Studies on in-place test of high efficiency particulate air filters in nuclear fuel facilities

Probelms in in-place test of high efficiency particulate air (HEPA) filters by a forward light-scattering photometer were studied in comparison with those by a laser particle spectrometer. Following are the results: (1) In the forward light-scattering photometer there is good linearity between the indication and the mass concentration of DOP aerosol up to 100 mg/m3. (2) The penetrations measured by the forward light- scattering photometer are nearly equal to the total reduced mass penetrations measured by the laser particle spectrometer. (3) In measurement of the penetrations of HEPA filters by the laser particle spectrometer a maximum penetration (count bases) appeared at particle size 0.1 μm - 0.2 μm, which was apporoximately equal to the penetration (mass bases) by the forward light-scattering photometer multiplied by a factor of 10 - 40. The penetrations, however, did not exceed the design value of 0.03 %. (4) In the measurement by a laser spectrometer, by-pass leakage of a HEPA filter can be known in the deviation from a penetration-particle size curve beyond a certain particle size. (5) Light-scattering photometers are suitable to test a single stage HEPA filter system due to good operation and the linearity, but not for a two-stage one. (author)