Lucens (French pronunciation: [lysɑ̃s]) is a municipality in the Broye-Vully district in the canton of Vaud in Switzerland.

It was a pilot project to test a heavy-water moderated, carbon dioxide gas-cooled reactor.

Soon after the initial start up, an undetected blockage in one of the cooling pipes led to a partial fuel meltdown and massive radioactive contamination of the underground site.

[6] Before the merger Lucens had an area, (as of the 2004/09 survey) of 7.83 square kilometers (3.02 sq mi).

Over the same time period, the amount of recreational space in the municipality decreased by 1 ha (2.5 acres) and is now about 0.38% of the total area.

Over the same time period the amount of forested land has decreased by 5 ha (12 acres).

[10] The blazon of the municipal coat of arms is Per bend Argent and Gules, overall a Sun in his splendour Or.

[13] The age distribution, as of 2009[update], in Lucens is; 256 children or 11.1% of the population are between 0 and 9 years old and 284 teenagers or 12.3% are between 10 and 19.

[14] The historical population is given in the following chart:[4][18] Lucens Castle is listed as a Swiss heritage site of national significance.

The entire town of Lucens is part of the Inventory of Swiss Heritage Sites.

In the federal election, a total of 542 votes were cast, and the voter turnout was 34.6%.

[20] In the 2007 federal election the most popular party was the SVP which received 29.38% of the vote.

In the federal election, a total of 494 votes were cast, and the voter turnout was 41.2%.

[21] Lucens is an industrial community, or a municipality where manufacturing provides over a quarter of all jobs.

A minority (19.5%) of the secondary sector employees worked in very small businesses.

In the tertiary sector; 70 or 27.6% were in wholesale or retail sales or the repair of motor vehicles, 24 or 9.4% were in the movement and storage of goods, 32 or 12.6% were in a hotel or restaurant, 5 or 2.0% were the insurance or financial industry, 16 or 6.3% were technical professionals or scientists, 35 or 13.8% were in education and 48 or 18.9% were in health care.

[14] From the 2000 census[update], 859 or 38.7% were Roman Catholic, while 802 or 36.1% belonged to the Swiss Reformed Church.

In the Vaud cantonal school system, two years of non-obligatory pre-school are provided by the political districts.

The canton's primary school program requires students to attend for four years.

In 2009 the Musée Sherlock Holmes was visited by 1,359 visitors (the average in previous years was 1,373).

In 2014 the crime rate, of the over 200 crimes listed in the Swiss Criminal Code (running from murder, robbery and assault to accepting bribes and election fraud), in Lucens was 58.8 per thousand residents.

The rate of violations of immigration, visa and work permit laws was 1.3 per thousand residents.