DE102017222344A1 - Apparatus and method for determining the boron content in a medium - Google Patents

Abstract

A measuring arrangement (2) for determining the boron content in a medium which flows through a pipeline (1) should also operate reliably without active cooling at high medium temperatures in the pipeline (1) and / or at high ambient temperatures, and should be as precise as possible of the boron content. This is achieved according to the invention by a measuring arrangement (2) having • a neutron source (16) which is arranged next to the pipeline (1), • a neutron detector (18) which is arranged next to the pipeline (1), and • an evaluation device ( 80), which determines the boron content in the medium by means of a counting rate (N) measured by the neutron detector (18), the neutron source (16) and / or the neutron detector (18) being surrounded by a neutron moderator consisting of a material from the group comprising graphite and polyetheretherketone and polyimide.

Description

The invention relates to an apparatus and a method for determining the boron content in a medium.

The measuring arrangement according to the present invention is a further development of the European patent specification EP 0 932 905 B1 known measuring arrangement. That is, the basic structure with respect to a neutron source and at least one neutron detector, which are preferably secured substantially opposite one another around a pipe, is maintained.

The measuring principle can be described as follows: Through the tube flows a medium, namely water with boric acid, whose boron content (isotope B-10) can be determined by the neutron detectors due to the absorption in the medium of the neutrons emitted by the neutron source.

• • Moderation der von der Quelle ausgesendeten Neutronen, um damit eine stärkere Absorption im Medium und ein höheres Signal bei den Detektoren (sprich eine Verbesserung des Signal- zu Rausch-Verhältnisses bei der Bormessung) erreichen zu können.
• • Der Moderator ist auch aus strahlenschutztechnischer Sicht bedeutend, da die moderierten Neutronen besser abgeschirmt werden können.

The neutron source, short source, and the neutron detectors, short detectors, are embedded in a moderator. According to the prior art, these are polyethylene (PE). The moderator fulfills two essential functions:

• • Moderation of the neutrons emitted by the source in order to be able to achieve greater absorption in the medium and a higher signal at the detectors (ie an improvement in the signal-to-noise ratio during the boron measurement).
• • The moderator is also important from a radiation protection point of view, since the moderated neutrons can be better shielded.

However, the previous design is only suitable for medium temperatures up to 100 ° C and ambient temperatures up to about 70 ° C, since the used moderator PE has a melting temperature of about 130 ° C and already softens at about 80 ° C. In addition, you can not rule out annoying aging effects in plastics such as PE.

The object of the invention is to further develop the known from the prior art measuring arrangement such that it works reliably without active cooling at high medium temperatures in the pipeline, for example, above 100 ° C and / or at high ambient temperatures and as precise as possible Determination of the boron content possible. Furthermore, a corresponding method should be specified.

With respect to the device, said object is achieved according to the invention by a measuring arrangement having the features of claim 1. A further independent solution which, together with the solution according to claim 1, realizes a general inventive concept, is specified in claim 2. Moreover, claim 10 contains a further independent solution that can be combined with the other two solutions mentioned. The corresponding method is defined in claim 14.

The measuring arrangement according to the present invention uses a temperature-resistant moderator or, depending on the field of application, a combination of several moderators. It is also the total abandonment of a moderator possible.

Suitable moderators are all temperature-resistant materials, which have certain moderation properties for neutrons, and a low neutron absorption, which decreases even further with increasing temperature and thus compensates for other temperature-dependent effects.

One possible suitable moderator is graphite. A graphite-moderated measuring arrangement also works at significantly higher medium temperatures and / or ambient temperatures. Since graphite is temperature resistant, it is generally possible to use it up to 300 ° C (medium temperature and also ambient temperature) and beyond. Thus, the measuring arrangement can be mounted in a nuclear power plant directly to the lines from the primary circuit and remains even during and after a fault with higher temperature still ready for use.

A combination of different moderators is always useful if the characteristics of two different moderators can be combined in an advantageous manner. For example, at a hot medium but moderate outdoor temperature location in an inner layer or shell, a temperature resistant moderator (eg graphite) may be applied and in a outer layer or shell a less temperature resistant moderator (eg PE). This has the advantage of a weight reduction (because the density of graphite is about twice as large as that of PE) with unchanged moderation effect and shielding the neutrons to the outside (radiation protection aspect).

The outer material may also be chosen to have neutron reflective properties to maximize the measurement signal as much as possible.

For example, you can fill the half-shell in which the source sits with another moderator, as the half-shell in which the detectors sit. Here you can select the best moderator to analyze the signal-to-noise ratio. Ratio of the measurement signal to optimize. Because the main purpose of the source is to slow down the fast neutrons emitted by the source so that they are absorbed by the boron in the medium as efficiently as possible, while at the detector site it is much more important to completely close the neutrons that have passed through the medium detect and lose none. Therefore, the reflection or backscattering of the neutrons towards the detector is more decisive than moderation. Based on these considerations, it is then possible to independently select suitable moderators for the side of the neutron source and the side of the detectors.

Other combinations of moderators are also possible, such as the combination of three or more moderators (eg, a neutron reflector as an additional outer layer). In each case the specific application or the given restrictions (weight, radiation protection, medium temperature, outside temperature) have to be considered.

A complete renouncement of a moderator has the advantage of a very robust construction. In addition, you have a significant cost reduction and weight savings. Thus, a design without a moderator can be used anywhere where certain lines only a limited weight can withstand, or where the seismic requirements are particularly large. In addition, use under higher temperatures (medium temperature and outside temperature) is possible.

However, one has a higher radiation exposure at the site of a measuring arrangement without a moderator, because the shielding effect of the moderator is eliminated. In addition, the requirements for the accuracy and response time should not be too high, because you have to accept a longer measurement time (and / or a reduced accuracy) due to the lower absolute measurement signal.

An increase in temperature in the medium causes the water in the medium to expand, which dilutes the boron. For the measuring arrangement, this means an increase in the measured counting rate, because fewer neutrons are absorbed by the temperature-induced dilution. These temperature-dependent effects on the count rate are compensated according to the invention with a temperature correction.

In addition, there are thermal effects in the moderator material and also in the detector, which has an influence on the measurement especially with changing ambient temperatures. Also in this regard, a correction is advantageously provided.

A particularly simple temperature correction algorithm corrects thermal effects with a single factor. This assumes that the temperature effects are independent of the boron concentration. This is only approximately the case. Therefore, such a correction is no longer adequate for use over a wide temperature range (eg 0 ° C to 300 ° C). In addition, it is necessary to consider and correct more thermal effects in the moderator material at changing ambient temperatures in order to arrive at an accurate measurement result. This is also not taken into account in the said simple temperature correction.

Recent information shows that just the ambient temperature has so far been taken into account too little, which leads to inaccurate results in the Borbestimmung.

Instead, a temperature correction is proposed according to the invention, which takes into account several influencing parameters on the count rate N, such. B. the respective Borkonzentration c, the medium temperature T _I and the ambient temperature T _A , The evaluation method thus operates preferably with a count rate N (c . T _I . T _A ), which functionally depends on the mentioned influencing parameters.

If necessary, a temperature gradient within the moderator should also be corrected. This can be solved either by the implementation of a suitable multi-dimensional function in the evaluation software, or by the characteristic curve N (c) for different temperatures (medium temperature T _I and outside temperatures T _A ) measures and interpolates in between. For this purpose, preferably the measurement data of at least two temperature sensors, namely on the one hand in the medium and on the other in or outside the moderator used.

In the case of rapid temperature changes, the temperature sensors react faster than the moderator temperature, so that the correction can already be deduced therefrom before a corresponding gradient occurs in the moderator. With such a method, one can permanently and predictively determine the required temperature correction and correct the measured value accordingly. That is, the required temperature correction for the temperature at the location of the detector, which may be significant in particular for measurements in a wide temperature range, is constantly recalculated on the basis of the input signals of the temperature sensors. It provides predictions for the correction needed after a certain amount of time (in which a particular gradient has set in the moderator). This method is also applicable when using different moderator layers.

• 1 zeigt einen Längsschnitt durch eine Messanordnung aus dem Stand der Technik (SdT) zur Bestimmung des Borgehalts in einem Medium.
• 2 zeigt einen zu 1 gehörigen Querschnitt.
• 3 zeigt einen Querschnitt durch eine Messanordnung gemäß einer Variante der Erfindung zur Bestimmung des Borgehalts in einem Medium.
• 4 zeigt einen Längsschnitt durch eine Messanordnung gemäß einer weiteren Variante der Erfindung zur Bestimmung des Borgehalts in einem Medium.
• 5 zeigt einen zu 4 gehörigen Querschnitt.
• 6 zeigt einen Querschnitt durch eine Messanordnung gemäß einer weiteren Variante der Erfindung zur Bestimmung des Borgehalts in einem Medium.
• 7 zeigt eine vereinfachte Ansicht einer Messanordnung gemäß einer der vorherigen Figuren, wobei zusätzliche Temperatursensoren schematisch angedeutet sind.
• 8 zeigt für eine Messanordnung gemäß einer der vorherigen Figuren den Verlauf der Temperatur am Ort des Detektors als Funktion der Zeit, wenn sich der den Detektor umgebende Moderator aufheizt (d. h. die Temperatur im Medium steigt).
• 9 zeigt den Verlauf Temperatur am Ort des Detektors als Funktion der Zeit, wenn sich der Moderator abkühlt (d. h. die Temperatur im Medium sinkt auf die Außentemperatur).
• 10 zeigt ein Beispiel einer Kennlinie für einen Detektor in einer der hier beschriebenen Messanordnungen. Die relativen Zählraten sind normiert auf die Zählrate von deionisiertem Wasser (0 ppm Bor). Eine Änderung der Zählrate überträgt sich auf eine Änderung in der Borkonzentration. Die Konzentrationsangaben sind hier für natürliches Bor gegeben.

Various exemplary embodiments of the invention will be explained in more detail below with reference to the schematic and partially greatly simplified drawings:

• 1 shows a longitudinal section through a measuring arrangement of the prior art (SdT) for determining the boron content in a medium.
• 2 shows you one 1 proper cross section.
• 3 shows a cross section through a measuring arrangement according to a variant of the invention for determining the boron content in a medium.
• 4 shows a longitudinal section through a measuring arrangement according to a further variant of the invention for determining the boron content in a medium.
• 5 shows you one 4 proper cross section.
• 6 shows a cross section through a measuring arrangement according to another variant of the invention for determining the boron content in a medium.
• 7 shows a simplified view of a measuring arrangement according to one of the preceding figures, wherein additional temperature sensors are indicated schematically.
• 8th shows for a measuring arrangement according to one of the preceding figures, the course of the temperature at the location of the detector as a function of time when the moderator surrounding the moderator heats up (ie the temperature in the medium rises).
• 9 shows the temperature at the location of the detector as a function of time when the moderator is cooling down (ie the temperature in the medium drops to the outside temperature).
• 10 shows an example of a characteristic curve for a detector in one of the measuring arrangements described here. The relative count rates are normalized to the count rate of deionized water (0 ppm boron). A change in count rate translates to a change in boron concentration. The concentration data are given here for natural boron.

The same or equivalent technical elements are provided in all figures with the same reference numerals.

1 and 2 are from the European patent specification EP 0 932 905 B1 taken and show a longitudinal section and a cross section through a measuring arrangement according to the prior art for determining the boron content in a liquid. For details, reference is made to said patent, the disclosure of which is incorporated herein by reference (incorporated by reference).

In summary, the patent describes EP 0 932 905 B1 a measuring arrangement 2 for determining the boron content in a medium, here a reactor coolant, which circulates in the cooling circuit of a nuclear reactor in a nuclear power plant. The refrigeration cycle comprises a section in which the reactor coolant during operation of the nuclear reactor in liquid form through a pipeline 1 flows. The pipeline, also referred to as the measuring line 1 is here in the example aligned vertically. The measuring arrangement 2 includes a neutron source 16 standing on one side of the pipeline 1 is arranged at a certain distance to her, as well as a neutron detector 18 in the form of at least one counter tube, essentially the neutron source 16 opposite on the other side of the pipeline 1 at a certain distance from it at about the same height as the neutron source 16 is arranged.

The of the neutron source 16 emitted neutrons occur (at least in large part) through the pipeline 1 and through the reactor coolant flowing therethrough and, unless they are absorbed on their way or scattered outward, on the opposite side by the neutron detector 18 detected. The at the neutron detector 18 The measured count rate correlates with the degree of neutron absorption in the reactor coolant, which in turn depends on the boron content or boric acid content in the reactor coolant. In this way, in an associated evaluation unit with a known intensity of the neutron source 16 From the measured count rate, the boron content or the boron concentration in the reactor coolant can be determined.

The neutron source 16 is from a half-shell 4 enclosed, which consists of a neutron moderator or short moderator. For holding the pipeline 1 in the center and the neutron source 16 a little further out is the half shell 4 provided with a corresponding cutout. The neutron detector 18 is in a similar way by a half-shell 6 enclosed, which also consists of a neutron moderator or short moderator. Both half shells 4 . 6 together form a complete shell in the installed position, here in the example with an octagonal outer contour in cross section, which in general can of course also be shaped differently. According to EP 0 932 905 B1 the neutron moderator of both shells exists Polyethylene (PE). The purpose of the neutron moderator is primarily in the thermalization of the neutron source 16 emitted neutrons to improve the signal-to-noise ratio at the neutron detector 18 , In addition, it causes a radiation protection shielding of the measuring device 2 to the outside environment. To improve the shield is optionally an additional enclosure 12 the two half-shells 4 . 6 of neutron absorbing material, here cadmium.

Furthermore, in a preferred variant, a cross-sectionally annular cooling passage through which a coolant flows during operation 20 between the pipeline 1 and the two half-shells 4 . 6 available. Preferably used as a coolant cooling air is used, with the help of a blower or fan 24 in the cooling channel 20 blown. Finally, advantageously located between the cooling channel 20 and the surrounding half-shells 4 . 6 a ring-shaped in cross-section thermal insulation layer 28 , preferably from an enclosed static air cushion.

The according to EP 0 932 905 B1 Material used as moderator Polyethylene is only suitable for ambient temperatures up to approx. 70 ° C because it softens at approx. 80 ° C. This corresponds to a medium temperature in the pipeline 1 of around 100 ° C. Although the measures described above for cooling the heat load caused by the medium on the two half-shells 4 . 6 but is still considerable at higher media temperatures. In addition, there is a risk that the active cooling by means of blower fails. In addition, in a scenario with high ambient temperatures (outside temperatures) also an inadmissibly high heating from the outside can take place. In the context of the present invention, therefore, various modifications of the known measuring arrangement 2 also proposed without active cooling at medium temperatures in the pipeline 1 over 100 ° C and / or at high ambient temperatures to function reliably in the long term.

In a first main variant of the measuring device or measuring arrangement according to the invention 2 is according to 3 completely dispensed with the moderator. That is, similar to the prior art is on the one hand, the pipeline leading to the medium to be examined 1 a neutron source 16 and, substantially diametrically opposite, on the other side, a neutron detector 18 comprising one or more counter tubes arranged. From 1 and 2 known half shells 4 . 6 but are not available. There is only air between these components. This achieves a significant cost reduction and weight saving with high temperature resistance, but must accept a higher radiation exposure in the environment, since the shielding effect of the moderator is eliminated. In addition, the moderator's positive influence on the signal-to-noise ratio at the neutron detector is eliminated 18 ,

In a second main variant according to 4 and 5 is the basic structure of the measuring arrangement 2 similar to the prior art according to 1 and 2 , On one side of the medium-carrying pipeline 1 is a neutron source 16 arranged, and substantially diametrically opposite on the other side is a neutron detector 18 comprising one or more counter tubes arranged. The neutron source 16 is from a half-shell 4 enclosed, which consists of a neutron moderator or short moderator. For holding the pipeline 1 in the center and the neutron source 16 a little further out is the half shell 4 provided with a corresponding cutout. The neutron detector 18 is in a similar way by a half-shell 6 enclosed, which also consists of a neutron moderator. Both half shells 4 . 6 together form a complete shell in the installation position 30 Here, in the example with a circular cross-sectional outer contour, which in general can of course also be shaped differently.

In contrast to the prior art, in which for both half-shells 4 . 6 Polyethylene (PE) is used as a moderator here is at least for one of the two half-shells 4 . 6 , preferably for both half-shells 4 . 6 a particularly temperature-resistant moderator from the group of materials comprising graphite and polyetheretherketone (abbreviated PEEK) and polyimide (PI) used. It can also be a mixture of these materials. These materials are suitable for use at temperatures up to 300 ° C or more. Active cooling by means of injected cooling air or the like can be dispensed with in this case. The out EP 0 932 905 B1 known cooling channel 20 between the pipeline 1 and the surrounding half-shells 4 . 6 can therefore be omitted. There are no moving parts needed.

In a possible embodiment is for both half shells 4 . 6 the same temperature-resistant moderator, so for example either graphite or PEEK or PI used. In an alternative embodiment, the two half shells 4 . 6 consist of different temperature-resistant materials, resulting in a targeted adaptation to different physical requirements on the side of the neutron source 16 on the one hand and on the side of the neutron detector 18 on the other hand allows.

The third main variant according to 6 builds on the second main variant according to 4 and 5 on. In addition to the two half-shells 4 . 6 formed inner shell 30 to which the above description applies, here is one of two half-shells 34 . 36 formed outer shell 40 present, preferably on the inner shell 30 is present and encloses this. Seen in section form the inner shell 30 and the outer shell 40 preferably a system of two concentric rings. If there are no particularly high outside temperatures, the outer shell can 40 consist of a less heat-resistant moderator than the inner shell 30 , If the outside temperatures are higher than the medium temperatures in the pipeline 1 but it can also be the other way around. In addition, the moderator of the outer shell 40 be optimized for a reflection of neutrons, so be effective as a neutron reflector. It is also possible here again - as with the inner shell 30 - the use of different materials for the two outer shells 34 . 36 , In this case, the abutment surfaces lie 44 between the two outer half shells 34 . 36 preferably in a plane with the abutment surfaces 42 between the inner half shells 4 . 6 , If the two outer half shells 34 . 36 However, consist of the same material, the outer shell is therefore formed uniformly from the material, then the abutting surfaces 42 . 44 in principle, are arbitrary to one another.

For example, from the two half shells 4 . 6 formed inner shell 30 completely made of graphite or PEEK or PI. As already mentioned above, alternatively, the two inner half shells 4 . 6 made of different materials, such as one of graphite and the other of PEEK. The from the two half shells 34 . 36 formed outer shell 40 however, for example, can be made entirely of PE, with the advantage of a weight reduction of the overall arrangement.

While it is generally advantageous, the neutron source must be 16 not necessarily opposite the neutron detector 18 be arranged. Both can also be more or less side by side, almost on one side with respect to the pipeline 1 be arranged. This applies to all variants of the invention described here. Optionally present moderators then form corresponding shell segments. To simplify the description, the term "half-shell" as used herein also covers such configurations.

At comparatively high medium temperatures in the pipeline 1 above 100 ° C, but also at high ambient temperatures, the temperature corrections described below are particularly advantageous for obtaining reliable measured values in all the variants described due to thermal moderator effects and detector effects and due to thermally induced density changes in the medium.

7 illustrates the input variables expediently used in this context, namely on the one hand the (intrinsic) temperature T _I in the area of the measuring arrangement 2 through the pipeline 1 flowing medium, which in the case of a good heat conducting pipe wall material approximately with the temperature on the outside of the pipe wall or on the inside of the pipeline 1 surrounding shell 30 equate to. The for measuring the temperature T _I required temperature sensor 50 may differ from the illustration in 7 at some distance from the measuring arrangement 2 be located downstream or upstream, provided that the temperature T _I does not change significantly over the corresponding route. On the other hand, on the outside of the shell 30 (or the outer shell 40 in the case of a two-shell construction), the surrounding ambient or outside temperature T _A through another temperature sensor 60 measured, which deviates from the illustration in 7 also farther away from the measuring arrangement 2 be arranged, provided the temperature T _A does not change significantly over the corresponding route. As will be described below, this can be done with a few expedient, simplifying assumptions of temperature T _D at the location of the neutron detector 18 or shortly detector inside the shell 30 as well as at any other point within the moderator.

You can also change the temperature directly T _D at the detector. However, a detector mounted on the outside of the moderator is easier to assemble and retrofit. In addition, it depends on the temperature distribution throughout the moderator (also in the outer layers) in order to correct thermal effects in the moderator material accordingly. Advantageously, therefore, at least two temperature sensors are used, one of them as possible inside and the other as far as possible outside.

The evaluations described below are preferably carried out in an electronic evaluation unit 80 , in which the evaluation and correction algorithms are implemented in hardware and / or software. In particular, the characteristics required for the evaluation and correction are also stored there in digital form, which were previously determined as part of calibration or standardization measurements. On the input side are the evaluation unit 80 the required measured values, in particular the measured count rate N and the temperatures T _I and T _A supplied, and then outputs the current Borkonzentration c.

Temperature correction due to thermal moderator and detector effects:

The temperature T _D at the location of the detector depends on the measured temperatures of at least two temperature sensors - here for simplicity on the one hand T _I : Temperature in the medium measured by intrinsic sensor, and on the other T _A : Outside temperature measured on the outer surface of the moderator. In addition, the time history must be calculated to make predictions for a correction: $$T_D\left(t\right)=f\left(T_I-T_A.t\right)$$

If the medium in the tube heats up, ie T _I (t)> T _I (t ₀ ) with t> t ₀ (t ₀ : start time, t: current time, t ₁ : time constant for normalization) and T _D (t ₀ ) = T _A ), the following applies: $$T_D\left(t\right)=T_A+\alpha \cdot \left(T_I-T_A\right)\cdot \left(1-\text{exp}(-\left(t-t_0\right)\text{/}{t}_1\right)$$

Here, α <1 denotes a material- and geometry-specific constant (with respect to the thermal conductivity of the material).

The corresponding course of the temperature T _D at the location of the detector as a function of time t during a heating process is exemplified in 8th shown.

If the medium in the tube cools down, ie T _I (t) <T _I (t ₀ ) with t> t ₀ (t ₀ : start time, t: current time, t ₁ : time constant for normalization) and T _D (t ₀ ) = T _A + α · (T _I -T _A ), applies accordingly: $$T_D\left(t\right)=T_A+\alpha \cdot \left(T_I-T_A\right)\cdot \text{exp}\left(-\left(t-t_0\right)\text{/}{t}_1\right)$$

The corresponding course of the temperature T _D at the location of the detector as a function of time t during a cooling process is exemplified in 9 shown.

The temperature of the detector T _D is chosen here by example. Similarly, one could determine the temperature at each point within the moderator as a function of time and make predictions about the correction needed.

Instead of an exponential function, the heating or cooling can also be described by a polynomial.

wobei die Zeitabhängigkeit in der Temperatur am Ort des Detektors steckt: $$T_D=T_D\left(t\right)$$

The count rate is then corrected according to the temperature effect (in the moderator material itself or in the detector): $$N_{kOrr}\left(t\right)=f\left(T_A-T_D\right).$$

where the time dependence is in the temperature at the location of the detector: $$T_D=T_D\left(t\right)$$

mit material- bzw. geometriespezifischen Konstanten β_i.In general, such a correction can be used as a polynomial: $$N_{kOrr}\left(t\right)=N_{mess}\cdot \left(1+{\displaystyle \underset{i}{\Sigma }{\beta }_i\cdot {\left(T_A-T_D\right)}^i}\right)$$

with material- or geometry-specific constants β _i .

As a first approximation, the correction can be applied linearly: $$N_{kOrr}\left(t\right)=N_{mess}\cdot \left(1+\beta \left(T_A-T_D\right)\right)$$

If you use the above formula for heating, you get: $$N_{kOrr}\left(t\right)=N_{mess}\cdot \left(1-\beta \cdot \alpha \cdot \left(T_I-T_A\right)\cdot (\text{1}\mathrm{-}\text{exp}\left(-\left(t-t_0\right)\text{/}{t}_1\right)\right)$$

And for cooling: $$N_{kOrr}\left(t\right)=N_{mess}\cdot \left(1-\beta \cdot \alpha \cdot \left(T_I-T_A\right)\cdot \text{exp}(-\left(t-t_0\right)\text{/}{t}_1\right)$$

The constants can be summarized, and then one has only a dependence of N _korr (t) = N _mess * f (T _I -T _A , t) for the temperature correction with respect to thermal moderator effects and detector effects.

Temperature correction due to thermally induced density changes in the medium:

Furthermore, an additional temperature correction is needed, which takes into account thermally induced density changes in the medium. For this purpose a correction function g ( T _I , c) a, which of the internal temperature (medium temperature) T _I and the concentration c depends. This means that you get the following correction: $$N_{kOrr}=N_{mess}\cdot f\left(T_I-T_A.t\right)\cdot G\left(T_I.c\right)$$

In general, the function g ( T _I , c) are also represented by a polynomial: $$G\left(T_I.c\right)={\displaystyle \underset{i}{\Sigma }{a}_i\left(c\right)\cdot T_I^i}$$

The factors a _i (c) are applied as a function of concentration. In a first approximation, the factors a _i (c) could be set linearly in the concentration: $$a_i\left(c\right)=a_{\mathrm{<figure-callout\; id="0"\; label="i"\; filenames="DE102017222344A1\_0018.png"\; state="\{\{state\}\}">i</figure-callout>}0}+a_{\mathrm{<figure-callout\; id="1"\; label="i"\; filenames="DE102017222344A1\_0014.png,DE102017222344A1\_0015.png"\; state="\{\{state\}\}">i</figure-callout>}1}\cdot c$$

The associated constants a _i0 and a _i1 would then have to be determined experimentally.

With the aid of the corrected counting rate N _korr, it is then possible to use the example in 10 shown characteristic Borkonzentration be determined. Thanks to the corrections described above, the determination of the boron concentration also works reasonably well at higher temperatures (in the medium and in the moderator).

In this example, the boron concentration always refers to the mass concentration (not the volume concentration).

LIST OF REFERENCE NUMBERS

1

pipeline

2

measuring arrangement

4

half shell

6

half shell

12

wrapping

16

neutron source

18

neutron detector

20

cooling channel

24

fan

28

insulation layer

30

Bowl

34

half shell

36

half shell

40

Bowl

42

abutting face

44

abutting face

50

temperature sensor

60

temperature sensor

80

evaluation device

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0932905 B1 [0002, 0026, 0027, 0029, 0031, 0034]

Claims (14)

Measuring arrangement (2) for determining the boron content in a medium which flows through a pipeline (1) with A neutron source (16), which is arranged next to the pipeline (1), • a neutron detector (18), which is arranged next to the pipeline (1), and An evaluation device (80) which determines the boron content in the medium from a count rate (N) measured by the neutron detector (18), the neutron source (16) and / or the neutron detector (18) being surrounded by a neutron moderator consisting of a neutron moderator Material from the group comprising graphite and polyetheretherketone and polyimide. Measuring arrangement (2) for determining the boron content in a medium which flows through a pipeline (1) with A neutron source (16), which is arranged next to the pipeline (1), • a neutron detector (18), which is arranged next to the pipeline (1), and An evaluation device (80) which determines the boron content in the medium from a count rate (N) measured by the neutron detector (18), wherein neither the neutron source (16) nor the neutron detector (18) is surrounded by a neutron moderator. Measuring arrangement (2) according to Claim 1 wherein the neutron source (16) and the neutron detector (18) are each surrounded by a half-shell (4, 6) of graphite or polyetheretherketone or polyimide. Measuring arrangement (2) according to Claim 3 , wherein the two half-shells (4, 6) consist of different materials. Measuring arrangement (2) according to Claim 3 or 4 , wherein the shell (30) formed by the two half-shells (4, 6) is surrounded by an outer shell (40) consisting of a neutron moderator. Measuring arrangement (2) according to Claim 5 wherein the outer shell (40) is made of polyethylene. Measuring arrangement (2) according to one of Claims 3 to 6 , as the outermost shell, a neutron reflector is present. Measuring arrangement (2) according to one of Claims 3 to 6 , where as the outermost shell a neutron absorber is present. Measuring arrangement (2) according to one of Claims 1 to 8th wherein the neutron source (16) and the neutron detector (18) are disposed substantially diametrically opposite each other with respect to the pipeline (1). Measuring arrangement (2) for determining the boron content in a medium which flows through a pipeline (1), having • a neutron source (16) which is arranged next to the pipeline (1), • a neutron detector (18) adjacent to the pipeline (1), and • an evaluation device (80) which determines the boron content in the medium based on a count rate (N) measured by the neutron detector (18), wherein the evaluation device (80) is configured to read based on the temperature a first temperature measuring point, in particular the temperature (T _D ) or the ambient temperature (T _A ) present at the neutron detector (18), and a temperature-dependent correction of the measured counting rate based on the temperature at a second temperature measuring point, in particular the temperature (T _I ) of the medium (N). Measuring arrangement (2) according to Claim 10 with a temperature sensor (50) which detects the current temperature (T _I ) of the medium, and with a temperature sensor (60) which detects the current ambient temperature (T _A ) or the temperature (T _D ) at the neutron detector (18), the evaluation device (80) determines the temperature at a location between the temperature measuring points, in particular the temperature (T _D ) at the neutron detector (18), from the at least two temperatures measured at different locations. Measuring arrangement after Claim 10 or 11 , wherein the evaluation device (80) takes into account the density of the medium which varies with the temperature (T _I ) of the medium in determining the boron concentration (c). Measuring arrangement according to one of Claims 10 to Claim 12 wherein the evaluation device (80) takes into account a plurality of coupled influencing factors, in particular thermal effects and boron concentration effects, by a multi-dimensional function mixed in temperature and concentration (N (c; T) ≠ f ₁ (c) .f ₂ (T)). Method for determining the boron content in a medium which flows through a pipeline (1) by means of a measuring arrangement (2) having • a neutron source (16) which is arranged next to the pipeline (1), • a neutron detector (18) is arranged next to the pipeline (1), and • an evaluation device (80) which determines the boron content in the medium from a count rate (N) measured with the neutron detector (18), wherein on the basis of the temperature at a first temperature measuring point, in particular at the neutron detector (18) present temperature (T _D ) or the ambient temperature (T _A ), and based on the temperature at a second temperature measuring point, in particular the temperature (T _I ) of the medium, a temperature-dependent correction of the measured count rate (N) is made.

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