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Radiation, Radon, Nuclear Power,
and Radiation Terror
Jonathan M. Links, PhD
Johns Hopkins University
Section A
Radiation
An Atom
a electron
b proton
c neutron
a
b
c
4
Radiation
„
„
Ionizing radiation is radiation with sufficient energy to eject
electrons from atoms; this process is called ionization
Non-ionizing radiation is radiation without sufficient energy
to produce ionization
5
Types of Radiation
„
„
Electromagnetic radiation
− UV, visible light, x-rays, EMFs: Electric field and magnetic
field traveling at right angles; no mass, no charge
Particulate radiation
− Alpha particle, beta particle, neutrons: Have mass and
(alphas and betas) charge
6
Types of Radiation
„
„
Ionizing radiation (~>14 eV)
− Particulate: Alpha (2p + 2n), beta (e-), positron (e+)
− Electromagnetic: X-rays, gamma rays
Non-ionizing radiation (~<14 eV)
− Electromagnetic: UV, microwaves, EMFs
7
Sources of Radiation Exposure: Natural
„
Natural sources are those of natural origin that are
unperturbed by human activities and those of natural origin
affected by human activities (enhanced natural sources)
− Examples include the sun (UV and cosmic x-rays) and the
soil (radon)
8
Sources of Radiation Exposure: Man-Made
„
Man-made sources are those specifically produced by man
− Examples include medical devices, consumer products,
and nuclear power plants
9
Ultraviolet Light
„
„
Ultraviolet light spans the gap between ionizing and nonionizing radiation
The sun is a major source of ultraviolet light, but sunlamps
and arc welding are also sources
10
Types of Ultraviolet Light
„
„
„
UV-A (315–400 nm)
− Tanning, skin cancer (?)
UV-B (280–315 nm)
− Sunburn, skin cancer, cataracts, immune suppression
UV-C (100–280 nm): DNA damage
− Basal cell carcinoma: Doesn’t usually metastasize
− Squamous cell carcinoma: Metastasizes to regional
lymph nodes
− Malignant melanomas: Rapid overall metastasis
11
Extremely Low-Frequency EMFs
„
„
1–3,000 Hz (cycles per second)
− High-voltage transmission lines, lower voltage distributor
lines, radar and communication equipment, electric
blankets
EMFs probably impact biological systems by interfering with
bio-electric processes at the molecular level—not by direct
heat, chemical bond breakage, or ion formation
12
Extremely Low-Frequency EMFs
„
„
„
No evidence of direct DNA damage, but EMFs produce
changes in DNA synthesis and RNA transcription
ELF EMFs are possibly carcinogenic to humans (NIEHS
Working Group, June 1998)
Public health approach
− “Prudent avoidance”
− ALARA—as low as reasonably achievable
13
The Precautionary Principle
„
„
„
„
Taking preventive action in the face of uncertainty
Shifting the burden of proof to the proponents of an activity
Exploring a wide range of alternatives to possibly harmful
actions
Increasing public participation in decision making
Source: 1992 Rio Declaration; Kriebel and Tickner. (September 2001). Reenergizing public health through precaution.
American Journal of Public Health, 91, 9, 1351–1355.
14
Ionizing Radiation Exposure
Average annual effective dose
equivalent (U.S.) from natural
sources in thousandths of a
rem (mrem)
Annual dose from all sources
(percentage from each)
Radon—200 mrem
In the body—39 mrem
Terrestrial—28 mrem
Cosmic—27 mrem
Radon—55%
In the body—11%
Terrestrial—8%
Cosmic—8%
Medical—15%
Products—3%
Other—1%
15
Ionizing Radiation and Cancer Causation
„
„
„
Leukemia
− Cancers in A-bomb survivors
− Patients irradiated for ankylosing spondylitis
Thyroid cancer
− Children irradiated for enlarged thymus
− Children irradiated for tinea capitis
Lung cancer
− Pitchblende miners
16
Ionizing Radiation and Cancer Causation (cont.)
„
„
„
Bone tumors
− Radium dial painters
Liver tumors
− Patients who received thorotrast
− Children irradiated for tinea capitis
Skin cancer
− X-ray workers
17
Mechanisms for Radiation Carcinogenesis
Ionizing radiation
Cell damage
Cell death
– Radiation target = DNA
– M (mitosis) phase is most
sensitive
– S (synthesis) phase is least
sensitive
Repair
Altered
function
18
What Cells Are Most Radiation-Sensitive?
„
Radiosensitive cells that are undergoing rapid cell division
− More frequently in the mitosis phase
− Less differentiated
− Less likely to have repair mechanisms
19
Radiation Risk Models: Absolute Risk Model
„
Absolute risk model
− Assumes that radiation produces a discrete “crop” of
cancers over and above the spontaneous level and
unrelated to the spontaneous level
20
Radiation Risk Models: Relative Risk Model
„
Relative risk model
− Assumes that radiation increases the spontaneous
incidence by a factor
− Because natural cancer incidence is a function of age, this
model assumes increasing excess cancers with increasing
age
21
Absolute Risk Model
22
Relative Risk Model
23
Radiation Carcinogenesis Risk Estimates
„
Most commonly accepted risk estimates (BEIR V, National
Academy of Sciences, 1990) are based on a relative risk
model, with excess cancer mortality dependent on dose,
dose2, age at exposure, time since exposure, and gender
24
Radiation Carcinogenesis Risk Estimates
„
„
For solid tumors, excess mortality is a linear function of dose
Leukemia is a linear-quadratic function of dose
25
Section B
Nuclear Power and Radioactive Waste Disposal
Comparison: Fossil Fuel and Nuclear Power Plants
Source: Adapted by CTLT from Botkin, D. B.
27
Pressurized Water Nuclear Reactor (Three Mile Island)
28
Three Mile Island: March 28, 1979
„
Unit 2: Pressurized-water reactor
− Feedwater pumps shut down
− Pressure relief valve opened and then stuck open
− Loss-of-coolant accident (LOCA)
− Emergency feedwater valves were closed
X Operator did not notice relevant annunciator lights
29
Three Mile Island: March 28, 1979 (cont.)
„
Unit 2: Pressurized-water reactor
− High-pressure injection pumps began automatically
operating, but 30 seconds later, operator shut one pump
down and reduced the flow in the second
− Operators then drained additional water
− Core temperature rose to point where partial melting
occurred and steam bubbles and hydrogen gas formed
− Finally, loss of coolant recognized and stopped
(6.5 hours into the accident)
30
Chernobyl: April 26, 1986
„
Unit 4: Russian RBMK design (boiling water)
− Routine shutdown to conduct experiment of the ability of
the turbines to produce electricity in the event of
interruption of steam supply
− Reduction of reactor power to too-low level
− Intentional disconnection of emergency core cooling
system
31
Chernobyl: April 26, 1986 (cont.)
„
Unit 4: Russian RBMK design (boiling water)
− Loss of reactor control (i.e., ability to stabilize heat and
power output)
− Operators took several actions over 30 seconds to
increase power
− Power increased sharply
− Two explosions and 30 fires, which destroyed the unit
and scattered the core
− Finally, firefighting brought immediate site under control
32
Chernobyl Fallout
„
„
„
„
„
Released ~ 185–200 million Ci (curies)
31 died as a result of the explosion and release of radiation
~ 5,000–7,000 died as result of the cleanup operation
~ 100,000 evacuated (living within 30 km)
~ 40,000–70,000 cancer deaths may result over the next
several decades (also outside former Soviet countries)
Source: McKinney, M. L.
33
Chernobyl Fallout
„
„
„
„
„
„
„
„
Released ~ 185–200 million Ci (curies)
31 died as a result of the explosion and release of radiation
~ 5,000–7,000 died as result of the cleanup operation
~ 100,000 evacuated (living within 30 km)
~ 40,000–70,000 cancer deaths may result over the next
several decades (also outside former Soviet countries)
In Ukraine, proximity to reactor
− Close: Vegetation and trees died
− Further: Humans with weakened immune systems,
animals with deformities
~ 10,000 km2 contaminated at a level of 15 Ci or higher/km2
627,000 Soviets under permanent observation
Source: McKinney, M. L.
34
Chernobyl Fallout
„
„
Direct financial cost: ~ $13 billion
Indirect costs: What are the costs of birth defects and
chromosomal abnormalities that appear generations later?
Source: McKinney, M. L.
35
Radioactive Waste Generated Annually, U.S.
Category
Type
Amount
Spent fuel
Fuel removed from commercial
reactors
2,100 tons
High-level
Highly radioactive—from fuel
processing
2,500 yd3
Low-level
Any waste not in the other
categories
150,000 yd3
Uranium mill
tailings
Residues and waste after
uranium mining and extraction
from ores
470,000 yd3
Source: Wagner, T.
36
Estimated Amounts of Radioactive Waste, U.S.—1991
Amount
generated per
year
National
inventory
Total
radioactivity
Spent fuel
2,100 tons
26,100 tons
(12,500 yd3)
23.3 billion Ci
High-level
2,500 yd3
903,000 yd3
1 billion Ci
Low-level
150,000 yd3
5,500,000 yd3
19 million Ci
Uranium mill
tailings
470,000 yd3
155,000,000 yd3
Unknown
Waste type
Source: Wagner, T.
37
High-Level Radioactive Waste Disposal
„
„
„
Permanent disposal system not fully developed
Generally stored “temporarily” on-site in pools of water
Disposal involves complex technical, political, and social
issues
− Must be perfectly contained (toxicity)
− Guarded for a very long time span (long half-life)
38
High-Level Radioactive Waste Disposal (cont.)
−
„
Secured as contains fissionable material (uranium or
plutonium) necessary for nuclear weapons
− Difficulties transporting to permanent site
Geologic disposal
− Isolate nuclear waste in a stable rock formation 1,000 feet
underground
− Barriers: Form of waste, fuel cladding, waste container,
rock
39
High-Level Radioactive Waste Disposal (cont.)
„
„
Sub-sea bed disposal
− Isolate nuclear waste in deep-sea sediments 3,000–5,000
meters deep
Other alternatives
− Bury in Antarctic ice sheet
− Send into space
− Keep in large water pool
40
Section C
Radon
Radon
„
„
„
„
„
Noble gas
Radioactive
Gives rise to progeny that are themselves radioactive
Some of these progeny have short half-lives and decay by
alpha decay
These progeny deposit in the lung
42
Three Types of Ionizing Radiation
„
Three types of ionizing radiation and their penetrating power
Source: Adapted by CTLT from UNEP.
43
Radon
„
„
„
Alphas lose all their energy over a short distance; they thus
have a short “range” in tissue (~ 2–4 cell diameters)
If a radioactive atom decays in the airways by alpha decay,
the alpha particle will give a very high dose to radiosensitive
epithelial stem cells
The alphas emitted by radon progeny are thus particularly
“dangerous”
44
Subdivisions of the Conducting Airways
Schematic
representation
for the subdivisions of
the conducting airways
and terminal
respiratory units
Source: Adapted by CTLT from Murray.
45
Particle Size and Deposition within the Respiratory Tract
Particle sizes for
common air
pollutants and
the sites of their
deposition within
the respiratory
tract (assuming a
respiratory rate of
15/min and a tidal
volume of 750 ml)
Source: Adapted by CTLT from Blumental, D. S.
46
Three Mechanisms of Aerosol Particle Deposition
„
Schematic representation of the three main mechanisms of
aerosol particle deposition
47
Particle Deposition in the Lung
Particle size
Respiratory rate
Deposition
process
Deposition site
Coarse
High
Impaction
Large airways
Coarse
Low
Sedimentation
Large and smaller
airways
Fine
High
Diffusion
Large and smaller
airways
Fine
Low
Diffusion
Alveoli
48
Radon Progeny Distribution in the Lung
„
„
Attached vs. unattached
− Attached distribute as air particles
− Unattached diffuse to lung periphery
Air particles
− Mining environment = coarse
− Home environment = fine
49
Points Where Radon Can Enter Homes
Source: Adapted by CTLT from Nadakavukaren, A.
50
Radon Reduction Methods
Source: Adapted by CTLT from Nadakavukaren, A.
51
Respiratory Cancer and Radon
Source: Adapted by CTLT from Archer, Gillam, Wagoner. (1976). Annals of the New York Academy of Sciences, 271.
52
Section D
Radiation in Terrorist Activities
Irradiation for Sterilization
„
„
„
„
Utilizes ionizing radiation to kill cells
Ionizing radiation can be particulate (e.g., electrons) or
electromagnetic (e.g., x-rays or gamma rays)
Ionizing radiation comes from either radioactive sources or
machines
Degree of sterilization (fraction of cells killed) depends on the
radiation dose (measured in rads or grays)
54
Radioactive Sources
„
Radioisotopes are unstable and emit radiation (in the form of
gamma rays) as they disintegrate or decay to a stable state
− Cobalt-60 or cesium-137 radionuclides
− The market is dominated by Co-60 sources (emit 1 MeV
photons)
55
Facility for Food Irradiation
56
Radiation Machines
„
„
„
Electron accelerators are a source of high-energy radiation
that use no radioactive materials
Accelerators produce 10 MeV electrons
− Penetration is limited compared to gamma rays from
Co-60 or Cs-137
Electrons can be converted to more-penetrating x-rays
− Conversion efficiency is low
57
With Electrons It’s Critical to Dose All Material
58
Radiation Facility Locations
59
Pros and Cons of Sources and Radiations
„
„
Radioactive source vs. machine
− Source is always “active”; machine can be turned on and
off
− Source produces gamma rays (like x-rays); machine can
produce either electrons or x-rays
Electrons vs. x-rays or gamma rays
− Electrons deliver a large dose near the surface; x-rays are
more penetrating (for thicker packages)
− Gamma rays from radioactive sources are widely
available; x-rays from machines are relatively inefficient to
produce
60
Food Irradiation
Food
Approved use
Dose
(kGy)
Spices and dry
vegetable seasoning
Decontaminating and
controlling insects and
microorganisms
30
Dry or dehydrated
enzyme preparations
Controlling insects and microorganisms
10
All foods
Controlling insects
1
Fresh foods
Delaying maturation
1
Poultry
Controlling disease-causing
microorganisms
3
Controlling spoilage and
Red meat (such as beef,
disease-causing microlamb, and pork)
organisms
4.5 (fresh)
7 (frozen)
Source: FDA. (May–June 1998). Irradiation: A safe measure for safer food. Publication number 98-2320.
61
Anthrax Inactivation
„
„
„
„
LD50 for inhalation anthrax is ≈ 8,000–10,000 spores
Desired fractional sterilization depends on starting number of
spores (assume 1013 spores)
Goal: 14 log reduction in spores; Armed Forces Radiobiology
Research Institute (AFRRI) dose estimate: 56 kGy
10 MeV electrons; 2-sided irradiation; 4” maximum mail
height
62
Irradiation of Larger Packages
„
„
„
3 MCi Co-60 or 5 MeV bremsstrahlung
8–12% electron-to-x-ray conversion efficiency
Segregate mail from known suppliers (e.g., pharmaceutical
companies and packaged food suppliers) and do not irradiate
63
Radiation Damage with High-Dose Irradiation
„
„
Radiolysis—changes in chemical composition (“unidentified
radiolytic products”—URPs)
Heating—charring, burning, “cooking”
64
Radiation Safety Issues
„
„
„
General public
− Irradiation does not make material radioactive
− Foods and drugs may be altered
General postal workers
− No new risks
Workers associated with irradiation
− Direct beam irradiation—highly unlikely
− Scattered radiation—depends on shielding
65
Use of Radioactivity or Radiation in Terrorist Activities
„
„
Bomb or other overt (explosive) attack
Air or water poisoning
66
Bomb-Type Attack
„
„
„
„
„
Nuclear device
Dirty bomb (“radiological dispersal device”)
Attack on fixed nuclear facility (nuclear reactor, spent fuel
storage depot, nuclear fuel reprocessing facilities, high-level
waste site)
Attack on radioactive material in transit
Note: Bomb-type attack has the “usual” explosion issues
(acute explosive/shock effects, fires, debris) plus radiation
issues (site contamination, dispersal of radioactivity beyond
immediate site)
67
Nuclear Device Detonation Physical Effects
„
„
„
„
„
„
Air blast
Thermal radiation
Initial nuclear radiation
Residual nuclear radiation
Crater formation
Ground shock
68
Radiation Poisoning
„
„
„
Small area contamination (localized release of radioactivity)
Larger release in air or water
Note: Must consider single event vs. ongoing poisoning
69
Response to Terrorist Attack
„
„
Crisis management—acute response
Consequence management—long-term effort
70
Medical Issues
„
„
„
Acute
− “Usual” medical problems for bomb-type attack (injuries,
burns)
− Acute radiation syndromes (unlikely for radiation
poisoning)
− Patient internal contamination
Delayed
− Radiation carcinogenesis
Note: Must consider both acute and delayed effects of in utero
irradiation
71
Psychosocial Issues
„
„
„
„
Radiation as an “invisible toxin”—some attacks may be
explicitly designed more for psychosocial than physical
impact
Acute and chronic psychosocial reaction is a central concern
Risk perception is high-risk—toxic hazard per se plus terrorist
(i.e., non-accidental) event
High-risk groups for psychosocial harm—children, mothers
with young children, emergency workers, clean-up workers
72
Decontamination
„
„
„
Personnel decontamination
Site decontamination
Region decontamination
73
Surveillance
„
„
Known attack—is radioactivity present?
Radiation poisoning monitoring of water and air
74
Accumulation of Pollutants
As air moves
across the
continent from
west to east, each
major population
area adds to the
total pollution in
the atmosphere
Source: Adapted by CTLT from Boyce, A.
75
Normal Pattern
Source: Adapted by CTLT from Mackenzie, F. T.
76
Inversion Layer
Source: Adapted by CTLT from Mackenzie, F. T.
77
Sources of Groundwater Contamination
Source: Adapted by CTLT from Nadakavukaren, A.
78
Surface Water Contamination
„
Point and nonpoint sources of surface water contamination
Source: Adapted by CTLT from Bucholz, R. A.
79
Water System Facts
Source: Adapted by CTLT
80