Identification of an Attenuated Substrain of Francisella tularensis SCHU S4 by Phenotypic and Genotypic Analyses

Pneumonic tularemia is a highly debilitating and potentially fatal disease caused by inhalation of Francisella tularensis. Most of our current understanding of its pathogenesis is based on the highly virulent F. tularensis subsp. tularensis strain SCHU S4. However, multiple sources of SCHU S4 have been maintained and propagated independently over the years, potentially generating genetic variants with altered virulence. In this study, the virulence of four SCHU S4 stocks (NR-10492, NR-28534, NR-643 from BEI Resources and FTS-635 from Battelle Memorial Institute) along with another virulent subsp. tularensis strain, MA00-2987, were assessed in parallel. In the Fischer 344 rat model of pneumonic tularemia, NR-643 and FTS-635 were found to be highly attenuated compared to NR-10492, NR-28534, and MA00-2987. In the NZW rabbit model of pneumonic tularemia, NR-643 caused morbidity but not mortality even at a dose equivalent to 500x the LD50 for NR-10492. Genetic analyses revealed that NR-10492 and NR-28534 were identical to each other, and nearly identical to the reference SCHU S4 sequence. NR-643 and FTS-635 were identical to each other but were found to have nine regions of difference in the genomic sequence when compared to the published reference SCHU S4 sequence. Given the genetic differences and decreased virulence, NR-643/FTS-635 should be clearly designated as a separate SCHU S4 substrain and no longer utilized in efficacy studies to evaluate potential vaccines and therapeutics against tularemia.

A Pressure Reduction to Prevent a Time-Delayed Failure in a Damaged Pipeline

A time-delayed failure due to stress-activated creep (cold-creep) is a failure that occurs under a constant load and with no growth due corrosion, fatigue or some other environmentally assisted time-dependent degradation mechanism. A time-delayed failure is prevented by reducing the pressure. ASME B31.4 and B31.8 recommend a 20 percent reduction, to 80 percent of the pressure at the time of damage or discovery. T/PM/P/11 Management Procedure for Inspection, assessment and repair of damaged (non-leaking) steel pipelines, an internal procedure used by National Grid, specifies a 15 percent reduction. The guidance in ASME B31.4 and B31.8, and in T/PM/P/11, is directly or indirectly based on the results of tests on the long term stability of defects conducted by the Battelle Memorial Institute and British Gas Corporation in the 1960s and 70s. The line pipe steels were Grades X52 or X60, and the full-size equivalent Charpy V-notch impact energy (where reported) did not exceed 35 J. The tests indicated that the threshold for a time-delayed failure was approximately 85–95% SAPF (straightaway-pressure-to-failure). The strength and toughness of line pipe steels has significantly increased over the decades due to developments in steel-making and processing. The question then is whether an empirical threshold based on tests on lower strength and lower toughness steels is applicable to higher strength and higher toughness steels. In the Tripartite Project, the Australian Pipelines and Gas Association (APGA), the European Pipeline Research Group (EPRG) and the Pipeline Research Council International (PRCI) collaborated in conducting full-scale six step-load-hold tests on higher strength and higher toughness steels. Companion papers present the other aspects of this multi-year project. An empirical threshold for a time-delayed failure is estimated using the results of the six step-load-hold tests. That estimate is also informed by the other published small and full-scale tests (on lower strength and lower toughness steels). The Ductile Flaw Growth Model is used to infer the effect of strength and toughness on the threshold for a time-delayed failure. A 15 percent pressure reduction, to 85 percent of the pressure at the time of damage (or of the maximum pressure that has occurred since the time of damage), is considered to be sufficient to prevent a time-delayed failure due to stress-activated creep in lower and higher toughness, in lower and higher strength, and in older and newer line pipe steels.

Full-Scale Step-Load-Hold Tests on X65 and X70 Line Pipe Steels

A time-delayed failure due to stress-activated creep (cold-creep) will occur if the applied load is held constant at a level above the threshold. The results of small and full-scale tests on line pipe steels conducted by the Battelle Memorial Institute and the British Gas Corporation in the 1960s and 70s indicated that the (empirical) threshold for a time-delayed failure was approximately 85–95% SAPF (straight-away-pressure-to-failure). The line pipe steels were Grades X52 or X60, and the full-size equivalent Charpy V-notch impact energy (where reported) did not exceed 35 J. The strength and toughness of line pipe steels has significantly increased over the decades due to developments in steel-making and processing. The question then is whether an empirical threshold based on tests on lower strength and lower toughness steels is applicable to higher strength and higher toughness steels. A Tripartite Project was established to answer this question. The Australian Pipelines and Gas Association (APGA), the European Pipeline Research Group (EPRG) and the Pipeline Research Council International (PRCI) collaborated in conducting six full-scale step-load-hold tests on higher strength and higher toughness steels. Companion papers present the other aspects of this multi-year project. The line pipe supplied for testing is summarised below. • Identifier — Dimensions and Grade — f.s.e. Charpy V-notch impact energy at 0 C • APGA [A] — 457.0 × 9.1 mm, Grade X70M, ERW — 263 J • EPRG [E] — 1016.0 × 13.6 mm, Grade X70M, SAWL — 165 J • PRCI [P] — 609.6 × 6.4 mm, Grade X65, SAWL — 160 J Six step-load-hold tests, each with four part-through-wall defects, were conducted. Test Nos. APGA 1 and 2, and Nos. EPRG 1 and 2 were conducted at Engie, France. Test Nos. PRCI 1 and 2 were conducted at EWI, USA. The full-scale tests, and associated small-scale testing, are described and discussed. A time-delayed failure due to stress-activated creep occurred in each of the step-load-hold tests. The failures occurred during a hold-period at 93.7–104.4% SAPF, after a hold of approximately 1.0–13.9 hours. The results of the six step-load-hold tests are consistent with a threshold for a time-delayed failure of approximately 90% SAPF.

Mission Mosquito: building and expanding an international network for innovation in health communication

The Mission Mosquito Information Sharing Program (ISP), a collaboration between the U.S. Department of State and Battelle Memorial Institute, is a public diplomacy effort to build and expand an international network of health communicators to increase engagement on mosquito-borne disease. Nineteen professionals from countries experiencing mosquito-borne diseases engaged in a two-week multi-directional information exchange across the United States in May 2018. Program alumni applied knowledge and tools from the ISP in follow-on projects and public outreach campaigns in their home countries. This paper summarizes the ISP and lessons learned, and highlights a science communication case study examining skills and understanding gained.

Analysis of Two Dense Phase Carbon Dioxide Full-Scale Fracture Propagation Tests

Two full-scale fracture propagation tests have been conducted using dense phase carbon dioxide (CO2)-rich mixtures at the Spadeadam Test Site, United Kingdom (UK). The tests were conducted on behalf of National Grid Carbon, UK, as part of the COOLTRANS research programme. The semi-empirical Two Curve Model, developed by the Battelle Memorial Institute in the 1970s, is widely used to set the (pipe body) toughness requirements for pipelines transporting lean and rich natural gas. However, it has not been validated for applications involving dense phase CO2 or CO2-rich mixtures. One significant difference between the decompression behaviour of dense phase CO2 and a lean or rich gas is the very long plateau in the decompression curve. The objective of the two tests was to determine the level of ‘impurities’ that could be transported by National Grid Carbon in a 914.0 mm outside diameter, 25.4 mm wall thickness, Grade L450 pipeline, with arrest at an upper shelf Charpy V-notch impact energy (toughness) of 250 J. The level of impurities that can be transported is dependent on the saturation pressure of the mixture. Therefore, the first test was conducted at a predicted saturation pressure of 80.5 barg and the second test was conducted at a predicted saturation pressure of 73.4 barg. A running ductile fracture was successfully initiated in the initiation pipe and arrested in the test section in both of the full-scale tests. The main experimental data, including the layout of the test sections, and the decompression and timing wire data, are summarised and discussed. The results of the two full-scale fracture propagation tests demonstrate that the Two Curve Model is not (currently) applicable to liquid or dense phase CO2 or CO2-rich mixtures.

Constraint Effects in Ductile Fracture on J-Resistance Curve for Full-Scale Cracked Pipes and Fracture Toughness Testing Specimens

Fracture toughness is an important quantity in structural integrity assessment of pressurised vessels and piping. This paper reports J resistance (J-R) curves for toughness test specimens and full-scale pipes with a circumferential crack in a carbon steel. Full-scale pipes with a circumferential crack subjected to four-point bending are investigated with single edge-notched-tension specimens, SE(T), under fixed grip and pin-loaded conditions and compact tension, C(T), fracture toughness test specimens. Finite element (FE) damage analyses based on a stress-modified fracture strain model are used to simulate ductile fracture. An element-size-dependent critical damage model is introduced and applied to the large-scale components. Fracture parameter J values are calculated using both experimental data and FE analysis. In the first part of this paper, experimental results performed by Battelle Memorial Institute are compared with results from FE simulations to gain confidence in the ductile fracture simulation. Subsequently, different types of fracture toughness tests and thickness variations are considered to address the effect of in-plane and out-of plane constraint, respectively. Also, pipe geometries and crack depth are varied systematically. In conclusion, the transferability of J-R curves from toughness test specimens to full-scale cracked pipes is discussed.

Existing Methods in Ductile Fracture Propagation Control for High-Strength Gas Transmission Pipelines

Ductile fracture propagation control is one of the most important technologies adopted in engineering design for high-pressure, high-strength gas transmission pipelines. In the early 1970s, Battelle Memorial Institute developed a two-curve model that is now commonly referred to as BTCM for dynamic ductile fracture control analysis. The BTCM has been applied successfully for determining the minimum fracture toughness required to arrest a running ductile fracture in a gas transmission pipeline in terms of Charpy vee-notched (CVN) impact energy. Practice showed that BTCM is accurate only for pipeline grades up to X65, and becomes invalid for high strength pipeline steels like X70, X80 and X100. Since 1990s, different correction methods for improving the BTCM have been proposed. However, a commonly accepted method is not available yet for the high strength pipeline steels in grades X80 and above. This paper reviews and evaluates the primary existing methods in determination of fracture arrest toughness for ductile pipeline steels. These include the CVN energy-based methods, the drop-weight tear test (DWTT) energy-based methods, the crack-tip opening angle (CTOA) method, and finite element numerical analysis methods. The purpose is to identify a method to be used in engineering design or to be investigated further for determining the minimum fracture toughness to arrest a ductile running crack in a modern high-pressure, high-strength gas pipeline.

Benchmarking xLPR Version 1.0 With the PRO-LOCA Version 3.0 Code

The US Nuclear Regulatory Commission (NRC) in conjunction with the US nuclear power industry under the leadership of the Electric Power Research Institute (EPRI) is developing a new probabilistic fracture mechanics (PFM) code as a means of demonstrating compliance with the 10CFR50 Appendix A, General Design Criterion 4 (GDC-4) requirement that primary system piping exhibit an extremely low probability of rupture. This PFM code, called xLPR (eXtremely Low Probability of Rupture) will be comprehensive by addressing all aspects of the problem, i.e., crack initiation, growth, stability, surface crack detection and leakage detection. Previously, the NRC, along with two of its contractors, Battelle Memorial Institute and Engineering Mechanics Corporation of Columbus (Emc2), developed a probabilistic fracture mechanics code called PRO-LOCA[1] which was to have been used as a tool for re-evaluating the break frequency versus break size curves developed as part of the technical basis for the transition break size as part of the redefinition of the emergency core cooling system (ECCS) requirements in 10CFR50.46. PRO-LOCA was subsequently developed as part of an international cooperative research program led by Battelle called MERIT (Maximizing Enhancements in Risk-Informed Technology). Today PRO-LOCA is being further developed as part of another international cooperative program called PARTRIDGE (Probabilistic Analysis as a Regulatory Tool for Risk-Informed Decision GuidancE). The focus of this paper is three-fold. First, the relationship between PRO-LOCA and xLPR will be described. Secondly, the enhancements being made to PRO-LOCA will be discussed and compared to xLPR development. Finally, the results of some comparative cases where PRO-LOCA (Version 3.0) was benchmarked against xLPR (Version 1.0) are provided.