Evaluation of the passage rate equations in the 2001 Dairy NRC model

Dairy ration formulation to meet protein and amino acid requirements with the National Research Council Nutrient Requirements of Dairy Cattle (NRC, 2001) model depends on accuracy of predicting feed passage rates out of the rumen. The NRC (2001) passage rate (Kp) equations were evaluated for validity and sensitivity to input variables in predicting supplies of rumen degraded protein, rumen undegraded protein, and metabolizable protein. The database used in the development of the 3 Kp equations (for dry forage, wet forage, and concentrate) was used to independently derive the 3 equations using a meta-analysis technique. To extract quantitative relationships between statistically significant input variables and rate of passage, a random coefficients model that used each study effect as a random variable was used. The database was comprised of studies that only used rare earth markers. Outliers were identified by acceptance criteria defined a priori or the difference in fit statistic (DFFITS) value; 319, 63, and 139 treatment means were used to develop the Kp equations for dry forage, wet forage, and concentrate, respectively. We found that the sign of the regression coefficient for concentrate content in diet dry matter in the equation for Kp dry forage was inverted; it should be positive. A sensitivity analysis was conducted with a spreadsheet version of the NRC (2001) model developed for this study, using the Monte Carlo technique. The sensitivity analysis indicated that all Kp predictions were the most sensitive to variation in DM intake, and thus accurate measurement of DM intake is the most important factor in predicting Kp. Predictions for protein supply (rumen degraded protein, rumen undegraded protein, and metabolizable protein) were sensitive to variability in amount of feed crude protein (CP, %DM), digestion rate (Kd) of the B fraction of feed CP (%/h), and the Kp for concentrate (%/h), due to the high proportion of dietary CP in lactating dairy rations coming from concentrates. The sensitivity analysis indicated that accurate determinations of DMI, the Kd of the B fraction of feed CP, and feed CP are the most important variables needed to predict MP supply in lactating dairy cows with the NRC (2001) model. We conclude that the empirical Kp equations in the model are suitable for predicting passage rate in lactating dairy cows. More accurate predictions of Kp will require the development of a more mechanistic model that accounts for more of the biologically important variables (e.g., physical property of particles, liquid flow, and timely variation of intake) affecting passage rate.     

Condensation heat transfer with noncondensable gas for passive containment cooling of nuclear reactors

Noncondensable gases that come from the containment and the interaction of cladding and steam during a severe accident deteriorate a passive containment cooling system's performance by degrading the heat transfer capabilities of the condensers in passive containment cooling systems. This work contributes to the area of modeling condensation heat transfer with noncondensable gases in integral facilities. Previously existing correlations and models are for the through-flow of the mixture of steam and the noncondensable gases and this may not be applicable to passive containment cooling systems where there is no clear passage for the steam to escape. This work presents a condensation heat transfer model for the downward cocurrent flow of a steam/air mixture through a condenser tube, taking into account the atypical characteristics of the passive containment cooling system. An empirical model is developed that depends on the inlet conditions, including the mixture Reynolds number and noncondensable gas concentration.     

Prediction of protein supply to ruminants from concentrates: comparison of the NRC‐2001 model with the DVE/OEB system

The objective of this study was to compare the DVE/OEB system (DVE = truly absorbed protein in the small intestine; OEB = degraded protein balance) and the NRC‐2001 model in the prediction of supply of protein to dairy cows from 46 selected concentrates: malting‐type barley (cv Harrington), feed‐type barley (cv Valier), field tick beans (Vicia faba), white albus lupins (Lupinus albus), whole soybeans and horse beans (Vicia faba cv Alfred). The two barleys were processed by coarse (roller miller, 0.533 mm gap) and fine (hammer mill, 2 mm screen) processing. The field tick beans and white albus lupins were dry roasted at various conditions at the University of Melbourne. The soybeans and horse beans were pressure‐toasted at 100, 118 and 136 °C for 3, 7, 15 and 30 min at Wageningen Feed Processing Centre. Comparisons were made in terms of (1) ruminally synthesized microbial protein, (2) truly absorbed protein in the small intestine and (3) degraded protein balance, based on 46 samples. The results showed that the predicted values from the DVE/OEB system and the NRC‐2001 model had significant correlations. However, using the DVE/OEB system, the overall average microbial protein supply based on available energy was 10% lower and the truly absorbed protein in the small intestine was 8% lower than that predicted by the NRC‐2001 model. A difference was also found in the prediction of the degraded protein balances, which was 16% higher than that estimated from the NRC‐2001 model. These differences are due to factors used in calculations in the two models, although both are based on similar principles. This indicates that further refinement is needed for a modern protein evaluation and prediction system. Copyright © 2004 Society of Chemical Industry     

A study on the effects of ESFAS STI modification on the unavailability of ESF actuated components

The nuclear industry has made so great efforts to attain safe and economically viable Nuclear Power Plants all over the world. Probabilistic Safety Assessment (PSA) applications are required now more than ever in order to operate Nuclear Power Plants.In this paper, the unavailability model of Engineered Safety Feature (ESF) actuated components, which is part of the Korean Standard Nuclear Power Plant (KSNPP) PSA model, is used to analyze the effects of Surveillance Test Interval (STI) extension of Engineered Safety Feature Actuation System (ESFAS) on the unavailability of the ESF actuated components.To develop a more accurate and realistic PSA model, the loop controller modules of Plant Control System (PCS) are also modeled on the KSNPP PSA model. The fault tree developed by each ESF actuated component includes the component failure, ESFAS signal failure, and loop controller module failure of PCS. When the ESFAS STI is extended from one month to three months, the unavailability of ESF actuated components partially increased by 10%. This shows the STI extension of ESFAS has minor effects on the unavailability of the ESF actuated components. The effects of ESFAS STI extension of KSNPP on the unavailability of the ESF actuated components as well as Core Damage Frequency (CDF) and Large Early Release Frequency (LERF) is less than expected. That result indirectly indicates that the ESFAS in KSNPP is designed well enough to extend the ESFAS STI.     

Modeling pressure suppression pool hydrodynamics in the ABWR containment

This paper focuses on the assessment of pressure suppression pool hydrodynamics in the advanced boiling water reactor (ABWR) containment under design-basis, loss-of-coolant accident (LOCA) conditions. The paper presents a mechanistic model for predicting various suppression pool hydrodynamics parameters. A phenomena identification and ranking table (PIRT) applicable to the ABWR containment pool hydrodynamics analysis is used as a basis for the development of the model. The highly ranked phenomena are represented by analytic equations or empirical correlations. The best estimate and several sensitivity calculations are performed for the ABWR containment using this model. Results of the sensitivity calculations are also presented that demonstrate the influence of key model parameters and assumptions on the pool hydrodynamics parameters. A comparison of model predictions to the results of the licensing analyses shows reasonable agreement. Comparison of the results of the proposed model to experimental data shows that the model predicted top vent clearance time, the pool swell height, and the bubble breakthrough elevation are within 10% of the data. The predicted pool surface velocity and the liquid slug thickness are within 30% of the measurements, which is considered adequate given the large uncertainties in the experimental measurements.     

Mass flow rate sensitivity and uncertainty analysis in natural circulation boiling water reactor core from Monte Carlo simulations

Our aim was to evaluate the sensitivity and uncertainty of mass flow rate in the core on the performance of natural circulation boiling water reactor (NCBWR). This analysis was carried out through Monte Carlo simulations of sizes up to 40,000, and the size, i.e., repetition of 25,000 was considered as valid for routine applications. A simplified boiling water reactor (SBWR) was used as an application example of Monte Carlo method. The numerical code to simulate the SBWR performance considers a one-dimensional thermo-hydraulics model along with non-equilibrium thermodynamics and non-homogeneous flow approximation, one-dimensional fuel rod heat transfer. The neutron processes were simulated with a point reactor kinetics model with six groups of delayed neutrons. The sensitivity was evaluated in terms of 99% confidence intervals of the mean to understand the range of mean values that may represent the entire statistical population of performance variables. The regression analysis with mass flow rate as the predictor variable showed statistically valid linear correlations for both neutron flux and fuel temperature and quadratic relationship for the void fraction. No statistically valid correlation was observed for the total heat flux as a function of the mass flow rate although heat flux at individual nodes was positively correlated with this variable. These correlations are useful for the study, analysis and design of any NCBWR. The uncertainties were propagated as follows: for 10% change in the mass flow rate in the core, the responses for neutron power, total heat flux, average fuel temperature and average void fraction changed by 8.74%, 7.77%, 2.74% and 0.58%, respectively.     

Variations of a passive safety containment for a BWR with active and passive safety systems

The paper presents variations of a certain passive safety containment for a near future BWR. It is tentatively named Mark S containment in the paper. It uses the operating dome as the upper secondary containment vessel (USCV) to where the pressure of the primary containment vessel (PCV) can be released through the upper vent pipes. One of the merits of the Mark S containment is very low peak pressure at severe accidents without venting the containment atmosphere to the environment. Another merit is the capability to submerge the PCV and the reactor pressure vessel (RPV) above the core level by flooding water from the gravity-driven cooling system (GDCS) pool and the upper pool. The third merit is robustness against external events such as a large commercial airplane crash owing to the reinforced concrete USCV. The Mark S containment is applicable to a large reactor that generates 1830 MW electric power. The paper presents several examples of BWRs that use the Mark S containment. In those examples active safety systems and passive safety systems function independently and constitute in-depth hybrid safety (IDHS). The concept of the IDHS is also presented in the paper.     

Chemical composition,fatty acid content and antioxidant potential of meat from goats supplemented with Moringa (Moringa oleifera) leaves,sunflower cake and grass hay

The present study determined the chemical composition, fatty acid (FA) content and antioxidant capacity of meat from goats supplemented with Moringa oleifera leaves (MOL) or sunflower cake (SC) or grass hay (GH). The meat from goat supplemented with MOL had higher concentrations of total phenolic content (10.62 ± 0.27 mg tannic acid equivalent E/g). The MOL significantly scavenged 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic-acid (ABTS) radical to 93.51 ± 0.19% (93.51 ± 0.19%) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical to 58.95 ± 0.3% than other supplements. The antioxidative effect of MOL supplemented meat on catalase (CAT), reduced glutathione (GSH), superoxide dismutase (SOD) and lipid oxidation (LO) was significantly (P < 0.05) higher than other meat from goat feed on grass hay or those supplemented with sunflower seed cake. The present study indicated that the anti-oxidative potential of MOL may play a role in improving meat quality (chemical composition, colour and lipid stability).     

Development and diversity and defense-in-depth application of ABWR feedwater pump and controller model

This work developed an advanced boiling water reactor (ABWR) feedwater pump and controller model, which was incorporated into Personal Computer Transient Analyzer (PCTran)-ABWR, a nuclear power plant simulation code. The feedwater pump model includes three turbine-driven feedwater pumps and one motor-driven feedwater pump. The feedwater controller includes a one-element/three-element water level controller and a specific feedwater speed controller for each feedwater pump. The performance tests, including step change of dome pressure, feedwater pumps transfer, inadvertent closure of all turbine control valves, and one feedwater pump trip at 100% power, demonstrate the feasibility of dynamic response of stand-alone model and incorporated model. Furthermore, a diversity and defense-in-depth analysis is performed to demonstrate the feasibility for motor-driven feedwater pump as an emergency core cooling system (ECCS) automatic diverse back-up. In Lungmen nuclear power plant (NPP), a diverse manual initiation means for the high pressure core flooder (HPCF) loop C is designed as the back-up of digitalized engineered safety features actuation system (ESFAS). If the motor-driven feedwater pump (MDFWP) can be an automatic digital diverse back-up for ESFAS, Lungmen NPP would be more robust to defend against software common-cause failure (CCF).     

Is bad performance the answer to saving the nuclear power industry?

Public opposition to nuclear power is an impediment for use of this energy source. The literature indicates risk perceptions are the dominant determinant of opposition. One aspect of risk involves fear of the unknown, suggesting those with more experience with nuclear mishaps should be less opposed to nuclear energy once they learn that the risk is not as bad as perceived. Evidence suggests that those who live near nuclear plants with more mishaps are more likely to support nuclear power.