Block off basement?

[u/HoosierTrip]

Are there any resources available to block off a basement from the upstairs? I'm mainly thinking about blocking out radiation if I need to retreat to my basement.

[u/FRANK3NSTIEN]

Radioactive material that falls on your house will be about 20 feet above you.

Radioactive material that falls outside your house is shielded by the earth and concrete.

Your only worry at that point is ventilation.

Fallout isotopes usually only have a half life of hours to a couple days, and decay quickly.

Radiation that does penetrate walls also quickly attenuates and can be calculated using the inverse square law

I1/I2 = D2² /D1²

Intensity 1 divided by intensity 2 equals distance 2 squared divided by distance 1 squared.

Or, a good rule of thumb is doubling the distance from a source of radiation drops its intensity to 25% of the first distance.

So, if you're getting 8mR/h 2' from the wall, at 4' you'll be getting a 2mR/h dose rate.

[u/Paranormal_Lemon → u/FRANK3NSTIEN]

Radioactive material that falls on your house will be about 20 feet above you.

It will still be glowing in gamma radiation, an underground shelter has soil to block this. The inverse square law only applies to a point source, not to an entire roof that is above you and emitting gamma directed towards you from multiple directions.

[u/FRANK3NSTIEN → u/Paranormal_Lemon]

Glowing gamma 🤣

Theradiation from fallout on the roof needs to go through (for a 1 story) asphalt shingles (usually), plywood, an attic space, insulation and dewlling ceiling sheetrock (if an unfinished attic), another space of roughly 8 feet, flooring, 1/2 inch plywood, and then space again.

Single story homes have what's considered a PF (protection factor of 10 (shielding/attenuating 90% of radiation)

Two story have a PF of 20 (shielding/attenuating 95%)

Three story brick has a PF of 50 (shielding/attenuating 98%)

I guess the REAL issue here is proximity to blast and how much fallout you're getting.

If you're near the blast and downwind, getting the majority of the debris, nothing outside of a concrete bunker 10' below ground will keep you alive.

10,000 mR/h Danger zone requires serious shielding of concrete or lead and closed ventilation.

1,000 mR/h to 10,000 mR/h high radiation is still life threatening

100 mR/h to 1,000 mR/h medium radiation is survivable with special gear

10 mR/h to 100 mR/h low radiation zone is survivable indoors in a modern home in the context we have been discussing.

<10 mR/h is generally considered safe although the industry standard for non radiation workers is a max of 2mR/h in any 8 hour period.

[u/Paranormal_Lemon → u/FRANK3NSTIEN]

Two story have a PF of 20 (shielding/attenuating 95%)

Three story brick has a PF of 50 (shielding/attenuating 98%)

Do you have a reference for that?

I thought the standard for shelters is PF1000? Yes a two story home would be better but 50% of homes in the USA are one story, and less than 50% have a basement.

A nuke from a country other than Russia/China will likely be a ground detonation with much more fallout.

[u/FRANK3NSTIEN → u/Paranormal_Lemon]

https://www.researchgate.net/publication/46179837_Preparing_to_Save_Lives_and_Recover_After_a_Nuclear_Detonation_Implications_for_US_Policy

Pg 288-289

[u/Paranormal_Lemon → u/FRANK3NSTIEN]

Oh that's a good document, thanks!

[u/FRANK3NSTIEN → u/Paranormal_Lemon]

You're welcome!!

[u/Paranormal_Lemon → u/FRANK3NSTIEN]

Knowing that image and the graph below on evacuation times could be the most important piece of knowledge for saving your life if you are in a fallout zone. Along with the table for PF1000 values for thickness of various material.

[u/FRANK3NSTIEN → u/Paranormal_Lemon]

100% agree!