Summary description of the methods used in the probabilistic risk assessments for NUREG-1150

Breeding, R.J.; Helton, Jon C.; Gorham, Eville; Harper, F.T.

doi:10.1016/0029-5493(92)90300-k

Cited by 92 publications

(48 citation statements)

References 30 publications

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“…In 1989, the WIPP PA analysts adopted the idea of conducting sequential PAs, that is, conducting an initial PA with simple or incomplete models and preliminary data, followed by other PAs with better data and/or more detailed models (Rechard, 1989 (Rasmussen, 1975) and its 1990 update (Breeding et al, 1992). The value of repeating the PA process was that engineers and scientists could gain an understanding about the disposal system and how best to model it and also replace weak links in the simulation chain as improved models and data became available.…”

Section: Iteration Of Calculationsmentioning

confidence: 99%

“…The idea had been used before, e.g., repeated NAS studies of ozone depletion in 1975 through 1982 (Morgan et al, 1990) or the 1975 Reactor Safety Study (Rasmussen, 1975) and its 1990 update (Breeding et al, 1992). The value of repeating the PA process was that engineers and scientists could gain an understanding about the disposal system and how best to model it and also replace weak links in the simulation chain as improved models and data became available.…”

Section: Iteration Of Calculationsmentioning

confidence: 99%

“…By the 1990 PA, analysts had also chosen to emphasize the detailed modeling style. An important reason for using a detailed modeling style was the general acceptance in the United States of its use in PWls (Rasmussen, 1975;Breeding et al, 1992). Also comments received from the EPA (Bertram-Howery et al, 1990) and the WIPP Panel of the NAS on the 1989 PA encouraged Sandia to move from the simplified NEFTRAN (Longsine et al, 1987) models to a more detailed modeling.…”

Section: Detailed Modeling Stylementioning

confidence: 99%

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Historical background on performance assessment for the Waste Isolation Pilot Plant

Rechard

2000

Reliability Engineering & System Safety

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Protection Agency (EPA) certified that the WIPP dkposal system complied with its regulations. The EPA's decision was primarily based on the results from a performance. assessment conducted in 1996, which is summarized in thk special issue of Reliability Engineerhg and System Safety. This performance assessment was the culmination of four prelirninaryperformance assessments conducted between 1989 and 1992. "This paper provides a historical setting and context for how the performance of the deep geologic repository at the WIPP was analyzed.' Also included is background on political forces .acting on the project.Key Words: performance assessmen~probabilistic risk assessment risk assessment; radioactive waste disposal; Waste Isolation Pilot PlanG history . '1.0 IntroductionIn 1998,25 years 'after selection of the "Delaware Basin in southeastern New Mexico as a~otential disposal site for radioactive waste, the U.S. Environmental Protection Agency (EPA) certified that the Waste Isolation Pilot Plant (WIPP), an underground geologic disposal system, complied with its regulations. This paper presents a historical summary of the system characterization, engineering analyses, and scientific investigations undertaken by the WIPP Project over the past 25 years and provides a context for the~esults presented in this special issue of Reliability Engineering and System Safety. Although it is mot .essentird to know the WIPP'S history to comprehend the engineering analysis, an understanding of the issues that the project faced can be helpful. Many paths were followed during these 25 years to discern which phenomena were important at the WIPP, and often these paths were initiated in Tesponse to evolving notions of what kind of :g@tific information was "significant, what level of understanding was required, and how society could use this scientific information to decide whether deep geologic disposal of nuclear waste was acceptable.1-3/9/99 Draft \. DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document... .- Characterization of WIPP Disposal SystemThe choice of New Mexico as a potential disposal site for nuclear waste in 1973 (Claibome and Gera, 1974) was one in a series of episodes in which New Mexico had figured prominently with regard to nuclear phenomena. In 1942, the Manhattan Engineering Dkrnct selected New Mexico as the location (including what are known now asLos Alamos National Laboratory and Sandia National Laboratories) for assembling the scientists, engineers, and technicians who would develop the fist atomic bomb. As a direct consequence of that development, the first atomic explosion took place in 1945 in the desert near Alamogordo, New Mexico (Serber, 1992). Sixteen years later, in 1961, scientists with the Gnome Project detonated a device in the Delaware Basin in bedded salt near Carlsbad, New Mexico, as part of the Plowshare Program, which was exploring nonmilitary uses of nuclear explosives (Gard, 1968).After a potential...

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Section: Iteration Of Calculationsmentioning

confidence: 99%

Section: Iteration Of Calculationsmentioning

confidence: 99%

Section: Detailed Modeling Stylementioning

confidence: 99%

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Historical background on performance assessment for the Waste Isolation Pilot Plant

Rechard

2000

Reliability Engineering & System Safety

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“…Regulatory Commission (NUREG-1150) provides an example of a very large analysis in which an extensive effort was made to separate stochastic and subjective uncertainty (U.S. NRC 1990, Breeding et al 1992). This analysis was instituted in response to criticisms that the Reactor Safety Study (U.S. NRC 1975) had inadequately characterized the uncertainty in its results (Lewis et al 1978).…”

Section: -12mentioning

confidence: 99%

“…When a distinction between stochastic and subjective uncertainty is not maintained, the deleterious events associated with a system, the likelihood of such events, and the confidence with which both likelihood and consequences can be estimated become commingled in a way that makes it difficult to draw useful insights. Due to the pervasiveness and importance of these two types of uncertainty, they have attracted many investigators (e.g., Kaplan and Garrick 1981;Vesely and Rasmuson 1984;Pate-Cornell 1986Whipple 1986;Silbergeld 1987;Parry 1988;Apostolakis 1989Apostolakis , 1990JAEA 1989;Finkel 1990;McKone and Bogen 1991;Breeding et al 1992;Anderson et al 1993;Helton 1993aHelton , 1994Helton , 1997Kaplan 1993;Hoffman and Hammonds 1994;Brattin et al 1996;Frey and Rhodes 1996;Rai et al 1996) and also many names (e.g., aleatory, type A, irreducible, and variability as alternatives to the designation stochastic, and epistemic, type B, reducible, and state of knowledge as alternatives to the designation subjective). Indeed, this distinction can be traced back to the beginnings of the formal development of probability theory in the seventeenth century (Hacking 1975).…”

Section: -12mentioning

confidence: 99%

Uncertainty and Sensitivity Analysis Results Obtained in the 1996 Performance Assessment for the Waste Isolation Pilot Plant

Bean¹,

Berglund²,

Davis³

et al. 1998

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The Waste Isolation Pilot Plant (WPP) is located in southeastern New Mexico and is being developed by the U.S. Department of Energy (DOE) for the geologic (deep underground) disposal of transuranic waste. A detailed performance assessment (PA) for the WIPP was carried out in 1996 and supports an application by the DOE to the U.S. Environmental Protection Agency (EPA) for the certification of the WIPP for the disposal of TRU waste. The 1996 WIPP PA uses a computational structure that maintains a separation between stochastic (i.e., aleatory) and subjective (Le., epistemic) uncertainty, with stochastic uncertainty arising from the many possible disruptions that could occur over the 10,000 yr regulatory period that applies to the WIPP and subjective uncertainty arising from the imprecision with which many of the quantities required in the PA are known. Important parts of this structure are (1) the use of Latin hypercube sampling to incorporate the effects of subjective uncertainty, (2) the use of Monte Carlo (Le., random) sampling to incorporate the effects of stochastic uncertainty, and (3) the efficient use of the necessarily limited number of mechanistic calculations that can be performed to support the analysis. The use of Latin hypercube sampling generates a mapping from imprecisely known analysis inputs to analysis outcomes of interest that provides both a display of the uncertainty in analysis outcomes (i.e., uncertainty analysis) and a basis for investigating the effects of individual inputs on these outcomes (i.e., sensitivity analysis). The sensitivity analysis procedures used in the PA include examination of scatterplots, stepwise regression analysis, and partial correlation analysis. Uncertainty and sensitivity analysis results obtained as part of the 1996 WIPP PA are presented and discussed. Specific topics considered include two phase flow in the vicinity of the repository, radionuclide release from the repository, fluid flow and radionuclide transport in formations overlying the repository, and complementary cumulative distribution functions used in comparisons with regulatory standards (i.e., 40 CFR 191, Subpart B). 12-6Transport . . .... A-24Time-dependent radionuclide inventories expressed in EPA units (i.e., the normalized units used in showing compliance with 191.13(a)) for entire repository (Sanchez et al. 1997). Left frame shows radionuclides included in groundwater transport calculations; right frame shows radionculides not included in groundwater transport because of low inventory or short half-life. All radionuclides shown are included in estimates of cuttings and cavings and spallings; direct brine releases included all except . 4-75Flowing bottom hole pressure (FBHP) (Le., p,,in Eq. (4.7.22)) as a function of brine well index (Le., J b in Eq. (4.7.5)) and panel pressure for a system.with only mobile brine (i.e., krg = 0) ( . 4-78Flowing bottom hole pressure (FBHP) (Le., p,,in Eq. (4.7.22)) as a function of relative permeabilities and panel pressure for a brine dominated sys...

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Latin Hypercube Sampling

Iman

2008

Encyclopedia of Quantitative Risk Analysis and Assessment

124

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This chapter discusses the use of computer models for such diverse applications as safety assessments for geologic isolation of radioactive waste and for nuclear power plants; loss cost projections for hurricanes; reliability analyses for manufacturing equipment; transmission of HIV; and subsurface storm flow modelling. Such models are usually characterized by a large number of input variables (perhaps as many as a few hundred), and usually, only a handful of these inputs are important for a given response. In addition, the model response is frequently multivariate and time dependent. Latin hypercube sampling (LHS) uses a stratified sampling scheme to improve on the coverage of the k ‐dimensional input space for such computer models. This means that a single sample will provide useful information when some input variable(s) dominate certain responses (or certain time intervals), while other input variables dominate other responses (or time intervals). By sampling over the entire range, each variable has the opportunity to show up as important, if it indeed is important. If an input variable is not important, then the method of sampling is of little or no concern. The values of the stratified sampling scheme can be paired to ensure a desired correlation structure among the k input variables. LHS is more efficient than simple random sampling in a large range of conditions.

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Summary description of the methods used in the probabilistic risk assessments for NUREG-1150

Cited by 92 publications

References 30 publications

Historical background on performance assessment for the Waste Isolation Pilot Plant

Historical background on performance assessment for the Waste Isolation Pilot Plant

Uncertainty and Sensitivity Analysis Results Obtained in the 1996 Performance Assessment for the Waste Isolation Pilot Plant

Latin Hypercube Sampling

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