Plutonium Worker Dosimetry

Transcription

1 Plutonium Worker Dosimetry A Birchall M Puncher, J Harrison, A Riddell, V Khokhryakov, S Romanov Bridging the Experimental and Epidemiologic Divide Georgetown University Hotel, Washington DC May 4-6 (2009) Centre for Radiation, Chemical and Environmental Hazards Radiation Protection Division formerly the National Radiological Protection Board

2 Introduction to Internal Dosimetry Structure 1. Introduction to current models 2. Improving on the current models 3. A method for dealing with uncertainties 4. Outstanding problems for Pu dosimetry 5. Conclusions

3 1. Introduction to current models Respiratory tract model 5 main regions Extrathoracic airways ET 1 ET 2 Bronchial BB Bronchiolar Alveolar interstitial bb Al 25475

4 1. Introduction to current models Respiratory tract model Particle transport ET 1 Extrathoracic ET1 1 ENVIRONMENT ET LNET ETseq ET 2 GI-TRACT BB Thoracic 0.01 BBseq 0.03 BB2 10 BB1 bb LNTH 0.01 bbseq bb bb1 2 AI AI1 AI2 AI3

5 1. Introduction to current models Respiratory tract model Absorption f r 1-f r Rapid Slow dissolution dissolution fs b r fs b s (1-f b)s Sr (1-f )s Bound material sb b Ss Blood

6 1. Introduction to current models Respiratory tract model Particle transport Particles in initial state Particles in transformed state.001 LN ET ET seq 0.03 ET 1 1 ENVIRONMENT LN' ET ET'seq ET GI-TRACT 2 ET' BB seq BB 2 BB 1 BB' seq BB' 2 BB' LN bbseq bb 2 bb 1 s pt LN' bb'seq bb' 2 bb' TH TH AI 1 AI2 AI AI' 1 AI' 3 2 AI' GI-TRACT Absorption (1-f b)sp LN ETb fs b p fs b t ET b (1-f b)st LN THb Bound BB b bb b AI b Blood

7 1. Introduction to current models Systemic model Soft tissues ICRP 56+ type models Intermediate Rapid Slow Skeleton Cortical volume Cortical Skeleton surface (with remodelling) Trabecular Cortical marrow Trabecular Trabecular Trabecular volume surface marrow Urinary bladder contents Kidney Blood Liver Liver 2 Liver 1 GI cont Gonads Urine

8 1. Introduction to current models GI tract model Rate constant Rate (d -1 ) λ ST 24 λ SI 6 λ ULI 1.8 λ LLI 1 f 1 ' λ s λ s % λ SI

9 2. Improving on the current models ICRP 1. Dosimetry Nuclear decay Bone dosimetry 2. Biokinetics Respiratory tract Systemic models GI-tract models Results preliminary Dose per unit intake (1Bq) Dose per unit excretion (1mBq) Target Dose (Gy/Sv) Factor Bone Mar BB bas BB sec bb AI Lung(eq) Eff Dose

10 2. Improving on the current models Respiratory tract model change? change? ch hange? change?

11 2. Improving on the current models Respiratory tract model (particle transport) Extrathoracic current proposed 50% 1 ET 1 environment 40% 20% 3 ET 1 ET 1 environment 50% ET GI tract % ET 2 50 GI tract BB BB

12 2. Improving on the current models Respiratory tract model (particle transport) Effect of Extrathoracic changes No significant effect

13 2. Improving on the current models Respiratory tract model (particle transport) Bronchial/Bronchiolar Current model ET 2 Proposed KI model ET 2 10 BB 2 BB 1 BB bb 2 bb bb 1 1 AI AI

14 2. Improving on the current models Respiratory tract model (particle transport) Effects of the KI model for Type M Dose per unit intake (1Bq) Dose per unit urine (1mBqd -1 at 100d) Target Dose (Gy/Sv) Factor Bone Mar e BB bas 2.54E BB sec 1.71E bb 1.22E AI 5.03E Lung(eq) 1.29E Target Dose (Gy/Sv) Factor Bone Mar 3.52E BB bas 3.77E BB sec 2.53E bb 1.80E AI 7.45E Lung(eq) 1.90E Eff Dose 3.12E Eff Dose 4.63E

15 2. Improving on the current models Respiratory tract model (particle transport) Effects of the KI model for Type S Dose per unit intake (1Bq) Dose per unit urine (1mBqd -1 t=100d) Target Dose (Gy/Sv) Factor Bone Mar 2.25E-0725E BB bas 2.82E BB sec 1.52E bb 2.65E AI 3.53E Lung(eq) 4.31E Target Dose (Gy/Sv) Factor Bone Mar 1.43E BB bas 1.79E BB sec 1.69E bb 1.80E AI 2.24E Lung(eq) 2.74E Eff Dose 7.91E Eff Dose 5.02E

16 2. Improving on the current models Respiratory tract model (particle transport) AI region current proposed bb 1 bb AI 1 AI 2 AI LN TH A I 30% 60% 10% 70% 30% LN TH

17 2. Improving on the current models Respiratory tract model (particle transport) Effects of delayed particle transport from AI (Type M) Dose per unit intake Dose per unit urine Target Dose (Gy/Sv) Factor Bone Mar 2.39E BB bas 2.67E BB sec 2.58E bb 1.20E AI 4.98E Lung(eq) Target Dose (Gy/Sv) Factor Bone Mar 3.37E-0437E BB bas 3.76E BB sec 3.63E bb 1.68E AI 7.00E Lung(eq) 2.92E Eff Dose 3.24E Eff Dose 4.55E

18 2. Improving on the current models Respiratory tract model (particle transport) Effects of delayed particle transport from AI (Type S) Dose per unit intake Dose per unit urine Target Dose (Gy/Sv) Factor Bone Mar 4.53E BB bas 3.06E BB sec 3.25E bb 1.81E AI 8.27E Lung(eq) 8.06E Target Dose (Gy/Sv) Factor Bone Mar 2.69E BB bas 1.81E BB sec 1.93E bb 1.07E AI 4.90E Lung(eq) 4.78E Eff Dose 1.49E Eff Dose 8.86E

19 2. Improving on the current models Respiratory tract model (absorption) Specific absorption rates Pu nitrate f r 1f 1-f r Type M specific Rapid dissolution Slow dissolution f r 10% 17% S r S s s r Blood s s

20 2. Improving on the current models Respiratory tract model (absorption) Specific absorption rates Pu oxide f r 1f 1-f r Type S specific Rapid dissolution Slow dissolution f r 0.1% 0.26% S r S s s r Blood s s

21 2. Improving on the current models Respiratory tract model (absorption) Effects of specific absorption rates for Pu nitrate Dose per unit intake Dose per unit urine Target Dose (Gy/Sv) Factor Bone Mar 1.25E BB bas 2.65E BB sec 2.65E bb 1.26E AI 1.10E Lung(eq) 2.54E Target Dose (Gy/Sv) Factor Bone Mar 5.24E BB bas 1.11E BB sec 1.00E bb 5.26E AI 4.60E Lung(eq) 1.06E Eff Dose 1.87E Eff Dose 7.80E

22 2. Improving on the current models Respiratory tract model (absorption) Specific absorption rates for Pu oxide Dose per unit intake Dose per unit urine Target Dose (Gy/Sv) Factor Bone Mar 2.21E-0721E BB bas 2.98E BB sec 3.25E bb 1.66E AI 3.53E Lung(eq) 4.68E Target Dose (Gy/Sv) Factor Bone Mar 1.46E BB bas 1.97E BB sec 2.15E bb 1.10E AI 2.33E Lung(eq) 3.10E Eff Dose 8.31E Eff Dose 5.50E

23 2. Improving on the current models Biokinetics (new Pu model)

24 2. Improving on the current models Biokinetics (new Pu model) Effects of new Leggett model for type M Dose per unit intake Dose per unit urine Target Dose (Gy/Sv) Factor Bone Mar e BB bas 2.55e BB sec 2.56e bb 1.18E AI 4.91E Lung(eq) 2.06E Target Dose (Gy/Sv) Factor Bone Mar 3.55E BB bas 3.90E BB sec 3.93E bb 1.81E AI 7.71E Lung(eq) 3.14E Eff Dose 3.34E Eff Dose 5.11E

25 2. Improving on the current models Biokinetics (new Pu model) Effects of new Leggett model for type S Dose per unit intake Dose per unit urine Target Dose (Gy/Sv) Factor Bone Mar 2.17E BB bas 2.97E BB sec 3.26E bb 1.66E AI 3.53E Lung(eq) 4.69E Target Dose (Gy/Sv) Factor Bone Mar 1.41E BB bas 1.93E BB sec 2.12E bb 1.08E AI 2.30E Lung(eq) 3.05E Eff Dose 8.44E Eff Dose 5.49E

26 2. Improving on the current models GI tract model from RT model Stomach SI Blood ULI LLI Excretion

27 2. Improving on the current models HAT model Oral cavity Pharynx Teeth B L O O D Salivary glands Secretory organs Fast 0esophagus 1 0esophagus 2 Stomach Small intest Left colon Slow Stomach wall SI wall LC wall Oral mucosa Hepatic artery Liver Portal vein B L O O D Right colon Sigmoid Rectum RC wall SR wall

28 2. Improving on the current models Respiratory tract model (effects?) Effects of the new HAT model No significant effect

29 3. A method for dealing with uncertainties Monte Carlo parameter 1 parameter 2.. parameter n MODEL Evaluate quantity of interest

30 3. A method for dealing with uncertainties How dose is calculated CONSTANT VARY Bioassay prediction MODEL INTAKE Internal Dose Deposition Weighting Intake

31 3. A method for dealing with uncertainties How dose is calculated CONSTANT VARY Measurement Error MODEL likeliho ood INTAKE Internal Dose Deposition Weighting intake Monte

32 3. A method for dealing with uncertainties The WeLMoS method 1 P 1 P 2 P 3. P n 2 P 1 P 2 P 3. P n 2 N P 1 P 2 P 3. P n Normalisation

33 3. A method for dealing with uncertainties Quick look at software

34 3. A method for dealing with uncertainties Dose per unit intake (Effects) In order to illustrate the effects of proposed model changes we have chosen equivalent lung dose The prior distributions for parameter distributions are taken from the Alpha Risk project and are provisional at the moment. All calculations have been made using the software that implments the WeLMoS method

35 3. A method for dealing with uncertainties Dose per unit intake (Effects) TB Type M AI 50% KI / 50% ICRP K PT ~ LN(1,1.73) 1 Med 1.57E-05 GSD DG / 0% ICRP K PT ~ LN(1,1.73) Med 2.21E-05 GSD 1.73 Systemic Absorption Med 2.05E-05 Med 2.47E-05 GSD 1 GSD % Leg / 0% ICRP F r ~ LN(0.17,2) s R ~ LN(1,4) S s ~LN(0.0012,2.3)

36 3. A method for dealing with uncertainties Dose per unit intake (Effects) TB Type S AI Med 4.51E-05 Med 8.06E-05 GSD 1.24 GSD % KI / 50% ICRP 100% DG / 0% ICRP K PT ~ LN(1,1.73) 1 K PT ~ LN(1,1.73) Systemic Med 4.69E-05 GSD 1 100% Leg / 0% ICRP Absorption F r ~ LN(0.0026,3.1) s R ~ LN(1,4) S s ~LN(0.0001,4.2) 0001 Med 4.68E-05 GSD 1.21

37 4. Outstanding problems for Pu dosimetry Two main issues A. Possible biasing i of doses estimated t with urine B. Existence of a bound fraction

38 4. Outstanding problems for Pu dosimetry A. Possible biasing Some suggestion that estimates of dose using urine overestimates that made by autopsy BNFL X3? Mayak < X2?

39 4. Outstanding problems for Pu dosimetry Possible explanation G Etherington G, Stradling GN, Hodgson A and Fifield LK. Anomalously high excretion of Pu in urine following inhalation of plutonium nitrate. Rad. Prot. Dosim. 105 (1-4) pp (2003)

40 4. Outstanding problems for Pu dosimetry Possible explanation Bailey MR, Etherington GE, Birchall A, Smith JRH, Cassey K, Dodd DH, Ham GJ, Hutton CA, Jarvis NS, Kovari M, Marsh JW, Shutt A and Youngman MJ. Assessment of Internal Dose to Subjects in the HSE Follow-uo to Gardner Study. NRPB R- 286(1996)

41 4. Outstanding problems for Pu dosimetry Conclusions? Needs more investigation In Alpha Risk Contract t it is not taken into account but attention is drawn to a possible biasing effect

42 4. Outstanding problems for Pu dosimetry B. Bound fraction Absorption = Dissolution + Uptake f r 1-f r Rapid Slow dissolution dissolution fs b r fs b s (1-f b)s Sr (1-f )s Bound material sb b Ss Blood Default ICRP-66 assumption: same from all reions of RT

43 4. Outstanding problems for Pu dosimetry Bound fraction Some evidence for long term bound state Khokhryakov VF et al. Title?. Health Phys 88; (2005) ~2% Dagel GE et al. Risk estimates for lung tumours from inhaled 239 PuO 2, 239 Pu(NO 3 ) 4 in beagle dogs. Radiat. Prot. Dosim. 26; (1989) James AC et al. USTUR whole body case 0269: demonstrating effectiveness of iv. Ca-DTPA for Pu. Radiat. Prot. Dosim 127; (2007) ~0.2% ~8%

44 2. Improving on the current models Respiratory tract model (effects?) Effects of a long term bound state on Type M Pu Dose per unit intake Dose per unit urine Target Dose (Gy/Sv) Factor Bone Mar 2.37E BB bas 3.54E BB sec 3.89E bb 7.27E AI 1.45E Lung(eq) 3.05E Target Dose (Gy/Sv) Factor Bone Mar 3.75E BB bas 5.59E BB sec 6.15E bb 1.15E AI 2.28E Lung(eq) 4.82E Eff Dose 1.53E Eff Dose 2.41E

45 2. Improving on the current models Respiratory tract model (effects?) Effects of a long term bound state on Type S Pu Dose per unit intake Dose per unit urine Target Dose (Gy/Sv) Factor Bone Mar 2.21E-0721E BB bas 8.38E BB sec 3.82E bb 1.77E AI 3.67E Lung(eq) 5.22E Target Dose (Gy/Sv) Factor Bone Mar 1.50E BB bas 5.67E BB sec 2.58E bb 1.20E AI 2.48E Lung(eq) 3.53E Eff Dose 1.19E Eff Dose 8.03E

46 4. Outstanding problems for Pu dosimetry Bound fraction Priors for the Alpha Risk Project Type M Med 9.51E-05 GSD 2.08 S b ~ LN(0.0002,1.73) F b ~ TRI(0, 0.08, 0) K FB = 0.25

47 4. Outstanding problems for Pu dosimetry Bound fraction Priors for the Alpha Risk Project Type S Med 4.75E-05 GSD S b ~ LN(0.0002,1.73) F b ~ TRI(0, 0.08, 0) K FB = 0.25

48 4. Outstanding problems for Pu dosimetry Other sources of uncertainty For the Alpha risk project, we also plan to take account of deposition uncertainties Med 4.78E-05 GSD AMAD B F n ET th GSD f R ET aer

49 4. Outstanding problems for Pu dosimetry What happens when you fold everything in? Dose per unit intake Pu Nitrate Pu Oxide Med 6.49E-05 Mean 8.67E-05 GSD 2.33 Med 1.21E-04 Mean 1.70E GSD 2.57

50 4. Outstanding problems for Pu dosimetry What happens when you fold everything in? Dose per unit bioassay Pu Nitrate Pu Oxide Med 1.61E-02 Mean 2.17E-02 GSD 2.22 Med Mean 1.29 GSD 5.0

51 5. Conclusions Changes currently being considered by ICRP Radiation Decay New systemic models New GI Tract model New respiratory tract changes X X X

52 5. Conclusions Changes currently being considered by ICRP ET Type M X Type S X TB Type M BB sec (x1/20) Type S BB sec (x1/20) AI Type M X Type S AI (x2) ABS Type M U (x2) Type S X

53 5. Conclusions Changes specific to Pu dosimetry Biasing Type M x1/3 Type S x1/3 Bound F Type M Lung x15 Type S X

54 5. Conclusions Uncertainties Uncertainties in particle transport tend to swamp subtle changes to biokinetic models currently being considered by ICRP. For nitrates, the existence of a small long term bound fraction can substantially increase lung dose. For oxides, the main source of uncertainty arises from the uncertainty in s S especially if estimates are made from urine.

55 5. Conclusions The focus of future research should be: 1. More accurate characterisation of uncertainties (variability) in particle transport. 2. More accurate determination of s s for oxides. 3. Determine if Pu is bound in the upper airways for a long term. 4. Investigation of the x3 bias between urine and autopsy data. THE END