X-ray Laboratory Safety

Additional Local Rules
System of Work in Powder X-ray Laboratory 313

Last updated 7 November 2008

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Departmental Health and Safety (Chemistry UCL)


  1. Current Status
  2. Critical Examination
  3. New User Training
  4. X-ray Safety Monitoring
  5. Procedure for Open Beam Work within Controlled Radiation Area 312
  6. Low Oxygen Alarm Testing

1. Current Status

The IMG X-ray laboratory currently has two X-ray generators, one supplied by Siemens, now Bruker, for a Siemens D500 Bragg-Brentano diffractometer, and one made by Spellman and supplied by Stoe for a Stoe refurbished STADI-P powder diffractometer. Both systems are equipped with non-walk-in safety radiation enclosures. The latter are fully interlocked. The opening of the shutter is only by positive user action and with the shielding correctly in place (i.e. doors closed). Accidental opening of the safety enclosures with the beam open results in a trip of the beam shutter which remains closed even when the enclosure doors are re-closed.

2. Critical Examination

  1. Siemens D500
  2. Stoe STADIP

3. New User Training

All new users of the X-ray powder diffractometers must be trained in person either by the laboratory research manager, Martin Vickers, or by the senior academic, Jeremy Karl Cockcroft, responsible for the PXRD laboratory.

Users will be given instruction on:

In addition, users are made aware of the local rules concerning X-ray laboratory safety.

Everyday users of the equipment must not touch or adjust any part of the diffractometer concerned with alignment. If misalignment is suspected (e.g. after a long power shutdown), users must contact Martin Vickers or Jeremy Karl Cockcroft as soon as possible. In the event of warning bulbs not functioing correctly, one of the above persons must be informed so that dead bulbs can be replaced.

In the event of non-ambient sample environments being used, these will be setup by Martin Vickers or Jeremy Karl Cockcroft and specific training will be given for their use.

4. Regular X-ray Safety Monitoring

The following procedures must be carried out during the year (typically every 2-6 months depending on active use of the equipment). Tests must be carried out with a calibrated and functioning Geiger X-ray monitor, and the results are to be recorded in the hardback IMG laboratory safety book. Before the specific tests below are started, the warning light bulbs of the X-ray generators should be checked for correct functioning. (The X-ray generators will normally function with one dead bulb, but not with two dead bulbs. Note that the Spellman generator has an additional single bulb in the safety box behind the generator.)

5. Procedure for Open Beam Work within Controlled Radiation Area 312

From time to time it may be necessary to bypass the security interlocks on the Stoe system so as to re-align the diffractometer. (In extremely rare circumstances, open beam diagnostic work may be required for the Siemens system. In this case, a similar procedure to that described below should be adopted). This requires access to the bypass key that is kept in the key-cupboard. During open beam work, the following procedures must be followed:

6.Low Oxygen Alarm Testing

The following procedures must be carried out on an ad-hoc basis (depending on active use of both liquid nitrogen and liquid helium dewars). The test may be carried out by blowing an inert gas over the oxygen sensors: in practice, expired air blown through a rubber tube and directed at the sensor should be sufficient to trigger the alarm system.

The alarm system consists of the main control box in 312 plus two oxygen level sensors, one positioned near floor level and the other positioned near ceiling level, plus 4 alarm units. Normal reading for oxygen level is 20.9% (though in practice the sensors may display a reading in the range 20.8% to 21.0% due to drift in the calibration as a function of time). If the level of oxygen drops to an unsafe level (< 18.5%) for either sensor, the audio-visual alarm box in 312 will produce a red flashing light and siren-style noise.

When the oxygen level returns to safe (i.e. both sensors reading > 18.5%), the alarms will automatically switch off. The current system does not record that the alarms have been triggered: it simply shows whether the oxygen level in the room is safe or unsafe.

Industrial Materials Group