The Heavy-Section Steel Irradiation Program at Oak Ridge National Laboratory includes a task to investigate the propensity for temper embrittlement in coarse grain regions of heat-affected zones in prototypic reactor pressure vessel (RPV) steel weldments as a consequence of irradiation and thermal annealing. For the present studies, five prototypic RPV steels with specifications of A302 grade B, A302 grade B (modified), A533 grade B class 1, and A508 class 2 were given two different austenitization treatments and various thermal aging treatments. Thermal aging treatments were conducted at 399, 425, 454 and 490 degreesC for times of 168 and 2000 h. Charpy V-notch impact toughness vs temperature curves were developed for each condition with ductile-brittle transition temperatures used as the basis for comparing the effects of the various heat treatments. Very high austenitization heat treatment produced extremely large grains which exhibited a very high propensity for temper embrittlement following thermal aging. Intergranular fracture was the predominant mode of failure in many of the materials and Auger analysis confirmed significant segregation of phosphorus at the grain boundaries. Lower temperature austenitization treatment performed in a super Gleeble to simulate prototypic coarse grain microstructures in submerged-arc weldments produced the expected grain size with varying propensity for temper embrittlement dependent on the material as well as on the thermal aging temperature and time. Although the lower temperature treatment resulted in decreased propensity for temper embrittlement, the results did provide motivation for the investigation of the potential for phosphorus segregation as a consequence of neutron irradiation and post-irradiation thermal annealing at 454 degreesC. One of the A 302 grade B (modified) steels was given the Gleeble treatment, irradiated at 288 degreesC to about 0.8 x 10(19)n/cm (>1 MeV) and given a thermal annealing treatment at 454 degreesC for 168 h. Charpy impact testing was conducted on the material in both the irradiated and irradiated/annealed conditions, as well as in the as-received condition. The results show that, although the material exhibited a relatively small Charpy impact 41-J temperature shift, the heat-affected zone-simulated material did exhibit significant intergranular fracture in the post-irradiation annealed condition.

A new method to determine fracture toughness KIC of materials is introduced. A round‐rod specimen having a V‐grooved spiral line with a 45° pitch is tested under pure torsion. An equibiaxial tensile/compressive stress state is effectively created to simulate conventional test methods using a compact‐type specimen with a thickness equivalent to the full length of the spiral line. KIC values are estimated from the fracture load and crack length with the aid of a three‐dimensional finite element analysis. KIC of 7475‐T7351 aluminium is estimated to be 51.3 MPa √m, which is higher than the vendor’s value in the TL orientation by ∼0.8% and higher than 0.5T compact tension (CT) value by 6%; A302B steel yields 54.9 MPa √m being higher than CT test value by ∼2%. Good agreement between the KIC values obtained by different methods indicates the proposed method is sound and reliable.

The crack-arrest fracture toughness (K-a) of unirradiated and irradiated specimens machined from a low upper-shelf, high-copper weld was determined. The specimens were machined from the beltline weld of the Midland Unit 1 nuclear reactor pressure vessel (RPV). This weld was fabricated from one heat of weld win and one lot of welding flux and bears the designation WF-70. It is of particular interest because it has been used in several RPVs that may still be in operation. The effect of irradiation has been measured in terms of the shift of the mean and lower-bound crack-arrest fracture toughness versus temperature cut-yes. These shifts are compared to (1) 41-J transition temperature shift from Charpy V-notch (CVN) tests, Delta TT41-J; (2) shift in the Master Curve transition temperature, T-0, at the 100 MPa.root m level, Delta T-0; and (3) shift of the "arrest force" F-a temperature determined from instrumented CVN testing, Delta TFa. Preliminary results indicate that the shift of K-a of this low upper-shelf energy weld is approximately the same as the shift Delta TT41-J, larger than Delta T-0, and significantly larger than Delta TFa.

An American Society for Testing and Materials (ASTM) standard method (E 1921-97) has been developed that exclusively uses fracture mechanics test practices and advanced statistical methods to establish the ductile-to-brittle transition range of fracture toughness for structural steels. The development of suitably accurate analyses had been slowed in the past due to an incomplete understanding of the operational mechanisms that control the fracture toughness behavior of structural steels. New perspectives taken are (1) that dominant linear-elastic conditions need not be rigidly enforced in specimens and (2) that the effect of specimen size on fracture toughness performance is mostly controlled by a weakest-link mechanism instead of being completely controlled by crack tip constraint conditions. The weakest-link behavior is defined from local cleavage crack initiators such as precipitates, inclusions, and grain boundary embrittlement, namely, all microstructural features in steel. Statistical models can be built upon such mechanisms that result in defined fracture probability levels and, when coupled to a master curve concept, can more accurately define the true location of the ductile-to-brittle transition temperature. An integral part of the ASTM test standard development work has been the production of a supporting technical basis document. This document presents substantial background data and supporting theoretical aspects that have been used to justify the method development. The paper will include some of the salient features presented.

The influence of irradiation damage and recovery of properties by thermal annealing for low upper-shelf WF-70 weld metal has been evaluated. The test material was obtained from the beltline and nozzle course girth welds of the Midland Unit 1 reactor pressure vessel. The two welds, ostensibly made with the same heat of weld wire and the same lot of submerged-are flux, were determined to be separable for evaluations by virtue of differing copper contents. Conventional transition temperature methods of drop-weight nil-ductility transition and Charpy V-notch (CVN) transition curves could not distinguish a difference in transition temperature. However, a recently developed master curve method of data evaluation revealed the difference by virtue of achieving better sensitivity using only fracture mechanics-based test data.Irradiation embrittlement after a fluence of 1.0 x 10(19) n/cm(2) was evaluated by both the conventional American Society of Mechanical Engineers (ASME) Code method and by the more recent American Society for Testing and Materials (ASTM) master curve method. Again, the Code method rated the postirradiation transition temperatures of the two materials the same. The master curve method indicated that the postirradiated properties of the two materials differed significantly. The U.S. Nuclear Regulatory Commission (NRC) Regulatory Guide 1.99, Rev. 2, reasonably predicted the experimentally obtained CVN transition temperature shift at the 41 J reference level for the beltline weld.Postirradiation annealing at 454 degrees C (850 degrees F) for 168 h almost completely restored the as-received transition temperature properties. The recovery of the transition temperature compared to unirradiated values after 343 degrees C (650 degrees F for 168-h recovery anneal was 52% by the 1 1 J CVN temperature, which conflicts with the theoretical recovery of 17% calculated by NRC Regulatory Guide 1.162. The Delta T-o from the master curve method indicated 21% recovery of transition temperature.

The Heavy-Section Steel Irradiation (HSSI) Program at Oak Ridge National Laboratory (ORNL) includes a task, the Tenth Irradiation Series, to investigate the effects of radiation on the fracture toughness of the low upper-shelf submerged-are welds in the reactor pressure vessel (RPV) of the canceled Midland Unit 1 nuclear plant. The welds carry the Babcock and Wilcox Co. (B&W) designation WF-70, a weld which exists in many commercial pressurized-water reactors. Various sections of both the beltline weld and the nozzle course weld were studied. A major part of the study involved the determination of variations in chemical composition and reference temperature (RTNDT) throughout the as-received welds. The RTNTDS, all controled by the Charpy behavior, varied from -20 to 37 degrees C (-4 to 99 degrees F) while the upper-shelf energies varied from 77 to 108 J (57 to 80 ft-lb). Even though all the welds carry the WF-70 designation, the bulk copper contents range from 0.21 to 0.34 wt % in the beltline weld and from 0.37 to 0.46 wt % in the nozzle course weld. The variation (2 sigma) of 41-J temperatures for 25 data sets of the Midland weld was 17 degrees C and is comparable to that for the high upper-shelf HSSI weld 72W and that from 13 data sets for HSST Plate 01. Statistical analyses of the Charpy and chemical composition results are discussed.Although the NDT temperatures and CVN transition temperature ranges were similar for the two welds, the fracture toughness results indicated that the nozzle course weld had a 27 degrees C (49 degrees F) higher transition temperature than the beltline weld. Some postirradiation data are available and are presented in this paper, but the major part of the irradiation effects study will be reported subsequently.

Equine influenza virus infection remains one of the most important infectious diseases of the horse, yet current vaccines offer only limited protection. The equine immune response to natural influenza virus infection results in long-term protective immunity, and is characterized by mucosal IgA and serum IgGa and IgGb antibody responses. DNA vaccination offers a radical alternative to conventional vaccines, with the potential to generate the same protective immune responses seen following viral infection. Antigen-specific antibody isotype responses in serum and mucosal secretions were studied in ponies following particle-mediated delivery of hemagglutinin (HA)-DNA vaccination on three occasions at approximately 63-day intervals. One group of four ponies were vaccinated at skin and mucosal sites and the another group were vaccinated at skin sites only. All ponies were subjected to a challenge infection 30 days after the third vaccination. Skin and mucosal vaccination provided complete protection from clinical signs of infection, while skin vaccination provided partial protection; DNA vaccination provided partial protection from viral shedding. DNA vaccination generated only IgGa and IgGb antibody responses, which occurred with a higher frequency in the skin and mucosa vaccinated ponies. No mucosal IgA response was generated prior to challenge infection and IgA responses were only detected in those ponies which shed virus postchallenge. These results demonstrate that HA-DNA vaccination induces IgG(a) and IgG(b) antibody responses which are associated with protection in the absence of mucosal IgA responses. In addition, additional DNA vaccinations of mucosal sites increased protection and the frequency of seroconversion in ponies.

The objective of this investigation is an estimation of the crack-arrest toughness, particularly of irradiated materials, from voltage versus time output of an instrumented tup during a test on a Charpy V-notch (CVN) specimen. This voltage versus time trace (which can be converted to force versus displacement) displays events during fracture of the specimen. Various stages of the fracture process can be identified on the trace, including an arrest point indicating arrest of brittle fracture. The force at arrest, F-a versus test temperature, T, relationship is examined to explore possible relationships to other experimental measures of crack-arrest toughness such as the drop-weight nil-ductility temperature (NDT), or crack-arrest toughness, K-a. For a wide range of weld and plate materials, the temperature at which F-a = 2.45 kN correlates with NDT with a standard deviation, sigma, of about 11 K. Excluding the so-called "low upper-shelf energy" (USE) welds from the analysis resulted in F-a = 4.12 kN and sigma = 6.6 K. The estimates of the correlation of the temperature for F-a = 7.4 kN with the temperature at 100-MPa.root m level for a mean American Society of Mechanical Engineers (ASME) type K-Ia curve through crack-arrest toughness values show that prediction of conservative values of K-a are possible.

The current provisions used in the U.S. Code of Federal Regulations for the determination of the fracture toughness of reactor pressure vessel steels employs an assumption that there is a direct correlation between K-Ic lower-bound toughness and the Charpy V-notch transition curve. Such correlations are subject to scatter from both approaches which weakens the reliability of fracture mechanics-based analyses. In this study, precracked Charpy and smaller size specimens are used in three-point static bend testing to develop fracture mechanics based K-Jc values. The testing is performed under carefully controlled conditions such that the values can be used to predict the fracture toughness performance of large specimens. The concept of a universal transition curve (master curve) is applied. Data scatter that is characteristic of commercial grade steels and their weldments is handled by Weibull statistical modeling. The master curve is developed to describe the median K-Jc fracture toughness for 1T size compact specimens. Size effects are modeled using weakest-link theory and are studied for different specimen geometries. It is shown that precracked Charpy specimens when tested within their confined validity limits follow the weakest-link size-adjustment trend and predict the fracture toughness of larger specimens. Specimens of smaller than Charpy sizes (5 mm thick) exhibit some disparities in results relative to weakest-link size adjustment prediction suggesting that application of such adjustment to very small specimens may have some limitations.

Polynucleotide vaccines are a new approach to immunization that promises qualitative advances in vaccine technology. These vaccines mimic infection in that they result in expression of pathogen gene products in situ, which can elicit both cell-mediated immune responses and humoral responses. This approach has been applied primarily to vaccines against viral diseases, but may be significant for vaccines directed toward bacterial pathogens. Auragen has developed a generally applicable gene transfer technology and, for vaccine applications, has focused on particle-mediated gene transfer to epidermis. Results demonstrate that Accell polynucleotide vaccines induce immune responses toward human immunodefficiency virus (HIV) antigens, influenza A virus antigens, and hepatitis B virus (HBV) antigens in rodent,s swine and primates. Cellular immune responses toward these antigens have been demonstrated in rodents. In a swine influenza a challenge model Accell vaccination provides protection equivalent to that of a commercial killed-whole-virus vaccine. Vaccination of mice by this method toward a Chlamydia pneumoniae major outer-membrane protein elicits a species-specific antibody response.

The primary objective of the Heavy-Section Steel Irradiation (HSSI) Program Tenth Irradiation Series was to develop a fracture mechanics evaluation of weld metal WF-70, which was taken from the beltline and nozzle course girth weld joints of the Midland Reactor vessel. This material became available when Consumers Power Company of Midland, Michigan, decided to abort plans to operate their nuclear power plant. WF-70 is classified as a low upper-shelf steel primarily due to the Linde 80 flux that was used in the submerged-arc welding process. The master curve concept is introduced to model the transition range fracture toughness when the toughness is quantified in terms of K{sub Jc} values. K{sub Jc} is an elastic-plastic stress intensity factor calculated by conversion from J{sub c}; i.e., J-integral at onset of cleavage instability.

Loading a cracked structure at elevated temperature, or warm prestressing (WPS), enhances its fracture resistance at a lower temperature. Five data sets, comprising 119 unclad pressure vessel steel specimens, were combined to derive correlations for WPS-enhanced fracture toughness (K I f r a c ) in the absence of ductile tearing. New WPS test results for 27 surface-flawed specimens, eight subclad-flawed specimens, and five strain-aged specimens are discussed. K I f r a c exceeded non-WPS fracture toughness, K I c , for all experiments. The WPS data showed that no specimens failed while K was decreasing, and that at least an additional 7% additional reloading from the minimum value of applied K 1 took place prior to final fracture. The data included complete and partial unloading after WPS prior to final fracture. Crack tip three-dimensional elastic-plastic finite element (3DEPFE) analysis was performed to support statistical analysis of the data. Regression models were compared with the Chell WPS model. Crack tip 3DEPFE analysis indicated that partially unloaded and completely unloaded data should be treated separately, and that the amount of unloading is unimportant for partially unloaded data. The regression models, which use K 1 at WPS (K I w p s ) and K I c as independent variables, better represented the WPS benefit than did the more complicated Chell model. An adequate accounting was made for constraint in the WPS experiments. The subclad flaw data support the use of the partial unload regression model provided that some care is taken to represent the effect of intact cladding if present. The effect of strain aging at or below 260°C (500°F) on the WPS benefit was of no consequence for the pressure vessel steels and WPS temperatures used to derive the regression models. The presence of ductile tearing precludes the use of the regression models. The regression model for partial unloading accurately predicted the behavior of full-scale pressure vessel WPS experiments. All but one of the 174 experiments considered lie above the lower 2σ estimate of the regressions. The experiments all supported Type I WPS, i.e., there was no fracture during cooling until reloading occurred. However, the regression equations apply to the reload and are inapplicable to Type I WPS.

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ASTM E-08 Committee has been developing a new standard, to deal with the fracture mechanics behavior of steels in the ductile to brittle transition region. This paper presents a comparison between the current approach and a new proposal to be used by the nuclear industry to face the problem of determining the behavior of ferritic steels. An emphasis will be given to the application of this proposal and its evaluation using a Brazilian A508 Class 3 nuclear steel.

In this work, elastic-plastic fracture mechanics (EPFM) methods are extended to study the behavior of surface cracks. The material used is a tungsten inert gas (TIG) welded 2219-aluminum alloy, welded with 2319 weld wire. Calibration and a crack-growth test were performed. A multiple specimen R-curve technique was used. A group of specimens with the same initial crack geometry was tested to different deformation values. Several different groups were considered. Crack extension as a function of position along the crack front was determined and digitized into data files. A method to estimate values of the J integral as a function of position is presented. Local resistance curves were obtained. A parameter to characterize constraint is proposed. It is only based on the elastic solution for G. It is shown that the slopes of the resistance curves are uniquely related to the constraint parameter for all cases considered.

Description Contains significant insight on the latest international developments in fracture mechanics. Central thermes are constraint issues and nonlinear fracture mechanics. Several papers also deal with the industry's most active topic of study, the two-parameter fracture mechanics approach to constraint and its impact on transition fracture toughness. 9 sections cover: • Progress in Fracture Mechanics Research • Constraint Issues • Ductile to Brittle Transition • Elastic-Plastic Fracture • High Temperature Effects • K Analysis • Applications • Fatigue • Nonmetallic Materials