Innovative extinction photometry for the characterisation of multicomponent-aerosol and humidity measurement (IN-EX). Sub-project A. Qualification of innovative extinction photometry. Final report

The overall goal of this joint project was to improve the metrological characterisation of a multicomponent-aerosol as well as the measurement of the humidity under boundary conditions, as they occur in an uncontrolled loss-of-coolant accident. For this purpose, different subprojects were used to develop two optical humidity sensors and one optical aerosol spectrometer. In the course of this named ''subproject A'' both the coordination of the overall joint project as well as the qualification of the sensors were conducted. To this end different testing facilities were at the project's disposal. First, suitable boundary conditions for the accident atmosphere in a target specification had to be determined. The atmosphere that was to be investigated contained a gas mixture of different amounts of helium, steam, nitrogen or air. Aside from the humidity sensor also an aerosol spectrometer was developed, which analyses the particle size distribution. For that reason, within the gaseous atmosphere also particle densities of different solid and liquid substances occur that are typical for this kind of accident. For the purpose of qualification the distinctive and nonradioactive substances caesium hydroxide, caesium iodide, silver and tin dioxide were chosen. After finishing the small test station, the Instruments were put into both as well individual examinations as fatigue tests. During the last measurement campaign in the small test station blind measurements were conducted in order to assess the quality of the developed algorithms and in order to examine the resilience of the sensors when put into operation. Overall, a heavy contamination of the optical parts within the FASP-measuring-head could be found. These parts were damaged irreversibly due to the chemically aggressive substances. This lead to a decrease with time of the detectable intensity to the same level as the detector noise. Therefore, the actual measuring head has to be revised for it to be used in such an atmosphere. Still, thanks to an affiliating algorithm, the detected spectres could be evaluated at least in parts. Thus the component tin dioxide was documented several times in these experiments. The other substances were not proven correctly. Also during the assessment of the optical humidity sensors a distinction must be drawn between the pure detection of the spectrum and the analysis with the help of the adjoining algorithm. Since the Steam-FASP is drawn passively, the intensity of the detectable signal decreases proportionally to the degree of contamination of the optical parts. At the same time, the Steam-FASP in its ultimate extension level overcame the demanded eight hours within the atmosphere alike to a breakdown. In contrary to this, the TDLAS is equipped with an active rinsing system for the optical parts, which lead to no decrease of intensity and a constant measuring signal. The particular recalculation prove that the Steam-FASP showed results that were less noisy than the results of the TDLAS, even though both algorithms are rest upon the same database. Since the spectrums that are to be detected with the TDLAS are very narrow-band and the data bases only have insufficient values for this area (high humidity, pressure and temperature) the findings result in a significant noise. Moreover, the optical humidity sensors have been - additionally to the the qualification tests within the small testing facility - put to use in an own series of tests in the REKO-4-plant (5,3m3 pressure tank) at the hydrogen laboratory at Juelich Research Centre (''Forschungszentrum Juelich''). Since the sensors are meant to be used in the field of reactor safety research in hydrogenous atmospheres, the optical humidity sensors had to be tested for a hydrogen-cross-sensitivity. No cross-sensitivities were found during the qualification tests.