Document wgope7vbgrzqVdxbyGjped2MJ

TECHNICAL BRIEFS 12 Olgesb lor yog on; NUCLEAR POWER WATER TREATMENT latest engineering developments lor busy power men STEAM GENERATION FUELS AND FIRING Primary coolant fM"p Boiler feedwater pump ELEMENTARY BLOCK diagram of possible nuclear power plont, Reoctor Is merely source of heat energy. Heat Is extracted by coolant, transferred`-via Seat exchonger to turbine system HEART OF CONTROL for nuclear plant it fts primary operating cycle. Desirable goal Is reoctor whose overoP octMty decreases as reoctor avcrago temperature Ihoi Nuclear Power Nueteor Fewer Plant Control Consider' atlons. By M A Sehulti, ITcstinghoust Electric Carp. The development procedure for de- signing the control system (or a nuclear power plant (s basically the same pro* cedure as for any other type of power plaot but the presence of a nuclear re* actor as a component in the system imposes many unusual design prob* Jems. This article reviews general plant considerations affecting control system design giving special emphasis to the features of reactor control. Thebajic method of approach to eon* irol system design consists first of study* ing the plant operational requirements and the plant control requirements. Fol* lowing this review a preliminary block diagram of a control system to fulfill these requirements may be attempted. However, after a study of this diagram, it often becomes apparent that the In herent dynamics of the plant and the characteristics and limitations of some of its components are of utmost im* portenco. Modifications ore then made to-the proposed block diagram. Once the desired operstiun of the control eys* tern is fully understood, the problem of synthesizing the control system can begin. ' For the sake of illustration an ele mentary Mock diagram of a possible nuclear power plant is shown left, above. Here-tbe reoctor is considered .merely as a source of hent energy. When this heat is extracted by passing a coolant through the reactor, the heat energy is then transferred vie e heat exchanger to a turbine system, and the output shaft of the turbine can be made to drive many types of working apparatus. The primary coolant considerations ere basic for control design, and it may be mentioned in passing that gas, water, --and liquid metals have been proposed as reactor coolants. Start-up and shut-down requirements affect the control system/ Here the nu clear reactor plays a prominent pert in determining plant performance for na* clear reactors cannot be started up too fast and never oan be really shut down. In considering the output of the nu clear reactor there is no such thing as "aero power" involved, right, above. Even In a brand new cold clean reac tor which has been shut down as mooh as possible an inherent souree of neu trons exists which causes a certain amount of nuctear fission to occur. This fission produces minute amounts of power and in the process more neutrons are released. This effect requires that the reactor neutron output be monitored continually to see that the neutron level is kept under control. In practical cases this monitoring means that instrumenta tion for measuring neutrons matt be cap able of operating over ranges as wide os 6 to 10 decodes and control provisions must be provided over a similar range. Starting up a reactor from a cold eon-' dition means that the reactor can ope! over a netaron range of many before any appreciable useful power`s gins to occur at the' output.'So arbitrary number of neutron fiur has to be taken os xero power.^;l example 1% of full load output be considered to be the equivsli zero power. Transitions between.. full power end 100% full powerlj be made relatively rapidly, btr^ cause of the safety aspects invtjlv transitions from a cold slarl-up mug, made quite slowly. AIEE Pope* 53*3/. Water Treatment Conversion of a Two Stage Hot i Water Softener. By G H Gowdy, > Service Corp and S B Applebaum, Co rone Corp. In 1949 a 16,000 gph two*sta|e;l lime-soda hot-phosphate softener >*, stalled in the Kendall Square stalky the Combrldge Electric Light (a treat up to 30% make-up for two V, pslg boilers evaporating 200,000 Ibj hr each. In 1951 make-up demand*; ceeded 20,000 gph at times. A ,Jr tank wae considered to tupplT th* Pf! demands. But conversion to hot tj{ teollte proved more economical. The second-stage phosphate tank now operates in parallel first stage tank providing settling capacity. Three more ... REAPER StRVtce SECTION