Development of a Performance Assessment Capability in the Waste Management Programs of the U.S. Nuclear Regulatory Commission

The U.S. Nuclear Regulatory Commission (NRC) staff has developed a performance assessment capability to address three programmatic areas in nuclear waste management: high-level waste, low-level waste, and decommissioning of licensed facilities (license termination). The NRC capability consists of: (1) methodologies for performance assessment; (2) models and computer codes for estimating system performance; (3) regulatory guidance in various forms, such as regulations, Branch Technical Positions, and Standard Review Plans; and (4) a technical staff experienced in executing and evaluating performance assessments for a variety of waste systems. Although the tools and techniques are refined for each programmatic area, general approaches and similar issues are encountered in all areas.     

Ramifications of Risk Measures in Implementing Quantitative Performance Assessment for the Proposed Radioactive Waste Repository at Yucca Mountain, Nevada, USA

As part of its preparation to review a potential license application from the U.S. Department of Energy (DOE), the U.S. Nuclear Regulatory Commission (NRC) is examining the performance of the proposed Yucca Mountain nuclear waste repository. In this regard, we evaluated postclosure repository performance using Monte Carlo analyses with an NRC-developed system model that has 950 input parameters, of which 330 are sampled to represent system uncertainties. The quantitative compliance criterion for dose was established by NRC to protect inhabitants who might be exposed to any releases from the repository. The NRC criterion limits the peak-of-the-mean dose, which in our analysis is estimated by averaging the potential exposure at any instant in time for all Monte Carlo realizations, and then determining the maximum value of the mean curve within 10000 years, the compliance period. This procedure contrasts in important ways with a more common measure of risk based on the mean of the ensemble of peaks from each Monte Carlo realization. The NRC chose the former (peak-of-the-mean) because it more correctly represents the risk to an exposed individual. Procedures for calculating risk in the expected case of slow repository degradation differ from those for low-probability cases of disruption by external forces such as volcanism. We also explored the possibility of risk dilution (i.e., lower calculated risk) that could result from arbitrarily defining wide probability distributions for certain parameters. Finally, our sensitivity analyses to identify influential parameters used two approaches: (1). the ensemble of doses from each Monte Carlo realization at the time of the peak risk (i.e., peak-of-the-mean) and (2). the ensemble of peak doses calculated from each realization within 10000 years. The latter measure appears to have more discriminatory power than the former for many parameters (based on the greater magnitude of the sensitivity coefficient), but can yield different rankings, especially for parameters that influence the timing of releases.     

Using Related Samples in Assessing Conformance to Safety Goals: A Nuclear Reactor Safety Application

Quantifying safety goals is a key to the regulation of activities which are beneficial on the whole but entail some risks in being performed. Determining compliance with safety goals involves dealing with uncertainties. A recent article by Bier^(I) describes some of the difficulties encountered using measures with uncertainty to determine compliance with safety goals for nuclear reactors. This paper uses a hierarchical Bayes approach to address two practical modeling problems in determining safety goal compliance under uncertainty: (1) allowing some modeling assumptions to be relaxed, and (2) allowing data from previous related samples to be included in the analysis. The two issues effect each other to the extent that relaxing some assumptions allows the use of a broader range of data. The usefulness of these changes and their impact on assessing safety compliance for nuclear reactors is shown.     

Modeling Precheck Parallel Screening Process in the Face of Strategic Applicants with Incomplete Information and Screening Errors

In security check systems, tighter screening processes increase the security level, but also cause more congestion, which could cause longer wait times. Having to deal with more congestion in lines could also cause issues for the screeners. The Transportation Security Administration (TSA) Precheck Program was introduced to create fast lanes in airports with the goal of expediting passengers who the TSA does not deem to be threats. In this lane, the TSA allows passengers to enjoy fewer restrictions in order to speed up the screening time. Motivated by the TSA Precheck Program, we study parallel queueing imperfect screening systems, where the potential normal and adversary participants/applicants decide whether to apply to the Precheck Program or not. The approved participants would be assigned to a faster screening channel based on a screening policy determined by an approver, who balances the concerns of safety of the passengers and congestion of the lines. There exist three types of optimal normal applicant's application strategy, which depend on whether the marginal payoff is negative or positive, or whether the marginal benefit equals the marginal cost. An adversary applicant would not apply when the screening policy is sufficiently large or the number of utilized benefits is sufficiently small. The basic model is extended by considering (1) applicants' parameters to follow different distributions and (2) applicants to have risk levels, where the approver determines the threshold value needed to qualify for Precheck. This article integrates game theory and queueing theory to study the optimal screening policy and provides some insights to imperfect parallel queueing screening systems.     

Safety Stock,Excess Capacity or Diversification: Trade‐Offs under Supply and Demand Uncertainty

Firms mitigate uncertainty in demand and supply by carrying safety stock, planning for excess capacity and diversifying supply sources. In this study, we provide a framework to jointly optimize these three levers in a periodic review infinite horizon setting, and in particular we examine how one can reduce inventory and capacity investments through proper diversification strategies. Observing that a modified base‐stock inventory policy is optimal, we find that the capacity‐diversification problem is well behaved and characterize the optimal mix of safety stock, excess capacity and extra number of supply sources. We find that higher supply uncertainty results in higher safety stock, more excess capacity, and higher diversification. But safety stock and diversification are non‐monotonic in demand uncertainty. Our results can be extended to situations in which suppliers are heterogeneous, and can be used to develop effective heuristics.     

Technology,Employment and Wages

This paper provides a critical review of the impact of technical change on the structure of relative wages and employment, and considers some alternative explanations for the immiseration of low skilled workers. In the absence of any clear and distinguishing policy blueprint, the paper also seeks to clarify the major issues raised by our discussion for employment policy.     

Probabilistic Risk Analyses: NRC Programs and Perspectives

The historical basis and more recent activities and products of probabilistic risk analysis (PRA) in the Atomic Energy Commission and Nuclear Regulatory Commission (NRC) are reviewed. Current NRC program activities and objectives are described. The author's opinions on the best uses of PRA are presented.     

Inventory Control with a Fixed Cost and a Piecewise Linear Convex Cost

This paper studies the optimal policy for a periodic‐review inventory system in which the production costs consist of a fixed cost and a piecewise linear convex variable cost. Such a cost function can arise from alternate sources of supply or from the use of overtime production. We fully characterize the structure of the optimal policy for the single‐period problem. For the multi‐period problem, the optimal policy can have disconnected production regions and complicated optimal produce‐up‐to levels, which implies that implementation of the optimal policy may not be practical. Fortunately, careful investigation shows that the optimal policy has some interesting properties. The structure of the optimal policy outlined by these properties leads to a practical and close‐to‐optimal heuristic policy. In an extensive numerical study, the average gap is only 0.02% and the worst gap is 1.37%.     

考虑多种安全库存策略的选址-库存问题研究

考虑多种安全设置策略的物流网络的选址-库存问题,不仅是选址、订货、运输和库存的集成优化,还需要考虑多种不同的安全库存设置和转运策略。因此,本文深入讨论了二级物流网络中的六种安全库存设置策略,构建了六种考虑不同安全库存设置的选址-库存模型。在考虑集中设置安全库存时,集中安全库存需要通过转载运输实现,因此需要将转载运输成本引入选址-库存模型之中,使新的选址-库存模型更加科学合理。另外,针对六种新的选址-库存模型,提出了基于个体成本差异分配的遗传算法,迭代搜索选址、分配、库存设置策略的优化组合。最后,通过数据实验验证了模型的有效性：（1）安全库存与转载运输之间存在此消彼长的背反关系;（2）安全库存设置和转载运输策略对总成本的影响取决于两种费率权重情况。本文的研究可以为二级物流网络的选址、订货和安全库存策略集成优化决策提供参考依据。     

Using farm assurance schemes to signal food safety to multiple food retailers in the U.K.

It is argued that privately run farm assurance schemes in the U.K. have been developed predominantly to signal the presence of desired levels of food safety (and other credence) attributes to domestic multiple food retailers. It is hypothesised that these food retailers will only buy ‘farm assured’ meat from abattoirs, therefore abattoirs must buy and process ‘farm assured’ livestock. Other factors, including abattoir size, procurement policy, level of processing and hygiene levels, are also hypothesised to affect the probability of an abattoir selling meat to large multiple retailers. The hypotheses are tested through a survey of abattoirs in the United Kingdom and a logistic regression is used to assess significance. It is found that buying farm assured livestock is a highly significant positive factor in selling meat to large multiple retailers; in addition, the procurement policy of abattoirs (affecting traceability of product) and abattoir size are also found to be significant determinants of the probability of this trade. The empirical evidence supports the hypothesis that industry-led farm assurance schemes are indeed used by large multiple food retailers as a credible signal of food safety (and other credence) attributes.     

Facts and Values in Risk Analysis for Environmental Toxicants

The U.S. Office of Science and Technology Policy describes toxic substance regulation as composed of two stages. Stage I (facts) uses empirical data and scientific judgment to characterize human exposure and risk. Stage II (values) uses social and political judgment to decide regulatory action based on significance of the risk, benefits of the agent, and costs of its control. This paper argues that such a view represents an unrealistic and unattainable goal. We present examples showing how values enter virtually every part of risk analysis, and we review work on the vagaries in human judgment concerning both facts and values. These issues indicate that U.S. regulatory policy needs reconsideration.     

Methods and Rationale for Derivation of a Reference Dose for Methylmercury by the U.S. EPA

In 2001, the U.S. Environmental Protection Agency derived a reference dose (RfD) for methylmercury, which is a daily intake that is likely to be without appreciable risk of deleterious effects during a lifetime. This derivation used a series of benchmark dose (BMD) analyses provided by a National Research Council (NRC) panel convened to assess the health effects of methylmercury. Analyses were performed for a number of endpoints from three large longitudinal cohort studies of the neuropsychological consequences of in utero exposure to methylmercury: the Faroe Islands, Seychelles Islands, and New Zealand studies. Adverse effects were identified in the Faroe Islands and New Zealand studies, but not in the Seychelles Islands. The NRC also performed an integrative analysis of all three studies. The EPA applied a total uncertainty factor (UF) of 10 for intrahuman toxicokinetic and toxicodynamic variability and uncertainty. Dose conversion from cord blood mercury concentrations to maternal methylmercury intake was performed using a one-compartment model. Derivation of potential RfDs from a number of endpoints from the Faroe Islands study converged on 0.1 microg/kg/day, as did the integrative analysis of all three studies. EPA identified several areas for which further information or analyses is needed. Perhaps the most immediately relevant is the ratio of cord:maternal blood mercury concentration, as well as the variability around this ratio. EPA assumed in its dose conversion that the ratio was 1.0; however, available data suggest it is perhaps 1.5-2.0. Verification of a deviation from unity presumably would be translated directly into comparable reduction in the RfD. Other areas that EPA identified as significant areas requiring further attention are cardiovascular consequences of methylmercury exposure and delayed neurotoxicity during aging as a result of previous developmental or adult exposure.     

The Nature,Social Organization and Promotion of Management Research: Towards Policy

This paper argues for the distinctiveness of management research and develops a perspective concerning management research policy. It argues that the key defining characteristic of management research is its applied nature, and that its central concern should be ‘the general (engineering) problem of design’. Because a key goal of management research is to improve the relationship between theory and practice, a fundamental concern lies with its diverse nature and the consequential difficulty of integration of sub-disciplines, as well as with the issue of the relevance and the application of findings. As a policy paper, it aims to introduce a limited number of analytical frameworks in order to develop a policy position, thus helping frame the debate concerning the role of management research. Specifically, it achieves this, first by exploring the ontology of management research, examining its form, features, peculiarities and idiosyncrasies using Becher's conceptual schema for exploring the nature of disciplines; second by identifying a requisite form of social organization to support management research activity using the Gibbons et al. taxonomy of knowledge production systems; and finally, by identifying some conclusions, research policy implications, and suggesting a set of policy propositions concerning the conduct of management research.     

POWER APPROXIMATIONS FOR A TWO-ECHELON INVENTORY SYSTEM USING SERVICE LEVELS

We consider a two-echelon inventory system with one warehouse and several stores. The warehouse as well as the stores are controlled by periodic review (s, S) inventory policies. We study the interrelationship between the safety stocks at the warehouse and the stores. Stockouts at the warehouse will result in supply delays to the stores and cause the lead time to be stochastic. The stores may react by increasing their safety stock. However, there is a trade-off between the safety stock at the warehouse and the safety stock at the stores. We use a service level at the warehouse to quantify the effect of warehouse stockouts on the lead time to the stores. The service level at the warehouse is considered a decision variable to find the best compromise between the various safety stocks by minimizing the overall costs. Using power approximations for the (s, S) policies, we provide an iterative procedure for adjusting the lead time distribution to the stores; this can result in substantial savings, but it doesn't guarantee the overall optimality. Numerical studies are provided to test the accuracy of approximations. The effects of the different system parameters on the inventory policy give general guidelines for use of the policies.     

Transparency in Europe: A Quantitative Study

In recent years, European pharmaceutical regulators have increasingly committed to heightening access to raw safety‐related data as part of a wave of transparency initiatives (e.g., providing public Internet‐mediated access to clinical trials data). Yet, the regulators—who are under significant pressure—have not yet benefited from a systematic review of this new policy. In seeking to inject much needed evidence, this article explores the effects of new transparency policies designed to promote meaningful communication of risks and benefits to patients. Results of a cross‐national European survey with respondents from Great Britain, the Netherlands, Spain, France, Germany, and Sweden (N = 5,648) shed light on how patients and the public are likely to react to the regulators’ new transparency policies. The findings demonstrate clear national variations in how European citizens are likely to react and emphasize the need to develop evidence‐based, reasoned transparency policies that integrate benefit‐risk communication. The authors conclude by providing six specific recommendations, informed by the study, that seek to improve the European transparency model both within the medical field and across health, safety, and environmental policy domains.     

The Use of Individual and Societal Risk Criteria Within the Dutch Flood Safety Policy—Nationwide Estimates of Societal Risk and Policy Applications

The Dutch government is in the process of revising its flood safety policy. The current safety standards for flood defenses in the Netherlands are largely based on the outcomes of cost‐benefit analyses. Loss of life has not been considered separately in the choice for current standards. This article presents the results of a research project that evaluated the potential roles of two risk metrics, individual and societal risk, to support decision making about new flood safety standards. These risk metrics are already used in the Dutch major hazards policy for the evaluation of risks to the public. Individual risk concerns the annual probability of death of a person. Societal risk concerns the probability of an event with many fatalities. Technical aspects of the use of individual and societal risk metrics in flood risk assessments as well as policy implications are discussed. Preliminary estimates of nationwide levels of societal risk are presented. Societal risk levels appear relatively high in the southwestern part of the country where densely populated dike rings are threatened by a combination of river and coastal floods. It was found that cumulation, the simultaneous flooding of multiple dike rings during a single flood event, has significant impact on the national level of societal risk. Options for the application of the individual and societal risk in the new flood safety policy are presented and discussed.     

International Business and Entrepreneurship Implications of Brexit

This paper provides an overview of the international business and entrepreneurship implications of Brexit. Our perspective is preliminary and based on a review of the practitioner, policy and academic literature over the first month following the Brexit vote. We highlight some of the potentially negative consequences for markets in the UK and around the world that result from barriers to trade and immigration associated with the uncertainty created by Brexit.     

Optimizing Risk Analysis Relating to External Safety in The Netherlands

Risk analyses in The Netherlands have been optimized so that they now express risks in a numerical form suitable for comparison to national safety standards. This factor is more important to national government than to local authorities; other factors relevant for local authorities are given less emphasis or even completely omitted from the results of the analysis. From a comparison of 16 risk analyses carried out during the last decade, it became clear that in the last 5 years the methods of risk analyses related to external safety have become unified. Results are now presented in terms of individual risk contours and in terms of F-N curves (accident frequency vs. exceeded number of fatalities). This unification seems to be a result of government policy. First, the implementation of the post-Seveso-directive (501/82/EC) in The Netherlands obliges a number of industries to provide the authorities with a quantitative risk assessment. Second, the government has set standards for the maximum permissible risk in residential areas. A unified type of risk analysis is a tool to achieve both these policies. From interviews with local government authorities, however, it has become clear that they need and use some quantitative risk information that is not provided by the unified analysis. They feel they need figures that provide insight into the effects of incidents and into the way effects may change as a result of safety measures. Ultimately, government policy may mean that local officials receive less information than before.     

A Periodic Inventory Model for Stocking Modular Components

We study the benefit obtained by exploiting modular product design in fulfilling exogenous demand for both a complete assembly and its components in a service parts inventory system. Our goal is to reduce overall service system costs by allowing assembly and/or disassembly (A/D) to occur at some unit cost per A/D action. In an extensive set of computational experiments, we compare a naïve stocking and operating policy that treats all items independently and ignores the modular product structure and related A/D capability to the optimal base stock policy, and to a policy that allows A/D from the naïve stocking levels. While extensive computational analysis shows that the optimal base stock policy improves the system cost between 3 to 26% over the naïve approach, simply allowing A/D from the naïve stocking levels captures a significant portion (an average of 67%) of the naïve–optimal gap. Our computational results demonstrate that the optimization shifts the component‐assembly mix from the naïve levels and that limiting A/D capacity affects this mix. Limiting A/D capacity can actually increase the expected number of A/D actions (versus the uncapacitated case), since the optimization shifts stocking levels to reduce the probability that “too many” actions will be required.     

Time for a revival? Public policy implementation: a review of the literature and an agenda for future research

This paper argues that there is not a vigorous contemporary literature in the UK which addresses implementation studies as part of the public policy process, whereas this is not the case in the USA. A review of the literature is presented, and a critique of the more traditional thematic groupings used to review the literature is given. A revised thematic review of the literature is presented based on the four themes of: (1) the role of knowledge and learning in policy implementation; (2) the processes of policy implementation; (3) the role of actors and agents in implementation; and (4) the role of bureaucratic discretion. The paper argues for a revival of research into public policy implementation and suggests a research agenda for the future which can use the aforementioned themes from the literature.