Data-Driven Management—A Dynamic Occupancy Approach to Enhanced Rabies Surveillance Prioritization

Rabies lyssavirus (RABV) is enzootic in raccoons across the eastern United States. Intensive management of RABV by oral rabies vaccination (ORV) has prevented its spread westward and shown evidence of local elimination in raccoon populations of the northeastern US. The USDA, Wildlife Services, National Rabies Management Program (NRMP) collaborates with other agencies to implement broad-scale ORV and conducts extensive monitoring to measure the effectiveness of the management. Enhanced Rabies Surveillance (ERS) was initiated during 2005 and updated in 2016 to direct surveillance efforts toward higher-value specimens by assigning points to different methods of encountering specimens for collection (strange-acting, roadkill, surveillance-trapped, etc.; specimen point values ranged from 1 to 15). We used the 2016–2019 data to re-evaluate the point values using a dynamic occupancy model. Additionally, we used ERS data from 2012–2015 and 2016–2019 to examine the impact that the point system had on surveillance data. Implementation of a point system increased positivity rates among specimens by 64%, indicating a substantial increase in the efficiency of the ERS to detect wildlife rabies. Our re-evaluation found that most points accurately reflect the value of the surveillance specimens. The notable exception was that samples from animals found dead were considerably more valuable for rabies detection than originally considered (original points = 5, new points = 20). This work demonstrates how specimen prioritization strategies can be used to refine and improve ERS in support of wildlife rabies management.

Fracture Toughness in Postulated Crack Area of PTS Evaluation in Highly-Neutron Irradiated RPV Steel

The Japanese Electric Association Code 4206-2016 requires that the semi-elliptical crack sized 10 mm in depth × 60 mm in length shall be postulated near the inner surface of a reactor pressure vessel (RPV) in pressurized thermal shock events. The fracture toughness distribution was investigated in the postulated crack area under the PTS events of unirradiated and highly-neutron irradiated RPV steels. Vickers hardness in heat-affected zone (HAZ) due to stainless overlay cladding and 10 mm from the cladding were higher than that of a quarter thickness position, where the surveillance specimens are machined, for both unirradiated (E1) and irradiated (up to 1 × 1020 n/cm2, WIM) materials. Fracture toughness of HAZ and 10 mm from the cladding was higher for the above highly-neutron irradiated material. The same result was obtained in the unirradiated material. Therefore, it was confirmed that fracture toughness obtained from surveillance specimens can provide conservative assessment of structural integrity of RPV.

Uncertainty determination of fast neutron fluence onto the WWER pressure vessel metal surveillance specimens

The standard surveillance programs of WWER reactors do not allow to measure the surveillance specimens irradiation conditions with the required accuracy. Therefore, the special methodology for the determination of the surveillance specimens irradiation conditions of the reactor pressure vessel metal has been developed by the specialists of the INR of NASU and is successfully applied. The developed methodology bases on the use of the Monte-Carlo code for neutron transport calculations to the surveillance specimens locations. The methodology improvement is described. The fundamentals of the calculation-experimental determination of the fast neutron fluences onto surveillance specimens and their uncertainties are presented.

Re-emergence of influenza Virus Circulation during 2020 in parts of Tropical Asia: Implications for Other Countries

Global influenza virus circulation declined and has been below traditional seasonal levels during the COVID-19 pandemic.1-3 We reviewed WHO influenza surveillance outputs from May 1-December 31, 2020 (epidemiologic weeks 18-53) from tropical Asian countries. For each country we report influenza surveillance specimens tested, and the percentage positive for influenza, by type and subtype. We compared current data to historical data from 2015-2019 in order to place the current season in historical context. Twelve included countries tested 17,407 surveillance specimens, with 592 (3.4%) testing positive for influenza viruses. From April 27-July 26, 2020 (epidemiologic weeks 18-30), specimens tested decreased from an average of 14,102 per year in 2015-2019 to 3,969 (71.9% decrease) and influenza positivity from 22% to <1%. During weeks 31-53, specimens tested decreased from an average of 24,782 per year in 2015-2019 to 13,438 (45.8% decrease) and influenza positivity from 18% to 4%. In six countries that maintained testing of surveillance specimens for >90% of weeks, influenza circulation was unseasonably low, or absent, during weeks 18-30, 2020. However, during weeks 31-53, the percentage of surveillance specimens testing positive for influenza approached or reached positivity rates of 2015-2019 in Bangladesh and Cambodia; and increased but remained lower than historical positivity in Lao PDR and Viet Nam. The data presented here are a reminder that the low levels of influenza circulation in the northern hemisphere in summer 2020 may not necessarily persist into the upcoming influenza season, and influenza surveillance and prevention strategies should continue as planned and not be delayed.

To the issue of accuracy of determination of irradiation embrittlement coefficient

The paper presents the statistical analysis of experimental results of radiation-induced critical brittle temperature ΔTF shifts and reference temperatures ΔT0 obtained respectively from the impact bend and fracture toughness tests of the reactor vessel metal surveillance specimens to define the possibility of their mutual application for the irradiation embrittlement coefficient to be determined more accurately. The correlation between these parameters is shown to remain up to the accumulation of over-design fast neutron fluence.

Non-Destructive Evaluation of RPV Embrittlement by Means of the Thermoelectric Power Method

Nondestructive evaluation (NDE) methods are widely used for inspecting safety relevant components in nuclear reactors. Most of these NDE-methods are optimized and applied for the detection of cracks but there is still no reliable NDE method for measuring the embrittlement of RPV steels. However, since the evaluation of RPV embrittlement of so-called Surveillance specimens with the Charpy test is a destructive approach, NDE methods are highly required. Among the investigated technics are acoustic (Ultrasonic scattering), electric (resistivity, thermoelectric) and magnetic (Barkhausen Noise, Non-Linear Harmonics Analysis, Micromagnetic Multiparameter) methods. However, all the methods under investigation suffer from the fact that fracture toughness of steel depends upon several factors, especially on lattice defects such as vacancies, dissolved atoms, dislocation loops, solute clusters, precipitates and dislocations. A major obstacle to the application of NDE methods for the quantification of material embrittlement is that they may be not only sensitive to these defects but also to other factors, such as magnetic, acoustic and electrical properties, as well as to surface quality and ambient temperature, etc.). In this paper, we present results gained by the optimization and application of the thermoelectric power method (TEPM) at the Paul Scherrer Institut (PSI) in Switzerland. The TEPM uses the change of the Seebeck coefficient (K) as an indicator for the material embrittlement. A clear almost linear correlation between the shift of the Nil-Ductile-Transition-Temperature (NDTT) and the change of the K was found. Beside the TEPM and its optimization with the finite element method, we describe the influencing parameters and the potential of this promising NDE method.

Study of Residual Stresses and Microstructural Changes in Charpy Test Specimens Reconstituted by Various Welding Techniques

Changes in the reactor pressure vessel (RPV) material properties due to neutron irradiation are monitored by means of surveillance specimen programs, which are used for realistic evaluation of the RPVs’ lifetime. Due to a limited number of surveillance specimens, the evaluation of reconstitution methods by various welding techniques after Charpy impact tests is of great importance. Time-of-flight (TOF) neutron diffraction method was used to determine the residual stress distributions and microstructural changes in Charpy specimens welded by arc stud, electron, and laser beam welding techniques. The lowest level of the residual stress in weld seams regions was found for the specimen welded by electron beam with optimal parameters as compared to other techniques. At the same time, this specimen exhibits the maximal level of microstrain, which points to high dislocation density in the material. The corresponding contributions to the yield strength due to various strengthening mechanisms were estimated.

Engineering Version of Local Approach to Fracture and its Application for RPV Lifetime Prediction

Theoretical basis of the simplified (engineering) version of Local Approach (LA) to fracture is summarized, and the possibility of using this version to predict the lifetime of RPV steels is demonstrated. The concept of “effective” volume, , within which stresses and strains are uniformly distributed, but the magnitude of the probability of cleavage initiation are equal to their real values at given value of , underlies the proposed engineering version of LA. A function was selected to describe the temperature dependence of local cleavage stress, and a calibration procedure was proposed for determining the constants in this dependence from the results of tests of surveillance specimens. For weld metal of WWER-1000 reactors the dependences of brittle strength on fluence were obtained, and the maximum permissible fluence values were determined. It is shown that in addition to the radiation hardening, the radiation-induced reduction in the level of brittle strength, , has a significant effect on the radiation service life of reactor pressure vessel steel.

Co-circulation of influenza A(H1N1)pdm09 and influenza A(H3N2) viruses, World Health Organization (WHO) European Region, October 2018 to February 2019

In the World Health Organization European Region, the 2018/19 influenza season started in week 49 2018, crossing 10% virus-positivity in sentinel surveillance specimens. At week 5 2019, activity remained elevated with positivity rates at 55%. Both A(H1N1)pdm09 and A(H3N2) viruses circulated widely and detection levels in primary care and hospital settings were similar to past seasons. Hospitalisation data may suggest an increased susceptibility to A(H1N1)pdm09 virus in older age groups.