Deterministic and probabilistic assessment

Deterministic and Probabilistic Assessment Factors Suggested for Use in Human Health Risk Assessment... 

Kralik, J. Kralik, J., jn 2007. Deterministic and Probabilistic Assessment of Reliability Design of the High Rise Buildings. Civil and Environmental Engineering, ZU Zilina, ISSN 1336-5835, 2007, Vol. 3, N.l, p. 12-27. 

The determination of the estimated levels of exposure is obviously a critical component of the risk assessment process. Both pesticide residue levels and food consumption estimates must be considered. Methods for determining exposure are frequently classified as deterministic and probabilistic methods (Winter, 2003). 

Methods available for analysing uncertainties fall into three broad types qualitative, deterministic and probabilistic. They provide contrasting ways of characterizing the relative importance of the uncertainties affecting an assessment and of characterizing the overall uncertainty of the assessment output, and they provide an essential input for decision-making. 

It is essential to provide decision-makers with an assessment of the overall degree of uncertainty in the assessment outcome. Therefore, if the uncertainties for an assessment have been analysed at different tiers (qualitatively, deterministically and probabilistically), it is necessary to find a way of presenting the results together and arriving at an overall characterization of exposure. This is difficult and subjective but unavoidable, since it is never possible to quantify all uncertainties objectively. Few assessments have attempted to do this in a systematic way, and it would be premature to give firm recommendations. However, a combined presentation should include ... 

Lawson K (2005). Pipeline corrosion risk analysis—an assessment of deterministic and probabilistic methods. Anti-Corrosion Methods and Materials, vol. 52, pp. 3-10. 

Krinitzsky, E. L. (2003). How to combine deterministic and probabilistic methods for assessing earthquake hazards. Engineering Geology, 70, 157-163. doi 10.1016/S0013-7952(02)00269-7... 

Application of the above principles and solutions in practice have come across with a problem of uncertainty with respect to achievable efficiency the latter is connected with necessity of quantification of the safety level. To evaluate and assess the achievable safety level, one has to perform the full-scale PSA in addition to deterministic principles. Common realisation of the deterministic and probabilistic analyses during the NVAES-2 design process has permitted to obtain optimal solution with respect to balance of the active and passive trains of the modular safety systems. As a result of this optimisation, total core melt frequency for NVAES-2 is about three orders of magnitude less than for unit 1 of Balakovo NPP with V-320 reactor plant. 

Both deterministic and probabilistic fracture mechanics methodologies are being development for the integrity assessment of flawed or cracked structure. 

Where appropriate, the review of each of the safety factors should be carried out for aU service conditions (including acddent conditions), using current deterministic and probabilistic methods and an assessment made against current safety standards and practices. A list of shortcomings should be prepared, showing areas where current standards and practices are not achieved. In addition, areas where current safety standards and practices are exceeded should be identified as plant strengths. 

SESSION II Risk Theory and Risk Analysis for Landslides. [1] Landslide Risk Management concepts and framework and examples (2.5 h) [2] Deterministic and Probabilistic models for slope stability evaluation (2 h) [3] Introduction to modelling of catastrophic landslide events (2 h) [4] Empirical models for travel distance (1.5 h) [5] Application examples of probabilistic methods and semi quantitative methods for landslide hazard zonation (2h) [6] Landslide Frequency Assessment (1.5 h) [7] Different components of vulnerability to landslides. Prevention and long term management of landslides (3.5 h) [8] Case Studies coal waste dump risk assessment, example from motorway in La Reunion Island, Aknes Rock slope in Norway (2 h) [9] Application of QRA to other geotechnical problems Internal erosion of dams, crater lake hazard (1.5 h) [10] Advanced numerical models initiation of landslides, propagation of sediments/climate change effects (3.5 h). 

The biological consequences of irradiation arc currently studied under two headings deterministic and probabilistic In the thyroid the main deterministic effect is hypothyroidism, which in practice only occurs after relatively large doses of lO s to lOO s of Grays. The incidence of radiation induced hypothyroidism is well known after radioiodine therapy, and shows a linear dose - effect relationship There is almost certainly a threshold dose beneath which no hypothyroidism occurs. However the size of the threshold depends on the radiation type and the time post irradiation plus the criteria used in the assessment of hypothyroidism. In one study it has been estimated that 50 Gy is required to induce hypothyroidism in 50 per cent of those exposed (Table l) In practice injestion of the order of 100 MBq of l, or... 

Estimating fault displacement is a key issue to design tunnels crossing active faults. One option to estimate fault displacement is using empirical relationships that express expected displacements in terms of some source parameter. Deterministic and probabilistic fault displacement hazard analyses can be used to assess fault displacement hazard where a displacement attenuation function is used in a probabilistic seismic hazard analysis (Coppersmith and Youngs 2000 Youngs et al. 2003). 

Both deterministic and probabilistic approaches are important and useful for clarifying the safety characteristics of new reactors concepts. In this section, simplified level-1 PSA (probabilistic safety assessment) of the Super LWR is introduced. Information from preliminary PSA studies on the SCWR [21, 33] and PSA documents for US LWRs [34-37] and for Japanese LWRs [38-41] is mainly referred to in this section. 

For example, existing databases and risk assessment publications often omit statistical measnres of variability or nncertainty and sample sizes and rarely report the underlying data. These types of information are rarely used in deterministic assessments but are a fundamental reqnirement for probabilistic assessments. 

The analysis plan should specify not only how the analysis will be conducted, but also how the results will be presented. Indeed, the way results will be communicated will usually influence the choice of both model structure and analysis method and is ultimately driven by the information needs of risk managers and other stakeholders and their management goals (see Figure 2.2). Careful advance planning for the communication of results is especially important for probabilistic assessments because they are more complex than deterministic assessments and less familiar to most audiences. It may be beneficial to present probabilistic and deterministic assessments together, to facilitate familiarization with the newer approaches. 

Defining the characteristics of each level of refinement of the risk assessment and identifying which levels are deterministic and which are probabilistic... 

Irrespective of the risk, assumptions and decisions will have to be made because of uncertainty. Implications of attempting to characterize all variability and uncertainty in the risk assessment need to be considered. For example, exaggerating uncertainties can obscure the scientific basis of risk management decisions, leaving the impression that the decision has been arbitrary in nature (NRC 1989). The purpose of the uncertainty factor together with the type of assessment (e.g., deterministic or probabilistic, protective or best estimate) must be clearly communicated. Uncertainty factors can be described in 3 categories ... 

Given the tiered system, evidently, any step in the exposure and effects assessment can be considered in a deterministic or probabilistic way. This does affect the outcomes of the risk assessment, but it does not influence the choice of extrapolation methods as guided by the decision tree itself. 

First, individuals interpreting data must decide on whether to use a deterministic or a probabilistic approach to generate an exposure estimate for the analysis. The deterministic approach (point-estimate) is widespread and beginning with this approach is consistent with the tiered approach to exposure and risk assessment. 

Guidance for selecting an appropriate mathematical approach for a given exposure scenario (deterministic versus probabilistic) and guidance regarding conduct of acceptable probabilistic assessments. 

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