235, which is the isotope of Uranium that has a high probability of fission when exposed to a thermal neutron. On average, 2.43 neutrons are released per fission event. The initial fission event is caused by source neutrons. Source neutrons are an inherent property of the fuel, which also consists of U-234 and U-238. There are three types of source neutrons: Intrinsic, photo, and transuranic. If the control rods are withdrawn, these source neutrons begin the fission chain reaction in the U-235.
After a U-235 fission event, I early stated that an average of 2.43 neutrons are produced per event, which are responsible for the continued nuclear chain reaction. The energy levels of neutrons released from a fission event can be categorized in two ways: Prompt neutrons and delayed neutrons. Prompt neutrons are neutrons born less than one femtosecond after the fissioning events, and they have much higher energy levels than the latter. The latter neutrons I speak of are delayed neutrons. They are born between one femtosecond and up to 54 seconds after the fission event. Delay neutrons are born at much lower energies. The probability of having a prompt neutron being born after a fission event is greater than .99. Therefore, the probability of a delayed neutron being born is less than .01.
U-235 has a large microscopic cross section for absorption of a thermal neutron. A thermal neutron is a neutron that has a kinetic energy level of less than .1 ev (electron volt). To make these neutrons reach that level, they need to undergo collisions to lose energy. This is made possible by the moderator. Which is water. The neutrons undergo collisions with the hydrogen atoms in the water and slow down to thermal energies. The time and distance it takes a neutron to reach thermal energy levels is referred to as slowing down length. Because prompt neutrons have a relatively high birth energy, in a pressurized water reactor most prompt neutrons escape or become resonantly absorbed and do not cause a fission reaction. The delayed neutrons are responsible for the sustained fission reactions. Therefore, we are wasting 99% of the neutrons produced and creating much more radioactive waste due to the production of transuranic elements in the core.
There are fast-neutron reactor designs out there that are much more efficient, but they are much more dangerous. Pressurized water reactors have a negative temperature coefficient of reactivity, which means if core temperature goes up, therefore the moderator gets less dense. This increases the slowing down length and more neutrons escape or become resonantly absorbed. This means if temperature goes up, then power goes down. In breeder reactors, they have a positive temperature coefficient of reactivity. Which means if core temperature goes up, then power goes up. This is a problem if you have an earthquake and a tsunami at the same time and lose power to the main coolant pumps/ reactor coolant pumps. The core melts down. This is what happened in Fukashima.
I hope y’all enjoyed my post. Please comment.
Wow very informative
Thank you for your kind and very thought out conclusion.
While most of this is way over my head, I still found this subject quite interesting. I’ve always heard the common argument that while nuclear power has extreme dangers associated with it, there is no more efficient way to generate power without obliterating the environment a la fossil fuels. Is this more of a myth than fact?
Nuclear energy generation is safe as long as you follow all the rules and regulations established by the Nuclear Regulatory Committee. Also, here in America, we use the hot channel concept when constructing power plants. Which means we take into account all the worst case scenarios when designing power plants. Natural disasters need to be factored always. Nuclear power generation is much more efficient and environmentally friendly than fossil fuel. The only negative byproducts are radioactive waste, but there have been significant developments in science that can use these radioactive isotopes for research.
Rather the potential energy go to waste than to give it away. The dilemma you propose would have a severe impact on profit margins to the nuclear industry.
How would making more energy and having less waste affect their profit margin? Also, they wouldn’t have to spend as much money getting rid of nuclear waste and finding places to store it while it decays. They wouldn’t be giving any away, they would just produce more energy with far less waste.
its a sticky business
I agree nuclear energy policies need modernized to promote an improved marketplace that calls for innovation that creates less waste.
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Word up.
This was a very intriguing read. I think that, as a nation, we give nuclear power a bad rep, if only because of meltdowns. In reality, the only reason they happen is either due to some extraneous circumstances that make management of the core extremely difficult, or incompetence, the latter of which can be solved with good old-fashioned regularly-scheduled competency tests and stress tests. If we didn’t shun nuclear energy, I think we could completely get rid of the sources that are a lot less resource-efficient that do constant damage to the environment. What do you think about this hypothesis?
I agree. I think a lot of negative press comes from smear campaigns perpetuated by the fossil fuel industry, but that may be me being paranoid and conspiratorial.
Excellent points, for a breeder reactor what controls can be put in place to reduce the possible effects of a positive temperature coefficient incident.
Redundant power supplies for coolant pumps and plant auxiliaries to prevent a loss of cooling casualty.
I downloaded the tinder app and it sent me here…..when do I start swiping right? Trying to hit legs Monday señor McNerdy?
Yes. Leg day on Monday. Thank you for your kind words. I know it’s hard for you to make them come out of your jarhead.
Hey Ron! I recently downloaded tinder too! My grandpa said I needed a girlfriend. Best of luck in your endeavors into finding true love. I hope I got me a keeper. Thanks – Sal
p.s. Feel free to email me at sal@sal.com if you ever want to hang out.
I can’t believe my site is already bringing love birds together.
Very interesting read. 1 question, you said civilian power plants are enriched to a Max of 6% U-235. Is there a maximum enrichment for non-civilian nuclear plants?
Anything greater than 90% enrichment is considered weapons grade. This is because an excess of Plutonium would be created. If your wrap Plutonium in Beryllium, It starts emitting millions of neutrons per second. Which would be handy triggering a nuclear bomb. To answer your question though, that’s classified information.