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Radioactivity in the environment

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3 categories of radioactive material. Natural radioactivity ... High concentrations may be natural, or from global fallout, or from LANL. ... – PowerPoint PPT presentation

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Title: Radioactivity in the environment


1
Radioactivity in the environment
  • Michael McNaughton
  • For the Community Radiation Monitoring Group
  • Wednesday, December 10th, 2009

2
Radioactivity in the environment
  • Response to the GAP Report
  • Radioactivity in indoor dust
  • Radioactive material downwind of LANL
  • Can we tell where it came from?
  • Is indoors different from outdoors?
  • What are the potential health effects?
  • Detailed calculations and references are
    available.

3
3 categories of radioactive material
  • Natural radioactivity
  • Radon, potassium-40, uranium, thorium
  • Global fallout from testing
  • Cesium-137, strontium-90, plutonium, americium
  • LANL radioactive materials
  • Tritium, plutonium, americium, depleted uranium,
    cesium-137, strontium-90, cobalt-60

4
Variability
  • The concentrations of natural radioactivity vary
    greatly.
  • High concentrations may be natural, or from
    global fallout, or from LANL.
  • It is not possible to establish background
    concentrations.

5
Potassium-40 in soils large variations
6
Thorium in soils large variations
7
Uranium in soils large variations
8
NM Mining Districts
  • Uranium
  • Forest
  • Metals
  • Other

9
Aerial Gamma Survey of LANL
10
LANL has been extensively studied
  • More than 99 of radioactivity detected on the
    surface is from natural sources
  • Radionuclides are identified by spectroscopy
  • Mostly natural potassium-40, thorium, and uranium
    decay products
  • Pink, red, and black are LANL radioactivity

11
Gamma Spectroscopy
12
Downwind
No measurable effect from airborne deposition
source
5.0
Miles
1.0
Rio Grande
Sangre de Cristo
LANL
  • Downwind concentrations depend on distance
  • Calculations and observations show deposition (in
    soil and sediment) of airborne radioactive
    material is too small to measure beyond 1 mile.

13
Plume from Cerro-Grande Fire
14
Plume from Cerro-Grande Fire
15
Plumes from known LANL sources extend less than 1
mile.
No visible deposition plume down wind from
potential LANL dust sources
16
Indoor dust
Most dust particles are large
  • Samples from NMED/OB and Los Alamos Monitor
    offices
  • Analyzed by Paragon Analytics lab
  • Greater than 99 from natural sources
  • Mostly radon decay products
  • .08 pCi/gram from LANL at L. A. Monitor

micrometers
nanometers
Radon decay products are on small particles
17
DP Road
  • At Los Alamos Monitor, 0.5 of the alpha
    radioactivity is plutonium from TA-21
  • Concentration 0.08 pCi/g
  • Potential dose from plutonium

18
LANL Contamination
  • LANL airborne contamination is found only within
    1 mile of Los Alamos County
  • Beyond 1 mile, calculations and observations show
    deposition of airborne contamination is too small
    to be measured
  • (Waterborne LANL contaminants may be found in
    canyons downstream of historical LANL outfalls)

19
Radon
  • Indoors, most of the radioactivity and most of
    the dose is from radon decay products
  • They are attached to very small particles
  • Small particles are difficult to collect, so the
    data vary
  • Short-lived activity is 50,000,000 pCi/g
  • Long-lived activity is 20,000 pCi/g
  • Dose from radon is 250 mrem/year

20
Accumulation of radon decay products
on an AIRNET filter
21
How can we determine what comes from LANL?
  • Regional Statistical Reference Level (RSRL) is no
    more than a reference level
  • Radioactivity can be greater than the RSRL
  • In such cases, consider
  • What radionuclides are prevalent at LANL?
  • What isotopes are prevalent at LANL?
  • Then, compare using models and calculations

22
Activity can differ from RSRL
  • Elevation More rain and especially snowfall
    causes more fallout at higher elevations
  • Soil and rock in some regions is high in
    naturally radioactive elements such as uranium
  • Runoff from less permeable slopes can focus
    fallout in basins
  • Bioaccumulation concentrates radionuclides in
    plant matter
  • Forest fires concentrate radionuclides in the ash

23
Other data RSRL
  • Higher than RSRL concentrations are measured in
    many locations, worldwide
  • In Colorado, Colorado State University measured
    cesium-137 concentrations greater than those at
    Trampas Lake.
  • NMED/OB investigations are continuing.

24
What radionuclides are prevalent at LANL?
  • Largest historical emissions from LANL are
    tritium, plutonium-239, depleted uranium
  • Much larger than strontium-90 or cesium-137
  • In contrast, downwind data show mostly cesium-137
    and strontium-90
  • Observations are not consistent with LANL origin
  • Observations are consistent with global fallout

25
Cobalt-60
  • Cobalt-60 was prevalent at TA-2 and TA-53
  • Emissions of cobalt-60 are comparable with
    strontium-90 and cesium-137
  • But cobalt-60 has not been observed outside Los
    Alamos County
  • This is consistent with models and calculations
  • Measurements and models show LANL airborne
    contamination is not measurable more than 1 mile
    from Los Alamos County

26
What isotopes are prevalent at LANL?
  • LANL higher uranium-238
  • Not observed downwind of Los Alamos
  • LANL higher plutonium-239
  • Fallout higher plutonium-240
  • Proportions of uranium-238 indicate that airborne
    radiological contamination is not measurable more
    than 1 mile from Los Alamos County
  • Plutonium investigation is ongoing

27
Using models and calculations
  • Two models (CAP88 and Hotspot) were used to
    calculate airborne cesium-137 and strontium-90 in
    Embudo Valley
  • LANL contribution is a million times less than
    the amounts observed
  • Results are consistent with global fallout, not
    with LANL origin
  • LANL airborne contamination is not measurable in
    Embudo Valley

28
Dose
  • The measure of health detriment due to
    radioactivity is the dose, measured in mrem
  • The maximally exposed individual, MEI, receives
  • Total dose from all natural and man-made sources
    is 500 mrem/year around LANL
  • Some natural locations 1,000 mrem/year
  • These locations are extensively studied, and
    there is no measurable health detriment

29
Doses
30
Sources of Airborne Radiation Exposure Around LANL
Background radiation 500 mrem/year Additional
from LANL Man-made products e.g., building materials, smoke
detectors (2)
Potassium-40 e.g., bananas, food, ash (8)
Medical and dental (10)
Cosmic radiation (13)
Terrestrial Radiation e.g., in rock, potassium,
thorium, uranium (19)
100
Radon (48)
LANL all-pathways e.g., stacks dust (0.2)
Nuclear fallout i.e., tests 1940s-60s (0.2)
31
Conclusions
  • We studied the Government Accountability Project
    (GAP) data
  • We gathered our own data
  • Almost all the radioactivity in indoor dust is
    naturally occurring
  • Measurements and models show that airborne
    contamination from LANL is not measurable more
    than 1 mile from Los Alamos County
  • All data show no measurable health detriment from
    LANL airborne contamination
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