Basınçlı su soğutmalı reaktörlerde yoğuşturucu su sıcaklığının değişmesinin reaktör gücüne etkisi

Abstract

ÖZET Bu çalışmada, basınçlı su soğutmalı reaktörlerde yoğuşturucu so ğutma suyu sıcaklığı artışının reaktör gücüne olan etkisi incelenmiş tir. Bu çalışma için Akkuyu Nükleer Güç Santralı Projesine ilişkin veriler örnek olarak alınmıştır. Birinci bölümde, Akkuyu da kurulması düşünülen Basınçlı Ağır Su Reaktörü hakkında genel bilgi verilmiş olup, santral ekipmanlarının işlevleri anlatılmıştır. Bu bölümde yüksek ve alçak basınç türbinleri, türbin by-pass sistemi, nem ayırıcı/kızdırıcı, buhar-jet hava ejektör- leri ve buhar kaçağı sistemleri incelenmiştir. İkinci bölümde, yoğuşturma ve ısı besi-suyu sistemleri hakkında genel bilgi verilmiş olup, tez konusunun esasım teşkil eden yoğuşturu cu! ar incelenmiştir. Yoğuşturucuda kullanılan yoğuşturucu tüpleri, yo ğuşturucu kabı, su akıntı kutuları, buhar-jet hava ejektörleri ve ani kalkış hava ejektörleri hakkında bilgi verilmiştir. Ayrıca ana soğut ma suyu sistemi (deniz suyu) ve deniz suyu korozyonuna karşı korunma sistemleri hakkında da bilgi verilmiştir. üçüncü bölümde, santralın bazı karakteristik noktalarında mevcut verilere göre akışkanın basınç, sıcaklık, entalpi vb. gibi termodina mik özellikleri ayrıntılı olarak hesabedi İmiştir. Santrala ait söz- konusu edilen bu noktalardaki termodinamik özellikler bir şema üzerin de gösterilmiştir. Bu sonuçlara göre entalpı-entropi (h-s) diyagramı çizilmiş olup, bölümün sonunda bulunan entalpi tablosu hazırlanarak tüm noktaların termodinamik özellikleri belirtilmiştir. Ayrıca türbin işleri, verimler ve özgül ısı oranları da hesaplanmıştır. Dördüncü bölümde yoğuşturucu hesabı ayrıntılı olarak incelenmiş tir, öncelikle yoğuşturucu boruları ve malzemesi seçimi yapılmış olup, buradan çıkan verilere göre yoğuşturucu tüp ölçüleri belirlenmiştir. Daha sonra toplam ısı transfer katsayısı hesaplanmıştır. Buradan yo la çıkılarak yoğuşturucu soğutma yüzeyi, yoğuşturucunun özgül buhar yükü tesbıt edilmiştir. Tüm bu hesaplamalardan sonra bölümün sonunda dizayn hesapları tablo halinde verilmiştir. Beşinci bölümde buhar üreteci hesabı yapılmıştır. Verilerden yo la çıkılarak reaktör kısmı ve buhar üreteci (1. devre) kısmında üreti len ısılar hesaplanmıştır. Altıncı bölümde yoğuşturucu soğutma suyu sıcaklığı artışının et kileri incelenmiştir. Santralın bulunduğu bölge Akdeniz Bölgesi olup, Akkuyu'da tesis edilmesi planlanmıştır. Akdeniz Bölgesinde deniz su yu sıcaklığı, yaz ortalamalarına göre 30 (°C) dolayında bulunduğu bi linmektedir. Bu bölümde, başlangıç deniz suyu sıcaklığı 17 (°C) ki bu değer yoğuşturucunun dizayn değeridir, bu değerden itibaren sıcaklığın artmasıyla reaktör gücüne olan etki incelenmiştir. Yedinci bölümde i- se altıncı bölümde bulunan değerler yardımı ile özgül ısı oram ve net elektrik çıkışına ait iki eğri çizilmiştir. Bu eğriler yardımı ile so ğutma suyu sıcaklığının artması ile reaktör gücünde meydana gelen deği şim hakkında yorun getirilmiştir.

SUMMARY In this study, the effect on reactor power when increase of the condenser cooling water temperature is analysed in Pressurized Heavy Water Reactor. For this purpose, the technical data belong to the Akkuyu Nuclear Power Plant is used in this work. In Chapter 1, some general knowledge about the Akkuyu Nuclear Power Plant are given. The operation procedures of some of the plant equipment, which are high and low pressure turbines, turbine by-pass system, moisture seperator steam- jet air ejectors and sealand leakage steam system are reviewed in detail. The turbine is a tandem compound machine consisting of a double flow high pressure turbine and three double flow low pressure turbines. The purpose of the turbine is to convert the thermal energy of the steam from the reactor to mechanical energy at the turbine/ generator coupling. Steam flows from the reactor through the turbine inlet stop and control valves to the high pressure turbine and then via moisture seperator units to the three low pressure turbines. Steam from the high pressure turbine flows via cross-over pipes to two moisture seperator units situated horizontally, one on each side of the turbine. The dried steam then enters the single VI istage reheating section which consists of two opposed U-tube bundles arranged in to the dryers. Two cross-over pipes carry steam from the moisture seperator/ reheater units to each low pressure turbine. The steam exhausts directly to a condenser under the turbine. The function of the seal and leakage steam system is to prevent the leakage of steam to the turbine room under all operating condi tions and prevent the ingress of air into the turbine under all ope rating conditions. Under normal operating conditions, steam leaking from the high pressure turbine glands and the control value glands is fed to a main whose pressure is controlled at a value slightly above atmospheric. To prevent steam leaking to atmosphere, the high pressure and low pressure turbine glands are connected to a second main whose pressure is held a a value slightly below atmospheric pressure. This mains thus extracts a mixture of air and steam from the glands. This mixture is then condensed in a gland-steam condenser. The extracted air is removed by fans and exhausted to atmosphere whi le.the conden sed steam is returned to the main turbine condenser. An additional supply of throttled inlet steam is supplied to the high pressure turbine glands. The pressure of this steam is higher than the high pressure turbine exhaust pressure and hence the ingress of moist steam, which could damage the seals, is prevented. The function of the by-pass system is to direct to the con denser the steam from the inlet steam lines during start-up conditions viitand under transient operating conditions where the steam flow from the reactor is in excess of the steam demand from the turbine. Steam from the inlet steam lines in led through a stop and a control valve to a steam dumping device situated on the wall of the condenser. The steam pressure is reduced in the control valve, and in the dump ing device pressure is further reduced to condenser pressure. In Chapter 2, some general information on condensing and feed- water systems main studying subject for this thesis, are given know ledge about the condenser tubes, the condenser hotwell, the flash boxes, the quick-start air ejectors are also given. Additionally, some in formation on main cooling water system (sea water) and protection against sea water corrosion are given. The function of the condenser is to condense the turbine ex haust steam, condense reactor steam possing from the by-pass directly to the condenser, collect and cool drainage from different parts of the plant during start-up and normal operations, collect and cool drainage from the different parts of the plant during emergency conditions. The condensing system consists of the condenser, condenser hot well, flash boxes, operational steam jet air ejectors and quick starting ejectors. The condenser is of the single pass type and is directly connected to the Raw Pressure turbine outlet. The condenser has four single-pass tube bundles through which sea water is circu lated. Steam condensing on these tube bundles falls to an inter mediate floor above the condenser hotwell. This intermediate floor is divided into sections and in each section a conductivity cauneis ixplaced, thus enabling the position of any leaking tubes to be rapidly determined. more On the lower side of the condenser is the hotwell which acts partially as a condensate reservoir for various turbine and reactor systems and partially as a regulation vessel for the control of the condensate pumps and the make-up water supply. Several flash boxes are provided in which the saturated water from emergency service and start-up and other drains is expanded down to condenser pressure. Each flash box is connected to the con denser by two connections, one carrying the condensate and the other carrying the flash steam. During normal operation, vacuum is maintained in the condenser by steam jet air ejectors units which use throttled inlet steam as the driving medium. The gases extracted from the condenser are led to atmosphere while the condenser condensed in the steam jet air ejector condensers is led to the main condenser. Sea water is used for cooling the main condenser, the turbine island closed cooling water circuit and the reactor closed cooling water circuits. Sea water is drawn through a tunnel, the intake of which is approximately 850 m from the shore. The tunnel consists of a 4x4 m concrete culvert, water from the screens flows to the suction of the circulating water-pumps. Three pumps each of 50% capacity are pro vided. The possibility exists of operating with one, two or threepumps in service, and thus it is possible to reduce the station aux iliary load under low turbine-output conditions or when an excepti onally low sea water temperature exists. The pumps are specially de signed for sea water duty and are of the vertical axial-flow type. Water from the pumps discharges into a 4x4 m interconnected concrete culvert All items in the sea water cooling circuit are manufactured from non-corrosive materials. The cooling water pumps are coated on their inside and outside surfaces with a thick epoxy-tar surface. Steel piping and the water boxes of the condenser are rubber lined. To prevent corrosion of the condenser and closed cooling water circuit cooler tubes, soft iron plates are fitted to the condenser inlet water boxes and a protective layer of iron is deposited on the copper alloy condenser tubes, a system is provided for the injection of copper sulphate into the cooling water inlet to further improve the built up of a protective layer on the condenser tubes. In Chapter 3; some of the thermodynamics properties like pres sure, temperature and spesific enthalpy are calculated in detaily. by using the data for some characteristic point of this power plant. In the end of this chapter, the enthalpy vs. entropy (enthalpy- entropy) diagram has been plotted and the enthalpy chart has been prepared by using the results of the calculations. In addition to these, efficiencies and spesific heat ratios have been determined. xiIn Chapter 4; condenser calculations are realized perfectly. First, condenser tubes and materials are choosen and appropriate di mensions of condenser tubes are determined. Then, the overall heat transfer coefficient is calculated. Condenser cooling area and con denser spesific heat load are determined by using the obtained results, After all of these calculations, the results of these design calculations are given in tables in the end of these section. In Chapter 5; steam generator calculations have been done. Heat generated in reactor and also heat transferred to the secondary side of steam generator by the primary heat transport system are calculated. In Chapter 6; the effect of the increase in temperature of con denser cooling water on the power plant is studied. Plant was plan ned to be built in Akkuyu in Mediterranien Region of Turkey. Sea water mean temperature for Summer season in this region is approxi mately 30° C. In the beginning, 17°C is chosen as the design temperature for condenser. Then, the effect on reactor power of the increase over this temperature is studied gradually. In Chapter 7, as a result, spesific heat ratio and net electric output diagrams are plotted by means of the d.ata obtained in Chapter 6, and then, these diagrams are used to make comment on the effect of increase of the condenser cooling water temperature. xii