Results 1 - 10 of 2041
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[en] The St. Lawrence Estuary, Eastern Canada, contains a very thick (>450 m) Quaternary sedimentary sequence. The results from recently conducted geophysical surveys in conjunction with piston coring indicate that these sediments were deposited under very high sedimentation rates, sometimes as high as ∼30 m/ka during the last deglaciation. Results also reveal evidence of large submarine landslides during the Holocene, changes in sedimentation rates and the significant role of submarine canyons and channels to transfer sediments from the coast to the deeper marine environment. Finally, this paper highlights the presence of more than 1900 pockmarks on the seafloor of the St. Lawrence Estuary and discusses their possible origins: active hydrocarbon seeps in the Laurentian Channel and biogenic gas seepage on the northwestern shoulder of the Laurentian Channel.
[en] This paper examines the results from the post-defueling radiation inspections of decommissioned 1950's vintage Soviet nuclear submarines. Exposed gamma doses from various areas of the reactor comprtment are presented, and lessons learned for future decommissioning activities are discussed
[en] The French assistance programme for removal of legacy spent nuclear fuel (SNF) from Gremikha, a former Russian Navy base, as of 2012. • Handling and removal of standard VVR submarine fuel and fuel from Alfa-class submarines. • Creation of infrastructure for SNF management and removal by international partners. • Refurbishment of a hot cell at the Mayak plant for handling damaged SNF canisters.
[en] The effect of the velocity program and duty cycle (StL) on the propulsive efficiency of pulsed-jet propulsion was studied experimentally on a self-propelled, pulsed-jet underwater vehicle, dubbed Robosquid due to the similarity of essential elements of its propulsion system with squid jet propulsion. Robosquid was tested for jet slug length-to-diameter ratios (L/D) in the range 2-6 and StL in the range 0.2-0.6 with jet velocity programs commanded to be triangular or trapezoidal. Digital particle image velocimetry was used for measuring the impulse and energy of jet pulses to calculate the pulsed-jet propulsive efficiency and compare it with an equivalent steady jet system. Robosquid's Reynolds number (Re) based on average vehicle velocity and vehicle diameter ranged between 1300 and 2700 for the conditions tested. The results indicated better propulsive efficiency of the trapezoidal velocity program (up to 20% higher) compared to the triangular velocity program. Also, an increase in the ratio of the pulsed-jet propulsive efficiency to the equivalent steady jet propulsive efficiency (ηP/ηP,ss) was observed as StL increased and L/D decreased. For cases of short L/D and high StL, ηP/ηP,ss was found to be as high as 1.2, indicating better performance of pulsed jets. This result demonstrates a case where propulsion using essential elements of a biological locomotion system can outperform the traditional mechanical system equivalent in terms of efficiency. It was also found that changes in StL had a proportionately larger effect on propulsive efficiency compared to changes in L/D. A simple model is presented to explain the results in terms of the contribution of over-pressure at the nozzle exit plane associated with the formation of vortex rings with each jet pulse.
[en] In submarines construction, provided that metallurgic characteristics have been established, the NDT methods and equipments as well as the application ways should be taken into account. It is then fundamental purpose of this work to emphasize all that coming from conventional context in the field of use of already known nondestructive techniques
[en] Three papers are presented from a mini-symposium on the issue of nuclear submarines for Australia. The first by Admiral A.J. Robertson discusses the operational attributes of both modern conventional diesel-powered and nuclear-powered vessels. The second by Commander N.S. Stewart discusses technical aspects of nuclear submarines. The third paper by John Grover argues for the French Navy's 2400 T RUBIS class submarine
[en] Specific features of a reactor for a submarine designed for performing researches and pipe laying in high arctic latitudes are described in short. Application of low-enriched uranium, the presence of a high negative reactivity coefficient as well as a special design geometry make the reactor safe
[en] Document available in abstract form only. Full text of publication follows: In the framework of the G8 Global Partnership the French Commission on Atomic Energy (CEA) is in charge of the French funded projects aimed to secure the materials susceptible to be a subject of the proliferation or a malicious use. The securing of the Spent Nuclear Fuel (SNF) from the former soviet submarines is of a special importance for CEA and the Russian Rosatom. Our main bilateral project has focused on two kinds of the SNF (alpha cores and VVR assemblies) stored at Gremikha, the former submarine base in the North-West of Russia. As of 2011 a significant results have been achieved: 2/3 of VVR type assemblies have been removed from Gremikha and reprocessed at PO Mayak. Nine alpha cores are unloaded and stored on at Gremikha. The main task now is to prepare the removal from Gremikha of all the remaining SNF and also to set up the needed infrastructure at the sites where this SNF will be moved. Substantial funding and technical assistance both from France and Russia will be required for that. Beyond the operator of the Gremikha site (SevRAO), the CEA and Rosatom involve many expert organizations from both countries such as AREVA, Kurchatov Institute and many others. Their contribution is one of the key elements of the success. (authors)
[en] Following the '911' attack on the USA in 2001 the international community under Canada's G8 leadership established a $20 billion Global Partnership initiative in 2002 to collaboratively address threats to global security posed by the proliferation and potential terrorist use of Weapons and Materials of Mass Destruction (WMMD) and related materials and knowledge. This major international initiative addressed four priority areas: (1) Chemical Weapon Destruction (2) Nuclear powered submarine eliminations (3) Nuclear and radiological security; and (4) Employment for former weapon scientists. Additionally the initiative has addressed Biological Non- Proliferation. Canada's execution of all these program areas has resulted in substantial environmental benefits aside from the eradication and securing of WMMD. This paper reviews the environmental and radiological remediation achievements of the four primary Global Partnership program areas addressed under Canadian funding 2004 through 2011. (author)