Ralph M. Singer

The experimental breeder reactor II inherent shutdown and heat removal tests — results and analysis

Abstract A test program is being conducted to demonstrate that a power-producing liquid-metal reactor (LMR) can (1) passively remove shutdown heat by natural convection, (2) passively reduce power in response to a loss of reactor flow, and (3) passively reduce power in response to a loss of the balance-of-plant heat sink. Measurements and pretest predictions confirm that natural convection is a reliable, predictable method of shutdown heat removal and suggest that safety-related pumps or pony motors are not necessary for safe shutdown heat removal in an LMR. Measurements from tests in which reactor flow and heat rejection to the balance of plant were perturbed show that reactivity feedbacks can passively control power and temperature. Data from these tests form a basis for additional tests including a complete loss of flow without scram and a complete loss of heat sink without scram.

Evolution of thermal-hydraulics testing in EBR-II

Abstract A thermal-hydraulics testing and modeling program has been underway at the Experimental Breeder Reactor-II (EBR-II) for 12 years. This work culminated in two tests of historical importance to commercial nuclear power, a loss of flow without scram and a loss of heat sink without scram, both from 100% initial power. These tests showed that natural processes will shut EBR-II down and maintain cooling without automatic control rod action or operator intervention. Supporting analyses indicate that these results are characteristic of a range of sizes of liquid metal cooled reactors (LMRs), if these reactors use metal driver fuel. This type of fuel is being developed as part of the Integral Fast Reactor Program at Argonne National Laboratory. Work is now underway at EBR-II to exploit the inherent safety of metal-fueled LMRs with regard to development of improved plant control strategies.

On the role of inert gas in incipient boiling liquid metal experiments

Abstract In experimental studies which measure the amount of liquid superheat required to nucleate the liquid alkali metals, a considerable amount of conflicting and for the most part, unexplained data have been presented. The incipient superheat has been shown or postulated to be affected by the pressuretemperature history, liquid velocity, pressure, heat-flux, liquid purity, dissolved gas content, surface conditions, particle radiation, heating method, length of a time of operation, and perhaps others. This paper presents a theoretical study of the effect of inert gas on incipient superheats and illustrates that among other things, the gas diffusion from surface cavities into the liquid solution accounts for the so-called “heat-flux effect”. On the basis of this study, it was determined that almost all of the published data do not include sufficient information to adequately characterize the experimental systems. The non-specification of the inert gas partial pressure in the gas cover blanket, for example, can cause an uncertainty in the incipient superheats as large as 100°C.

Approximate solution of the transient free convection laminar boundary layer equations

ZusammenfassungEs wird eine angenäherte Lösung der Gleichungen der laminaren Grenzschicht in freier Konvektionsströmung an einer halbunendlichen senkrechten Platte angegeben. Obwohl bereits Ähnlichkeitsvariablen für die transiente Strömung dieses Typus angegeben wurden, ist bis heute kein numerisches Ergebnis bekannt. Daher wird im vorliegenden Aufsatz das System der nichtlinearen, gekoppelten partiellen Differentialgleichungen durch Approximation gelöst. Durch ein Integrationsverfahren kann das System der Differentialgleichungen mit drei unabhängigen Variablen (zwei Ortskoordinaten und Zeit) auf ein solches mit zwei unabhängigen Variablen zurückgeführt werden. Das so verbleibende Gleichungssystem wird auf zwei verschiedene Arten behandelt. Die eine wird als eine “Methode der Integralrelationen” bezeichnet, die andere als “Linienmethode” (ein Verfahren der Differenzenrechnung). Nach beiden Methoden werden für verschiedene Prandtl-Zahlen Geschwindigkeits- und Temperaturprofile berechnet und mit experimentellen Ergebnissen verglichen.

Numerical simulation of seismic sloshing of LMR reactors

Abstract Numerical simulations of EPRI/CRIEPI sloshing experiments have been performed by Argonne National Laboratory using the ANL-developed FLUSTR computer code. The number of meshes used in the mathematical model for numerical simulation is rather small. Thus, the computing cost is relatively inexpensive. Results of numerical simulations of the sloshing responses of two test configurations (1 and 2) which were performed by CRIEPI are described in detail. Natural frequencies and sloshing wave heights and fluid pressures at locations of sensors are calculated. The predicted values are compared with the experimental data. In all comparisons, the agreement is very good. Thus, these computer codes can be used for numerical simulation of seismic sloshing.

A fault-tolerant sensory diagnostic system for intelligent vehicle application

A properly designed automotive sensor monitoring and diagnostic system must be capable of detecting and distinguishing sensor and component malfunctions in the presence of signal noise, varying vehicle operating conditions and multiple faults. The technique presented in this paper addresses these objectives through the implementation of a multivariate state estimation algorithm based upon pattern recognition methodology coupled with a statistically-based hypothesis test. Utilizing a residual signal vector generated from the difference between the estimated and measured current states of a system, disturbances are detected and identified with statistical hypothesis testing. Since the hypothesis testing utilizes the inherent noise on the signals to obtain a conclusion and the state estimation algorithm requires only a majority of the sensors to be functioning to ascertain the current state, this technique has proven to be quite robust and fault-tolerant. Several examples of its application are presented.

Studies of thermal-hydraulic phenomena in EBR-II

Abstract An experimental and theoretical program has been undertaken during the past several years with the objective of developing a well-documented understanding of steady-state and transient thermal-hydraulic behavior in EBR-II. The results of this effort have provided reactor designers and system modelers with needed integral-type demonstrations of important phenomena. This paper will discuss the particular problems of steady-state and transient hot channel peaking factors and plant operational characteristics impact upon natural circulation dynamics. Direct in-core experimental measurements have demonstrated that factors used for the prediction of peak coolant temperature rises at normal rated plant conditions may not be conservative due to pin-bundle distortions or inlet flow maldistributions, while those applied during loss-of-flow transients are most likely overconservative due to inter- and intrasubassembly phenomena. The importance of somewhat controllable parameters such as the sequence of primary and secondary pump trips and reactor scram, primary pump rundown times, and nominal operational power-to-flow ratio upon the dynamics of the transition from forced to natural convective flow are also presented.

The Vaporization of Superheated Sodium in a Vertical Channel

Measurements of the vapor growth patterns and rates following the nucleation of superheated sodium in a vertical rectangular channel are presented and discussed. The vapor was found to grow as a single bubble for incipient bulk-liquid superheats greater than about 10 deg C, and this single bubble tended to completely fill the channel cross section (except for a thin liquid film on the walls) and to grow as a vapor slug for incipient bulk-liquid superheats greater than about 50 deg C. The temperature gradients in the liquid both normal and parallel to the channel axis prior to nucleation were found to have an important effect upon the dynamics of the vapor slug. Experimental data on the vapor growth and collapse rates and the associated pressure transients are presented for boiling pressures up to 1 atm and incipient superheats up to about 180 deg C.

Experimental study of the transition from forced to natural circulation in EBR-II at low power and flow

A series of tests was conducted in EBR-II which examined the dynamics of the transition from forced to natural circulation flow in a liquid-metal-cooled fast breeder reactor. Each test was initiated by abruptly tripping an electromagnetic pump which supplies 5--6 percent of the normal full operational primary flow rate. The ensuing flow coastdown reached a minimum value after which the flow increased as natural circulation was established. The effects of secondary system flow through the intermediate heat exchanger and reactor decay power level on the minimum in-core flow rates and maximum in-core temperatures were examined.

Transient magnetohydrodynamic flow and heat transfer

ZusammenfassungEs wird die zeitabhängige Strömung einer elektrisch leitenden Flüssigkeit untersucht, die sich bei Gegenwart eines Quermagnetfeldes einstellt, und zwar wird die freie und die erzwungene Konvektion berechnet. Wenn die Wandtemperatur längs der Kanalachse linear variiert, werden die Grundgleichungen linear, was eine analytische Lösung ermöglicht. Unsteitigkeiten können entstehen durch Variationen des axialen Druckgradienten, der Wandtemperatur oder der inneren Energieerzeugung. Die Einflüsse der thermischen und magnetischen Prandtlzahl, der Hartmannzahl, der Rayleighzahl und der inneren Energieerzeugung auf die Strömung und den Wärmeübergang werden untersucht. Für grosse Werte vonRa undM und fürPr-Werte von der Grössenordnung 1 wird ein Schwingungsverhalten gefunden, dessen Periode stark von den genannten Parametern abhängt.