Regarding Things Take
Time:
Leyse Gamma Thermometer in
ESBWR
NEDO-33197-A Revision 3
Page 157
11. REFERENCES
1. R.H. Leyse, R.D. Smith:
“Gamma Thermometer Developments for Light
Water
Reactors,” IEEE Transactions on Nuclear
Science, Vol.N5.26, No. 1, February 1979,
pp.
934–943.
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7.3.3 Conclusions
The comparison with the gamma scan
established that core monitoring based on GTs is nearly equivalent in accuracy
to core monitoring with neutron TIPs. In addition, it was shown that the thermal
limits, MCPR and MLHGR, evaluated by the two core monitoring systems were very
similar throughout the cycle.
The overall conclusion was that the GT
system is “practical as a substitute” for the TIP
system.
Method of and apparatus for measuring the power distribution in nuclear reactor cores
Abstract
The invention disclosed is the method of exact calibration of gamma ray
detectors called gamma thermometers prior to acceptance for installation into a
nuclear reactor core. This exact calibration increases the accuracy of
determining the power distribution in the nuclear reactor core. The calibration
by electric resistance heating of the gamma thermometer consists of applying an
electric current along the controlled heat path of the gamma thermometer and
then measuring the temperature difference along this controlled heat path as a
function of the amount of power generated by the electric resistance heating.
Then, after the gamma thermometer is installed into the nuclear reactor core and
the reactor core is operating at power producing conditions, the gamma ray
heating of the detector produces a temperature difference along the controlled
heat path. With the knowledge of this temperature difference, the calibration
characteristic determined by the prior electric resistance heating is employed
to accurately determine the local rate of gamma ray heating. The accurate
measurement of the gamma heating rate at each location of a set of locations
throughout the nuclear reactor core is the basis for accurately determining the
power distribution within the nuclear reactor core.
| United States Patent | 4,393,025 |
| Leyse | July 12, 1983 |
Method of and apparatus for measuring the power distribution in nuclear reactor cores
| Inventors: | Leyse; Robert H. (Rockville, MD) |
|---|---|
| Family ID: | 26901622 |
| Appl. No.: | 06/206,741 |
| Filed: | November 14, 1980 Here is some text: The method of calibration which has been described may be performed after the gamma thermometer assembly has been fabricated, but prior to installation into the nuclear reactor core. The calibration may also be determined after the apparatus is installed into the nuclear reactor core, for example, prior to first power operation of the nuclear reactor core or during shutdown of the nuclear reactor core after a period of extended operation. In addition, the calibration may be checked while the nuclear core is at power operation. In this latter case, one procedure would be the following: a. With no electrical power input, measure the temperature difference that results from gamma heating with the core at power and then utilizing the calibration curve of FIG. 4, determine the corresponding value of the power per unit length of thermocouple tube. b. Next, apply an increment of electric power to the thermocouple tube. Add this value of electric power to the gamma heating power determined in step a. Measure the temperature difference of the gamma thermometer detector. This temperature difference and the total of the gamma heating power and the electrical heating power may then be plotted on the original calibration curve as a check on the retention of the original calibration. c. Step b may be performed for several increments of electric power heating. Here are some CLAIMS: 17. The method of monitoring elongated fuel elements, which emit gamma rays, of a nuclear reactor core, comprising: (a) providing a flow path for the flow of a cooling fluid to be used for calibration purposes, and passing said cooling fluid along said flow path for calibration purposes, (b) providing an elongated instrument element including electrical conducting material having first and second zones, (c) locating said instrument in said flow path and exposing it to said fluid so that the temperature of the second zone depends on said temperature and rate of flow of said cooling fluid more than the temperature of the first zone depends on the temperature and rate of flow of said cooling fluid, (d) passing an electrical current, for calibration purposes, through said electrical conducting material to supply heat to both of said zones with the first zone rising in temperature more than the second zone due to cooling effect of said cooling fluid on said second zone, (e) measuring the temperature difference between said first and second zones to calibrate the instrument, (f) placing the instrument parallel to and adjacent said elongated fuel elements, (g) passing a cooling fluid past the instrument while it is adjacent said elongated fuel elements, (h) the step of passing a cooling fluid past the instrument for calibration purposes as aforesaid involving fluid cooling conditions substantially identical to those characterizing the cooling fluid that is passed by the instrument while it is adjacent to the elongated fuel elements, and (i) measuring the temperature difference between said two zones while the instrument is adjacent the elongated fuel elements with cooling fluid flowing past the same and without said electrical current flowing, whereby in view of the previous calibration of the instrument with said flow of current the output of the elongated fuel elements may be determined. 18. The method of claim 17 in which during step (i), the first zone rises in temperature above the second zone by an amount related to the output of the elongated fuel elements, and in which water is selected as the cooling fluid. 19. The method of claim 18 in which the cooling fluid is in such good thermal contact with the second zone that the second zone remains at a temperature substantially the same as that of the cooling fluid with the first zone rising to a higher temperature both during calibration as well as during operation adjacent the elongated fuel elements. 20. The method of monitoring elongated fuel elements as defined in claim 17 in which steps (a) to (e) inclusive are performed with said instrument positioned in a remote location with reference to said elongated fuel elements so that those elements do not supply substantial gamma rays to the instrument and so that the instrument is calibrated while the only heat supplied to the instrument during calibration results from said electrical current, and performing steps (f), (g) and (i) after the instrument has been calibrated in said remote location. 21. The method of monitoring elongated fuel elements as defined in claim 20 in which the instrument is calibrated as set forth in said steps (a) to (e) using a first flow path for the cooling fluid, and the elongated fuel elements are monitored as set forth in steps (f), (g) and (i) using a second flow path for the cooling fluid which second path is adjacent said elongated fuel elements and is remote from the first flow path. 22. The method of monitoring elongated fuel elements as defined in claim 17 in which step (f) is performed before the instrument is calibrated, and in which: the nuclear reactor core is shut down before the instrument is calibrated and in which the instrument is calibrated as called for by said steps (a) to (e) while the instrument is adjacent the elongated fuel elements and the nuclear reactor core is shut down. 23. The method of monitoring elongated fuel elements as recited in claim 22 in which the same flow path for the flow of the cooling fluid is used during said calibration steps (a) to (e) inclusive as is used for the monitoring steps (g) and (i). 24. The method of monitoring elongated fuel elements as recited in claim 17 in which the calibration steps (a) to (e) inclusive are performed while said instrument is adjacent said elongated fuel elements and while the nuclear reactor core is in operation, said calibration and monitoring steps comprising comparing the temperature differences between said zones under two conditions one of which conditions occurs while said electrical current is off and the other of which conditions occurs while said electrical current is on. 25. The method of monitoring elongated fuel elements as recited in claim 24 in which the calibration steps (a) to (e) inclusive are performed using several increments of electric power heating. 26. The method of monitoring elongated fuel elements as defined in claim 17 in which said measuring step (e) includes measuring the temperature difference between the "hot" and "cold" junction of a thermocouple, comprising: spacing said "hot" junction from all nearby liquid and solid matter while exposing said "hot" junction to said gamma rays. 27. The method of monitoring elongated fuel elements as defined in claim 26, comprising: positioning said "cold" junction in a bed of solid material and exposing said solid material to said cooling fluid, whereby said "hot" junction is heated to a temperature above said cold junction by reason of the direct impingement of said gamma rays on said "hot" junction with said cooling fluid having only a secondary effect on the temperature of said "hot" junction. 28. In apparatus for monitoring fuel elements, a nuclear reactor core: a measuring instrument comprising a thermocouple having a "hot" junction and a "cold" junction, said measuring instrument having a body, said body having an outer wall, said measuring instrument including means for mounting said "hot" junction inside said body and spaced from any and all liquid and solid material, said measuring instrument including solid material surrounding said "cold" junction and providing a heat conduction path from said cold junction to said outer wall, means for passing a cooling fluid along the outer wall of said body, and means for positioning said body in the path of said gamma rays to thus directly heat said hot junction, whereby the heat from said gamma rays elevates the temperature of the "hot" junction above that of the "cold" junction due to the better thermal contact between the "cold" junction and the cooling fluid than between the "hot" junction and the cooling fluid. Here is another link to ESBWR Design Summary: http://pbadupws.nrc.gov/docs/ML0217/ML021770054.pdf See page 56 for a Cross Section of Gamma Thermometer |
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