Page 235 - Dynamics and Control of Nuclear Reactors

234 CHAPTER 16 Nuclear plant instrumentation

16.6.3 Molten salt reactor instrumentation
Molten salt power reactors are candidates for future implementation, but at the time
of preparing this book, they were still in the design and development stage. Fig. 16.18
shows the conceptual layout of the main instrumentation in a molten salt demonstra-
tion reactor (MSDR) [13].
The schematic shows placement of process sensors in the primary, secondary,
and tertiary loops, as well as ex-vessel neutron detectors. Most of the required mea-
surement are the same as in earlier plants, but MSR conditions (high temperature, salt
chemistry, and use of thorium) dictate the use of some different sensor technologies.
Various options for chemical processes to separate uranium, thorium and protactin-
ium into different streams and handling are under consideration. The chemical pro-
cesses selected in an MSR design will require appropriate instrumentation.
Temperature measurements will rely on thermocouples (type-N) because temper-
atures are above the limit for RTD use. Pressure and flow measurements are made
using standard instrumentation with sensing lines from process points to transmitter
locations. Modern magnetic flow meters are sensitive enough for use in molten salt
systems.
Ex-vessel neutron detectors as used in other nuclear power plants would be appli-
cable in a similar configuration in MSRs. Most ex-vessel neutron detectors span the
active fuel length and are placed around the top half and bottom half of the reactor
vessel. Generally, there is a set of four detectors in the top half and another set of four
detectors in the bottom half, placed symmetrically around the reactor vessel; thus, the
reactor power can be monitored radially as well as axially.
Monitoring of chemical processes occurs in all types of power reactors but is
much more important in MSRs. MSRs may be viewed as chemical plants in which
nuclear fission occurs and produces heat. Fig. 16.18 shows locations in various salt
loops where chemical composition measurements are made.
A review of instrumentation for advanced reactors is presented in Ref. [14].

References
[1] J.M. Harrer, J.G. Beckerley, Nuclear Power Reactor Instrumentation Systems Handbook,
vol. 1, TID-25952-P1, National Technical Information Service, U.S. Department of
Commerce, Springfield, VA, 1973.
[2] J.M. Harrer, J.G. Beckerley, Nuclear Power Reactor Instrumentation Systems Handbook,
vol. 2, TID-25952-P2, National Technical Information Service, U.S. Department of
Commerce, Springfield, VA, 1974.
[3] H.M. Hashemian, Maintenance of Process Instrumentation in Nuclear Power Plants,
Springer-Verlag, Berlin, Germany, 2006.
[4] H.M. Hashemian, Monitoring and Measuring I&C Performance in Nuclear Power Plants,
International Society of Automation, Research Triangle Park, NC, 2014.
[5] T.W. Kerlin, L.F. Miller, H.M. Hashemian, In-situ response time testing of platinum
resistance thermometers, ISA Trans. 17 (4) (1978) 71–88.