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Radiochemical Processing Laboratory

Reactor Dosimetry

Reactor Characterization and Safety

The Analytical Chemistry Laboratory conducts radiochemistry and reactor dosimetry measurements for clients at commercial nuclear reactors, test and research reactors at universities and other U.S Department of Energy national laboratories, and accelerator-based neutron sources. Located in Richland, Washington, Pacific Northwest's client base extends to Europe and Asia.

Comprehensive Services

Photo: Typical dosimetry capsule with neutron and helium monitors
Typical dosimetry capsule with neutron and helium monitors. (Enlarge image)

What sets us apart is our years of experience in developing techniques and monitors to make measurements in complex reactor environments and our computer programs to determine fundamental neutron exposure and radiation damage parameters. We provide clients with comprehensive services including neutron fluence and spectral measurements, hydrogen and helium gas measurements, and extensive computer calculations of radiation damage effects.

We have developed small neutron flux monitor capsules containing 14 or more materials for the simultaneous measurement of multiple neutron activation reaction products. Our inventory of highly-pure and well-characterized materials includes titanium, manganese, scandium, iron, nickel, boron, lithium, cobalt, copper, gold, lutetium, beryllium, aluminum, and various isotopes of plutonium, uranium, and neptunium. One small capsule can contain both radiometric and helium gas monitors. Our ability to combine multiple monitors into one capsule and to provide comprehensive reactor services, minimizes the need for reactor irradiation time, providing lower cost and faster service to our clients.

Monitor capsules are custom designed to meet our client's needs which vary from simple measurements in test reactors up to fully documented and qualified materials to meet the most stringent commercial reactor QA requirements. Capsules can be designed to survive multi-year exposures at high-temperature in high-flux neutron fields at any accessible reactor location from in-core positions to the reactor pressure vessels.

Monitors can be placed at a variety of locations at the same time to map reactor environments. Following irradiation, capsules are returned to Pacific Northwest where we have hot cells to open highly-radioactive capsules and retrieve the monitors for testing. We have a comprehensive suite of analytical instrumentation allowing measurements of activation products by gamma spectrometry, alpha or beta counting following radiochemical separations, mass spectrometry on radioactive or stable isotopes, and hydrogen and helium gas measurements. Such measurements are also performed on reactor components themselves following removal from reactors. This retrospective dosimetry technique has proven highly useful for studying plant life extension in aging commercial reactor facilities. Helium and transmutation product measurements are especially useful for very long irradiations since they are not limited by radioactive decay.

We have developed the STAY'SL computer code to combine all of these different types of data to determine the neutron flux and energy distribution. Evaluated nuclear cross section data and their uncertainties are combined with reactor physics calculations and our radiometric or transmutant measurements using a least-squares procedure to find the most probable solution. The adjusted neutron flux spectrum can then be used to calculate a wide array of fundamental radiation damage effects in over 40 pure elements using the SPECTER computer code:

  • Atomic displacements per atom (dpa).
  • Primary atomic recoil energy distributions.
  • Hydrogen and helium gas production.
  • Atomic transmutation.
  • Activation of materials.

The SPECOMP computer code can further be used to determine these radiation damage effects in alloys, ceramics, and other compound materials.

We have pioneered the extension of these methods to high-energy neutron fields created at particle accelerators using the T(d,n) 14 MeV fusion reaction, Be and Li(d,n) reactions up to 40 MeV, and spallation reactions up to 800 MeV. Our monitors have been used to both characterize these complex neutron fields and to measure fundamental nuclear reaction cross sections.

Point of Contact:
Larry Greenwood, Nuclear Chemistry & Engineering
Phone: (509) 375-5301

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