11 research outputs found
Dokumentation SSYST-1: Ein Programmsystem zur Beschreibung des LWR-Brennstabverhaltens bei Kuehlmittelverluststoerfaellen
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Two-dimensional temperature distributions in fuel rods under blowdown conditions
In the case of a loss-of-coolant accident (LOCA) in a light water reactor, the fuel rod cladding may reach temperatures which cause ballooning and rupture. To investigate the potential azimuthal temperature difference on the surface, a series of calculations were performed using the FRAP-T4 (Fuel Rod Analysis Program Transient) computer code. FRAP-T4 is capable of simulating the state of fuel rods during a LOCA, in particular the two-dimensional (r - theta) temperature distribution. Most of the effects relevant to LOCA behavior are modeled in the code. The calculations were performed for a fuel rod typical of a 17 x 17 pressurized water reactor (PWR) fuel assembly subjected to simplified blowdown thermal hydraulic conditions
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Fuel relocation as deduced from the gas flow resistance and thermal behavior of Halden Assembly IFA-430. [BWR; PWR]
The relationship of axial gas flow and fuel temperature measurements to fuel cracking and relocation occurring during the first month of irradiation of light water reactor fuel rods is discussed. Two types of fuel rod axial gas flow tests were used to determine the effective hydraulic diameter and its change during the ramping operations. Fuel centerline and off-center measurements are compared with the results of the gas flow analysis and pretest FRAP calculations
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Influence of gas pressure and composition on fuel temperature observed in the USNRC/Halden assembly IFA-430
A series of fuel behavior experiments have been conducted in the Heavy Boiling Water Reactor in Halden, Norway, to assess the effects of fuel rod internal fill gas pressure and composition on fuel temperature. Fill gases composed of He, 90% He/10% Xe, and 95% He/5% Xe at pressures from 0.1 to 5.0 MPa, were introduced into two light water reactor (LWR) design fuel rods in the Instrumented Fuel Assembly 430. These two fuel rods are connected to a gas flow system which allows the fill gases to be exchanged during nuclear operation. The two rods are identical in design except for fuel-cladding gap sizes, which are 0.1 and 0.23 mm
Early versus delayed neonatal administration of a synthetic surfactant: the judgment of Osiris
Although exogenous surfactants are of known efficacy in the prevention and treatment of respiratory distress syndrome (RDS), questions remain about the best regimens. During 1990-91, 6774 babies were recruited to an international multicentre trial to assess when administration of Exosurf, a synthetic surfactant should be started and how often it should be given. The clinical outcome is known for 6757 (99.7%) infants. 2690 babies, judged to be at high risk of RDS when less than 2 hours of age, were randomly allocated to either early administration or delayed selective administration; 96% versus 73% received surfactant, at median ages of 118 and 182 min. The risk of death or dependence on extra oxygen at the expected date of delivery was 16% (95% Cl 25% to 7%) lower among infants allocated early administration. Early administration was also associated with a 32% lower risk of pneumothorax. These 2690 infants were further randomised in a factorial design to either two doses of surfactant 12 hours apart, or the option of third and fourth doses at 12-36 hour intervals if signs of RDS persisted or recurred. 4067 other infants who later developed RDS were also recruited to this comparison, giving a total of 3376 infants allocated up-to-four doses (of whom, 45% received more than two) and 3381 allocated two doses. The outcome was similar in the two groups in respect of death, long-term oxygen dependence, and other major morbidity, even in secondary analyses restricted to infants who met the criteria for additional administration. There were more reports of poorly tolerated administration in the up-to-four doses group but no clear increase in serious morbidity, such as pulmonary haemorrhage. The OSIRIS trial suggests that early administration of surfactant to an estimated 32 babies, when compared with treatment of established RDS, would prevent 1 baby from dying and another from being dependent on extra oxygen long-term, but would entail the additional use of surfactant in 8 of these babies. It provides no evidence that a regimen including the option of third and fourth doses when signs of RDS persist or recur is clinically superior to a regimen of two doses