Radiation Safety Manual - Chapter 06: Radiation and Contamination Surveys

Title

Radiation Safety Manual - Chapter 06: Radiation and Contamination Surveys

Introduction

Prevention of the spread of contamination and excessive radiation exposure is the responsibility of the Authorized User. The Authorized User is also responsible for providing radiation detection equipment to monitor removable contamination and external radiation exposure levels as appropriate. Radiation detection devices, such as liquid scintillation counters, gamma counters, and portable survey instruments, must be available.

Table of Contents

1. Laboratory Surveys
   1. Contamination Survey Procedure
2. EHS Surveys
3. Authorized User Surveys
4. Instrument Surveys
5. Wipe Tests
6. Action Levels
   1. External Radiation
   2. Contamination
7. Training
8. Survey Instrument Calibration
9. Removal of Laboratory Equipment
10. Vacating Laboratory Spaces
    1. Procedures for Vacating/Moving Laboratory Space

Laboratory Surveys

“Survey” means an evaluation of the radiation hazards incident to the use, release, disposal and presence of radioactive materials and other sources under a specific Authorized User. A survey should include measurements of external radiation levels near sources in use, storage, waste containers, etc. and of removable contamination by wipe testing (refer to Contamination Survey Procedure). Both restricted (areas posted with radiation warning signs and labels) and adjacent unrestricted areas should be included. Surveys should also include an examination of the presence and condition of warning signs, instructions and other necessary postings and a thorough review of the records-keeping system.

During the monthly survey, records-keeping systems and the Radiation Safety Notebook should be reviewed for completeness and orderliness. Waste storage, records and security should be examined also during the monthly survey.

Contamination Survey Procedure

A series of wipe tests must be taken in all areas where activity is handled in unsealed form on a routine basis. The location of wipe tests should be indicated on the survey form and should be chosen for maximum probability of contamination, e.g. areas where individual doses are drawn up, incoming packages received, frequent pipetting carried out.

Floors, particularly adjacent to doorways, lead syringe shields, and door and drawer handles should also be wipe tested frequently. Care should be taken that cross contamination does not occur.

A gamma-scintillation counter (example: NaI well counter), should be used for pure gamma emitters. Make sure that the analyzer threshold is set below the lowest gamma energy used in the lab (usually I-125). Low energy beta emitters will require liquid scintillation counting for wipe assay.

Measure the background count rate under the same counting conditions used with the wipes and record. An individual wipe test should routinely cover approximately 100 cm². Ideally, any contamination more than a few DPM above background should be cleaned up; however, a more usual level at which cleanup is initiated is about 200 DPM (100 CPM).

EHS Surveys

EHS personnel periodically inspect the laboratories of Authorized Users to monitor the in-lab radiation safety program. Radiation exposure rates and removable contamination levels are measured and records-keeping systems are reviewed during the surveys. The frequency of surveys is determined by the quantity of radioactive materials used, results of previous surveys, and general compliance with State and University safety and health regulations and policies. Although the EHS inspections fulfill a need for supervisory overview, they do not provide adequate day-to-day information regarding the effectiveness of radiation control procedures used in the laboratory. Therefore, laboratory personnel must routinely monitor their laboratories when using radiation sources.

Authorized User Surveys

Each Authorized User is required to conduct formal, documented surveys on a regular basis in every authorized radiation use space. The Radiation Safety Office establishes this survey schedule during application review. The typical schedule requires the survey to be performed within each calendar month. The schedule is subject to change through the Radiation Safety Office in accordance with the frequency of source use, potential for exposure and the established safety record.

When higher energy beta emitters, such as P-32, or gamma emitters, such as I-125, Na-22, etc. are used in the laboratory, the monthly Authorized User survey must consist of a wipe test and instrument survey using a portable, hand-held survey meter. The instrument make, model number, serial number, calibration date, and readings must be recorded on the written survey report. Instrument surveys are specified in the radiation source authorization, if required. When lower energy beta emitters; such as H-3, C-14, or S-35, or small quantities of gamma emitters contained in commercial test kits, are used in the laboratory, only wipe test surveys are required.

During the monthly Authorized User survey, records-keeping systems and the Radiation Safety Notebook should be evaluated for completeness and orderliness. Waste storage, records, security, and the overall laboratory radiation safety program should also be reviewed. If no radioactive material has been used during a month, a statement of that fact may be entered into the Radiation Safety records in lieu of a recorded survey. However, a record of the survey performed after the last use must be on file, showing that all radiation and contamination levels are within the specified guideline limits. For Authorized Users having more than one room authorized on their radiation us license, a statement of "No Use" may be entered for the individual rooms where radioactive materials was neither used nor stored (including waste) for the month. As such, a survey is required only in those rooms where use or storage occurred during the calendar month. The Radiation Safety Office may, according to particular conditions including quantities or types of materials and an Authorized User's safety record, set radiation safety survey schedules specifically designed for named laboratories or Authorized Users.

Instrument Surveys

The routine use of radiation survey instruments during the course of any work utilizing gamma or higher energy beta emitters (other than H-3, C-14, S-35, etc.) is required. After each use of stock solutions:

• Monitor hands, arms, front of lab coat and other potentially contaminated areas.
• Monitor bench tops, floor areas, equipment, etc.
• Monitor hands and clothing before leaving the laboratory.

Do not use a survey meter that has not been calibrated within the past year for any purpose. Never use a survey meter that indicates "low batteries". Any meter that is not operating properly or is out of calibration must be tagged or labeled as "Out-Of-Service". Low batteries should be replaced at once. If an instrument is put in storage, the batteries should be removed. Old or spent batteries are prone to leakage and can ruin an instrument.

Wipe Tests

Wipe tests are performed by wiping a filter paper disk, Q-tip, etc., across the areas of interest and then determining the activity in a counter calibrated for the suspected radionuclide. Wipe tests are more sensitive than instrument surveys and should especially be used when instrument surveys indicate possible contamination. They are the only practical method of monitoring weakly penetrating beta emitters, such as H-3, C-14, S-35 and are to be substituted for instrument surveys for such emitters. The wipe test method must be used for all surveys conducted for identifying and/or documenting removable contamination levels.

When radioactive contamination is found above the action levels, clean and decontaminate the area. Re-survey with wipe tests and record the results to document adequate cleanup.

Action Levels

External Radiation

Radiation levels must be kept to less than 2 mrem/hr at 30 cm (12 in) from the source surface and to levels as low as reasonably achievable.

Areas in which the radiation exposure level exceeds 5 mrem/hr must be designated as a "Radiation Area" and posted with an appropriate sign (available from EHS). When such levels are expected, the RSO will indicate specific procedures to be followed when the "authorization" to use radioactive materials is issued. When such conditions arise that are not covered by the authorization, the RSO must be contacted immediately.

Contamination

EHS records removable contamination levels in terms of disintegrations per minute (DPM) per 100 square centimeters (standard areas to be covered by a "wipe"). Wipe test survey results by Authorized Users must also be recorded in DPM. Counting efficiencies used to convert from CPM to DPM may be stated in the Authorized User's records in lieu of converting to DPM. Typical liquid scintillation counting efficiencies are 20 percent for H-3 and 50 percent for other radionuclides. Laboratories may use the same counting efficiencies for wipes or use their own established efficiencies. Actions to be taken as a function of contamination level are:

Training

The specifics of how to perform contamination and radiation surveys will be covered in the radiation safety training sessions which all laboratory personnel and new Authorized Users are required to attend prior to use with radioactive materials. During the first three months following authorization of a new User, EHS personnel will assist as requested in establishing routine surveys, which are required by conditions of the User's Authorization.

Survey Instrument Calibration

Survey instruments must be calibrated annually. The calibrations will be performed by the Radiation Safety Office, without charge. The Radiation Safety Office must be informed whenever a new instrument is purchased, after significant repair or other calibration has been done.

Removal of Laboratory Equipment

Any equipment in the laboratory which could have been contaminated with radioactive material must be surveyed before removal to another laboratory, transfer to a repair shop, or transfer to Surplus Property. Before the equipment is transferred and following a satisfactory survey, all warning signs and stickers must be removed. A Safety Clearance Form, Appendix F (see attached document, below), must also be completed. This form should be provided to the appropriate personnel to designate that the equipment is considered safe for any use.

Vacating Laboratory Spaces

EHS must be informed of all changes in authorized laboratory spaces, including transfers or departures from the University and laboratory relocations. Written notification to EHS is required prior to vacating a lab or moving into different labs (refer to Procedure for Vacating/Moving Lab Space). The Authorized User is responsible for surveying all spaces and equipment and proper removal of all radioactive waste and radioactive sources prior to the changes. Upon notification, via the filing of a Safety Clearance Form, EHS will complete a final clearance survey of the authorized spaces.

Procedures for Vacating/Moving Laboratory Space

1. Written notification to the UNC Department of Environment, Health & Safety is required prior to vacating a lab or moving into a different lab. Prior to moving into a new lab, the room/s must be authorized and posted for radiation use.
2. When vacating a lab, remove all sources of radiation from the lab space, source vials, aliquots of radioactive material, experiments containing radioactive material and radiation waste.
3. Decontaminate all areas where radioactive material was used, and decontaminate all equipment (refrigerators, freezers, incubators, centrifuges, microfuges, etc.) that contained radioactive material.
4. Perform a radiation survey of the whole lab including all equipment that may have contained radioactive material (Geiger counter survey and wipe test survey).
5. The Safety Clearance Form (Appendix F) is to be used for rooms/equipment that contained radioactive material, have been decontaminated and surveyed, and are considered safe for any use.
6. After survey of equipment and if equipment is to be moved, transferred, surplused or remain in the vacated space, remove the radiation labels on the equipment, and attach a Safety Clearance Form (Appendix F) to the equipment. This form verifies that the equipment is considered safe for any use. Contact EHS for new radiation stickers as needed after moving/repairing equipment. Do not allow maintenance staff or the moving crew to repair/move/transfer equipment with radiation labels affixed to it.
7. Notify Environment, Health & Safety via the Safety Clearance Form (Appendix F) that lab space is ready for a final clearance survey by one of our EHS Safety Officers.
8. Never remove the room sign. Environment, Health & Safety will remove the room sign after an EHS Safety Officer has completed the final clearance survey of the vacated lab space.
9. Call EHS for questions at 919-962-5507.

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