PHWRs reactors

There are various types of nuclear power reactors, including boiling water reactors (BWR) and pressurized water reactors (PLWR or LWR), which are both light-water reactor (LWR) designs and are cooled and moderated by water. There also are pressurized heavy-water reactor (PHWR or HWR) designs. 

Pressurized filters, 11 324 Pressurized heavy water reactors (PHWRs), 24 758... 

Furthermore, HEEP will consider several reactor concepts including water reactors such as PWR and PHWR for the lower temperature range, the very high temperature reactors (VHTR), fast breeder reactors (FBR) and molten-salt cooled reactors for the high temperature range, and super-critical water reactor (SCWR) capable of output temperatures up to around 625°C for the medium range of temperature. 

Pressurized heavy-water reactor (PHWR) % 5 UO2 pellets (natural U) Zircaloy DnO D2O 280- 310 8 11 700 -800 8-10... 

Radioactive waste treatment applications have been reported [3-9] for the laundry wastes from nuclear power plants and mixed laboratory wastes. Another interesting application of reverse osmosis process is in decontamination of boric acid wastes from pressurized heavy water reactors (PHWRs), which allows for the recovery of boric acid, by using the fact that the latter is relatively undissociated and hence wdl pass with water through the membrane while most of the radioactivity is retained [10]. Reverse osmosis was evaluated for treating fuel storage pool water, and for low-level liquid effluents from reprocessing plants. 

As motioned in Chapter 19, the name implies that a pressurized water reactor is cooled by hot high pressure water, either H2O (PWR, VVER) or DjO (PHWR). In the PWR and VVER types the coolant is also us as moderator whereas a separate D2O containing moderator tank is normally used in the PHWR type. These power reactor types have several things in common primary — secondary coolant circuits separated by heat exchangers (steam generators), a pressurizer to adjust primary system pressure and often diemical shim control for adjustment of the excess reactivity with fresh fuel. 

The successful operation of 500 MWe thermal power plants in India has enabled to fix PFBR reactor power as 500 MWe. Large sized FBR have not indicated any technologic d problems because of reactor size. Specific capital cost is lower for 500 MWe than for a lower power, say 250 MWe. The design and development efforts needed for 500 MWe and 250 MWe plants are comparable. Pressurised Heavy Water Reactors (PHWR) of 500 MWe are under construction in India. Constructability of 500 MWe PFBR components has been assessed and adequate industrial capability exists within the country. 

One of the technical problems of ranoval of tritium is its low concentration in technological and waste streams. In heavy water reactor moderator (pressurized heavy water reactor [PHWR]), the ratio of DTO to D2O is 10 , and in water... 

Pressurized heavy water reactor "CANDU" (PHWR) Canada 33 18 Natural UO2 Heavy water Heavy water... 

Several reactor design have appeared in the SMR range that use Heavy Water as a moderator (e.g. CANDU 3, CANDU 6, PHWR 500, PHWR 220). The main features of this technology line is ... 

India has adopted a prime policy target of self reliance in nuclear power development, based on heavy water moderated reactors. Five units of the 220 MWe PHWR type are under construction and all are expected to be in operation by the year 1997. An additional four units of the same type and an extra four units of a scaled up 500 MWe type are planned. 

Reactor Type PHWR Number of modules/per plant 1... 

PRESSURIZED HEAVY WATER REACTOR PHWR-500 SYSTEM DESCRIPTION AND DEVELOPMENT STATUS... 

The Indian PHWR is a pressure tube type reactor using heavy water moderator, heavy water coolant (in a separate high pressure high temperature system) and natural uranium oxide fuel. 

On-power fuelling is a feature of all PHWRs which have veiy low excess reactivity. In this type of reactor, refuelling to compensate for fuel depletion and for overall flux shaping to give optimum power distribution, is carried out with the help of two fuelling machines, which work in unison on the opposite ends of a channel. One of the machines is used to fuel the channel while the other one accepts the spent bundles. In addition, the fuelling machines facilitate on-power removal of failed fuel bundles. 

The shutdown function in PHWRs is achieved by the reactor protection system which is capable of completely terminating any of the postulated reactivity transients in the most reactive state of the core. The characteristic design parameters specified for the system are ... 

The reactor protection system protects the reactor and associated equipment by tripping the reactor, when certain plant parameters exceed their respective set points. Two independent reactor shutdown systems are provided in PHWRS. These systems introduce a neutron absorbing material into the reactor core to decrease reactivity and therefore shutdown the reactor. The two shutdown systems are physically separate and diverse in function. The features of the shutdown systems are brought out in Section 5.9.2.3.3. 

---