C. RISK ASSESSMENT FOR WORKING WITH X-RAYS IN THE X-RAY CRYSTALLOGRAPHY SUITE, ROOM 5.20, FLOWERS BUILDING

Transcription

1 C. RISK ASSESSMENT FOR WORKING WITH X-RAYS IN THE X-RAY CRYSTALLOGRAPHY SUITE, ROOM 5.20, FLOWERS BUILDING DEPARTMENT: Center for Structural Biology, Flowers Building, Biological Sciences. ROOM/LAB: 5.20 SUPERVISOR: Paul Freemont MANAGER: Liz Carpenter 1. Activity: This document covers the risks associated with working with X-rays in the X-ray crystallography facility, room 5.20, Flowers Building, Imperial College. 2. The X-ray facility The X-ray facility consists of three X-ray generators from Rigaku-MSC, three X-stream crystal freezing sets and three image plates from MAR. The equipment is housed in three separate experimental areas (hutches) within room The X-ray shutters are interlocked, so that when the users are working near the X-ray equipment, the X-ray shutters are closed and no X-rays are emitted from the system. Only by closing the lead impregnated plastic doors and activating the interlock switches can the shutters be opened to allow X-ray emission in the experimental area. The system is designed to prevent anyone exposing themselves to X-rays. 3. Properties of X-rays and hazards associated with use of X-rays in the facility: X-rays are electro-magnetic waves We use copper k-alpha radiation of wavelength Å. We use a single well-collimated beam of approximately 200 um x 200 um. If these X-rays hit a part of the body they would be absorbed by the first few millimeters of the body This causes burns in the short term There is a risk of cancer in the long term These X-rays can be detected using a Geiger counter. 4. Risk assessment and control measures in place: The table below shows the risks to anyone who may be involved in the use of X-rays in room 5.20 and those who may have access to the facility. Last revised on 31 st of March,

2 The risks to the general public are minimized by preventing access to the laboratories where the work is carried out. Swipe cards are required for access to both the building and the X-ray laboratory. Activity: Mounting crystals, testing crystals and collecting data using the X-ray generators in room This facility is used for collecting X-ray diffraction data from crystals of macromolecules. Generally these crystals are kept at 100 kelvin with an X-stream cooling system. Crystals are mounted on the X-ray camera in fibre loops in a stream of N 2 gas at 100 K. Alternatively crystals are mounted in glass or quartz capillaries and data is collected at room temperature. Users leave the experimental area, close the doors and activate the interlock system before the crystals can be exposed to X-rays. Risk: exposure to X-rays leading to burns and possible carcinogenic effects. Risk to: Direct users Control measures: Summary The risk of exposure to X-rays are minimized by preventing anyone from having access to the X-ray equipment when all the shutters are open. No-one should ever be in the experimental area when X-rays are being emitted. The equipment All this equipment is new: the oldest system is 3 years old, the other systems are less than 2 years old. All equipment is housed inside an interlocked experimental area (hutch). X-rays can not penetrate the glass doors or the brick walls between the hutches. The X-ray beam is directed away from the area where the users sit when data is being collected. The generators have a number of safety features: The generation of X-rays is disabled when the visual indicator lights are not working. The shutters are disabled with the shutter open warning lamps are not working. X-ray production is disabled if a shutter fault occurs (sticks open or is forced open). The main circuit breaker is disabled, removing all power to the generator, if any access panels are removed. There is an emergency panic button on the front of the generators which turns the generator off. Last revised on 31 st of March,

3 Interlocks: When users are working with crystals near the X-ray generator there are always two shutters closed on the generators. In order to obtain an X- ray beam the users must leave the experimental area, close the glass doors, activate the hutch interlock by pressing a button and turning a key or flicking a switch. The interlock will not work unless the door is properly closed. The final shutter is opened from the computer screen outside the hutch. If the door to the hutch is opened at any time when the shutters are open, the shutter will close automatically. Interlock override There are override keys for the interlock. These are kept is in the possession of the X-ray technician and the facility manager. They are not left in room This allows the interlock system to be inactivated when maintenance work requires the X-ray technician to work in the hutch with the beam on. Only the trained technician, Ian Coole, can perform this task, no user has access to the key. Training All users will be trained in the use of the X-ray equipment either by their supervisors or by the X-ray laboratory facility manager, Liz Carpenter. The users are also required to read the local working rules and the facility risk assessment. All users are required to complete the Registration form for Users of the X-ray Crystallography Facility. This consists of two parts, the college registration form working with ionizing radiation - new users registration form and Training record for users of the X-ray facility, room 5.20, Flowers Building. Prior to becoming a registered user all users must complete these records to indicate that they have read the local rules and risk assessment. They must also sign that they have received training in the use of the facility and obtain a signature from their trainer. User tests for X-ray leaks A Geiger counter is available in the X-ray laboratory and users are trained in its use. They are required to scan the area around the crystal mounting position prior to starting work and when they finish. The maximum reading is to be recorded at the start of each experiment. Should any part of the generator, collimator or shielding be dislodged or knocked during an experiment the users are told to stop work immediately and see either Liz Carpenter or Ian Coole to discuss any possible problems with the equipment. Signs to provide suitable information There are signs on the door of the X-ray facility indicating that it is a restricted area where X-rays are produced. Last revised on 31 st of March,

4 Safety check by the manufacturers: All three generators were subject to a safety assessment by the manufacturers, Rigaku MSC, on the 29 th of August, All three were certified as safe by the company on that date. We have arranged a yearly maintenance contract which includes a yearly visit to our site in which we include a safety check of the equipment by the manufacturer to ensure that no problems have arisen in a given year. These safety checks will be performed each year. Safety check by college safety department: The Safety department radiation officer, Mark Ramsey will be carrying out unannounced safety checks of the facility at intervals. Maintenance: General maintenance of the X-ray equipment is performed by our specialist X-ray technician, Ian Coole. We will have regular maintenance visits from Rigaku MSC to ensure that the equipment is properly checked. We have a service contact arranged from March 2003 to March, Other workers in the area. Cleaning staff Room 5.20 is only accessible with a swipe card and only users of the X- ray facility have access to the room. If anyone did enter the room by mistake they would not be exposed to X-rays since the interlock system would protect them. Cleaning staff can not expose themselves to X-rays since the interlock system would switch off the X-ray beam as soon as they attempted to enter the experimental hutch area. Cleaning staff are currently only cleaning the outer area, not the hutch areas, where X-rays are generated. Cleaning of the hutches is done by arrangement between the cleaning staff and the facility manager only when the X-ray equipment is off and the manager or technician can be present to supervise the work. The general public Members of the general public would not have access to the X-ray facility since there is swipe card access for both the Flowers Building and room If someone unauthorized did enter room 5.20 they would be protected by the interlock system. Maintenance staff Members of the maintenance staff can not enter room 5.20 without a prior arrangement with Anna McDadd, (the Flowers Building Supervisor). She would arrange access with the manager and/or facility technician. If it was necessary for staff to enter the experimental hutch area, where X-rays could be generated, then the interlock system would prevent exposure of maintenance staff to X-rays. If maintenance work such as changing the air filters above the X-ray equipment is necessary then X-ray generation will be turned off. If necessary the X-ray technician or facility manager will be present to Last revised on 31 st of March,

5 ensure the safety of the equipment. Signs on the facility door indicate the possible presence of X-rays. Activity: Maintenance of the X-ray equipment The X-ray equipment requires regular maintenance which is carried out by the X-ray technician, Ian Coole or occasionally by the facility manager, Liz Carpenter. Operations include: 1. Changing the filaments, oil filters, fan belts, on the X-ray generators 2. Changing the erase lamps on the MAR detectors 3. Adjusting the osmic mirrors to optimize the beam. Only the last of these operations requires the override switch to be used, in the first two processes the override is not needed. In the third operation the override switch is used, but the final shutter is not opened, so the user can not be exposed to X-rays. No operation is performed with the final shutter open. It is only on rare occasions that the interlock is overridden. The override keys are kept by the manager and the technician. They are not given to users. All users, workers in the vicinity and members of the public. The Facility technician, Ian Coole. No-one should be working in the X-ray facility when the override system is activated. The facility technician and manager are the only people with access to the override key. Ian is a highly experienced X-ray facility technician. He knows the risks of working with the equipment when the beam is on and never does so. He wears a radiation dosage film badge when working with the X-ray equipment. This badge is checked regularly to ensure that he does not exceed the maximum allowed dose. The area where the technician is working is checked with the Geiger counter before and after the work to ensure that are not X-ray leaks. The technician does not perform tasks which involve him being in the hutch with the interlock override activated and all the shutters open. Conclusions: 1. There should be no risk of anyone exposing themselves to X-rays in the facility. 2. We do not see a need for general users to have radiation dosage badges, since the chances of exposure to X-rays are very remote. 3. Users will be required to attend specially designed radiation safety instruction sessions with their supervisors or the facility manager. 4. The college radiation safety course will also be drawn to their attention though attendance on this course is not mandatory for access to the facility. Last revised on 31 st of March,

6 Requirements for the future: 1. Ensure the maintenance contract is in place 2. Arrange for the maintenance visit These tasks to be completed by Liz Carpenter on her return, in October, People with responsibility for the X-ray facility, safety and the Flowers building: Person responsible Their role Extn number Paul Freemont Supervisor/Head of laboratory p.freemont Stephen Curry Radiation Supervisor for Biolgical Sciences s.curry Mark Ramsay Radiation Supervisor m.ramsay Liz Carpenter X-ray facility manager liz.carpenter Ian Coole X-ray facility technician i.coole Colin Gleeson Flowers Building Safety Officer c.gleeson Anna McDadd Flowers Building Supervisor a.mcdadd Risk assessment review record: Date: Reviewed by: Date reviewed: Signature: October, 2003 April, 2004 October, 2004 April, 2005 October, 2005 April, 2006 Last revised on 31 st of March,