Activity Depth Profiling of HIFAR Reactor at ANSTO, Lucas Heights, Australia

Scope:

HIFAR was Australia’s first multi-purpose research nuclear reactor, a pressurized heavy water reactor that operated from 1958 to 2007
Depth profiling of the reactor shell was performed to support future dismantling and disposal of the activated components
The TruPro^® patented technology was selected by ANSTO to avoid cross-contamination as drilling is less invasive and contaminating than the standard coring method
The goal of this project for ANSTO was to perform the facility characterization using New Millennium Nuclear Technologies International, Inc’s (NMNTI) TruPro^® patented technology coupled with the CANBERRA™ alpha /beta /gamma analytical capabilities to assess the levels of material activation while still maintaining the integrity of the building

To maintain ALARA principles, the reactor shell had to be characterized to understand levels of activation in different materials and to generate activity depth profiles prior to dismantlement
Three locations were used to sample different zones of the reactor shell
The duration of the work was four weeks, with 100 samples collected and analyzed
Sampling of several different materials including steel, lead, graphite, concrete, lead-shot concrete, aluminum and boral, was required
Same-day analytical results were required
Specific radionuclides of concern included Ba-133, Co-60, Cs-137, Eu-152, Eu-154, Eu-155, and Zn-65
Gamma detection limits of <0.1 Bq/g were to be maintained for all radionuclides of concern
Working space for drilling was very limited within the HIFAR building

A temporary on-site analytical lab was set up in an adjacent building for sample analysis. The required measurements included gamma spectroscopy, gross alpha, and gross beta counts
NMNTI’s TruPro^® patented technology collected powdered samples into 250 ml sample jars
The TruPro^® technology is capable of sampling a wide range of materials, including concrete, lead, graphite, and steel
The sampling depth was recorded for each sample
The CANBERRA ISOCS system was the appropriate choice for gamma measurements
A separate ISOCS efficiency model that accounted for the sample material type and density, the sample geometry, and the intrinsic detector efficiency, were generated for each sample collected
The complete gamma system included two ISOCS HPGe detectors, 25 mm lead shielding, InSpector 2000 MCA’s, and ISOCS and Genie 2000 analysis software
Typical gamma count times were 20 minutes per sample
Same-day gamma analyses were performed
Gross alpha/beta counts were performed on subsamples using the CANBERRA iSolo instrument

All layers of the HIFAR reactor shield were successfully sampled
Three different locations were drilled. Depth profiles of detected activation products were generated for all three locations. All of the relevant radionuclides were detected and quantified
Distinct material layers were sampled with no cross contamination
100 samples were measured over 20 working days
Throughputs were up to 20 samples per day
Gamma detection limits were maintained below 0.1Bq/g for all radionuclides of concern and for all samples
All gamma analyses were completed and reported to the customer on the same day as sample measurement
Gross alpha/beta counts were performed for all samples
The TruPro^® patented technology approach was faster, cheaper, and safer than traditional core drilling
The successful joint effort demonstrated that the CANBERRA solutions are well suited for analysis of samples obtained with TruPro^®
Personnel doses were maintained ALARA. Control of radioactive material was maintained throughout the project