1. 46th Annual HPS Mtg; MPM-B.31 Two Sample Preparation Methods for Measuring 3 H and 14 C in Incinerator Ash and Spent Lime Ben Edwards, Le-Xuan Thai and Dan Sprau Master's Project - East Carolina University in partial fulfillment of the requirements for the degree of MS in Occupational Safety Duke University Medical Center Division of Radiation Protection

2. 46th Annual HPS Mtg; MPM-B.32 Problem: Analyze two selected methodologies for measuring 3 H and 14 C in ash and spent lime from the incineration of low level radioactive biomedical research waste. Assess the analytical performance of each method.

3. 46th Annual HPS Mtg; MPM-B.33 Relevance Radioactive material was used in the development of every major drug discovered since 1946, and in millions of analytical, diagnostic, and therapeutic medical procedures each year in the US. Radioactive waste from this biomedical use is highly regulated. Disposal is expensive, particularly for 3 H and 14 C. Radioactive waste management dissipates biomedical research institutions' financial resources.

4. 46th Annual HPS Mtg; MPM-B.34 Relevance (cont’d) Incineration generates ash and spent lime waste. Disposal of this waste as non-radioactive requires demonstrating that the radioactive concentration does not exceed specified regulatory limits. Disposal of the ash and lime as radioactive waste is prohibitively expensive. A reliable analytical method, capable of achieving the required sensitivity, can reduce waste disposal costs of academic, industrial and government biomedical research facilities.

5. 46th Annual HPS Mtg; MPM-B.35 Performance Criteria Count time t needed, for each nuclide and material, to achieve a specified "minimum detectable concentration" [MDC] based on the regulatory constraints

6. 46th Annual HPS Mtg; MPM-B.36 MDC Formula MDC = [2.71+4.65(R B xt)½]x[60xExMxYxt] -1 R B = Background count rate in counts minute -1 (cpm) t = Background & gross count time (minutes) E = Counter efficiency (counts/disintegration) M = Sample mass (g) 60 = disintegrations minute –1 [dpm] per Bq of activity Y = fraction of chemical yield, if applicable Gollnick (1994)

7. 46th Annual HPS Mtg; MPM-B.37 Target MDC Specified regulatory limits: 37 Bq g -1 for 3 H 1.1 Bq g -1 for 14 C [10 CFR 20 App. B Table 2 Column 2; PG 8-10 (1997)] Per Fong and Alvarez (1997), set target MDC at 1/10 of regulatory limit; target MDC: 3.7 Bq g -1 for 3 H 0.11 Bq g -1 for 14 C

8. 46th Annual HPS Mtg; MPM-B.38 Specific Activity [C] Formula C = (S - R B )Y (E M) -1 S = sample [gross] count rate (cpm) R B = Background count rate (cpm) Y = sample yield E = counting efficiency (dpm/cpm) M = sample mass (g)

9. 46th Annual HPS Mtg; MPM-B.39 Available Methods Oxidation - combustion of the solid sample in an oxygen-rich environment; drives off the 3 H as HTO vapor and the 14 C as 14 CO 2. These gaseous combustion products are then captured in separate collection vials for liquid scintillation counting. Gel Suspension - the powdered solid sample material is suspended in a gel- forming liquid scintillation counting solution.

10. 46th Annual HPS Mtg; MPM-B.310 Measurement Results 3 H (Bq g -1 ) 14 C (Bq g -1 ) Material/MethodMeanStd. Dev. MeanStd. Dev. Ash/Oxidizer 32.413.30.740.47 Ash/Gel 0.60.30.800.07 Lime/Oxidizer 13.30.70.240.04 Lime/Gel 8.10.50.570.07

11. 46th Annual HPS Mtg; MPM-B.311 Time to Achieve MDC 3 H Count Time a (minutes) 14 C Count Time b (minutes) Ash/Oxidizer < 179 Ash/Gel 227559 Lime/Oxidizer <177 Lime/Gel 221175 a 3 H MDC = 3.7 Bq g -1 b 14 C MDC = 0.11 Bq g -1

12. 46th Annual HPS Mtg; MPM-B.312 Conclusions Both methods easily achieve 3 H MDC Only oxidizer achieves 14 C MDC in less than 2 hours; gel takes 126 hours for ash & 26 hours for lime Gel method fails to detect 95+% of 3 H in ash

13. 46th Annual HPS Mtg; MPM-B.313 Sampling Campaign (n=30) NuclideMaterialMethodSample (g) Count t (minutes) 3H3H AshOxidation0.520 14 C AshOxidation0.5180 3H3H LimeOxidation0.520 14 C LimeOxidation0.5180 3H3H AshGel0.1180 14 C AshGel0.1180 3H3H LimeGel0.1180 14 C LimeGel0.1180

14. 46th Annual HPS Mtg; MPM-B.314 3 H MDC vs count time Count time (minutes) Desired MDC (3.7 Bq g -1 ) MDC (Bq g - 1 )

15. 46th Annual HPS Mtg; MPM-B.315 14 C MDC vs count time MDC (Bq g -1 ) Desired MDC (0.11 Bq g -1 ) Count time (minutes)

16. 46th Annual HPS Mtg; MPM-B.316 Error Propagation If x, y, z, … are directly measured variables for which we know the standard deviations  x,  y,  z,…, then the standard deviation for any quantity u derived from these counts can be calculated from:  u ² = (  u/  x)²  x ² + (  u/  y)²  y ² + (  u/  z)²  z ² + … where u = u(x, y, z, …) is the derived quantity. Knoll (1989)