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During the 5th Framework Program (FP5) the European Commission (EC) funded the PDS-XADS project (Preliminary Design Studies on an eXperimental Accelerator Driven System) mainly devoted to the demonstration of the feasibility of the coupling among an accelerator, a spallation target and a sub-critical core, and to preliminarily investigate the possibility of enhancing the transmutation rates for achieving values suitable for an Industrial Scale Transmuter.The on-going activities of the FP6 EUROTRANS integrated project (EUROpean research programme for TRANSmutation of high level nuclear waste in an accelerator driven system) are in continuity with the PDS-XADS project objectives, but with a significant change for what concerns the final goal in terms of demonstration level. In fact they are oriented to both the design of an industrial-scale transmuter (EFIT) and a small experiment facility (XT-ADS), serving as a test bench for as much component technologies as possible in a realistic irradiation environmentThe paper describes the main results of the design activities for the large and small LBE-cooled cores performed within PDS-XADS and discusses the constraints (e.g. those deriving from the spallation target and the accelerator), the requirements (such as the degree of subcriticality when operating at power as well as during refuelling), the design criteria and choices with the purpose to verify their applicability to new designs (EFIT, XT-ADS).

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The pressurized light water cooled, medium power (1000 MWt) IRIS (International Reactor Innovative and Secure) reactor plant has been under development for three years by an international consortium of over 20 organizations from nine countries. The plant conceptual design was completed in 2001 and the preliminary design is currently underway. The pre-application licensing process with NRC started in October 2002 and IRIS is one of the designs considered by US utilities as part of the ESP (Early Site Permit) process. Major characteristics of the IRIS design and supporting analyses have been previously reported. This paper focuses on the status of the design and licensing process. IRIS is a pressurized water reactor that utilizes an integral reactor coolant system layout. The IRIS reactor vessel houses not only the nuclear fuel and control rods, but also all the major reactor coolant system components including: eight, small, spool type, reactor coolant pumps ; eight, modular, helical coil, once through steam generators ; a steel reflector which surrounds the core to improve neutron economy and reduce the neutron fluence on the vessel ; and, a pressurizer located in the reactor vessel upper head. The design of the reactor internals is also quite different from typical loop reactors, since all the reactor coolant system components are located in the pressure vessel. Also because of this fact, the IRIS integral vessel is larger than a traditional RV, with an ID of 6.21 meters and an overall height of 21.3 meters including the closure head. However, the large integral RV enables the size of the IRIS containment to be a fraction of the size of corresponding loop reactors. This compact containment size will enable the IRIS to achieve a significant reduction in the overall size of the reactor plant. IRIS has been primarily focused on achieving a design with innovative safety characteristics. The first line of defense in IRIS is to eliminate event initiators that could convincibly lead to core damage. In IRIS, this concept is implemented through the “ safety by design” approach, which can be simply described as “ design the plant in such a way as to eliminate accidents from occurring, rather than coping with their consequences” . If it is not possible to eliminate certain accidents altogether, then the design inherently reduces their consequences and/or decrease their probability of occurring. The key difference in the IRIS “ safety by design” approach from previous practice is that the integral reactor design is conducive to eliminating accidents, to a degree impossible in conventional loop-type reactors. The elimination of the large LOCAs, since no large primary penetrations of the reactor vessel or large loop piping exist, is only the most easily visible of the safety potential characteristics of integral reactors. Many others are possible, but they must be carefully exploited through an appropriate design that is kept focused on selecting design characteristics that are most amenable to eliminate accident initiating events. The IRIS design builds on the proven technology provided by over 40 years of operating PWR experience, and on the established use of passive safety features pioneered by Westinghouse in the NRC certified AP600 plant design. The use of passive safety systems provides improvements in plant simplification, safety, reliability, and investment protection over conventional plant designs. Because of the safety by design approach, the number and complexity of these passive safety systems and required operator actions are further minimized in IRIS. The net result is a design with significantly reduced complexity and improved operability, and extensive plant simplifications to enhance construction. This paper will describe the accident sequence improvements resulting from the IRIS safety by design approach and the IRIS safety systems, and provide a short overview of the licensing and pre-application activities with the NRC.

The TRADE project, which is part of the European Roadmap towards the development of Accelerator Driven Systems (ADS), foresees the coupling of a 110 MeV, 2 mA proton cyclotron with the core of a 1 MW Triga research reactor. We performed radioprotection studies using two state-of-the-art computer code packages, FLUKA and EA-MC. We concentrated on the calculation of the neutron and particle flux and dose rates during normal operation as well as in the case of several possible accidents, in order to assess the radiation damage and define the design of key components of the facility, such as the beam-line shielding. Both high-energy particle interactions and low-energy neutron transport are treated with a sophisticated method based on a full Monte Carlo simulation, combined with the use of modern nuclear data libraries.

The TRADE project is based on the coupling of, in a sub-critical configuration, of a 115 MeV, 2 mA proton cyclotron with a TRIGA research reactor at the ENEA Casaccia centre (Rome). Detailed radioprotection calculations using the FLUKA and EA-MC Monte Carlo codes were performed during the feasibility study. The study concentrated on dose rates due to beam losses in normal operating conditions and in the calculation of activation in the most sensitive components of the experiment. Results show that a shielding of 1.4 m of barytes concrete around the beam line will be sufficient to maintain the effective doses below the level of 10 Mu Sv/h, provided that the beam losses are at the level of 10 nA/m. The activation level around the beam line and in the water will be negligible, while the spallation target will reach an activation level comparable to the one of a fuel element at maximum burnup.

Surgery of cavernous angiomas is often proposed due to the epileptogenic and hemorrhagic potential of this lesion. Little information is available on the impact of surgical resection on brain metabolism, locally or at a distance from the lesion. Fifteen patients presenting with a cavernoma and epileptic seizures underwent positron emission tomography examinations before and 1 year after surgical resection. We studied the quantitative cerebral metabolic rate of glucose (CMRGlu) with [18F]-fluorodeoxyglucose. The global brain CMRGlu remained unchanged after surgery. There was a significant decrease of metabolism in the lesion hemisphere, which remained unchanged after surgery. The perilesional regions were less metabolic than the contralateral ones and less metabolic than remote regions within the same hemisphere, before and after surgery. The absence of pre- to postsurgical variations suggests that the metabolic consequences of the lesion are maintained despite the surgical procedure during long-term follow-up studies.

In vivo studies of ligand-receptor interactions with PET data are based on different approaches that provide either quantitative results (receptor density and affinity) or indices that are assumed to be correlated with the receptor concentration. The aims of this study are to obtain parametric images of benzodiazepine receptor concentration and of flumazenil affinity and to study the validity of two receptor concentration indexes.A three-compartment ligand-receptor model, [11C]flumazenil, and experimental data obtained using a three-injection protocol in human volunteers were used to acquire parametric images. The delayed activity method and the apparent distribution volume (estimated using a two-compartment model) were also tested and their results compared with those of the multi-injection approach.Parametric images of receptor density, affinity and all kinetic parameters were obtained with acceptable variation coefficients. A correlation between receptor density and apparent affinity was found (r = 0.83; p0.0005). The correlation between receptor concentration and apparent distribution volume (estimated with three- and two-compartment models, respectively) was accessed using both a linear (the usual hypothesis) and a nonlinear correlation derived from the relationship between the receptor density and the affinity.In spite of the complexity of this protocol (three injections, a 2-hr experiment, blood sampling and a metabolite study), we showed that the multi-injection approach is suitable for parametric brain imaging. By using this approach as a reference, we deduced that the distribution volume and delayed activity images are valid methods in the usual range of the benzodiazepine receptor concentrations found in the human brain.

The authors report 3 cases of slowly progressive aphasia with different language disturbances: anomia, pure word deafness and Broca's aphasia. All patients were independent in daily life activities. Insight, judgement and overall behaviour were intact. There was no major disturbance of other cognitive functions, but psychometric tests showed mild deficits suggesting widespread involvement. CT scans and magnetic resonance imaging showed focal dilatation of the left sylvian fissure. A positron emission tomographic study showed left perisylvian hypometabolism. A review of the literature yielded an increasing number of cases of this degenerative syndrome affecting dominant hemisphere language areas. Our cases confirm the clinical heterogeneity of degenerative aphasia. Postmortem neuropathological examinations are rare and many causes are found: Pick's disease, Alzheimer's disease or aspecific gliosis.

To compare the merits of 123I-isopropyl-iodoamphetamine (123I-IMP) and 99mTc-HMPAO in showing abnormal brain uptake distribution during cerebral ischemia, we studied ten patients during the subacute phase of their stroke, a period where metabolism and blood flow are frequently uncoupled. SPECT imaging was performed using both radiopharmaceuticals in the 10 patients from 48 h to 4 weeks after onset of symptoms. Two patients out of the 10 had similar defects with 123I-IMP and 99mTc-HMPAO SPECT, the location of the defects corresponding to the area of infarction observed on CT. Six patients had normal 99mTc-HMPAO SPECT and abnormal 123I-IMP SPECT with defects in the area of infarction shown by CT. The remaining 2 patients had hyperactive abnormalities on 99mTc-HMPAO in areas corresponding to defects on the 123I-IMP images. Two of the patients with SPECT mismatches were studied again more than 1 month after onset. On reexamination, 99mTc-HMPAO SPECT which was previously normal or hyperactive became hypoactive with a focal area of decreased activity corresponding to the defect on 123I-IMP. Crossed cerebellar diaschisis was found in 7 patients with 99mTc-HMPAO and was absent for both 123I-IMP and 99mTc-HMPAO in 3. We suggest that SPECT with 99mTc-HMPAO could show transient hyperemia not demonstrated by 123I-IMP whereas in some cases cerebral infarction would be more difficult to demonstrate with 99mTc-HMPAO than with 123I-IMP. SPECT with both tracers is recommended to follow the evolution of strokes in terms of regional cerebral blood flow and tissue metabolism.