Induced nuclear reactions: processes – systems – and elements – Testing – sensing – measuring – or detecting a fission reactor... – Flux monitoring
Patent
1997-02-27
1998-07-28
Wasil, Daniel D.
Induced nuclear reactions: processes, systems, and elements
Testing, sensing, measuring, or detecting a fission reactor...
Flux monitoring
376215, 395 24, 395915, G21C 17108
Patent
active
057871388
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for supervision of a neutron flux detector in the reactor core of a nuclear reactor comprising a plurality of neutron flux detectors.
BACKGROUND OF THE INVENTION
A core in a nuclear reactor comprises a plurality of fuel assemblies. These are arranged vertically in the core in spaced relationship to each other. A fuel assembly comprises a plurality of vertical fuel rods, each of which contains a stack of circular-cylindrical pellets of a nuclear fuel, arranged in a cladding tube. The core is immersed into water which serves both as coolant and as neutron moderator. The reactor core also comprises a plurality of control rods which, by being inserted into and withdrawn from the core, control the reactivity of the core and hence its output power.
A boiling-water nuclear reactor (BWR) comprises a large number of neutron-sensitive detectors, so-called LPRM (Linear Power Range Monitor) detectors. The core comprises, regularly spaced from each other, a plurality of detector tubes, each one comprising four LPRM detectors placed at four different levels in the vertical direction. The detectors, which form a regular lattice in the core, measure the neutron flux which is directly proportional to the power. The output signals from the detectors are used as a basis for supervising the core and calculating the margins of the reactor and are connected to different safety functions. It is, therefore, important that any faults in the detectors be discovered and that the faulty detector be identified as soon as possible.
The LPRM detectors comprise a fissile material for detection of the neutron flux. When the detector is subjected to neutron irradiation, the fissile material is consumed, which means that the detector deflection is changed with time. The reduction of fissile material in the detectors is different for different detectors and depends on the amount of radiation to which the detector has been exposed. To compensate for this, the detectors are calibrated at regular intervals, approximately once every month. For this purpose, a movable neutron-sensitive detector, a so-called TIP detector (Traveling Incore Probe) is used, which is inserted through all the detector tubes in the core. The TIP detector measures the neutron flux at the same locations in the tube at which the LPRM detectors are placed. These TIP measured values are used as reference values and all the LPRM detectors are adjusted so as to coincide with the TIP measured values.
The LPRM measurements contain a high degree of noise. In addition, the detectors operate under extremely difficult conditions where the risk of faults arising in the detectors is relatively high. The LPRM detectors are filled with gas, for example argon. A frequently occurring fault is that a crack in the detector causes the gas slowly to leak out, which in turn causes the detector to drift. This type of fault is difficult to discover and requires that the output signals from the detector be studied for a long period of time.
The method currently used for supervising the LPRM detectors compares the output signals from the detectors with calculated values from a core simulator. This method has many uncertainties since the calculated values may be subjected to both model faults and faults in the input signals to the calculations. If the output signal from a detector differs from the calculated value, it may be difficult to determine whether there is a fault in the detector or a fault in the calculated value.
The LPRM detector may also be supervised by studying the output signal from the detector for a long period to see whether the detector is drifting or is otherwise defective. This method is not completely reliable either since it does not take into consideration whether the operating conditions have been changed during the period studied.
SUMMARY OF THE INVENTION
The invention aims to provide a method for supervision of a neutron detector in a reactor core, which method on the one hand indicates that the detector is
REFERENCES:
patent: 5023045 (1991-06-01), Watanabe et al.
patent: 5311562 (1994-05-01), Palusamy et al.
patent: 5349541 (1994-09-01), Alexandro, Jr. et al.
patent: 5581459 (1996-12-01), Enbutsu et al.
patent: 5623579 (1997-04-01), Damiano et al.
The Electrical Engineering Handbook, pp. 420-429, editor Richard C. Dorf, 1993, CRC Press.
Ocieczek Grzegorz
Tiusanen Mika
ABB Atom AB
Wasil Daniel D.
LandOfFree
Supervision of a neutron detector in a nuclear reactor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Supervision of a neutron detector in a nuclear reactor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Supervision of a neutron detector in a nuclear reactor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-29194