An Aerial Gamma Ray Survey of Springfields and the Ribble Estuary in September 1992

<p>A short aerial gamma ray survey was conducted in the vicinity of the Springfields site and Ribble Estuary from 1st-5th September 1992, to define existing background radiation levels, against which any future changes can be assessed. A twin engine AS 355 "Squirrel" helicopter chartered from Dollar Helicopters was used for this work. It was loaded with a 16 litre NaI(Tl) gamma ray detector and spectroscopy system on the 31st August and during the following days over 2700 separate spectra were recorded within a survey area of 20 x 12 km. Gamma ray spectra were recorded every 5 seconds at survey speed and altitude of 120 kph and 75 m respectively. A flight line spacing of 0.3km was chosen for the main survey area. On the 3rd September a low altitude, high spatial resolution (flight line spacing 100m and altitude 30m) was made over Banks Marsh (an area frequented by local wild fowlers).</p> <p>Survey results have been stored archivally and used to map the naturally occurring radionuclides 40K, 214Bi and 208Tl together with 137Cs and total gamma ray flux. In addition, for the first time, estimates of 234mPa in terms of deconvoluted count rate (normalised to 100m altitude) were made in the presence of 228Ac interference probably in disequilibrium with its parent thorium series.</p> <p>The maps provide a clear indication of the distribution and sources of environmental radioactivity in the Ribble at the time of the survey. The Ribble estuary is subject to regular and ongoing ground based studies by BNF, MAFF, HMIP, and University based groups, as a result of the authorised discharges of low level radioactivity from the Springfields site. The results of this survey complement this ground based work, and add to confidence that the estuarine system, it's associated sediments, tide washed pastures, salt marshes and river banks, have been thoroughly examined. There is support for earlier conclusions that the Cs on the salt marshes is the dominant source of external gamma exposure, and that the Springfields contribution to these locations is minor in comparison with this, Sellafield derived, signal. Upstream the situation is more complex, particularly where the dynamic sources of beta radiation are considered. As far as critical group assessments are concerned the survey provides clear evidence that the areas affected by 137Cs, where external gamma dose and possible food chain effects are of greatest interest, are in the lower reaches of the Ribble, whereas, at the time of the survey the 234mPa distribution was in the upper reaches of the river. This not only confirms the findings of ground based work, but provides some assurance that the different exposure paths (external gamma dose, skin dose) are not entirely synergistic. The discovery of possible transient sources of natural 228Ac in the salt marsh environment as a consequence of Th series disequilibrium immediately following spring tides is extremely interesting. If substantiated by further studies using semiconductor detectors this provides a new insight into the dynamic radiation environment of tide washed contexts.</p> <p>Aerial survey can potentially provide a rapid and cost effective means of studying environmentally dynamic sources such as 234mPa. In the case of the Ribble it would be necessary to reduce survey height to below 50m ground clearance to improve spatial resolution. Possible inconvenience to residents and property owners of such low altitude flights would have to be considered in addition to the potential value of environmental knowledge of the behaviour of short lived nuclides in a dynamic system such the Ribble estuary. There is nonetheless considerable potential for time series studies of this location. Recent flight trials by SURRC incorporating high efficiency germanium semiconductor detectors have verified the feasibility and potential a hybrid scintillation⁄ semiconductor spectrometer. Such a device can resolve any ambiguities arising from overlapping gamma ray peaks. This is particularly relevant to the confirmation of 228Ac in salt marshes. Ground based sampling at the time of measurement would enable concentration calibrations to be made for these dynamic sources. Further ground based measurements would be desirable to establish the extent to which low energy photons contribute to external gamma ray dose rates from sources with pronounced subsurface activity maxima.</p&gt

Modeling a Chemical Battlefield and the Resulting Effects in a Theater-Level Combat Model

This thesis describes the development of a methodology to model chemical weapons use in the Joint Staff\u27s Joint Warfare Analysis Experimental Prototype (JWAEP) and to quantify the resulting effects. The methodology incorporates organic unit assets and theater-level chemical assets into JWAEP by using the three principles of nuclear, biological, and chemical defense (NBC) which reflect joint and Army doctrine, and combines them with the basic concepts already used in existing theater-level models. Other aspects of the problem include representing chemical \u27packages\u27 on the battlefield, determining attrition and time effects, adjusting unit effectiveness, determining chemical package intelligence acquisition procedures, identifying solution techniques, verifying the results, and making recommendations. The proposed solution techniques provide a feasible methodology for integrating high resolution modeling into a low resolution model. The algorithms incorporate the chemical estimate process, Mission Oriented Protective Posture (MOPP) analysis, and employment of appropriate doctrinal unit tactics based on a perception of existing or potential chemical weapons use. Thus, the methodology provides accurate input into the JWAEP for approximating real world results as well as a structured and quantifiable framework reflecting joint and Army doctrine that can be used for stand alone chemical effects analysis

Windblown sand along railway infrastructures: A review of challenges and mitigation measures

Abstract The engineering interest about windblown sand is dictated by the harmful interactions between sand and a number of human infrastructures in arid environments. Particularly, the ongoing grand railway projects in the deserts of Far East, Middle East and North Africa regions require robust technical solutions to guarantee the efficient railway performance. The huge competences of the railway industry, traditionally developed in non-arid regions, should be developed and complemented to face mentioned challenges. The rationale problem setting, design, quantitative analysis and verification of sand mitigation measures are at present not sufficiently developed. The paper introduces original categorizations of both the windblown sand-induced performance deficiencies of the railway systems (windblown Sand Ultimate and Serviceability Limit States) and the prevention techniques to mitigate the windblown sand effects (Source-Path-Receiver categorization of the Sand Mitigation Measures). The state of the art is reviewed in the attempt to present the classification as accurately as possible. The main goal of the classification is to provide an orienting framework for scholars, railway owners, designers, general contractors and operators. We suggest the presented framework as a structured and organic base to properly set up future research activities, project terms of reference, most suited design solution, plan maintenance practices

Irregular wave runup statistics on plane beaches: application of a Boussinesq-type model incorporating a generating-absorbing sponge layer and second-order wave generation

Efficient absorption of reflected waves at the offshore boundary is a prerequisite for the accurate physical or theoretical modelling of long-duration irregular wave runup statistics at uniform, gently sloped beaches. This paper presents an implementation of the method suggested by Zhang et al. (2014) to achieve reflected wave absorption and simultaneous generation and propagation of incident waves in an existing numerical wave flume incorporating a moving boundary wavemaker. A generating–absorbing layer is incorporated within this 1DH hybrid Boussinesq-nonlinear shallow water equation model such that inshore-travelling incident waves, encompassing bound-wave structure approximately correct to second order, propagate unhindered while offshore-travelling reflected waves are absorbed. Once validated, the method is used to compile random wave runup statistics on uniform beach slopes broadly representative of dissipative, intermediate, and reflective beaches. Analyses of the individual runup time series, ensemble statistics and comparison to an empirical formula based on experimental runup data suggest that the main aspects of runup observed in the field are properly represented by the model. Existence of an upper limit on maximum runup is investigated using a simple extreme-value statistical analysis. Spectral saturation is examined by considering ensemble-averaged swash spectra for three representative beach slopes subject to incident waves with two different offshore significant wave heights. All spectra show f^−4 roll-off at high frequencies in agreement with many previous field studies. The effect is also investigated of the swash motions preceding one particular extreme runup event on the eventual maximum runup elevation