Radiation Shielding

[Yansuf]

Yesterday I asked the following question:

 

"Radiation Shielding

In 6E2 pg 155, the multiplier for dense atmosphere is given as 0.9/meter.

This is the same as is given for thin atmosphere. This appears to be a typo.

What is the correct value?"

 

Steve Long replied:

 

"Re: Radiation Shielding

As far as I can recall the table is correct as listed. I'm not going to take the time to try to dig out my notes, but I recall being surprised myself at the fact that they were equal."

 

 

Anyone care to comment?

[Hyper-Man]

Re: Radiation Shielding

 

I'm not familiar with the table but I'll hazard a guess that the radiation in question is that from our sun. If so, isn't most of the shielding provided by the Earth's magnetic field and then the ozone layer?

 

So this begs the question: Is it just an urban legend that airline passengers flying above the cloud layer get the same radiation exposure as an x-ray machine?

[Ockham's Spoon]

Re: Radiation Shielding

 

Radiation is a really vague term because there are so many types. For some types of radiation a little bit of atmosphere (or planet) means nothing, for others it is effectively a brick wall. It may also depend on the composition of the atmosphere (e.g. is there an ozone layer or not?).

 

From a gaming standpoint, if you want to make radiation an environmental hazard, just say that the radiation in the area isn't affected by the atmosphere. If you don't want to mess with that extra compliation in a particular scenario, just assume that the atmosphere makes a pretty good shield.

[Cancer]

Re: Radiation Shielding

 

Atmospheric attenuation of radiation depends on what sort of radiation it is (how energetic the photons are), and what the difference is between "thick atmosphere" and "thin atmosphere".

 

For gamma rays, I'd be willing to believe that sea level air doesn't do much better than air at 10,000 feet of altitude, at least at the HERO scaling level.

[Yansuf]

Re: Radiation Shielding

 

The table in question is:

 

RADIATION SHIElDING

Substance Radiation Multiplier

Atmosphere

Standard (per meter) .75

Thin (per meter) .9

Trace (per meter) .98

Dense (per meter) .9

Brick (per cm) .75

Lead (per mm) .8

Radiation Suit .7

Rock (per cm) .75

Soil (per cm) .75

Spacesuit .9

Steel (per mm) .9

Vehicle Hull (per point of PD) .9

Water (per cm) .9

Wood or Plastic (per cm) .95

 

Concentrating on the "Atmosphere" portion, I maintain that it is flat out wrong.

Anyone here who agrees with Mr. Long that it is not?

[JavalTigar]

Re: Radiation Shielding

 

Well in the real world as a Navy Nuclear Engineer, the mantra was Time - Distance - Shielding.

How long exposed to the source, how far away from the source, and what is between you and the source.

 

From the list you can see that heavy dense material is your friend. That's why there was lead, concrete and water around our reactor core. On the other hand, air is a very light and sparce material. Insulates for heat well since there are not a lot of particles to rub together. But that is exactly the reason that it sucks for radiation.

 

Think of radiation as fast moving projectiles not unlike bullets. Would you want to hide behind a brick wall or a rice paper wall? It might seem wierd that atmosphere doesn't stop much but remember there is 62 MILES of air and 8 light minutes of distance between the sun and us. So to put that into my bullet analogy, it would be 50 meters of rice paper and the bullet was fired from 1 mile off.

 

I hope this helps clear up the confusion.

[Ice9]

Re: Radiation Shielding

 

That does seem odd that dense atmosphere would provide less shielding than standard atmosphere. I could see them being the same, but less?

[IndianaJoe3]

Re: Radiation Shielding

 

That does seem odd that dense atmosphere would provide less shielding than standard atmosphere. I could see them being the same' date=' but less?[/quote']

 

I think there are problems with secondary radiation.

[Ockham's Spoon]

Re: Radiation Shielding

 

The numbers look intuitively inconsistent, but I don't know where Steve found them. They might be perfectly correct, but from different sources for different forms of radiation or for different atmospheric compositions. Safe to say that the GM has a lot of latitude in determining the relative radiation danger in any given location, so he can basically do what is deemed appropriate for the venue.