Natural activity and inhalation problems Wim Erkens (Thermphos) Electro-thermal elemental phosphorus production and workplace related affairs with natural radionuclides Natural activity and inhalation problems Wim Erkens (Thermphos) wim erkens Thermphos International BV 1/6/18

Overview Process Enrichment and surface contamination Measurement technique (inhalation) Measurement results Classification as exposed workers Risk communication Conclusions wim erkens Thermphos International BV 1/6/18

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Use of elemental phosphorus and derivates wim erkens Thermphos International BV 1/6/18

Phosphorus slag leaving the furnace into a pan wim erkens Thermphos International BV 1/6/18

The pan is being emptied wim erkens Thermphos International BV 1/6/18

The pan is being emptied wim erkens Thermphos International BV 1/6/18

The material is being removed from the slag beds after cooling and elaborated wim erkens Thermphos International BV 1/6/18

, The hydraulic slag mixture is used in road construction wim erkens Thermphos International BV 1/6/18

The hydraulic slag mixture is being spread wim erkens Thermphos International BV 1/6/18

A top layer is being applied wim erkens Thermphos International BV 1/6/18

Surface contamination inside equipment Up to hundreds of Bq per cm2 surface contamination inside equipment Work which disperses this contamination can cause a dose rate of approximately 1 mSv per hour Breathing air protection measures are necessary wim erkens Thermphos International BV 1/6/18

Safety procedures Entering process vessels, furnaces etc: < 0.25 Bq per cm2 : no measures > 0.25 < 10 Bq per cm2 : half mask (PF10) > 10 Bq per cm2 : full face mask (PF 100-500) wim erkens Thermphos International BV 1/6/18

Mask with a sturdy construction and broad flexible sealing edge wim erkens Thermphos International BV 1/6/18

PF: laboratory conditions 50 PF: BS 20 PF: Dutch Labor inspectorate 10 Protection factor: PF: laboratory conditions 50 PF: BS 20 PF: Dutch Labor inspectorate 10 wim erkens Thermphos International BV 1/6/18

Full face mask with remote air supply wim erkens Thermphos International BV 1/6/18

Improvements (dose reduction) New floors which can be cleaned easily Central vacuum cleaner Process automation Continuous cleaning operations Slag beds removed from furnace building Improved ventilation (iron beds) Measurement programs Breathing air protection measures (procedures) wim erkens Thermphos International BV 1/6/18

Measurement technique Air sampling: 120 litre per h through filter Activity on filter is measured Calculation of the activity in the air Bq/m3 Dose estimation: breathing rate : 1.2 m3 per h activity in the air DCC: Sv per inhaled Bq (particle size dependent) Annual dose based on 1600 hours wim erkens Thermphos International BV 1/6/18

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Air pump and IOM filter holder with filter wim erkens Thermphos International BV 1/6/18

Monodisperse approach with LUDEP (GSD 1, no distribution): No AMAD Aerodynamic Median Activity Diameter Geometrical Standard Deviation wim erkens Thermphos International BV 1/6/18

A joint measurement setup comprising various measuring devices wim erkens Thermphos International BV 1/6/18

Industrial hygienic approach wim erkens Thermphos International BV 1/6/18

The inside of a cyclone wim erkens Thermphos International BV 1/6/18

Cascade-impactor wim erkens Thermphos International BV 1/6/18

Collection efficiency % Cascade impactor wim erkens Thermphos International BV 1/6/18

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Cascade-impactor: the first separation stage wim erkens Thermphos International BV 1/6/18

Cascade-impactor: the third separation stage wim erkens Thermphos International BV 1/6/18

Cascade-impactor: the seventh separation stage Dust that can reach the deepest parts of the lung wim erkens Thermphos International BV 1/6/18

Dust producing for tests wim erkens Thermphos International BV 1/6/18

Dust producing for tests wim erkens Thermphos International BV 1/6/18

The thoracic cyclone approach wim erkens Thermphos International BV 1/6/18

Conclusions measurement technique Determination of dust distribution is a prerequisite for correct inhalation dose assessment However: not simple: cascade impactor Thoracic cyclone as a practical approach wim erkens Thermphos International BV 1/6/18

Measurement results Comparison ICRP30 ICRP66 lung models with IOM filter holder and with thoracic cyclone Between brackets: cleaning operator Method Dose Sinter plant N CI90% +/- Dose Furnace ICRP30 (1993-’97) 0.4 (1.6) 20 <0.2 1.3 (1.8) 68 ICRP66 IOM (1998-03) 1.14 (2.29) 71 (24) 0.8 (1.71) 100 (25) ICRP66 Thoracic 2004 0.44 (0.45) 21 (5) 0.27 0.34 (0.38) 30 (4) 0.28 wim erkens Thermphos International BV 1/6/18

Exposed workers legislation Based on directive 96/29/EURATOM and Dutch law. Above 1 mSv per year Category B Above 6 mSv per year Category A Based on this law and the result of the dose measurements Thermphos classified the workers to exposed workers (300 people involved in phosphorus production) wim erkens Thermphos International BV 1/6/18

Consequences classification No extra medical examination Dose monitoring system Reporting the dose to NDRIS National Dose Registration and Information system Dose is reported to the workers (they knew about the radioactivity approximately 15 years) wim erkens Thermphos International BV 1/6/18

Workers information They received comprehensive information on dose and risk on their home address. A risk comparison is given to them Going to work Working activities Smoking cigarettes (the greatest risk) Dose risk in perspective accepted risks wim erkens Thermphos International BV 1/6/18

Workers reaction None (no unrest), But 1 person told me: “We know this whole issue of radioactivity for more then 15 years, but if you forgot to tell it to your wife, you have to explain something to her if she opens your letter with dose information” wim erkens Thermphos International BV 1/6/18

Summary Enrichment and surface contamination Measurement technique Procedures and breathing air protection measures Continuous cleaning Process improvements Measurement technique Continues study to improve the measurements Measurement results Classification as Exposed workers Risk communication To put RA-risk in perspective with “accepted risks” wim erkens Thermphos International BV 1/6/18

Conclusion Natural radioactivity in processes like our Elemental Phosphorus production cause problems in the workplace. You cannot ignore these problems from a dose point of view. However: These problems are manageable. wim erkens Thermphos International BV 1/6/18

For more information on the measurement technique a comprehensive (free) paper in PDF format is available: Erkens@thermphos.com wim erkens Thermphos International BV 1/6/18