physics

Lucens reactor

Lucens reactor is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lucens reactor rather than just read about it. In short: The Lucens reactor was an experimental nuclear power reactor built next to Lucens, Vaud, Switzerland. After its connection to the electrical grid on 29 January 1968, the reactor only operated for a year before it suffered an accident on 21 January 1969.

Key takeaways

Lucens reactor belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lucens reactor to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lucens reactor from memory before moving on to harder problems.

Reference excerpt

The Lucens reactor was an experimental nuclear power reactor built next to Lucens, Vaud, Switzerland. After its connection to the electrical grid on 29 January 1968, the reactor only operated for a year before it suffered an accident on 21 January 1969. The cause was a corrosion-induced loss of heat dispersal leading to the destruction of a pressure tube which caused an adjacent pressure tube to fail, and partial meltdown of the core, resulting in radioactive contamination of the cavern.

History

Background After international breakthroughs in Nuclear technology after the Second World War the Swiss federal government sought to participate in this field as well. As a result it launched an extensive funding and research program. The main goal of this program was the construction of a Swiss made nuclear reactor. In this context three industry groups were founded who applied for funding, each with their own project for a nuclear reactor. In September 1959 the Swiss Federal Council urged them to merge their projects and work together to develop a Swiss made experimental reactor, as a result the Nationale Gesellschaft zur Förderung der industriellen Atomtechnik (transl. National Society for the Promotion of Industrial Nuclear Technology, NGA) was founded. To contribute to the funding of such projects the Federal Assembly passed a federal decree on 15 May 1960 that allowed the Federal Council to contribute up to 50 million Swiss francs to the construction and experimental operation of prototype power reactors. In 1960 the Eidgenössische Kommission für die Sicherheit der Atomanlagen, transl. Federal Nuclear Safety Commission was founded to oversee the new nuclear reactors.

Construction In May 1962, the definitive decision to build was made and construction started later the same year on 1 April. In the following five years the experimental reactor was constructed near the town of Lucens. The reactor, turbine and fuel rod storage were built into three different caverns for security reasons.

Commissioning and early operation The reactor became critical for the first time on 29 December 1966. During 1967 diverse commissioning attempts as well as completion and improvement work took place. Beginning in early 1968, the reactor's power output was increased in stages until it was tested in a ten-day endurance test in April/ May. With the test the reactors construction and testing phase was completed and in 1968 the finished reactor was handed over to Energie Ouest Suisse (EOS), the operator of the reactor. The EOS then operated the reactor between mid-August and late October 1968 continuously in a provisional configuration. Operations were then suspended to allow repairs and technical modifications.

Reactor design The heavy-water moderated, carbon dioxide gas-cooled pressure tube reactor produced 28 megawatts (MW) of heat, which was used to generate 6 MW of electricity. It consisted out of 73 fuel rods, each in their own carbon dioxide filled pressure tube. The tubes were housed within a moderator tank filled with heavy water. Since enriched uranium at the time was only available in the US and Switzerland sought to remain independent the reactor was designed to use natural uranium as fuel, which at the time was hoped to be sourceable in Switzerland as well. It was fueled by 0.96% natural uranium alloyed with chromium cased in magnesium alloy (magnesium with 0.6% zirconium) inserted into a graphite matrix. Carbon dioxide gas was pumped into the top of the channels at 6.28 megapascals (MPa) and 223 °C and exited the channels at a pressure of 5.79 MPa and at a temperature of 378 °C.

1969 nuclear accident On 21 January 1969, the reactor was started for regular operation when it suffered a loss-of-coolant accident, leading to a partial core meltdown and the radioactive contamination of the cavern, which was then sealed. The meltdown was caused by water entering the pressure tubes, where it corroded the magnesium tubes. The resulting corrosion products accumulated in some fuel channels, restricting the flow of the CO2 cooling gas in them, inhibiting the cooling of the fuel, causing it to overheat, catch fire and partially melt. No irradiation of workers or the population occurred, though the reactor's cavern was seriously contaminated. Using the criteria of the International Nuclear Event Scale (INES), introduced in 1990, the event has been assessed between level 4, "Accident with local consequences" and level 5, "Accident with wider consequences".

Background Starting on 24 October 1968, the reactor went into maintenance during which its cooling system was improved, with work continuing for several months. One month before the accident the federal government issued the permanent operating license on 23 December 1968. The Swiss nuclear safety commission found that the reactor's fuel elements were potentially vulnerable to malfunction and supported the manufacturers recommendation that the reactor should be operated avoiding thermal fluctuation. On 21 January the reactor was supposed to start its definitive regular operation.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Lucens reactor

Start with the simplest possible case. Write down what Lucens reactor claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lucens reactor before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lucens reactor ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lucens reactor

In research: Lucens reactor appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lucens reactor in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lucens reactor is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1962 establishments in Switzerland, 1969 disestablishments in Switzerland, Buildings and structures in Vaud, so understanding it makes those chapters shorter.
In everyday life: Look for Lucens reactor outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lucens reactor in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lucens reactor means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lucens reactor out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lucens reactor in simple terms?

Why does Lucens reactor matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lucens reactor?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lucens reactor.