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» WP4: Infrastructures »  Irradiation Facilities


Irradiation Facilities of DoReMi partners

There are, in total, 45 irradiation facilities distributed amongst DoReMi partners. Most DoReMi partners can provide access to at least one installation for radiobiology studies, although a few institutions are not equipped.
France is equipped with the largest number of facilities followed by Belgium, Finland and Germany.

Distribution of irradiation facilities amongst DoReMi partners by country

In terms of radiation types, most types are well represented in the facilities, with a predominance of photons (either gamma photons [21 facilities] or X-photons [11 facilities]. Of note, there are four sites which offer the possibility to carry out internal contamination studies, although one of these is slated to be closed in the near future.

Distribution of radiation types amongst DoReMi partners

Faculties offering different radiation types are available in some countries, most notably France, Belgium, Finland, and Germany.

Distribution of radiation types by country

Low dose/low dose rate facilities below 0.1 Gy and/or 0.1 Gy/min are available in France, Italy and Belgium.

Facilities for low dose and low dose rate studies (< 0.1 Gy, < 0.1 Gy/min)

Very low dose/low dose rate facilities below 0.01 Gy and 0.01 Gy/min are available in France, Italy, Belgium, the UK,Sweden, Norway and Japan.

Facilities for very low dose and dose rate studies (< 0.01 Gy, < 0.01 Gy/min)

Access to these facilities is available to radiation biologists within and outside of DoReMi, pending approval of a submitted proposal.  For further information please contact the infrastructure helpdesk.

Facilities for retrospective radon and thoron dosimetry

In the framework of Task 4.10. of DoReMi, a facility for retrospective measurements of radon and thoron by CDs/DVDs and their quality assurance/calibration is currently being established at Sofia University ””St. Kliment Ohridski”, Sofia, Bulgaria. The infrastructure includes a laboratory for procesing CDs/DVDs and a calibration facility for exposure of CD/DVDs to radon and thoron (see Fig. 1). The laboratory is supplied with systems for chemical pre-etching and electrochemical etching, specificallyy designed for etching alpha-tracks in disks (Fig. 2) and equipment for automatic track counting (Fig. 3). Its projected capacity is about 50 disks per day. The calibration facility is intended to provide fast and precise calibration of CD/DVDs. It will allow exposures to a wide range of radon and thoron activity concentrations (from several kBq.m-3.h to several hundred MBq.m -3.h) and could potentially be used for exposure of other radon/thoron detectors. To provide controlled exposure conditions, the facility will utilise certified radon and thoron sources, reference radon and thoron monitors, hermetic exposure chambers and a system for temperature control. Calibration procedures with a focus on precise measurements for the aims of epidemiological studies will be developed, such as procedures for individual aposteriori calibration of each disk. Upon completion of the task, a ready for use infrastructure and methodology for retrospective assessment of the indoor radon/thoron activity concentrations will be available.

Fig. 1 Calibration facility for a posteriori calibration of CDs/DVDs Fig. 2 A system for electrochemical etching of CDs/DVDs loaded with discs Fig. 3 Scanning and atomatic counting of ECE tracks in CDs/DVDs
Examples of scientific studies that can be performed with this infrastructure are:
  • Large-scale studies based on retrospective radon measurements by the CD/DVD method
  • Retrospective dosimetry of radon/thoron as confounders in other radiation risk studies (e.g. epidemiology studies of nuclear workers etc.) related to lung cancer and possibly, leukemia
  • Exposures of detectors to known radon/thoron concentrations for calibration of radon measurement detectors, study of the sensitivity of radon detectors to thoron, development of radon/thoron measurement techniques, etc.
Retrospective radon and thoron measurements from CDs/DVDs
  • A single CD or DVD allows retrospective evaluation of the exposure to both radon and thoron. Until recently, no method for retrospective thoron measurements has been reported in the literature. The method allows very precise retrospective radon measurements with typical uncertainty of better than 25% and covers the entire range of indoor radon concentrations (from several to several hundred thousand Bq /m3).
  • The signal related to radon (alpha tracks inside the disk) is not influenced by radon and thoron progeny behavior in air, by humidity and smoke, or by the storage mode of the disks (in boxes, envelopes, bare, etc.). The influence of temperature is typically within 10 % and could be corrected for.
  • Two disks of different age could be used to detect significant past changes in radon concentration, due for example, to radon mitigation, energy-efficient reconstructions, etc.
  • Surveys could be organized remotely, e.g. by sending the disks by mail. Prospective measurements based on disks could be organized much faster with no wait-time for exposure of new detectors.
Short description of the methodology:

The method for retrospective radon measurements employs the high radon absorption ability of the polycarbonate material of commercial CDs/DVDs and is based on the following: Before gathering them for analysis, the polycarbonate specimens (e.g. CD, DVD) are exposed to radon at the studied home. During exposure, 222Rn atoms are first trapped on the polycarbonate surface and then diffuse further in depth. After decay, they emit alpha particles and give birth to decay products, two of which (218Po and 214Po) are alpha emitters and have the same volume distribution as that of 222Rn. For a polycarbonate specimen placed in a radon-containing atmosphere, one can distinguish “external” and “internal” alpha sources (see Fig. 4). “External” to the plastic volume are alpha particles coming from the ambient radon, thoron and their progeny, as well as those from the progeny atoms deposited on the surface of the disk (plate-out). The “internal” source is the absorbed 222Rn and its progeny. After exposure, we remove a sufficiently thick layer from the surface and electrochemically etch the alpha tracks at that depth. Figure 5 shows an etched part of a CD and Fig. 6 shows a microscope image of etched tracks in the CDs.

Fig. 4 Sources of tracks beneath
the CD/DVD surface
Fig. 5 A part of electorchemically
etched CD
Fig. 6 Snapshot of ECE tracks
in CDs

The “external” sources are highly variable and depend on the particular behavior of radon and thoron progeny in the ambient air and close to the surface. If the removed layer is thicker than 76 μm (usually about 80 μm are removed), none of the alpha particles from the external sources can reach the etched depth and the signal is related only to the absorbed 222Rn. To evaluate the concentrations of both radon and thoron two pieces of the disk are analyzed. Thoron is not absorbed in the disk, due to its short half-life. It can be detected by the alpha tracks formed by its daughter 212Po, deposited on the disk surface and on the inside of the disk packaging. These alpha particles have the highest energy among other “external” sources and form tracks at the highest depth. In the interval 64-76 μm below the disk surface, the signal is due only to 212Po and absorbed radon (see Figure 4). The radon signal at these depths can be subtracted using the signal at a depth > 76 μm (determined by processing the first piece of the disk). Alternatively, the foil-covered side of the disk, which is radon tight, can be used to obtain a pure thoron-related signal. For thoron measurements only disks exposed in their packaging are used, since the packing could provide fixed geometry of the 212Po source. The full capability of the CD/DVD method for retrospective thoron measurements is under study.