Don CarpenterGeochemist ARCADIS U.S., Inc.Brighton, MI

LEVERAGING THE AGE DATING OF NORM TO AID IN ENVIRONMENTAL CHALLENGES

2 May 2, 2023 © 2013 ARCADIS

The Age of a Radioactive Waste is Often Unimportant, Up to the Time it Becomes Important

“Owner A” “Owner B” “Owner C”

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Ra-228Th-228

Radioactive Age Dating of NORM may be the solution

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This Presentation Will Discuss a Comparatively Unique Age Dating Approach

Ra+2 Ba+2 SO4-2

Ra226 Pb210

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NORM is 20 years old

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Nuclear Instability

Rate of Nuclear Decay

Features of an “Ideal Age Dating” Material

Discussion of Radium-Enriched Barite NORM

Applications of Age Dating of NORM

THIS PRESENTATION WILL SYSTEMATICALLY ADDRESS THE

FOLLOWING ITEMS:

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It is Important to Address a Misconception that Radioactive Instability is Uncommon

H

U

La

Ba

Pb

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260

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Stable IsotopesRadioactive Isotopes

Radioactive Instability is Actually Far More Common Than are “Stable” Isotopes

85% of all known isotopes are radioactive

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Radioactivity is Due to Nuclear Instability Rather than Reactions Between Orbital Electrons

Alpha radiation results in the ejection of two protons and two neutrons

Beta decay results in either the loss (and commensurate gain) of a proton or a neutron

Rate is fixed and is measure of the degree of instability of isotope

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Mathematics of Radioactive Decay are Related by a few Comparatively Simple Equations

-dN/dt = λN0

Rate of decrease in decaying isotope is a function of the decay constant and the number of atoms at any timet½ = ln(2)/ λ

“Half-life” is a function of the decay rate

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Characteristics of a “Good” Age Dating Candidate Consist of a Few Specific Criteria

Absence of prior progeny

Geochemical retention of parent radionuclides

Geochemical retention of progeny

Half Life duration consistent with the age dating challenge• Years or Tens of Years, not minutes or

billions of years

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Decay of Naturally Occurring Uranium and Thorium Generates Radioactive Progeny and NORM

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Radium isotopes are produced within each decay chain

Comparatively short half-life of Radium-228 results in rapid natural attenuation

Lead-210’s 22 year half life allows it to

potentially accumulate

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Predictable Manner of Nuclear Decay Provides Insight as to Radionuclide Composition with Time

Rate of formation of Radium from known activity of Uranium

Rate of formation of Lead-210 from known activity of Radium

Rates of formation of other radionuclides of interest

© 2013 ARCADISMay 2, 202312

Precipitation of Alkaline Earth Sulfates can Co-Precipitate Radium Sulfate forming a NORM

Ba+2 + SO4-2 → BaSO4

Ba+2 + (Ra+2) + SO4-2 → Ba(Ra)SO4

Acid insoluble

Low (“insolubility”) of Barite causes Radium and decay products to be largely retained within crystalline structure

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Lead-210 Will Accumulate at a Fixed Rate in the Barite Scale Due to the Decay of Radium-226

Time of Formation

Time of Formation Plus

20 Years

Time of Formation Plus

40 Years

Lead-210

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Radium-Enriched Barite has all of the “Ideal” Age Dating Characteristics

Geochemically “inert”

Rapidly formedAbsence of any progeny due to geochemical-induced separationRetains Radium parent(s) and progenyRadium-226 has decay rate commensurate with needsRadium-228 and Po-210 may also be employed for “recent” NORM

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The Predicable Rate of Lead-210 Accumulation Allows an Age Estimate to be Calculated

Ratio of Lead-210 to Radium-226 allows an “age of NORM formation” to be calculated

Percent of Lead-210 “In-growth” with Time (in years)

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Lead-210 Data may also Aid in Identifying Possible Different Sample Populations of NORM

Relationship Between Radium-226 Activity and Estimated Lead-210-Based Age

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Estimated Lead-210-Based Age (Years)

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“Young” NORM Might Allow for “Independent” Age Estimates to be Made

Pb-210/Po-210 and Ra-228/Th-228

Ra-228/Th-228 and Ra-226/Pb-210

Up to 2 years

2 to 6 years

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Age Estimates Need to Comport with “Other” Information

Age estimates of NORM pre-dating operational activities

“Known” date of NORM formation

Help establish accuracy of “anecdotal” information

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Age Dating Information May Provide Critical Data for Specific Environmental Needs

Help identify responsible parties for NORM

Provide an upper limit for the time of exposure to potential receptors; a possibly critical element in lawsuits

Develop an age estimate for NORM or the ages of NORM produced by different processes over time.

Provide insight into the mass and location of NORM related to a specific operational change or processing of different solutions.

State-based regulations may exempt “old” NORM that predates regulations

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Imagine the result