Excretion rates of 210Po and 210Pb in Prague inhabitants

Internal radiation exposure from TENORM for workers conducting cleaning activities on equipment used at geothermal energy plant

Geothermal energy is predicted to be one of the most important renewable energy sources in the near future. In geothermal energy plants, the secondary products such as the scale containing naturally occurring radioactive material (NORM) and adhering to the surface of equipment produce radiation fields. The workers who maintain and clean such equipment are at a risk to be exposed by the technically enhanced NORM (TENORM). To estimate the risks of radiation exposure to the workers, we assessed internal doses resulting from the cleaning activities on 150 heat exchanging boards used at a geothermal energy plant, focusing on ²²²Rn, ²²⁶Ra, ²¹⁰Pb, ²²⁸Ra and ²²⁸Th. The experiment was performed with the subjects of workers and office workers as control, supplying prepared foods and drinks. Using the analytical results of ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra, and ²²⁸Th in the excretions of subjects, committed effect doses were determined. The annual internal dose for the workers with protective clothing due to the cleaning activities on removing scale, assuming the cleaning activities requires 170 h (standard monthly working time) a year, was obtained as 26 μSv/y and the total dose including ²²²Rn inhalation dose was calculated as 323 μSv/y. The additional dose for the cleaning workers was less than the dose limit of 20000 μSv/y for radiation workers, even less than for general population (1000 μSv/y) recommended by International Commission on Radiological Protection (ICRP). However, the elevated inhalation dose for workers conducting cleaning activities may present a health hazard to workers if they deal with excessive materials containing TENORM, work for excessive time or are under inappropriate safety measures.

ASSOCIATION OF 210Po CONTENT IN URINE WITH CONCENTRATION OF 222Rn IN DWELLINGS

Effect of indoor radon concentrations higher than 500 Bq m-3 in dwellings on excretion of 210Po was studied in 28 volunteers. The study was further augmented by following eight individuals from the group for 5 months at 1-month intervals. Association between 222Rn concentration in homes and 210Po excretion was found when the dataset containing values of the studied 27 subjects was combined with data on 40 Prague inhabitants from the previous study. Sources of uncertainties involved in the analysis are discussed.

Variation of ²¹⁰Po daily urinary excretion for male subjects at environmental level

(210)Po was determined in 24-h urine of seven healthy males from Prague, Czech Republic, for ten consecutive days. The results show that for each volunteer, the urinary excretion of (210)Po changed only little from day to day in the studied time period. For two volunteers, the difference in the daily excreted (210)Po activity for two consecutive days was not significant, given the 95% confidence interval (two sigma) of the activity measurements. The same is valid for the excretion data of the other volunteers, except for some days where the differences were slightly higher. The range of daily urinary excretion of (210)Po of each volunteer in the studied time period was quite narrow. Among the volunteers, the maximum daily urinary excretion value of (210)Po was at most about a factor of 2.5 higher than the lowest excretion value. An attempt to explain the observed small inter-individual variability of (210)Po excretion in daily urine is made.