Nuclear Operation Research Articles

Silver Lining Study: Missileer Fatigue Mitigation During 2020 Coronavirus Pandemic.

The U.S. Air Force's Intercontinental Ballistic Missile (ICBM) force stands ready to launch weapons 365 days per year. Since its inception, missileers vigilantly operate launch consoles on a 3-day cycle: minimum 24-hour alert-shift/24-hour travel-admin/24-hour off, leading to concerns that health, morale, and alertness are chronically impacted. In 2020, a Missileer Occupational Health Assessment (OHA) revealed 76% of respondents struggle with being rested for duty and 29% of respondents never feel adequately rested for duty. Later that year, 20th Air Force initiated long-duration operations to safeguard from the SARS CoV-2 (COVID-19) Pandemic, resulting in increased operations tempo, and exacerbating crew fatigue.341st Operations Group and 341st Medical Group at Malmstrom Air Force Base enacted interventions to mitigate crew fatigue and support continued readiness during pandemic operations. They recorded, analyzed, and compiled findings in this report, including recommendations for long-term ICBM operations at Missile Wings. All participants were Nuclear and Missile Operations Officers, or missileers, were continuously evaluated with qualitative and quantitative measures to ensure safety of the force during a period of unprecedented change. Interventions implemented and evaluated during the 9-month period included: environmental modifications, scheduling changes, and crew education on fatigue management, nutrition, anticipatory sleep preparation, and fitness. Most notably, the 341st Operations Group examined various 3-person and 4-person shift-length and alert duration schedules. Psychomotor vigilance testing results validated safety of operators and delta between pre- and post-shift measurements. Crew force readiness trends were analyzed for force-health awareness. Pre- and post-OHA results were compared for subjective changes. Fatigue and health-related outcomes were collected from a safety monitoring effort during standard and COVID-19 operations at 341st Missile Wing. Findings from qualitative and quantitative data indicate the optimal schedule is a 3-week cycle:7-day alert/7-day recovery/7-day training-administrative utilizing 4-member or 3-member crews for low tempo operations. Crews experimented with shift-lengths of 24hrs-on/24hrs-off, 16hrs-on/8hrs-off, and 12hrs-on/12hrs-off. Maximum safe alert duration is 7 days due to task fatigue onset between 8 and 10 days. Short and long duration Duties Not to Include Flight (DNIF) (also known as Duties Not to Include Alert (DNIA) among missileers) rates decreased from the first to last month of the period by 74.6% and 79.2%, respectively. The number of alerts missed per month decreased 86% from baseline. The 2021 OHA found a 7% decline in members seeking separation, and absence of sleep, fatigue, and physical or mental health as missileer concerns. This analysis has identified a sustainable alert rotation of 7/7/7 with emphasis on protected recovery and training time and has been continued after concluding pandemic operations, creating consistent schedule stability where there once was none. If executed properly, this alert rotation, regardless of shift-length selected, has potential to improve trust between crews and leadership, provides adequate recovery time between alerts to maintain health, and improves wellness, family stability, morale, unit cohesion, and crew force retention. Notably, all Air Force Global Strike Missile Operations Groups adjusted scheduling practices to align with these findings.

Zeolites identification for wastewater radionuclides removal in the decommissioning of a former Italian nuclear power plant

Radionuclides are widely known to produce serious problem when released and dispersed in the environment because they can contaminate humans through food chains, affecting metabolic process and causing health diseases to the population. A large amount of radionuclides is produced as waste during the process of nuclear facility operation, maintenance, and decommissioning. Wastewater contains many radioactivemetal ions. During the last three decades, after Chernobyl accident and then that of Fukushima, several techniques have been developed for the removal of radionuclides from the environment and from wastewater aiming of inertization. One of the most recent techniques, and in continuous progress, is the radionuclides removal by adsorption using natural and/or synthesized materials having high retention capacity and being resistant to radiation. The most used type of material, cheap and easy-to-find, is zeolite due to its high ion exchange capacity, adsorption efficiency and abundance. This work concerns a preliminary study on zeolites identification for the removal of radionuclides in wastewater samples from the fuel storage of the former nuclear power plant of Latina, Italy. The activity concentration of the radionuclides in the samples was investigated by γ- and α-spectrometry. The wastewater samples contain the radionuclides 137Cs, 60Co and 241Am, and the best solution for their removal was discovered to be the zeolite A. The obtained results can be enlarged to all former Italian nuclear facilities.

Study on Stiffened-Plate Structure Response in Marine Nuclear Reactor Operation Environment

As the regulations on greenhouse gas emissions at sea become strict, efforts are being made to minimize environmental pollutants emitted from fossil fuels used by ships. Considering the large sizes of ships in conjunction with securing stable supplies of environment-friendly energy, interest in nuclear energy to power ships has been increasing. In this study, the neutron irradiation that occurs during the nuclear reactor operation and its effect on the structural responses of the stiffened-plate structures are investigated. This is done by changing the material properties of DH36 steel according to the research findings on the neutron-irradiated steels and then performing the structural response analyses of the structures using analytical and finite-element numerical solutions. Results reveal the influence of neutron irradiation on the structural responses of the structures. It is shown that both the strength and stiffness of the structures are affected by the neutron-irradiation phenomenon as their maximum flexural stress and deflection are increased with the increase in the amount of neutron irradiation. This implies that strength and stiffness need to be considered in the design of ships equipped with marine nuclear reactors.

A Comparison of Three Types of Computer-Based Procedures: An Experiment Using the Rancor Microworld Simulator

The nuclear power industry has historically used paper-based procedures, but a shift towards computer-based procedures (CBPs) has the potential to reduce human errors, alleviate mental workload, and improve work performance. Twenty-seven participants were randomly assigned to one of three CBP types using the Rancor Microworld Simulator, and each performed two different types of operational scenarios (startup and loss of feedwater). The three CBP types varied in levels of digitalization. It was hypothesized that there would be less favorable impressions of the most basic procedures, and that these would demonstrate lower usability than types with greater digitalization. Overall, our predictions were partially supported with some interesting caveats, specifically with some performance benefits for CBPs that provided indicators but not embedded controls. We discuss our findings in terms of optimal levels of digitalization/automation within nuclear operations and suggest pathways for future directions.

Relations of Microstructural Attributes and Strength-Ductility of Zirconium Alloys with Hydrides

As the first safety barrier of nuclear reactors, zirconium alloy cladding tubes have attracted extensive attention because of its good mechanical properties. The strength and ductility of zirconium alloy are of great significance to the service process of cladding tubes, while brittle hydrides precipitate and thus deteriorate the overall performance. Based on the cohesive finite element method, the effects of cohesive strength, interfacial characteristics, and hydrides geometric characteristics on the strength and ductility of two-phase material (zirconium alloy with hydrides) are numerically simulated. The results show that the fracture behavior is significantly affected by the cohesive strength and that the overall strength and ductility are sensitive to the cohesive strength of the zirconium alloy. Furthermore, the interface is revealed to have prominent effects on the overall fracture behavior. When the cohesive strength and fracture energy of the interface are higher than those of the hydride phase, fracture initiates in the hydrides, which is consistent with the experimental phenomena. In addition, it is found that the number density and arrangement of hydrides play important roles in the overall strength and ductility. Our simulation provides theoretical support for the performance analysis of hydrogenated zirconium alloys during nuclear reactor operation.

Reflection on and construction of the legal regimes of nuclear damage compensation in China: a policy analysis perspective

This paper explores the legal policy of nuclear damage compensation laws. As a specialised sector of nuclear law, the legal regimes on nuclear civil liability aim to provide timely and effective compensation to third parties, while also addressing the special policy concern of ensuring the sustainable development of the global or national nuclear industry. The paper examines the international methods of establishing major principles of liability with the corresponding rules and regimes to balance the interests of the parties involved. Comparatively, there is great uncertainty surrounding Chinese rules and principles of nuclear liability. Therefore, this paper suggests accelerating the enactment of a Chinese law specifically addressing nuclear damage compensation, aligning it with the national strategy and prospects of civil nuclear energy in China. Additionally, issues closely related to nuclear damage compensation, such as nuclear insurance policies, operation and supervision of national public funds and the use of alternative dispute resolution to settle nuclear disputes, are also discussed.

Prediction of stress-fatigue life on the impeller of the reactor coolant pump based on fluid-thermal-structure interaction method

The reactor coolant pump (RCP) is the core part of the first loop in nuclear power plant. It plays a crucial role on the stability and security of the nuclear reactor operation. As the only rotating equipment in the RCP, the impeller needs to run tens of thousands of cycles in the high-temperature and high-pressure coolant, which significantly affects the physical properties and reduces the fatigue life. This paper mainly studies the law of the dynamic stress on impeller of the RCP based on the fluid-thermal-structure interaction method, further predicting the stress-fatigue life of the impeller based on the Palmgren-Miner theory. The results show that the impeller is subjected to periodic alternating stress during rotation. The stress value gradually increases with the increase of the flow. The location and value of the maximum stress on the impeller at each moment are inconsistent. The highest negative correlation between the stress amplitude and the fatigue life is found, and the correlation is more than 19%. Fatigue failure first occurs at the junction between the inlet edge of the blade and the hub, and the fatigue life on the impeller is calculated to be 146.6 years. The fatigue life of the impeller is greater than the designed life, thus characterizing the impeller safe for use in nuclear power plant.

Radiation Safety Awareness and Practice among Radiology Staff in Kabul National Specialty Hospitals

In the world, more than ten million photographs and hundreds of thousands of nuclear medicine operations are performed daily. The exposure of such a large population even at the low dose levels used in diagnostic radiology due to definite effects and the possibility of ionizing radiation has caused public concern. This study aimed to determine the awareness of radiology staff from X-Rays adverse effects and the extent of use of safety measures in their practice in Kabul National hospitals. Methodology: A cross-sectional descriptive study was conducted among 60 radiology staff in national specialty hospitals of Kabul Afghanistan. A structured multiple-choice questionnaire was used. Data were coded and analyzed using the statistical package for social science (SPSS) software. Results: 83.3% of participants were male. 71% of the participants had >40 years old and the mean age of them was 41 years old. The type of job of participants was radiology technician. The mean of the years of job experience was 16 years. The knowledge or awareness of 95.0 % of participants was weak and 5.0% was intermediate. 96.7% of participant's practice was good and 3.3 % was intermediate. Conclusion: The level of awareness of 95.0 % of radiology staff was very poor. This is of concern as technologists are the first point of contact with the patients and they should be adequately trained to answer common patient questions and concerns. The level of practice of 3.3 % of the staff was intermediate and 96.7% was good. Based on our results, a conscientious effort to provide a more robust education and acquire greater knowledge in these matters is required.

Understanding the relationship between safety culture and safety performance indicators in U.S. nuclear waste cleanup operations

The relationship between nuclear safety culture and safety performance remains uncertain due to the limited research directly comparing these two variables. This study aimed to help address that gap in knowledge by evaluating the relationships between safety culture traits and two types of performance measures – personal safety and operations indicators – for a U.S. nuclear waste cleanup contractor.Data for 29 performance indicators were correlated with data measuring workforce perceptions on safety culture traits defined by the Institute of Nuclear Power Operations (INPO). Correlation and regression analyses indicated statistically significant relationships between safety culture traits and multiple organizational key performance indicators related to safety, quality and cost savings. Higher scores on safety culture traits were more closely associated with key performance indicators related to the evaluation and resolution of safety concerns, the recognition and accurate categorization of self-revealing and self-identified issues, and emergency response actions. The results suggest that while management strategies to improve safety culture may be linked to key performance indicators that strengthen overall organizational performance, these same strategies may also indirectly degrade the work environment in other areas. These research findings can help managers and safety professionals establish key performance indicators and safety culture metrics that are meaningful indicators of safety performance and inform action plans that improve productivity, enhance workplace safety, and avoid unintended consequences.

Radiation Safety Awareness and Practice among Radiology Staff in Kabul National Specialty Hospitals

Background and Aim: In the world, more than ten million photographs and hundreds of thousands of nuclear medicine operations are performed daily. The exposure of such a large population even at the low dose levels used in diagnostic radiology due to definite effects and the possibility of ionizing radiation has caused public concern. This study aimed to determine the awareness of radiology staff from X-Rays adverse effects and the extent of use of safety measures in their practice in Kabul National hospitals. Methodology: A cross-sectional descriptive study was conducted among 60 radiology staff in national specialty hospitals of Kabul Afghanistan. A structured multiple-choice questionnaire was used. Data were coded and analyzed using the statistical package for social science (SPSS) software. Results: 83.3% of participants were male. 71% of the participants had >40 years old and the mean age of them was 41 years old. The type of job of participants was radiology technician. The mean of the years of job experience was 16 years. The knowledge or awareness of 95.0 % of participants was weak and 5.0% was intermediate. 96.7% of participant's practice was good and 3.3 % was intermediate. Conclusion: The level of awareness of 95.0 % of radiology staff was very poor. This is of concern as technologists are the first point of contact with the patients and they should be adequately trained to answer common patient questions and concerns. The level of practice of 3.3 % of the staff was intermediate and 96.7% was good. Based on our results, a conscientious effort to provide a more robust education and acquire greater knowledge in these matters is required.

Achieving Minimum Deterrence: A New Dyadic Dataset on Strategic Nuclear Weapons Delivery Capabilities

This paper argues that existing quantitative studies mistakenly assume that all nuclear states can impose nuclear destruction on opponents by simply distinguishing nuclear states from non-nuclear states. This practice, however, does not capture variation in 1) nuclear states’ possession of delivery capabilities, 2) the range of deployed nuclear delivery systems, and 3) the geographic distance between nuclear states and their dyadic counterparts. Instead of this monadic nuclear statehood approach, I propose the dyadic nuclear reach approach, which uses a new dyad-specific measure of states’ strategic nuclear delivery capabilities. It codes whether a nuclear state can launch a nuclear strike against a given opponent by using the information about the estimated range of each nuclear state’s strategic nuclear delivery platforms, nuclear operation bases, and states’ capital cities. An empirical application shows that using an appropriate measure of nuclear capabilities does significantly alter existing empirical knowledge of nuclear weapons and international conflict.

False data injection attack detection for nuclear reactor based on chaotic time/frequency-hopping spread spectrum

False data injection (FDI) attacks represent a serious threat to securing nuclear reactor operation. Efficient FDI attack detection is essential to prevent related unforeseen nuclear accidents. However, owing to their design principles, the existing detection methods are limited in their ability to detect multiple types of FDI attacks. To address this issue, we propose a detection scheme for FDI attacks on a nuclear reactor based on the chaotic time/frequency-hopping (TH/FH) spread spectrum. The proposed scheme uses frequency hopping modulation, demodulation, and filtering of the signal based on hyper-chaotic sequences to limit the attacker's access to the system's real data and eliminate the adverse effects of attacks on the system. Furthermore, theoretical analysis derives the stability constraint of the frequency hopping frequency and demonstrates the detectability and defendability of the proposed scheme. Experimental simulations demonstrated that our proposed scheme can detect two typical FDI attacks, replay attacks and covert attacks, without compromising system operation, and defend against and reproduce covert attack signals.

Dispatch analysis of flexible power operation with multi-unit small modular reactors

The relevance of nuclear power plant flexible power operation (FPO) is rising due to increased penetration of variable renewables. Small Modular Reactors (SMRs) such as NuScale are envisaged to have multiple units on one site. This provides opportunities for coordinating FPO between units, but also introduces challenges as common services (e.g., refueling equipment) must be shared between units and fuel loadings may be standardized. It is therefore important to quantify whether FPO with SMRs is economically beneficial. This paper quantifies the economics of FPO on different timescales to analyze refueling outages of such multi-unit SMRs. A 24-h price-taker profit maximization of SMR operation is first solved considering revenues from wholesale power and ancillary service (AS) markets. The results are then used to find the most profitable operation strategy over several years for multiple units at the site accounting for the physics and materials limits on NPP operation, including refueling outages. Results show a small but appreciable participation of nuclear into AS, contributing 4% of revenues. Due to the longer fuel cycle, over a decade of operation the units’ refueling outages drifted by 3 months, ultimately leading to refueling during summer.

Cyber hardening of Nuclear Power Plants with real-time nuclear reactor operation, 1. Preliminary operational testing

Maintaining and extending the lifetime of the domestic Nuclear Power Plant fleet is predicated on digitalization. However, digitalization also gives rise to increasing vulnerabilities. This paper is the first in a body of novel research at the Idaho Falls Center for Higher Education focusing on the cyber hardening of currently operating and aging Nuclear Power Plants that uses the Western Services Corporation Generic Pressurized Water Reactor real-time operational platform. The Western Services Corporation platform was used here natively to collect data during atypical plant events that could be initiated by cyberattacks. The goals of this first phase of work is to identify data ‘fingerprints’ unique to each of the initiating events, determine when or if the reactor trips, and suggest operator actions that could mitigate the cyberattack and possibly avoid a trip and maintain operations. First, a cyber-informed Preliminary Hazards Analysis was conducted to determine plant systems most vulnerable to a cyberattack. Then, the associated malfunction as an analogue to a potential cyberattack on the selected system was executed during operation of the reactor. Relevant data was collected during these events until the reactor tripped. The data was then processed to determine if a fingerprint could be crafted, and mitigating operator actions were formulated. Finally, we demonstrate a proof-of-concept for simulating cyberattacks on the Western Services Corporation platform in real-time during reactor operation. This development will open possibilities for ‘Red Team/Blue Team’ exercises for cyber hardening of the domestic Nuclear Power Plant fleet.

Human-machine interface (HMI) assessment in the nuclear control room operations using the modified machine learning (ML) algorithm

Human-machine interface (HMI) assessment in the nuclear control room operations using the modified machine learning (ML) algorithm

Main Parameters Influencing the Level of Labile Contamination and the Removal Factor

Abstract Several nuclear facilities are currently being decommissioned in France, on CEA and EDF sites. The decommissioning process as a whole, with cutting operations and nuclear waste management presents workers with significant risks of exposure. The aim of this study was therefore to improve risk assessments of internal exposure in operations where the main uncertainties are the removal factor and the airborne release factor. A new method is presented to assess the risk of internal exposure and optimize the choice of personal protective equipment to use during nuclear dismantling operations. The main forces and parameters influencing the level of labile contamination and particle resuspension were identified from a literature review and feedback. A manageable set of parameters was then obtained based on literature data and on-site information. The effects of the drying temperature, relative humidity, roughness of the contaminated surface, and wiping pressure were thus investigated on labile contamination and removal factor measurements. Successive wipings with cotton pads were performed on surfaces contaminated with simulated contaminants to estimate the influence of the different parameters. Results highlight the importance of surface roughness over the other considered parameters.

Prediction of inter-granular crack initiation susceptibility in post irradiated grade 300 steels

Grade 300 austenitic steel components are subjected to irradiation-assisted stress corrosion cracking hazard, in the context of nuclear pressurized water reactor operation. In this paper, it is assumed that inter-granular cracking susceptibility primarily depends on sub grain plasticity mechanisms, controlling the slip band thickness and spacing achieved for a plastic strain level imposed. A computational model evaluating the related grain-boundary stress evolutions is developed and evaluated, using actual post-irradiation observations. In practice, we calculate a quantitative damage susceptibility factor R depending on the characteristic local slip band arrangements and the grain to grain misorientation. The statistical R evolutions obtained are consistent with the strain localization and related intergranular crack susceptibility trends, under corresponding irradiation and deformation conditions.

The development of prediction model on irradiation embitterment for low Cu RPV steels

The development of prediction model on irradiation embitterment (PMIE) of reactor pressure vessel (RPV) is an important method for nuclear reactor long term operation. Based on the physical mechanism of RPV irradiation embrittlement, a preliminary model is determined and the critical threshold of Cu content of 0.072% is obtained according to this preliminary model. Then a prediction model named PMIE-2020 for low Cu RPV steels is developed. At last the residual, standard deviation and predicted values and test values distribution analysis are given. Simultaneously, a comparison between PMIE-2020 and other prediction model and irradiation data is provided. Results indicate that the predicted results of PMIE-2020 has no tendency with influence factors such as neutron fluence, flux, irradiation temperature, chemical elements Cu, P, Mn, Ni, Si. The residual standard deviation is 10.76 °C, which is lower than present prediction model. The distribution between predicted values of PMIE-2020 and test values are located the area near the 45° line. These results prove that the PMIE-2020 have high accuracy on irradiation embrittlement prediction.

Heuristics for Multi-Vehicle Routing Problem Considering Human-Robot Interactions

Autonomous mobile robots (AMRs) are being used extensively in civilian and military applications for applications such as underground mining, nuclear plant operations, planetary exploration, intelligence, surveillance and reconnaissance (ISR) missions and manned-unmanned teaming. We consider a multi-objective, multiple-vehicle routing problem in which teams of manned ground vehicles (MGVs) and AMRs are deployed respectively in a leader-follower framework to execute missions with differing requirements for MGVs and AMRs while considering human-robot interactions (HRI). HRI studies highlight the costs of managing a team of follower AMRs by a leader MGV. This paper aims to compute feasible visit sequences, replenishments, team compositions and number of MGV-AMR teams deployed such that the requirements for MGVs and AMRs for the missions are met and the routing, replenishment, HRI and team deployment costs are at minimum. The problem is first modeled as a a mixed-integer linear program (MILP) that can be solved to optimality by off-the-shelf commercial solvers for small-sized instances. For larger instances, a variable neighborhood search algorithm is offered to compute near optimal solutions and address the challenges that arise when solving the combinatorial multi-objective routing optimization problem. Finally, computational experiments that corroborate the effectiveness of the proposed algorithms are presented.

Prognosis of wear-out effect on of safety equipment reliability for nuclear power plants long-term safe operation

Prognosis of wear-out effect on of safety equipment reliability for nuclear power plants long-term safe operation