Neutron measurements around an 18 MV linac.

An estimate of the neutron production of medical electron accelerators is of interest in order to quantify the radiological risk for the staff operating such machines. First, we used a theoretical procedure, based on the Montecarlo method, in order to get some information about the neutron spectrum. Second, by using the neutron activation of indium foils, we have empirically obtained the neutron fluence at different locations in the accelerator room. Finally, some post-irradiation environmental levels of radiation are given.

Measurements of 99Tc in biological samples: problems with the evaluation of radiochemical yield.

Measurements of 99Tc in vegetables have been made. The radiochemical yield is measured by tracing the process with a known amount of 99mTc. Differences in chemical behaviour of the problem 99Tc relative to the tracer 99mTc have been found under certain conditions and the way to overcome them is reported.

Radiological impact of fallout 99Tc in Seville, 1965-1967.

From 99Tc concentrations in Seville air, measured previously for a 26 month period in 1965-67, we deduce the amount of intake by inhalation and the following committed dose equivalent to the population using in different ways a compartmental model to describe clearance from the respiratory system. Extremely low values of less than 10(-2) Bq intake per year and a corresponding committed dose equivalent below the nSv are deduced.

A geometric calculation of square and circular size equivalents for rectangular radiation fields in radiotherapy.

In radiotherapy the volume of irradiated tissue is determined by the cross-section of a beam of radiation that strikes the skin of a patient. The radiation dose delivered at a given depth is a function of this cross-section, known as the radiation field. The computing of that dose for rectangular fields can be simplified using a small number of data corresponding to square or circular fields. This procedure is called the equivalent field method. Two fields are said to be equivalent if they give equal doses of radiation at a given depth in tissue. In this work the equivalent circular and square fields are determined by the condition that the solid angle subtended by the field in the skin, as viewed from the exposed point, be the same.

On the determination of 99Tc in environmental waters.

In this paper we propose a search for 99Tc in flocs from water treatment plants. We show that preconcentration of 99Tc from environmental waters is a very advantageous method because of the high volumes involved. A radiochemical method is adapted in these kinds of samples, and 99Tc is identified in them by a previously published method. A typical value found is 0.56 +/- 0.26 mBq/g, where 1 g dry floc should be related to many liters of water.

99Tc in surface air samples during the years 1965-1967.

In this work, 99Tc activities in atmospheric filters taken during the years 1965, 1966 and 1967 are measured on a monthly or bimonthly basis. The results show a clear yearly pattern of the activities with a maximum below 3 mBq/1000 m3 at the end of each summer, probably related, in a non trivial way, to meteorological factors. Our atmospheric 99Tc data add a more detailed structure to previously published fallout curves.