• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content

Loading…

Flash Player 9 (or above) is needed to view presentations.
We have detected that you do not have it on your computer. To install it, go here.

Like this presentation? Why not share!

Occupational dose assessment of iodine intake at ansto meriaty

on

  • 819 views

 

Statistics

Views

Total Views
819
Views on SlideShare
819
Embed Views
0

Actions

Likes
0
Downloads
4
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Adobe PDF

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    Occupational dose assessment of iodine intake at ansto meriaty Occupational dose assessment of iodine intake at ansto meriaty Presentation Transcript

    • OCCUPATIONAL DOSE ASSESSMENT OF IODINE-131 AT AUSTRALIAN NUCLEAR SCIENCE &TECHNOLOGY ORGANISATION Haider Meriaty Safety, Environmental & Radiological Assurance ANSTO, Locked Bag2001, Kirrawee DC, NSW 2232, Australia ham@ansto.gov.au
    • INTRODUCTION: • ANSTO Internal Dosimetry provides monitoring and assessment of contaminant intake and their relevant doses. • Direct measurements cover: organs, lungs or whole body. • The detection systems are NaI, HPGe and Phoswich. • Calibration phantoms are BOMAB and IAEA Thyroid. • ICRP and IAEA publications are utilised to obtain the intake and the corresponding committed doses.
    • OBJECTIVES: • To evaluate the thyroid’s retention functions (RF) and data of Predicted Intake Fractions (PIF), given in ICRP publications 54&78, and their impact on earlier measurements. • To Compare Iodine-131 Intakes of subjects, which obtained by the retention functions and data of Predicted Intake Fraction. • To illustrate a realistic and practical “transfer time” that improve the accuracy of Intake.
    • THREE COMPARTMENTAL MODEL, ICRP-78 : • Assumes three compartments for translocation. • Provides Rate Constants between compartments. • Provides data of predicted intake fraction (PIF). • Transfer & Body compartments have different “OUT” Rate Constants. • The following Retention Function was derived: 78R -0.382 e(- 0.832 t)+0.24 e(- 8.663x10-3 t)+0.072 e(- 4.62x10-2 t) Th,B=
    • THREE COMPARTMENTAL MODEL, ICRP-54: • Assumes three compartments for translocation. • Provides Rate Constants between compartments. • Provides data of predicted intake fraction (PIF). • Transfer & Body compartments have same “OUT” Rate Constants. • Provides Retention Function: 54R = -0.33 e(- 2.888 t)+0.31 e(- 5.775x10-3 t)+0.018 e(- 6.3x10-2 t) Th,B
    • THREE COMPARTMENTAL BIOKINETIC MODEL OF THYROID Absorption 0.3 Transfer Thyroid Compartment Compartment (0.25d)  = 2.772 d-1} (80d)  = 0.832 d-1  = 8.6710-3 d-1 0.7  = 8.66310-3 d-1  = 5.77510-2 d-1)  = 4.62010-2 d-1 Body’s Rest GREEN: ICRP78 : ICRP54 Compartment (0.8) (0.9) (12d)  = 2.772 d-1} RED 0.1  = 5.77510-2 d-1)  = 1.940 d-1 0.2  = 1.15510-2 d-1 Urine Faeces
    • METHODS: • Derived the retention function (78RTh,B), using the parameters of thyroid 3-compartmental model described in ICRP78 publication. • Compared the similar retention function (54RTh,B) of ICRP54. • Simulated both functions over same period of time and plotted/compared outcomes. • Plotted and compared the values of predicted Intake Fraction, given in both ICRP 54 and 78. • Compared 78RTh,B and 54RTh,B with Predicted Intake Factions (PIF). • Applied PIF and RF to thyroid measurements of two subjects and obtained their Intakes, which then evaluated. • Applied dose conversion factor (ICRP68, 1.1x10-8 Sv.Bq-1) and tissue weighting factor (WT = 0.05) to derive the Committed Effective Dose (CED) and thyroid dose equivalent.
    • RESULTS: Retentions & PIF Values Table 1: Comparison between Thyroid Retentions Functions and Tabulated PIF Values of ICRP 54 and 78 Publications Retentions Functions & Tabulated Fractions (ICRP 54&78 m(t) Elapsed Elapsed Publications) ICRP 54 ICRP 78 Time Time I n t a k e F ra c io n (B q / B q I n t a k e ) 3.0E-01 (h) Retention Tabulated Retention Tabulated (d) Function Fractions Function Fractions 2.5E-01 18.1 2.70E-01 1.40E-01 9.72E-02 0.120 0.753 48.0 2.70E-01 1.60E-01 1.93E-01 0.120 2.000 2.0E-01 49.8 2.69E-01 1.60E-01 1.95E-01 0.120 2.075 1.5E-01 72.0 2.47E-01 1.50E-01 2.05E-01 0.110 3.000 96.0 2.24E-01 1.40E-01 1.97E-01 0.099 4.000 1.0E-01 121.0 2.03E-01 1.30E-01 1.82E-01 0.090 5.040 5.0E-02 144.0 1.86E-01 1.20E-01 1.67E-01 0.082 6.000 168.0 1.69E-01 1.10E-01 1.51E-01 0.074 7.000 0.0E+00 192.0 1.54E-01 1.00E-01 1.37E-01 0.068 8.000 0.000 2.000 4.000 6.000 8.000 10.000 12.000 14.000 216.0 1.40E-01 9.00E-02 1.24E-01 0.062 9.000 Time after Intake (days) 240.0 1.28E-01 8.00E-02 1.12E-01 0.056 10.000 Function-54 Function-78 Table-54 Table-78 314.0 9.56E-02 6.00E-02 8.21E-02 0.043 13.085
    • RESULTS: Subjects Intakes Comparison between I-131 Intakes of Two Contaminated Subjects, using the Comparison of Subject "A" Intake using the Tables & Biokinetic Models and Tabled Fractions in ICRP 54&78 Publications. Retention Functions in ICRP 54&78 Puplications Table 2: I-131 Intake (A0) by subject “A”: 9.0E+04 8.0E+04 Measured Activity (M) Function-54 Table-54 Function-78 Table-78 7.0E+04 Intake (Bq) 6.0E+04 Elapsed days M (Bq) A0 (Bq) A0 (Bq) A0 (Bq) A0 (Bq) 5.0E+04 4.0E+04 0.753 7800 2.89E+04 5.57E+04 8.02E+04 6.50E+04 3.0E+04 2.075 5900 2.20E+04 3.69E+04 3.03E+04 4.92E+04 2.0E+04 1.0E+04 5.04 4200 2.06E+04 3.23E+04 2.31E+04 4.67E+04 0.0E+00 0 2 4 6 8 10 12 14 13.09 2400 2.51E+04 4.00E+04 2.92E+04 5.58E+04 Time after Intake (days) Mean 2.41E+04 4.12E+04 4.07E+04 5.42E+04 Function-54 Function-78 Table-54 Table-78 Statistical Comparison SD 3.66E+03 1.02E+04 2.65E+04 8.19E+03 %SD 15.18 24.65 65.19 15.12 Table 3: I-131 Intake (A0) by subject “B” Comparison of Subject "B" Intake using the Tables & Measured Activity (M) Function-54 Table-54 Function-78 Table-78 Retention Functions in ICRP 54&78 Puplications 1.0E+06 Elapsed days M (Bq) A0 (Bq) A0 (Bq) A0 (Bq) A0 (Bq) 9.0E+05 8.0E+05 0.07 43770 7.92E+05 - -8.85E+05 - 7.0E+05 Intake (Bq) 0.94 94390 3.37E+05 6.74E+05 7.74E+05 7.87E+05 6.0E+05 5.0E+05 6.17 59690.0 3.26E+05 4.97E+05 3.63E+05 7.28E+05 4.0E+05 3.0E+05 21.11 17200 3.80E+05 4.91E+05 4.67E+05 8.60E+05 2.0E+05 1.0E+05 Mean 3.48E+05 5.54E+05 5.35E+05 7.92E+05 0.0E+00 Statistical 0.00 5.00 10.00 15.00 20.00 25.00 Comparison SD 2.84E+04 1.04E+05 2.13E+05 6.62E+04 Time after Intake (days) %SD 8.16 18.73 39.91 8.36 Function-54 Function-78 Table-54 Table-78
    • RESULTS: RF & PIF versus Intakes Retentions Functions & Tabulated Fractions (ICRP 54&78 Comparison of Subject "A" Intake using the Tables & Publications) Retention Functions in ICRP 54&78 Puplications 9.0E+04 Intake Fracion (Bq/Bq Intake) 3.0E-01 8.0E+04 2.5E-01 7.0E+04 Intake (Bq) 6.0E+04 2.0E-01 5.0E+04 1.5E-01 4.0E+04 3.0E+04 1.0E-01 2.0E+04 5.0E-02 1.0E+04 0.0E+00 0.0E+00 0 2 4 6 8 10 12 14 0.000 2.000 4.000 6.000 8.000 10.000 12.000 14.000 Time after Intake (days) Time after Intake (days) Function-54 Function-78 Table-54 Table-78 Function-54 Function-78 Table-54 Table-78 Comparison of Subject "B" Intake using the Tables &  The steep plots’ sections of A & B resulted from Retention Functions in ICRP 54&78 Puplications the Build Up (BU) of RF & PIF. 1.0E+06 9.0E+05  The flat BU of 54RTh,B resulted in minimum 8.0E+05 7.0E+05 fluctuations to the intakes of A&B subjects. Intake (Bq) 6.0E+05  The sharp BU of 78RTh,B is due to 7854. 5.0E+05 4.0E+05  BU region results in an over estimation of Intake. 3.0E+05 2.0E+05  Intake’s trend by Retention Functions or PIF is 1.0E+05 0.0E+00 steady after the BU region and would have less 0.00 5.00 10.00 15.00 20.00 25.00 uncertainty of average. Time after Intake (days) Function-54 Function-78 Table-54 Table-78
    • CONCLUSIONS:  Over the steady region, 78RTh,B < 54RTh,B (slightly) hence gives a higher predicted Intake.  Difference between the values of RF versus PIF in each publication existed.  Values of PIF are smaller than corresponding RF in both publications i.e. resulting in higher predicted intake.  54RTh,B is less sensitive to “transfer time” and compatible with the default 0.25d value, in contrast with 78RTh,B and PIFs.  Incident with potentially high intake shall require multiple measurements (over a period of time) to establish the uptake peak, hence obtaining a reliable intake average.
    • CONCLUSIONS: (Continue….)  The predicted Intake at 2 days or less showed significant variations by both 78RTh,B and PIFs thus, suggesting a need for longer “transfer time” in which the uptake can reach its maximum and minimise the uncertainty in intake’s average.  The PIF plots of ICRP 54&78 publications follow similar trend after ~3 days of the intake.  The deviations of average intake by ICRP 54&78 ranged between 15% to 65% for subject “A”; and 8% to 40% for subject “B”. The BU contributes largely to this variations.  “Transfer time” to reach uptake maxima of subjects “A” & “B” showed one fold deviation e.g. ~2 versus 4. This may be related to different individual metabolism!!
    • References: 1. ICRP Publication 54, Pergamon Press, 1988. 2. ICRP Publication 78, Pergamon Press, 1998. 3. ICRP Publication 68, Pergamon Press, 1995. 4. ANSTO files of the subjects. 5. Mathematical Models in Biology, L Edelstein- Keshet, 1988, Random House/NY. 6. Elementary Differential Equations with Boundary Value Problems, C H Edwards, et al., 2nd Ed, 1989.
    • THANKS FOR YOUR ATTENTION QUESTIONS????????