P-32 Standard Operating Procedures (Version: May 1997)

Introduction

Phosphorus-32 is a commonly used radionuclide with a half-life of 14.3 days, emitting beta particles with a maximum energy of 1.71 MeV (Million Electron Volts). The beta particles travel a maximum of 20 feet in air at maximum energy. See Appendix A for information on the rate at which P-32 decays. 

Concerns

The major concerns with using P-32 are:

  • Surface radiation exposure to the skin of the hands. A drop of contamination containing 1 microcurie of P-32 on 1 cm2 area of the skin produces an exposure of 2,000 millirems / hour. One microcurie = 2.22 x 106 dpm (disintegrations per minute).
  • Radiation exposure in air over an open vial. The dose rate at the opening of a vial containing 1 millicurie of P-32 can be as high as 26,000 millirems per hour.

This means that the quarterly SUNY As Low As Reasonably Achievable (ALARA) limit of 1,875 millirems for the hands would be reached in a little over 4 minutes.

  • Working with P-32 orthophosphate in high concentrations. Using orthophosphate poses significant problems because of the large activity and high concentrations (i.e., 5 millicuries in 10 lambda!). If you can avoid using high concentrations, please do so.

Our experience at SUNY has shown that laboratories using pre-labeled P-32 (dATP, etc.) in activities of 0.25 and 0.5 millicuries have had little or no safety problems.

Using lower concentrations is very desirable. Most companies will provide lower concentrations if requested. The cost of using pre-labeled materials or lower concentrations is higher but the return in safety more than offsets the additional cost.

Shielding

Plexiglas (lucite) is the best shield for beta particles from P-32. When more than 1 millicurie of P-32 is handled, a sufficient number of x-rays (bremmstrahlung) may be formed to require Lead foil to be added to the exterior of the shield. The beta particles travel a maximum of 3.1 mm. in glass, 6.7 mm. in lucite, and 8 mm. in tissue.

Detection

A tiny drop of contamination of P-32 can be easily detected with an end window Geiger Counter.

Equipment / Supplies

The following equipment and supplies must be available:

  • A Geiger Counter sensitive to beta particles
    • This device will allow the detection not only of P-32 beta particles but also the secondary x-rays.
  • 3/8" or 1/2" Plexiglas benchtop shield.
    • These are available from many lab equipment vendors such as VWR, Fisher, etc. and cost $150-$250.
    • If you are going to handle more than 1 millicurie, we recommend the 1/2" thickness.
  • disposable latex or plastic gloves.
  • Ring badge (need to be determined by the RSO).
  • full-length lab coat.
  • Plexiglas containers for radioactive waste.
    • These are available from many lab equipment vendors such as VWR, Fisher, etc.
  • pipettes dedicated to the use of P-32.
  • plastic safety glasses.
  • commercial decontaminate, i.e. DuPont's "Count Off".
  • absorbent bench covering or tray.

Safety Rules

If the following safety rules are followed, personnel radiation exposure will be as low as reasonably achievable.

  1. Designate a specific area of the lab for P-32 handling.
    • Place the Plexiglas shield near a wall on top of absorbent bench paper or pads (not toward another work area on the other side of the bench) away from the main flow of traffic in the lab.
  2. All persons handling P-32 and issued a ring badge must wear the ring badge inside the disposable glove on the hand which is most frequently used to handle vials, samples, pipettes, etc. containing P-32. The sensitive portion of the ring badge must face the radioactive material.
  3. Full-length lab coats must be worn by all persons who handle P-32.
  4. Protect the skin of your hands from becoming contaminated by wearing two pairs of disposable gloves.
  5. A Geiger counter must be in operation during the experiment, and preferably at all other times.
    • To avoid contaminating the detector, a thin sheet of plastic (i.e., Saran Wrap) may be placed around the detector
  6. Place all vials and test tubes containing P-32 behind a 3/8" or 1/2" thick Plexiglas shield.
    • Check the radiation level in front of the shield to determine if Lead foil should be added to block out the x-rays (called bremmstrahlung) formed by the beta particles interacting with the Plexiglas.
  7. Do not work directly over an open container of P-32.
  8. Never pipette P-32 or "any radionuclide" by mouth.
  9. Only use pipettes which have been dedicated to your specific use of P-32.
    • Pipettes will easily become contaminated and therefore, should not be shared with others.
  10. Use the Geiger Counter to check your gloves frequently for contamination.
    • If contamination is found, immediately dispose of the gloves in the radioactive waste container

Post-Use Procedures

After handling P-32:

  • Use the Geiger Counter to check your hands, shoes, clothing, work bench, floor, centrifuges, and water baths for contamination.
  • If any contamination is found on your shoes and/or clothing, contact the RSO. You will likely have to remove it temporarily until the radiation decays to background. The RSO has some disposable clothing that you can wear home, but we do not have any shoes.
  • If any contamination is found on your hands, wash thoroughly with soap and water. This will usually be sufficient to remove the surface contamination. If it does not, contact the RSO for assistance.
  • If any contamination is found on the work bench, floor, or lab equipment, use a commercial radiation contamination remover (i.e. Count Off) with paper towels to clean up the equipment. Place the towels in the radioactive waste receptacle.
  • If contamination cannot be removed, place a "radiation" label on the equipment indicating that it is P-32, maximum cpm found, and the date you measured the level.
  • If contamination cannot be removed from the floor, contact the RSO to obtain shielding materials.
  • Inform your fellow lab workers if any unremovable contamination is found.
  • Check the normal trash container to make sure no radioactive waste has been accidentally placed there.
  • Store the waste temporarily in Plexiglas containers or other containers which are sufficient to absorb P-32's beta particles.
  • Complete the Survey log.
  • Call the RSO if you have any questions about where to survey, or how to fill out the form.
  • Wash your hands thoroughly after using P-32.
  • Bring the waste to the RSO frequently. Do not let it pile up. The RSO accepts waste every Thursday or other times by arrangement. Call 464-6510 with any questions.

Any questions about these procedures?

Call the Radiation Safety Office: 464-6510


APPENDIX A
DECAY RATE OF P-32
Days Elapsed % of Activity Remaining Decay Factor
0 100.0 1.00
1 95.3 0.953
2 90.8 0.908
3 86.5 0.865
4 82.4 0.824
5 78.5 0.785
6 74.8 0.748
7 71.2 0.712
8 67.8 0.678
9 64.6 0.646
10 61.6 0.616
11 58.7 0.587
12 55.9 0.559
13 53.2 0.532
14 50.7 0.507
15 48.3 0.483
16 46.0 0.460
17 43.8 0.438
18 41.8 0.418
19 39.8 0.398
20 37.9 0.379
21 36.1 0.361
22 34.4 0.344
23 32.2 0.328
24 31.2 0.312
25 29.7 0.297
26 28.3 0.283
27 27.0 0.270
28 25.7 0.257
29 24.5 0.245
30 23.3 0.233
... ... ...
143 (10 half-lives) 0.1 0.001

For example, if your vial contained 500 microcuries of P-32 on 7/1/90, the amount of activity remaining on 7/8/90 (7 elapsed days) would be:

Activity x Decay Factor = 500 microcuries x 0.712 = 356 microcuries