Feasibility of the laser particle spectrometry technology for in-situ testing of hepa-filtration systems in the nuclear industry

The application of the laser spectrometer as detector for rig testing of HEPA filters was investigated and compared to the uranine and DOP methodology. These rig tests were performed at different volumetric flow rates (350-3000 m3/hr) and for single and double HEPA filters. The sensitivity of the laser detector on this test rig was at least 103 higher as the two conventional methods. Penetrations down to 10-8 (confidence level of 99.7%), over the whole light scattering range (0.09-3 μm), were measured. Leakpaths of more than 1 mm2 could be observed, working at three different flow rates through influence on the relation by p=a vsup(-b). The influence on the ''a'' parameter was important. The influence of the particle size distribution of the test aerosol was established, giving rise to different penetration values depending on the considered size control. A particle size distribution can be established over the range 0.09-3 μm. For the DOP aerosol the ratio of penetrations for the size range (0.09-0.195 μm) and (0.09-3 μm) was about 2. For the French uranine method this ratio was 1 indicating that this aerosol gives only information about the maximum penetration size range. Nevertheless a comparison in the range 0.09-0.176 μm gave a same figure for both aerosols. The laser detector has the great advantage that particles with different physical characteristics can be measured. The application of the laser detector is well promising. Rig tests under more severe conditions indicated that the DOP and uranine aerosols are still good test aerosols for temperature up to 80 deg. C and higher humidity. The feasibility to transform the in-situ test into a more economical kink of total filtration system efficiency test was assessed. This in-situ test, using laser detector, replaces the manufacturers' rig test and the in-situ leak test through one test. With the present single particle spectrometer it was possible to assess penetrations less than 10-6 for the 0.09-3 μm light scattering size range