Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Calorimeter
Reexamination Certificate
2001-01-11
2002-10-15
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Calorimeter
C436S143000, C436S144000, C422S090000, C422S083000
Reexamination Certificate
active
06464938
ABSTRACT:
The present invention relates to a device for measuring the concentration of hydrogen in a gaseous mixture and in particular in the air constituting, for example, the atmosphere inside closed premises.
The technical field of the invention can perhaps be described as that of measurement, that is to say the quantitative evaluation of the concentration or level of hydrogen H
2
in a gaseous mixture such as air and water vapour; this atmosphere can also be charged with aerosols and dust, following an accident.
The devices or apparatus making it possible to ensure a qualitative or quantitative measurement of the hydrogen in a gaseous mixture can in fact be classified, on the one hand among detectors which can possibly be calibrated as measuring instruments within a very limited range of values, and on the other hand among laboratory apparatuses which are very complex and which require diverse supplies of reference gas as well as specialised operators.
These also exist indicators which are not usable at present in an atmosphere after an accident and whose range of uncertainty is very wide.
The simplest indicators are catharometers whose principle is based on measuring the thermal conductivity of the gas contained in a chamber.
Apparatuses like this are generally only used in an atmosphere of a known type and they are therefore calibrated specially with this aim. They also require a complex installation with gas sampling, a condenser and filters.
Recently, that is to say over about five years, a big. demand has built up for measuring instruments able to be placed at precisely the point where the hydrogen level needs to be known, and capable of measuring hydrogen levels in a range from 0 to 30% of H
2
, that is to say much above the ignition, combustion and explosion thresholds for hydrogen.
These demands result principally from operators of nuclear power plants world-wide. One of the major risks in the event of an accident causing fusion of the core is in fact the risk of explosion due to hydrogen, which means that each reactor requires the operation of several dozens of instruments.
Several types of measuring instruments trying to respond to the demands described above have therefore been developed and marketed. These measuring instruments depend on either the electrochemical or the thermal properties of hydrogen.
All these instruments have the radical inconvenience of requiring a permanent and substantial electricity supply whereas, in the event of a serious accident, the first consequence of this is precisely the loss of all electricity supplies.
The present inventors have moreover demonstrated, during tests concerning all the measuring instruments currently available, that none of them is acceptable, one of the fundamental reasons being that the atmosphere in the dome of a nuclear power plant after an accident comprises a very high proportion of water vapour and very high radioactivity under the form, among others, of aerosols and dusts, which disturb measuring systems.
The apparatuses known in the present state of the art also suffer from their weight, their dimensions, and their high cost.
In conclusion, all these instruments, whatever their type, have the inconvenience of a very high cost, lack of adaptation to the expressed demand and are, in short, little or not at all operational.
Therefore a need exists for a device for measuring the concentration of hydrogen in a gaseous mixture which, among other requirements, is simple, not bulky, light in weight and also highly reliable.
There is still a need for a device which makes it possible to measure with precision the concentrations of hydrogen in all the possible ranges of concentration, in particular those above the ignition, combustion and explosion thresholds for hydrogen.
This device must, in addition, be able to be used without suffering any disturbance for measuring the concentration of hydrogen for any gaseous mixture, whatsoever its composition, the possible presence of aerosols and dust, and its radioactivity, which is the case for example in the atmosphere present in the dome of a nuclear power plant after an accident.
The aim of the present invention is to provide a device for measuring the concentration of hydrogen in a gaseous mixture that responds, among other things, to the essential part of the needs indicated above.
The aim of the present invention is also to provide a device which does not have the inconveniences, limitations, lacks and disadvantages of the devices of prior art and which solves the problems of prior art mentioned above.
This aim is attained, in conformity with the present invention, by a device for measuring the concentration of hydrogen in a gaseous mixture comprising a sensor in contact with said gaseous mixture, said sensor being linked to means for calculation and display, in which said sensor comprises a catalyst capable of initiating an exothermic reaction with the hydrogen contained in the gaseous mixture, conducting means fixed to said catalyst to transfer the thermal energy generated, essentially by conduction, from said catalyst to a cold point, means for measuring the temperature T
1
of said catalyst and the temperature T
2
of said cold point being linked to means for calculating the value of the molar concentration of hydrogen in a gaseous mixture from the temperature gradient measured T
1
-T
2
, said means of calculation communicating said value of hydrogen concentration to said display means.
The device according to the invention responds to all the requirements indicated above, and provides a solution to the problems of prior art.
Generally speaking, the device according to the invention has much smaller dimensions and much lower weight compared to known devices.
In addition, as an example, the “sensor” device according to the invention can have overall dimensions of 10 to 15 cm and a weight generally less than 1 kilogram.
The low weight and small dimensions of the device according to the invention make it possible in a particularly advantageous manner to position it in places with particularly difficult access, which is not the case for the devices proposed at present.
In the same way, the device according to the invention is very simple, and only comprises a limited number of elements, which reduces the cost, simplifies manufacture and maintenance, and contributes to its reliability.
The sensor of the device according to the invention does not need any electricity supply, contrary to prior art devices, which require a permanent and substantial electricity supply.
In fact, the sensor only comprises elements which themselves generate the energies and electrical voltages needed.
This sensor autonomy makes it particularly adapted to operating in the chambers of nuclear power plants after an accident, since it can remain operational even if the electricity supply systems of the power plant fail.
Only the means for calculation and display, which can be moved outside the dangerous zone, are supplied electrically; but their consumption remains very low and their supply can be independent from the general supply of the power plant.
Thus, the battery life of the device according to the invention can be 10 to 100 times greater than the autonomy of prior art devices.
Moreover, the need for supply and/or remote control of the pumps and solenoid valves of prior art devices greatly increases the probability of very quick failure of one of the elements in an accident sequence.
Besides this, according to the invention, these means of calculation and display of the concentration of H
2
can be set at any distance from the sensor, that is to say that they can, for example, be placed outside the atmosphere of the power plant and not be submitted to the drawbacks of an accident situation.
The sensor and the means of calculation and display are linked by any known means such as a single cable whose dimensions are small and whose protection against aggression is greatly simplified.
In particular, the invention relies on the surprising and unexpected use of a catalytic exothermic reaction of hydro
Bonhomme Thierry
Perez Christian
Rongier Pierre
Commissariat a l'Energie Atomique
Harness & Dickey & Pierce P.L.C.
Siefke Sam
Warden Jill
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