Structural restraints

Restraints due to artifacts may, by chance, be completely consistent with the correct structure of the molecule. However, the majority of incorrect restraints will be inconsistent with the correct structural data (i.e., the correct restraints and information from the force field). Inconsistencies in the data produce distortions in the structure and violations in some restraints. Structural consistency is often taken as the final criterion to identify problematic restraints. It is, for example, the central idea in the bound-smoothing part of distance geometry algorithms, and it is intimately related to the way distance data are usually specified The error bounds are set wide enough that all data are geometrically consistent. 

Using 18 trNOE-derived distance restraints and 13 trCCR-derived backbone torsion angle restraints, structure calculations using distance geometry and simulated annealing [48] resulted in a well-defined structure of the IKK/1-derived peptide bound to NEMO. The backbone structure is displayed in Fig. 7B and is compared with the result of the calculation carried out using the trNOE-derived distance restraints alone. It is obvious from Eig. 7 that only the combination of the trNOE- and trCCR-derived restraints results in the structure elucidation of the bound conformation of this peptide. 

The scope of the reactor core analysis includes the fuel elements, plenum elements, inner and outer reflector elements, peraanent side reflector, core support posts, core metallic support structure and core barrel lateral restraint structure. 

Core Lateral Restraint Structure - Elevation View Core Lateral Restraint Structure - Plan View Metallic Core Support Structure... 

Monitoring of core power level during power operation is provided by ex-vessel neutron flux detectors. Flux monitoring at lower powers and at shutdown conditions is provided by source range detectors which are located in the side reflector. The reactor core and reflectors rest vertically on a support structure below the core and are restrained by a core lateral restraint structure located between the outer side reflector and the reactor vessel. 

Around the outside of the hexagonal replaceable side reflector is a permanent side reflector which provides a transition from the core periphery to a cylindrical outer boundary. Interfacing of the graphite reflector with the reactor vessel is provided by a core lateral restraint structure which is composed of a core barrel and seismic keys. 

The Reactor Core Subsystem (RCSS) consists of fuel elements, hexagonal graphite reflector elements, plenum elements, startup sources, and reactivity control material, all located inside a reactor pressure vessel. The RCSS, together with graphite components of the Reactor Internals Subsystem, constitutes a graphite assembly which is supported on a graphite support structure and restrained by a core lateral restraint structure. (See Figures 4.1-1 and 4.1-2). 

The core lateral restraint structure is composed of metal components consisting of a core barrel, seismic keys, coolant channels, and boss located between the PSR and the reactor vessel as shown in Figures 4.4-11 and 4.4-12. The core barrel is a cylinder composed of approximately 76 mm (3 in.) thick steel to locate, restrain, and limit the motion of the core outer radial boundary. It is attached to the top plate of the core support structure. 

The permanent side reflector (PSR), in conjunction with the core barrel, protects the reactor vessel and the core lateral restraint structure from excessive neutron fluence. 

For DBE-5, the earthquake design spectrtam load for the core lateral restraint structures was estimated as approximately 0.5 g. The value is based on a very stiff core barrel and key support design yielding a natural frequency of about 25 Hz. The lateral restraints must also accomodate the loads caused by lateral impact of the core against the core barrel. Overall, the design shows barrel/key interface stresses well below the material strength. Consequently, the core barrel will prevent excessive core deflections and will ensure that control rod reserve shutdown materials are capable of being inserted into the core when required. 

CORE LATERAL RESTRAINT STRUCTURE - ELEVATION VIEW... 

The core restraint structure was not strong enough to withstand a channel tube failure... 

In the early life of these reactors in-service inspection revealed higher than expected steel oxidation rates in the high temperature regions of the primary coolant circuit. Oxidation damage to the core restraint structure could have led to the partial disruption of... 

Visual inspection provided enough information for most purposes with the main exception of the core restraint structure and this accounts for the majority of in service inspection work at Hunterston A. ... 

The main restraint comprises a framework at each core facet vhich is hinged at the base and vhich applies forces to core restraint beams at each brick layer joint by means of universal links vhich accommodate vertical and circumferential differential expansions. Each core facet restraint structure is linked to its nei bour at two levels by T.C.U. s (tenperature compensating units). 

Inside the gas baffle 24 vertical routes are provided which permit viewing of the annulus containing the core restraint structure between the core restraint tank and the outer parts of the graphite core. 

On a large number of routes, for example in the boiler annulus or through the core restraint structure, the camera is deployed vertically downwards by paying out the hose through the links from a hose drum in the main containment ... 

Closed circuit television equipment is used for general surveillance and for the examination of core restraint structures. Normally 2/3" newvicon cameras are used but for increased sensitivity 1" cameras can be employed. The cameras are modified on-site to be gas-cooled and to permit manipulations between the core and the pressure vessel. All the reactors are surveyed during their annual refuelling outages and no noticeable lens darkening has been encountered even after several hours continuous operation. 

The ACL is also the restraint structure to internal and/or valgus tibial moments. The ACL force in response to 10 Nm of internal moment applied to the tibia is approximately 70 N at full extension and decreases at flexion angles more... 

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