Thermal Hydraulic Analysis Towards a Robust Design of Leak Collection Tray for Pool Type Sodium Cooled Fast Reactors

To protect the sodium cooled FBR plant against the hazardous effects of sodium leak into the ambient, one of the passive protection devices used is the Leak Collection Trays (LCT) below the secondary sodium carrying pipelines in the Steam Generator Building (SGB). The design of LCT is based on immediate channeling of burning liquid sodium on the funnel shaped ‘sloping cover tray’ to the bottom ‘sodium hold-up vessel’ in which self-extinction of the fire occurs due to oxygen starvation. In the secondary heat transfer circuits of FBRs, leakage of liquid sodium from the pipelines is postulated as one of the design basis accidents with probability of occurrence at 10−2 per reactor year. LCT collect the leaked sodium in a hold up vessel, suppress the sodium fire due to oxygen starvation and guide the sodium to an inerted ‘sodium transfer tank’ located at the bottom most elevation of the SGB. The procedure of draining the leaked sodium into the transfer tank has been envisaged as a defense in depth measure against the handling of un-burnt sodium and to guard against larger leak rates than that can be handled by the LCT effectively. Towards this, a network of carbon steel pipelines are laid out connecting all the LCT and the transfer tank through headers in strategic locations, each having a fusible plug. The fusible plug separates the air environment in LCT and argon environment in sodium transfer tank. Woods metal is the preliminary choice for the fusible plug. It is an alloy of 50% Bi, 25% Pb, 12.5% Sn and 12.5% Cd with a melting point of 72°C. The transfer tank is filled with argon at ∼ 0.03 bars-g pressure. Both the header and the tank are at room temperature during normal conditions. Leaked sodium by virtue of its high temperature has to heat up the fusible plug to melt the same and drain into the transfer tank. Transient thermal hydraulic investigations have been carried out to predict the fusing characteristics of woods metal plug. The numerical results have been validated against analytical solutions for idealized conditions. Detailed parametric studies have been carried out with plug thickness as a parameter. It is established that effective melting of the plug and trouble free draining of the leaked sodium is possible for a 3 mm thick fusible plug.

Sodium transfer from endolymph through a luminal amiloride-sensitive channel

An in vitro preparation of frog semicircular canal was devised to study the mechanisms of Na transport across the labyrinthine epithelium. When the lumen of the semicircular canal was filled with perilymph-like solution, the structure was able to secrete K into and to absorb Na from the lumen and to generate a lumen-positive transepithelial potential. When the lumen of the semicircular canal was filled with endolymph-like solution, the electrochemical composition of the luminal fluid was partly maintained up to 2 h. In this last experimental condition net and unidirectional fluxes were calculated in absence or presence of transport inhibitors, separately for the ampulla and for the nonampullar part of the canal. Amiloride (10(-5) M) but not dimethyl amiloride (10(-5) M) inhibited 60% of the unidirectional Na efflux out of endolymph; this Na efflux decrease resulted in an increase of the inward net Na flux. The net Na flux was also increased after abluminal application of ouabain (10(-3) M), furosemide (10(-4) M), and bumetanide (10(-6) M). This study validates this isolated preparation as a suitable tool for the study of endolymph secretion, confirms that the secretion of endolymph is achieved in the ampulla, and provides evidence for an apical amiloride-sensitive Na channel through which Na is transferred out of endolymph along an electrochemical gradient provided by the activity of the abluminal Na+-K+-ATPase.

Peritoneal Equilibration Test

Peritoneal transfer rates of urea, creatinine, glucose, protein potassium, and sodium as well as drain and residual volumes were measured during 103 equilibration tests performed in 18 diabetic and 68 nondiabetic patients. Equilibration test was performed over a 4-hour dwell exchange with 2 L of 2.5% Dianeal solution. Excellent reproducibility was seen after tests were standardized for length of preceding exchange, times of inflow and drainage, patient position, methods of obtaining and processing samples and laboratory assays. Diabetics did not have lower peritoneal solute transfers than nondiabetics. Wide variations were found in the study population. Measurements of creatinine, glucose and sodium transfer were particularly useful in predicting the patient's response to the standard CAPO. The patients with highaverage peritoneal solute transport did well on standard CAPO even after losing residual renal function. Patients with high peritoneal solute transfer rates were likely to have inadequate ultrafiltration on standard CAPO. These patients did much better on dialysis modalities with short dwell exchanges, i.e. nightly peritoneal dialysis (NPO) or daytime ambulatory peritoneal dialysis (OAPO). Patients with low average, and particularly low peritoneal transport rates were likely to develop symptoms and signs of inadequate dialysis as their residual renal function became negligible, particularly in individuals with high body surface area. Repeated tests were helpful in evaluating causes of insufficient ultrafiltration and/or inadequate dialysis.

Effect of Oxygen on Sodium Transfer across the Isolated Frog Skin

1. The effect of high oxygen pressures on sodium transport across the isolated frog skin was investigated. 2. No effect on sodium transport was found when the skin was exposed to oxygen at 2 atmospheres pressure for 1 h.

The Measurement of Bidirectional Sodium Fluxes across the Intestinal Wall in Man Using Whole Gut Perfusion

1. Double-tracer studies have been carried out in order to investigate the validity of a whole-gut perfusion technique for the measurement of gut lumen-to-plasma and plasma-to-gut lumen sodium fluxes in man. 2. The use of two tracers permits differentiation between the unabsorbed orally administered sodium in the stools and the sodium which has been absorbed and resecreted. The latter is by no means negligible and may amount to some 30% of the recovered material. 3. The available data do not permit the calculation of the absolute values of the bidirectional fluxes without the introduction of some assumption concerning the reabsorption of the sodium which crosses from the plasma to the gut lumen. It is assumed here that this sodium is absorbed by the gut to the same extent as the orally administered material. Analysis of the kinetics of sodium transfer from mouth to stool direct and via the blood plasma in normal subjects and patients with diarrhoea provided experimental evidence confirming the correctness of this assumption. 4. In eleven normal volunteers the gut lumen-to-plasma flow of sodium averaged 13.0 mmol min−1, implying that the observed absorption averaging 1.65 mmol min−1 represents a relatively small imbalance between the bidirectional fluxes. Although one patient with post-gastrectomy dumping syndrome had high fluxes and another with malabsorption following gut resection gave low values, it is suggested that changes in the fluxes in the same patient are more significant than isolated observations on individuals. 5. Granted the validity of the primary assumption, a considerably simpler technique may be used for clinical and field studies which is sufficiently accurate for most purposes and employs a single tracer.