Experience of the erosion-corrosion problems in the main ring cooling water system at the KEK-PS

After more than two decades have passed since the KEK-PS construction, water leak accidents in the cooling system have occurred frequently. Low conductivity deionized water, at 20 degrees centigrade, is supplied at the Mechanical support building and circulates in a closed loop. Water flows through the main ring magnets, various magnets for beam injection and extraction, correction magnets and the power supply system, and so on. Recently, various repair works due to the plugged water pipes have been attempted in a high radioactivated area. After several investigations it was concluded that most of the leaks come from erosion-corrosion after long periods of use. We introduce erosion-corrosion problems into future cooling system/material designs.