Safe operating temperature simulation

Two separate models based on Dow Advanced Continuous Simulation Language (DACSL) were used in these studies. The first model used laboratory data and parameter estimation to determine the Arrhenius constants for two desired and eight undesired reactions in a process. The second model used the Arrhenius constants, heats of reaction, different physical properties, and reactor parameters (volume, heat transfer properties, jacket control parameters, jacket inlet temperature) to simulate the effect of reaction conditions (concentration, set temperature, addition rate) on the temperature of the reaction mixture, pressure and gas flow rates in the reactor, yield, and assay of the product. The program has been successfully used in two scale-ups where the optimum safe operating conditions, effect of various possible failures, and control of possible abnormal conditions were evaluated. 

There are two main approaches to determining whether the plant operating temperature is safe simulation and calculation. 

Worst-case analysis based on the DSC data, namely, the test with the lowest onset temperature, resulted in a graph showing the relationship between initial temperature and time-to-maximum rate under adiabatic conditions. For an initial temperature of 170°C, it would take 2 hours to reach the maximum rate. Venting simulation tests were undertaken on a larger scale to detect safe venting requirements for the separator and for the MNB hold tank. Several vent sizes were tested. It was found that a 10-cm rupture disc with a burst pressure 1 bar above the operating pressure was adequate. 

Fire-Safe Valves that handle flammable fluids may have additional safety-related requirements for minimal external leakage, minimal internal (downstream) leakage, and operability during and after a fire. Being fire-safe does not mean being totally impervious to fire, but a sample valve must meet particular specifications such as American Petroleum Institute (API) 607, Factory Mutual Research Corp. (FM) 7440, or the British Standard 5146 under a simulated fire test. Due to very high flame temperature, metal seating (either primary or as a backup to a burned-out elastomer) is mandatory. 

One is the secondary- coolant reduction test by partial secondary loss of coolant flow in order to simulate the load change of the nuclear heat utilization system. This test will demonstrate that the both of negative reactivity feedback effect and the reactor power control system brings the reactor power safely to a stable level without a reactor scram, and that the temperature transient of the reactor core is slow in a decrease of the secondary coolant flow rate. The test will be perfonned at a rated operation and parallel-loaded operation mode. The maximum reactor power during the test will limit within 30 MW (100%). In this test, the rotation rate of the secondary helium circulator will be changed to simulate a temperature transient of the heat utilisation system in addition to cutting off the reactor-inlet temperature control system. This test will be performed under anticipated transients without reactor scram (ATWS). 

The simulation results confirm the estimated maximum temperature allowing safe reactor operation. The conversion is slightly higher (X = 0.78) than predicted on the basis of an isothermal reactor operation at 318 K. This is because of the temperature peak near the reactor entrance. To complete the reaction a second reactor operating at higher temperature is needed. As the inlet concentration of the second reactor is relatively low (cj g 1 kmol m ) temperature control is facilitated. 

The calculated DNBR is shown in Figure 10. The simulations predict a boiling crisis at a height close to 25 cm. All values are above the MDNBR (Table 1), indicating a safe reactor operation. The lowest DNBR value occurs when all the parameters (pressure, mass flux and temperature) reach their maximum values, as expected. 

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