Heating your home with nuclear energy
During the construction of the Bohunice V2 nuclear power plant (EBO V2), the works at Jaslovské Bohunice also included the construction of heat feeder for the city Trnava, commissioned on 10 December 1987. Ten years later a heat feeder was put into operation for the areas of the municipalities Leopoldov, J. Bohunice and eventually also Hlohovec. All these were part of the Bohunice V2 nuclear power plant project.The heat generated at the power plant has been warming people in the vicinity of the Bohunice nuclear facility for three decades, at their homes and work, using 44-km long heat transmission pipe routes.
The heat from the hot water is used for creating hot utility water and for heating residential and non-residential premises, institutions, public buildings, medical and educational facilities. This is not waste heat (as for instance the water from cooling towers has a maximum temperature of 36°C), but, rather, direct heat offtake from a steam turbine.
Let’s take a closer look at the heat production process of in steam and of heat in hot water:
- Primary water obtains heat in the reactor. The water temperature is 297°C, and in order that this water remains in a liquid state, the pressure in the primary circuit is kept at 12.26 megapascals. The secondary circuit contains steam as well as water. The steam is at a temperature of 256°C and pressure of 4.6 MPa.
- This steam spins turbines and part of it travels through the pipes to the heat exchanger station. At this point another water circuit is heated up, which travels in green pipes to the mentioned destinations, the municipality of J. Bohunice and the company JAVYS. This third water circuit is adapted to the external temperature. In the case of severe winters, the temperature ranges between 130 - 140 °C.
In summers, when the heating is off, the water in the hot water pipe is 70°C, and serves only for the preparation of hot utility water. By the time this water arrives to the end of its route, in the winter as well as summer season, it loses roughly 2°C of its temperature. The pipe length to Trnava is 28.5 km and to Hlohovec 23.6 km.
At the heat exchange stations at these destinations the hot water is used to heat up now a fourth water circuit, when counting the circuits from the origin of the heat in the reactor.So, there are two key pieces of information to remember: the heat is not waste and the water circulating in radiators in the homes around the EBO V2 is not active.
Thousands of apartments
The hot water provides the heating for 17 781 apartments in Trnava, 4 193 in Hlohovec, 205 in Leopoldov and 187 in J. Bohunice, where the heat is also used in 364 houses. If each apartment and house houses four persons, then the heat from the power plant provides warmth for 90 920 people. This year there is a plan for roughly 200 heat connections in J. Bohunice, including a college, two primary schools and the community centre in Hlohovec.
Every year the heat feeder is scheduled for a shutdown taking approximately one week; the shutdown takes place in summer. Last year was an exception when both units of the V2 nuclear power plant were jointly shutdown. During the 38 days of the shutdown, Trnava ensured hot water provision by means of the boiler company Trnavská teplárenská. The customers from Hlohovec, Leopoldov and J. Bohunice were provided with hot water from the start-up and back-up boiler of the company JAVYS.
In January 2017, the average temperature was -4.81°C. The average water temperature leaving the heat exchange station from the power plant premises at the time was 120.5°C. After transferring the energy in the towns, the water returned at a warm temperature of 66.9°C. To make a comparison: outgoing water in the summer months, when the heating is turned off, the temperature averages 70°C and returns at 54.5°C.
In Slovakia there are in total 330 heat providers. In the framework of Slovenské elektrárne heat is also provided by the Nováky power plant, to 11 943 apartments in Prievidza and Nováky and 46 houses in Zemianske Kostoľany. In addition to the hot water used for heating and the heating of utility water, ENO supplies the heat in the form of steam for technological purposes in the volume of 35% of its supply.
All premises of SE plants generate heat by way of a combined heat and power generation, with the exception of Mochovce Units 3 and 4, where the heat is generated in seven gas boiler rooms, and this heat serves for the purposes of completing Mochovce NPP units 3 and 4.