Internal defence system

Previous results have shown that parasite infection of the snail host affects the neuroendocrine system of the snail in a way that results in reduced reproduction of these snails a phenomenon referred to as parasitic castration (Crews and Yoshino 1989 Sorensen and Minchella, 2001). The Lymnaea stagnalis-Trichobilharzia ocellata host-parasite combination has been the model system adopted for most of these studies (de Jong-Brink et at., 2001). However, comparable studies as to how parasite infection affects the snail s central nervous system (CNS) in releasing neuropeptides and bioamines that modulate snail reproduction and the internal defence system of... 

Fiserova A, Kfen V, Aug C, Sima P, Pospisil M (1995) Ergot alkaloid derivatives with immunomodulatory activities. Proceedings of the International Conference on Experimental, Therapeutic and Toxic Manipulations of Host Defence Systems. June 12-15,1995 Hradec Krtllove, Czech Rep. p 67... 

Goodman TD (ed) (2005) Advancements in polymer optics design, fabrication and materials. SPIE (The International Society for Optical Engineering), San Diego, California, USA Grote JG (eds) (2006) Optical materials in defence systems technology IB. Stockholm, Sweden, 13-14 Sept 2006 (sponsored by SPIE Europe published by SPIE - The International Society... 

CAA (2003) CAP670 Air traffic services safety requirements. Civil Aviation Authority Cullen (1990) The public inquiry into the Piper Alpha disaster. HM Stationery Office, London Haddon-Cave C (2009) The Nimrod review. The Stationery Office, London lEC (2002) lEC 61508 Functional safety of electrical/electronic/programmable electronic safety-related systems. Part 1. International Electrotechnical Commission Kuhn TS (1962) The structure of scientific revolutions. University of Chicago Press MoD (2007) Defence standard 00-56 Issue 4. Safety management requirements for defence systems part 1 requirements part 2 guidance on establishing a means of complying with part 1. Ministry of Defence... 

Economics and politics also intersected in Whitehall s perception in 1956 of the Soviet Union as a threat to Britain s share of international trade. In May of that year, when arguing that Britain could not afford a policy of perfection in defence, Eden noted that there was evidence that the Russians intended to concentrate on industrial exports. In order to be able to meet this competition, part of the burden placed on British industry by defence orders must be reduced, so as to release resources for civil production. In present circumstances, he said, economic failure was a more serious risk than global war, and defence plans had to be adjusted to this revised political assessment. He added that a recent report from the ambassador in Washington showed that President Eisenhower was thinking along the same lines.The Russians made no secret of their intentions. In November 1957 Nikita Khrushchev, the Soviet leader, declared in a visit to the United States in the peaceful field of trade we declare a war. The threat to the United States is not in the intercontinental ballistic missile but in the field of peaceful production. We are relentless in this and will prove the superiority of our system. ... 

Could be worse." Samuel tried his beer, and frowned at the bottle with some dismay. "Take me. I m supposed to be part of the delegation from this system s Edenist habitats, discussing mutual defence enhancement arrangements. I specialize in internal security procedures."... 

The complete adoption of the Defence in Depth principle has to be noted in its more evolved version, which includes five superimposed levels of defenee, concisely summarized as follows good design, good control, adequate emergency systems, accident management (various levels of seriousness eonsidered), internal and external emergeney plans. 

International practice considers the analysis of ATWS for a variety of initiating events such as loss of feedwater, loss of load, turbine trip, loss of condenser vacuum, loss of off-site power, closure of main steamline isolation valves, uncontrolled boron dilution, inadvertent control rod withdrawal, etc. ATWS analyses are performed in general by using best-estimate tools to determine the preventive (e.g. a diverse scram system) or mitigative measures (e.g. initiation of turbine trip and emergency feedwater supply) which need to be implemented for strengthening plants defence in depth. 

No safety requirements are made on fire suppression systems or operator actions in the event of a fire these serve to provide defence in depth and have been identified in the Internal Hazards Topic Report. 

This method allows balance and optimization of the reactor and the safety system at an early engineering stage, to cost-efficiently internalize safety issues based on the defence in depth approach and considering appropriate conservative assumptions and safety margins. This achieves a balance between inherent capability of the reactor and the safety systems to cope with the postulated initiating events. 

A relevant aspect of the implementation of defence in depth is the provision in the design of a series of physical barriers to confine the radioactive material at specified locations. The number of physical barriers that will be necessary will depend on the potential internal and external hazards, and the potential consequences of failures. The barriers may, typically for water cooled reactors, be in the form of the fuel matrix, the fuel cladding, the reactor coolant system pressure boundary and the contaimnent. 

Step 2 The safety classification of structures, systems and components reflects the internal postulated events and external events as set forth in the safety analysis of the plant (box (3) of Fig. 1). The definition of the defence in depth levels and barriers [2], the application of the single failure criterion and the assessment of the potential for common cause failures are identified in box (2) of Fig. 1 [19], bearing in mind the categorization of the facility. Next is the evaluation of the need for emergency procedures, both on and off the site. This is followed by identification of the internal events to be considered as a consequence of an external event or as contemporaneous to an external event, and therefore of the safety functions to be maintained in case of an external event (e.g. cooling of radioactive material, reactivity control, confinement). 

Analysing the existing defence in depth system for VVER-440 reactors from a materials point of view and improving it based on national and international experience and trends ... 

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