Facility Start-up with Air in Loop:

Below figure describes modifications to chemistry within an experimental facility which was started up along with high oxygen and nitrogen within the system from the deliberate addition of air.  Since the power level and temperature were raised then nitric acid created and neutralized the ammonium hydroxide present from earlier operation. The Conductivity and pH decreased until pH 7 was reached; while the water became acidic the conductivity displayed a corresponding increase.  Along With the creation of nitric acid (from the nitrogen present), a corresponding increase within chromate ion was observed (in that case Cr concentrations are directly associated to crud inventories and result from chemical attack on facility materials).  The procedure was reversed through adding hydrogen that combined along with the oxygen and decreases the chromate and nitrate ions.

It should be remembered, therefore, that in the above experiment the chromate ions were efficiently erased from the coolant through decreasing their solubility.  This would not be the case for the majority of the crud. A vast majority of crud would remain suspended within the coolant until it was either removed mechanically (filtered) or settled and redeposited at another locations inside the system (involving redeposition on the core surfaces).

Figure: Facility Start-up with Air in Loop