The 13th International Conference on Environmental ... - Events

Abstracts
SESSION L3: Nuclide Assay
1) 40279 – Design of a facility for the automated receipt inspection and characterization of LILW using
integrated non-destructive examination and assay techniques
Stephen Halliwell, VJ Technologies Inc.� (USA)
KHNP is constructing two repositories, located in Bonggil-ri, Yangbukmyun, Gyeongju-si, Gyeongbuk, Korea, for
Low & Intermediate Level Radwaste. (LILW). <strong>The</strong> waste received is required to be inspected and characterized prior to
being placed into storage at the repository. This paper describes the design of an integrated system of non destructive
examination (xray), and non destructive assay (radiometric) instrument systems, waste package integrity checking
systems, waste handling mechanisms and data management and archival provisions, which comprise the Waste Receipt
and Inspection Facility (WRIF). <strong>The</strong> WRIF is designed to uncap transport containers, unload waste drums from
containers, safely examine the drums, to ensure they meet the waste acceptance criteria established by the LILW facility.
<strong>The</strong> drums are then loaded into waste disposal containers for transfer to the repository. <strong>The</strong> WRIF also receives larger
waste containers, which are characterized in a separate section of the WRIF, before being transferred to the repository.
Remote control and handling of the waste is a design requirement, as is the management, processing archival and
retrieval system for all data generated during waste characterization.
Importance of this work
Remotely controlled characterization of LILW in drums and large boxes, by the integrated system of
non-destructive and non-intrusive techniques in the WRIF, will minimize the risk of operator dose uptake, increase
operator safety, reduce the generation of additional waste, and save time and cost within the waste management process.
<strong>The</strong> data management, processing, archival and retrieval system will insure the data quality and integrity is maintained
over the required period of time, and that particular data can be easily and reliably accessed at any time.
2) 40167 – Feasibility Study on the Nuclide Analysis of the Radwaste Drum Using the Spectrum to Dose
Conversion Factor
Young-Yong Ji, Dae-Seok Hong, Tae-kuk Kim, Woo-Seog Ryu, KAERI (Korea Rep.)
<strong>The</strong>re are several methods for non-destructive assay of a radwaste drum that are based on the gamma ray scanning
and the in-situ objet counting system. Although these methods can be processed using high resolution, shielded detector
and specific correction techniques to quantitatively analyze the nuclides in a drum, time and cost constraints compared
with their accuracy dictate the use of simpler method to apply. Dose to curie (DTC) conversion method can simply and
easily provide a reasonable estimate of the nuclide inventory in a radwaste drum. <strong>The</strong> measured dose rate as well as the
relative abundance of gamma nuclides in a drum is a very important factor to be appreciated at the DTC conversion
method because of the direct linearity between the measured dose rate and the gamma emitters in a drum. <strong>The</strong> dose rate is
directly measured with the field detector. However, the relative abundance of gamma nuclides in a drum to be assayed is
determined form an indirect measurement using the material balance by the waste stream. <strong>The</strong> uncertainty of the nuclide
inventory of the assayed drum from the DTC conversion method could be increased because of the different detection
mechanism between the dose rate and the relative abundance of gamma emitters in a drum. Unfortunately, that expands
the limitation of using the DTC method. It is, therefore, necessary to find out a suitable measurement method of which
two variables could be obtained from the drum to be assayed at once. This method could be realized by using the dose
conversion factor, which has been widely using in the field of the environmental radiation measurement. <strong>The</strong> dose rate
from a drum could be directly calculated from the measured gamma ray spectra by using the dose conversion factor, and
also, the relative abundance of gamma nuclides could be easily obtained from the net count peaks in the spectra. In this
study, the dose conversion factor for 3”?x3” NaI(Tl) scintillation detector around lead shield with the thickness of about
3 cm was calculated by a MCNP code. <strong>The</strong> experimental verification for using this dose conversion factor was performed
by using the simulated drum that has several holes for locating a standard source.
3) 40255 – Portable Non-Destructive Assay Methods for Screening and Segregation of Radioactive Waste
Alan Simpson, Martin Clapham, Stephanie Jones, Randy Lucero, Pajarito Scientific Corporation (UK)
Significant cost-savings and operational efficiency may be realised by performing rapid nondestructive
classification of radioactive waste at or near its point of retrieval or generation. <strong>The</strong>re is often a need to quickly
categorize and segregate bulk containers (drums, crates etc.) into waste streams defined at various boundary levels (based
on its radioactive hazard) in order to meet disposal regulations and consignor waste acceptance criteria.
Recent improvements in gamma spectroscopy technologies have provided the capability to perform rapid in-situ
analysis using portable and hand-held devices such as battery-operated medium and high resolution detectors including
lanthanum halide and high purity germanium (HPGe). Instruments and technologies that were previously the domain of
complex lab systems are now widely available as touch-screen “off-the-shelf” units. Despite such advances, the task of
waste stream screening and segregation remains a complex exercise requiring a detailed understanding of programmatic
requirements and, in particular, the capability to ensure data quality when operating in the field. This is particularly so
when surveying historical waste drums and crates containing heterogeneous debris of unknown composition. <strong>The</strong> most
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