Radioprotection 61-2 | Page 103

172 N. Blanchin et al.: Radioprotection 2026, 61( 2), 171 – 177

Table 1. Uranium bioassay results of the involved worker.

* The compliance criteria for urine analyses are: the volume must be greater than 500 ml and the urinary creatinine concentration must be greater than 0.5 g / L( Recommendation 32 � SFMT, 2011). ** The compliance criteria for feces analyses is based on an ash weight greater than 1 g / 24 h( Recommendation 31 � SFMT, 2011).

upper values( 0.034 mg / l, equivalent to 0.9 mBq / l) found in the French population in the ESTEBAN study over the period 2014-2016( Esteban study, France 2024)

The isotopic ratio U 234 / U 238 in this analysis was 1.2, consistent with natural isotopy. The same Recommendation 54( SFMT, 2011) defines natural isotopy as an isotopic ratio U 234 / U 238 below 2.

Simultaneously, a radiotoxicological analysis of 24-hour feces samples was conducted, yielding a result of 19.4 mBq. Current best practice guidelines( SFMT, 2011) use 45 mBq / 24 h as the reference value for activity linked to dietary intake. This result therefore falls within the normal range observed in the general population( see Tab. 1).

Furthermore, it should be noted that the analysis results for plutonium and americium in the same samples are below the laboratory’ s usual detection limits( 0.2 mBq for 24-hour urine and 1 mBq for 24-hour feces samples).

3 Further information from the employee

Following these initial results, the employee was examined by the physician for information gathering and an interview: 1 Regarding any possible contamination event that may have occurred since the previous“ normal” analysis.

2 Regarding his dietary habits, in particular the type of mineral water consumed or the use of a well( Mineral water and radioactivity Technical report, 2000) as well as the intake of certain clay-based medications, which are widely used by the general population in cases of diarrhea. The employee was also questioned about the consumption of mushrooms or wild plants known to concentrate certain elements, including uranium.

Regarding the first, professional aspect, no specific event could be identified by the employee. However, this issue will require further investigation by the radioprotection teams( see paragraph 5).

Regarding the consumption of mineral water, the employee states that he only drinks tap water. It should be noted that a survey conducted on a control population of workers at Cadarache from 2001 to 2011( Blanchin et al., 2013; Davesne et al., 2014) showed a very high variability in urinary and fecal excretion, both between individuals( inter-individual) and for the same individual from one analysis to another( intraindividual). Out of approximately 600 urine analyses, nearly 90 % of the results were below the detection limits at the time( between 1 and 3 mBq), and it was found that the Cadarache population did not differ from the French reference data. This is not surprising given the predominantly limestone nature of the soil in Provence, which results in low uranium concentrations in the soil and consequently in tap water.

Finally, the employee informed us that he is neither a hunter nor a gatherer of mushrooms or wild herbs, and furthermore, he is not undergoing any treatment, particularly for digestive issues.

Given these initial findings, the physician decided to schedule more frequent radiotoxicological tests in order to support a possible occupational origin.

Furthermore, the radiotoxicological analysis results of all employees working on the same sites as Mr CC were carefully reviewed. No similar findings were observed.

4 Additional investigations

The results of the radiotoxicological samples are presented in Table 2 below. LOD means“ limit of detection” and is the lowest measurable activity.

The date of 11 / 04 / 2016 corresponds to the last test result below the laboratory’ s detection limits and therefore represents the potential start date of exposure, which is the most unfavorable scenario from a dosimetric perspective.

It is observed that all 24-hour urine radiotoxicological analysis results from July 2016 onwards are significantly higher than the values seen in the general population and those considered to be related to dietary intake.

Conversely, over the same period, all 24-hour feces radiotoxicological analysis results fall within the normal range for the general population.

5 Interpretation of results and provisional dosimetric estimate

Given the absence of any indications of possible contamination, two scenarios were considered: an acute occupational inhalation or a chronic dietary ingestion.

First scenario: This is the default scenario, involving acute inhalation exposure that occurred on 12 / 04 / 2016( the date of the previous analysis < LOD) to a uranium oxide compound, type S, according to the " inhalation " model of ICRP 78( Marsh et al., 2007), which was the reference biokinetic model at the time( see Fig. 1)

The curves are generated by the IMBA software( Birchall et al., 2006): – The blue points correspond to the measured values in urine on the upper graph and in feces on the lower graph. The measured values are associated with an uncertainty value defined by the scattering factor( SF)( Marsh et al., 2007)). IDEAS Guidelines( Castellani et al., 2013, 2016)