An Analysis of Salt and Moisture Deposition on the Air Sampling Probes in the Exhaust Shaft of the Waste Isolation Pilot Plant

Abstract

A study was performed to determine the source of moist salt formations on air sampling , probes at the top of the exhaust shaft used in ventilating the waste repository at the Waste Isolation Pilot Plant (WIPP). An earlier study by Texas A&M Univ suggested that outdoor weather conditions affected the rate of growth on the air sampling probes. Specifically, moist salt tended to form more heavily during relativel dry outdoor conditions, whereas the amount of salt on the probes diminished during moist outdoor conditions. The conditions of the air were already being monitored outside, at the bottom of the exhaust shaft, and at the top of the exhaust shaft. The data obtained from the weather instrumentation at the top of the exhaust shaft were believed to be affected by outdoor conditions and were not believed to accurately report the conditions of the air. Additional weather monitoring equipment was installed at the top of the exhaust shaft in a location that would not be subjected t outside influences. The data obtained from this instrumentation, along with the data obtained from the weather monitors outside and at the bottom of the exhaust shaft, w used to develop a computer model of the waste repository and of the exhaust shaft, Using the computer model, the conditions under which moisture would precipitate out of the air stream as a result of the cooling the air.underwent as in passed through the exhaust shaft were predicted. The model showed that such conditions rarely existed, and that an unaccounted for source of moisture was entering the exhaust shaft air stream. It was believed that this additional source of water was coming from either ground water recharge or from aquifers the exhaust shaft penetrated, and that sealing the exhaust shaft to prevent this influx of moisture would reduce, if not eliminate, the problem of moist salt forming on the air sampling probes.