Nuclear Regulatory Commission Regulations Research Articles

Verification of the Coupled Code PARCS/TWOPORFLOW with Rod Ejection Accident Calculations for Small Modular Reactors

Research on small modular reactors (SMRs) is gaining importance since they are key for addressing energy challenges in various sectors. These types of reactors integrate novel technologies that rely heavily on passive safety systems. Among the most developed light water reactors, SMR designs are SMART and NuScale. This work analyzes the academic boron-free Karlsruhe Small Modular Reactor (KSMR), which may fit in SMART, and a core design resembling NuScale. The research aims to explore the potential of new multiphysics tools under development to predict safety parameters of SMRs during normal operation and transients. For this purpose, the Purdue Advanced Reactor Core Simulator (PARCS) and TWOPORFLOW (TPF) codes have been coupled using the Interface for Code Coupling (ICoCo), orchestrating code execution through a C++ Supervisor program. In this work, a nodewise rod ejection accident (REA) has been analyzed for two different scenarios. The first is a hot-zero-power scenario for the KSMR core, and the second is initiated at 75% of nominal power for the NuScale core. Verification of results has been done though code-to-code comparison. Comparison of the PARCS/TPF results obtained for both KSMR and NuScale with reference cases shows acceptable differences. Key safety parameters predicted by the codes for the REA analysis of both cores have also been evaluated against the latest U.S. Nuclear Regulatory Commission regulation for reactivity initiated accidents showing that all parameters fulfill core coolability acceptance criteria and fuel rod cladding failure thresholds. The presented work highlights the transition from the coupling of PARCS with a mixture model code, such as SCF, to a coupling with a two-phase model code, such as TPF. These findings contribute to a better understanding of SMR phenomenology during accidental sequences and demonstrate the capabilities of the coupled codes.

Extravasation of radiopharmaceuticals: Why report?

In this essay, I wish to discuss extravasation in the context of medical imaging and therapy with radiopharmaceuticals. Central to this discussion are two facts. First, they are easily identified, but the frequency of significant extravasations is unclear because there is no generally accepted definition of such an event. And second, there appears to be few reports of injuries from these events. The central thesis of this essay is that these events should be reported and followed so that agreement can be reached on the definition of a "significant" event which should be classified as a medical event in accordance with US Nuclear Regulatory Commission (NRC) regulations. I will also outline steps that can be taken to reduce the risk of extravasations.

Road to becoming Y-90 authorized user as an integrated vascular and interventional radiology resident (NRC alternate pathway)

Yttrium-90 (Y-90) radioembolization, also called transarterial radioembolization (TARE), is a catheter-directed therapy for direct delivery of internal radiation to tumors in the form of microspheres. It is currently available in two forms, either as a constituent of glass microspheres called TheraSphere® (BTG Ltd., London, UK [now Boston Scientific, Marlborough, MA, USA]) or as a biocompatible resin-based microsphere called SIR-Spheres® (Sirtex Medical Ltd., Woburn, MA, USA). Once these microspheres are delivered to the tumor through an arterial pathway, they are embedded within the tumor microcirculation and emit β-radiation at therapeutic levels. TARE is a commonly used treatment for unresectable primary or secondary hepatic malignancies and has led to improved survival rates and increased success rates in downstaging patients before liver resection or transplantation. Immediately following the pre-treatment angiogram, each patient undergoes a nuclear medicine study, otherwise known as technetium (99mTc) macroaggregated albumin scan, to determine the amount of radiotracer that has accumulated in the lungs (lung shunt fraction). Finally, after several calculations, the appropriate radiation dose to be delivered to the tumor is determined. While the technical aspects of radioembolization are quite complex, the collective clinical experience presented in the literature supports the use of Y-90 radioembolization for unresectable hepatic malignancies. Those ordering and administering radioembolization particles must be deemed an authorized user (AU) by the Nuclear Regulatory Commission (NRC). The NRC defines an AU as the individual responsible for ensuring that radioactive materials are handled and used safely and following NRC regulations and the terms and conditions of the NRC license. The NRC has published licensing guidance on Y-90 brachytherapy with the 10th revision released on November 8, 2019. This guidance has outlined specific requirements for obtaining a license for the use of TheraSphere and SIR-Spheres. Following the revised licensure guidelines from the NRC on Y-90 usage, a conditional authorization has been obtained at our institution by the PGY-6 interventional radiology/diagnostic radiology (IR/DR) resident. While the full guidelines and extensive alternative requirements can be found online, we will highlight the specific guidelines applicable to and fulfilled by IR/DR residents. The traditional ABR pathway takes approximately 18 months after graduation, including passing the ABR certification examination to become an AU. With the proposed alternate pathway, trainees will potentially become AU immediately after graduation. The primary aim of this submission is to describe the process for obtaining conditional authorization for Y-90 microspheres for PGY-6 IR/DR residents.

Research on the Application of Fen for Environmentally Assisted Fatigue Evaluation of the Austenitic SS Pipe Under Combined Transient Loads

Accumulative test data indicate that the effects of the light water reactor (LWR) environment could cause the fatigue resistance of primary pressure boundary components materials to be significantly reduced. Environmentally assisted fatigue (EAF) is the abbreviation of the environmentally assisted fatigue. In 2007, Nuclear Regulatory Commission (NRC) issued RG. 1.207. It was updated in 2014. And, it requires that the effects of LWR environment on the fatigue life reduction of metal components should be considered for new design plants. And it suggests to use environmental correction factor, Fen, to account for EAF. NRC regulation (NUREG), NUREG/CR-6909 (NRC, 2013, “Effect of LWR Coolant Environments on the Fatigue Life of Reactor Materials,” U.S. Nuclear Regulatory Commission, Argonne, IL, Standard no. NUREG/CR-6909), presents the detail Fen calculation formula. Fen is a function of temperature, strain rate, dissolved oxygen level in water, and sulfur content of the steel. Accordingly, Fen calculation will present a comparatively conservative result. Depending on the experience of the primary pressure boundary piping transient operation, Fen varies during each transient. More uncertainty and confusion are raised during the application of the Fen method. The research work in this paper includes: first, the typical character of piping thermal transient is derived based on the existing experience. Second, small specimen EAF tests are conducted depending on the above derived combined loading characters. Then effort is taken to improve the application of the Fen method for the combined multitransient loading conditions. And the results are compared with those of the lowest instantaneous Fen method and equalization of the weighted Fen method. Finally, a designed test plan is presented.

The Gamma Atmospheric Dispersion Factor for Finite-Cloud Radiation Dose Computations

Estimates of radiation doses to receptors in the vicinity of nuclear power plants from gaseous effluents are important to ensure that plant operation is in compliance with the as-low-as-reasonably-achievable dose objectives delineated in 10 CFR 50, Appendix I. The U.S. Nuclear Regulatory Commission (NRC) recently issued an Advance Notice of Proposed Rulemaking (ANPR) on the development of a new regulatory basis in support of aligning the NRC regulations governing dose assessments for radioactive effluents with the most recent methodology published by the International Commission on Radiological Protection (ICRP) contained in ICRP Publication 103 (ICRP-103) (2007). The ANPR specifically recommends that the dose conversion factors (DCFs) in Regulatory Guide 1.109 (RG 1.109) be revised as part of any effort to more closely align the NRC's regulations with the ICRP-103 recommendations. Section C.2 of RG 1.109 provides a sector-average (SA) finite-cloud model for computation of annual doses at off-site receptors from noble gas releases from freestanding tall stacks. One of the limitations of this model is that embedded in the applicable equation is the DCF, and as such, the model is not suitable for implementation of the ANPR (if approved) and the recommended use of stand-alone updated DCFs. This limitation can be circumvented through use of the “gamma atmospheric dispersion factor” in the finite-cloud dose model, referred to as the gamma (Ç/Q). A second limitation of the SA finite-cloud model is the dose overestimation at close-in receptors under very stable conditions and elevated plumes, which can be eliminated by using the corresponding finite-cloud gamma (Ç/Q) for the plume-centerline (PC) model. Presented are analytical details on the derivation and use of the SA and PC gamma (Ç/Q)'s, which are suitable for incorporation of stand-alone updated sets of DCFs based on ICRP-103.

Occupational Dose and Dose Limits: Experience in a Large Multisite Hospital System

PurposeThe Nuclear Regulatory Commission (NRC) has recently proposed changes that reduce the occupational dose limits for lens dose equivalent (LDE), embryo/fetus dose, and administrative control levels (ACLs) related to deep dose equivalent (DDE). This study collected occupational dose data from a large hospital system and determined how proposed NRC regulatory changes may affect worker and hospital workflow. MethodsRadiation badge data were collected for 1,305 workers, from between 2013 and 2014, and 180 pregnancies, from between 2009 and 2014. Median values for LDE, DDE, and embryo/fetus dose were determined. Current and proposed NRC regulations were applied, and the percentage of workers exceeding regulatory limits/ACLs was recorded. Fisher’s exact test was applied to determine if physicians were disproportionately affected by dose regulations. ResultsMedian doses were one to two orders of magnitude lower than current annual dose limits prescribed by the NRC. Proposed NRC regulations significantly increased the percentage of workers who exceeded limits and ACLs. Interventional radiologists, pain medicine physicians, and cardiologists working in catheter laboratories were most affected by LDE limits and DDE ACLs. Nuclear medicine technologists were most affected by embryo/fetus limits. Physicians were disproportionately affected by regulations (odds ratio 26.86; P < .0001). ConclusionsProposed NRC regulatory changes will cause a small increase in the number of workers who exceed ACLs and limits. Physicians and pregnant nuclear medicine workers are most affected and may need to alter their workloads. Practical difficulties in implementing cumulative dose tracking, and use of an LDE shielding factor, should be considered.

Soil–structure interaction analyses to locate nuclear power plant free-field seismic instrumentation

The recorded earthquake ground motion at the nuclear power plant site is needed for several purposes. US Nuclear Regulatory Commission (NRC) Regulatory Guide 1.12, Nuclear Power Plant Instrumentation for Earthquakes, NRC (1997a), describes acceptable instrumentation to meet the requirements in NRC's regulations pertaining to earthquake engineering criteria for nuclear power plants. The ground motion data recorded by the free-field seismic instrumentation are used to compare the actual earthquake motion at the site with the design input motion. The result of the comparison determines if the Operating Basis Earthquake ground motion (OBE) has been exceeded and plant shutdown is required per the guidance in NRC Regulatory Guide 1.166, Pre-Earthquake Planning and Immediate Nuclear Power Plant Operator Postearthquake Actions, NRC (1979b). The free-field is defined as a location on the ground surface or in the site soil column that is sufficiently distant from the site structures to be essentially unaffected by the vibration of the site structures.

Time-domain soil-structure interaction analysis of nuclear facilities

The Nuclear Regulatory Commission (NRC) regulation 10 CFR Part 50 Appendix S requires consideration of soil-structure interaction (SSI) in nuclear power plant (NPP) analysis and design. Soil-structure interaction analysis for NPPs is routinely carried out using guidance provided in the ASCE Standard 4-98 titled “Seismic Analysis of Safety-Related Nuclear Structures and Commentary”. This Standard, which is currently under revision, provides guidance on linear seismic soil-structure-interaction (SSI) analysis of nuclear facilities using deterministic and probabilistic methods. A new appendix has been added to the forthcoming edition of ASCE Standard 4 to provide guidance for time-domain, nonlinear SSI (NLSSI) analysis. Nonlinear SSI analysis will be needed to simulate material nonlinearity in soil and/or structure, static and dynamic soil pressure effects on deeply embedded structures, local soil failure at the foundation-soil interface, nonlinear coupling of soil and pore fluid, uplift or sliding of the foundation, nonlinear effects of gaps between the surrounding soil and the embedded structure and seismic isolation systems, none of which can be addressed explicitly at present.Appendix B of ASCE Standard 4 provides general guidance for NLSSI analysis but will not provide a methodology for performing the analysis. This paper provides a description of an NLSSI methodology developed for application to nuclear facilities, including NPPs. This methodology is described as series of sequential steps to produce reasonable results using any time-domain numerical code. These steps require some numerical capabilities, such as nonlinear soil constitutive models, which are also described in the paper.

Worker Protection Implications of the Solubility and Human Metabolism of Modern Uranium Mill Products in the U.S.

This paper presents an analysis of the implications of some recent studies performed to characterize uranium products from modern uranium recovery facilities important for worker protection. Assumptions about the solubility (related to the molecular species being produced) of these materials in humans are critical to properly assess radiation dose from intakes, understand chemotoxic implications, and establish protective exposure standards (airborne concentrations, limits on intake, etc.). Recent studies, as well as information in the historical professional literature, were reviewed that address the issue of solubility and related characteristics. These data are important for the design of programs for assessment of both chemical and radiological aspects of worker exposure to the products of modern uranium recovery plants (conventional uranium mills and in situ recovery plants; i.e., ISRs). The data suggest strongly that the oxide form produced by these facilities (and therefore, product solubility) is related to precipitation chemistry and thermal exposure (dryer temperature). Given the peroxide precipitation and low temperature drying methods being used at many modern uranium recovery facilities in the U.S. today, very soluble products are being produced. The dosimetric impacts of these products to the pulmonary system (except perhaps in case of an extreme acute insult) would be small, and any residual pulmonary retention beyond a month or two would most likely be too small to measure by traditional urinalysis sampling or the current state-of-the-art of natural uranium in vivo lung counting techniques. Uranium recovery plants should revisit the adequacy of current bioassay programs in the context of their process and product specifics. Workers potentially exposed to these very soluble yellowcake concentrates should have urine specimens submitted for uranium analysis on an approximately weekly basis, including analysis for the biomarkers associated with potential renal injury [e.g., glucose, lactate dehydrogenase (LDH) and protein albumen]. Additionally, implications for compliance with current U.S. Nuclear Regulatory Commission (NRC) regulations (e.g., 10 CFR20) are discussed. NRC, the applicable Agreement State agencies, and licensees need to recognize the importance of the uranium chemotoxicity versus dose relationship in the interest of worker protection.

Are the makings of a dirty bomb in your neighborhood?

Although regulators say that current protections are adequate, the US government continues to pay for extra security features for facilities that hold radiological materials.

Development of training course on transport security of radioactive materials

AbstractArgonne National Laboratory (Argonne), with the support of the US Department of Energy (DOE) Packaging Certification Program, has developed a week long training course on security for nuclear and other radioactive materials during transport. The course focuses on USA domestic and international requirements and recommendations for transport security. A review of applicable US Department of Transportation regulations, recently issued US Nuclear Regulatory Commission regulations, DOE orders and manuals, and relevant international modal regulatory documents relating to transport security was conducted. The review disclosed that existing International Atomic Energy Agency security training materials could be incorporated into a training course on security requirements for US domestic shippers. Development of training materials for such a course was initiated in late 2012, and the first course was convened in early December 2013 at Argonne. The course also incorporated training and hands on transport se...

Expected dose and associated uncertainty and sensitivity analysis results for the human intrusion scenario in the 2008 performance assessment for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada

Extensive work has been carried out by the U.S. Department of Energy (DOE) in the development of a proposed geologic repository at Yucca Mountain (YM), Nevada, for the disposal of high-level radioactive waste. In support of this development and an associated license application to the U.S. Nuclear Regulatory Commission (NRC), the DOE completed an extensive performance assessment (PA) for the proposed YM repository in 2008. This presentation describes the determination of expected (mean) dose to the reasonably maximally exposed individual (RMEI) specified in the NRC regulations for the YM repository resulting from an inadvertent drilling intrusion into the repository. The following topics are addressed: (i) assumed properties of an inadvertent drilling intrusion and the determination of the associated dose and expected (mean) dose to the RMEI, (ii) uncertainty and sensitivity analysis results for expected dose to the RMEI, and (iii) the numerical stability of the sampling-based procedure used to estimate expected (mean) dose to the RMEI. The present article is part of a special issue of Reliability Engineering and System Safety devoted to the 2008 YM PA; additional articles in the issue describe other aspects of the 2008 YM PA.

Expected dose for the seismic scenario classes in the 2008 performance assessment for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada

Extensive work has been carried out by the U.S. Department of Energy (DOE) in the development of a proposed geologic repository at Yucca Mountain (YM), Nevada, for the disposal of high-level radioactive waste. In support of this development and an associated license application to the U.S. Nuclear Regulatory Commission (NRC), the DOE completed an extensive performance assessment (PA) for the proposed YM repository in 2008. This presentation describes the determination of expected dose to the reasonably maximally exposed individual (RMEI) specified in the NRC regulations for the YM repository for the seismic ground motion scenario class and the seismic fault displacement scenario class in the 2008 YM PA. The following topics are addressed: (i) definition of the seismic scenario classes and the determination of dose and expected dose to the RMEI, (ii) properties of the seismic ground motion scenario class, (iii) expected dose and uncertainty in expected dose to the RMEI for the seismic ground motion scenario class from 0 to 20,000yr, (iv) expected dose and uncertainty in expected dose to the RMEI for the seismic ground motion scenario class from 0 to 106yr, (v) properties of the seismic fault displacement scenario class including expected dose and uncertainty in expected dose to the RMEI from 0 to 20,000yr and 0 to 106yr, (vi) expected dose and uncertainty in expected dose to the RMEI for the combined ground motion and seismic fault displacement scenario class, and (vii) probabilities associated with seismic scenario classes. The present article is part of a special issue of Reliability Engineering and System Safety devoted to the 2008 YM PA; additional articles in the issue describe other aspects of the 2008 YM PA.

Uncertainty and sensitivity analysis for the igneous scenario classes in the 2008 performance assessment for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada

Extensive work has been carried out by the U.S. Department of Energy (DOE) in the development of a proposed geologic repository at Yucca Mountain (YM), Nevada, for the disposal of high-level radioactive waste. In support of this development and an associated license application to the U.S. Nuclear Regulatory Commission (NRC), the DOE completed an extensive performance assessment (PA) for the proposed YM repository in 2008. This presentation describes uncertainty and sensitivity analysis results for the igneous intrusive scenario class and the igneous eruptive scenario class obtained in the 2008 YM PA. The following topics are addressed for the igneous intrusive scenario class: (i) engineered barrier system conditions, (ii) release results for the engineered barrier system, unsaturated zone, and saturated zone, (iii) dose to the reasonably maximally exposed individual (RMEI) specified in the NRC regulations for the YM repository, and (iv) expected dose to the RMEI. In addition, expected dose to the RMEI for the igneous eruptive scenario class is also considered. The present article is part of a special issue of Reliability Engineering and System Safety devoted to the 2008 YM PA; additional articles in the issue describe other aspects of the 2008 YM PA.

Expected dose for the nominal scenario class in the 2008 performance assessment for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada

Extensive work has been carried out by the U.S. Department of Energy (DOE) in the development of a proposed geologic repository at Yucca Mountain (YM), Nevada, for the disposal of high-level radioactive waste. In support of this development and an associated license application to the U.S. Nuclear Regulatory Commission (NRC), the DOE completed an extensive performance assessment (PA) for the proposed YM repository in 2008. This presentation describes the determination of expected (mean) dose to the reasonably maximally exposed individual (RMEI) specified in the NRC regulations for the YM repository for the nominal scenario class (i.e., under nominal or undisturbed conditions) in the 2008YM PA. The following topics are addressed: (i) properties of the nominal scenario class and the determination of dose and expected (mean) dose to the RMEI, (ii) uncertainty in dose and resultant expected (mean) dose to the RMEI, (iii) expected (mean) dose to the RMEI from individual radionuclides, and (iv) numerical stability of the sampling-based procedure used to estimate the expected (mean) dose to the RMEI. The present paper is part of a special issue of Reliability Engineering and System Safety devoted to the 2008YM PA; additional papers in the issue describe other aspects of the 2008YM PA.

Uncertainty and sensitivity analysis for the nominal scenario class in the 2008 performance assessment for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada

Extensive work has been carried out by the U.S. Department of Energy (DOE) in the development of a proposed geologic repository at Yucca Mountain (YM), Nevada, for the disposal of high-level radioactive waste. In support of this development and an associated license application to the U.S. Nuclear Regulatory Commission (NRC), the DOE completed an extensive performance assessment (PA) for the proposed YM repository in 2008. This presentation describes uncertainty and sensitivity analysis results for the nominal scenario class (i.e., for undisturbed conditions) obtained in the 2008 YM PA. The following topics are addressed: (i) uncertainty and sensitivity analysis procedures, (ii) drip shield and waste package failure, (iii) engineered barrier system conditions, (iv) radionuclide release results for the engineered barrier system, unsaturated zone, and saturated zone, and (v) dose to the reasonably maximally exposed individual specified in the NRC regulations for the YM repository. The present article is part of a special issue of Reliability Engineering and System Safety devoted to the 2008 YM PA; additional articles in the issue describe other aspects of the 2008 YM PA.

Summary discussion of the 2008 performance assessment for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada

A deep geologic repository at Yucca Mountain (YM), Nevada, for the disposal of spent nuclear fuel and high-level radioactive waste was proposed by the U.S. Department of Energy (DOE). This paper summarizes the historical development of the 2008 YM performance assessment (PA), and explains how the methods and results of the 2008 PA address regulatory requirements specified by the United States Environmental Protection Agency (EPA) and the United States Nuclear Regulatory Commission (NRC). Topics covered include (i) screening of features, events and processes, (ii) development of scenario classes, (iii) descriptions of barrier capability, and (iv) compliance with applicable quantitative standards for individual protection, individual protection following human intrusion, and ground water protection. This article is part of a special issue of Reliability Engineering and System Safety devoted to the 2008 YM PA and provides a brief summary of information presented in detail in multiple articles in this issue and interprets the results in the context of applicable EPA and NRC regulations.

Uncertainty and sensitivity analysis for the early failure scenario classes in the 2008 performance assessment for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada

Extensive work has been carried out by the U.S. Department of Energy (DOE) in the development of a proposed geologic repository at Yucca Mountain (YM), Nevada, for the disposal of high-level radioactive waste. In support of this development and an associated license application to the U.S. Nuclear Regulatory Commission (NRC), the DOE completed an extensive performance assessment (PA) for the proposed YM repository in 2008. This presentation describes uncertainty and sensitivity analysis results for the early waste package failure scenario class and the early drip shield failure scenario class obtained in the 2008 YM PA. The following topics are addressed: (i) engineered barrier system conditions, (ii) release results for the engineered barrier system, unsaturated zone, and saturated zone, (iii) dose to the reasonably maximally exposed individual (RMEI) specified in the NRC regulations for the YM repository, and (iv) expected dose to the RMEI. The present article is part of a special issue of Reliability Engineering and System Safety devoted to the 2008 YM PA; additional articles in the issue describe other aspects of the 2008 YM PA.

Expected dose for the igneous scenario classes in the 2008 performance assessment for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada

Extensive work has been carried out by the U.S. Department of Energy (DOE) in the development of a proposed geologic repository at Yucca Mountain (YM), Nevada, for the disposal of high-level radioactive waste. In support of this development and an associated license application to the U.S. Nuclear Regulatory Commission (NRC), the DOE completed an extensive performance assessment (PA) for the proposed YM repository in 2008. This presentation describes the determination of expected dose to the reasonably maximally exposed individual (RMEI) specified in the NRC regulations for the YM repository for the igneous intrusive scenario class and the igneous eruptive scenario class in the 2008 YM PA. The following topics are addressed: (i) properties of the igneous scenario classes and the determination of dose and expected dose to the RMEI, (ii) expected dose and uncertainty in expected dose to the RMEI from the igneous intrusive scenario class, (iii) expected dose and uncertainty in expected dose to the RMEI from the igneous eruptive scenario class, (iv) expected dose and uncertainty in expected dose to the RMEI from the combined igneous intrusive and igneous eruptive scenario class, and (v) uncertainty in the occurrence of igneous scenario classes. The present article is part of a special issue of Reliability Engineering and System Safety devoted to the 2008 YM PA; additional articles in the issue describe other aspects of the 2008 YM PA.

Expected dose for the early failure scenario classes in the 2008 performance assessment for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada

Extensive work has been carried out by the U.S. Department of Energy (DOE) in the development of a proposed geologic repository at Yucca Mountain (YM), Nevada, for the disposal of high-level radioactive waste. In support of this development and an associated license application to the U.S. Nuclear Regulatory Commission (NRC), the DOE completed an extensive performance assessment (PA) for the proposed YM repository in 2008. This presentation describes the determination of expected dose to the reasonably maximally exposed individual (RMEI) specified in the NRC regulations for the YM repository for the early waste package (WP) failure scenario class and the early drip shield (DS) failure scenario class in the 2008 YM PA. The following topics are addressed: (i) properties of the early failure scenario classes and the determination of dose and expected dose the RMEI, (ii) expected dose and uncertainty in expected dose to the RMEI from the early WP failure scenario class, (iii) expected dose and uncertainty in expected dose to the RMEI from the early DS failure scenario class, (iv) expected dose and uncertainty in expected dose to the RMEI from the combined early WP and early DS failure scenario class with and without the inclusion of failures resulting from nominal processes, and (v) uncertainty in the occurrence of early failure scenario classes. The present article is part of a special issue of Reliability Engineering and System Safety devoted to the 2008 YM PA; additional articles in the issue describe other aspects of the 2008 YM PA.