Lessons learned from the surveillance: Measuring methods and monitoring strategies

1. Lessons learned from the surveillance:Measuring methods and monitoring strategies T. R. Beck, E. EttenhuberFederal Office for Radiation Protection, Germany

2. Content —General Principles of Radiation Protection Monitoring — Natural Radiation at Workplaces: Present Status in Europe — Measuring Quantities and Assessment of Effective Dose — Monitoring Approaches

3. General Principles of Radiation Protection Monitoring Aims: — Verification of compliance with the limits specified for workers — Providing information for optimization of radiation protectionandsafety Requirements — Monitoring of workers (individual monitoring) should be made systema-ticallyand based on individual measurements — In cases within which individual measurements are impossible or in-adequatethe individual monitoring should be based on an estimatearrived at eitherfrom individual measurements made on other exposedworkers or from resultsof the workplace monitoring —

4. Natural Radiation at Workplaces: Present Status in EuropeESOREX www.esorex.cz

5. Natural Radiation at Workplaces: Present Status in EuropeESOREX www.esorex.cz Countries: AT, CZ, DE, NO, RO, SE, SI, UK

6. Radon at Workplaces: Present Status in EuropeEURADOS working group on „Harmonisation of Individual Monitoring in Europe“ — Action levels:Underground workplaces, industry, waterworks: 400 - 1000 Bq·m-3Offices, schools, day-care homes: 200 - 500 Bq·m-3 — Monitoring strategies:In most countries both individual and workplace monitoring are authorized. — Measuring period:Finland: 2 months; Germany: 1 - 3 months — Instrumentation:Diffusion chambers using SSNTDElectretsVarious electronic instruments for continuous and grab samplingIn a few countries exposures to radon decay products are measured in mines. — Results published in: Lopez, M. A. et al: Workplace monitoring for exposures to radon and other natural sources in Europe: Integration of monitoring forinternal and external exposures. Radiation Protection Dosimetry (2004), Vol. 112, No. 1, pp. 121-139

7. Radon at Workplaces: Present Status in EuropeEURADOS working group on „Harmonisation of Individual Monitoring in Europe“ In Europe no workplaces with elevated exposures causedby thoron exist. No Thoron !

8. a a b- b- a Measuring Quantities and Assessment of Effective Dose short-lived Radon Decay Products Potential Alpha Energy: The total alpha energy emitted during the decay of a short-lived radon decay product along the decay chain up to Pb-210.

9. Measuring Quantities and Assessment of Effective Dose — The exposure of the lung caused byinhalation of short-lived radon decayproducts is the risk relevant quantity! — Doses to other organs (skin, eye,extremities) are not relevant. —

10. Measuring Quantities and Assessment of Effective Dose: Methods of Measurement Measurement of Exposure to Radon Decay Products Relation to dose direct measurement of the risk relevant quantity Quantity Potential Alpha Energy Exposure Instruments electronic with active air sampling Advantages/Disadvantages direct relation to doselower uncertainty of dose assessment high costs of instruments high expenditure of maintenance —

11. Measuring Quantities and Assessment of Effective Dose: Methods of Measurement Measurement of Exposure to Radon Relation to dose no direct; radon equilibrium factor is to be estimated Quantity Exposure to radon Instruments electronic and passive (e.g. diffusion chambers) Advantages/Disadvantages passive instruments: cost-effectiveness, robust,and available in high quantities no direct relation to dosehigher uncertainties of dose assessment —

12. Measuring Quantities and Assessment of Effective Dose: Calculation of the Effective Dose Effective Dose D = Conversion to Dose x Measurement of Exposure to Radon Decay Products PotentialAlpha Energy Exposure PP

13. Measuring Quantities and Assessment of Effective Dose: Calculation of the Effective Dose Effective Dose D = Conversion to Dose x Measurement of Exposure to Radon Decay Products PotentialAlpha Energy Exposure PP

14. 96/29/EURATOM: The conversion factor effective dose per unit potential alpha energy exposure is mSv 1.4 for radon at work. mJ·h·m-3 Measuring Quantities and Assessment of Effective Dose:Dose Conversion Convention ICRP 65: An exposure to radon decay products of 1 mJ·h·m-3 is equivalent to an effectivedose of1.43 mSv for workers.

15. Measuring Quantities and Assessment of Effective Dose:Dose Conversion Convention Note! Conversion convention based on epidemiological studies on miners toradon (ICRP 65). The dosimetric model (ICRP 66) is not used for dose assessment ofworkers and should be not adopted in legal regulations.

16. mSv ________ 3.1 Effective Dose D MBq·h·m-3 = Conversion to Dose x Measurement of Exposure to Radon Decay Products PotentialAlpha Energy Exposure PP Measuring Quantities and Assessment of Effective Dose: Calculation of the Effective Dose = Transformation Coefficient5.56 ·10-9 J·Bq-1 x Equilibrium Factor F = 0.4 Measurement of Exposure to Radon x Exposure to Radon PRn

17. Measuring Quantities and Assessment of Effective Dose: Calculation of the Effective Dose Effective Dose D = Conversion to Dose x Measurement of Exposure to Radon Decay Products PotentialAlpha Energy Exposure PP = Transformation Coefficient5.56 ·10-9 J·Bq-1 x Equilibrium Factor F = 0.4 Measurement of Exposure to Radon x Exposure to Radon PRn

18. Measuring Quantities and Assessment of Effective Dose:Variation of Equilibrium Factor Lognormal distribution: µLF = ln(0.4) L,F = 0.295 Variation of the equilibrium factor at a 95% confidence interval: 0.2 to 0.7 Distribution of the radon equilibriumfactor in homes and at workplaces

19. ! Uncertainty of dose assess-ment up to a factor of 2 Measuring Quantities and Assessment of Effective Dose:Accuracy of Dose Assessment using passive Instruments Accuracy Criteria for Radon Measurements: Near the Relevant Limit an Accuracy of 20% is required Overestimationnot more than a Factor of 1.5

20. Measuring Quantities and Assessment of Effective Dose:Accuracy of Dose Assessment using passive Instruments Results of the 2005 Intercomparison for Solid State Nuclear Track Detectors

21. Monitoring Approaches: Individual Monitoring Indication for Application • Doses may represent a significant fraction of dose limits • Workers with frequently changing workplaces or inhomogeneous exposure conditions

22. Monitoring Approaches: WorkplaceMonitoring Individual monitoringof a subset of the group Localinstruments Indication for Application • Workers with similar work patterns and exposure conditions • Unlikely to receive doses approaching dose limits • Detailed records of the duration spent at each work location

23. Conclusions Using passive radon instruments for monitoring of workers exposed to radon should be recommended. • Passive instruments are cost-effective, robust, can be applied in different exposure conditions. • Individual measurements are possible. • Quality assurance and maintenance of the instruments are undertaken by a radon service. • Employer has low expenditure in managing the monitoring.

24. Conclusions Under special circumstances the direct measurement of potential alpha energy exposure is recommended: • Dose estimations give rise to doses approaching dose limits • Information on the equilibrium factor are not available • The mean equilibrium factor is lower or higher than defined values

25. Conclusions Generally individual monitoring and workplace monitoring may be used as synonymous alternatives. At special work patterns or exposure conditions one of the approaches is indicated.