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HWF NOTES©


Gossman Consulting, Inc.                     April, 1992
Many of our clients have asked for a method to screen for radioactivity in hazardous waste fuels. This month's issue provides that method along with recommended instrumentation and check standards.

METHOD FOR THE SCREENING OF RADIOACTIVITY IN WASTE

1. SCOPE AND APPLICATION

1.1 To screen for radioactivity in samples of hazardous liquid or solid waste.

1.2 This standard is designed and intended as a preliminary test to compliment the more sophisticated quantitative analytical techniques that may be used to determine radioactivity in waste. This standard offers, to the user, the option and the ability to "screen" waste for potentially regulated levels of radioactivity when the more sophisticated techniques are not available and the total waste composition is unknown.

1.3 This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

2. SUMMARY OF METHOD

2.1 A sample is passed near the detector window of a Geiger counter, and the reaction of the meter is noted.

3. SIGNIFICANCE AND USE

3.1 Most hazardous waste treatment, storage, and disposal facilities receiving wastes from off-site do not handle radioactive materials. These facilities need a simple screening procedure for verifying that wastes being received are not radioactive.

4. INTERFERENCES

4.1 Due to the natural omnidirectional background radiation, occasional background noise (clicks or needle deflections) will be noticed. This method is not suitable for detecting low energy level alpha radiation.

4.2 Any person with a pacemaker or other apparatus which uses a low level radioactive source as an energy source (battery), including radium watch dials, may cause interference. Such interference can usually be tracked to its source using a portable instrument.

5. MATERIALS

5.1 Geiger counter/survey meter including a halogen quenched GM tube detector with a this mica end window, 1.5 - 2.0 mg/cm2 in thickness capable of detecting alpha radiation down to 2.5 MeV, beta radiation down to 50 KeV, and gamma radiation down to 10 KeV with a readout down to 0.1 mr./hr.

5.2 Low-level radioactive check source.

6. SAMPLE COLLECTION, PRESERVATION, AND HANDLING

6.1 No special sample collection, preservation or handling is necessary. The long-term exposure of any probe to a radioactive sample and/or radioactive check source should be avoided.

7. PROCEDURE

7.1 Place the open sample for screening within one centimeter of the Geiger counter or survey meter. If the sample is in a container, the top can be removed and the Geiger counter/survey meter detector window should be held within one centimeter of the surface. Hold this position for at least 10 seconds making sure the probe does not contact sample.

7.2 Note the presence of radiation by the increased frequency of clicks or deflection of the meter needle.

8. CALCULATIONS

8.1 None. Any positive result should warrant further investigation to determine the source and type of radiation.

9. QUALITY CONTROL

9.1 Instrument performance is evaluated each day the instrument is used.

9.2 Since there is no aliquot to be removed from the sample container, no other special QC procedures need be performed.

10. PRECISION AND BIAS

Since the results of the test are only intended to give a positive/negative rating to the material being tested, no statement will be made about the precision of this method.

References

(1) Meter successfully used: Radiation Alert Monitor 4.

Available from:
Lab Safety Supply, Inc.
P.O. Box 1368
Janesville, WI 5347-1368
(800)356-0783

(2) Successfully used radioactive sources, Federally exempt, 1 set consisting of polonium-210, 0.1 microcurie, t½=28 yr, cpbalt-60, 1 microcurie, t½=5.26 yr.

Available from:
The Nucleaus, Inc.
P.O. Box 2561
Oak Ridge, TN 37831
(615) 482-4041