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126-418: PSI develops, builds and operates large and complex research facilities and makes them available to the national and international scientific communities. In 2017, for example, more than 2,500 researchers from 60 different countries came to PSI to take advantage of the concentration of large-scale research facilities in the same location, which is unique worldwide. About 1,900 experiments are conducted each year at

252-404: A synchrotron light source (SLS), which is particularly brilliant and stable, a spallation neutron source (SINQ), a muon source (SμS) and an X-ray free-electron laser ( SwissFEL ). This makes PSI currently (2020) the only institute in the world to provide the four most important probes for researching the structure and dynamics of condensed matter (neutrons, muons and synchrotron radiation) on

378-544: A campus for the international user community. In addition, HIPA's target facilities also produce pions that feed the muon source and the Ultracold Neutron source UCN produces very slow, ultracold neutrons. All these particle types are used for research in particle physics. Research at PSI is conducted with the help of these facilities. Its focus areas include: All the materials humans work with are made up of atoms . The interaction of atoms and their arrangement determine

504-457: A deep geological repository. Since 1984, PSI has operated (initially as SIN) the centre for Proton Therapy for treating patients with eye melanomas and other tumours located deep inside the body. More than 9,000 patients have been treated there until now (status 2020). The institute is also active in space research. For example, in 1990 PSI engineers built the detector of the EUVITA telescope for

630-406: A dense solid which has few pores. The thermal conductivity of uranium dioxide is very low compared with that of zirconium metal, and it goes down as the temperature goes up. Corrosion of uranium dioxide in water is controlled by similar electrochemical processes to the galvanic corrosion of a metal surface. While exposed to the neutron flux during normal operation in the core environment,

756-471: A flat-top cavity, and has enabled a significant increase in the number of extracted particles. Since 2008 all the old aluminium cavities of the Ring Cyclotron have been replaced with new copper cavities. These allow higher voltage amplitudes and thus a greater acceleration of the protons per revolution. The number of revolutions of the protons in the cyclotron could thus be reduced from approx. 200 to 186, and

882-432: A fuel would be so expensive it is likely that the fuel would require pyroprocessing to enable recovery of the N. It is likely that if the fuel was processed and dissolved in nitric acid that the nitrogen enriched with N would be diluted with the common N. Fluoride volatility is a method of reprocessing that does not rely on nitric acid, but it has only been demonstrated in relatively small scale installations whereas

1008-552: A good level of nuclear expertise and thus to training scientists and engineers in nuclear energy. For example, PSI maintains one of the few laboratories in Europe for investigating fuel rods in commercial reactors. The division works closely with ETH Zurich , EPFL and the University of Bern , using, for example, their high-performance computers or the CROCUS research reactor at EPFL. PSI

1134-455: A horse-riding accident. The eponymous Paul Scherrer Institute , based near Villigen in canton of Aargau , was established on 1 January 1988 by merging the 1960 established EIR ( Eidgenössisches Institut für Reaktorforschung , Federal Institute for Reactor Research) and the 1968 established SIN ( Schweizerisches Institut für Nuklearphysik , Swiss Institute for Nuclear Physics) with Jean-Pierre Blaser (SIN founder) named its first director. There

1260-453: A kernel of UO X fuel (sometimes UC or UCO), which has been coated with four layers of three isotropic materials deposited through fluidized chemical vapor deposition (FCVD). The four layers are a porous buffer layer made of carbon that absorbs fission product recoils, followed by a dense inner layer of protective pyrolytic carbon (PyC), followed by a ceramic layer of SiC to retain fission products at elevated temperatures and to give

1386-479: A kind of combined X-ray machine and microscope to screen a wide variety of substances. In the circular structure, the electrons move on a circular path 288 m in circumference, emitting synchrotron radiation in a tangential direction. A total of 350 magnets hold the electron beam on its course and focus it. Acceleration cavities ensure that the beam's speed remains constant. Paul Scherrer Paul Hermann Scherrer (3 February 1890 – 25 September 1969)

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1512-458: A myriad of these molecules in order, for example, to be able to metabolise, receive and transmit signals or to divide. The aim is to understand these life processes better and thus to be able to treat or prevent diseases more effectively. For example, PSI is investigating the structure of microtubules , filamentous structures which, among other things, pull apart chromosomes during cell division. They consist of long protein chains. When chemotherapy

1638-613: A properly designed reactor. Two such reactor designs are the prismatic-block gas-cooled reactor (such as the GT-MHR ) and the pebble-bed reactor (PBR). Both of these reactor designs are high temperature gas reactors (HTGRs). These are also the basic reactor designs of very-high-temperature reactors (VHTRs), one of the six classes of reactor designs in the Generation IV initiative that is attempting to reach even higher HTGR outlet temperatures. TRISO fuel particles were originally developed in

1764-412: A proton source based on cyclotron resonance, microwaves are used to strip electrons from hydrogen atoms. What remains are the hydrogen atomic nuclei, each consisting of only one proton. These protons leave the source with a potential of 60 kilovolts and are then subjected to a further voltage of 810 kilovolts in an accelerator tube. Both voltages are supplied by a Cockcroft-Walton accelerator . With

1890-401: A radioactive isotope. Its radiation can be localized with imaging techniques such as SPECT or PET , which enables the diagnosis of tumours and their metastases. Moreover, it can be dosed so that it also destroys the tumour cells. Several such radioactive substances have been developed at PSI. They are currently being tested in clinical trials, in close cooperation with universities, clinics and

2016-762: A reactor is plutonium, and some two thirds of this is fissile (c. 50% Pu , 15% Pu ). Metal fuels have the advantage of a much higher heat conductivity than oxide fuels but cannot survive equally high temperatures. Metal fuels have a long history of use, stretching from the Clementine reactor in 1946 to many test and research reactors. Metal fuels have the potential for the highest fissile atom density. Metal fuels are normally alloyed, but some metal fuels have been made with pure uranium metal. Uranium alloys that have been used include uranium aluminum, uranium zirconium , uranium silicon, uranium molybdenum, uranium zirconium hydride (UZrH), and uranium zirconium carbonitride. Any of

2142-420: A second spallation neutron source for the generation of ultracold neutrons (UCN). Unlike SINQ, it is pulsed and uses HIPA's full beam, but normally only for 8 seconds every 5 minutes. The design is similar to that of SINQ. In order to cool down the neutrons, however, it uses frozen deuterium at a temperature of 5 Kelvin (corresponding to −268 degrees Celsius) as a cold moderator. The UCN generated can be stored in

2268-859: A similar design to the CANDU but built by German KWU was originally designed for non-enriched fuel but since switched to slightly enriched fuel with a U content about 0.1 percentage points higher than in natural uranium. Various other nuclear fuel forms find use in specific applications, but lack the widespread use of those found in BWRs, PWRs, and CANDU power plants. Many of these fuel forms are only found in research reactors, or have military applications. Magnox (magnesium non-oxidising) reactors are pressurised, carbon dioxide –cooled, graphite - moderated reactors using natural uranium (i.e. unenriched) as fuel and Magnox alloy as fuel cladding. Working pressure varies from 6.9 to 19.35 bars (100.1 to 280.6 psi) for

2394-449: A small percentage of the U in the fuel absorbs excess neutrons and is transmuted into U . U rapidly decays into Np which in turn rapidly decays into Pu . The small percentage of Pu has a higher neutron cross section than U . As the Pu accumulates the chain reaction shifts from pure U at initiation of the fuel use to a ratio of about 70% U and 30% Pu at the end of

2520-409: A solid called ammonium diuranate , (NH 4 ) 2 U 2 O 7 . This is then heated ( calcined ) to form UO 3 and U 3 O 8 which is then converted by heating with hydrogen or ammonia to form UO 2 . The UO 2 is mixed with an organic binder and pressed into pellets. The pellets are then fired at a much higher temperature (in hydrogen or argon) to sinter the solid. The aim is to form

2646-438: A solid target. SINQ was one of the first facilities to use specially developed optical guide systems to transport slow neutrons. Metal-coated glass conduits guide neutrons over longer distances (a few tens of metres) by means of total reflection, analogous to the light guidance in glass fibres, with a low loss of intensity. The efficiency of these neutron guides has steadily increased with advances in manufacturing technology. This

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2772-637: A total of 870 kilovolts, the protons are accelerated to a speed of 46 million km/h or 4 percent of the speed of light. The protons are then fed into the Injector-2. With Injector-1, operating currents of 170 μA and peak currents of 200 μA could be reached. It was also used for low energy experiments, for OPTIS eye therapy and for the LiSoR experiment in the MEGAPIE project. Since December 1, 2010, this ring accelerator has been out of operation. The Injector-2, which

2898-505: A trillionth of a second (picosecond). For example, they have detected how certain proteins in the photoreceptors of the retina of our eyes are activated by light. While PSI's proton accelerator , which went into service in 1974, was primarily used in the early days for elementary particle physics , today the focus is on applications for solid-state physics , radiopharmaceuticals and cancer therapy. Since it started operating, it has been constantly developed further, and its performance today

3024-476: A typical core loading is on the order of 4500–6500 bundles, depending on the design. Modern types typically have 37 identical fuel pins radially arranged about the long axis of the bundle, but in the past several different configurations and numbers of pins have been used. The CANFLEX bundle has 43 fuel elements, with two element sizes. It is also about 10 cm (4 inches) in diameter, 0.5 m (20 in) long and weighs about 20 kg (44 lb) and replaces

3150-399: A typical spent fuel assembly still exceeds 10,000 rem/hour, resulting in a fatal dose in just minutes. Two main modes of release exist, the fission products can be vaporised or small particles of the fuel can be dispersed. Post-Irradiation Examination (PIE) is the study of used nuclear materials such as nuclear fuel. It has several purposes. It is known that by examination of used fuel that

3276-404: A way as to ensure low contamination with non-radioactive carbon (not a common fission product and absent in nuclear reactors that don't use it as a moderator ) then fluoride volatility could be used to separate the C produced by producing carbon tetrafluoride . C is proposed for use in particularly long lived low power nuclear batteries called diamond batteries . Much of what

3402-467: A wide range of applications are available for such investigations. Particle physicists are using some of the beamlines to perform high-precision measurements to test the limits of the Standard Model. The neutron source SINQ, which has been in operation since 1996, was the first, and is still the strongest, of its kind. It delivers a continuous neutron flux of 10 n cms. In SINQ the protons from

3528-700: Is a means to dispose of surplus plutonium by transmutation . Reprocessing of commercial nuclear fuel to make MOX was done in the Sellafield MOX Plant (England). As of 2015, MOX fuel is made in France at the Marcoule Nuclear Site , and to a lesser extent in Russia at the Mining and Chemical Combine , India and Japan. China plans to develop fast breeder reactors and reprocessing. The Global Nuclear Energy Partnership

3654-420: Is a street, Route Scherrer , named after Scherrer at CERN , Geneva . Nuclear fuel Nuclear fuel refers to any substance, typically fissile material, which is used by nuclear power stations or other nuclear devices to generate energy. For fission reactors, the fuel (typically based on uranium ) is usually based on the metal oxide ; the oxides are used rather than the metals themselves because

3780-475: Is able to release xenon gas, which normally acts as a neutron absorber ( Xe is the strongest known neutron poison and is produced both directly and as a decay product of I as a fission product ) and causes structural occlusions in solid fuel elements (leading to the early replacement of solid fuel rods with over 98% of the nuclear fuel unburned, including many long-lived actinides). In contrast, molten-salt reactors are capable of retaining

3906-484: Is as much as 2.4 mA, which is 24 times higher than the initial 100 μA. This is why the facility is now considered a high-performance proton accelerator, or HIPA (High Intensity Proton Accelerator) for short. Basically, it consists of three accelerators in series: the Cockcroft-Walton, the injector-2 cyclotron, and the ring-cyclotron. They accelerate the protons to around 80 percent of the speed of light . In

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4032-489: Is commonly composed of enriched uranium sandwiched between metal cladding. Plate-type fuel is used in several research reactors where a high neutron flux is desired, for uses such as material irradiation studies or isotope production, without the high temperatures seen in ceramic, cylindrical fuel. It is currently used in the Advanced Test Reactor (ATR) at Idaho National Laboratory , and the nuclear research reactor at

4158-410: Is compacted to cylindrical pellets and sintered at high temperatures to produce ceramic nuclear fuel pellets with a high density and well defined physical properties and chemical composition. A grinding process is used to achieve a uniform cylindrical geometry with narrow tolerances. Such fuel pellets are then stacked and filled into the metallic tubes. The metal used for the tubes depends on the design of

4284-590: Is done is the ITU which is the EU centre for the study of highly radioactive materials. Materials in a high-radiation environment (such as a reactor) can undergo unique behaviors such as swelling and non-thermal creep. If there are nuclear reactions within the material (such as what happens in the fuel), the stoichiometry will also change slowly over time. These behaviors can lead to new material properties, cracking, and fission gas release. The thermal conductivity of uranium dioxide

4410-566: Is formed into pellets and inserted into Zircaloy tubes that are bundled together. The Zircaloy tubes are about 1 centimetre (0.4 in) in diameter, and the fuel cladding gap is filled with helium gas to improve heat conduction from the fuel to the cladding. There are about 179–264 fuel rods per fuel bundle and about 121 to 193 fuel bundles are loaded into a reactor core. Generally, the fuel bundles consist of fuel rods bundled 14×14 to 17×17. PWR fuel bundles are about 4 m (13 ft) long. In PWR fuel bundles, control rods are inserted through

4536-450: Is known about uranium carbide is in the form of pin-type fuel elements for liquid metal fast reactors during their intense study in the 1960s and 1970s. Recently there has been a revived interest in uranium carbide in the form of plate fuel and most notably, micro fuel particles (such as tristructural-isotropic particles). The high thermal conductivity and high melting point makes uranium carbide an attractive fuel. In addition, because of

4662-413: Is low; it is affected by porosity and burn-up. The burn-up results in fission products being dissolved in the lattice (such as lanthanides ), the precipitation of fission products such as palladium , the formation of fission gas bubbles due to fission products such as xenon and krypton and radiation damage of the lattice. The low thermal conductivity can lead to overheating of the center part of

4788-500: Is one of the leading institutions worldwide in the research and application of proton therapy for the treatment of cancer. Since 1984, the Center for Proton Therapy has been successfully treating cancer patients with a special form of radiation therapy. To date, more than 7500 patients with ocular tumours have been irradiated (status 2020). The success rate for eye therapy using the OPTIS facility

4914-418: Is over 98 percent. In 1996, an irradiation unit (Gantry 1) was equipped for the first time to use the so-called spot-scanning proton technique developed at PSI. With this technique, tumours deep inside the body are scanned three-dimensionally with a proton beam about 5 to 7 mm in width. By superimposing many individual proton spots – about 10,000 spots per litre volume – the tumour is evenly exposed to

5040-462: Is the only place in the world where a muon beam of sufficient intensity is available at a very low energy of only a few kiloelectron volts – thanks to the Muon Source's high muon intensity and a special process. The resulting muons are slow enough to be used to analyse thin layers of material and surfaces. Six measuring stations (FLAME (from 2021), DOLLY, GPD, GPS, HAL-9500, and LEM) with instruments for

5166-495: Is used to treat cancer, it disturbs the assembly or breakdown of these chains so that the cancer cells can no longer divide. Researchers are closely observing the structure of these proteins and how they change to find out exactly where cancer drugs have to attack the microtubules. With the help of PSI's SwissFEL free-electron X-ray laser, which was inaugurated in 2016, researchers have been able to analyse dynamic processes in biomolecules with extremely high time resolution – less than

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5292-411: Is why PSI decided to carry out a comprehensive upgrade in 2019. When SINQ goes back into operation in summer 2020, it will be able to provide, on average, five times more neutrons for experiments, and in a special case, even 30 times more. SINQ's 15 instruments are not only used for PSI research projects but are also available for national and international users. Since 2011, PSI has also been operating

5418-529: The C concentration will be too low for use in nuclear batteries without enrichment. Nuclear graphite discharged from reactors where it was used as a moderator presents the same issue. Liquid fuels contain dissolved nuclear fuel and have been shown to offer numerous operational advantages compared to traditional solid fuel approaches. Liquid-fuel reactors offer significant safety advantages due to their inherently stable "self-adjusting" reactor dynamics. This provides two major benefits: virtually eliminating

5544-475: The University of Göttingen , graduating from there with a doctorate on the Faraday effect in the hydrogen molecule . In 1916, while still working on his dissertation, he and his tutor, Peter Debye , developed the “Debye–Scherrer powder method”, a procedure using X-rays for the structural analysis of crystals. This made an important contribution to the development of the scattering techniques that are still used in

5670-504: The University of Massachusetts Lowell Radiation Laboratory . Sodium-bonded fuel consists of fuel that has liquid sodium in the gap between the fuel slug (or pellet) and the cladding. This fuel type is often used for sodium-cooled liquid metal fast reactors. It has been used in EBR-I, EBR-II, and the FFTF. The fuel slug may be metallic or ceramic. The sodium bonding is used to reduce the temperature of

5796-404: The liquid fluoride thorium reactor (LFTR), this fuel salt is also the coolant; in other designs, such as the stable salt reactor , the fuel salt is contained in fuel pins and the coolant is a separate, non-radioactive salt. There is a further category of molten salt-cooled reactors in which the fuel is not in molten salt form, but a molten salt is used for cooling. Molten salt fuels were used in

5922-509: The 18 to 24 month fuel exposure period. Mixed oxide , or MOX fuel , is a blend of plutonium and natural or depleted uranium which behaves similarly (though not identically) to the enriched uranium feed for which most nuclear reactors were designed. MOX fuel is an alternative to low enriched uranium (LEU) fuel used in the light water reactors which predominate nuclear power generation. Some concern has been expressed that used MOX cores will introduce new disposal challenges, though MOX

6048-471: The 1980s. Today, the injector-2 delivers a beam current of ≈ 2.2 mA in routine operation and 2.4 mA in high current operation at 72 MeV, which is about 38 percent of the speed of light. Originally, two resonators were operated at 150 MHz in flat-top mode to enable a clear separation of the proton orbits, but these are now also used for acceleration. Part of the extracted 72 MeV proton beam can be split off for isotope production, while

6174-499: The 37-pin standard bundle. It has been designed specifically to increase fuel performance by utilizing two different pin diameters. Current CANDU designs do not need enriched uranium to achieve criticality (due to the lower neutron absorption in their heavy water moderator compared to light water), however, some newer concepts call for low enrichment to help reduce the size of the reactors. The Atucha nuclear power plant in Argentina,

6300-567: The Diorit research reactor, which was operated from 1960 to 1977, to develop a new generation of fuel element types for nuclear power plants. This, however, never happened. By the time it was decided, in 2011, to phase out nuclear power, it had become clear that there was no further use for the material in Switzerland. The Federal Council decided at the Nuclear Security Summit in 2014 to close

6426-507: The ESI (Energy System Integration) experimental platform to answer specific questions on seasonal energy storage and sector coupling . The platform can be used in research and industry to test promising approaches to integrating renewable energies into the energy system – for example, storing excess electricity from solar or wind power in the form of hydrogen or methane . At PSI a method for extracting significantly more methane gas from biowaste

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6552-775: The Hönggerberg near Zurich, which at the time was jointly operated by ETH Zurich and PSI. In 2009, the Indian-born British structural biologist Venkatraman Ramakrishnan was awarded the Nobel Prize in Chemistry for, among other things, his research at the Synchrotron Light Source Switzerland (SLS). The SLS is one of PSI's four large-scale research facilities. His investigations there enabled Ramakrishnan to clarify what ribosomes look like and how they function at

6678-521: The LFTR known as the Molten Salt Reactor Experiment, as well as other liquid core reactor experiments. The liquid fuel for the molten salt reactor was a mixture of lithium, beryllium, thorium and uranium fluorides: LiF-BeF 2 -ThF 4 -UF 4 (72-16-12-0.4 mol%). It had a peak operating temperature of 705 °C in the experiment, but could have operated at much higher temperatures since

6804-530: The River Aare served as national centres for research: one focusing on nuclear energy and the other on nuclear and particle physics. Over the years, research at the centres expanded into other areas, and nuclear and reactor physics accounts for just 11 percent of the research work at PSI today. Since Switzerland decided in 2011 to phase out nuclear energy, this research has primarily been concerned with questions of safety, such as how to store radioactive waste safely in

6930-520: The Russian satellite Spectrum X-G, and later also supplied NASA and ESA with detectors to analyse radiation in space. In 1992, physicists used accelerator mass spectrometry and radiocarbon methods to determine the age of Ötzi , the mummy found in a glacier in the Ötztal Alps a year earlier, from small samples of just a few milligrams of bone, tissue and grass. They were analysed at the TANDEM accelerator on

7056-722: The Standard Model. Examples include the upper limit measured in the MEG experiment of the hypothetical decay of positive muons into positrons and photons as well as that of the permanent electric dipole moment for neutrons. Muons are not only useful in particle physics, but also in solid-state physics and materials science. The muon spin spectroscopy method (μSR) is used to investigate the fundamental properties of magnetic and superconducting materials as well as of semiconductors , insulators and semiconductor structures, including technologically relevant applications such as for solar cells. PSI researchers are addressing all aspects of energy use with

7182-462: The Standard Model. Particle physics at PSI holds many records, including the most precise determination of the coupling constants of the weak interaction and the most accurate measurement of the charge radius of the proton. Some experiments aim to find effects that are not foreseen in the Standard Model, but which could correct inconsistencies in the theory or solve unexplained phenomena from astrophysics and cosmology. Their results so far agree with

7308-723: The Swiss Commission for Atomic Sciences in 1958. In addition, Scherrer took part in establishing CERN near Geneva in 1952–54. When established he became one of the original members of the Scientific Policy Committee, at which he served until the end of 1963, and the CERN Council. Furthermore, he participated in setting up Reaktor AG, to study the construction and operation of nuclear fission facilities one year later, in Würenlingen . His abilities and foresight led to

7434-785: The Swiss Federal Council and head of the Swiss military department. In parallel with his main professional occupation as a researcher and leader of an institution, Paul Scherrer also served in various institutions and committees involved in the dissemination of nuclear energy in Switzerland : the Swiss Federal Council appointed him to the post of President of the Swiss Study Commission on Atomic Energy ( Schweizerischen Studienkommission für Atomenergie) in 1946, and President of

7560-583: The Swiss plutonium storage facility. A bilateral agreement between the two countries meant the plutonium could then be transferred to the US for further storage. In July 2017, the three-dimensional alignment of magnetization inside a three-dimensional magnetic object was investigated and visualized with the help of the SLS without affecting the material. The technology is expected to be useful in developing better magnets, for example for motors or data storage. Joël François Mesot,

7686-475: The TRISO particle more structural integrity, followed by a dense outer layer of PyC. TRISO particles are then encapsulated into cylindrical or spherical graphite pellets. TRISO fuel particles are designed not to crack due to the stresses from processes (such as differential thermal expansion or fission gas pressure) at temperatures up to 1600 °C, and therefore can contain the fuel in the worst of accident scenarios in

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7812-478: The US and an additional 35 in other countries. In a fast-neutron reactor , the minor actinides produced by neutron capture of uranium and plutonium can be used as fuel. Metal actinide fuel is typically an alloy of zirconium, uranium, plutonium, and minor actinides . It can be made inherently safe as thermal expansion of the metal alloy will increase neutron leakage. Molten plutonium, alloyed with other metals to lower its melting point and encapsulated in tantalum ,

7938-491: The USA. According to a newspaper report, the federal government had a secret plutonium storage facility in which the material had been kept since the 1960s to construct an atomic bomb as planned at the time. The Federal Council denied this, maintaining the plutonium-239 content of the material was below 92 percent, which meant it was not weapons-grade material. The idea was rather to use the material obtained from reprocessed fuel rods of

8064-821: The United Kingdom as part of the Dragon reactor project. The inclusion of the SiC as diffusion barrier was first suggested by D. T. Livey. The first nuclear reactor to use TRISO fuels was the Dragon reactor and the first powerplant was the THTR-300 . Currently, TRISO fuel compacts are being used in some experimental reactors, such as the HTR-10 in China and the high-temperature engineering test reactor in Japan. In

8190-456: The United States information about German science and German scientists, especially related to efforts to develop a nuclear weapon . Scherrer later became the foremost proponent of Switzerland developing its own nuclear weapons with enriched uranium supplied by Belgian Congo , a program which was pursued by the government for 43 years and abandoned in 1988 by Arnold Koller , then member of

8316-452: The United States, spherical fuel elements utilizing a TRISO particle with a UO 2 and UC solid solution kernel are being used in the Xe-100 , and Kairos Power is developing a 140 MWE nuclear reactor that uses TRISO. In QUADRISO particles a burnable neutron poison ( europium oxide or erbium oxide or carbide ) layer surrounds the fuel kernel of ordinary TRISO particles to better manage

8442-401: The absence of oxygen in this fuel (during the course of irradiation, excess gas pressure can build from the formation of O 2 or other gases) as well as the ability to complement a ceramic coating (a ceramic-ceramic interface has structural and chemical advantages), uranium carbide could be the ideal fuel candidate for certain Generation IV reactors such as the gas-cooled fast reactor . While

8568-515: The aforementioned fuels can be made with plutonium and other actinides as part of a closed nuclear fuel cycle. Metal fuels have been used in light-water reactors and liquid metal fast breeder reactors , such as Experimental Breeder Reactor II . TRIGA fuel is used in TRIGA (Training, Research, Isotopes, General Atomics ) reactors. The TRIGA reactor uses UZrH fuel, which has a prompt negative fuel temperature coefficient of reactivity , meaning that as

8694-431: The aim to make energy supplies more sustainable. Focus areas include: new technologies for renewable energies , low-loss energy storage, energy efficiency , low-pollution combustion, fuel cells , experimental and model-based assessment of energy and material cycles, environmental impacts of energy production and consumption, and nuclear energy research, in particular reactor safety and waste management . PSI operates

8820-424: The application of the new fuel-cladding material systems for various types of ATF materials. The aim of the research is to develop nuclear fuels that can tolerate loss of active cooling for a considerably longer period than the existing fuel designs and prevent or delay the release of radionuclides during an accident. This research is focused on reconsidering the design of fuel pellets and cladding, as well as

8946-541: The approximately 40 measuring stations in these facilities. In recent years, the institute has been one of the largest recipients of money from the Swiss lottery fund. The institute, named after the Swiss physicist Paul Scherrer , was created in 1988 when EIR ( Eidgenössisches Institut für Reaktorforschung , Swiss Federal Institute for Reactor Research, founded in 1960) was merged with SIN ( Schweizerisches Institut für Nuklearphysik , Swiss Institute for Nuclear Research, founded in 1968). The two institutes on opposite sides of

9072-420: The boiling point of the molten salt was in excess of 1400 °C. The aqueous homogeneous reactors (AHRs) use a solution of uranyl sulfate or other uranium salt in water. Historically, AHRs have all been small research reactors, not large power reactors. The dual fluid reactor (DFR) has a variant DFR/m which works with eutectic liquid metal alloys, e.g. U-Cr or U-Fe. Uranium dioxide (UO 2 ) powder

9198-420: The chain-reaction. This mechanism compensates for the accumulation of undesirable neutron poisons which are an unavoidable part of the fission products, as well as normal fissile fuel "burn up" or depletion. In the generalized QUADRISO fuel concept the poison can eventually be mixed with the fuel kernel or the outer pyrocarbon. The QUADRISO concept was conceived at Argonne National Laboratory . RBMK reactor fuel

9324-510: The coolant and contaminating it. Besides the prevention of radioactive leaks this also serves to keep the coolant as non-corrosive as feasible and to prevent reactions between chemically aggressive fission products and the coolant. For example, the highly reactive alkali metal caesium which reacts strongly with water, producing hydrogen, and which is among the more common fission products. Pressurized water reactor (PWR) fuel consists of cylindrical rods put into bundles. A uranium oxide ceramic

9450-403: The distance travelled by the protons in the cyclotron decreased from 6 km to 4 km. With a beam current of 2.2 mA, this proton facility at PSI is currently the most powerful continuous particle accelerator in the world. The 1.3 MW strong proton beam is directed towards the muon source (SμS) and the spallation neutron source (SINQ). In the middle of the large experimental hall,

9576-585: The early age of 30. In 1925, he organised the first international conference of physicists to take place after the First World War . He became Principal of the Physical Institute at ETH in 1927 and focused its direction on nuclear physics, a research branch that was still coming into being at that stage. The first cyclotron at ETH Zurich was built under his direction in 1940. Beginning in late 1944, Scherrer became close to Moe Berg and, through Berg, gave

9702-514: The early development of new branches of solid-state physics , particle physics and electronics , which made a vital contribution to the high standard of research at Swiss universities. When Scherrer was made emeritus professor in 1960, after 40 years at ETH Zurich, he took up a teaching appointment at the University of Basel and his former students and friends put together a Festschrift . In 1922 Scherrer married Ina Sonderegger, with whom he had two daughters. He died on 25 September 1969 after

9828-434: The established PUREX process is used commercially for about a third of all spent nuclear fuel (the rest being largely subject to a "once through fuel cycle"). All nitrogen-fluoride compounds are volatile or gaseous at room temperature and could be fractionally distilled from the other gaseous products (including recovered uranium hexafluoride ) to recover the initially used nitrogen. If the fuel could be processed in such

9954-491: The excess of reactivity. If the core is equipped both with TRISO and QUADRISO fuels, at beginning of life neutrons do not reach the fuel of the QUADRISO particles because they are stopped by the burnable poison. During reactor operation, neutron irradiation of the poison causes it to "burn up" or progressively transmute to non-poison isotopes, depleting this poison effect and leaving progressively more neutrons available for sustaining

10080-406: The facility and observed for a few minutes in experiments. This superconducting 250 MeV cyclotron has been in operation for proton therapy since 2007 and provides the beam for treating tumours in cancer patients. It was the first superconducting cyclotron worldwide to be used for proton therapy. Previously, part of the proton beam from the Ring Cyclotron was split off for this purpose, but since 2007

10206-407: The fact that the used fuel can be cracked, it is very insoluble in water, and is able to retain the vast majority of the actinides and fission products within the uranium dioxide crystal lattice . The radiation hazard from spent nuclear fuel declines as its radioactive components decay, but remains high for many years. For example 10 years after removal from a reactor, the surface dose rate for

10332-412: The failure modes which occur during normal use (and the manner in which the fuel will behave during an accident) can be studied. In addition information is gained which enables the users of fuel to assure themselves of its quality and it also assists in the development of new fuels. After major accidents the core (or what is left of it) is normally subject to PIE to find out what happened. One site where PIE

10458-403: The fuel being changed every three years or so, about half of the Pu is 'burned' in the reactor, providing about one third of the total energy. It behaves like U and its fission releases a similar amount of energy. The higher the burnup , the more plutonium is present in the spent fuel, but the available fissile plutonium is lower. Typically about one percent of the used fuel discharged from

10584-403: The fuel is similar to PWR fuel except that the bundles are "canned". That is, there is a thin tube surrounding each bundle. This is primarily done to prevent local density variations from affecting neutronics and thermal hydraulics of the reactor core. In modern BWR fuel bundles, there are either 91, 92, or 96 fuel rods per assembly depending on the manufacturer. A range between 368 assemblies for

10710-850: The fuel mixture for significantly extended periods, which increases fuel efficiency dramatically and incinerates the vast majority of its own waste as part of the normal operational characteristics. A downside to letting the Xe escape instead of allowing it to capture neutrons converting it to the basically stable and chemically inert Xe , is that it will quickly decay to the highly chemically reactive, long lived radioactive Cs , which behaves similar to other alkali metals and can be taken up by organisms in their metabolism. Molten salt fuels are mixtures of actinide salts (e.g. thorium/uranium fluoride/chloride) with other salts, used in liquid form above their typical melting points of several hundred degrees C. In some molten salt-fueled reactor designs, such as

10836-408: The fuel of choice for reactor designs that NASA produces. One advantage is that uranium nitride has a better thermal conductivity than UO 2 . Uranium nitride has a very high melting point. This fuel has the disadvantage that unless N was used (in place of the more common N ), a large amount of C would be generated from the nitrogen by the (n,p) reaction . As the nitrogen needed for such

10962-406: The fuel rods, standing between the coolant and the nuclear fuel. It is made of a corrosion -resistant material with low absorption cross section for thermal neutrons , usually Zircaloy or steel in modern constructions, or magnesium with small amount of aluminium and other metals for the now-obsolete Magnox reactors . Cladding prevents radioactive fission fragments from escaping the fuel into

11088-532: The fuel. Accident tolerant fuels (ATF) are a series of new nuclear fuel concepts, researched in order to improve fuel performance under accident conditions, such as loss-of-coolant accident (LOCA) or reaction-initiated accidents (RIA). These concerns became more prominent after the Fukushima Daiichi nuclear disaster in Japan, in particular regarding light-water reactor (LWR) fuels performance under accident conditions. Neutronics analyses were performed for

11214-673: The help of the SLS. This optical pigment acts as a kind of light sensor and plays a decisive role in the process of sight. A so-called ‘barrel pixel detector’ built at PSI was a central element in the CMS detector at the Geneva nuclear research centre CERN , and was thus involved in detecting the Higgs boson. This discovery, announced on 4 July 2012, was awarded the Nobel Prize in Physics one year later. In January 2016, 20 kilograms of plutonium were taken from PSI to

11340-468: The interactions between the two. Used nuclear fuel is a complex mixture of the fission products , uranium , plutonium , and the transplutonium metals . In fuel which has been used at high temperature in power reactors it is common for the fuel to be heterogeneous ; often the fuel will contain nanoparticles of platinum group metals such as palladium . Also the fuel may well have cracked, swollen, and been heated close to its melting point. Despite

11466-422: The interior of materials on a scale ranging from the size of atoms to objects a centimetre long. They therefore serve as ideal probes for investigating fundamental and applied research topics, such as quantum spin systems and their potential for application in future computer technologies, the functionalities of complex lipid membranes and their use for the transport and targeted release of drug substances, as well as

11592-465: The introduction of additional absorbers. CerMet fuel consists of ceramic fuel particles (usually uranium oxide) embedded in a metal matrix. It is hypothesized that this type of fuel is what is used in United States Navy reactors. This fuel has high heat transport characteristics and can withstand a large amount of expansion. Plate-type fuel has fallen out of favor over the years. Plate-type fuel

11718-524: The large facilities at the Paul Scherrer Institute to this day. Debye received the Nobel Prize in Chemistry for this work in 1936. He is perhaps best known for determining the inverse relationship between the width of an X-ray diffraction peak and the crystallite size . This work was published in 1918. ETH Zurich appointed Scherrer to the post of Professor of Experimental Physics in 1920, at

11844-401: The large particle accelerator strike a lead target and knock the neutrons out of the lead nuclei, making them available for experiments. In addition to thermal neutrons , a moderator made of liquid deuterium also enables the production of slow neutrons, which have a lower energy spectrum . The MEGAPIE Target ( Mega watt Pi lot- E xperiment) came into operation in summer 2006. By replacing

11970-442: The level of individual molecules. Using the information encoded in the genes, ribosomes produce proteins that control many chemical processes in living organisms. In 2010, an international team of researchers at PSI used negative muons to perform a new measurement of the proton and found that its radius is significantly smaller than previously thought: 0.84184 femtometers instead of 0.8768. According to press reports, this result

12096-470: The long-standing Director of PSI (2008 to 2018), was elected President of ETH Zurich at the end of 2018. His post was temporarily taken over by the physicist and PSI Chief of Staff Thierry Strässle from January 2019. Since 1 April 2020, the physicist Christian Rüegg has been Director of PSI. He was previously head of the PSI research division Neutrons and Muons. Numerous PSI spin-off companies have been founded over

12222-422: The main part is fed into the Ring Cyclotron for further acceleration. Like the Injector-2, the Ring Cyclotron, which has a circumference of about 48 m, went into operation in 1974. It was specially developed at SIN and is at the heart of the PSI proton accelerator facilities. The protons are accelerated to 80 percent of the speed of light on the approximately 4 km long track, which the protons cover inside

12348-520: The manufacturer of metal-organic frameworks novoMOF or the drug developer leadXpro, have settled close to PSI in the Park Innovaare, which was founded in 2015 with the support of several companies and Canton Aargau. PSI develops, builds and operates several accelerator facilities , e. g. a 590 MeV high-current cyclotron , which in normal operation supplies a beam current of about 2.2 mA. PSI also operates four large-scale research facilities:

12474-485: The medical facility has been producing its own proton beam independently, which supplies several irradiation stations for therapy. Other components of the facility, the peripheral equipment and the control systems have also been improved in the meantime, so that today the facility is available over 98 percent of the time with more than 7000 operating hours per year. The Swiss Light Source (SLS), an electron synchrotron , has been in operation since 1 August 2001. It works like

12600-409: The muon source is able to generate the world's most intense muon beams. These enable researchers to conduct experiments in particle physics and materials science that cannot be carried out anywhere else. The Swiss Muon Source (SμS) has seven beamlines that scientists can use to investigate various aspects of modern physics. Some materials scientists use them for muon spin spectroscopy experiments. PSI

12726-505: The necessary radiation dose, which is monitored individually for each spot. This allows an extremely precise, homogeneous irradiation that is optimally adapted to the usually irregular shape of the tumour. The technique enables as much as possible of the surrounding healthy tissue to be spared. The first gantry was in operation for patients from 1996 to the end of 2018. In 2013, the second Gantry 2, developed at PSI, went into operation, and in mid-2018 another treatment station, Gantry 3,

12852-420: The neutron cross section of carbon is low, during years of burnup, the predominantly C will undergo neutron capture to produce stable C as well as radioactive C . Unlike the C produced by using uranium nitrate, the C will make up only a small isotopic impurity in the overall carbon content and thus make the entirety of the carbon content unsuitable for non-nuclear uses but

12978-407: The oxide melting point is much higher than that of the metal and because it cannot burn, being already in the oxidized state. Uranium dioxide is a black semiconducting solid. It can be made by heating uranyl nitrate to form UO 2 . This is then converted by heating with hydrogen to form UO 2 . It can be made from enriched uranium hexafluoride by reacting with ammonia to form

13104-448: The pharmaceutical industry. PSI also supplies local hospitals with radiopharmaceuticals if required. Since the opening of the Synchrotron Light Source Switzerland (SLS), structural biology has been a further focus of research in the field of human health. Here, the structure and function of biomolecules are being investigated – preferably at atomic resolution. The PSI researchers are primarily concerned with proteins. Every living cell needs

13230-500: The pollutant emissions of various energy production processes and the behaviour of the corresponding substances in the atmosphere, PSI also operates a smog chamber. Another area of research at PSI is on the effects of energy production on the atmosphere locally, including in the Alps, in the polar regions of the Earth and in China. The Nuclear Energy and Safety Division is dedicated to maintaining

13356-486: The possibility of a runaway reactor meltdown, and providing an automatic load-following capability which is well suited to electricity generation and high-temperature industrial heat applications. In some liquid core designs, the fuel can be drained rapidly into a passively safe dump-tank. This advantage was conclusively demonstrated repeatedly as part of a weekly shutdown procedure during the highly successful Molten-Salt Reactor Experiment from 1965 to 1969. A liquid core

13482-740: The properties of a material. Most of the researchers in the field of matter and materials at PSI want to find out more about how the internal structure of different materials relates to their observable properties. Fundamental research in this area contributes to the development of new materials with a wide range of applications, for example in electrical engineering , medicine , telecommunications , mobility , new energy storage systems, quantum computers and spintronics . The phenomena investigated include superconductivity , ferro- and anti ferromagnetism , spin fluids and topological insulators . Neutrons are intensively used for materials research at PSI because they enable unique and non-destructive access to

13608-402: The proton beam of the Ring Cyclotron collides with two targets – rings of carbon . During the collisions of the protons with the atomic carbon nuclei, pions are first formed and then decay into muons after about 26 billionths of a second. Magnets then direct these muons to instruments used in materials science and particle physics. Thanks to the Ring Cyclotron's enormously high proton current,

13734-410: The reactor. Stainless steel was used in the past, but most reactors now use a zirconium alloy which, in addition to being highly corrosion-resistant, has low neutron absorption. The tubes containing the fuel pellets are sealed: these tubes are called fuel rods . The finished fuel rods are grouped into fuel assemblies that are used to build up the core of a power reactor. Cladding is the outer layer of

13860-504: The ring in 186 laps. This corresponds to a kinetic energy of 590 MeV. Only three such rings exist worldwide, namely: TRIUMF in Vancouver, Canada; LAMPF in Los Alamos, USA; and the one at PSI. TRIUMF has only reached beam currents of 500 μA and LAMPF 1 mA. In addition to the four original Cavities , a smaller fifth cavity was added in 1979. It is operated at 150 megahertz as

13986-496: The smallest and 800 assemblies for the largest BWR in the U.S. form the reactor core. Each BWR fuel rod is backfilled with helium to a pressure of about 3 standard atmospheres (300 kPa). Canada deuterium uranium fuel (CANDU) fuel bundles are about 0.5 metres (20 in) long and 10 centimetres (4 in) in diameter. They consist of sintered (UO 2 ) pellets in zirconium alloy tubes, welded to zirconium alloy end plates. Each bundle weighs roughly 20 kilograms (44 lb), and

14112-467: The solid target with a target made of a lead-bismuth eutectic , the neutron yield could be increased by about another 80%. Since it would be very costly to dispose of the MEGAPIE target, PSI decided in 2009 not to produce another such target and instead to develop the solid target further as it had already proven its worth. Based on the findings from the MEGAPIE project, it was possible to obtain almost as large an increase in neutron yield for operation with

14238-587: The steel pressure vessels, and the two reinforced concrete designs operated at 24.8 and 27 bars (24.5 and 26.6 atm). Magnox alloy consists mainly of magnesium with small amounts of aluminium and other metals—used in cladding unenriched uranium metal fuel with a non-oxidising covering to contain fission products. This material has the advantage of a low neutron capture cross-section, but has two major disadvantages: Magnox fuel incorporated cooling fins to provide maximum heat transfer despite low operating temperatures, making it expensive to produce. While

14364-490: The structure of novel materials for energy storage as key components in intelligent energy networks. In particle physics , PSI researchers are investigating the structure and properties of the innermost layers of matter and what holds them together. Muons, pions and ultra-cold neutrons are used to test the Standard Model of elementary particles, to determine fundamental natural constants and to test theories that go beyond

14490-560: The temperature of the core increases, the reactivity decreases—so it is highly unlikely for a meltdown to occur. Most cores that use this fuel are "high leakage" cores where the excess leaked neutrons can be utilized for research. That is, they can be used as a neutron source . TRIGA fuel was originally designed to use highly enriched uranium, however in 1978 the U.S. Department of Energy launched its Reduced Enrichment for Research Test Reactors program, which promoted reactor conversion to low-enriched uranium fuel. There are 35 TRIGA reactors in

14616-449: The top directly into the fuel bundle. The fuel bundles usually are enriched several percent in U. The uranium oxide is dried before inserting into the tubes to try to eliminate moisture in the ceramic fuel that can lead to corrosion and hydrogen embrittlement . The Zircaloy tubes are pressurized with helium to try to minimize pellet-cladding interaction which can lead to fuel rod failure over long periods. In boiling water reactors (BWR),

14742-407: The use of uranium metal rather than oxide made nuclear reprocessing more straightforward and therefore cheaper, the need to reprocess fuel a short time after removal from the reactor meant that the fission product hazard was severe. Expensive remote handling facilities were required to address this issue. Tristructural-isotropic (TRISO) fuel is a type of micro-particle fuel. A particle consists of

14868-505: The years to make the research findings available to the wider society. The largest spin-off, with 120 employees, is the DECTRIS AG , founded in 2006 in nearby Baden, which specializes in the development and marketing of X-ray detectors. SwissNeutronics AG in Klingnau, which sells optical components for neutron research facilities, was founded as early as 1999. Several recent PSI offshoots, such as

14994-675: Was a Swiss physicist . Born in St. Gallen , Switzerland, he studied at Göttingen , Germany, before becoming a lecturer there. Later, Scherrer became head of the Department of Physics at ETH Zurich . Paul Scherrer was born in St. Gallen . In 1908, he enrolled at the Swiss Federal Polytechnic (later known as ETH Zurich ), changing course from Botany to Mathematics and Physics after two semesters. In 1912, Scherrer spent one semester at Königsberg University , then undertook further studies at

15120-560: Was a U.S. proposal in the George W. Bush administration to form an international partnership to see spent nuclear fuel reprocessed in a way that renders the plutonium in it usable for nuclear fuel but not for nuclear weapons. Reprocessing of spent commercial-reactor nuclear fuel has not been permitted in the United States due to nonproliferation considerations . All other reprocessing nations have long had nuclear weapons from military-focused research reactor fuels except for Japan. Normally, with

15246-472: Was commissioned in 1984 and developed by what was then SIN, replaced the Injector-1 as the injection machine for the 590 MeV ring cyclotron. Initially, it was possible to operate Injector-1 and Injector-2 alternately, but now only Injector-2 is used to feed the proton beam into the ring. The new cyclotron has enabled an increase in the beam current from 1 to 2 mA, which was the absolute record value for

15372-595: Was developed and successfully tested with the help of the ESI platform together with the Zurich power company Energie 360°. The team was awarded the Watt d'Or 2018 of the Swiss Federal Office of Energy . A platform for catalyst research is also maintained at PSI. Catalysis is a central component in various energy conversion processes, for example in fuel cells, water electrolysis and the methanation of carbon dioxide. To test

15498-414: Was not only surprising, it could also call previous models in physics into question. The measurements were only possible with PSI's 590 MeV proton accelerator HIPA because its secondarily generated muon beam is the only one worldwide that is intense enough to conduct the experiment. In 2011, researchers from PSI and elsewhere succeeded in deciphering the basic structure of the protein molecule rhodopsin with

15624-586: Was opened. In the field of radiopharmacy , PSI's infrastructure covers the entire spectrum. In particular, PSI researchers are tackling very small tumours distributed throughout the body. These cannot be treated with the usual radiotherapy techniques. New medically applicable radionuclides have, however, been produced with the help of the proton accelerators and the neutron source SINQ at PSI. When combined for therapy with special biomolecules ( antibodies ), therapeutic molecules can be formed to selectively and specifically detect tumour cells. These are then labelled with

15750-400: Was tested in two experimental reactors, LAMPRE I and LAMPRE II, at Los Alamos National Laboratory in the 1960s. LAMPRE experienced three separate fuel failures during operation. Ceramic fuels other than oxides have the advantage of high heat conductivities and melting points, but they are more prone to swelling than oxide fuels and are not understood as well. Uranium nitride is often

15876-548: Was used in Soviet -designed and built RBMK -type reactors. This is a low-enriched uranium oxide fuel. The fuel elements in an RBMK are 3 m long each, and two of these sit back-to-back on each fuel channel, pressure tube. Reprocessed uranium from Russian VVER reactor spent fuel is used to fabricate RBMK fuel. Following the Chernobyl accident, the enrichment of fuel was changed from 2.0% to 2.4%, to compensate for control rod modifications and

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