VVER reactor

There are a number of ways to reduce corrosion. One is to increase the pH of the water to 8 by adding alkali, e.g. LiOH or NH3 ( 10 ppm). While reactors of US type use LiOH in order to reduce the formation of tritium firom n,y-capture in Li, the VVER reactors normally use KOH. When ammonia is used, the radiolysis yields HNO2 and HNO3 it is necessary to add H2 gas to shift the equilibrium from the acidic products. At an H2 concentration of 2 ppm, the concentration of dissolved O2 is greatly reduced. Instead of NH3, hydrazine or N2 may be added to the water to increase the pH via the reactions... 

The special parts of the system are units executing functions connected directly with the VVER reactor technology. 

The award for Neutronics of VVER Reactors, which permitted Professor V. V. Naumov (MEPhI) to visit the ANRCP universities and ORNL in November 1995, for the purpose of lecturing and consulting on this topic ... 

According to a number of experts, in particular from the former USSR, the attitude of the industry towards safety also changed in Eastern Europe after the TMI accident already in early 1980s, Russian designers of VVER reactors proposed a number of measures for safety improvements. 

The improved fuel with a reduced fuel element cladding thickness and an enlarged fuel pellet diameter currently developed for the VVER reactors will also extend core life of the VBER-150. 

VKR-MT is a direct successor of the VK-300 reactor developed for the renovation of reactor facilities previously used for weapon plutonium production [X-1]. The VKR-MT also makes use of the basic propositions of a concept of VVER reactor with micro fuel elements as developed by the Russian Research Centre Kurchatov Institute (RRC KI), the All-Russian Institute of Atomic Machinery (VNIIAM), and the Scientific and Production Association Luch (SPA Luch ) [X-2]. 

X-2] PONOMAREV-STEPNOI, N.N., et al.. Prospects of VVER reactors with micro fuel elements. Atomnaya Energia, Vol. 86 (6) (June 1999, in Russian). 

Improved fuel design with reduced thickness of fuel cladding and enlarged diameter of fuel pellet currently developed for VVER reactors will also enable the VBER core lifetime to be extended. This would make it possible to ensure VBER-150 operation without on-site refuelling during the whole period between FPU repairs. 

A standard once-through fuel cycle of the present-day VVER reactors is used, for which a well-established infrastructure and proliferation resistance measures are in place. 

Some fuel elements within the core contain gadolinium in the uranium dioxide fuel pellets and are used as burnable poisons. The geometric characteristics of such gadolinium fuel elements are similar to those of the core fuel elements. The gadolinium content in the fuel elements is identical with that in the VVER reactors. 

For the VVER market, FRAMATOME, COGEMA and Siemens joined forces in 1993 and founded European VVER Fuels GmbH, located in Offenbach/Main, Germany. The purpose of this company was to supply nuclear uranium fuel assemblies and related services for utilities operating VVER reactors. 

VVER Reactor Types, Designs, Listing and Materials... 

The long-term study of the phase compositions of corrosion products in VVER reactors is a prerequisite for safe NPP operation over its projected lifetime. Longterm observations of corrosion status via Mossbauer spectroscopy are very useful and relatively inexpensive. Based on the results obtained, the following lines of inquiry were established for the next period ... 

Ryzhov, S.B., Mokhov, V. A., Nikitenko, M.P., et al., 2010. Advanced designs of VVER reactor plant. In Proceedings of the 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8), Shanghai, China, October 10—14. 

Four nuclear power units are ciurently in operation in Finland the Loviisa NPP has two 488 MW(e) VVER imits and the Olkiluoto NPP has two 840 MW(e) BWR imits. These NPP imits have been in operation for 23-27 years. The construction of the fifth reactor, EPR 1600 MW(e) to be located at the Olkiluoto site, is scheduled to be started in early 2005. 

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 important features of the PWR core are shown in Figure 19.12 and described in 19.13.1. The design with a pressure vessel without facilities for fuel handling imder pressure necessitates a yearly shutdown for fuel rq>lacement. However, this is not considered a great inconv ence as a PWR anyhow has to be shutdown on a regular basis for safety inspection of pipes, welds, etc, and for routine maintenance. The need to shut down the reactor and open the pressure vessel in order to replace fuel also makes the PWR (as well as the VVER) resistent to concealed nuclear proliferation. 

It may be noted that the RBMK reactor design was chosen by the USSR (despite warnings from the Soviet Academy of Sciences) because it was better suited to available production facilities than the VVER types (which required the manufacture of large pressure vessels). The rapid introduction of RBMK reactors in the USSR made previously used energy resources (oil and gas) available for export to the West, giving a very needed hard currency income. 

VVER-440 SG, possibility of reactor module complete plant fabrication and its transportation by the railway, as well as closeness of the scale factor to NS s RIs that enables to use some developed technical solutions and reduce R D. For replacing the power capacities of the 2-nd unit four SVBR-75 modules are installed in SG compartments, and six modules are installed for each of 3-rd and 4-th units. 

If there is the increase of uranium enrichment in the make-up fuel, there would be the decrease of requirements for fuel elements operation conditions (see Table 2). But thus EUU decreases, being still several times as high as this one for the VVER-1000 reactor. 

WER-1000 ones in the open NFC under the same NPP s total power maintmned and NU resources. If the enrichment of make-up fuel is taken to be 4,4%, as it concerns the VVER-1000 reactor, then EUU for the SVBR-600 reactor would be three times of that for the WER-1000 reactor even in the fourth campaign. As a result, the consumption of natural uranium would decrease three times, i.e. die possible term of existing the open NFC would increase three times. 

TABLE 3. THE COMPARATIVE EFFICIENCY OF NATURAL URANIUM ENERGY POTENTIAL UTILIZATION. (THE INCREASE OF OPERATION TIME FORNP USING SVBR-600 REACTORS IN THE OPEN NFC IN COMPARISON WITH VVER-1000 UNDER THE SAME POWER AND NATURE URANIUM RESOURCES)... 

Since the inception of these cooperative efforts in 1992, U.S. specialists have initiated more than 150 joint projects and have completed over 50 of these projects. The program initially focused on reducing risks at reactors with a high risk of having an accident. Many projects immediately reduced risks at reactors by decreasing the possibilities of equipment malfunction or operator error. As the program has evolved, more attention has been placed on VVER-1000 reactors, particularly in Ukraine. 

Kouzmine, S.K., Ryazanov, B.G., Sviridov, V.I., (1995), Analysis of Criticality Safety in VVER-1000 Spent Fuel Sub-assembly Reprocessing at the RT-2-plant, Proceedings, III US-Russian Meeting on Non-reactor Nuclear Safety, Los Alamos. 

Since 1992, both France and Germany have developed bilateral cooperation programs with Russia in order to assess the feasibility of recycling weapons grade plutonium in Russian reactors. These cooperation studies came to a similar conclusion loading MOX fuel (made from weapons-grade plutonium) into Russian VVER-1000 and fast reactors, in particular the Balakovo units and the BN-600, is feasible. 

Both programs also developed concepts for pilot plants to fabricate fuel for these reactors. They were designed for capacities of approx. 1 to 1.3 t Pu/year, representing the consumption of four VVER-1000s and one BN-600 reactor. 

Russia intends to start the program for the use of weapons plutonium by introduction of MOX fuel into the existing four VVER-1000 reactors and one BN-600 reactor. The aim of the DEMOX project is to build an industrial demonstration plant in Russia that is able to produce the required MOX fuel. This plant could be in operation as soon as 2002. The fuel requirements are ... 

Within its various specialties, the TRACTEBEL Group is active in about one hundred countries. The presence of TRACTEBEL in the CIS is well known, more specifically in the Russian Federation in the engineering studies and backfitting for safety and reliability (EU-TACIS-BERD) for VVER-1000 and RMBK and a reactor simulator for the Beloyark reactor. In Ukraine, TRACTEBEL made feasibility studies for a nuclear power plant. The company developed a simulator for an RBMK reactor in Lithuania and is very active in the construction and operation of electrical power and heat generation plants in Kazakhstan. 

Besides, surfaces of FB and the fuel elements can be polluted by plutonium. The level of heat release for FB made of weapon plutonium is essentially higher than that for FB made from uranium (in the latter, heat release is practically absent). For example, heat release of FB of reactor BN-600 reaches 20 watts and that in FB of reactor VVER-1000 reaches 130 watts. The heat release of fuel bundles with regenerated or recycled reactor-grade plutonium is several times higher. 

VVER-1000 REACTOR FUEL ELEMENTS AND FUEL BUNDLES... 

At the moment, there are no transport packages in Russia that are suitable for the transportation of fuel elements and fuel bundles of reactor VVER-1000 with fresh mixed fuel. VNIPIET has performed design studies for such packages and appropriate auxiliaries. The work was conducted in two directions ... 

The safety of transport of MOX fuel requires careful analysis and substantiation. A use of available transport packages for MOX fuel transport will require essential upgrades and the development of new packages. This work would require considerable financial expense and a long time. Therefore, it should be started right now, so that there would not be a delay in deliveries of sample or regular fuel bundles to nuclear power plants. Besides, variants of the transport-technological methods of operation with fresh and spent MOX fuel in NPPs with reactor types VVER-1000 and BN-600 should be worked out. 

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