UPGRADING ELASTOMERIC SEALS FOR NUCLEAR SERVICE

Pumps, valves and instruments in nuclear plants have historically cont ained whatever elastomer each equipment supplier traditionally used fo r corresponding non-nuclear service. The proliferation of elastomeric compounds, and their sometimes uncertain reliability, is now being red uced by upgrading and standardizing on a handful of compounds that hav e each been verified to be high performers for their class of service conditions. The objective is to make cost-effective improvements In th e reliability and integrity of equipment in Canadian-designed nuclear plants. The effort focuses on elastomeric seals and includes understan ding sealing fundamentals, developing relevant data for superior compo unds for each service, and improving quality assurance methods, includ ing handling and inspection guidelines. In practice, discussions with plant personnel and review of plant records are the first step. Two se vere-service examples are given where these needs have been met by the following progression of activities: inspecting and laboratory testin g of seals removed from service, preliminary and qualification testing of improvements, introduction into service, and monitoring the upgrad ed seals during phase-in periods. Large gains in reliability and integ rity have been demonstrated for simulated normal and accident service conditions of heat, radiation and other deteriorative influences. Sign ificant savings in maintenance costs are also projected.