Episode: 4523
Title: Nuclear Reactor Technology - Ep 1 - Nuclear Basics
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr4523/hpr4523.mp3
Transcribed: 2026-07-31 16:13:13 (official HPR transcript)

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This is Hacker Public Radio Episode 4523, for 2025-12-03
Today's show is entitled, "Nuclear Reactor Technology - Ep 1 - Nuclear Basics"
The host is Whiskeyjack and the duration is 00:11:24
The flag is Clean, and the license is CC-BY-SA
The summary is "This episode is the first in an 8 part series on nuclear reactor technology. - Nuclear Basics"
This episode is the first in an eight-part series on nuclear reactor technology.
What this series will cover?
I'm not a nuclear engineer or physicist, just an amateur with a hobbyist's interest in
the subject.
This is a politics-free series and the focus is on the technology of the reactors.
This series will focus on the civil nuclear industry with a particular focus on electric
power generation reactors.
I will discuss the technology, what it is, how it works, and some of the pros and
cons of different technologies, but I will try to avoid offering too many opinions on what
it's the best or worst of anything.
I won't cover military or naval reactors or nuclear weapons production reactors.
I won't cover fusion power as it is still in the experimental stages and I don't know too
much about it.
I won't cover research or experimental reactors with a few exceptions needed to illustrate
a point.
I also won't cover mining, refining, converting, enrichment or disposal.
I won't cover the parts of an electric generating plant outside of the reactor, such
as turbines, generators, transformers, cooling systems, and everything else that is needed
to make a functioning power plant.
I will instead focus on reactor technologies which are in commercial use today, plus some
of the more interesting samples of things being developed in some of the historical dead
ends.
I'm not interested in discussing any politics, just to nuts and bolts of technology.
I will try to keep explanation simple, and so will skilm over a lot of details, there
is far more that could be discussed on this subject than I have the time to make podcasts
on.
Also, I'm probably not the best version to get into that sort of detail.
Episode 1 will cover nuclear basics, including basic terminology and several versus military
nuclear material.
Episode 2 will cover nuclear fuel, including the different types, recycling of spent fuel,
uranium, and thorium resources, and medical isotopes.
Episode 3 will cover reactor basics, including slow versus fast reactors, moderators,
coolants, steam generation, refueling methods, and the 3 main commercial reactor types.
Episode 4 will cover the less common reactor types, including types which are no longer
used, some historical developmental dead ends, and some types which may be possibly making
a comeback.
Episode 5 will cover fast reactors, including the different types, some of their history,
why they were developed, and why they have so far only seen limited use.
Episode 6 will cover thorium reactors, including what is thorium, and how it differs
from uranium, why there is interest in thorium, what sorts of reactors can use thorium,
and why thorium has not yet seen widespread use.
Episode 7 will cover small modular reactors or SMRs, what the reason is for developing
them, what are the different ways they may be used, and where they are currently being built.
Episode 8 will cover generation 4 reactors, which is a collection of future technologies.
Nuclear basics, first we need to start with the basics.
I won't explain what an atom is, or what a nucleus or proton or neutrons are.
I assume you already learned that in school.
We need to define some basic terms first, however.
Isotopes.
The first is an isotope, an element is defined by the number of protons and electrons
that it has in it, an atom can also have neutrons.
Neutrons do not affect the chemical properties of an element.
To be a bit more precise, they do not affect it in ways that are easy to detect.
The number of neutrons, however, can affect the nuclear properties.
The number of neutrons in the atoms of an element can, in some case, vary,
resulting in multiple forms of each element.
Isotopes of uranium.
Uranium, as it occurs in nature, has two main isotopes.
One isotope of uranium is U235, which makes up approximately 0.7% of natural uranium.
The U is the chemical symbol for uranium, and the number 235 is the number of protons,
plus the number of neutrons in the nucleus of the atom.
Virtually all of the rest is U238.
U235 has the same number of protons as U238, but has three more neutrons.
Nuclear fission.
Nuclear fission is a random atomic nucleus is split, producing energy as a byproduct.
This will normally result in the atom becoming either a different element,
or a different isotope of the same element.
Some radiation is given off in the process in the form of neutrons or other particles, such as
alpha or bedic particles, or electromagnetic radiation, such as gamma rays.
Some small part of the matter is converted into energy in the process of this,
and it is this energy we are mainly interested in obtaining.
This is distinct from nuclear fusion, where two or more atoms or particles are merged
into one, producing a larger element or form of the same element.
Fission may happen spontaneously, or it may be induced by being struck by another particle,
usually a neutron.
Half-life.
Radioactive isotopes which decay spontaneously have what is called a half-life.
Half-life is a term to describe how quickly something spontaneously fissions.
The half-life is a time required for half of the existing material to spontaneously
fission. This can happen repeatedly, so there is no end to the process as long as any of the original material remains.
This half-life could be anywhere from a fraction of a second to billions of years.
An isotope with a very short half-life gives out more radiation in a given period of time than one
that has a very long half-life. For example, the common element potassium 40, which is found in many
rocks such as granite, has a half-life of 1.25 billion years. This means that it will be around for a very long time.
However, that also means that it is not very radioactive as a rate of decay is very slow.
Fisile versus fertile. U235 is fisile. That is, it will take active part in initiating and
contributing to a nuclear reaction. U238 is fertile. It will not initiate a nuclear reaction.
However, if U238 is hit by a neutron, it can be converted into another element which is fisile.
It is very important to understand a remember what isotopes are and the difference between
fisile and fertile in order to understand nuclear power.
Enrichment of isotopes. Enrichment is a complex process which increases the percentage of
U235 isotope in fuel from the natural 0.7% to a higher level. Typically between 3 and 5%
in standard commercial fuel. It does this by extracting some of the U238, leaving behind a mixture
which has a higher proportion of U235. While many nuclear reactors are designed to use and
rich to uranium, it is not strictly necessary in order for them to work and some commercial
reactors use natural uranium. There are a number of different ways that enrichment can be performed,
but it won't be covering them in this series. Civil versus military nuclear material. Under
international convention, nuclear material is divided into civil and military categories.
The difference between the two is based on the proportions of different isotopes.
Military material has many more restrictions on who can have it and how it is accounted for
than civil material. Civil material hover must still be accounted for and tracked under
international treaty. These rules have a direct effect on reactor designs as we shall see.
Uranium. Civil uranium is uranium that has less than 20% U235. Military uranium is 20% or higher
U235. This is why you see so many small reactor designs as state they use fuel and rich to 20%.
It's actually typically 19.75% in order to stand with the limit. This is the highest
taken go in civilian hands. Most civilian nuclear power reactors which use in rich uranium
use 3 to 5% enrichment due to economic reasons. The higher the enrichment level, the more expensive
the fuel. Also, to supply a fuel higher than normal commercial that has 3 to 5% levels,
is very limited and there are very few sources. Plutonium, just like with uranium,
several versus military plutonium, is defined by the ratio of isotopes. Plutonium does not
exist in nature and significant quantities but can be created artificially. In spent fuel
from civilian power reactors, the Bain isotopes are PU238 239 240 240 1 and 2402. Typically in
spent fuel this is 50 to 60% PU239 25 to 30% PU 240 10 to 15% PU241 and a few percent each
of PU238 and PU242. PU239 and PU241 our fizzile will PU242 is fertile. Civil plutonium is defined as
having 20% or more PU242. The PU239 is an is the isotope desired for making weapons,
and PU242 is considered to be a serious contaminant from that perspective. Unlike with enriching
uranium, it is not feasible to separate PU242 from PU239. The only feasible way to create plutonium
with a high level of PU239 and a low level of 240 is to avoid making PU242. Weapons great plutonium
is made in special military reactors, although two of the UK's magnox reactors were designed
as dual use models intended as military reactors but producing electric power as a buy product.
I won't go into how military reactors for producing weapons great plutonium operate
as it is not relevant to our discussion on civil nuclear power plants. It is also not a topic
with very much public information being available or for which I have much personal knowledge.
Conclusion in the first episode of this series we discussed what this series will cover
some of the basic nuclear physics terminology and the differences between civil and military
nuclear material. In the upcoming episodes we will discuss some of the basic engineering
aspects of reactors, the various types of commercial reactors including common and uncommon ones,
nuclear fuel including uranium plutonium and thorium, medical isotopes, small modular reactors,
and the areas of research being conducted into new reactor technologies.
In the next episode, however, we will cover types of nuclear fuel, recycling of nuclear fuel,
uranium and thorium resources and medical isotopes. This concludes the first episode of
an eight-part series, a nuclear reactor technology.
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