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Title: PVT Degradation Studies: NMR Analysis

Abstract

Under certain environmental conditions, polyvinyl toluene (PVT) plastic scintillator has been observed to undergo internal fogging. Nuclear magnetic resonance spectroscopy has been used to elucidate the state of water inside the PVT. The deuterium NMR results show that water absorbed by PVT under warm, humid conditions enters several distinct environments, and when the PVT is transferred from incubation to ambient temperature and humidity the water is lost on a time scale of a few hours from these samples. Most of the deuterium NMR peaks can be assigned to bulk liquid water, but almost 35% of the detected signal intensity is contained in a resonance that resembles spectra of water contained in nanometer-scale pores in mesoporous carbon.

Authors:
 [1];  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE; Dept. of Homeland Security (DHS) (United States)
OSTI Identifier:
1411933
Report Number(s):
PNNL-26530
830403000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; PVT; NMR spectrometry; PVT degradation

Citation Formats

Cho, Herman M., and Kouzes, Richard T.. PVT Degradation Studies: NMR Analysis. United States: N. p., 2017. Web. doi:10.2172/1411933.
Cho, Herman M., & Kouzes, Richard T.. PVT Degradation Studies: NMR Analysis. United States. doi:10.2172/1411933.
Cho, Herman M., and Kouzes, Richard T.. Tue . "PVT Degradation Studies: NMR Analysis". United States. doi:10.2172/1411933. https://www.osti.gov/servlets/purl/1411933.
@article{osti_1411933,
title = {PVT Degradation Studies: NMR Analysis},
author = {Cho, Herman M. and Kouzes, Richard T.},
abstractNote = {Under certain environmental conditions, polyvinyl toluene (PVT) plastic scintillator has been observed to undergo internal fogging. Nuclear magnetic resonance spectroscopy has been used to elucidate the state of water inside the PVT. The deuterium NMR results show that water absorbed by PVT under warm, humid conditions enters several distinct environments, and when the PVT is transferred from incubation to ambient temperature and humidity the water is lost on a time scale of a few hours from these samples. Most of the deuterium NMR peaks can be assigned to bulk liquid water, but almost 35% of the detected signal intensity is contained in a resonance that resembles spectra of water contained in nanometer-scale pores in mesoporous carbon.},
doi = {10.2172/1411933},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jun 06 00:00:00 EDT 2017},
month = {Tue Jun 06 00:00:00 EDT 2017}
}

Technical Report:

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  • Under certain environmental conditions, polyvinyl toluene (PVT) plastic scintillator has been observed to undergo internal fogging. This document reports on a study of acoustic techniques to determine whether they can provide a diagnostic for the fogging of PVT. Different ultrasound techniques were employed for detecting the level of internal fogging in PVT, including wave velocity measurements, attenuation, nonlinear acoustics, and acoustic microscopy. The results indicate that there are linear relations between the wave velocity and wave attenuation with the level of internal fogging. The effects of fogging on ultrasound wave attenuation is further verified by acoustic microscopy imaging, where regionsmore » with fog in the specimen demonstration higher levels of attenuation compared to clear regions. Results from the nonlinear ultrasound measurements were inconclusive due to high sensitivities to transducer coupling and fixture variabilities.« less
  • Polyvinyl Toluene (PVT) plastic scintillator is the most common gamma ray detector material used for large systems when only gross counting is needed because of its low cost, robustness, and relative sensitivity. PVT does provide some energy information about the incident photons, as has been demonstrated through the development of Energy Windowing analysis. There is a more sophisticated energy analysis algorithm developed by Symetrica, Inc., and they have demonstrated the application of their deconvolution algorithm to PVT with very promising results. The thrust of such a deconvolution algorithm used with PVT is to allow for identification and rejection of naturallymore » occurring radioactive material, reducing alarm rates, rather than the complete identification of all radionuclides, which is the goal of spectroscopic portal monitors. Under this condition, there could be a significant increase in sensitivity to threat materials. The advantage of this approach is an enhancement to the low cost, robust detection capability of PVT-based radiation portal monitor systems. The success of this method could provide an inexpensive upgrade path for a large number of deployed PVT-based systems to provide significantly improved capability at a much lower cost than deployment of NaI(Tl)-based systems of comparable sensitivity.« less
  • Propagation-of-error calculations were performed for material balance areas for processes involving the handling of bulk quantities of tritium gas. Random and systematic error components were obtained from pressure, volume, temperature, and isotopic measurements performed by Mound measurement control and calibration programs. The resultant error components were used to determine the uncertainties in determinations of physical inventories and material flow through material balance areas.
  • A modification of a purge-and-trap unit is described for use in microbiological studies concerning degradation of aliphatic halogenated hydrocarbons (halocarbons). Sealed serum tubes containing bacteria, aqueous medium, headspace, and volatile halocarbons are used as purge vessels to monitor the disappearance of the halocarbons. Data are presented to show the loss of volatile halocarbons that occurred when these systems were analyzed by standard purge-and-trap. An application of this method is shown with methane-utilizing bacteria. The modified purge-and-trap method resulted in a total measurement of halocarbons in the sample without making a transfer to a separate purge vessel.