Energy amplifier

As Rubbiatron a concept of nuclear reactors is called. It goes back to ideas of Carlo Rubbia, Nobel laureate and former director of the research center CERN in Geneva. Long-lived radionuclides ( plutonium and other actinides ) from the operation of nuclear power plants to be converted in these plants specifically in shorter-lived radionuclides. Generally, these reactor concepts as transmutation reactors, English as Energy Amplifier (ie energy amplifier ) or Accelerator Driven Systems (ie, accelerator driven systems ) refers.

Basics

A particle accelerator for the protons is combined with a cracking reactor ( Accelerator Driven Transmutation Technology - ADTT ). Rubbias concept in the accelerator is a conventional synchrotron which accelerates protons to an energy of about 1 GeV. Take the protons in a subcritical reactor to a target of molten lead, released by the spallation neutrons. Meet The neutrons on a fuel mixture of thorium and the converted actinides ( from the waste from nuclear power plants ) and are absorbed by thorium nuclei. This is not easily fissionable thorium easily converts into a - that is, even with thermal neutrons - fissionable uranium isotope to. The nuclear reactions see it like this:

The reactor of Rubbiatrons is designed so that it is subcritical under all operating conditions. Thereby is not possible to get out of control, the chain reaction; it only runs as long as the proton beam strikes the spallation target.

The fission of the uranium isotope 233U releases energy that is dissipated as heat to the surroundings. This heat can be removed as in conventional reactors with a cooling circuit and converted by means of a steam turbine power generator into electrical energy. Ultimate goal of this concept is the construction of the reactor, providing more electrical power than is necessary for the generation of the proton beam.

Meaning of this concept is the possibility to introduce in addition to the elements thorium and lead radioactive waste from conventional nuclear reactors in the Rubbiatron. This waste generally consists of long-lived actinides, is converted by irradiation with short-lived nuclides in the spallation neutrons. This makes it possible, as few of these in the spent fuel or - also to introduce the radioactive waste contained long-lived radionuclides in a repository - a much lesser extent. There are also other technical proposals with the same objective. In summary, these methods are called transmutation. As a rule prior to the conversion, a separation of the components to be processed (referred to in English as Partitioning) takes place, is often also the term used in the art partitioning and transmutation or P & T.

Research facilities

In Belgium, is currently a research reactor based on the Rubbiatron concept, the so-called MYRRHA reactor designed. Construction is scheduled for 2015. As with Rubbiatron a sub-critical, passively cooled by lead reactor core is driven by a proton beam. Departing from the original concept of Rubbiatrons the reactor is, however, included as a nuclear fuel Thorium not, but mixed oxide fuel rods. The purpose of this facility will be to test the technology of transmutation in the proton beam driven reactor in pilot use in addition to other research fields.

In February 2012, was in this context for the first time a system that couples a particle beam with a lead- cooled reactor core, put into operation. Referred to with the " GUINEVERE " system to be experience for MYRRHA collected.

Another Rubbiatron -like plant is planned in the Japanese research facility J- PARC. The " Transmutation Experimental Facility " (experimental transmutation facility, TEF ) above is said to have a thermal output of 800 MW and are driven by an accelerator with 30 MW. Currently running preliminary tests to cool the sub-critical reactor core.

Feasibility and cost-effectiveness

The total cost is expected for a first plant for the transmutation of an investment volume of € and operating costs of € 20 million / year, 383 million. The proposed CERN facility of 1,500 MW thermal power transuranic and minor actinides can be mined at a rate of 402 kg / year. Since in this particular system is added to the thorium Kritikalitätsausgleich arise also 175 kg / year, uranium-233, so that the Aktinidenmenge is effectively reduced to only 227 kg / year. The 2010 operating in the Federal Republic of 17 nuclear power plants annually produced 370,000 kilograms of highly radioactive waste, the radiotoxicity and required storage period mainly the Minor of the contained 3700 kg of actinides and transuranic elements, especially plutonium, is determined. Only these are after separation (partitioning ) and again mixed with thorium in the proposed CERN facility einzufüttern and be reduced to the above rate. This results in a required number of 3.700/227 = 16 constantly running " Transmutern ". A feeding these plants with un-partitioned waste from uranium -fueled reactors, consisting of 95 % of uranium -238 is not provided and not even possible.

CERN Transmuter needed to compensate for the thorium criticality requires fine tuning to reduce the neutron flux generated by the accelerator. In systems such as MYRRHA or TEF instead burnable neutron poisons are used, which leave themselves little radioactivity, so that the effective throughput is significantly increased.

In a thorough study by the Nuclear Energy Agency of the OECD, a scenario with modern Transmutern for Germany and other countries will be completely calculated. Here, the fuel cycle up to that time ( 2009) for Germany is planned exit simulated to determine the exact composition of the waste. In a second step, the decomposition is 8 Transmuter (each 840 MW thermal power), working from 2030 with 40 -year maturity and 3 other Transmutern that process the output of the previous Transmuter from 2070 is calculated. This results in the following picture:

• Through the transmutation of long-lived nuclides into short-lived arises shortly hardly a reduction of radioactivity, that is one of the decay heat power - they may even increase slightly.
• The real success of transmutation is only achieved after hundreds of years. Compared to the situation without the 80 -year-old ADS transmutation is the decay heat after 100 years, only half as high and
• By 100-2,000 years, only a quarter as high.

Because of the challenges still to be technical problems and the high investment costs is questionable whether transmutation can actually be used in practice to any significant extent. Because next to a (mainly conventional ) reactor, a large accelerator is required, the cost-benefit ratio is favorable than for conventional nuclear power plants. The construction Rubbiatron -like systems is for economic reasons, currently (2013 ) at least as inefficient as the construction of new conventional nuclear power plants. Especially the " dramatic escalation of the costs of all large industrial projects where engineering services are in demand. " represents the economic realization in doubt.