Proposed pebble bed modular reactor
Description Of The Proposed Structure
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Description Of The Proposed StructureThis section briefly describes the position and the development characteristics of the proposed Pebble Bed Modular Reactor.
The two alternatives for the proposed Pebble Bed Modular Reactor are not obtrusive, due to the fact that these sites are located adjacent to the existing structures on the site. The two alternative positions for the establishment of the Modular Reactor are discussed below:
The project will entail the construction, commissioning, operation/maintenance and decommissioning of a 110 MWe Class Pebble Bed Modular Reactor demonstration module electricity generating plant. The electricity generation plant will be enclosed in a specially designed/constructed concrete building with the following approximate dimensions; 60 metres long, 40 metres wide and about 60 metres high, of which 24 metres will be above the natural ground level. The demonstration plant will make use of the existing infrastructure of Koeberg Power Station and modifications thereto, with the main components being as follows:
The scale of the proposed building is described in Chapter 2.2.3.
Construction will entail major excavations and dewatering due to the shallow water table. The construction time for the PBMR is approximately 36 months. The proposed time frame for construction is from the year 2004 to 2006. Observation Of The Proposed StructureThis section describes the existing theories with regard to the observation of elements in a landscape by humans. Thereafter the anticipated viewing points and type of observers are evaluated.
i. “GENIUS LOCI” The landscape is usually experienced in a sensory, psychological and sequential sense, in order to provide a feel and image of place (“genius loci”). A landscape is an integrated set of expressions, which responds to different influences. Each has its unique spirit of place, or “genius loci”. Each landscape has a distinct character, which makes an impression in the mind, an image that endures long after the eye has moved to other settings. The visual quality of a coastal landscape is to a large extent the product of the topography, ocean and skyline. The construction and/ or positioning of any structures that could alter the character of the landscape should be carefully designed and located. According to Motloch (1991: p. 54), elements such as landform and topography, vegetation, climate, water, social history, physical location, human activities, the place’s meaning beyond its physical expression due to its historical significance, and the sensory experience, primarily visual, contribute towards the “genius loci” of a place. The loss of spirit of place or “placeless ness” results from an inability to perceive or respond to this spirit as an interactive synthesis of the above elements. ii. SENSORY EXPERIENCE Our perception of the environment encompasses the visual, hearing, smell and tactile senses, together with the psychological experience. The major emphasis in planning and impact assessment is usually on the visual characteristics of the environment. iii. PSYCHOLOGICAL EXPERIENCE According to Laurie (1978, p.155), human psychological and social needs, behavioural patterns and the perception of the environment, differ according to variables such as age, social class, cultural background, past experience, motives and daily routine of the individual.
The inner condition of the individual entails the following factors:
The way, in which the individual perceives the environment, as well as behavioural reactions, should therefore be taken into account with the planning and design of a structure. Another way in which the influence of the environment on behaviour can be seen, is in the way places/ structures assume meaning, e.g. the symbolism of a church or nuclear power station such as Koeberg. This selection and attribution of meaning or symbolism to the environment, or the development of an emotional response to aspects of the environment, will vary according to the individual. This fact makes it difficult to produce universal rules with regard to perceptions and behaviour. What is seen by an individual is usually what he/ she wants to see, or what he/ she is looking for. The perception of the environment depends on the type of social- and economic group, e.g. low-, middle- or high-income groups or tourists. Each person has a visual realm or cone of vision, which is approximately 60 degrees from the point of viewing for an average person with clear vision. This cone is 30 degrees to the left and 30 degrees to the right of the viewer, and 30 degrees above the horizontal. Any element viewed within this cone is observed as part of its surroundings. Furthermore a person with normal 20/20 vision can identify a human form at a distance of approximately 120 metres. A normal person with 20/20 vision can identify a person’s face over a distance of 60 metres. This distance can be considered as the limit of intimate space. Intrusion into this intimate space can be considered to be the greatest visual impact. Jacobs, Maertens and Blumenfeld (1999: p 278) came to the following conclusions, based on their work on physiological optics and experience:
VISUAL DISTANCE THEORY: THE EFFECT ON PERCEPTION OF A VIEWER’S DISTANCE FROM THE OBJECT – KOSTOF (1992: p. 140) For the purpose of this study, distances will be specified in km, due to the fact that most of the viewing points will fall in the category of a height: distance ratio of 1:4 or less. According to the context theory, the average person becomes aware of a structure within his visual realm at the first viewing of the element. Thereafter the awareness fades, until the element is hardly noticed at all. The time period for the person to become accustomed to the structure depends on the following:
The first two categories would eventually hardly notice the structure at all. Incremental development is less easily noticeable to regular passers-by. It would however be clearly noted by first-comers and tourists. iv. SEQUENTIAL EXPERIENCE The landscape is seldom experienced in a static way, but mainly in a kinetic way from foot or from moving cars. This constantly changing scene can be defined as sequential experience.
This section of the report entails the interpretation of data with regard to the above description of the existing landscape, the proposed structure and the observers. i. ANTICIPATED VIEWING POINTS The following viewing points to the proposed alternatives for the modular reactor can be listed:
ii. CATEGORIES OF THE COMMUNITY, ANTICIPATED TO OBSERVE THE PROPOSED STRUCTURE The categories of humans, who are expected to have visual access to the site, are set out in Table 27. (Categories of Observers). Table 27: CATEGORIES OF OBSERVERS
= observers who will be aware of the new development The perceived visual perceptions of observers from the different viewing points are set out in Table 28. Table 28: PERCEPTIONS OF OBSERVERS
= observers who will be aware of the new development If the context theory is applied, tourists will clearly note the proposed structure from these roads. The awareness of regular viewers, who travel on the above roads regularly and at a speed, will become accustomed to the structure with time, until the element blends into the overall picture. The same principle would be applicable for people who work or stay in Duynefontyn, Van Riebeeckstrand, Melkbosstrand and Atlantis, where observation fades with time. According to Bentley (1996: p. 42) users, rather than designers, form images of layout, the designer merely arranges the physical layout itself to achieve legibility. Legibility can be defined as the quality that makes a place graspable, and that enables people to form clear, accurate images of a city/ structure or new entity. Table Mountain and Robbeneiland are of natural-, historical- and cultural significance. These landmarks contribute to the legibility of Cape Town. Researchers have explored the contents of these images, using techniques such as interviews, asking directions to places, and getting people to draw maps from memory. Certain types of physical features play a key role in the content of these shared images. Kevin Lynch, an American planner, grouped these features into five key elements, namely nodes, edges, paths, districts and landmarks. These key physical elements are illustrated below. 
THE KEY PHYSICAL ELEMENTS, WHICH CONSTITUTE THE SKELETON OF THE URBAN IMAGE – BENTLEY (1996: p. 43) The most significant viewing points would be the Koeberg Private Nature Reserve, Table Mountain and Robbeneiland, due to the awareness and category of users, which mainly entails tourists. Table Mountain and Robbeneiland, however, are located at distances of 31 and 15km respectively from the proposed structures, which implies that the proposed reactor will not be seen as an individual element, but becomes part of its surroundings and speaks mainly through its silhouette. The character of the respective viewing points is rated in Table 29. Table 29: CHARACTER OF VIEWING POINTS
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