Radiation shielding - Revision history

RichardWSmith: /* General */ Made sentence more correct / clearer.

2025-11-18T02:14:39Z

General: Made sentence more correct / clearer.

RichardWSmith: /* General */ Adding a link.

2025-11-18T02:12:45Z

General: Adding a link.

RichardWSmith: /* Protection from Electromagnetic Radiation */

2025-05-26T10:21:03Z

Protection from Electromagnetic Radiation

RichardWSmith: /* Protection from Electromagnetic Radiation */

2025-05-26T09:40:26Z

Protection from Electromagnetic Radiation

RichardWSmith: /* Protection from Electromagnetic Radiation */ Added reference.

2025-05-26T09:09:47Z

Protection from Electromagnetic Radiation: Added reference.

RichardWSmith: /* Protection from Electromagnetic Radiation */ Adding wood.

2025-05-26T08:32:22Z

Protection from Electromagnetic Radiation: Adding wood.

Michel Lamontagne: /* General */

2024-12-28T20:37:17Z

General

RichardWSmith: /* Risk-mitigating behaviour */ Added link

2024-11-01T18:17:30Z

Risk-mitigating behaviour: Added link

RichardWSmith: /* Types of radiation shielding and risk to tissue */ Added link.

2024-10-31T21:30:33Z

Types of radiation shielding and risk to tissue: Added link.

RichardWSmith: /* Types of radiation shielding and risk to tissue */

2024-10-31T08:24:45Z

Types of radiation shielding and risk to tissue

@@ Line 11: / Line 11: @@
 Note that there is significant evidence that very low levels of radiation is healthy.  See [[Radiation Hormesis]].
-Long term settlers will need to shield against 3 types of radiation: [[Electromagnetic radiation]], [[Solar Cosmic Rays]], and more powerful [[Cosmic radiation | Cosmic Rays]].  Of the last, [[Galactic Cosmic Rays]] are by far the most common fraction of these.
+Long term settlers will need to shield against 3 types of radiation: [[Electromagnetic radiation]], [[Solar Cosmic Rays]], and more powerful [[Cosmic radiation | Cosmic Rays]].  [[Galactic Cosmic Rays]] are by far the most difficult to shield against (tho their total energy dosage is low).
 ===Electromagnetic Radiation===

← Older revision		Revision as of 02:12, 18 November 2025
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	Also note that sudden radiation doses are much more dangerous than a small steady dose over a long period of time. A solar storm is FAR more dangerous than the slow and steady trickle of cosmic rays.		Also note that sudden radiation doses are much more dangerous than a small steady dose over a long period of time. A solar storm is FAR more dangerous than the slow and steady trickle of cosmic rays.
		+
		+	Note that there is significant evidence that very low levels of radiation is healthy. See [[Radiation Hormesis]].

	Long term settlers will need to shield against 3 types of radiation: [[Electromagnetic radiation]], [[Solar Cosmic Rays]], and more powerful [[Cosmic radiation \| Cosmic Rays]]. Of the last, [[Galactic Cosmic Rays]] are by far the most common fraction of these.		Long term settlers will need to shield against 3 types of radiation: [[Electromagnetic radiation]], [[Solar Cosmic Rays]], and more powerful [[Cosmic radiation \| Cosmic Rays]]. Of the last, [[Galactic Cosmic Rays]] are by far the most common fraction of these.

@@ Line 147: / Line 147: @@
 |}
-'* Wood varies by species and water content (wet wood is better), but the values given are typical.  [[Superwood]] is 5 times denser, but has less water in it, so the wood value was multiplied by 4 as a conservative estimate.  Wood and superwood provide excellent alpha and beta protection, and the large number of light atoms will help stop secondary radiation and albedo neutrons.
+'* Wood varies by species (hard woods are better) and water content (wet wood is better), but the values given are typical.  [[Superwood]] is 5 times denser, but has less water in it, so the wood value was multiplied by 4 as a conservative estimate.  Wood and superwood provide excellent alpha and beta protection, and the large number of light atoms will help stop secondary radiation and albedo neutrons.
 The linear attenuation coefficient µ is not commonly found in the literature, the mass attenuation coefficient µ<sub>m</sub> is usually used instead.  The coefficient is also dependent on the type of radiation, so a complete solution  for radiation protection requires multiple analysis of the type of radiation to be protected against.
@@ Line 207: / Line 207: @@
 |0.42
 |}
-'* The radiation protection of wood varies by species and water content (more water is good).  These are typical values.  Superwood is 5 times the density, so the Wood values would be 1/4 to 1/5.<ref>https://www.sciencedirect.com/science/article/abs/pii/S0969806X21005776</ref>
+'* The radiation protection of wood varies by species (hard woods are better) and water content (more water is good).  These are typical values.<ref>https://www.sciencedirect.com/science/article/abs/pii/S0969806X21005776</ref>  Superwood is 5 times the density, so the Wood values would be 1/4 to 1/5.
 The first point to note is that the Half Value Layer decreases as the atomic number increases.  For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.

@@ Line 147: / Line 147: @@
 |}
-* Wood varies by species and water content (wet wood is better), but the values given are typical.  [[Superwood]] is 5 times denser, but has less water in it, so the wood value was multiplied by 4 as a conservative estimate.  Wood and superwood provide excellent alpha and beta protection, and the large number of light atoms will help stop secondary radiation and albedo neutrons.
+'* Wood varies by species and water content (wet wood is better), but the values given are typical.  [[Superwood]] is 5 times denser, but has less water in it, so the wood value was multiplied by 4 as a conservative estimate.  Wood and superwood provide excellent alpha and beta protection, and the large number of light atoms will help stop secondary radiation and albedo neutrons.
 The linear attenuation coefficient µ is not commonly found in the literature, the mass attenuation coefficient µ<sub>m</sub> is usually used instead.  The coefficient is also dependent on the type of radiation, so a complete solution  for radiation protection requires multiple analysis of the type of radiation to be protected against.
@@ Line 183: / Line 183: @@
 |-
 |'''Wood*'''
-|16.0
+|17.0
-|19.5
+|20.5
-|27.5
+|28.5
 |-
 |'''Aluminium'''
@@ Line 207: / Line 207: @@
 |0.42
 |}
-* The radiation protection of wood varies by species and water content (more water is good).  These are typical values.  Superwood is 5 times the density, so the Wood values would be 1/4 to 1/5.<ref>https://www.sciencedirect.com/science/article/abs/pii/S0969806X21005776</ref>
+'* The radiation protection of wood varies by species and water content (more water is good).  These are typical values.  Superwood is 5 times the density, so the Wood values would be 1/4 to 1/5.<ref>https://www.sciencedirect.com/science/article/abs/pii/S0969806X21005776</ref>
 The first point to note is that the Half Value Layer decreases as the atomic number increases.  For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.

@@ Line 116: / Line 116: @@
 |0.196
 |-
-|'''2 cm of wood'''
+|'''Wood *'''
-|0.?
+|0.60
-|0.?
+|0.20
-|0.?
+|0.08
 |-
 |'''Aluminium'''
@@ Line 142: / Line 147: @@
 |}
-the linear attenuation coefficient µ is not commonly found in the literature, the mass attenuation coefficient µ<sub>m</sub> is usually used instead.  The coefficient is also dependent on the type of radiation, so a complete solution  for radiation protection requires multiple analysis of the type of radiation to be protected against.
+* Wood varies by species and water content (wet wood is better), but the values given are typical.  [[Superwood]] is 5 times denser, but has less water in it, so the wood value was multiplied by 4 as a conservative estimate.  Wood and superwood provide excellent alpha and beta protection, and the large number of light atoms will help stop secondary radiation and albedo neutrons.
 Conversion is quite simple as:
@@ Line 174: / Line 181: @@
 |2.53
 |3.54
 |-
 |'''Aluminium'''
@@ Line 195: / Line 207: @@
 |0.42
 |}
 The first point to note is that the Half Value Layer decreases as the atomic number increases.  For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.

@@ Line 115: / Line 115: @@
 |0.274
 |0.196
 |-
 |'''Aluminium'''
@@ Line 192: / Line 197: @@
 The first point to note is that the Half Value Layer decreases as the atomic number increases.  For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.
 Also note that this table is for gamma rays.  Gamma rays in the kilo-electron volt ranger are not the big problem. Giga-electron volt cosmic rays are.
 ===Protection from Particulate Radiation===

@@ Line 5: / Line 5: @@
 ==General==
-The average radiation on Earth is very low at ~6.2 mSv / year.  However, in some areas of the city Ramsar, Iran, the radiation level is 260 mSv / year, with no increase in health problems.  Thus the radiation safety levels in many countries on Earth, are likely too conservative.  This is good news for Mars colonists, our goal is not 6.2 mSv per year, but say 200 to 250 mSv / year.  The discussion below assumes we are aiming for 6.2 mSv, but there shouldn't be a disaster if this is missed, even by a significant amount.
+The average radiation on Earth is very low at 3 to 6.2 mSv / year depending on location (https://en.wikipedia.org/wiki/Background_radiation).  However, in some areas of the city Ramsar, Iran, the radiation level is 260 mSv / year, with no measured increase in health problems.  Thus the radiation safety levels in many countries on Earth may be too conservative.  Mars starts at 200 to 250 mSv / year.  The discussion below assumes we are aiming for 6.2 mSv, but there shouldn't be a disaster if this is missed, even by a significant amount.
 Also note that sudden radiation doses are much more dangerous than a small steady dose over a long period of time.  A solar storm is FAR more dangerous than the slow and steady trickle of cosmic rays.

@@ Line 304: / Line 304: @@
 The possible sources of radiation on Mars are man-made sources, (such as nuclear reactors or medical equipment), [[solar radiation]], [[galactic cosmic radiation]] and naturally occurring [[radioactive elements]] on Mars.
-Living in a deep lava tube takes care of the problem.  However many sites on Mars do not have these.  For those areas...
+Living in a deep [[Lava tube]] takes care of the problem.  However many sites on Mars do not have these.  For those areas...
 Possible behavioral choices which minimize the risk from these include:

@@ Line 297: / Line 297: @@
 |}
-Note that small particles about the same mass of a proton or helium nucleus, are best slowed down by bouncing off of other small atoms.  (As much energy as possible is removed by kinetic energy of the atom it bumps into.) Where as gamma rays, and heavy nucleus want dense matter, or metals to stop them.  However, cosmic rays with obscene amounts of energy will break into [[Secondary radiation]] when hitting dense matter, and the secondary radiation is more dangerous than the cosmic rays themselves.  Finally, cosmic rays can create free neutrons, which we want to slow with light atoms.
+Note that small particles about the same mass of a proton or helium nucleus, are best slowed down by bouncing off of other small atoms.  (As much energy as possible is removed by kinetic energy of the atom it bumps into.) Where as gamma rays, and heavy nucleus want dense matter, or metals to stop them.  However, cosmic rays with obscene amounts of energy will break into [[Secondary radiation]] when hitting dense matter, and the secondary radiation is more dangerous than the cosmic rays themselves.  Finally, cosmic rays can create free neutrons, which we want to slow with light atoms.  See [[Radiation sickness]] for more information on these weighting factors.
 So ideal radiation protection might have a couple meters (or more) or soil, then a metal wall a few cm thick, then some material with small atoms like water, plastic, or lithium hydroxide (LiOH).  A storm shelter is similar, but might have 5 to 8 meters of soil.

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 ==Types of radiation shielding and risk to tissue==
 {| class="wikitable" style="margin:auto"
-|+ Radiation Weighting Factors
+|+ Radiation Weighting Factors & Best Shielding Materials
 |-
 ! Type of Radiation !! Tissue Weighting Factor !! Ideal Shielding Material