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4.2 DESIGN BASIS EVENT (DBE) SIMULATION PHASES

The design basis event portion of the qualification test program consisted of three sequential exposure phases. These were designed to simulate the most severe expected levels of all potentially degrading conditions associated with postulated accident environments for nuclear power generating stations. The three simulations were seismic SSE, DBE radiation exposure, and environmental DBE exposure.

4.2.1 SEISMIC SSE

Immediately following the seismic OBE aging testing, seismic SSE simulation testing was performed by single frequency, single axis, continuous sinusoidal tests at 1/3 octave intervals as indicated in Figure 4.1 and the resonance frequency values that were not encompassed by the 1/3 octave intervals.

The input motion was applied to each orthogonal axis, separately, with the peak acceleration applied for a minimum period of 15 seconds at either the levels shown in Figure 4.1 or the point where a 10% change in the cylinder inlet port pressure occurred. Each valve was operated through two complete de-energize to energize to de- energize cycles at each test frequency, while powered at either 102/60 Vac or 90 Vdc. These tests were performed once with the valve pressurized to its maximum operating pressure differential and then repeated with each valve pressurized to either 10 psig or its minimum operating pressure, whichever was greatest.

A full baseline performance test was performed at the conclusion of this series of tests.

4.2.2 DBE RADIATION EXPOSURE

At the conclusion of the seismic SSE simulation the test valves were all subjected to baseline tests and again sent to Isomedix, Inc. for the accident radiation (DBE) portion of the program. The simulation consisted of exposure to a cobalt-60 source of gamma radiation with an average energy of 2.5 Mev. and a total dose of 180 megarads. Pipe plugs were again installed in the pressure, cylinder, and exhaust ports of the valves. The valves were maintained de-energized during this exposure period.

At the completion of this simulation the valves were returned to the ASCO facility and subjected to a baseline test.

4.2.3 ENVIRONMENTAL DBE EXPOSURE

Upon completion of the post radiation DBE simulation baseline testing, the test samples with B and C suffixes were forwarded to Wyle Laboratories of Norco, California. The test samples were subjected to the Environmental DBE simulation. The test samples were installed into a test chamber and subjected to a 30 day exposure to steam, chemical spray, and clear water spray simulating a combined Loss Of Coolant accident / High Energy Line Break event and post-event cool down. Figure 4.1 shows the actual temperature / and figure 4.2 shows the pressure profiles for this simulation.

Upon completion of the DBE environmental simulation the valves were subjected to a portion of the baseline test conducted at Wyle Labs. The valves were then returned to ASCO where the balance of the base line testing was performed at ASCO.

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