radiation + radiation monitoring presentation (online publication)

Review on Ionizing Radiation and Radiation

Monitoring in Low Earth Orbit

“My God, space is radioactive!

- Ernie Ray (1958)

Sample Presentation – Not a finalized document

Modified for Online Distribution

Overview

• Ionizing Radiation

• Dose Terminology

• Earth, High Altitude and Space Radiation Sources

• Biological Effects of Radiation

• Regulations and Standards

2

Overview

• Radiation Monitoring: Space Weather Forecasting

• Radiation Monitoring: Devices

• Biodosimetry Programme

• Non-ionizing Radiation

• Summary

3

4

Ionizing Radiation:

General Information, Dose Terminology

• Defined as particles that have sufficient energy to remove an electron

from an atom or molecule (becoming electrically charged) while also

capable of damaging DNA

• Various types of radiation affects the body in different ways

• ALL radiation exposure (no matter how small) has associated health risks

• Linear No-Threshold Model

• X-rays, gamma-rays, neutrons, protons, electrons and heavy ion particles

are examples of ionizing radiation

5

Ionizing Radiation

6

Ionizing Radiation:

Electromagnetic Spectrum

Non-ionizing Radiation Ionizing Radiation

University of California

Ionizing Radiation (Cont.)

• Can cause severe cell damage (DNA), leading to various forms of cancer

• Radioactive decay of particles may take the form of:

• Beta (β) particles

• β+ = positron

• β- = electron

• Alpha (α) particles – Charged helium nuclei

• Neutrons

• Radioactive sources may include

• Radon-222: naturally occurring α emitter

• Potassium-40: naturally occurring β emitter

• Cobalt-60: used in medical equipment sterilization – emits 2 high energy γ via β decay

• Neutrons: Secondary particle from charged ions interacting with shielding7

Gamma-ray (γ) emission

May lead to

X-ray emission

• Absorbed Dose (D) is a measure of the energy absorbed per unit mass of

material

• Units of Gray (Gy) or rad

• 1 Gy = 100 rad

• All tissue within a radiation beam (i.e. X-ray) will not absorb the same

amount of radiation dose

8

Radiation:

Dose Terminology – Absorbed Dose

• Equivalent Dose (H) relates Radiation Biological Effectiveness (RBE) of

radiation exposure with a Quality Factor (Q)

• Units of Sieverts (Sv) or rem

• 1 Sv = 100 rem

• RBE compares effectiveness of one radiation against gamma radiation

• Value of Q for each radiation type assigned by ICRP 26 and 60

• H = Q * D

9

Radiation:

Dose Terminology – Equivalent Dose

Type of Radiation Quality

Factor

(Q)

Absorbed Dose equal to

1 Equivalent Dose unit

(D = H ÷ Q)*

X-ray, Gamma ray, Beta 1 1

Alpha, Multiple-charge Particles,

Fission Fragments, Heavy Particles

20 0.05

Neutrons 10 0.1

High-energy protons 10 0.1

* Absorbed dose in rad equal to 1 rem or in Gy equal to 1 Sv

10

Radiation:

Quality Factor

11

Radiation:

Dose Terminology

Radiation Quantities and Units (Sprawls, P)

12

Ionizing Radiation Sources:

Earth, High Altitude and Space Environments

Radiation:

Earth Radiation Sources

• Radon gas emissions produce the largest hazard to radiation exposure

on the ground

• Earth’s atmosphere shields against most cosmic radiation

13 World Nuclear Organization (WNO)

Radiation:

High Altitude Exposure

• Jet altitudes ~6.1 km to 18 km

• Exposure from radiation originating from space

• Galactic Cosmic Rays (GCR)

• Solar Particle Events (SPE)

• Annual exposure to flight crews is ~1 to 6 mSv

• GCR and SPE particles interact with atoms in Earth’s atmosphere

creating numerous secondary particles

• Dose from GCR, SPE and secondary particles in correlation to high/low solar

activity

14

Radiation:

Neutron Count Rate and Sunspot Number

15

Neutron count rate and sunspot number plotted against date. Sunspot number per month (indication

of the heliocentric potential); monthly average of the hourly neutron count from the Climax,

Colorado ground-based neutron monitor (Lewis, B. J. et al 2001)

Radiation:

High Altitude Environment

17

Typical cursing altitude of jet aircraft

~6.1 – 18 km above the Earth’s surface

6.1 km

18 km

Cosmic Ray

Protons

Neutrons

Pions

Muons

Photons

Electrons + Positrons

• GCR (and SPE) particles interact

with molecules in the atmosphere

(nitrogen, oxygen, etc.) if they are

not shielded by Earth’s magnetic

field.

• Interaction causes a wide range of

secondary particles which contribute

to the dose in high altitudes (as well

as on the ground).

• Effect of GCRs generally much

greater than SPE

400 km

• SPEs much more

frequent during high

solar activity

• Occasionally, an SPE

can cause a significant

dose at high altitudes

Artwork courtesy of Windows of the Universe

Data from National Oceanic and Atmospheric Administration (NOAA)

18

Radiation:

Space Exposure – Solar Cycle

• Period of solar cycle is

11 years

• Magnetic field polarity

reverses between each

cycle

Radiation:

Space Exposure – Solar Particle Events (SPE)

• Solar flares and Coronal Mass Ejections (CMEs)

• Statistically, most SPE which impact the Earth are not large events

• Consists mainly of p+, but also contains some ions of higher mass

• Unpredictable. Evaluate SPE as they unfold

• Capable of producing radiation levels lethal hours after an event occurs

19

Radiation:

Space Exposure – Solar Particle Events (SPE)

20

Coronal Mass Ejections

Solar Flare

• Radiation that originates from outside the solar system

• Supernova explosions from massive stars

• Solar Cycle dependent

• Highest during Solar Minimum

• Extremely penetrating and biologically damaging

21

Radiation:

Space Exposure – Galactic Cosmic Rays (GCR)

Advanced Composition Explorer (ACE) Website

22

Radiation:

Space Exposure – Cosmic Abundances

• Particles include highly

energetic p+ and heavy ion

(HZE) particles

• 90% protons

• 9% alpha (α) particles – 4He

• 1% HZE particles

• p+ and e- trapped in Earth magnetic field (Van Allen Radiation Belts)

• Inner Belt mostly protons > 10MeV. Reaches ~7700 km from Earth’s Surface

• Outer Belt mostly electrons < 10MeV. Reaches ~51 500 km from Earth’s Surface

• Exposure a function of altitude, inclination and solar cycle position

• Proton exposure highest at Solar Minimum

• e- penetrate EVA suit, but not spacecraft

23

Radiation:

Trapped Particles

SRAG

SRAG

24

Radiation:

Trapped Particles – South Atlantic Anomaly (SAA)

• Region of high radiation exposure

(determined from past missions whose

orbits intersected SAA)

• Result of the offset between Earth’s

geographical and magnetic axes

• Inner Van Allen Belt reaches a

minimum of 200 km above Atlantic

Ocean and South America

• Accounts for approximately 10 – 30% of the dose equivalent received by

astronauts onboard spacecraft in LEO

• Extremely penetrating and can cause cellular damage to internal organs

• Canadian-Russian experiments to characterize neutron field in LEO have

been performed since the late 1980’s

25

Space Radiation Environment:

Neutrons

26


Neutrons

• Originate from charged particles (SPE, GCR and trapped) interacting

with:

1. Spacecraft (spallation/evaporation neutrons): ~20% of total

neutron dose

2. Earth’s atmosphere (albedo neutrons): ~80% of total neutron dose

27


Neutrons

Institut de Recherche sur les Lois Fondamentales de l’Univers

Inner Van Allen Belt

• p+ > 10 MeV, e- ~ 100 keV

• Altitude ~ 7 700 km

• p+ result of neutron decay

(beta decay)

Outer Van Allen Belt

• e- < 10 MeV

• Altitude ~51 500 km

• Trapped by Earth’s magnetosphere

ISS Orbit

Galactic Cosmic Rays (GCR)

• High-energy p+ (90 %)

• α particles (9%)

• Ionized heavier particles – He to U (1 %)

• Originate from outside Solar System

(Supernovae)

• Highest during Solar Minimum

• 100 MeV < Energy < 10 GeV

Solar Particle Events (SPE)

• High-energy p+, α particles, X-

rays

• Highest during Solar Maximum

• Solar Flares

• Coronal Mass Ejections (CME)

• 10 MeV < Energy < 100 MeV

ISS

Secondary Particles

• Protons, neutrons, X-rays, α-particles,

heavy ions (with sufficient energy)

South Atlantic Anomaly (SAA)

• Intersection of Earth’s Atmosphere with Inner belt

• Increased dose when ISS passes through region

• Attitude ~200 km

Rotational

Axis

Magnetic

Axis

29

Radiation:

Space Environment

11.4

30

Ionizing Radiation:

Biological Effects, Regulations and Standards

• Types of radiation risk include:

• Deterministic (Cell death)

• Radiation sickness

• Nausea

• Skin reddening

• Stochastic (Cell Modification)

• Probability of occurrence in

population a function of dose

• Cancer (leukemia, lung,

thyroid)

• Genetic effects

Radiation:

Biological Effects

31

• Acute effects are not expected to result from exposure to the radiation

environments in space, with the exception of SPE

• Major concern about radiation in space is long term effects, such as cancer

or genetic effects

• Risk of acute effects during shuttle or ISS missions is considered to be

minimal

• Increase in cancer risk is the principal concern for astronaut exposure to

space radiation

• Delayed effects (e.g. cancer) can appear months (or years) after exposure. Even the

smallest dose increases the chance of developing this condition

32

Radiation:

Biological Effects (Cont.)

• Ionizing radiation causes atoms and molecules to become excited

(ionized). This can cause:

• Free radicals

• Breaking of original chemical bonds (and forming new bonds)

• Damage to molecules that regulate vital cell process (DNA, RNA, proteins)

• Heavy ion particles are more damaging to vital cells

33

Radiation:


34

Astroprof’s page, Space Radiation and Humans

SRAG

Radiation:


• Particles with a higher linear energy transfer (LET) are more effective in

producing biological effects

• HZE

• Low energy p+

• α-particles

• LET is the amount of energy that is released by radioactive material per

unit length

35 Memorial University

Radiation:


Radiation:

Low-level Acute Radiation Exposure Models

36

• No evidence of adverse health effects

at chronic doses below 100 mSv

• Various models to estimate radiation

risk of low-level radiation exposure• Hypersensitivity – Greater risk at low doses

• Linear No-Threshold – Linear relationship between

radiation exposure and cancer risk

• Threshold – Below certain doses, no cancer risk

• Hormesis – Low doses protective/beneficial

• Known risks represented by data points > 100 mSv

Canadian Nuclear Safety Commission (CNSC)

• Acute (rapid) Wholebody Absorbed Dose

– < 25 rad

• insignificant acute changes

– 25 - 50 rad

• temporary oligospermia

– 50 - 100 rad

• mild nausea in 5 - 30% of population

• mild vomiting in 5 - 20% of population

• anorexia in 15 - 50% of population

• slight decreases in lymphocyte, platelet, and

granulocyte counts--no overt symptoms

– 100 - 200 rad

• mild to moderate nausea in 30 - 70% of

population

• mild to moderate vomiting in 20 - 50%

of population

• slight to moderate decreases in

lymphocyte, platelet, and granulocyte

counts


• mild to moderate fatigue in 30 - 60% of

population

• mild bleeding in 10% of population

• mild to moderate fever/infection in 10-

50% of population

• death in less than 5% of population

Radiation:

Exposure Effects

37

• Acute (rapid) Wholebody Absorbed Dose

– 200 - 350 rad (cont.)

• moderate nausea in 70 - 90% of population

• moderate vomiting in 50 - 80% of population


• moderate diarrhea in ~ 10% of population

• moderate fatigue in 60 - 90% of population

• moderate weakness in 60 - 90% of population

• moderate bleeding in 10 - 50% of population

• moderate infection in 10 - 80% of population

• moderate epilation in 30% of population

• moderate decreases in platelets and granulocytes

• moderate to severe decrease in lymphocytes

• death in 5-50% of population

– > 350 rad

• death to 50% of population in 60 days (LD50/60)

Risk of acute effects during

Shuttle or ISS missions is

considered very minimal!

Radiation:

Exposure Effects (Cont.)

38

Type of Exposure

• Limit: Annual Canadian Public

• Limit: Annual Canadian Radiation Worker

• Average annual exposure to natural background

• Average annual occupational exposure (US) (ground)

• Living one year in Kerala, India

• Airline Flight Crew

• Apollo 14 Highest Skin Dose

• Average Shuttle Skin Dose

• STS 82 Highest Skin Dose

• STS-57 (473 km, 28.5)

• STS-60 (352 km, 57)

• 140 day mission on ISS (400 km, 51.56)• 1 year in deep space (5 g cm-2 Al shielding)

• 1 year deep space (5 g cm-2 polyethylene shielding)

• Mars mission BFO Dose (GCR+SPE: behind 10 g cm-2 shielding) (3-year)

Radiation:

Levels of Exposure – Based on Occupation

Dose Equivalent

1 mSv/y

20 mSv/y

2.94 mSv/y

2.10 mSv/y

13 mSv/y

1-6 mSv/y

14 mSv

~4.33 mSv

76.3 mSv

19.1 mSv

4 mSv

~60 mSv1140 mSv

870 mSv

800 to 2000 mSv

Ground

Air

Space

Regulations and Standards:

30 Day, Annual and Career Exposure Limits

Exposure

Duration

BFO – 5.0 cm

(Sv)

Eye – 0.3 cm

(Sv)

Skin – 0.01 cm

(Sv)

30 Days 0.25 1.00 1.50

Annual 0.05 2.00 3.00

Career 1.00 4.00 6.00

• 30-Day and annual exposure are for protection against deterministic

effects (short term effects)

• Career limit Stochastic effects (fatal cancer)

40

Regulations and Standards:

As Low As Reasonably Achievable (ALARA)

• Involves setting upper limits on the doses received

• Radiation exposures resulting from the practice must be reduced to lowest

levels possible; technological, economic and social issues considered

• Proposed activity that may cause exposure to humans should yield a

sufficient benefit to society to justify the risk

• Understanding and minimizing exposures from space weather events is

an important implementation of ALARA for manned missions

41

42

Radiation Monitoring:

Space Weather Predictions


Pre-, In-, and Post-Flight

• Pre-Flight

• Space radiation exposure assessment performed. Ensure exposures are within limits

(ALARA)

• Inter-Vehicular Activity (IVA) – Activities performed while inside ISS

• Extra-Vehicular Activity (EVA) – Activities performed while outside ISS

(Spacewalk)

• Space environment monitoring

43


Pre-, In-, and Post-Flight

• In-Flight

• Ensure crew limits do not exceed prescribed limits (ALARA)

• Daily support and enhancements

• Post-Flight

• Determine crew exposure and risk

• Biodosimetry analysis

44

Est. 1962ANALYSIS GROUP

JSCN

ASA

SPACE RADIATION


Space Weather – Space Radiation Analysis Group

(SRAG)

• Provides projections for crew exposure

• Maintain comprehensive crew exposure modeling capability

• Radiation instruments to characterize and quantify radiation environment

inside and outside ISS and other spacecraft

• L-4 Months: Complete preliminary EVA exposure analysis

• Forward to Flight Surgeon and Radiation health Officer

• L-5 Weeks: Complete final analysis of EVA exposure from nominal environment

• L-4 Weeks: Report analysis for planned and contingency EVA exposures

45

• In-Flight support

• Provide appropriate alerts and warnings

• Daily space weather reviews and forecasts (via telecon)

• Weekly summaries of forecasts (via email)

• Solar forecasters (24/7 support)

• Classifies solar activity in conjunction with SRAG

46


Space Weather – National Oceanic and

Atmospheric Association (NOAA)

• Receive real-time space environment data from variety of operational

stations, including:

• Satellites

• Geostationary Operational Environmental Satellites (GOES)

• Solar and Heliospheric Observatory (SOHO)

• NOAA/Television Infrared Observation Satellite Program (TIROS)

• Ground stations

• Ground-based solar observations,

• NASA science spacecraft

• United States Air Force (USAF)

47


Space Weather – National Oceanic and

Atmospheric Association (NOAA)

• Solar classification uses a letter system which ranks solar activity by its

peak X-ray activity

• Letter denotes the order of magnitude of the peak value and the number is

the multiplicative factor

The SEC X-ray Flare Classification

Peak Flux Range (0.1 – 0.8 nm)

Classification SI Unit

(W/m2)

CGS Unit

(erg/cm2/s)

A φ < 10-7 φ < 10-4

B 10-7 ≤ φ < 10-6 10-4 ≤ φ < 10-3

C 10-6 ≤ φ < 10-5 10-3 ≤ φ < 10-2

M 10-5 ≤ φ < 10-4 10-2 ≤ φ < 10-1

X 10-4 ≤ φ 10-1 ≤ φ

48 CSA C1 Radiation Monitoring Plan


NOAA – Solar Activity Classification

• Geomagnetic storm – temporary disturbance of Earth’s magnetic field

• Two different classes to describe geomagnetic activity

• A-index: 24 hr average level

• K-index: 3 hr interval

• Quantifying disturbances in horizontal component of Earth’s magnetic field

• Derived from maximum fluctuations of horizontal components observed

Category A-Index K-Index

Quiet 00 ≤ A < 08 Usually no K indices > 2

Unsettled 08 ≤ A < 16 Usually no K indices > 3

Active 16 ≤ A < 30 A few K indices of 4

Minor Storm 30 ≤ A < 50 K indices mostly 4 and 5

Major Storm 50 ≤ A < 100 Some K indices 6 or greater

Severe Storm 100 ≤ A Some K indices 7 or greater

49 CSA C1 Radiation Monitoring Plan


NOAA – Geomagnetic Activity Classification

• X-Ray Flare

• SPE*

• ≥ 10 pfu @ ≥ 10 MeV

• Energetic SPE

• ≥ 1 pfu @ ≥ 100 MeV

• Major Geomagnetic Storm

• AB ≥ 50

• KB = 6

* pfu (proton flux unit)

pfu = particles/sr/cm2/s

• Major X-Ray Flare

• ≥ M5

• Major Integral X-Ray Event

• Flux ≥ 0.3 W/m2

• SPE

• ≥ 10 pfu @ ≥ 10 MeV

• Energetic SPE

• ≥ 1 pfu @ ≥ 100 MeV

• Major Geomagnetic Storm

• AB = 50 – 99

• KB = 6

• Severe Geomagnetic Storm

• AB ≥ 100

• KB ≥ 7

SRAG recall to Mission Control

** Alert product still in development

SRAG remain on console


SRAG and NOAA Warning and Alert Criteria

Watches/Warnings Alerts

50

51


Monitoring Radiation Exposure in

Low Earth Orbit

52 SRAG


Extravehicular Charged Particle Directional

Spectrometer (EV-CPDS)

• 3-axis unit mounted to mast on S0 truss of ISS

• EV1 – Forward along velocity vector (direction of orbit)

• EV2 – Zenith direction (orthogonal to ISS)

• EV3 – Along anti-velocity vector (opposite to EV1)

• Thresholds of measured charged particles

• Proton ≥ 15 MeV

• Electron ≥ 0.5 MeV

• Records dose and dose rate values

53




• Unit insensitive to neutrons

• Measured particle flux as a function of particle energy, charge and arrival

direction

• Trapped

• Secondary

• GCR

• Data sent directly to mission control

54




55SRAG


Intravehicular Charged Particle Directional

Spectrometer (IV-CPDS)

• Identical to single axis EV-CPDS unit

• Portable

• Used to conduct shielding effectiveness surveys

• Not suitable for monitoring important low-energy component of EVA

exposures

56


Intravehicular (Internal) Charged Particle

Directional Spectrometer (IV-CPDS)

57

SRAG


Tissue Equivalent Proportional Counter (TEPC)

• Active system which provides measurements of dose rate and cumulative

dose at 2 or 20 second intervals

• Not suitable for monitoring important low-energy component of EVA

exposures

• Located inside ISS. Moved throughout the station approximately every

month

58



• Time resolved Linear Energy Transfer (LET) spectra

• 0.3 – 1200 keV/m

• Alarm capability when dose rate exceeds 5 mrad/min (50 Gy/min) –

Absorbed dose

• Dose and dose equivalent are stored for future analysis

59



• Thermoluminesent dosimeters (TLDs) placed throughout the ISS

• Dose is determined upon further analysis once the detectors are returned

to Earth

• No record of LET information from charged particles

• Archived measurements are available in

• Absorbed Dose – H2O (mGy)

• Absorbed Dose Rate – H2O (Gy/day)

60Radiation Area Monitor – SRAG


Radiation Area Monitor (RAM) and

NASA Crew Passive Dosimeter (CPD)

• Sensitive to neutrons and charged

particles and records particle impact

angles and LET information

• Consists five different passive

radiation sensors

• Designed to measure total

absorbed dose

61


European CPD (EuCPD)

CSA C1 Radiation Monitoring Plan

•Acquires two sets of data

• Shielded

• Unshielded

• Measurements updated through the SRAG website and can be acquired

for specific dates

62


DB-8 Detectors

CSA C1 Radiation Monitoring PlanCSA C1 Radiation Monitoring Plan

Protection Against Ionizing Radiation onboard ISS

• During periods of higher radiation activity, it is always best to stay in

high shielded areas to reduce exposure

Higher Shielded areas of ISS

• Service Module aft of treadmill (Panel 339)

• Node 2 crew quarters

• US Lab

Lower Shielded areas of ISS

• Service Module crew sleeping compartments

• Service Module transfer compartment (between FGB and Service Module)

• Pressurized mating adapters

• Air locks

• Window in US Lab (WORF)63

Protection Against Ionizing Radiation:

Module Locations

US Destiny Laboratory

Module (US LAB)

Japanese Experiment

Module (JEM/Kibo)

ESA Columbus

Module (COL)

Russian Zvezda

Service Module

64

65

Protection Against Ionizing Radiation:

Particle Interaction with Shielding

MIT Open Courseware

66


Biodosimetry Programme

• Individual responses governed by genetic variability and results in a wide

range of susceptibilities and risks

• A number of tests are performed on the samples including:

• Fluorescent in situ Hybridization (FISH)

• Spectral Karyotyping (SKY)

• Cytokinesis Block Micronucleus (CBMN) Assay

• Dicentric Chromosome Assay

• Protein Profiling

• In addition to the tests listed above, data is also collected from physical

dosimetry devices for comparison.

67


Biodosimetry


Biodosimetry – Fluorescence in situ Hybridization

(FISH)

• An effect of ionizing radiation is when “stable” translocations occur

• Chromosome segments are exchanged, but no genetic information is lost

• These abnormalities are not lethal

• FISH provides a measure of cumulative lifetime dose

• Translocation rates are determined by fluorescently labeling parts of the

genome with part of the segments appearing bi-colored

68


Biodosimetry – Fluorescence in situ Hybridization

(FISH)

69

Health Canada

Health Canada


Biodosimetry – Spectral Karyotyping (SKY)

• Similar to FISH, SKY allows you to visualize all 23 pairs of human

chromosomes at one time

• Differs in the methods it employs to detect and discriminate the different

colour combinations

• Each probe is labeled with a fluorescent molecule that corresponds to the

chromosome to which it is complementary

• Probes complementary to chromosome 1 are labeled yellow, chromosome 2 red, and

so on…

70

71 Health Canada

Health Canada


Biodosimetry – Spectral Karyotyping (SKY)


Biodosimetry – Cytokinesis Block Micronucleus

(CBMN) Assay

• Micronuclei are formed when a complete chromosome or a fragment is

not incorporated into one of the daughter nuclei during cell division

• Proliferating and non-proliferating cells may be distinguished

• Micronuclei are only scored in binucleated cells

• Dose estimation may be correlated to micronucleus frequency

72


Biodosimetry – Cytokinesis Block Micronucleus

(CBMN) Assay

73

Health Canada

Radiation Monitoring

Biodosimetry – Dicentric Chromosome Assay

• Dicentric chromosomes form when two segments (from different

chromosomes) fuse, each with a centromere

• These chromosomes are unstable and so these tests only provides a

measure of DNA damage for the lifetime of the circulating lymphocyte

(type of white blood cell)

• Relatively specific to ionizing radiation

• Low energy radiation does not induce dicentrics

74


Biodosimetry – Dicentric Chromosome Assay

75

Health Canada


Biodosimetry – Protein Profiling

• Refers to quantifying the abundance of individual proteins in a sample

• Known as expression levels

• Current research is interested in identifying biomarkers that could be used

to evaluate an individual’s biological response to radiation exposure

76


Biodosimetry – Dose Response Curve

• Aberrations such as dicentric

chromosomes and translocations

are equally likely outcomes of

radiation exposure

• Individual dose estimates

derived by comparing aberration

rates to calibration curves

established by irradiating pre-

flight samples with known

radiation sources

77

Health Canada

78

Non-Ionizing Radiation

Non-ionizing Radiation

• Consists of the broadband of electromagnetic radiation having

frequencies less than approximately 3 – 1015 Hz, or expressed in

wavelength 108 – 10-7 m

• Far end of the ultraviolet spectrum (10-15 Hz) is considered ionizing

radiation

• Heat generation is consider the main biological effect of non-ionizing

radiation

79

Non-ionizing Radiation:

Biological Effects

80

Ultraviolet

Infrared

Non-Ionizing

Radiations–Sources,

Biological Effects,

Emissions and

Exposures (Ng, K. – N.)

Radiofrequency

Electromagnetic Spectrum

81

Non-ionizing Radiation Ionizing Radiation

University of California

Summary

• Ionizing radiation can cause atoms and molecules to become electrically

charged and damage DNA

• Astronauts are exposed to ionizing radiation on ALL space flights

• Galactic Cosmic Rays (GCR)

• Solar Particle Events (SPE)

• Trapped Particles – Van Allen Radiation Belts

• Secondary Particles

• Low-level radiation exposure follows the Linear No-Threshold Model

• Acute biological effects of space radiation (with the exception of SPE) are

not expected to result from radiation exposure in space.

82

Summary

• Radiation exposure can result in an increased risk in cancer (stochastic

effects)

• Those who are exposed to radiation in LEO receive a dose from various

types of radiation sources (neutrons, protons, gamma-rays, etc).

• Ionizing radiation exposure can leave distinct markers in the blood

samples taken from individuals who have been exposed

83

Summary

84

• Further studies will be conducted in order to characterize neutron

radiation field during ISS-34/35 during the Radi-N2 study

• The ALARA protocol is followed at ALL TIMES

• Astronauts are asked to wear the their CPDs to monitor their dose at ALL

TIMES

85

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