(Clicking on the above link will not bring up the patent. However, if you copy it to an email, the patent will appear when clicked on.)
| United States Patent | 5,621,161 | ||||||||
Leyse
|
April 15, 1997 |
Method for monitoring for the presence of dissolved gas in a fluid under pressure
The present invention relates to dissolved gases in fluids under pressure and, more particularly, to relating the electrical resistance of a sensor element to the presence of the dissolved gas.
BACKGROUND OF THE INVENTION
The presence of dissolved gas in fluid, such as water, under pressure can lead to unacceptable performance of certain support and monitoring equipment in industry. These factors are extremely important in nuclear power plants. In both pressurized water reactors and boiling water reactors, the presence of dissolved gas in reference level pipes for water level detectors leads to outgassing and degradation of calibration. In the case of the water-filled accumulators for an emergency core cooling system, called upper head injection, the presence of substantial amounts of dissolved gas (such as hydrogen and nitrogen) degrades the ability of the system to function and provide emergency core cooling. Dissolved gas is released during rapid pressure reductions which results in expulsion of fluid from reference pipes. This leads to erroneous vessel level readings at a time when there is a critical need for accurate level measurement.
I first wrote the patent application while I was at the Electric Power Research Institute (EPRI). It is part of an involved situation, but below is the reaction of the nuclear power gang at EPRI. It is misleading.
The need for the invention, the determination that dissolved gas is present in systems such as upper head injection, was well known to Rossin who wrote the above. Below is a two page memorandum that Rossin received during October, 1984. The second sentence of the opening paragraph is, "For example, AEOD does not recognize that plant operation with the UHI accumulator water saturated with dissolved nitrogen increases the chance of sustained core uncovery during some accidents."
At
the Staff‘s request, the BWROG submitted a report on May 20, 1993, discussing
the impact of level 84 'P errors on automatic safety system
response and operator actions during transients and accidents initiated from
reduced-pressure conditions during plant cooldown (shutdown mode). Based on
this information, in addition to the January 21, 1993 WNP-2 event, and data
from the reference-leg de-gas testing that was conducted by the BWROG, the
staff concluded that additional short-term actions needed to be taken for
protection against potential events occurring during normal cooldown. On May
28, 1993, NRC Bulletin (NRCB) 93-03, "Reso- lution of Issues Related to
Reactor Vessel Water Level Instrumentation," was issued, in which the
Staff requested each BWR licensee to implement additional short-term compensatory
actions, and to implement a hardware modification to
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