X-Ray Facility Safety Review
The following information is an application of basic radiation safety to the situations encountered in our laboratories. A familiarity with the fundamental radiation concepts presented in the University radiation safety training films is presupposed.
Sources of Radiation
In our facilities there are two types of radiation:
- machine-produced X-ray radiation in Rooms 8 and 22 Shepherd Labs
- X-rays from a radioactive material: Fe55 in Room 8 Shepherd Labs
General Philosophy of Acceptable Radiation Exposure
The equipment in our laboratories is equipped with safety interlocks in order to eliminate accidental exposure. Our goal is that one should receive no exposure during routine operation of the equipment. Even during alignment procedures exposure is to be avoided.
Principles of Radiation Exposure Control
There are three aspects of exposure control important in the lab:
- Equipment is periodically monitored using a hand-held Geiger counter radiation monitor.
- Sufficient shielding is provided so that no exposure occurs during general usage.
- During alignment additional shielding is used, including lead aprons and distance (remote tools) to avoid exposure. Placing any part of the body in the pathway of the X-ray beam is to be avoided at all times.
Individuals using the x-ray equipment are monitored to record accidental exposure. Dosimetry is not a preventative measure, but allows exposure to be quantified. Dose monitoring will be done using a TLD ring obtained from the university's Environmental Health and Safety Radiation Protection office. Rings are stored in a cabinet in room 8. If you have your own ring, wear only the ring assigned to you. If you are using one of the laboratory's visitor rings wear the same ring every time, if possible.
- Record the ring number in the comment section of the computer log.
- Wear the ring at all times while in the lab.
- Wear the ring with the TLD turned towards the source of the x-rays.
- Do not intentionally expose the personnel-monitoring device to radiation, contaminate it with radioisotopes, or damage it in any way.
- When not in use, the ring should be stored in the storage cabinet in room 8. Do not take it home to avoid loss or exposure to stray radiation. If you accidentally remove the ring from the lab, make a notation in the comments section of the computer log.
- The Radiation Protection Program maintains a permanent record of the radiation dose accumulated by each individual monitored at the University. An individual may request information on his or her radiation dose history from the Radiation Protection Program at any time.
- Rings are exchanged by the X-ray Scattering Lab staff and the Environmental Health and Safety Department four times a year for analysis.
- Quarterly dosimetry reports are kept on permanent file by the facility director. Individuals may see their reports at any time. The individual will be notified if any significant exposure is detected.
- Visitors to the lab must be monitored using visitor rings. The ring number and name of the individual using the ring must be recorded in the comment section of the computer log.
Legally Permissible Dose Limits
While our goal is to minimize exposure, federal and state regulators have established radiation dose limits. If these limits are exceeded, the individual will not be allowed to perform any more experiments.
- The limits for people who are not pregnant and who are exposed in the course of their occupation are:
- whole body dose - 1.25 rem/qtr (100 mrem/week)
- extremity dose (hands, feet) - 18.75 rem/qtr (1.45 rem/week)
- skin of whole body - 7.5 rem/qtr (575 mrem/week) - 30 rem/year
- A recommended maximum dose level for pregnant women is 100 mrem/9 months gestation. Exposure during the first trimester is the most hazardous. Generally, pregnant women should not be assigned to a radiation use area during pregnancy unless exposures potential is demonstrated to be below 100 mrem/9 mo.
There are special requirements for pregnant women. If you are pregnant, you have the option of notifying Linda Sauer of your condition (in writing) and she will initiate the special training and radiation monitoring.
- The radiation protection guide's limit for an individual in the general public (e.g. a visitor) is 100 mrem/year.
Access to the lab is limited to authorized individuals. Users are required to complete the safety training including viewing of the video "The Double-Edged Sword"
Also required is a review of our laboratory's specific policies as outlined in this document. A record of the training sessions will be kept on file.
Equipment-Specific Safety Aspects
Each x-ray generator has an "x-ray on" light that is hard-wired into the instrument's safety circuit. Check to see if the "x-ray on" light is lit before logging your time on the computer. Check the box on the log sheet indicating that the x-ray on safety feature is working.
All the X-ray scattering instruments have ‘door-shutter interlock’. The shutter will not open if the doors are open. Only when the doors are locked, the shutter will open. If the door is opened accidentally when the shutter is open, either the shutter will close or X-ray will shut off.
- Do as much sample preparation as possible before entering the lab. There is no hood, so use solvents sparingly.
- Samples may remain in the lab only while you are present. Please take them with you when you leave. Don't throw chemicals in the trash!
- Clean the sample holders (and mortar and pestle if you used them) and the sample preparation area before you leave.
- If you are working with anything particularly hazardous, let the lab manager and others working in the lab know.
Emergency Telephone Numbers
In case of an emergency, the following numbers are provided:
Environmental Health and Safety Radiation Protection: 612-626-6002
After Hours: 911
Tell them you are in room 8 or 22, Shepherd Labs, phone number 612-626-0776 and give them a brief description of the incident.
General Laboratory Safety
- No food or beverages in the facility.
- Review the laboratory's Chemical Hygiene Plan.
- Gas cylinders must be fastened securely.
- Eye washes are located in rooms 8 and 22b.
- Fire extinguishers are located in each room.
The facility director is responsible for enforcing the laboratory safety policy. Safety policy infractions will result in the individual being asked to leave the lab for a period of not less than one day. Grievous negligence could lead to permanent removal from the lab.