The role of BWR secondary containments in severe accident mitigation: Issues and insights from recent analyses

All commercial boiling water reactor (BWR) plants in the US employ primary containments of the pressure suppression design. These primary containments are surrounded and enclosed by secondary containments. While not designed for severe accident mitigation, these secondary containments might also reduce the radiological consequences of severe accidents. This issue is receiving increasing attention due to concerns that BWR MK I primary containment integrity would be lost should a significant mass of molten debris escape the reactor vessel during a severe accident.The fission product retention capability of an intact secondary containment will depend on several factors. Recent analyses indicate that the major factors influencing secondary containment effectiveness include: the mode and location of the primary containment failure, the internal architectural design of the secondary containment, the design of the standby gas treatment system, and the ability of fire protection system sprays to remove suspended aerosols from the the secondary containment atmosphere. Each of these factors interact in a very complex manner to determine secondary containment severe accident mitigation performance.This paper presents a brief overview of US BWR secondary containment designs and highlights plant-specific features that could influence secondary containment severe accident survivability and accident mitigation effectiveness. Current issues surrounding secondary containment performance are discussed, and insights gained from recent secondary containment studies of Browns Ferry, Peach Bottom, and Shoreham are presented. Areas of significant uncertainty are identified and recommendations for future research are presented.     

Endoscopic CO2 laser excision of large or recurrent laryngeal saccular cysts in adults

BACKGROUND: Most paediatric cardiac arrest studies have been conducted in the USA, where paramedics provide prehospital emergency care. We wanted to study the outcome of paediatric cardiac arrest patients in an emergency medical system which is based on physician staffed emergency care units. METHODS: We analysed retrospectively the files of 100 prehospital cardiac arrest patients from Southern Finland during a 10-year study period. The patients were less than 16 years of age. RESULTS: Fifty patients were declared dead on the scene (DOS) without attempted resuscitation, and cardiopulmonary resuscitation (CPR) was initiated in 50 patients. The sudden infant death syndrome was the most common cause of arrest in the DOS patients (68%) as well as in those receiving CPR (36%). Asystole was the initial cardiac rhythm in 70% of the patients in whom CPR was attempted. Resuscitation was successful in 13 patients, 8 of whom were ultimately discharged. Six of the patients survived with mild or no disability and 4 of them had near-drowning aetiology. In multivariate analysis, the short duration of CPR (< or = 15 min) was the only factor significantly associated with better survival. CONCLUSIONS: Although prehospital care was provided by physicians, the overall rate of survival was found to be equally poor as reported from systems with paramedics. The only major difference between physician- and paramedic-staffed emergency care units is the ability of physicians to refrain from resuscitation already on the scene when prognosis is poor.     

Follicular vascularity--the predictive value of transvaginal power Doppler ultrasonography in an in-vitro fertilization programme: a preliminary study

The glnA gene from the human pathogen Streptococcus agalactiae was cloned from a genomic library prepared with the lambda phage vector lambdaDASHII. A 4.6-kb DNA fragment of one of the recombinant phages was subcloned in pUC18. This Escherichia coli clone expressed a 52-kDa protein encoded by a 1,341-bp open reading frame. The nucleotide sequence of the open reading frame and the deduced amino acid sequence shared a significant degree of homology with the sequences of other glutamine synthetases (GS). The highest homology was between our deduced protein and GS of gram-positive bacteria such as Bacillus subtilis, Bacillus cereus, and Staphylococcus aureus. Plasmids with the cloned streptococcal glnA were able to complement E. coli glnA mutants grown on minimal media. Rabbit antisera to streptococcal GS recombinant protein recognized not only the recombinant protein but also a similar-sized band in mutanolysin extracts of all group B streptococcal strains tested, regardless of polysaccharide type or surface protein profile. The amino acid sequence of the deduced protein had similarities to other streptococcal cell-surface-bound proteins. The possible functional role of the immunological features of streptococcal GS is discussed.     

Multifactorial analysis of lung cancer dose-response relationships for workers at the Mayak nuclear enterprise

Dose-response relationships for alpha-radiation-induced lung cancers (adenocarcinoma, squamous carcinoma and small cell carcinoma) were developed by multifactorial analysis using data for Mayak nuclear enterprise workers chronically exposed by inhalation to 239Pu. The three most important lung cancer risk factors (smoking, plutonium incorporation, and external gamma irradiation), out of six factors previously identified, were used. Relative risks (odds ratios) were determined for 500 nuclear enterprise workers (162 cancer cases, 338 control) for different dose levels using a case-control study design and logistic regression. A threshold at about 3.7 kBq or 0.80 Gy was discovered for incorporated plutonium, which is satisfactorily described by linear-quadratic and quadratic models. Excess relative risk was 0.020 kBq(-2) and 0.97 Gy(-2). This quadratic function was mainly due to adenocarcinoma. A trend for decreasing risk was noted for the lowest levels of plutonium incorporation, near permissible level. No clear-cut dose-response relationship for lung cancer induction by chronic external gamma irradiation was obtained. Lung cancer induction by cigarette smoking had a linear dependence: smoking of one pack of papiroses (a type of Russian cigarette) per day for 5 y increases the lung cancer risk twofold. The effect was most clearly manifested for squamous-cell carcinoma.     

Indium phosphide and quaternary doping superlattices grown by liquid-phase epitaxy

Stacks containing from 20 to 100 alternating n and p-layers, each less than 100 nm thick, have been produced by liquid-phase epitaxy in both InP and in the quaternary alloy Int?x GaxAsyP1?y. Increasing the excitation intensity shifts the photoluminescence (PL) towards shorter wavelengths by the expected magnitude. Hetero-nipi quaternary structures displaying two PL peaks have also been grown. The relative intensities of the two peaks depend strongly on the excitation intensity.     

High power operation of GaInAsP/GaInAs MQW ridge lasers emitting at 1.48 mu m

Multi-quantum-well (MQW) ridge lasers have been produced with CW light outputs in excess of 100 mW at 500 mA. The wavelength of operation is 1480 nm and the lasers are suitable for pumping erbium-doped-fibre amplifiers. These are the highest power ridge lasers yet produced in the 1500 nm wavelength region.<>     

Oxidation of Inconel 718 in Air at High Temperatures

Experiments were conducted with Inconel 718 at high temperatures to evaluate the rate of oxidation of the material over as wide a temperature range as possible, as well as to determine the high-temperature failure limit of the material. Samples of Inconel 718 were inserted into preheated furnaces at temperatures ranging from 973 to 1620 K and oxidized in air for varying periods of time. After being oxidized in air at a constant temperature for the prescribed time and then being allowed to cool, the samples were reweighed to determine their mass gain due to the uptake of oxygen. From these mass-gain measurements, it was possible to identify three regimes of oxidation for Inconel 718: a low-temperature regime in which the samples behaved as if passivated after an initial period of transient oxidation, an intermediate-temperature regime in which the rate of oxidation was limited by diffusion and exhibited a constant parabolic rate dependence, and a high-temperature regime in which material deformation and damage accompanied an accelerated oxidation rate above the parabolic regime.