About the heat carrier in a nuclear reactor

[hagopbul]

Hello:

I have small question , as I read about the ATF research in the news ,a question present it self , why no one does any research on heat carrier in nuclear reactor that can absorb nuclear radiation and change it to infra red radiation ?

Best
H

 

[Rive]

As long as the 'nuclear radiation' remains inside and has no significant leak then ~ all of it is absorbed and converted to heat (what includes IR radiation) anyway, regardless of the actual 'heat carrier'. So the answer is: because it does not really matter.

 

[hagopbul]

why it does not matter ?
if it absorbs more heat then less nuclear materials is needed to heat it to the needed degree

 

[hagopbul]

some energetic particles for example are absorbed into the concrete shield , and so on

 

[hagopbul]

not taking about leaking the radiation outside the reactor talking about the thermo cycle

 

[anorlunda]

heat carrier in nuclear reactor that can absorb nuclear radiation and change it to infra red radiation ?

No infrared, but heat. The most common material for that purpose is water.

 

[russ_watters]

why it does not matter ?
if it absorbs more heat then less nuclear materials is needed to heat it to the needed degree

All of the heat that is generated is absorbed. It has to be: conservation of energy demands it.

some energetic particles for example are absorbed into the concrete shield , and so on

The nuclear materials are submerged in a water bath inside the vessel. Virtually all of the energy (including radiation) is absorbed by the water or containment vessel -- if they didn't, they'd kill the plant workers! The vessel will, however, lose heat due to convection if it isn't insulated, but that would be a different and very small issue.

There's videos and photos online, but here's a bite-sized reactor that makes it easier to see, and they discuss ambient radiation levels around the reactor:


[maybe start about 2 min in, but there is critical info at 7min]

 

[Rive]

some energetic particles for example are absorbed into the concrete shield , and so on

Could you please try to give us an estimate about the ratio of the energy lost this way? Just a direct comparison of the radiation levels (in the core vs. in the drywell) would do I think.

 

[Astronuc]

why no one does any research on heat carrier in nuclear reactor that can absorb nuclear radiation and change it to infra red radiation ?

This question is rather strange, since nuclear, in-core structural materials are used to transfer heat from the fuel to the coolant, and the coolant passes heat to steam generators in a PWR, or directly as steam in a BWR, and the steam is used to power steam turbines (steam or Rankine thermodynamic cycle).

Heat must be removed from the core so that materials stay within specified operating limits with respect to temperature, i.e., well below melting. Without heat removal, temperatures in the reactor would increase, which was the problem at Fukushima or TMI-2.

The UO₂ fuel + fission products store a lot of heat, which is produced from the fission process and decay of fission products. When the reactor is shutdown, the fission process stops (except for those nuclides that undergo spontaneous fission), but the decay of fission products continues. It is the decay heat that must be removed when the reactor is shutdown. The ultimate heat sink for any power plant is the environment (ground water and atmosphere). The temperature is determined by the specific enthalpy or specific heat of the material and the mass of the material through which the thermal energy is distributed.

Anything hot will emit infrared energy, and if a material is hot enough, it will emit in the visible range as well as infrared.

 

[hagopbul]

Thanks for the information , although it didn't answer my questions completely , it was rich with information.

There is more than one type of radiation emitted from the core of the reactor what you are interested in obviously is heat that you transport to the torbine .

But there is other types of radiation that don't transforms into heat like gamma rays , and so on , (not talking only about gamma rays)

What we can do about that type of radiation , can we transform it into heat .

 

[anorlunda]

What we can do about that type of radiation , can we transform it into heat .

That's the source of your confusion. The energy of all forms of radiation convert to heat. Even gamma rays are absorbed by the surroundings, although they may penetrate deeper before being absorbed.

 

[gmax137]

not talking only about gamma rays

Of the other types, the alphas and betas do not pass through the reactor vessel walls; and most of the the neutrons are captured within the vessel. The neutrinos pass freely but do not carry significant energy overall. Interesting note, the first detected neutrinos were from one of the reactors at Savannah river.

 

[Astronuc]

But there is other types of radiation that don't transforms into heat like gamma rays , and so on , (not talking only about gamma rays)

As gmax137 mentioned, alpha and beta particles don't pass through the reactor pressure vessel, and in fact, most are stopped by the fuel and structural alloys in the core. Some betas might make it to the core shroud or baffle, which surrounds the fuel and directs the water up through the core. Gammas are more penetrating, but most are stopped before they get to the pressure vessel exterior. Gamma heating in the fuel is about 2.5 to 3.5% of the heating in the core.

Gamma rays are largely attenuated by the U and transuranics in the fuel. Gamma rays interact with matter by photoelectric effect for low energy gammas, by Compton scattering and by pair production. http://mragheb.com/NPRE 402 ME 405 Nuclear Power Engineering/Gamma Rays Interactions with Matter.pdf

The interaction of gamma rays and their effects in structural materials is one area if my research.

 

[hagopbul]

Thank you for your answers it was helpful