DE1062837B - Process for operating a heavy water boiler reactor - Google Patents

Description

In most nuclear reactor systems, the heat is transferred by a circulating liquid, e.g. B. Water, discharged to the outside for recycling. While high pressure water is a good heat transfer medium, but also requires very high operating temperatures at the required high operating temperatures Pressures which are generally three to five times the pressure under which the working medium stands for the power plant itself - such as the steam at the turbine inlet. That means but very thick-walled coolant vessels in the reactor and similar pipelines.

As is known, these disadvantages are avoided by the simple boiler reactor in which the evaporating cooling water is used is also the work equipment of the power plant. It limits · - ■ in contrast to the autocatalytic Reactors - also its own maximum output, since a sudden increase in reactivity in the Coolant forms steam and thus the content of the water, which also serves as a moderator, in the reactor core decreased. As a result of the rapid change in density of the water, on the other hand, the also fluctuates Output of the reactor when the maximum steam generation (based on the total water content of the Reactor core) is not limited. Therefore, in the interest of smooth operation, the automatic Power control by means of steam generation can only be used within a few percent (of the reactivity). The practical limit of steam generation is around 20%; a sufficient power density (Output per space requirement) can therefore only be achieved with small reactors. The sensitivity of this simple Boiler reactors against load fluctuations is also increased by the fact that with increasing steam extraction the operating pressure drops and the tendency to form steam increases. But it also falls the reactivity, due to the decreasing water content, continues to decrease when it increases should.

These disadvantages of the low stability with load changes and the power limitation can be avoided, as is known, by interposing an expansion system in the coolant circuit, whereby the high-pressure water heated in the reactor is expanded by means of a reducing valve in an expansion tank and is thus partially transformed into working steam at low pressure, which for example, a low-pressure saturated steam turbine can be fed directly. The remaining water - which is subcooled compared to the reactor pressure - is fed back to the high pressure system via a pump (for example together with the turbine condensate) and increases the reactivity there as a result of the subcooling, thus raising the process for operation
of a heavy water boiler reactor

Applicant:

L. & C. Steinmüller GmbH,
Gummersbach (RhId.)

the performance losses of the previously described reactor system, which works with the same pressure everywhere without the possibility of steam formation in the primary circuit in the event of an overload Impairing self-assurance. The low thermodynamic reduction in efficiency is far outweighed by the practical advantages.

Should a boiling reactor in the interest of a better neutron efficiency and a lower enrichment or a smaller amount of the required reactor fuel operated with heavy water it seems questionable, the heavy water vapor generated by the expansion of the engine to be supplied immediately. The self-stabilization given in the aforementioned system However, load changes can also be made with material separation of the circuits of the evaporating coolant (for example heavy water) and the working medium (for example light water) as follows reach:

An older German property right (German patent 1 003 363) provides the solution or application of this measure in that 'facilities for the extraction of energy from the non-boiling part of the Coolant and devices for supplying subcooled coolant to the reactor are provided are so that only part of the coolant in the reactor contains coolant in vapor phase, such that that the output power of the system is increased and the system is essentially self-regulating. "

The subcooling of the total coolant to be returned to the reactor should therefore be - similar as with the above-described single-circuit boiler reactor with expansion system - with increasing load are reinforced by the fact that the liquid phase of the coolant increasingly extracted relatively more heat

909 580/332

is called the vapor phase. The teaching actually given reveals, however, except for one-circle Systems (in which the reactor coolant and the working fluid of the power plant are not materially different from each other are separated) only a two-circuit system, in which the liquid coolant is a cross-flow heat exchanger Low-pressure working steam, whereas the vaporous reactor coolant is high-pressure working steam generated. In this way, however, the desired subcooling of the liquid reactor coolant is achieved only possible to a limited extent; because the coolant (i.e. the one that accumulates in the steam converter Heavy steam condensate or the liquid coolant removed from the reactor) can be used in one Cross-flow heat exchanger, which simultaneously generates low-pressure working steam, has not cooled down sufficiently will.

In contrast, with two-circle (i.e. with Pamp. Converter equipped) heavy water boiling reactors according to the invention, the heavy steam condensate obtained before being returned to the reactor in one of the preheating of the light water (or turbine condensate) to be evaporated in the steam converter, serving countercurrent heat exchangers with increasing total load of the power plant be hypothermic.

. However, this results in greater undercooling, especially when using additional coolants of the liquid reactor coolant possible than with the aforementioned system. As such, further auxiliary coolants For example, the combustion air (for example from a directly fired superheater or another incineration plant), liquid or gaseous fuel, any fuel gasifying agents, the heat transfer medium of heating systems or the like. Serve.

■ The subcooling of the liquid reactor coolant is therefore appropriate as a function of the load on the Power plant regulated in such a way that at least for part of the total load range the self-stabilizing effective adaptation of the reactivity to the changing load is guaranteed.

If the undercooling of the heavy steam condensate is the only thing to adjust the reactivity is not sufficient, of course, in a known manner, part of what has already been warmed up, but still liquid heavy water taken directly from the reactor and in a sub-cycle by means of a Countercurrent cooler - as well as the heavy steam condensate in the light water preheater mentioned - get hypothermic.

The regulation of subcooling, i.e. H. i.e. the actuation of the required switching valves for the Reactor coolant and the working medium used for its subcooling can be expedient automatically from the measuring device of an operating variable to be regarded as a load criterion of the power plant, for example from the working steam flow meter, made or controlled. ... The arrangement of the working medium evaporator, d. H. ■ des. Heavy water-light water steam converter, is arbitrary. In any case, however, the countercurrent preheater is used for the light water or for the working steam condensate the steam converter on the heavy water side downstream, while he (preferably the exhaust drum and over the same) the Steam converter is connected upstream on the light water side. In this case, an adjustable one is preferably used for regulation Light water bypass line or a bypass valve, whereby the steam flow in the Steam converter is not influenced in an undesirable way and the performance of the actual Reactor is adapted as desired to the load on the power plant.

The drawing shows the scheme of a possible embodiment in which the working medium circuit without superheater, engine, condensers and other additional equipment, i.e. the steam converter with the evaporation drum and the light water preheater together, for example, a forced circulation steam generator form. 1 is the heavy water boiler, 2 is the steam converter, 3 is the countercurrent heat exchanger that subcools the heavy water or light water preheater, 4 the return pump for the supercooled heavy steam condensate, 5 a controllable light water bypass valve for the heat exchanger 3, 6 a known one Circulation pump borrowed from forced circulation boilers for the light water to be preheated or evaporated, 7 the evaporation drum for the mentioned steam generator or boiler, 8 the light water feed line of the boiler, 9 the main outlet line (s) of the light water saturated steam generated, 10 the heavy steam outlet line from the reactor 1 and 11 the liquid level of the generated in the steam converter 2 Heavy steam condensate, from the level of which the drive of the return pump 4 is controlled.

The heavy water is evaporated in the reactor 1 and passes through the line 10 into the steam converter 2, where it condenses. The heavy steam condensate then gives off part of its heat in the countercurrent heat exchanger 3 to the light feed water, which in turn flows to the evaporation drum 7. The proportion of the feed water to be heated up and thus the subcooling of the heavy steam condensate are regulated by the bypass valve 5, depending on the load on the power plant, in such a way that at full load the entire amount of feed water flows through the heat exchanger 3 so that the heavy steam condensate is maximally subcooled and by means of the return pump 4 in is returned to the reactor. When the load is low, however, the heat exchanger 3 is short-circuited on the light water side and the heavy steam condensate is practically no longer undercooled. In this way, a self-stabilizing load control is made possible, at least above a certain pressure level and in a certain load range.

Claims (4)

Patent claims: 1. Operating method for a heavy water boiler, the heavy water vapor in particular for generating energy in a steam converter with the generation of light water vapor is condensed, characterized in that the heavy steam condensate before the return into the reactor in one of the preheating of the light water to be evaporated in the steam converter or turbine condensate serving countercurrent heat exchanger with increasing total load'increasing is hypothermic. 2. Operating method according to claim 1, characterized in that the heavy steam condensate is at least partially undercooled with the help of other work equipment, e.g. B. with the help of combustion air, liquid or gaseous fuels, gasification agents, heat carriers for heating systems or the like. 3. Operating method according to claim 1 or 2, characterized in that the rule characters ristics of the subcooling is chosen as a function of the load that at least in a part A self-stabilizing behavior in the event of load changes is achieved across the entire load range. 4. Operating method according to one of the preceding claims, characterized in that also a Part of the heavy water that has not yet evaporated is taken directly from the reactor and stored in the Countercurrent is subcooled. Older patents considered: German Patent No. 1 003 363. 1 sheet of drawings