Do Thermal Neutrons Irradiate Their Shielding Water?

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Aeronaut
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Do Thermal Neutrons Irradiate Their Shielding Water?

Post by Aeronaut »

Can the shielding water be used to co-generate directly useful heat, or will that require a heat exchanger?
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chrismb
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Re: Do Thermal Neutrons Irradiate Their Shielding Water?

Post by chrismb »

Aeronaut wrote:Can the shielding water be used to co-generate directly useful heat, or will that require a heat exchanger?
If you have water of a sufficient thickness to effectively eliminate radiation, then its temperature will become 'waste heat'. You could pump it out with a heat pump. Look up 'Carnot cycle' and 'heat pump' and it should come clear to you.

The substances that 'cool' a reactor, that actually carry away the heat it generates are a smaller volume (and may be water) but that wouldn't be enough to 'shield' the radiation. You're looking for 'good quality' (viz. high temp) heat to get useful work out of it.

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Re: Do Thermal Neutrons Irradiate Their Shielding Water?

Post by MSimon »

Aeronaut wrote:Can the shielding water be used to co-generate directly useful heat, or will that require a heat exchanger?
Maybe. It depends on the impurities (including pH buffers) in the water and how well tritium can be scavenged. The answer as close as I can come without data is: "probably yes."
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Post by drmike »

On a submarine you use one heat exchanger to prevent radiation from getting into your turbines, on a normal plant you use two heat exchangers for safety. You can go direct and gain efficiency, but you lose big on the radiation damage to your turbines.

The impurities in the water absorb the neutrons and become radioactive. If you have pure water (hard to do!) it'd be less of a problem. But you'll still have tritium generated at some level and have to deal with it.

A heat exchanger just makes lots of problems go away. Until you need to refurbish the plant anyway!

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Post by Aeronaut »

drmike wrote:On a submarine you use one heat exchanger to prevent radiation from getting into your turbines, on a normal plant you use two heat exchangers for safety. You can go direct and gain efficiency, but you lose big on the radiation damage to your turbines.

The impurities in the water absorb the neutrons and become radioactive. If you have pure water (hard to do!) it'd be less of a problem. But you'll still have tritium generated at some level and have to deal with it.

A heat exchanger just makes lots of problems go away. Until you need to refurbish the plant anyway!
Hmmm... Are we talking about changing the cooling water once a decade, once a year, or once a month to keep the tritium at safe levels? Will the tritium and other products be suspended in the water, easy to flush out?

Thanx again.
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D Tibbets
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Post by D Tibbets »

Tritium at least would be the water. Tritium is an isotope of hydrogen so it would react chemically the same as hydrogen ( with some perhaps very subtle differences), so it would be incorperated into the water molecules (just like deuterium makes heavy water). To seperate the tritium you would have to do mass apectroscopy, repeated fractional distillation (boiling point is probably slightly different than regular water) or some other involved process.

Dillution with Huge amounts of water would be the easiest approach to the reactor waste water- dump it into the ocean, just don't get caught, and hope none of the products get concentrated in the food chain!


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Post by Aeronaut »

Thanx for the reality checks, everybody. I was hoping for a perfect machine (no tritium).

Shoulda outa known better. :wink:
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Post by MSimon »

Aeronaut wrote:Thanx for the reality checks, everybody. I was hoping for a perfect machine (no tritium).

Shoulda outa known better. :wink:
It is not a big problem.

First - Deuterium makes up .06% of the water coolant. And the D n cross section for thermal neutrons is:

0.57±0.01 millibarn

That is about: .0006 Barns.

http://prola.aps.org/abstract/PR/v87/i5/p785_1
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Post by Aeronaut »

Thanx again, MSimon. Sounds like a string of really small numbers to my lay eye. What blew me away was that the article you linked to was dated 1952. (!) Was there organized radiation and shielding research before 1910?
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Post by MSimon »

Aeronaut wrote:Thanx again, MSimon. Sounds like a string of really small numbers to my lay eye. What blew me away was that the article you linked to was dated 1952. (!) Was there organized radiation and shielding research before 1910?
A lot of the work came about due to the availability of nuclear reactors.

Before 1910? I'd have to do some research. One thing to look up would be workers who painted watch dials with radium. An interesting story.
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Post by Aeronaut »

No need to look it up- I was just wondering if you've had the same thought or had heard something about how atomic science got started. Put another way, whose shoulders did the Manhattan Project build on?

I saw a brief brief blurb about Madam Curie and her workers' health problems on the tube a few months back. GR followed in 1905. Coupling those ideas with the 4 or 5 test reactors leading up to the atom bombs made me wonder just when the Feds really got serious about atomic power. :shock:
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Post by MSimon »

Aeronaut wrote:No need to look it up- I was just wondering if you've had the same thought or had heard something about how atomic science got started. Put another way, whose shoulders did the Manhattan Project build on?

I saw a brief brief blurb about Madam Curie and her workers' health problems on the tube a few months back. GR followed in 1905. Coupling those ideas with the 4 or 5 test reactors leading up to the atom bombs made me wonder just when the Feds really got serious about atomic power. :shock:
There was a criticality experiment that went bad wrong during the Manhattan Project. That may have shaken the tree.

Also X-Ray technicians were known to have radiation problems.
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Post by icarus »

There was Enrico Fermi's "stack" that was the first pile of man-made matter that went critical ... Chicago. In parallel with Manhattan bomb project were the experiments with generating electrical power from stack heat at Windscale in NW England and led to first electrical power-generating reactor at Calder Hall, same location.

Lots of contaminated ponds that still need cleaning up there, don't get started on Hanford Washington, Savvanah River Georgia, Los Alamos or some of the Russian experimental sites .... nuclear power is mighty force to be reckoned with but like all sharp knives .... cuts both ways.

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Post by MSimon »

icarus wrote:There was Enrico Fermi's "stack" that was the first pile of man-made matter that went critical ... Chicago. In parallel with Manhattan bomb project were the experiments with generating electrical power from stack heat at Windscale in NW England and led to first electrical power-generating reactor at Calder Hall, same location.

Lots of contaminated ponds that still need cleaning up there, don't get started on Hanford Washington, Savvanah River Georgia, Los Alamos or some of the Russian experimental sites .... nuclear power is mighty force to be reckoned with but like all sharp knives .... cuts both ways.
The pile was well instrumented for radiation. They were concerned about it.
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Post by kunkmiester »

How hard is it to get pure water? Pure enough to make the irradiation negligible, anyway.
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