Dynamic Modeling

Introduction to Dynamic Modeling

The inherent safety and stability of a nuclear reactor is poorly appreciated in the public’s mind. Many fear nuclear power because of a mistaken belief that a well-designed reactor can undergo a nuclear explosion leading to the scattering of radioactive material. In reality, there are innate physical processes taking place in a reactor that help give it a significant measure of stability and control. Of course, the impact of these processes vary from one reactor design to another. The liquid-fluoride thorium reactor (LFTR) is quite different from today’s reactors due to its use of liquid fuel rather than solid fuel, and thorium rather than uranium. Liquid fuel is outside of the base of experience of most nuclear engineers, and they might be forgiven for thinking that it is less safe than solid fuel, but the reality can be quite the opposite.

Actual analysis is a powerful tool for dispelling fears and doubts about a new technology. The successful operation of the Molten-Salt Reactor Experiment (MSRE) at Oak Ridge National Lab (ORNL) from 1965 to 1969 serves as an “existence proof” that liquid-fluoride reactors can operate safely and in a stable manner. Although the MSRE did not incorporate thorium in its fuel, it served as a technology precursor for liquid-fluoride thorium reactors that we hope will follow.

Objective and Background

Our objective is to build a dynamic model of a liquid-fluoride reactor that will serve as a testbed for various simulated “excursions” as well as a design tool through which new concepts for LFTRs can be tested and evaluated. In so doing, we are retracing a thread of work that was done at ORNL fifty years ago.

Our logical point-of-departure is the dynamic analysis work that was done to support the MSRE. Some of this was captured in the form of design documents which we will use to begin the dynamic modeling effort. One of the most important is ORNL-TM-1070 (Stability Analysis of the Molten-Salt Reactor Experiment), published in December 1965. Through study and emulation of ORNL-TM-1070, we anticipate that a preliminary dynamic model of a liquid-fluoride reactor can be built using modern tools like MATLAB and SIMULINK.

Actual operation of the MSRE starting in 1965 gave ORNL engineers an opportunity to check the prediction of their TM-1070 model against the real reactor. The results of this testing were reported in ORNL-TM-1647 (Experimental Dynamic Analysis of the MSRE), published in October 1966.

Part of the original plan for the MSRE involved testing the reactor using uranium-233 as fuel. This is important because a thorium reactor would use uranium-233 as fuel, and uranium-233 has different performance properties from uranium-235 fuel. Therefore, ORNL engineers revisited the TM-1070 model again to prepare for U-233 use and detailed the changes in ORNL-TM-2571 (Theoretical Dynamic Analysis of the MSRE with 233U Fuel), published in July 1969. After operations on uranium-233 fuel, they were again able to compare theory and actual results in ORNL-TM-2997 (Experimental Dynamic Analysis of the MSRE with 233U Fuel), published in April 1970.

Beyond the MSRE, ORNL engineers considered the performance of a large-scale power-generating reactor design they called the Molten-Salt Breeder Reactor (MSBR). They undertook preliminary work on the MSBR dynamic response in ORNL-TM-2927 (Control Studies of 1000-MWe MSBR) published in May 1970.


ORNL-MSR-73-7: A Catalog of Dynamics Analyses for Circulating-Fuel Reactors, February 7, 1973 (2.1M PDF)

Experiences with Dynamic Testing Methods at the MSRE, Nuclear Applications and Technology, 10 2 (February 1971).

Theoretical Dynamics Analysis of the MSRE, Nuclear Applications and Technology, 10 2 (February 1971).

ORNL-TM-3229: Fluid Dynamic Studies of the MSRE Core, November 1970 (2.6M PDF)

ORNL-TM-2997: Experimental Dynamic Analysis of the MSRE with 233U Fuel, April 1970 (1.2M PDF)

ORNL-TM-2571: Theoretical Dynamic Analysis of the MSRE with 233U Fuel, July 1969 (2.2M PDF)

ORNL-MSR-67-102: Preliminary Dynamics Model of the MSBR, November 30, 1967 (1.7M PDF)

ORNL-TM-1647: Experimental Dynamic Analysis of the MSRE, October 13, 1966 (2.4M PDF)

ORNL-TM-1070: Stability Analysis of the MSRE, December 1965 (4.9M PDF)

ORNL-TM-0203: MURGATROYD–An IBM 7090 Program for the Analysis of the Kinetics of the MSRE, April 1962 (12.8M PDF)

ORNL Central Files

ORNL-CF-66-2-67: Analysis of MSRE Zero-Power Flux Noise Using Digital Techniques, February 1966 (2.8M PDF)

ORNL-CF-65-10-18: Results of Neutron Fluctuation Measurements Made During the MSRE Zero-Power Experiment, October 1965 (1.4M PDF)

ORNL-CF-65-8-32: Preliminary Report on Results of MSRE Zero-Power Experiments, August 1965 (4.2M PDF)

ORNL-CF-62-11-69: Preliminary Equations to Describe Iodine and Xenon Behavior in the MSRE, November 1962 (1.5M PDF)

ORNL-CF-61-12-50: MSRE Analog Computer Simulation of the System with a Servo Controller, December 1961 (2.6M PDF)

ORNL-CF-61-10-39: Delayed Neutron Losses in Circulating Fuel Reactors – MSCR Memo No. 6, October 1961 (0.4M PDF)

ORNL-CF-60-11-20: MSRE – Analog Computer Simulation of a Loss of Flow Accident in the Secondary System, November 1960 (1.1M PDF)

ORNL Internal Memoranda

ORNL-MSR-73-7: 1973-02-07 (2.1M PDF)
A Catalog of Dynamics Analyses for Circulating-Fuel Reactors

Correspondence dated 1968-05-27 (0.3M PDF)
Status of Analysis of Dynamic Tests Performed on MSRE at the End of Operation with 235U Fuel

Correspondence dated 1968-02-05 (0.3M PDF)
Test of MSRE Rod Control System Under Simulated 233U Fuel Loading Conditions

ORNL-MSR-68-24: 1968-01-30 (2.3M PDF)
Xenon Behavior in Recent Tests in the MSRE

Correspondence dated 1968-01-25 (0.1M PDF)
MIT Practice School Problem – Test of MSRE Rod Controller with Simulated 233U Fuel Loading

ORNL-MSR-68-21: 1968-01-17 (0.4M PDF)
Proposed Program for Stability Analysis and Dynamic Testing of the MSRE for the 233U Fuel Loading

Correspondence dated 1968-01-10 (0.1M PDF)
Tests of MSRE Rod Control System in Preparation for 233U

ORNL-MSR-68-5: 1967-12-21 (0.7M PDF)
Proposed Test of MSRE Rod Control System Under Simulated 233U Fuel Loading Conditions

Correspondence dated 1967-12-14 (0.4M PDF)
MSRE External Loop Dynamics Transfer Function Derivation

ORNL-MSR-67-102: 1967-11-30 (1.7M PDF)
Preliminary Dynamics Model of the MSBR

ORNL-MSR-67-96: 1967-11-07 (0.1M PDF)
Acceptability of NaK-Filled Pressure and Differential Pressure Transmitters for Use on the MSBR

ORNL-MSR-67-29: 1967-05-12 (1.1M PDF)
Xenon-135 Poison Fraction for MSBR Reference Design

ORNL-MSR-67-2: 1967-01-06 (1.0M PDF)
Reactor Dynamics Information from MSRE Operation with 233U-Bearing Fuel Salt

ORNL-MSR-66-2: 1966-03-07 (0.9M PDF)
Operating History of the MSRE Digital, Data-Collecting and Computer System

Correspondence dated 1965-10-08 (0.1M PDF)
Future Neutron Fluctuation Measurements at the MSRE

Correspondence dated 1964-12-14 (0.2M PDF)
Documentation of Critical and Subsequent Experiments on the MSRE

ORNL-MSR-64-41: 1964-10-12 (0.3M PDF)
MSRE Simulator for Operator Training

Correspondence dated 1964-06-04 (0.2M PDF)
MSRE Operator Training

ORNL-MSR-64-14: 1964-04-17 (1.6M PDF)
On-Line Computation of Control Rod Effect for Reactivity Balance

ORNL-MSR-63-49: 1963-12-19 (1.0M PDF)
Proposed MSRE Dynamic Tests

Correspondence dated 1963-05-02 (0.5M PDF)
Analysis of MSRE Cooling Water Temperature Control System

Correspondence dated 1963-04-08 (0.6M PDF)
Analog Study of MSRE Component Cooling Pump Differential Pressure Controller (PdIC-960A)

ORNL-MSR-62-96: 1962-12-29 (0.9M PDF)
Preliminary Study of an Automatic Rod Controller Proposed for the MSRE

Correspondence dated 1962-12-17 (1.5M PDF)
MSRE Drain Times

ORNL-MSR-62-86: 1962-09-27 (6.4M PDF)
MSRE Rod Controller Simulation – Week of 6-25-62

Hand Notes from Syd Ball:

MSRE Analog Circuit

MSRE Charcoal Trap

MSRE Computer Programs

MSRE Cooling Water System

MSRE Dynamic Tests 1

MSRE Dynamic Tests 2

MSRE Fill Accident Simulation

MSRE Hot Valve Problem

MSRE Power Oscillations

MSRE Radiator Freeze

MSRE Rod Controller

MSRE Roots Blower Control

MSRE Surveillance Rig

MSRE Temperature Measurement

MSRE Training Simulator