TE NORM and ALARA in the Florida Phosphate

TE NORM and ALARA in the Florida Phosphate Industry Brian Birky, Ph. D. Florida Institute of Phosphate Research Julian Hilton, D. Phil. Oxford University Aleff. Group Vaughn Astley, Ph. D. Aleff. Group

NORM and ALARA in the Florida Phosphate Industry Brian Birky, Ph. D. Florida Institute of Phosphate Research Julian Hilton, D. Phil. Oxford University Aleff. Group Vaughn Astley, Ph. D. Aleff. Group

Today’s Presentation • Occupational dose studies by Florida Institute of Phosphate Research (FIPR) • ALARA / absolute dose considerations • The phosphogypsum issue: waste or asset • The gap between supposition and reality • Did the R drop out of ALARA?

The Phosphate Industry in Florida • • > 6, 000 directly employed > 30, 000 indirectly employed Supplies 75% of US phosphate demand Supplies 25% of world phosphate demand

FIPR Occupational Dose Studies • NORM Energy Spectrum – Industry specific dose conversion factors • Florida Phosphate Industry Dose Assessment – External dose – Inhalation dose • Inhalation Dose – Follow-up Studies

Central Florida NORM Distribution (Bq/kg) Ra-226 U-238 Material Process Stage 1400 Matrix Mining 1430 1610 Clays 230 200 Sand 1460 1350 Rock Concentrate 1100 <40 Phosphogypsum <40 1100 Phosphoric Acid 170 2560 MAP/DAP Fertilizer Products >>1400 420 Scale Waste Beneficiation Chemical Processing

FIPR Study No. 1 – Phosphate Industry Specific Dose Conversion Factors • Florida International University (funded by FIPR) – Examined External dose only – Method: Broad-energy germanium spectrometer in the field – Characterized NORM energy spectrum – Developed Roentgen-to-Rem DCFs

Phosphate Industry Specific Dose Conversion Factors (Cont. ) • One-to-one conversion commonly used • Actual dose rate – 40 to 45% of common survey meter readings in m. R/hr – Doses estimated using survey meters are overestimated by up to 60% – Recyclable metals are buried instead of salvaged

FIPR Study No. 2 - Results of the Phosphate Industry NORM Study • Doses were low < 1 m. Sv/a • External dose was the big contributor • But, internal dose could drive the TEDE up an order of magnitude in some situations

FIPR Study No. 3 – Inhalation Doses in the Phosphate Industry • Actually two related studies – Particle size distributions by site areas – Chemistry and radioactivity by size fractions – Particle shapes and densities – Solubility of size fractions in lung fluid – ICRP-66 HRTM and LUDEP/IMBA codes

Research Procedure for Inhalation Dose Assessment Air Sampling & Size distribution Project 1 Project 2 (Cascade Impactor) Determination of particle size distribution (Hi-Vol Sampler) For analysis of density and radioactivity Particle Shape Analysis Element Composition Analysis Particle Density Analysis Radioactivity Measurement (SEM) Determination of particle shape factor (EDXS) Quantification of elemental distribution (Pycnometer) Determination of Particle density (HPGe) Determination of Particle radioactivity Effective Dose Scaling Factors Inhalation Dose Assessment Particle Solubility In Lung Fluid (IMBA, LUDEP) Generation of effective dose scaling factors (IMBA, LUDEP) Calculation of inhalation dose w/o solubility data (In-Vitro Test) Radionuclide dissolution fractions & rates Risk Assessment to Workers in the Phosphate Industry Annual total effective dose calculation Recommendation

Dissolution Rates of Phosphate • If radioactive element is present as a minor constituent of inhaled particles, absorption of the radionuclide to body fluids may be controlled by surrounding matrix rather than elemental form of the radionuclide. [ICRP 71] • Dissolution rate of surrounding matrix (phosphate) • Measurement of phosphate ion concentration in solution (IC)

Dissolution Rates of Phosphate (Cont. )

Dissolution Rate of Uranium

Dissolution Rate of Thorium

Dissolution Rate of Lead

TEDE Results for the Industry • Final reports from the University of Florida are due soon • Several are in various stages of publication – First is in the current issue of Health Physics – More to follow – Full FIPR publications will be posted on the web at www. fipr. state. fl. us

Where Do You Focus ALARA Resources? You may reasonably choose: • To apply no further resources • Worker education – Time, Distance, Shielding – Proper use of dust masks • Dust suppression • Ventilation of rock tunnels

The Price of the Dropped R?

The Great Divide • The industry views phosphogypsum as a potentially useful by-product • Regulatory agencies view phosphogypsum as a waste that does not belong in commerce – Radium content – Radon potential

New Project: Stack Free by ’ 53? • Establish an authoritative database by country and by region of regulations and laws affecting the industry, and the extent to which such laws impact on commerce and trade • Evaluate potentially beneficial uses of phosphogypsum in construction and agriculture, including the use of phosphogypsum as a source of nutrients • Provide new information to policymakers on the safety aspects of phosphogypsum

Is it Economical to Use Phosphogypsum (PG)? • Will the PG be sold or given away? • Transportation costs will determine the distance PG can be delivered • Competitive sources of sulfur – Natural gypsum – Electric power, etc. • Engineer a desirable PG?

The Key Question • Is the practice of stacking phosphogypsum truly in keeping with ALARA as supposed, or is it really at odds with the ALARA philosophy?

What Data are Needed to Answer the Key Question? • Data in two categories – Risk to the public and environment from PG use • Standard pathway techniques – Risk avoided by the use of PG • Is this assessment done as easily? • Literature review in progress • Support from Rothamsted Research (UK)

Data Needed to Determine Risk from PG Use • PG characteristics – Radioactivity concentrations for radionuclides in PG by production site – Concentrations of heavy metals (Cd, Pb, Hg, etc. ) • Data for Defined Application Scenarios

Data Needed to Determine Risk from PG Use (cont. ) • For example: PG as a soil amendment – Application rates for optimum growth – Soil to plant transfer of radionuclides and metals – Accumulation and leaching • Conduct ingestion pathway analyses • Translate dose to risk

Data Needed to Determine Risk Avoided from PG Use • Improved nutrition – Estimate of increased life expectancy • Improved availability of foods – Lives saved

Data Needed to Determine Risk Avoided from PG Use (Cont. ) • Decreased risk of stack failure – Estimate of failure rate and environmental damage • Decreased discharge of PG to the environment – Estimate of long-term effects

Data Needed to Determine Risk Avoided from PG Use (Cont. ) • Benefits from other uses – Road beds • All are difficult to quantify

Regulatory Practice and ALARA • USEPA – If the maximally exposed hypothetical individual exceeds a risk of 1 E 04, the practice is not acceptable • Is this keeping with the ALARA philosophy if the vast majority of the population will enjoy a decreased risk of detriment and mortality as a result?

Regulatory Practice and ALARA • If the health risks from radiation are surpassed by decreasing societal health risks from other causes, and economic considerations for both industry and the public are favorable, then doses are as low as practical and optimization is achieved

Two Questions Remain • Do you protect the unlikely hypothetical maximum individual at the expense of the more numerous and realistic individuals? • Is it reasonable to reinstate reasonableness in the adjudication of risk – ALAA, or ALARA?

Is this reasonable?