[en] Full text: A series of crystalline compounds, [M(m-TUP)4(H₂₀)zJS04_2H20 (M = Co, Ni, Zn; m-TUP = N-(4-tolyl) (3-pyridyl)urea) display interesting solid-state structures containing a highly unusual water tetramer. These result from a high degree of hydrogen bonding, both within the cavities and between parallel chains via the sulphate counter-anions. Neutron Laue diffraction data has provided high precision, low temperature structures of the cobalt complex, showing the ordering of the water tetramer that occurs as the sample is slowly cooled. The hydrogen bonding involving the solvent molecules is seen to play a more pronounced role at low temperature, pulling together two sides of the [M(m-TUP)4 (H₂₀)²+ complex. Non-empirical calculations reveal details of the strength of the hydrogen-bonding compared to a 'free' tetrameric water cluster and account for the observed distortion of the octahedral metal coordination geometry.

[en] The causes of the drop in the hitherto good performance figures for CANDU reactors since the late 1980s are discussed. Units in India and Pakistan whose design has evolved separately since the mid 1970s are not considered. The discussion is focussed on the reactors operating at Ontario Hydro's power stations (Pickering and Bruce) which account for over 85% of CANDU installed capacity in Canada, Argentina and Korea. Two major contributors to reactor incapacity are identified; these are fuel channels and steam generators. Retubing the fuel channels at the four Pickering A units has resulted in 13 years of collective downtimes earlier than expected in the lifetime of the reactors. The units are now operating at their former high performance level and improved technology used in the retubing should ensure that the pressure tubes achieve their design lifetime. Leaks in steam generator tubes due to corrosion have significantly affected performance at the Bruce A reactors, and to a lesser extent at one of the Pickering B reactors. Operational changes have been put in place to remedy this problem both at Ontario Hydro and other CANDU utilities. (2 figures, 1 table) (UK)

[en] Presently there are 31 Pressurized Heavy Water Reactors, based on the CANDU design, operating throughout the world. This paper reviews the lifetime performance of these CANDUs, ranging from the oldest Pickering NGS-A, RAPS and KANUPP units which went into service in the early 1970's, the newest Darlington units of which the last one reached full power in May of this year. While some units suffered from initial technical problems and others have been affected by grid limitations, in general CANDUs have been successful in achieving high capacity factors during their early years of operation. However, the pressure tube failure of Pickering 2 in August 1983 revealed the potential for a much shorter tube life than originally expected, and the resulting need for lengthy outages at mid-life to retube the reactor. To date, the pressure tube problem, and more recent steam generator problems, have resulted in reduced capability for the Ontario Hydro 'A' units. However, it is expected that the knowledge and experience gained will reduce the future impact of these problems on other reactors in the CANDU family. (author). 3 figs, 5 tabs

[en] This paper describes the process of retrieving, repackaging, and preparing Oak Ridge spent nuclear fuel (SNF) for off-site disposition. The objective of the Oak Ridge SNF Project is to safely, reliably, and efficiently manage SNF that is stored on the Oak Ridge Reservation until it can be shipped off-site. The project required development of several unique processes and the design and fabrication of special equipment to enable the successful retrieval, transfer, and repackaging of Oak Ridge SNF. SNF was retrieved and transferred to a hot cell for repackaging. After retrieval of SNF packages, the storage positions were decontaminated and stainless steel liners were installed to resolve the vulnerability of water infiltration. Each repackaged SNF canister has been transferred from the hot cell back to dry storage until off-site shipments can be made. Three shipments of aluminum-clad SNF were made to the Savannah River Site (SRS), and five shipments of non-aluminum-clad SNF are planned to the Idaho National Engineering and Environmental Laboratory (INEEL). Through the integrated cooperation of several organizations including the U.S. Department of Energy (DOE), Bechtel Jacobs Company LLC (BJC), Oak Ridge National Laboratory (ORNL), and various subcontractors, preparations for the disposition of SNF in Oak Ridge have been performed in a safe and successful manner

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No abstract available

[en] The reactions of Pb(OAc)2 with 1, 2,4, 5-benzenetetrathiol, 1, 4-benzenedithiol, and benzenehexathiol in ethylenediamine yield bright yellow [Pb2(S2C6H2S2)(en)]n, orange-red [Pb3(SC6H4S)3(en)2]n, and brown [Pb3C6S6]n, respectively. The structures of [Pb2(S2C6H2S2)(en)]n and [Pb3C6S6]n were solved by synchrotron X-ray powder diffraction, while the structure of [Pb3(SC6H4S)3(en)2]n was solved by single-crystal X-ray diffraction. The bonding in [Pb2(S2C6H2S2)(en)]n indicates the presence of 'molecular' units, while in [Pb3C6S6]n, the bonding most resembles that in an inorganic solid such as PbS. The differences in bonding are reflected in the optical and electrical properties of the materials; [Pb3C6S6]n is a semiconductor.

[en] Meeting quarterly, members of project teams from major DOE sites continue to demonstrate that there are savings through sharing. Out of a need for better understanding of projects of similar nature and to achieve the national DOE mission to design and build facilities for retrieval,characterization, packaging, storage and transportation of TRU solid waste, this paper reviews the history of this open-quotes intersiteclose quotes working group and explores the benefits of open communication between sites, DOE National program personnel, and DOE TRU steering committee members

[en] Short communication

[en] The existing ISIS Penning H"− source is unable to produce the beam parameters required for the front end test stand and so a new, high duty factor, high brightness scaled source is being developed. This paper details first the development of an electrically biased aperture plate for the existing ISIS source and second, the design, simulation, and development of a prototype scaled source