Could you reduce the amount of concrete by increasing the amount of tungsten?

Not really. You have to stop neutrons and gammas. Concrete does neutrons but not gammas, tungsten does gammas but not neutrons.

You can also use water on neutrons or lead on gammas. There are many combos and composites.

Oh and neutrons cause more gammas when they get absorbed. Sometimes there are repeated layers, 3 or 4 times. If you have even tiny impurities in your shield you can get huge unexpected capture gammas

It's a rich tradition for reactors to start out with too little shielding though. Like the Japanese nuclear powered cargo ship Mutsu fired up for the first time, realized they didn't shield well enough, and spent 4 years fixing/retrofitting more shielding.

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LargoLasskhyfv 2 days ago | parent [-]

Is anybody considering the research into and use of metamaterials for shielding instead? Like 2D-twisted-hyperhexasomething?

	▲	acidburnNSA 2 days ago \| parent \| next [-]
		People are looking into it, but I don't think there's all that much promise. Fine structure of shielding doesn't really matter to an energetic particle that's blowing through meters of it. Gamma rays are stopped by electron density. Electron density requires high mass density heavy (high Z) nuclides. Neutrons are stopped by light nuclei via conservation of momentum, and by neutron absorbing nuclei like boron. If metamaterials can be made with higher density electrons in a way that's cheaper than lead and high hydrogen density that's cheaper than concrete, paraffin wax, or water, then I guess it could be interesting.
	▲	godelski 2 days ago \| parent \| prev [-]
		I used to work on novel shielding designs. There's some pretty interesting stuff out there but in the vast majority of situations it is just cheaper and easier to pour more concrete. To add to acidburn's comment, material choice is also highly dependent on the energy levels and particle types. At high energies you basically just maximize mass. At lower energies (more typical for reactors) you can start taking advantage of atomic cross-sections and electromagnetism. That's why they like borated concrete, high neutron cross-section, but only really effective for "thermal neutrons".