With the recently issued authority licence, the transition to the fuel replacement interval of once per every 15 months, instead of every 12 months, is now authorised to commence. Since fuel may only be replaced when the reactors are shut down, the introduction of a new type of fuel has also become necessary, which burns up and loses efficiency in a longer period compared to the former ones. The new fuel assembly - named Gd-2_4.7 - is a product of Hungarian innovation; it was developed through international cooperation, based on the design of the Reactor Physics Section of the Paks Nuclear Power Plant (lead by Dr. Imre Nemes). Among similar types of nuclear power plants, Paks is the first to introduce the 15-month operation interval.
The use of operation intervals exceeding 12 months is not unprecedented in the world. Due to the economic benefits of implementing extended fuel and outage intervals, the use of fuel intervals different from 12 months has become prevalent in numerous leading countries of the nuclear industry, including the United States and France, already in the 1990s. In the US, the mean duration of operation intervals has increased to 18 months after 2000, while in France the majority of nuclear power plant units operates with the fuel intervals of 15, 17 or 18 months. The Krško Nuclear Power Plant in the closest vicinity to Hungary, has already switched to 18-month operation in 2004.
The introduction of the 15-month interval has several economic benefits to both the nuclear power plant and the Hungarian economy, including the most important improvements of safety aspects. After the introduction of the 15-month operation interval, proportionately with the reduction of outage work volume, collective dose (the total occupational exposure of the power plant staff) will significantly decrease, and the number of failures due to maintenance risk will also be further reduced. Applied to the entire lifetime of the plant, the number of unit shutdowns and restarts (the so-called transient states) will be lower. (Transients mean increased stress to the nuclear power plant equipment, and therefore the reduction of their number has positive impact on nuclear safety and the lifetimes of systems and components.)
The further improvement of sustainability and environmental impact factors is also extremely important. Due to the 15-month operation and the application of the higher enrichment fuel, the volume of spent fuel is reduced by 3% on average, and the volume of low and medium level radioactive waste produced during maintenance works and also the level of non-radioactive waste is also significantly reduced.
From the viewpoints of the Hungarian public and the national economy, the expected increase of the production at the nuclear power plant due to the introduction of the 15-month operation interval is also significant. With the rescheduling of the outages, annual availability increases by 2% on average, thus also increasing the volume of the electric energy produced, covering the demand of approximately 80 000 households, i.e. almost a quarter million people. Proportionately to the increase of the produced electricity volume, the electric energy import dependence of Hungary can also be reduced by 1%, thus contributing to the security of supply. Proportionately to the decrease of maintenance work volume, the service and material costs related to maintenance can also decrease.
Considering the above, with longer campaigns environmental impact can be significantly reduced, the safety of the nuclear power plant can be maintained and improved, and its competitiveness will also increase.
The complex implementation of the 15-month intervals - similarly to every other technical change at a nuclear power plant - requires the licence issued by the relevant authority, and the authority has classified this transformation in its most stringent category.
After the issue of the licence, 15-month operation has begun, and simultaneously with the refuelling schedule, until late 2016 it will be implemented at all four power plant units.
The Paks Nuclear Power Plant has supplied safe, cheap and environmentally friendly electric energy to the residential and industrial consumers in Hungary for more than 30 years. In 2014 Paks NPP has covered 53.6% of the total energy output of Hungary. The corporate vision of Paks NPP, in addition to the primacy of nuclear safety at all times, is minimising environmental impact and maximising electricity production, in a technically sound manner, at the optimal level of costs. Since the commencement of its operation, the nuclear power plant has improved its systems with transformations contributing to safety, sustainability and economy, and it has operated at an internationally acclaimed level of safety.
In accordance with its corporate strategy, MVM Paks NPP Ltd. has increased the nominal electric capacity of the units to 108%, acquired the operational licence of units 1 and 2 for a lifetime extension of 20 years, and the authorisation of the lifetime extension of units 3 and 4 is also being carried out.
23 nuclear power plant units of identical type with the VVER-440/213 unit used at the Paks Nuclear Power Plant operate all over the world. When the Council for Mutual Economic Assistance (Comecon) disbanded, due to both financial and geopolitical reasons, and also because of focusing capacities on the new third and fourth generation unit types, the Russian designer and manufacturer abandoned the further improvement of the VVER-440 unit. This vacuum was made up for by the operating countries through establishing their international engineering scientific background. Hungary had a great advantage, as the university education of natural science is traditionally of very high quality, and the spirit of Leo Szilard, Eugene Wigner, John von Neumann and Edward Teller is still present as a heritage in the Hungarian nuclear industry. This engineering scientific background is the cornerstone of the nuclear safety of the Paks Nuclear Power Plant, and the innovations of the present and the future.
The operation of the power plant, its constant modernisation, the lifetime extension and the preparation to introducing the 15-month operation interval have been assisted by a wide and well-organised system of partnerships: almost 30 qualified domestic and foreign service provider and supplier companies, including the former suppliers, design and scientific institutes, the chief designer of the nuclear power plant, the fuel manufacturer and designer facilities and research institutes. This background enabled the Paks NPP to be the first place where the VVER-440 type unit has its operation intervals extended, and enabled Hungary to be the location for designing the required nuclear fuel.
During the licensing procedure conducted pursuant to Act on Atomic Energy and Decree No. 118/2011 (VII. 11.) of the Government, the Paks Nuclear Power Plant has presented in its almost 30 000 pages long documentation to the Hungarian Atomic Energy Authority the modified complex technical system, the operational and status control programs and criteria, and also the demonstrations of the admissibility of changes.
For the extended operation interval and the application of the modified fuel assembly it requires, the acquisition of the nuclear licence was necessary. Preliminary conditions of issuing the licence included the power plant receiving the environmental permit for the application of the modified fuel, the successful completion of the test operation and the certification of the compliance of the spent fuel storage facility regarding the higher mean enrichment fuel, which was implemented with the amendment of the environmental use and nuclear licence of the Interim Spent Fuel Storage Facility, also granted in the course of a strict official authorisation procedure.
During the administrative proceedings, the Hungarian Atomic Energy Authority has organised a public hearing on 23 June 2015. No social acceptance doubts have been raised with regard to the introduction of C15 and therefore the licences required for commencing the 15-month intervals could be granted.