Situation on exposure of workers due to use of industrial NORM in Japan

Transcription

1 Situation on exposure of workers due to use of industrial NORM in Japan Hidenori Yonehara, Kazuki Iwaoka National Institute of Radiological Sciences,JAPAN

2 Status on use of NORM for industrial raw materials and consumer goods in Japan Japan is deficient in natural resources Mines except those for limestone have been closed Various industrial raw materials imported - Monazite - Phosphate ore - Titanium - Bastnaesite - Zircon - Coal - Samarium

3 Exemption level of NORM under current legislation system in Japan NORM is regulated by the law for the Regulations of Nuclear Source Material, Nuclear Fuel Material and Reactors from the view of nuclear security. Regulatory criteria of Nuclear Fuel Material - amount of natural uranium: 300 g - amount of depleted uranium: 300 g - amount of thorium: 900 g Regulatory criteria of Nuclear Source Material - radioactive concentration: 74Bq/g (liquid or gas) or 370Bq/g (solid) - amount of uranium and thorium (*) : 900 g (*) the sum of the amount of thorium and 3 times of the amount of uranium

4 Principle for regulation of NORM in Japan Report published in 2003 by Administrative Group of the Radiation Council of Japanese Government Necessity of radiation protection radiation risk from NORM is same as that from artificial source NORM has been used since early times existing source is subject to Intervention Classification according to degree of artificiality or amenability is necessary for appropriate regulation Activity concentrations are widely distributed from very low level to high level Because of difficulty in setting exemption level, Regulation according to the dose criteria provided in ICRP Publ. 82 as intervention exemption level (1mSv/y)

5 Guideline for Ensuring Safety of Raw Materials and Products Containing Uranium or Thorium Manufacturers and importers who handle certain amount of designated raw materials (*) or products made from these materials are target manufacturers and importers of the Guideline specified raw materials means ores containing uranium or thorium such as Monazite, Bastnaesite, Zircon. Requirements for voluntary control of the exposure: - Measurement of radiation dose rate at 1m from raw materials products, etc. and evaluate 1-year exposure dose of workers, local residents or users. - If the dose excess 1mSv/y, measures to reduce radiation exposure are to be requested.

6 Industrial raw materials subject to future regulatory control as NORM in Japan Materials Amount of import (ton/a) Typical concentration (Bq/g) 238 U 232 Th Purpose of industrial use Average dose of workers roughly estimated (msv/a) Monazite Several tens (in the past) Consumer goods 0.3 Zircon 78,000 (in 2005) Bastnaesite 2,000 (in 2003) Refractory Abrasive 0.4 Titanium ore 510,000 (in 2005) Titanium Phosphate ore 770,000 (in 2005) Fertilizer 0.28

7 Radon spa in Japan Dose rate from terrestrial radiation sources Iida 9kBq/L Misasa 2-10kBq/L 48 Ikeda 24-90kBq/L Sarugajyou 10kBq/L Yunoshima (Ena) 5-8kBq/L Masutomi 160kBq/L Lacco Ameno (Italy) 37kBq/L Therma(Greece) 10kBq/L Brambach(Germany) 30kBq/L Badgastein(Austria) 1-4kBq/L

8 Misasa Spa The amount of radium (actually, radon) contained in the water has made Misasa hot springs world famous. This water is said to be effective for treating deseases such as rheumatism, neuralgia gastroenteric troubles, cutaneous and other disorders.

9 Consumer goods Apparatus aiming for beneficial health-effect Bottle for delicious water For radon spa in home bath Radon spa bathing apparatus Athletic supporter

10 Monazite Imported tens of tons/y in the past from India, Vietnam, Malaysia, South Africa Sandy monazite is crushed to use raw materials for health products, paint and spa bathing apparatus Monazite sand 238 U: 40Bq/g, 232 Th: Bq/g Dose rate in typical work place :0.75µSv/h Estimated effective dose :1.6 msv/y (360 hour work at product fabrication place)

11 Study on exposure of workers in NORM industries Dose evaluation in previous investigation was not accurate because method of dose estimation used a conservative value of dose rate in the site and parameters related to dose estimates. Investigation of range of the actual doses of different types of individual workers Both external and internal exposure including radon exposure were considered according to new BSS

12 Different types of factory for refractory using zircon Unshaped refractory plant Shaped refractory Plant Electrocast refractory plant

13 NORM Zirconium ore Estimated effective dose of workers in various NORM industries Type of plant investigated Factory for unshaped refractory Factory for shaped refractory Factory for electrocast refractory Range of annual effective dose of workers (msv/a) External and internal exposure Only external exposure Using Without mask mask Monazite Titanium ore Factory for consumer products Storage for residue

14 Dose estimation (external and internal) of workers in various NORM industries 10 Estimated annual effective dose (msv/a) 1 0,1 0,01 0,001 0,0001 0,00001 Titanium Zirconium Monazite External Total with mask Total without mask

15 Activity concentrations of NORM in consumer goods Samples U-238 Th-232 Bq/g Bq/g Refractory brick Thoriated Tungsten Electrodes Muffler catalyst Phosphate fertilizer Abrasive Ship bottom paint pigment Sinter or mineral encrustations left by hot springs Fly ash for cement Measured by ICPMS

16 NORM Database:NIRS

17 Data for activity concentration in more than 900 materials of natural source, industrial products and consumer goods from NORM industries

18 Information of activity concentrations from literatures and results of actual Measurements Industrial raw materials ICPMS Ge detector U Th Activity Concentration U Th Series K-40 Activity concentration

19 Summary NORM Regulation by legislation system is not established sufficiently in Japan. Dose to workers in various NORM industries has wide range. Effective doses of workers due to handling of NORM are less than 1 msv/a in most.

20 Thank you for your kind attention!