ADVANCED STUDIES ON GAMMA BLINDNESS, HIGH RESOLUTION HYBRID MASS ALPHA STPECTROSCOPY/EXTRACTION AND NEUTRON DETECTION WITH CTMFDS

<p>The primary focus of this thesis pertains to R&D results associated with deploying tensioned</p> <p>metastable fluid detector (TMFD) technology for monitoring of spent nuclear fuel</p> <p>(SNF) for actinide content from their neutron emissions while under extreme photon backgrounds</p> <p>(> 150 Gy/h), as may be expected within a hotcell. Traditional state-of-the-art</p> <p>neutron detectors such as 3He and BF3 based systems are well-known to be dysfunctional</p> <p>under such conditions, despite having pulse-shaped discrimination capabilities that allow</p> <p>them to differentiate photons vs. neutrons. The aim of this thesis was to test the ‘gamma</p> <p>blind’ ability of the centrifugally tensioned metastable fluid detector (CTMFD) based system,</p> <p>to monitor for actinide generated neutrons despite the anticipated high intensity gamma</p> <p>background, a goal which was successfully accomplished. Methods, designs, and experimental</p> <p>procedures are discussed for successful neutron monitoring from an Americium-Beryllium</p> <p>neutron source, as well as results showing no hindrance to neutron detection capability at</p> <p>modest negative pressure states through 150 Gy (15 kRad) accumulated gamma dose.</p> <p>A secondary focus was the ability of the TMFD based systems to perform alpha spectroscopy</p> <p>on closely separated (<10 keV) alpha particle emissions from 239Pu and 240Pu</p> <p>isotopes. Due to the closely spearated alpha decay energies, this feat could previously only</p> <p>be perfromed by tedious and expensive mass-spectrometry based systems. Instead, a wet</p> <p>chemistry apporach for detecting trace (? 10−3 Bq/mL) quantity alpha radiation with high</p> <p>alpha energy resolution (<10 keV) was developed and validated using the CTMFD system.</p> <p>Using this technique, mixtures containing samples of 239Pu:240Pu with activity concentrations</p> <p>ranging in ratio from 1:0 to 0:1 were able to be identified within ±12% accuracy.</p> <p>Lastly, successful assessments were conducted for detecting neutron emissions from a 1</p> <p>Ci Plutonium-Beryllium source under a variety of shielded configurations using a CTMFD</p> <p>and a 3He based Ludlum 42-49BTM detector. Concrete, lead, and water shielding materials</p> <p>of thicknesses ranging from 0 to ?30 cm were placed as shielding material, with the</p> <p>CTMFD configured only for fast energy neutron detection. Monte Carlo N-Particle Transport</p> <p>(MCNP) code-based simulations were performed for derivation of the neutron energy</p> <p>spectrum incident on the detectors to compute sensitivity estimates. At 0.6 MPa (6 bar) negative pressure, the CTMFD was determined to offer up to 7 times higher sensitivity vs the</p> <p>Ludlum 42-49B, though further increasing the negative pressure state to 1.1 MPA (11 bar)</p> <p>exponentially increases the sensitivity to offer 100+ times higher sensitivity for the CTMFD</p> <p>vs the Ludlum 42-49B.</p>