Concrete Slab and Footer Sampling, Characterization, and Analysis Using the TRUPRO® Sampling and Analysis System at the Ashtabula Environmental Management Project (AEMP)
The objective of this Facilities Project was to deploy and evaluate a concrete sampling and profiling tool developed and deployed by NMNTI to warehouse slabs and subsurface structures in support of cost effective and safe removal of the slabs and footers for the U.S. Department of Energy Ashtabula Environmental Management Project. The DOE is in the process of D&D for many of its nuclear facilities throughout the United States. These facilities must be dismantled and the demolition waste sized into manageable pieces for handling and disposal. The facilities undergoing D&D are typically chemically and/or radiologically contaminated. To facilitate this work, DOE required tools capable of profiling the bulk building materials to depth.
RMIES of Ashtabula, Ohio was engaged in the closure of AEMP. Pre-demolition surveys and potential decontamination of contaminated concrete slabs were important to AEMP. NMNTI used the TRUPRO® Profiling System Equipment and the results acquired from warehouse slabs and subsurface footers at AEMP site using TRUPRO® were used to develop a more detailed subsurface radiological contamination profile from which a strategy of cleanup action can be derived.
There was a need to detect uranium and technetium-99 at depth within the building material matrix in real time to support the AEMP evaluation of cleanup goals for soil of uranium (30 pCi/gm) and technetium 99 (65 pCi/gm) and to allow for immediate response to contamination and increased worker safety awareness. The accepted method for detecting uranium isotopes was alpha and gamma spectrometry. For Tc-99 Liquid Scintillation Counting (LSC) of field swipes or digestion of sub-sampled cores was performed.
Profiling the concrete slabs and concrete slab subsurface material at AEMP to depth included the following desired capabilities and design features of the equipment: (a) powered by a mobile diesel electric power generator unit coupled to 200 foot power cables, (b) removed almost 90 samples of concrete using a specialized tungsten carbide drilling technology, (c) removed one-inch depths of potentially contaminated concrete from predetermined sampling points sequentially from depths of one half-inch to three feet (1/2 – 36 inch), (d) collected all concrete particulate from sampling operations into specialized filter units and (e) produced representative samples in a powdered form for optimal counting by a portable scintillation system and gamma spectrometer.
NMNTI’s findings indicated that there was measurable uranium and Tc-99 contamination at all the points sampled. Slab expansion joints and cracks around the Quench Tank, Campbell Saw pads and hot spot locations on footers of the Ramp Way and North East Warehouse Footers to depth were generally more contaminated than the bulk of the concrete slab material. The cracks were typically hotter than the pad values. Holding in mind that primarily hot spots were sampled to depth, activity profiles from the top half inch increment, the bulk incremental sample and the bottom incremental samples of each slab and its joints were developed. For most slab cracks and joints the middle bulk incremental sample was more active except for the Campbell Saw and Die Head sampled joints and cracks where the top and the bottom samples were more active respectively.
The radionuclide contamination data for concrete surfaces, cracks and slab subsurface soils, and incidental ground water, do not adequately characterize the extent or amount of site contamination that may exist on or off the site and adequate data does not exist to determine if contaminants exist in concrete slab sub-surfaces and soils or surface waters in quantities that might be dispersed to the air and working environment on slab removal. However at the points sampled on the slab pads, measurable contamination was found on the undersurfaces of RF6, Ramp Way, Quench Tank, North East Warehouse, RF3, and the Waste Water Treatment Plant slabs. Despite poor weather conditions including rain, snow, ice and slab surface conditions sampling and profiling to depths below slab surfaces and deep into footers to 36 inches at this site was relatively straightforward and can be used in the acquisition of incremental samples to measure levels of contamination.