At approximately 11am today the T2 cooling package heat exchanger secondary side water flow suddenly dropped from ~11gpm to 0.  This was confirmed to be a real reading by observing that with no secondary cooling both the inlet and outlet target water temperatures rose steadily with beam on the target.  While standing on the blocks in the T2 area and having a controls expert (wither "superuser" access mode) actuate the secondary side solenoid independently it was confirmed that no "click" was heard when power was supplied to the valve.  No other changes were observed with other parts of the CuALCW system, therefore it was concluded that the secondary side solenoid valve (B1A:T2CS:SVSEC) had failed.

Blocks were removed above the T2 cooling package, the CuALCW lines were valved off and drained, and the failed valve was removed.  A new valve was installed.  A section of 3/4" SS tubing was replaced with flexible 21" long 3/4" diameter SS hose to allow re-installation (alignment could not be achieved with rigid tubing).  Water supply and return were restored, and the system was started.  Because of the new section of tubing, the flow through the secondary side dropped from ~11gpm to ~9gpm.  This should not have a significant effect on operation.  No leaks were observed.

Total dose for Isaac: 0.15mSv, for Keith: 0.03mSv