[Activation of solid materials in a medical linear electron accelerator]. / Aktivierung fester Materialien an einem medizinischen Elektronenlinearbeschleuniger.

Using the medical linear electron accelerator SL 75/20 supplied by Philips and employing a radiation time of 15 minutes with the 16 MeV high-energy photon stage, we measured the radioactivities induced by photons and neutrons, at the output elements (target, compensator body, wedge filter, diaphragms), at the positioning table of the patient and at a barium oxide concrete wall, via Ge(Li) spectrometry. The resulting local dose rates were determined. The radioactivity that is mainly caused by the nuclides W 187, Sb 120, Cu 64, Cu 62, Ni 57, Mn 56, Al 28, Mg 27 and Al 26 m results (with the exception of the target) in a local gamma-Dose rate of the order of 10 mu Sv/h, respectively. beta radiation, however, is expected to markedly increase these values. The total dose rate of 15 mSv/h in the target region, which retains this indeed rather high level even 7 minutes after radiation has been discontinued, makes it imperative to control the local dose rate and if necessary--depending on the irradiation conditions--to introduce waiting times of several hours if manipulations in this area have to be performed.

[Radioactivity in dismantling a betatron]. / Radioaktivität beim Abbau eines Betatrons.

The authors report on the specific radioactivity of construction components of a 42 MeV betatron measured 28 days after the last run by means of a Ge spectrometer (ultra-pure germanium detector employed in a semiconductor spectroscopic method) recording the gamma spectra of various components of the betatron. This examination served to find out which components would have to be considered as radioactive waste requiring special treatment in accordance with Federal German legislation on radioactive waste disposal (section 47 of the Radiation Protection Ordinance). The examination showed that such special treatment would be required only for the target (main material: platinum) and the Platness-filter (chief constituent: lead) of the decommissioned electron accelerator.

[Comparison between 2 methods of determining photon-induced air activity around medical accelerators]. / Der Vergleich zweier Methoden zur Bestimmung der photoneninduzierten Luftaktivität an medizinischen Beschleunigern.

The authors compare two different methods to determine the activity of the air induced by the bremsstrahlung of medical accelerators. The activities of the air resulting from maximum photon energies of 16 to 42 MeV are measured with a proportional counter tube ("direct measurement") and by means of activation analyses of imidazole, triazole, malonic acid, and urea specimens ("indirect measurement"). The results are compared.