Radiation protection of the environment and economy in the construction of thyroid gland cancer therapy wards

There are basically three methods for the retention of radioactive patient effluents: 1. Separate retention of faeces and treatment in decontamination systems, decay tanks etc. and direct passing of patients' washing water into the drains because of supposedly low residual activity of the washing water. 2. Separate collection and storage of falces and washing water of the patients. Reduction of the required storage capacity be re-using the collected washing water as flushing water for the cancer patients' toilets. 3. Collection of all waters (faeces and washing water). This method requires a relatively large storage capacity of the decay system. In our hospital (24 therapy beds, up to 50% are cancer patients), we found out by measurement that with cancer patients for treatment in hospital 4-5% of the radioactivity applied is found in the patients' washing water. This implies that the limit value set by the Radiation Protection Ordinance area alone are exceeded by several orders of magnitude. The collection of faeces without retention of washing water makes little sense. On the other hand, the collection of all waters leads to a significant expansion of the collecting capacity which increases the cost for the enclosed area of the system. Measurements and estimates of the radioactivity release with waste air show that without retention system about 0.5per mille of the radioactivity received are released with the waste air. Taking the specific concentration of radioactive waste air as a basis, this value exceeds the limit values of 9 pCi/m3 for waste air stipulated in the Radiation Protection Ordinance by 1 to 2 orders of magnitude. (orig./HP)