Nuclear Power - Pros and Cons

Kinda curious,does any better radiation shielding other than "Lead.Lots of it." exist?

Secret Signature

IIRC aluminium also works well.

As does areogell, which has been used in military aplications for a bit....

Suposasdly... since well nuclear programs are classified.

edited 26th Apr '16 1:26:38 PM by Imca

There are three factors that determine how big a dose of radiation you get: Time of Exposure, Distance From Source, and Shielding. Practical radiation protection tends to be a job of juggling the three factors to identify the most cost-effective solution.

• Alpha particles can be stopped by a sheet of paper.
• Beta particle shielding is accomplished with low atomic weight materials: plastic, wood, water, or acrylic glass (Plexiglas or Lucite.)
• Almost any material can be an effective shield against Gamma or X-rays if used in sufficient amounts. A thin sheet of lead offers perhaps the best protection-to-weight ratio, but a foot or two of concrete works just as well, if cost is an issue but size and mobility are not.

edited 26th Apr '16 2:01:14 PM by pwiegle

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Isn't water also often used as a raidiation sink? Basically the water becomes raidiation instead of something else.

"And the Bunny nails it!" ~ Gabrael "If the UN can get through a day without everyone strangling everyone else so can we." ~ Cyran

Clearly this means we need to pack all our nuclear waste in boxes of lead and drop them down the Mariana Trench.Then research giant robot technology for any aftermath.

Secret Signature

Where is water used as radiation sink...?

"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman

The only real requirement for radiation shielding of the type you're talking about is mass. As much mass as possible between the radiation source and the thing you want shielded. The more mass in the shield, the more likely it is that the radiation will hit the atoms in the shield instead of hitting the atoms in your body (which is the thing you're trying to avoid). Normally people like to use dense materials (like lead) because that allows you to put a large amount of mass in a small volume of space, but that's not strictly necessary.

This means that yes, water can (and is) used as radiation shielding, because it's both reasonably dense and extremely cheap. (It also has the added benefit of high thermal conductivity, meaning it will keep any radiation source it's shielding cool, as well.) The most obvious example of this are spent fuel pools, which are literally giant pools of water with spent fuel rods (which are still radioactive, but no longer pure enough for use in reactors) at the bottom. XKCD did a What If article on them.

Really from Jupiter, but not an alien.

Speaking of XKCD, here's another big plus in nuclear power's favor:

Fuel Energy Density (in mega-joules per kilogram)

• Sugar: 19
• Coal: 24
• Fat: 39
• Gasoline: 46
• Uranium: 76,000,000

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Questions:

• Are photovoltaic technologies—direct radiation to electricity it seems—applicable to fission power as well?"
• Does say, uranium's energy density mean that a nuclear power plant be able to keep producing electricity without continuous resupply or does that work differently than I imagine?

Look with century eyes... With our backs to the arch And the wreck of our kind We will stare straight ahead For the rest of our lives

While I am not sure on the voltaic panels.

The uranium depends, if it is just a small reactor for something like a ship the answer is yes, they only really refule that when the ship goes in for its midlife mantiance.

For something big like a powerplant, the answer is no, because the amount of energy that humans consume is so mind boggling that even WITH the energy density of uranium they still require a continuous supply of fuel..... its one reason why nuclear is practically required.

Admitantly the definitions of contentious varry, you dont like constantly have to pump uranium into it or any thing but without a source of fuel rods they will shut down suprisingly fast, especialy since a reactor cant change its fuel consumption relitive to the amount of power being consumed.

Betavoltaics are a thing, but in practice a live nuclear reactor is too hostile an environment for a photovoltaic panel. Also, most of the energy is not produced in photovoltaics-friendly way.

"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman

It is possible to do nuclear power without a heatengine - But those reactor designs are generally.. very inappropriate for use inside a biosphere. https://en.wikipedia.org/wiki/Fission_fragment_reactor Very shiny if you want a 2 gigawatt powerplant that clocks in at ten tonnes and needs very modest radiators - Not so cool if you care.. like, at all, about failure modes. So this is a way to power extravagantly powerhungry activities in space, where you don't care if there's a chance your powerplant turns itself into a fireball.

There's no practical way to host that fission fragment design on Earth?

Look with century eyes... With our backs to the arch And the wreck of our kind We will stare straight ahead For the rest of our lives

Contrary to popular belief it's very clean.

The biproducts tho...

GIVE ME YOUR FACE

... Bottom of a mineshaft and seal it before you turn it on, I guess. That's how I'd test the prototype for this thing, but it's just not what it's for - It's a nuclear rocket that can also be used to generate oceans of electricity.

This is super neat for space - want to visit europa and run a base there for a year? This will let you do that, but it's as safe as any rocket engine is - That is, "Not that safe", and runs on bomb-grade fissiles, which.. completely ruins the economics for grid use.

From a physics standpoint, sure — there's no reason you can't take electromagnetic radiation from the gamma spectrum instead of the visible (or is it ultraviolet? I'm not even sure) spectrum and turn it into electricity. From a practical standpoint, though, the engineering problems of doing it that way are worse than just turning it into a giant steam turbine.

Depends on what you mean by "continuous". Unlike coal, gas, or oil power plants, which use fuel at a constant rate, nuclear powerplants are refueled once every few years. IIRC there are some naval reactor designs whose fuel life is longer than the expected life of the ship (a few decades), so the reactor will never need refueling before it's retired. So it's not like they're feeding a steady stream of uranium into a reactor like you would with fossil fuels, but it's also not the case that they can just run forever with the same chunk of uranium.

edited 5th Feb '17 9:43:41 AM by NativeJovian

Really from Jupiter, but not an alien.

Because nuclear fuel rods are subject to extreme heat during a chain reaction, there comes a point where they're no longer considered safe to use, even though you could conceivably get more out of them if you ignored safety standards. (Kind of like how the arrestor wires on a US Navy aircraft carrier are replaced after exactly 100 uses — no exceptions.)

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Ultraviolet is easier as the individual photons have a higher energy but the threshold photon energy will vary depending on exactly what material you're using for the photovoltaic cell. Some work in UV, others in the visible and I think there are some designs that are optimised for the near infrared.

Sorry to restart this thread but I have a question: when it comes to building a nuclear power plant, what's the ideal time period needed to finish building a plant?

That depends on a large variety of factors, buildings can go up safely in as little as six months, or take years to construct depending on things like... the number and skill of your workers, what the land you are building on is like, what the permits and regulations where you are building are like. And for nuclear piles you have even more variables like what kind of nuclear facility are you building, there are many different types and they all have different challenges.... or even how many cores it is supposed to have.

What your asking is one of those questions that seems simple, but really isnt without more details.

Well, would five years be an applicable time period to build a nuclear power plant, like with Chernobyl (1972-1977) or not?

edited 6th Jun '18 6:18:19 PM by HallowHawk

I suspect that building a safe and reliable plant (assuming the factors that that Imca mentioned are all in place) is potentially faster than it was in the 70s.

Politics is the skilled use of blunt objects.

The main obstacle to building a plant is the NIMBY issue.

Disgusted, but not surprised

At least in the US, most obstacles to building reactors are regulatory rather than anything else. It's harder to get permission to build and get the build certified, etc, than to do the actual building. Five years is certainly a reasonable amount of time assuming there's no major opposition to the project (lawsuits over the proposed site, etc), and if your story has some major group throwing their weight behind it, they could probably get it done significantly faster than that.

Of course, as says, in real life (again, at least in the US), major opposition to the project is virtually guaranteed.

Really from Jupiter, but not an alien.

My father could probably answer that question. He was in charge of construction and startup of a nuclear power plant here in the US, then became a consultant and basically did the same thing in foreign countries, such as China and South Africa.

Unfortunately, when he divorced my mother, he basically divorced the rest of the family, as well. I haven't heard from him in five years...

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