CRISP Risk Assessment - ISIS

Hazard Assessment for the CRISP Reflectometer in ISIS at RAL
The CRISP neutron reflectometer is an instrument on the ISIS pulsed neutron source at RAL.
The instrument uses a beam of thermal/cold neutrons to probe, by specular reflection the
nature of surfaces and interfaces of thin films.
The reflectometer is located on the N4 beamline and views the liquid hydrogen moderator.
The primary hazard is the neutron beam, which has a maximum dimension of 40x10 mm, and
a thermal/cold flux of

efore the solenoid is energised. Once the “green box” is activated and key released, an
integral switch within the box senses the key has been removed and prevents the beam shutter
from being opened. Any attempt to open the beam shutter before the interlocks are made, or
any malfunction causes the accelerator to trip and therefore remove the source of the
radiation. A radiation monitor in the chopper enclosure provides an additional interlock.
Blue fluorescent lamps are visible in the experimental area when radiation is present. Lamps
indicating the interlock status are also visible from the access gate. Two emergency “beamoff”
buttons are provided in the experimental enclosure, which trips the accelerator when
activated. The access door can only be closed when the 'search' button has been pushed.
Permit to work
For the removable shielding blocks of the chopper enclosure the crane lifting points are
“locked off” by keys held in the MCR key-press and interlocked with a Fortress Interlock
key. Access can only be gained using a “permit to work”. This requires the shutter to be
locked off by the Duty Officer in the closed position, and can only be released when the
shielding has been replaced, locks replaced and an inspection carried out.
Enclosed Experimental Area
‘The experimental enclosure is sealed and air conditioned. The access doors can be opened
from within the enclosure, and will cause the accelerator to trip if the interlocks are enabled.
The air-conditioning has a continual supply of filtered air, the status of which is displayed: an
oxygen monitor is installed within the enclosure with the alarm located outside the access
door.
Alignment Laser
Within the experimental enclosure there is a 3mW solid state laser (670 nm wavelength) for
sample alignment. The installation is in accordance with current regulations for Class IIIa
lasers. The laser power supply is connected through a “Warning Laser On” light at the
enclosure entrance, and the appropriate warning notices are displayed.
Magnet and Cryostat
Two electromagnets are currently available on CRISP to provide magnetic fields in the range
0

low risk of hazards. Contact with cryofluids (liquid helium and nitrogen) represents a risk of
burns to exposed skin. Only experienced technicians and CRISP instrument staff fill the
cryostat with cryofluids.
DG Bucknall
12 February 1997
Updated: S. Langridge January 2001