Design Basis Analysis

Documentation of system design basis, analysis of accident scenarios, prediction of overall risk to society. 

The plant conditions considered in the design basis analysis include anticipated operational occurrences and design basis accidents (DBAs). The division is based on the frequency of the occurrence. 

The aim of the design basis analysis should be to provide a robust demonstration of the fault tolerance of the engineering design and the effectiveness of the safety systems. This is done by carrying out a conservative analysis which should take account of the uncertainties in the modelling. 

The conservative assumptions made for the design basis analysis should typically include the following ... 

The design basis analysis should include any failures which could occur as a consequence of the initiating event (and are thus part of the PIE). These include the following ... 

In view of the very conservative nature of these assumptions, the design basis analysis often provides a robust demonstration that there are large margins before safety limits would be exceeded. However, caution is necessary in using the analysis, as this outcome is not always the case. 

For each of the PIEs identified, the safety functions that need to be performed to prevent core damage should be identified. These safety functions are the same as those addressed in the design basis analysis — that is, detection of the initiating event, reactor shutdown, residual heat removal and containment protection. However, the limits above which the safety function would be considered to have failed would be realistic limits rather than the conservative limits defined for the design basis analysis. 

SAFETY SYSTEM TESTED IN ALL CONDITIONS REQUIRED BY DESIGN BASIS ANALYSIS... 

A unique aspect resulting from the application of the Siting Guide is that the design basis analysis has included a class of events called dual failures. A dual failure is defined as the simultaneous failure of a process system and the unavailability of a safety system or subsystem. Safety analysis is therefore performed for the failure of each process system in the plant then for each such failure combined with the unavailability or impairment of each relevant safety system or subsystem in turn. Examples of major impairments are... 

The Design Basis Analysis (DBA) of the faults in the fault sehedule is then described in subsection 5.3. The DBA aims to demonstrate, through thermal-hydraulie and radiological analysis of bounding fault sequences, the efifeetiveness of the proteetion identified for each of the faults in the fault schedule. 

The review described above provides confidence that the AP1000 is tolerant of faults associated with shutdown operations is acceptable. However, it is UK good practice to perform a robust shutdown fault identification exercise, with the identified faults included in the fault schedule and analysed using Design Basis analysis techniques. This fault identification and analysis will be undertaken during Step 4 of the GDA. 

An important part of hazard analysis and risk assessment is the identification of the scenario, or design basis by which hazards result in accidents. Hazards are constandy present in any chemical faciUty. It is the scenario, or sequence of initiating and propagating events, which makes the hazard result in an accident. Many accidents have been the result of an improper identification of the scenario. 

The Pickering A Risk Assessment (PARA) (Ontario Hydro, 1995) is also a level 3 PSA for 1 of the 4 units at Pickering. A difference between PARA and DPSE is that sequences beyond the design basis were modeled using the MAAP-CANDU codes with best estimate assumptions. Other parts of the analysis used licensing-type conservative assumptions. 

In Table III are shown values of p, p, X, n, SD, / and Hammett p values obtained for additional para BA type reaction series which contain data for sufficient numbers ( ) and kinds of substituents to provide a reasonably critical analysis. We do not believe, however, that the analysis is as critical for sets which do not meet the minimal requirements for a basis set. The reaction series are segregated according to type of measurement equilibrium, rate, and fluorine nmr (F-nmr) shift. Any data set in Table III and in all tables hereafter (other than designated basis sets) which meets our minimal basis set criterion is indicated by an asterisk. 

Regulatory status In 1998, Lopez Canyon Sanitary Landfill received conditional approval for an ET cover, which required a minimum of 2 years of field performance data to validate the model used for the design. An analysis was conducted and provided the basis for final regulatory approval of the ET cover. The cover was fully approved in October 2002 by the California Regional Water Quality Control Board—Los Angeles Region. 

Consequence assessment for the purposes of establishing design basis differs from consequence assessment in the context of a risk analysis study (see Qualitative and Quantitative Methods, below). A qualitative, or semi-quantitative (order of magnitude) consequence severity estimate may suffice for the latter. 

By contrast, the nature of certain accident scenarios could prove to be quite sensitive to some design parameters. It should not be ruled out during the risk assessment phase, especially during detailed design, that discoveries during consequence analysis could lead to the revision of the design basis of the facility or some equipment or components. 

The anticipated product slate from a typical commercial plant feeding 33,500 tons per stream day of dry coal is given in Table II. This product slate is based on conversion of a typical Pittsburgh seam coal from West Virginia. The ultimate analysis of the coal used as a design basis is given in Table III. 

It would be quite appropriate to draw here an analogy with the generally accepted approach to safety assessment of nuclear power plants where, along with the probabilistic safety analysis, each NPP is calculated for the maximum possible (i.e. beyond the design basis) accident in order to obtain as conservative assessment as possible. 

Calculation results of radiation factors analysis show that maximum annual effective radiation dose for population in case of the design-basis accident during Victor II dismantling will not exceed 0.1 mSv. It is considerably less than dose limit for population under normal operational conditions given in Radiation Safety Standards (NRB -99). 

Application of statistical analysis in process design has beeome so extensive that every chemical engineer must have a basie knowledge of this branch of mathematics. Statistical design and analysis help the engineer to make decisions by getting the most out of the data. In many eases, where too little is known about a chemical process to permit a mathematieal model, a statistical approach may indicate the manner of the direction in which to proceed with the design. 

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