Page 105 - ILL Annual Report 2019

THE ILL’sHigh-Flux Reactor (HFR) produces the most intense
neutron flux in the world: 1.5 x 1015 neutrons per second per cm2, with a thermal power of 58.3 MW.
It normally operates four reactor cycles per year. At the end of each cycle there is a shutdown period, during which the fuel element is changed and a number of checks are carried out. Occasional longer shutdowns are scheduled to allow for equipment maintenance.
At maximum power, the reactor's fuel element can provide 46 days of operation per cycle. For almost the last ten years, our ‘contract’ with our scientific users
has been to provide 200 days of operation per year (excluding maintenance and upgrade work). At nominal power this allows for 4.5 cycles per year.
For obvious practical reasons this number of annual cycles is not ideal; for the Reactor Division it involves the same amount of work as having five operating cycles, since the tests to be carried out and fuel loading operations are the same before every start- up irrespective of the length of the cycle. As the performance of the instruments has generally been increased over the years thanks to regular upgrade programmes, we have recently decided to provide the 200 days of operation over four 50-day cycles at slightly lower power.
Following the nuclear disaster at Fukushima in 2011, the French nuclear safety authority (ASN) ordered additional safety assessments to be carried out on all French basic nuclear installations (INBs), including the ILL. The Post-Fukushima programme has now ended. The safety of the reactor is guaranteed, even in the event of an extreme earthquake-and-flood combination following the rupture of the dams upstream, well beyond previous dimensioning standards.
The ASN has also asked the ILL to reorganise our working methods to make them better and more secure, by implementing an Integrated Management System (SMI) (INB Decree of 2012) and incorporating it into the ILL’s operating procedures. The ASN decisions
are extremely demanding and involve a lot of work. However, such work is essential and remains a top priority for the ILL.
REACTOR OPERATION
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