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When working with radioactive materials, use an appropriate radiation detection instrument repeatedly during the work to monitor the work areas, equipment, and yourself. Monitoring during and after work will help prevent the spread of contamination. Table 12.2.1 indicates which instrument to use for each type of monitoring that might be performed.

12.1 Surveys

Surveys are required to be performed (but not documented) during work and after use of radioactive materials. In addition, the laboratories are responsible for documenting a survey at least monthly in all spaces listed on the PI's RMUA. The lab must keep survey records for review for three years. The survey frequency may be increased if the RSO deems that contamination has increased to levels that could pose an exposure problem or cause regulatory concern.

For labs in which tritium is used, a wipe survey analyzed by liquid scintillation is required to satisfy the survey requirements. Tritium is not detectable with standard portable radiation survey instruments.

Labs using isotopes other than tritium must complete a wipe survey or an instrument survey. (See Section 12.2.6 and Section 12.2.7 for procedures for doing wipe and instrument surveys)

If a laboratory has no radioactive material use in a given month, no surveys need be documented for that month. In lieu of the monthly survey, the lab must note on the survey form or log that "No radioactive material was used during [month]" or words to that effect.

EH&S performs confirmation surveys in all labs on a quarterly basis as part of the lab audit program. EH&S also does monthly surveys in all common areas. Common areas are areas that:

  1. Are not lab spaces;
  2. Have more than one PI using the space but no main user;
  3. Have radioactive material use that could result in contamination;
  4. Have open access and may be used by any researcher at Fred Hutch; and
  5. Are listed on any RMUA as active labs.

When removing a lab from radioactive service, a complete survey of the lab by the lab staff is required, and a follow-up survey must be done by EH&S. See Section 12.2.11: Lab Closeout and Decommissioning Surveys.

12.2 Performing and Recording Surveys

Survey types are defined as follows:

  1. Instrument Survey: Used to locate fixed and removable contamination on surfaces, equipment, staff, and clothing. (See Section 15.5.1, Contaminated Work Areas and Section 12.2.6, Portable Detector Survey Procedures.)
  2. Wipe Survey: Used to locate and quantify removable contamination on surfaces, equipment, staff, and clothing. (See Section 15.5.1, Contaminated Work Areas and Section 12.2.7, Wipe Survey Procedures.)
  3. Exposure Survey: Used to measure the dose rate in an area, usually in mR/hr. (See Section 12.2.12, Exposure Survey.)
  4. Air Concentration Survey: Used to measure the airborne concentration of a radioactive material. (See Section 12.2.15, Air Concentration Survey for procedures.)

Table 12.2.1: Appropriate Survey Instrumentation By Radionuclide

Radionuclide

Type of Survey

Instrument Type and Probe

3H

Wipe only

Liquid scintillation counter (LSC)

14C, 32P, 33P, 35S, other beta emitters

Wipe

Liquid scintillation counter (LSC)

125I, 51Cr, 131I, other gamma emitters

Wipe

Gamma counter or liquid scintillation counter (LSC)

14C*, 32P, 33P, 35S, 131I, 90Y, other medium to high energy beta emitters

Instrument

Portable detector with thin window GM pancake probe preferred, also useable is a EWGM.

125I, low energy gamma emitters

Instrument

Portable detector with thin NaI probe

51Cr, 131I, medium energy gamma and high energy beta emitters

Instrument

Portable detector with thick NaI probe preferred, also useable is a EWGM

High energy gamma emitters

Exposure

Ion chamber, also useable is the SWGM

*C-14 detection via instrument is allowed with RSO permission and reduced detection level (e.g., 50 cpm over background). LSC is the preferred method for surveying for C-14.

12.2.2 Common Probes

  1. GM Pancake Probe: Gas-filled Geiger-Mueller probe with a thin entrance window with a round and flat shape;
  2. NaI Probe: Solid sodium iodide crystal used in probe. NaI crystal may be thin (1mm) for low energy x-rays and gammas or thick (1'x1') for higher energy gammas;
  3. End-window Geiger-Mueller (EWGM) probe: Cylindrical shape; and
  4. Side-window Geiger-Mueller (SWGM) probe: Cylindrical shape. Preferred as an energy-compensated GM detector.

12.2.3 Common Stationary Analyzers

  1. Liquid scintillation counter (LSC): A large stationary counter in which radioactive material is placed directly into a fluid or fluor for measurement. Can detect all research nuclides with good efficiency.
  2. Gamma counter: A large stationary counter containing a NaI well crystal. Used to analyze gamma samples.

12.2.4 Common Portable Detectors

  1. Count Rate Meter: Handheld device to which a probe is attached. Has a read out in counts per minute (CPM).
  2. Ion Chamber: Exposure rate meter, reads out in mR/hr. Often has beta slide shield over chamber. The RSO can recommend specific meters and manufacturers for your laboratories' needs.

12.2.5 About Portable Radiation Detectors

Various companies supply the Center with radiation detection instruments. Laboratories are responsible for purchasing their own instruments with EH&S providing calibration and some repair services. For information about a specific company, contact either EH&S or Purchasing. When ordering a new instrument, please contact EH&S so the detector can be added to the annual calibration tracking database. A portable radiation detector is usually made of two parts, the instrument body and the probe. The instrument body contains the electronics, batteries, on-off switch, and readout (preferably in counts per minute or cpm). Use Table 12.2.1 to identify which instrument and probe to use.

12.2.6 Portable Detector Survey Procedures

  1. Use an appropriate detector with the correct probe as specified in Table 12.2.1. The instrument should have an audible signal and readout in cpm.
  2. The instrument should be checked for operation, calibration and battery before the survey.
  3. A reading should be taken away from the area to be scanned to get a representative background count.
  4. With the instrument on the lowest scale, slowly scan items and areas with the probe about 1/2 inch away from surfaces.
  5. Probe should scan at a rate of one to two inches per second. The lower the energy of the radiation, the slower the scan rate.
  6. For most surveys, in areas of greater than 300 cpm background radiation, use a wipe survey (see Section 12.2.7, below) or wipe the area with a dry wipe and count with a portable instrument. Note: H-3 work areas must be wiped as noted in Section 12.2.7.
  7. Taking the highest reading in the scanned area and subtracting the background count determines the final level.

Record surveys upon completion. See Section 12.2.9, Recording the Monthly Surveys.

12.2.7 Wipe Survey Procedures

An instrument survey may be performed prior to a wipe survey to minimize the chance of inadvertently spreading contamination and to identify areas requiring greater attention in wipe sampling. In areas of suspected contamination, wear gloves. To perform a wipe survey:

  1. While applying pressure, run a small piece of dry filter paper over the surface to be surveyed. A standard area approximating 100 square centimeters should be covered with each wipe to allow comparison of results.
  2. Place in LSC vial; fill vial approximately 3/4 full of scintillation fluid.
  3. In addition to the survey wipes, prepare background vial with new filter paper.
  4. Count in liquid scintillation counter for one minute. Channels can be set for specific isotopes or labs can use full channel spectrum for gross contamination.
  5. Take the highest reading in the wiped area and subtract the background count to determine the final level.

See Section 12.2.9, Recording the Monthly Surveys.

12.2.8 Survey Results

  1. If contamination above the action level (see Section 12.2.10) is found, do one of the following:
    a. Clean the item or area until contamination drops below the action level; or
    b. Label the contaminated item or area with the radiation symbol and take proper precautions to prevent exposure; or
    c. Dispose of the item as radioactive waste.
    d. Notify the RSO for help with decontamination.
  2. Notify the RSO of all areas of fixed contamination above the action level. Areas with fixed contamination must be marked and labeled with date of discovery, suspected or known isotope and count rate. The RSO must evaluate the need for further actions for fixed contamination areas.

12.2.9 Recording the Monthly Surveys

Labs should use either a preprinted map provided by EH&S or a lab-drawn map. The lab may also have a master map indicating areas that will be surveyed regularly, with a log form from EH&S to record multiple surveys.

  1. Prominent items or areas should be labeled on the map for orientation.
  2. Record the make, model, and serial number of the instrument used.
  3. Perform the wipe or instrument survey as instructed in Section 12.2.6 or Section 12.2.7.
  4. Record the count rate (in cpm) of any contamination found both before and after cleaning, along with the background count rate.
  5. Sign and date the survey and keep it in the notebook so others can review it.

Labs must maintain surveys for review for three years.

See also Section 4, Recordkeeping Procedures.

12.2.10 Contamination Action Levels

  1. An area must be decontaminated if the loose contamination level exceeds 200 cpm above background by wipe or direct scan following completion of work.
  2. Work areas should be kept at levels of less than 500 cpm during experiments where practical.
  3. Gloves should be changed when a level of greater than 100 cpm is measured.
  4. If an area shows a fixed contamination level greater than 200 cpm above background, mark the area and notify the RSO.
  5. Airborne levels must be maintained such that no one will be exposed to greater than 10% of the derived air concentration (DAC). DAC is the concentration of radioactive material in air that will result in an annual intake limit.
  6. Surveys in non-radioactive work areas, such as desks, hallways, and floors will be documented, and areas must be decontaminated if loose contamination levels exceed 200 cpm above background levels. Standard laboratory practice is to keep contamination levels in these areas as low as reasonably achievable (ALARA).
  7. Staff with fixed or loose skin contamination greater than 100 cpm must be decontaminated. Clothing or personal items with levels of greater than 100 cpm should be decontaminated or removed and given to EH&S for storage during the period of radioactive decay.

See Section 12.2.8, Survey Results, for steps to take if the action levels are exceeded.

12.2.11 Lab Closeout and Decommissioning Surveys

A researcher who wishes to remove a laboratory used for radioactive work from an RMUA must:

  1. Submit an amendment RMUA form to EH&S.
  2. Remove and/or dispose of all contaminated equipment and radioactive material and waste. This should be coordinated through EH&S.
  3. Perform an instrument and a wipe survey of all areas in the lab where radioactive materials were used or stored. Decontaminate all areas which test at levels greater than 200 cpm above background. Pay attention to hood areas, sinks, and refrigerators in addition to work areas. Note all areas of fixed contamination greater than 200 cpm above background.
  4. Contact EH&S to allow the RSO to perform a confirmation survey in that space.
  5. When approved by EH&S, remove all postings, marking and labels used for radioactive material.

Note: EH&S will perform a second comprehensive instrument and wipe survey for all spaces which will never again be used for radioactive work.

12.2.12 Exposure Survey

An ionization chamber specifically designed and calibrated to measure external radiation levels in air is required for an exposure survey. Labs do not usually need these types of instruments. EH&S will perform an exposure survey when necessary.

Exposure surveys are only required to be performed for large quantities of high energy gamma-emitting radionuclides, such as 131I,51Cr and 137Cs.

The instrument used must be able to measure dose rates down to 0.1 mR/hr.

Do not use a NaI probe or a GM probe unless it is specifically calibrated for the type of radiation you are measuring.

Quickly measure the dose rates at three feet, at one foot, and at the surface of the source of radiation.

12.2.13 Exposure Rate Action Levels

If the dose rates are great enough that someone can receive greater than five mrem in one hour at a distance of 30 cm from a source of radiation, the area must be posted as a radiation area.

Non-restricted areas where the general public could be exposed to radiation must be controlled so possible doses in those areas are less than two mrem in one hour.

Dose rates should be reduced in accordance with ALARA principles whenever practical.

12.2.14 Recording the Exposure Rate Survey

  1. All exposure surveys are recorded. To record a survey:
  2. Draw a layout diagram of the lab and identify features or use a preprinted map.
  3. Identify the source(s) of radiation.
  4. Record the make, model, and serial number of the instrument used to measure the dose rate.
  5. Record the dose rates at the surface, at a distance of one foot, and at a distance of three feet from the source(s) of radiation.
  6. If the radiation is shielded, record the radiation levels both before and after shielding is installed.
  7. Sign and date the survey and post it in the area so others can review it.

12.2.15 Air Concentration Survey

EH&S will perform air concentration surveys when radioactive material has a significant potential to become airborne and staff are exposed via inhalation to levels that could lead to exposure greater than 10% of the annual limit on intake (ALI). This should not happen under normal working conditions. Contact EH&S for more information regarding inhalation exposure to radioactive materials.

12.3 Laboratory Use Audits

When radioactive material is used in the lab, the following items must be checked for and maintained each quarter. EH&S checks for these items during routine audits, and reports any deficiencies to the lab for correction.

  1. Radiation use and storage areas are properly posted with the Caution - Radioactive Material sign.
  2. Radioactive waste containers are properly used and conspicuously labeled with the radiation symbol and Caution - Radioactive Material warning.
  3. Radioactive waste is not disposed of as normal trash.
  4. Lab glassware is not used for food or drink purposes and food and drink containers are not used for radioactive materials.
  5. Food and drink are neither prepared nor consumed in labs posted for radioactivity, and not stored in refrigerators or coolers used for radioactive material storage. Food and drink are prohibited in all labs.
  6. Surveys are being performed as required (i.e., monthly).
  7. Sewer disposal logs are being maintained adequately.
  8. Area where radioactive material is used is kept clean.
  9. Survey instruments are available and operational.
  10. Dosimetry is being worn, along with proper PPE.
  11. Radioactive vial records are being maintained.

The lab is responsible for correcting any deficiencies in a timely manner once notified.