A LABORATORY APPARATUS FOR MEASURING THE AMOU OF TRITIUM ACTIVITY REMOVED FROM A CONTAMINATED SURFACE, BY DIRECT CONTACT WITH THE SURFACE

摘要

An apparatus is described that can be used to obtain data for evaluation of the health hazard to personnel who directly contact a sur¬face contaminated with tritium. The sampling component is a small glass roller wrapped with a strip of filter paper dampened with ethylene gly¬col. It is rolled over the contaminated surface to sample the activity. The sampling apparatus has adjustments to vary the surface contact time, the area of surface sampled, and the pressure applied. After a run, the contaminated roller is dropped immediately after contact with the sur¬face into a counting vial containing a scintillant solution, and the ac¬tivity is assayed. The apparatus is small enough to be operated in a conventional glove box.nThe precision of the measurements is influenced by the texture of the surface sampled. Precision measured on a smooth optical quartz sur¬face using a nonvolatile tracer, Pm143 as a contaminant was determined to be + 2%. The precision for tritium sampling from a relatively coar¬ser, nonuniform metal surface was approximately + 25%.nThe apparatus can be used to study the rate of tritium desorbed from the surface, which allows estimation of the cumulative hazard effect of multiple contacts with the surface during the desorption period. Representative samples of metal surfaces exposed to tritium show that after exposure, desorption is exponential, decreasing to an "equilibrium" amount within a few hours. Multiple contacts with these desorbing sur¬faces did not seem to significantly alter the desorption process.