Wipe test counter

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A wipe test counter is a device used to measure for possible radioactive contamination in a variety of environments. When using radioactive materials it is necessary to test for accidental contamination, whether from use of liquid unsealed sources or to check for leaking sealed sources. A swab or small absorbent smear can be used to “wipe” an area, the wipe is then placed into a test tube and counted, typically using a gamma counter. Testing for leaks in this manner is a method described in the ISO 9978 standard. [1]

Radioactive contamination Presence of radioactive substances where they are undesirable

The sources of radioactive pollution can be classified into two groups: natural and man made.

Radioactive source

A radioactive source is a known quantity of a radionuclide which emits ionizing radiation; typically one or more of the radiation types gamma rays, alpha particles, beta particles, and neutron radiation.

Test tube

A test tube, also known as a culture tube or sample tube, is a common piece of laboratory glassware consisting of a finger-like length of glass or clear plastic tubing, open at the top and closed at the bottom.

Contents

Equipment

Survey instruments may be used to detect surface contamination without requiring wiping, however this requires careful calibration and technique to ensure adequate sensitivity is achieved. [2]

Survey meter

Survey meters in radiation protection are hand-held ionising radiation measurement instruments used to check such as personnel, equipment and the environment for radioactive contamination and ambient radiation. The hand-held survey meter is probably the most familiar radiation measuring device owing to its wide and visible use.

A gamma counter is a typical choice for measuring wipe samples for radioactivity as it allows multiple tests to be counted in a largely automated way.These systems detect radiation using a scintillator and photomultiplier tube and may allow the energy spectrum of a sample to be recorded, which can be used to identify the contaminant. [3] [4]

Scintillator

A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate. Sometimes, the excited state is metastable, so the relaxation back down from the excited state to lower states is delayed : the process then corresponds to either one of two phenomena, depending on the type of transition and hence the wavelength of the emitted optical photon: delayed fluorescence or phosphorescence.

Use of a gamma camera has also been proposed, where collimators are removed to improve sensitivity. [5]

Gamma camera

A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy. The applications of scintigraphy include early drug development and nuclear medical imaging to view and analyse images of the human body or the distribution of medically injected, inhaled, or ingested radionuclides emitting gamma rays.

Regulation

Wipe testing is typically a requirement of licenses to hold radioactive materials. In the United States the Nuclear Regulatory Commission requires wipe testing of sealed sources "periodically" using equipment sensitive down to 185 Becquerels. [6] In the United Kingdom the Health and Safety Executive guidance for the Ionising Radiations Regulations 1999 requires wipe testing (usually every two years) and it is also likely to be a requirement of Environment Agency permits. [7] [8] In Australia licence conditions may require adherence to Australian standard AS2243.4 and ISO 9978 for wipe testing of sealed sources. [9]

United States Federal republic in North America

The United States of America (USA), commonly known as the United States or America, is a country comprising 50 states, a federal district, five major self-governing territories, and various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is slightly smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U.S. is the third most populous country. The capital is Washington, D.C., and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico. The State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean. The U.S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The extremely diverse geography, climate, and wildlife of the United States make it one of the world's 17 megadiverse countries.

Nuclear Regulatory Commission government agency of the United States

The Nuclear Regulatory Commission (NRC) is an independent agency of the United States government tasked with protecting public health and safety related to nuclear energy. Established by the Energy Reorganization Act of 1974, the NRC began operations on January 19, 1975 as one of two successor agencies to the United States Atomic Energy Commission. Its functions include overseeing reactor safety and security, administering reactor licensing and renewal, licensing radioactive materials, radionuclide safety, and managing the storage, security, recycling, and disposal of spent fuel.

United Kingdom Country in Europe

The United Kingdom (UK), officially the United Kingdom of Great Britain and Northern Ireland, and sometimes referred to as Britain, is a sovereign country located off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland, and many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state, the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world. The Irish Sea lies between Great Britain and Ireland. With an area of 242,500 square kilometres (93,600 sq mi), the United Kingdom is the 78th-largest sovereign state in the world. It is also the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017.

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Scintillation counter

A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses.

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Gamma counter

A gamma counter is a machine to measure gamma radiation emitted by a radionuclide. Unlike survey meters, gamma counters are designed to measure small samples of radioactive material, typically with automated measurement and movement of multiple samples.

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References

  1. ↑ "ISO 9978:1992 Radiation protection -- Sealed radioactive sources -- Leakage test methods" (PDF). Public.Resource.Org. Retrieved 27 February 2017.
  2. ↑ "Information Notice No. NO. 93-30: NRC Requirements for Evaluation of Wipe Test Results; Calibration of Count Rate Survey Instruments". Nuclear Regulatory Commission. 12 April 1993. Retrieved 27 February 2017.
  3. ↑ Rayburn, Stephen R (1990). The Foundations of Laboratory Safety a Guide for the Biomedical Laboratory. New York, NY: Springer New York. p. 206. ISBN   9781461233206.
  4. ↑ Lombardi, Max H (2006). Radiation Safety in Nuclear Medicine (2nd ed.). Hoboken: CRC Press. p. 129. ISBN   9780849381799.
  5. ↑ Friede, Juan; Dumesnil, Cecile; Caron, Camille (1990). "Gamma Camera and Computer-Assisted Wipe Tests: A Simple Method". Journal of Nuclear Medicine Technology. 18 (1): 49–51. ISSN   0091-4916.
  6. ↑ "10 CFR 39.35 Leak testing of sealed sources". Nuclear Regulatory Commission. Retrieved 27 February 2017.
  7. ↑ Health & Safety Commission (2000). Work with ionising radiation : Ionising Radiations Regulations 1999 approved code of practice and guidance. London: HSE Books. ISBN   9780717617463.
  8. ↑ "Sealed sources: how to comply with your EPR RSR environmental permit". Environment Agency. 2011. Retrieved 27 February 2017.
  9. ↑ "Wipe Testing of Sealed Sources & Use of Sealed Sources Beyond Recommended Working Life" (PDF). Australian Radiation Protection and Nuclear Safety Agency . February 2013. Retrieved 27 February 2017.
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