Research On Disinfection Factors Of Monochloramine In Circulating Cooling Water System Of Nuclear Power Plant

Energy is the prop of development of human society. Nuclear power, as a newenergy has advantages as: it cost little but generate lot, and it leads very littlepollution to the environment. The cooling circulation system ensures the stableoperating, while in the system there is a large number of microbes, these microbescan corrode the system and deteriorate the water quality, in that way the system cannot operate normally, so the disinfection is imperative. The research works with themodule of cooling tower of nuclear power plant of Dampierre, we study on thestability, kinetic reaction, biofilm on packing and influence of metal elements ofmonochloramine.First of all, we study on the stability of monochloramine. We use the method ofDPD to measure the residuel concentration of monochloramine with blank waterand raw water. From the results we know: the stability of monochloramine isinfluenced by N/Cl₂, temperature, pH and evaporation. When N/Cl₂ is high,temperature is low, pH is high, monochloramine is very stable. However weconsider the factor of economy, the final condition is: N/Cl₂=1.05, the averagetemperature is 35 oC in the system and pH of raw water is environ 8.5. Moreover,we study on the kinetic of consumption of monochloramine as a desinfect in orderto determine consumption of monochloramine with raw water is first-order kineticreaction, and the rate constant is 0.002 min^-1.Raw water from river of Loire is used in cooling system of Dampierre nuclearplant, it has nice quality as cooling water; the biofilm on the packings grow normallyas theoric curve of growth of microbe,and can be stable in seven days; we identify thespecies of the microbes, and we find Pseudomonas, Staphylococcus and Bacillus inthe biofilm. the consumption of monochloramine has two parts: solid phase(surfaceof packing) and liquid phase(raw water). When we donot put in the packings, wehave only liquid phase consumption, which cost 18.8% of monochloramine; andwith the packings, both the solid phase and liquid phase consume 60.3% ofmonochloramine, solid phase is more than two times than liquid phase; as thecirculant time is 6⁸ hours to add monochloramine, it is more efficient to addbefore the cooling tower than in the cooling pool.From the researches on metal elements we can find that: in solid phase, ironcan decompose some monochloramine, and the consumption of monochloramine isproportional to the proportion of iron on surface of packing, the relationship is:y=0.359x + 57.7; in liquid phase, iron cannot influence monochloramine, but cupric ion can consume monochloramine with relationship: y=0.013x + 21.21; zinc ion andmanganese ion cannot consume monochloramine.The research provide s some support to new energy trend of human society andto environment. The research results can also make China's nuclear power systemdesign and operation of water management to provide technical support andguidance.