SOLUBLE URANIUM DEFINITION FOR REGULATORY COMPLIANCE

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Hubert Neal
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1 SOLUBLE URANIUM DEFINITION FOR REGULATORY COMPLIANCE Rland Benke, Ph.D., CHP (Center fr Nuclear Waste Regulatry Analyses) Tanya Oxenberg, Ph.D. (U.S. Nuclear Regulatry Cmmissin) James Webb (U.S. Nuclear Regulatry Cmmissin) 2014 Health Physics Sciety s Radiatin Safety Cnference (July 13 17, 2014)

Backgrund Uranium extractin practices have evlved ver decades Existing regulatry guidance is being expanded t address in-situ recvery prcesses and

2 Backgrund Uranium extractin practices have evlved ver decades Existing regulatry guidance is being expanded t address in-situ recvery prcesses and peratins CNWRA and U.S. Nuclear Regulatry Cmmissin (USNRC) are updating Regulatry Guide 8.30, Health Physics Surveys in Uranium Recvery Facilities 2

3 Regulatry Limits Radilgical and chemical txicity cnsideratins apply t ccupatinal uranium intakes Annual radiatin dse limits in 10 CFR Weekly intake limit f 10 mg f sluble uranium per 10 CFR (e) Occupatinal limits fr sluble uranium exist t prevent chemical txicity effects n kidney functin due t uranium accumulatin in the kidney and its persistence with time 3

4 Regulatry Definitin Gap In peratinal settings at uranium recvery facilities, uranium tends t be a mixture f chemical cmpunds and multiple inhalatin classes. Uranium re is an exceptin; singular inhalatin class W applies N sluble uranium definitin in 10 CFR Part 20 Guidance needed n which inhalatin classes relate t sluble uranium s that weekly ccupatinal intakes can be cmpared t the 10-mg limit specified in 10 CFR (e) 4

5 Recmmended Definitin Recmmended definitin fr sluble uranium INHALATION CLASS BLOOD UPTAKE FRACTION, f 1 REGULATORY POSITION D 0.05 Sluble W 0.05 Sluble Y Insluble Technical basis addressed by remainder f presentatin 5

6 Bikinetic Mdeling Bikinetic mdels represent the human bdy by a grup f intercnnected cmpartments. Regins f the human respiratry system Organs (e.g., kidney) Transfer rates specified between cmpartments Cmpute transfer t, accumulatin in, and remval r excretin frm cmpartments 6

7 Uranium Cncentratin in the Kidney Bikinetic mdeling fr uranium has been described. NUREG 0874, Internal Dsimetry Mdel fr Applicatins t Biassay at Uranium Mills, U.S. Nuclear Regulatry Cmmissin, Washingtn, DC, July Calculated kidney cncentratins Varius uranium cmpund mixtures Inhalatin and ingestin Single and cntinuus intakes 7

$fractins influenced by particle size Transfer rates$

8 Internal Dsimetry Calculatin Influenced by aersl particle size and chemical frm Aersl depsitin fractins influenced by particle size Transfer rates amng cmpartments influenced by chemical frm (Inhalatin classes) 8

9 Internal Dsimetry Calculatin 3 pathways via lung cmpartments thrugh bld Many distinct pathways t kidney NP,B TB,B P,B NP,B TB,B P,B Calculated time dependent slutin fr each pathway 9

10 Internal Dsimetry Calculatin 3 pathways via lung cmpartments thrugh gastrintestinal tract (4 slutins) Many distinct pathways t kidney NP,B NP,GI TB,GI P,GI TB,B P,B NP,GI TB,GI P,GI(fast) P,GI(slw) Calculated time dependent slutin fr each pathway 10

11 Internal Dsimetry Calculatin 1 pathway via pulmnary lung thrugh lymph nde and bld P,L,B Many distinct pathways t kidney NP,B TB,B P,B NP,GI TB,GI P,GI(fast) P,GI(slw) P,L,B Calculated time dependent slutin fr each pathway 11

12 Internal Dsimetry Calculatin NP,B,S TB,B,S P,B,S Many distinct pathways t kidney NP,B NP,B,S TB,B TB,B,S P,B P,B,S NP,GI TB,GI P,GI(fast) P,GI(slw) P,L,B Calculated time dependent slutin fr each pathway 3 additinal systemic pathways via bld and ther rgans 12

13 Internal Dsimetry Calculatin NP,GI,S TB,GI,S P,GI,S Many distinct pathways t kidney NP,B NP,B,S TB,B TB,B,S P,B P,B,S NP,GI NP,GI,S TB,GI TB,GI,S P,GI(fast) P,GI(fast),S P,GI(slw) P,GI(slw),S P,L,B Calculated time dependent slutin fr each pathway 3 additinal systemic pathways via gastrintestinal tract and ther rgans (4 slutins) 13

14 Internal Dsimetry Calculatin P,L,B,S Many distinct pathways t kidney NP,B NP,B,S TB,B TB,B,S P,B P,B,S NP,GI NP,GI,S TB,GI TB,GI,S P,GI(fast) P,GI(fast),S P,GI(slw) P,GI(slw),S P,L,B P,L,B,S Calculated time dependent slutin fr each pathway 1 additinal systemic pathway via lymph nde, bld, and ther rgans 14

15 Cntinuus Inhalatin: 2-Cmpartment Slutin Presenting examples fr cntinuus inhalatin intake In-viv pathways dictate number f cmpartments and slutins Fractinal transfer thrugh bld and gastrintestinal tract (GI) des nt require separate cmpartment mdeling C 1 Intake rate Lung cmpartment C 2 λ 1 Kidney via bld r via GI and bld λ 2 Kidney Intake rate

16 Cntinuus Inhalatin: 3-Cmpartment Slutin C 1 Intake rate Lung cmpartment C 2 λ 1 Lymph nde C 3 λ 2 Kidney via bld r via GI and bld via bld C 1 Intake rate Lung cmpartment C 2 λ 1 Systemic, rgans ther than kidney C 3 λ 2 Kidney λ 3 λ 3 Kidney Intake rate 1 16

17 Cntinuus Inhalatin: 4-Cmpartment Slutin Cntinuus inhalatin intake Applied 2-, 3-, and 4- cmpartment slutins fr fractinal cntributins f each inhalatin class in the uranium mixture Class D (n pathway cntributins frm pulmnary lung t gastrintestinal tract) Class W Class Y C 1 Intake rate Lung cmpartment C 2 λ 1 Lymph nde C 3 λ 2 Systemic, rgans ther than kidney C 4 λ 3 Kidney via bld r via GI and bld via bld via bld Kidney Intake rate 1 λ 4 17

18 Selected Results fr Inhalatin Intakes Kidney Burden (Uranium Mass in Kidney per Unit Intake Mass) Kidney Burden (Uranium Mass in Kidney per Unit Daily Intake Mass) Single Inhalatin Intake 100 % Class Y 100 % Class W 100 % Class D ,000 Time (days) Cntinuus Inhalatin Intake 100 % Class Y 100 % Class W 100 % Class D ,000 10,000 Time (days) Class D Readily transferred t kidney Class W Lesser effectiveness fr elevating uranium cncentratins in the kidney Class Y Least effectiveness Lwer by mre than an rder f magnitude at shrter times Increased cntributin at lnger times Fr single intake, lng-term kidney burden is significantly lwer than shrt-term values Fr cntinuus intake, lng-term burden is significantly lwer cmpared t burden frm mre sluble cmpunds 18

19 Selected Results fr Ingestin Intakes Kidney Burden (Uranium Mass in Kidney per Unit Intake Mass) Kidney Burden (Uranium Mass in Kidney per Unit Daily Intake Mass) E-05 1E-06 Single Ingestin Intake 100 % Class Y , % Class D 100 % Class D Time (days) 100 % Class Y ,000 Time (days) 100 % Class W Cntinuus Ingestin Intake 100 % Class W Ingestin less effective cmpared t inhalatin Classes D and W mre readily transferred t kidney Same behavir fr Classes D and W fllwing ingestin Substantially smaller cntributins frm Class Y 19

20 Selected Inhalatin Results fr Uranium Mixture Kidney Burden (Uranium Mass in Kidney per Unit Intake Mass) Kidney Burden (Uranium Mass in Kidney per Daily Mass Intake) Single Inhalatin Intake Ttal (All Classes) Class W Cntributin Class Y Cntributin ,000 Ttal (All Classes) Time (days) Cntinuus Inhalatin Intake ,000 10,000 Time (days) Class W Cntributin Class Y Cntributin Uranium cmpund mixture Class D Class W Class Y Class D Dminant cntributin t maximum kidney burden Class W Small cntributin Class Y Negligible cntributin 20

21 Selected Ingestin Results fr Uranium Mixture Kidney Burden (Uranium Mass in Kidney per Unit Intake Mass) Kidney Burden (Uranium Mass in Kidney per Daily Mass Intake) Single Ingestin Intake Ttal (All Classes) Class W Cntributin Class Y Cntributin ,000 Time (days) Cntinuus Ingestin Intake Ttal (All Classes) ,000 10,000 Time (days) Class W Cntributin Class Y Cntributin Uranium cmpund mixture Class D Class W Class Y Classes D & W Significant (equal) cntributins t maximum kidney burden Class Y Negligible cntributin 21

22 Raditxicity vs. Chemtxicity Bikinetic mdeling f maximum kidney burden prvides technical basis frm chemtxic perspective Radilgical limits als apply t uranium intakes Mst restrictive limit (radilgical r chemical) depends n relative abundances f the different uranium cmpunds Applying the recmmended sluble uranium definitin fr the inhalatin f sluble and insluble mixtures Raditxicity is limiting when Class Y abundance > ~9 percent Chemtxicity is limiting when Class Y abundance < ~9 percent 22

23 Cnclusins Calculatin results supprt defining sluble uranium as thse chemical cmpunds assciated with Inhalatin Classes D and W and bld uptake fractins f Class Y cmpunds with a bld uptake fractin f are insluble and prvide small cntributins t the maximum uranium cncentratin in the kidney. Neglecting the insluble cntributin t the uranium cncentratin in the kidney is acceptable because raditxicity is mre limiting than chemical txicity fr inhaled mixtures f sluble and insluble uranium with significant Class Y cntributins. 23

24 Acknwledgement This presentatin is an independent prduct f the Center fr Nuclear Waste Regulatry Analyses and des nt necessarily reflect the view r regulatry psitin f USNRC. The USNRC staff views expressed herein are preliminary and d nt cnstitute a final judgment r determinatin f the matters addressed r f the acceptability f any licensing actin that may be under cnsideratin at USNRC. 24

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