Method for location of shocks with a structure-borne sound monitoring system, in particular in pressurized enclosures in power plants

A method for the location of shocks with a structure-borne sound monitoring system is used especially for pressurized enclosures in power plants, particularly nuclear power plants. Structure-borne sound monitoring systems were heretofore dependent upon assumptions regarding the propagation velocities of the structure-borne sound sensors. According to the invention an exact method of ascertaining the propagation velocities and the burst location is given. The invention begins with the realization that the frequency spectrum of the respective bursts of information for clarification of the dispersion behavior, for identifying the sound wave modes and for deriving the group velocity of these modes is self-evident. Burst signal-rise time differences, wave modes, especially s.sub.0 and a.sub.0 mode, as well as the pertaining group velocities are then ascertained. The sound travel distance from the burst location to the sturcture-borne sound-sensors are determined on the basis of fact with at least double redundancy based on the general relationship EQU L.sub.S-E =t.sub.i,n .multidot.v.sub.i v.sub.n /(v.sub.i -v.sub.n) so that at least three burst signal components are separated through corresponding electronic signal filter systems.

The invention relates to a method for the location of shocks or "bursts" 
using a structure-borne sound monitoring system, especially in pressurized 
enclosures, such as structural components and pipelines in power plants, 
which includes: 
picking-up burst signals originating at a burst site with at least one 
structure-borne sound sensor mounted at different points on an enclosure 
to be monitored, and recording the burst signals with recording devices 
connected downstream of the at least one sensor; and 
filtering two burst signal components (BS.sub.1, BS.sub.2) out of the burst 
signal spectrum at frequencies (f.sub.1, f.sub.2) including frequency 
bandwidths (.DELTA.f.sub.1, .DELTA.f.sub.2), and referring the two burst 
signal components (BS.sub.1, BS.sub.2) to a rise time difference 
(.DELTA.t.sub.1,2) resulting from dissimilar arrival times (t.sub.1, 
t.sub.2) of the two burst signal components at a given one of the at least 
one structure-borne sound sensor, so that in accordance with a general 
formula: 
##EQU1## 
the sound travel distance (L.sub.S-E) from the at least one 
structure-borne sound sensor to the burst site can be determined, wherein 
(v.sub.1 v.sub.2) represent the suspected propagation velocities at a 
given frequency. 
The method has a particular significance for nuclear power plants, for 
example pressurized water reactors (PWR) and boiling water reactors (BWR). 
Assuring the integrity of the pressurized structural components and 
pipelines plays a particularly important role in this case. The structural 
components include not only the reactor pressure vessel but also the steam 
generator, primary coolant pumps, and pressure maintenance elements, to 
name only the most important. 
Thus if loose or wobbling parts cause abnormal signals (bursts) from 
structure-borne sound or sound transmitted through solids in power plants 
in general, or in nuclear power plants in particular, then locating the 
shocks is one of the most important aids in determining the cause thereof. 
A generic method is known, for instance, from the paper by B. J. Olma et al 
entitled "Schwingungs- und Korperschalluberwachung an 
Primarkreiskomponenten von Kernkraftwerken" [Monitoring Vibration and 
Structure-Borne Sound in Primary Loop Components of Nuclear Power Plants], 
in VDI Berichte [German Engineering Association Reports] 568 (1985), pages 
13-18. However, accurate location is not always reliably possible with 
this prior art method, for the following reasons: 
it is seldom clear whether the measured reference sound velocities are 
applicable to the signals presently occurring; 
often, only the site of the induction of the sound into the pressurized 
enclosure can be determined, but not the actual shock site; 
sometimes the number of signal pick-ups installed is not adequate to define 
the sound induction site more closely. 
In the prior art method, magnetic, adapted structure-borne sound pick-ups 
that have two resonant frequencies are used, such as a pick-up-specific 
frequency at approximately 20 to 30 kHz and a fastener-specific frequency 
in the range from 5 to 10 kHz, for the separation of two burst signal 
components, where associated propagation velocities are postulated or 
suspected. 
It is accordingly an object of the invention to provide a method for the 
location of shocks with a structure-borne sound monitoring system, in 
particular in pressurized enclosures in power plants, which overcomes the 
herein aforementioned disadvantages of the heretofore-known methods of 
this general type and in which: 
more-accurate location of the burst site by means of self-checking is 
permitted, or in other words, operation with redundancy; 
the number of structure-borne sound sensors or pick-ups required for a 
given measurement task can be reduced in general, without having to make 
sacrifices in reliability or replaceability of the results; and 
not only the sound induction sites but also shock or burst sites can be 
ascertained. 
With the foregoing and other objects in view there is provided, in 
accordance with the invention, in a method for location of shocks or 
bursts using a structure-borne sound monitoring system, which includes: 
picking-up burst signals originating at a burst site with at least one 
structure-borne sound sensor mounted at different points on an enclosure 
to be monitored, and recording the burst signals with recording devices 
connected downstream of the at least one sensor; and filtering two burst 
signal components (BS.sub.1, BS.sub.2) out of the burst signal spectrum at 
frequencies (f.sub.1, f.sub.2) including frequency bandwidths 
(.DELTA.f.sub.1, .DELTA.f.sub.2), and referring the two burst signal 
components (BS.sub.1, BS.sub.2) to a rise time difference 
(.DELTA.t.sub.1,2) resulting from dissimilar arrival times (t.sub.1, 
t.sub.2) of the two burst signal components at a given one of the at least 
one structure-borne sound sensor, so that in accordance with a general 
formula: 
##EQU2## 
the sound travel distance (L.sub.S-E) from the at least one 
structure-borne sound sensor to the burst site can be determined, wherein 
(v.sub.1 v.sub.2) represent the suspected propagation velocities at a 
given frequency: 
the improvement which comprises: 
separating at least three burst signal components (BS.sub.i . . . BS.sub.n) 
at frequencies (f.sub.1 . . . f.sub.n) with electronic signal filter 
systems; 
determining a group of signal onsets (t.sub.i . . . t.sub.n) of the burst 
signal components (BS.sub.l . . . BS.sub.n), where (i=1, 2, 3 . . . n); 
forming rise time differences (t.sub.l -t.sub.r) . . . (t.sub.n -t.sub.r) 
with respect to a reference time (t.sub.r) selected arbitrarily from the 
group of signal onsets (t.sub.i . . . t.sub.n); 
determining the dispersion behavior of the separated burst signal 
components (BS.sub.i . . . BS.sub.n) from the rise time differences, as a 
function of the frequencies (f.sub.i . . . f.sub.n) known from the 
filtering; 
ascertaining the type of sound propagation (s.sub.0 mode, a.sub.0 mode) of 
the individual burst signal components and the group velocities (v.sub.i . 
. . v.sub.n) belonging to the individual burst signal components (BS.sub.i 
. . . BS.sub.n) by taking into account the wall thickness of the enclosure 
carrying the signal and by comparative analysis with the theoretical 
dispersion behavior; and 
subsequently determining the sound travel distance (L.sub.S-E) with at 
least double redundancy based on the general formula, with at least two 
parameter sets to be inserted into the general formula. 
In accordance with another mode of the invention, there is provided a 
method which comprises determining the theoretical dispersion behavior 
with mode diagrams for various wave modes (s.sub.0, a.sub.0, a.sub.1 . . . 
) of plate waves in the form of propagation velocities plotted as a 
function of frequency or as a function of the product of plate thickness 
times frequency. 
In accordance with a concomitant mode of the invention, there is provided a 
method which comprises: 
(a) ascertaining a variable L.sub.S-E =D+L in at least two received burst 
signal components (BS.sub.1, BS.sub.2) having dissimilar frequencies 
(f.sub.1, f.sub.2) of a single wave mode (a.sub.0 or s.sub.0), from a rise 
time difference 
##EQU3## 
measured by the at least one structure-borne sound sensor, and from the 
velocities (v.sub.1 and v.sub.2), which are known and are dissimilar 
because of the dispersion, wherein D represents the sound travel distance 
in the structural component and L represents the sound travel distance in 
a sound conduction route joined at one side to the structural component; 
(b) deriving intervals (A) of the rise time differences of the curves or 
envelopes of the measured values from a rise time/frequency diagram with 
the at least one structure-borne sound sensor and with fixed frequencies 
(F) for two different wave modes (a.sub.0) and (s.sub.0) and 
correspondingly with dissimilar propagation velocities (v.sub.s not equal 
to v.sub.a), and subsequently ascertaining the three-dimensional distance 
L.sub.S-E =D+L in accordance with the relationship: 
##EQU4## 
and 
(c) ascertaining the site of the sound induction in accordance with the 
relationship: 
##EQU5## 
and with the aid of hyperbolic section position finding, at fixed 
frequencies (F) with at least three structure-borne sound sensors, each 
furnishing burst component time differences for the a.sub.0 and the 
s.sub.0 mode, wherein the interval (A.sub.p) between the a.sub.0 and the 
s.sub.0 curve in the diagram associated with one of the sensors is 
different from the interval (A.sub.q) between the a.sub.0 and the s.sub.0 
curve in the diagram associated with another of the sensors, and wherein 
the plate thickness or wall thickness is the same. 
The invention is based on the recognition that first, bursts in themselves 
carry the information as to the velocity with which the signal components 
have reached the pick-up, and that second, at least two separable burst 
signal components are present in the burst, having velocities of sound 
which are different from one another and which are even known because of 
the aforementioned first condition. A closer study of the theory of plate 
waves has shown that with structure-borne sound signals or so-called 
bursts, both of these conditions are fulfilled. In location methods of the 
prior art, the full informational content of the bursts was never 
exploited. 
The advantages of the invention are listed in further detail in the final 
section below entitled "4. Findings, Conclusions and Advantages". 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a 
method for the location of shocks with a structure-borne sound monitoring 
system, in particular in pressurized enclosures in power plants, it is 
nevertheless not intended to be limited to the details shown, since 
various modifications may be made therein without departing from the 
spirit of the invention and within the scope and range of equivalents of 
the claims.

Referring now to the figures of the drawings in detail, it is noted that 
due to the complexity of the method according to the invention, it will 
first be explained below in principle while referring to FIGS. 1-4, and 
then two embodiments will be explained in detail while referring to Figs. 
5A, 5B and 5C through 7. For the sake of better comprehension, the 
description is subdivided into sections 1-4 and corresponding subsections. 
The formulas given below are numbered serially, for the sake of easier 
reference. 
1. Discussion of location problems presented by rise time differences: 
Some major simplifications are made in the following discussion. Among them 
are that sound mode transformations, particularly at the transitions from 
pipelines to vessel walls, are ignored, and it is assumed that the 
information expressed by the plate waves is at least approximately valid 
for the pipelines as well. 
Although this could certainly lead to inaccuracies in the location of sound 
sources with small pipeline diameters and thus especially at low sound 
signal frequencies, the method outlined at this point does permit at least 
an approximate determination of the sound velocity from the signals 
themselves, and thus a substantial improvement of the situation as 
compared with that in which it was not even possible to differentiate 
between the velocities of approximately 5.2 kms.sup.-1 and 3.0 kms.sup.-1, 
which in fact differ by almost a factor of 2. With this restriction, the 
basic problems will now be explained, referring to the diagrammatic 
illustration of a pipeline and part of a vessel wall (such as a wall of a 
reactor pressure vessel or steam generator) provided in FIG. 1. In FIG. 1, 
L is the length of the pipeline segment from the shock site S to the 
vessel wall. D.sub.i (i=1, 2, 3) are the shortest travel lengths from the 
pipeline connector to three pick-ups, in the form of structure-borne sound 
sensors A1, A2, A3 for sensing sound transmitted through solids. t.sub.i 
(i=1, 2, 3) represents the instants at which bursts are recorded in 
pick-ups A.sub.i, and v.sub.i represent the structure-borne sound 
velocities along the way from the shock site to the pickups or sensors. 
Then, 
EQU t=t.sub.i -t.sub.j =D.sub.i /v.sub.i -D.sub.j /v.sub.j +L(1/v.sub.i 
-1/v.sub.j) (1) 
which is a general formula that can be derived inductively by the following 
process: 
If the rise time difference .DELTA.t.sub.2,1 =(t.sub.2 -t.sub.0)-(t.sub.1 
-t.sub.0) of two structure-borne sound signals is to be ascertained, one 
of which is recorded by the pick-up A2 at time t.sub.2 and the other by 
the pickup A1 at time t.sub.1, and both signals belong to one and the same 
burst at the site S, then the following applies: 
##EQU6## 
where t.sub.0 represents the reference instant, which is generally the 
instant of the shock of the loose part on the pressurized enclosure. Since 
the pick-ups or structure-borne sound sensors A1 and A2 were taken into 
consideration in this formula, corresponding subscripts "1" and "2" have 
also been used for the associated lengths, namely D.sub.1 and D.sub.2, and 
for the associated velocities, namely v.sub.1 and v.sub.2. In this 
concrete case, the decision has been made that D.sub.1 is not equal to 
D.sub.2. Each of these two subscripts "1" and "2" can belong to either of 
two index groups i or j, where i=1, 2, 3 and j=1, 2, 3. Thus the general 
case is expressed that D.sub.i and D.sub.j can differ from one another or 
can be equal to one another. The same applies to v.sub.i and v.sub.j, as 
well as to t.sub.i and t.sub.j. 
Based on the theory of sound propagation conditions in plates (e.g., pipe 
or vessel walls), (see, for example, B. J. Krautkramer and H. Krautkramer, 
Werkstoffprufung mit Ultraschall [Material Testing with Ultrasound], 
fourth edition, Springer Verlag, 1980), various kinds of sound propagation 
with various group velocities occur, which furthermore also exhibit the 
phenomenon of dispersion (see FIG. 2). Therefore in the location process 
(that is, in the evaluation of the above formula), it is not clear what 
values should be used for v.sub.i or v.sub.j in order to ascertain the 
sound travel distances D.sub.i and L from the measured rise time 
differences .DELTA.t, even if reference velocities are available from test 
shock data. 
There is also a case, which previously was often assumed in practice, that 
v.sub.i (i=1, 2, 3, . . . )=v=v.sub.j (j=1, 2, 3) are all of equal 
magnitude; 
EQU .DELTA.t=D.sub.i /v.sub.i -D.sub.j /v.sub.j =(D.sub.i -D.sub.j)/v (2) 
and in principle only the site of the sound induction (that is, the 
magnitude of D.sub.i) is determinable. 
If individual reactor components are only provided with a few pick-ups, or 
if only one of the pick-ups even receives a sufficiently large signal, 
then in the past, either any indication as to location was usually 
impossible, or additional pick-ups had to be reset during operation. 
As a limitation, it should be noted that a "loop method" is known (for 
example, see B. J. Olma, Progress in Nuclear Energy, 1985, Vol. 15, pages 
583-594), with which a kind of location is also possible with one or two 
pick-ups, if at least two components that have different velocities 
v.sub.1 and v.sub.2 can be separated within the burst. In that case, the 
following equation applies to the rise time differences of the first 
components: 
EQU .DELTA.t=(D+L) (v.sub.2 -v.sub.1)/v.sub.1 .multidot.v.sub.2 (3) 
and if v.sub.1 and v.sub.2 are known, then D+L can be ascertained. 
B. J. Olma et al have separated two sound mode components in one burst 
having different velocities, by using the pick-up resonance or magnet 
adaptation resonance, and are thus capable of performing a location. 
However, this method only partially solves the fundamental problems in 
location, because of the following factors: 
the dispersion is only incompletely taken into account; and 
the separation of the modes is highly incomplete: For instance, it is 
assumed without comment that in the frequency band of the magnet 
adaptation resonance (at approximately 5 to 10 kHz), only the a.sub.0 mode 
occurs. The fact that this is not always true will be documented below 
using test shock data. 
2. Exploitation of the Dispersion of Sound Modes for Determining the Actual 
Sound Velocities from the Burst Itself: 
2.1. Separation of the sound modes s.sub.0 and a.sub.0 based on the 
dispersion: 
According to FIG. 2, the relevant parameter range for d.multidot.f 
.ltoreq.2.5 mm MHz for nuclear power plant components, the s.sub.0 mode 
and the a.sub.0 mode exhibit entirely different dispersion. While the 
s.sub.0 mode velocity at a low d.multidot.f initially takes a nearly 
constant course and then only drops off steeply beyond 
d.multidot.f.apprxeq.1.5 mm MHz, the a.sub.0 mode velocity exhibits a 
great dispersion, especially at low values for d.multidot.f, and takes a 
virtually constant course from d.multidot.f.apprxeq.0.7 mm MHz on. The 
a.sub.1 mode was heretofore undetectable in structure-borne sound 
monitoring in nuclear power plants. 
By measuring this dissimilar dispersion behavior in the burst itself (in 
fact by doing so particularly in the case of anomalies as well), the 
components of the s.sub.0 mode and a.sub.0 mode can be identified. This 
can be done in the following manner: 
If a burst is transformed into the frequency band then, among others, there 
are contributions in virtually the entire frequency band, although 
pronounced peaks (resonances) occur at a few frequencies. If bandpass 
filters are then set to the pronounced peaks, or to portions of the 
more-continuous frequency spectrum, and the corresponding burst components 
are represented in the chronological range and the component onsets are 
measured in the usual manner, a series of times t.sub.i (f.sub.i) (i=1, . 
. . ) are obtained, to which the frequency F.sub.i is unequivocally 
assigned. After selection of an arbitrary value t.sub.n (f.sub.n) as a 
time reference, the rise time differences .DELTA.t.sub.i =t.sub.i 
(f.sub.i)-t.sub.n (f.sub.n) are plotted as a function of the frequency 
values f.sub.i. The result is a diagram that corresponds to either FIG. 3 
or 4, with FIG. 3 occurring for a reference point on the a.sub.0 mode 
curve and FIG. 4 occurring for a reference point on the s.sub.0 mode 
curve. It is therefore possible to unequivocally recognize which mode has 
to be assigned to the individual components of the burst at the various 
frequencies, from the signs (+ or -) and the course of the curves. Thus an 
unequivocal mode separation is theoretically possible. 
2.2 Mode separation and location in practice: 
In practice, somewhat different results can occur: 
(I) One of the modes may not occur at all. For instance, the corresponding 
components (over relatively long sound travel distances) may be damped too 
severely. Experience shows that this is most likely for the s.sub.0 mode. 
(II) At certain frequencies, .DELTA.t values which fall between the two 
curves also appear if both s.sub.0 and a.sub.0 modes contribute to the 
burst component in the selected frequency band. 
If only the a.sub.0 mode is present, as in (I), then making reference to 
equation (3) it is seen that because of its dispersion, various values 
.DELTA.t.sub.k =(D+L)(v.sub.k -v.sub.n)/v.sub.k .multidot.v.sub.n can be 
determined and assigned to sound frequencies. Since the structural 
component on which the pick-up is mounted (such as the reactor pressure 
vessel, steam generator, etc.) is known, the plate thickness and thus the 
velocities v.sub.k and v.sub.n belonging to the frequencies are also known 
according to the plate wave theory. The result is a value for D+L. If this 
is satisfied for the same result for the signals of a plurality of 
pick-ups, then for each of the pick-ups it follows that there is a value 
D.sub.i +L. At values having the same (arbitrarily selected) frequency and 
hence velocity v of the burst components in various pick-ups, the various 
rise time differences (between analogous burst components in various 
pick-ups) .DELTA.t.sub.lm can be formed, and it follows that: 
EQU t.sub.lm =(D.sub.l +L)/v-(D.sub.m +L)/v=(D.sub.l -D.sub.m)v.sup..multidot. 
(4); cf. (2) 
This can be utilized for determining the sound induction site. 
If as in (II) both modes (s.sub.0 and a.sub.0) are detected, and if two 
curves corresponding to FIG. 3 are present, or if at least the envelopes 
of the domain of possible rise time differences are recognizable, then the 
interval A of the curves or envelopes is obtained from the following: 
EQU A=(D+L)(v.sub.s -v.sub.a)/(v.sub.s .multidot.v.sub.a) (5); cf. (3) 
where for v.sub.s and v.sub.a once again the theoretical sound velocities 
given as a function of plate thickness, mode and frequency can be used, so 
that a value D+L follows. If different curve intervals A.sub.q and A.sub.p 
result for various pick-ups at the same frequencies and the same plate 
thickness, then 
EQU A.sub.q -A.sub.p =(D.sub.q -D.sub.p)(v.sub.s -v.sub.a)/v.sub.s 
.multidot.v.sub.a (6) 
and from that, once again, location of the sound induction is possible. 
3. Application of the Evaluation Method to Test Shock Bursts: 
3.1 Test shock on hot loop line of a PWR (pressurized water reactor): 
In FIG. 5, three examples of burst components after bandpass filtering 
operations are shown for a test impact on a hot loop line of a PWR. 
In column 3 of table 1, rise time differences that have been ascertained 
are listed, with the component at 8.5 kHz being used as a reference. These 
are only three values, nevertheless, an analysis in accordance with 
section 2 above is fundamentally possible. 
The three rise time differences are plotted in FIG. 6 as a function of the 
center frequency of the bandpass filter. A comparison of FIG. 6 with FIGS. 
3 and 4 unequivocally shows that the situation is as represented in FIG. 
4. In other words, the value at 5.75 kHz must be assigned to an a.sub.0 
mode, while the values at 3.75 kHz and 8.5 kHz are clearly s.sub.0 mode 
components. In column 4 of Table 1, the theoretical sound velocities 
corresponding to this assignment (taking into account the loop line wall 
thickness of 50 mm) are listed in accordance with FIG. 2. From the values 
of lines 2 and 3 a sound travel distance of 4.75+0.6 meters can then be 
calculated, the indicated error being based solely on the estimated 
uncertainty of 0.1 ms in the rise time difference determination. The 
ascertained sound travel distance is in agreement with the actual sound 
travel of 5.4 meters. 
3.2 Test shock on the reactor vessel of a BWR (boiling water reactor): 
As early as 1982, the firm Kraftwerk Union A.G. of Mulheim/Ruhr, West 
Germany studied some test shock data following (analog) filtering. For one 
shock, there were three relatively prominent peaks in the frequency band 
at 1.55 kHz, 3.8 kHz and 7.25 kHz, which were well separable with the 
analog technique, and some peaks at 8.9 kHz, which were not fully 
separated from the peak at 7.25 kHz. 
In Table 2 , column 3, the rise time differences of the burst components 
are listed, with the component at 8.9 kHz being used as a reference. These 
rise time differences are plotted in FIG. 7 as a function of the 
frequency. 
By comparison with FIGS. 3 and 4, the two burst components at 1.55 kHz and 
3.8 kHz are to be assigned to a.sub.0 mode components, while the other two 
values indicate the s.sub.0 mode. According to FIG. 2, the velocities 
listed in column 4 of the table are therefore to be expected. 
If the sound travel distance L.sub.S-A from the shock site to the pick-up 
is calculated using the values in the table, three values result: 
SW(1.55 kHz)=14.1 m 
SW(3.80 kHz)=13.9 m 
SW(7.25 kHz)=14.0 m. 
Initially it is highly satisfactory for the three sound travel or L.sub.S-A 
values to agree very well with one another. The actual sound travel 
distance of approximately 13.2 m is ascertained to approximately 6% 
accuracy. However, if the theoretical rise time differences are calculated 
afterward as a function of the burst component frequencies, using the 
now-known sound travel distance, the curves shown in dashed lines in FIG. 
7 are obtained, which once again confirms the above mode assignment. 
4. Findings, Conclusions and Advantages: 
Now that it has been demonstrated theoretically and with recourse to test 
shock data that in the location of shock events, the dispersion of the 
sound modes on one hand has a considerable influence on the accuracy, and 
on the other hand can be exploited in order to find the actual sound 
velocities from the bursts themselves, the following conclusions and 
advantages can be stated: 
(1) Analyses of bursts should always be performed in the frequency band as 
well, or after bandpass filtering operations. The novel analysis method 
that is thereby possible, with simultaneous determination of the sound 
velocities from the signals themselves, allows reliable locations, and as 
a result, decisive improvements in the evaluation of a source of 
anomalies, with faster prevention of threatened damage as necessary 
(maintaining plant operability) and with less radiation exposure during 
repairs. 
(2) The novel analysis method permits adequate locations of the shock site 
as well of the sound induction site, with only a few pick-ups. 
(3) It is unnecessary to derive reference velocities from test shocks. 
(4) During inspection, for instance, fewer shock sites than before (in 
other words, less radiation exposure) are needed for functional testing of 
the pick-ups. 
(5) In the context of the invention, computer-supported automatic analyses 
of the proposed type can be performed and are useful. This could 
advantageously be done in such a way that approximately 10 bandpass values 
in the frequency band of the monitoring are predetermined, the 
corresponding burst components are automatically separated in the 
chronological range, and the time differences are ascertained using 
correlation methods. If the few parameters relating to wall thicknesses, 
etc., are also predetermined, then in principle the computer could also 
ascertain the sound velocities directly, even during anomalous events. 
5. Table 1 and Table 2: 
TABLE 1 
______________________________________ 
Summary of the data of three burst components for 
one test shock on the hot loop line of a PWR 
Theoretical 
Center frequency Rise time velocities and 
of the bandpass, 
Parameter d.f, 
difference 
sound mode in 
in kHZ in mm MHz t in ms m/ms 
______________________________________ 
3.75 0.19 0.0 s.sub.0 : 5.4 
5.75 0.29 0.8 a.sub.0 : 2.8 
8.50 0.43 0.0 s.sub.0 : 5.3 
(reference) 
______________________________________ 
TABLE 2 
______________________________________ 
Summary of the data of burst components for one test 
shock on the hot loop line of a BWR pressure vessel 
Theoretical 
Center frequency Rise time velocities and 
of the bandpass, 
Parameter d.f, 
difference 
sound mode in 
in kHZ in mm MHz t in ms m/ms 
______________________________________ 
1.55 0.26 2.6 a.sub.0 : 2.4 
3.80 0.65 1.4 a.sub.0 : 3.0 
7.25 1.24 -0.4 s.sub.0 : 4.9 
8.90 1.52 0.0 s.sub.0 : 4.3 
(reference) 
______________________________________ 
The foregoing is a description corresponding in substance to German 
Application P No. 37 02 879.0, dated Jan. 31, 1987, the International 
priority of which is being claimed for the instant application, and which 
is hereby made part of this application. Any material discrepancies 
between the foregoing specification and the aforementioned corresponding 
German application are to be resolved in favor of the latter.