The effect on hydrazine on the transport and property of corrosion products in PWR secondary circuit

(1) Influence of sampling method of corrosion products: We confirmed that concentration and particle size of corrosion products were influenced easily by the shape of sample tap and the length of sampling pipe at some important locations such as final feedwater and moisture separator drain. As a result of this, sampling equipment with nozzle probe and short sample pipe was installed for all units. (2) Influence of feedwater hydrazine on behavior of corrosion products: Reducing atmosphere in the system will maintain well even if feedwater hydrazine is decreased to 100ppb. Furthermore, it turned out that decreasing feedwater hydrazine and increasing feedwater ammonia to maintain pH were advantageous for the decrease in iron, nickel and anionic impurities. Now, we put into practice of controlling FW hydrazine with 100-150ppb for all units. (J.P.N.)