The efficiency assessment of the state system of nuclear safety control of NSC-SO
According to the results of a comprehensive analysis, it was found that the nuclear safety monitoring system (NSMS) does not fully comply with the requirements put forward to it. By assessing the sufficiency of the detection points of this monitoring system, it was found that there is no monitoring...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2020 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2020
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| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | The efficiency assessment of the state system of nuclear safety control of NSC-SO / R.L. Godun, A.O. Doroshenko, D.О. Muliar // Problems of atomic science and tecnology. — 2020. — № 2. — С. 71-80. — Бібліогр.: 24 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859981485883260928 |
|---|---|
| author | Godun, R.L. Doroshenko, A.O. Muliar, D.О. |
| author_facet | Godun, R.L. Doroshenko, A.O. Muliar, D.О. |
| citation_txt | The efficiency assessment of the state system of nuclear safety control of NSC-SO / R.L. Godun, A.O. Doroshenko, D.О. Muliar // Problems of atomic science and tecnology. — 2020. — № 2. — С. 71-80. — Бібліогр.: 24 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | According to the results of a comprehensive analysis, it was found that the nuclear safety monitoring system (NSMS) does not fully comply with the requirements put forward to it. By assessing the sufficiency of the detection points of this monitoring system, it was found that there is no monitoring at the cluster of nuclear fissile materials (NFM) in the central hall and at the "northern" cluster in 305/2 rooms. The effectiveness of monitoring the "southern" cluster of NFM in the room. 305/2 is insufficient and does not comply with the standards regulated by the rules of nuclear safety. Also, a number of other requirements to the NSMS (as the emergency alarm systems of the spent nuclear waste storage facility) are not fulfilled. It is proposed to re-arrange the measuring channels (MC) of the system, decommission excess (non-informative) MC and use their equipment to organize new effective monitoring points; to upgrade the software and arrange individual ground of the system to reduce the influence of high-frequency interference.
За результатами комплексного аналізу встановлено, що система контролю ядерної безпеки (СКЯБ) у повному обсязі відповідає висунутим до неї вимогам. За оцінкою достатності точок детектування цієї регламентної системи встановлено, що відсутній моніторинг скупчень ядерно-небезпечних матеріалів, що діляться (ЯНДМ), у центральному залі і «північного» скупчення ЯНДМ в приміщенні 305/2. Ефективність моніторингу «південного» скупчення ЯНДМ у приміщенні 305/2 недостатня і не відповідає нормам, що регламентуються «Правилами ядерної безпеки» (ПЯБ). Також не виконується ряд інших вимог до СКЯБ як системи аварійної сигналізації сховища відпрацьованих ядерних відходів. Пропонується виконати перекомпонування вимірювальних каналів (ВК) системи, вивести з експлуатації надлишкові (неінформативні) ВК і використовувати їх обладнання для організації нових ефективних точок моніторингу; провести модернізацію програмного забезпечення та організувати індивідуальне заземлення системи, щоб знизити вплив високочастотних наведень і перешкод.
По результатам комплексного анализа установлено, что система контроля ядерной безопасности (СКЯБ) не полностью соответствует выдвигаемым к ней требованиям. По оценке достаточности точек детектирования этой регламентной системы установлено, что отсутствует мониторинг скоплений ядерноопасных делящихся материалов (ЯОДМ) в центральном зале и «северного» скопления ЯОДМ в помещении 305/2. Эффективность мониторинга «южного» скопления ЯОДМ в помещении 305/2 недостаточна и не соответствует нормам, регламентируемым «Правилами ядерной безопасности» (ПБЯ). Также не выполняется ряд других требований к СКЯБ как системы аварийной сигнализации хранилища отработанных ядерных отходов. Предлагается выполнить перекомпоновку измерительных каналов (ИК) системы, вывести из эксплуатации избыточные (неинформативные) ИК и использовать их оборудования для организации новых эффективных точек мониторинга; произвести модернизацию программного обеспечения и организовать индивидуальное заземление системы, чтобы снизить влияние высокочастотных наводок и помех.
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| first_indexed | 2025-12-07T16:26:03Z |
| format | Article |
| fulltext |
ISSN 1562-6016. PASТ. 2020. №2(126), p. 71-80.
UDC 621.039
THE EFFICIENCY ASSESSMENT OF THE STATE SYSTEM
OF NUCLEAR SAFETY CONTROL OF NSC-SO
R.L. Godun, A.O. Doroshenko, D.О. Muliar
Institute for Safety Problems of Nuclear Power Plants NAS of Ukraine,
Chornobyl, Ukraine
E-mail: ispnpp@ispnpp.kiev.ua; fax 5-14-34, tel. (04593) 5-10-44
According to the results of a comprehensive analysis, it was found that the nuclear safety monitoring system
(NSMS) does not fully comply with the requirements put forward to it. By assessing the sufficiency of the detection
points of this monitoring system, it was found that there is no monitoring at the cluster of nuclear fissile materials
(NFM) in the central hall and at the “northern” cluster in 305/2 rooms. The effectiveness of monitoring the
“southern” cluster of NFM in the room. 305/2 is insufficient and does not comply with the standards regulated by
the rules of nuclear safety. Also, a number of other requirements to the NSMS (as the emergency alarm systems of
the spent nuclear waste storage facility) are not fulfilled. It is proposed to re-arrange the measuring channels (MC)
of the system, decommission excess (non-informative) MC and use their equipment to organize new effective
monitoring points; to upgrade the software and arrange individual ground of the system to reduce the influence of
high-frequency interference.
INTRODUCTION
Nuclear safety (NS) of the New Safe Confinement
(NSC) complex can be ensured only if there is effective
monitoring of the neutron activity of clusters of nuclear
hazardous fissile materials (NHFM) in the premises of
the Shelter object (SO) formed as a result of a severe
beyond design basis accident at the fourth power unit
Chernobyl nuclear power plant.
The NSMS of the Integrated Automated Monitoring
System (IAMS) successfully passed metrological
certification and was put into experimental testing in
2014, and from 2016 to regular operation. NSMS IAMS
continuously (in automatic mode) registers the neutron
flux density (NFD) and the gamma dose rate (GDR)
inside the NSC-SO complex and accumulates the
measurement results in a centralized database, as a
result of which there are continuous regular series of
data allowing the analysis of these parameters.
According to the results of the analysis of continuous
monitoring of NFD, it was found that in some
measuring channels (MC) there are periods when there
are no measurements, and in some MC there are sharp
jumps in the recorded neutron activity (Fig. 1).
Fig. 1. The dynamics of NFD in MC NSMS, in which unauthorized operator intervention
The absence of NFD measurements is due to the fact
that these MC are taken out of operational service, while
there is no backup equipment, which does not allow for
continuous measurement of parameters, and also in the
event of failure of the MC elements, they can be
restored to serviceability during the routine 72 h.
Regarding drastic changes recorded by the NFD, they
are not associated with real physical processes within
the controlled facility, but only with the intervention of
operational personnel. These jumps are most likely the
result of changes in the discriminatory characteristics in
the NSMS (changes in the discrimination thresholds)
and/or non-observance of the exact coordinates of the
installation of the detection units (DU) when they are
reinstalled, which with a strong dependence of the
fission chamber (FC) on the neutron spectrum
(estimated by the cadmium ratio - Rcd) leads to a
significant change in the recorded NFD [1].
In any case, both variants of such interventions in
the operation of the metrologically certified nuclear
safety system of the NSC-SO complex are an
unauthorized violation of the operating conditions of the
NSMS and should be excluded in the future.
The relevance of the study to evaluate the
effectiveness of the work of the NSMS is mainly
determined by the fact that at the moment the issue of
nuclear safety is not given due attention. The last
comprehensive analysis of the nuclear safety factor was
performed in 2009 [2]. After that, the operator of the
ChNPP provides only short informational reports [3–5],
in which several (3–4) pages are devoted to the problem
of nuclear safety. The following information is provided
in these reports: localization of the monitoring points of
the regulatory NSMS, the measurement results of some
non-informative MC, and indicates that the operational
control function of dangerous changes in subcritical is
assigned to the gadolinium solution supply system and
the modernized dust suppression system. The
conclusions of these reports state that “... there are no
anomalies or incidents, which are caused by the
constant increase in the power of the NFD, and control
systems for the free period are not fixed ...”. Thus, the
fact is ignored that in several MC for more than two
years there has been a constant increase in NFD from 20
to 90% (Fig. 2).
Considering the fact that the nuclear research and
storage facilities are poorly researched and controlled
(there is no direct access to them) in the central hall and
room 305/2, which, according to various estimates, has
about 80 tons of spent nuclear fuel (SNF) [6–8] (which
is more than enough for the formation of a critical
composition), then we can state the following: this
situation is unacceptable because now the SO does not
meet the generally accepted safety requirements put
forward to the complex NSC-SO (nuclear hazardous
facility).
Fig. 2. Measuring channels with stable NFD growth
ANALYSIS OF COMPLIANCE WITH NSMS
REGULATORY REQUIREMENTS
The current state of the SO [9] is qualified as
follows: “SO is the 4th Chernobyl NPP unit destroyed
by a beyond design basis accident, which lost all the
functional properties of the power unit and on which
priority measures were taken to reduce the
consequences of the accident, and work is continuing to
ensure its nuclear and radiation safety ”[10]; SO in its
current state should be classified as “... the temporary
storage of non-organized radioactive waste (RW), is in
the process of stabilization and reconstruction” [11].
From the above provisions, it follows that activities
at the SO (NSC) are radioactive waste management
activities. Accordingly, regulation of its safety should
be carried out on the basis of regulatory legal acts and
scientific and technical documentation [12, 13]
operating in the field of radioactive waste management.
Thus, in order to comply with the basic principles and
the nature of technical and organizational measures
aimed at achieving nuclear and radiation safety, for the
NSC-SO complex to apply the “Nuclear Safety Rules”
(NSR) [14] and [15, 16]. NSR-90/99 to the NSMS as an
alarm system for the radioactive waste storage facility
(nuclear hazardous facility) is regulated by the
following requirements:
1. “If the nuclear hazard zone includes a collection
of separate buildings or adjacent rooms, then the
detection units (DU) and alarm devices are installed in
those buildings and rooms where the possibility of a
self-sustaining chain reaction (SCR) is not excluded”
(paragraph 2.2.7).
2. The threshold for the operation of alarm systems
in accordance with clause 2.2.2 is determined by the
requirement to detect a minimum SCR, which creates a
dose of 0.25 Gy (25 rad) for no more than 60 s at a
distance of 1 m from the place of occurrence in the
absence of absorbing screens (i.e., during the accepted
maximum duration of the SCR peak). Moreover,
“response thresholds in NFD units should be determined
to take into account the energy dependence of their
spectrum and the sensitivity of the DU” (paragraph
2.2.4).
3. The angular dependence of the efficiency of the
DU of the detected radiation should be no more than
25% and is given in the documentation for these DU
(paragraph 2.2.10).
4. Alarm systems should be designed, manufactured
and placed (mounted) in such a way as to ensure its
reliable and long-term continuous operation in a
production environment (paragraph 2.5.1).
Based on the results of the analysis of NSMS, the
following conclusions are made:
1. The requirements of paragraph 2.2.7 of the NSR
are not fulfilled, since the availability of effective
monitoring points in all rooms where "the likelihood of
an SCR is not excluded" is not implemented. More
detailed information is presented in the section
“Assessment of the sufficiency and effectiveness of
detection points for the SO nuclear safety system”.
2. The requirements of paragraph 2.2.2 are also not
fulfilled, which will be justified below. Moreover,
according to the NSR “if the system is based on
recording the dose rate of the neutron radiation, the
response threshold should not exceed 1/r
2
mGy/s (r is
the distance in meters from the place of the possible
occurrence of the SCR to the DU), and the dose of
neutron radiation should be up to the moment of
operation of the unit detection should be no more than
3/r
2
mGy”. The requirements of paragraph 2.2.4 are also
not fulfilled because the NFD at the control points
should be determined to take into account the individual
energy dependence of the spectrum and the sensitivity
of each DU. For the DU NSMS (FC216 / 2000 / U235),
spectral dependences were not obtained under the real
conditions of the NSC-SO. The existing spectral
dependences (constructed for the FC KNT-31) were
taken on the basis of the analogy method. FC NSMS
and KNT-31 have a number of differences in the
characteristics of the radiator (active layer consisting of
uranium isotopes), therefore, this should be verified
experimentally.
3. The requirements of 2.2.10 are not fulfilled,
because according to the technical documentation [17]
on NSMS, the DU efficiency has a strong angular
dependence (when the neutron beam changes by 90°,
the response changes by a factor of 7–8).
4. The requirements of paragraph 2.5.1 are not
fulfilled (see Fig. 1), in addition, the lack of backup
equipment (at the moment there is only one incomplete
set for 19 MC in the reserve) in the event of a failure of
one of the equipment, it will not allow to restore the
System within a permissible 72 h.
ASSESSMENT OF THE SUFFICIENCY AND
EFFECTIVENESS OF DETECTION POINTS
FOR THE SO NUCLEAR SAFETY SYSTEM
NSMS is a complex of 19 MC that register of NFD
and GDR at the control points. At the same time, a part
of the MC equipment (detectors, preliminary and main
amplifiers, etc.) was designed for use in standard
monitoring channels NFD of nuclear power reactors
(the equipment is designed for large neutron fluxes),
which does not correspond to the current operating
conditions.
The control of GDR (as a parameter concomitant
with neutron activity from accumulations of NHFM) is
not informative. This is due to the fact that the GDR
level by gamma radiation from fission events and decay
chains of fission fragments is orders of magnitude lower
than the level detected by the gamma background (the
monitoring points of the routine NSMS IAMS are in
fields with GDR values of several hundred/thousand x-
rays). According to the calculations, when SCR occurs
at the regulatory monitoring points, reliable registration
of GDR changes (detectable excess over the background
level) is possible only with a number of divisions of the
order of 10
15
...10
16
, which (taking into account the
increasing kinetics/speed in the near-critical zone) does
not allow using this parameter to prevent the occurrence
of SCR [18].
In the regular system of IAMS, temperature control
at the places of accumulation of fuel-containing
materials (FCM) was not provided. Although this
control parameter (temperature) is not the main criterion
in assessing the stability state of FCM clusters, the data
on temperature fields in the SO rooms provide a general
idea of temporary changes in energy release from the
FCM cluster and are taken into account when assessing
the boundaries of FCM clusters.
Fig. 3. Localization of monitoring points for MC NFD NSMS
In the report on the results of the analysis of the
current SO safety [19–21], based on experimental and
calculated estimates, the premises were classified
according to the degree of nuclear hazard of FCM
accumulations located in them. The following premises
were identified as potentially nuclear-hazardous the
central hall (CH), the southern exposure pool, the
reactor shaft, and the underreactor room 305/2. In these
rooms, “the existence of compositions in which the
occurrence of SCR is fundamentally possible” was
allowed.
At the same time, current monitoring of the FCM
NFD inside the NSC-SO complex is carried out (Fig. 3)
in the following rooms: reactor space (at elevations
from +15.00 to +22.00); 305/2 (at elevations +12.00;
+9.00); 304/3 (at +10.00); steam distribution corridor (at
+ 6.50); the southern exposure pool (at +19.00 and
+22.00); in tunnels under the central lock (at +33.00).
The standard detection points for NSMS, which
were selected according to the recommendations of
2001 [23], are currently largely uninformative for the
purpose of providing nuclear safety since over the past
15 years the information on the parameters and
localization of the main clusters of NHFM has changed
significantly. Now the most potentially dangerous is the
central hall and room 305/2 [22]. The estimated area of
accumulation of NHFM in the CH requiring continuous
monitoring is limited by the following coordinates:
altitude level from 35.00 m to 37.00 m, between the
axes 40.00 – 46.00, rows I – N, the coordinate system
4th unit of the ChNPP. In this zone, the nearest neutron
detectors (DU NFD No. 017, 018, 019) of the NSMS
are installed in the tunnels under the lower central
overlap (altitude 33 m) and are uninformative due to
weakening (at least 103 times less) of the FC response
to neutron incident. Thus, the DU NSMS will not
respond in a timely manner to changes in neutron
activity with the possible occurrence of SCR, and the
cluster of FCM in the CH is not currently monitored.
Also, NSMS has practically no control over the
“northern” NHFM cluster in room 305/2, which is
clearly visible on temperature field maps (Fig. 4). There
are no monitoring points in the zone of localization of
this potentially nuclear hazardous cluster.
Fig. 4. Temperature fields in the area of localization of NHFM
(top view of the underreactor plate, mark +9.00)
In the zone of localization of the “southern” cluster
of NHFM in room 305/2, the closest to the source are
the DU MC NFD No. 01, 03 and 04 (Fig. 5), while:
1. Detector MC NFD No. 1 is installed through
borehole Yu-12-78 (in the space above the zone of
location of the FCM cluster) at +12.00 and the partition
environment between the DU and the NHFM cluster are
black LFCM layer (0.6 m), layer (0.8 m) of heavy
concrete and 1.5 m of air.
2. Detector MC NFD No. 3 is installed in the
concrete of the underreactor plate (in borehole Z-9-F) at
the level of + 9.30 m and the partition environment
between the DU and the NHFM cluster are a layer
(1.5 m) of heavy concrete and a layer (1, 0 m) LFCM.
3. Detector MC NFD No. 4 is installed in room
304/3 (through borehole Z-10-G) on the surface of the
LFCM (elevation + 9.70) and the partition environment
between the DU and the NHFM cluster is: a layer
(2.5 m) of LFCM or meter heavy concrete layer.
Fig. 5. The estimated cross-section in the zone of localization of the “southern” cluster of NHFM in room 305/2,
indicating the localization of the nearest NSMS DU
The informational sufficiency of the obtained data
on the subcritical state of NHFM clusters primarily
depends on the location of the detectors relative to the
controlled sources, because the radiation of neutrons
and gamma rays of the sensor (due to their absorption in
FCM, structures, etc.) is effectively recorded only in a
limited distance (Table 1).
Table 1
The maximum value of the response threshold of the DU and the maximum distance from the DU
to the place of the possible occurrence of SCR at various absorbing thicknesses materials located between
the DU and the location of the SCR [16]
The thickness of the
absorbing material, m
Registered radiation – neutrons, absorbing material - concrete
The maximum distance from the DU to the
place of the possible occurrence of SCR, m
The maximum value of the DU response
threshold, μRad/s
ρ = 2.2 ρ = 3.2 ρ = 4.2 ρ = 4.2 ρ = 3.2 ρ = 4.2
0 30 100 100 100 30 30
0.40 10 11 4 4 5 6
0.50 7 5 1 1 3 3
0.60 4 2 – – 1 1
0.70 3 1 – – – –
Note: ρ – this is the density of the material in units of t/m3; given distances are conservatively rounded to integer values;
linear interpolation of data is allowed to determine intermediate values.
Thus, it is necessary to carry out calculations in
order to assess the conformity of the detection points of
the NSMS with the requirements of paragraph 2.2.2–
2.2.5 [15, 16]. In this case, the location of the DU
should be selected in such a way as to avoid affecting
the choice of thresholds for the operation of significant
absorption of the recorded radiation by structural
materials, equipment, walls of premises. The influence
of absorption is allowed to be neglected when its
multiplicity is not more than 1.5. If it is impossible to
eliminate significant absorption of radiation from the
site of the possible occurrence of the SCR to the
detection units, the latter must be brought closer to the
controlled equipment or the threshold of the system
should be lowered so that the requirements of the above
points are satisfied.
Based on the results of assessments of the distance
from the "southern" cluster of NHFM to the DU of the
MC NSMS, as well as the partitioned environment
between them, it was concluded that these detection
points do not meet the regulated requirements of the
NSR regarding the maximum distance from the DU to
the place of the possible occurrence of SCR.
As intermediate results, it can be argued that the
existing information capacity of the NSMS is
insufficient due to the lack of:
– control points in the zone of localization of NHFM
clusters, “in which the occurrence of SCR is possible”
(CH, “northern” cluster in room 305/2), as well as low
efficiency/informational content of control points in the
zone of localization of the potentially most dangerous
“southern” cluster NHFM of room 305/2, in which
about 20 tons of spent fuel in a compact composition
[22];
– duplication of detection points in the localization
zone of NHFM (production facilities, temporary storage
sites for NHFM, where SCR may occur, should be
monitored by at least two independent DU. The DU is
accepted independent if the failure of any of them does
not affect the operability of others. Alarm should trigger
from any of the two DU [16]).
In addition to the analysis of the adequacy of the
control points of the NSMS, an analysis was made of
the location of each DU of the MC NSMS, according to
the results of which the following was established:
1. DU MC NFD No. 01 (BH U-12-78), 03 (BH Z-9-
F), 06 (BH Z-9-68), 07 (BH Z-16-61), 04 (BH Z-10 -G),
10 (BH Yu-9-D), 11 (BH Z-15-D) and 15 (BH Z-15-Zh)
are located in the localization zone of the main clusters
of NHFM, therefore, they can be used to control their
subcritical.
2. Due to the spatial distance from potentially
dangerous accumulations of NHFM, detectors MC NFD
No. 05 (BH Z-9-Zh), 08 (BH V-21-96), 09 (BH V-19-
103), 12 (BH Z-15 -B), 14 (BH Z-9-Ch), 16 (BH 3-22-
B), MC No. 17–19 are practically uninformative. This is
especially true for BH No. 17–19, in which there is no
controlled parameter. The DU of these MC NSMS is
located on the periphery of FCM clusters in which the
occurrence of SCR is impossible [18–22]. Thus, the
current circuit of the detection points of the NSMS is
unnecessary, not effective, and should be adjusted.
It should also be noted that the neutron detectors and
GDR sensors of the MC NSMS are located in research
borehole (BH) in different rooms throughout the entire
volume of the NSC-SO complex. To isolate the DU
from the negative effects of water, MC is cased (sealed)
with pipes. It was shown in [24] that during the
preparation of MC for NSMS, their available depth
decreased significantly due to their sealing with casing
pipes; therefore, DU NSMS is located further from the
localization zones of NHFM clusters. In this regard,
several of the most informative points were lost,
because due to sealing there were restrictions on the
depth of the possible installation of the DU. For
example, in MC NFD No. 02 (BH Z-9-K), 13 (BH Z-
15-V), 15 (BH Z-15-Zh) the monitoring efficiency was
lost due to the inability to install sensors at informative
points after execution BH casing (Fig. 6).
The green line marks the current (determined by the casing depth) coordinate of the DU center,
purple – optimal
Fig. 6. The expected values of NFD and Rcd along the length of the BH Z-9-K, in which the DU NFD No. 02 (a)
is installed and for the BH Z-9-V DU NFD No. 13 (b)
The recorded NSMS NFD is obtained by
multiplying the MC sensitivity coefficient by the count
rate in this channel. The sensitivity coefficients of each
MC NFD are individual and are estimated by the
measured Rcd value at the monitoring point, the values
of which can vary greatly along with the depth of the
MC (see Fig. 6). The last measurements of cadmium
ratios (see Fig. 6) in the MC in which the detectors were
installed were performed in 1989–1990. In this regard, it
is desirable to re-conduct the work on the experimental
removal of Rcd depending on the depth of installation
(from the wellhead) of the FC (Fig. 7).
Fig. 7. The dependence of the cadmium ratio from the
coordinates of the FC installation in MC No. 05
b
RECOMMENDATIONS FOR BETWEEN
NSMS IAMS IN ACCORDANCE WITH
REGULATED REQUIREMENTS, AND ALSO
INCREASING ITS EFFICIENCY
Obviously, in the localization zone of each NHFM
cluster, the total number and location of the monitoring
centers for NSMS is determined by the real possibilities
of their approach to a controlled source and financial
possibility. The greatest monitoring efficiency would be
obtained when the detectors were installed directly in
the volumes of NHFM clusters, however, this is a
complex and expensive technological task, which is
now difficult to solve in the current realities. Therefore,
a set of optimal and economically acceptable measures
has been proposed that can significantly increase the
effectiveness of the NSMS and bring it in line with
regulatory requirements.
1. Improving the efficiency of NSMS is possible by
optimizing/correcting MC and changing the localization
of some DU. It is proposed to decommission non-
informative (for the purpose of providing NS) MC NFD
No. 12-19. It is proposed to use the “freed up”
equipment of these MC for organizing new effective
detection points and/or as backup equipment for
restoring the operability of informative MC.
2. An increase in the information content of NSMS
can be achieved due to the maximum approximation of
the location of the DU of existing MC sources to the
sources (table 2) and the implementation of new
informative points for detecting NFD (primarily in
rooms 305/2 and CH). The effectiveness of monitoring
the neutron activity of the "southern" cluster of NHFM
in room 305/2 can be improved by removing the casing
from the BH Z-9-K, Z-9-Zh and further reinstalling the
DU located in them at more informative points (located
closer to the source ) Monitoring of the neutron activity
of the “northern” cluster of NHFM in room 305/2 can
be realized after the detectors are installed in room
307/2 through the BH 3-9-V and V-13-106.
Table 2
Parameters of the current MC casing used to install the DU NSMS
Number
MC NSMS
Brief description of the borehole Depth of
detector
installation,
m
Recommendations Design drilling depth,
m
Real casing depth,
m
MC NFD N 1 13.0 11.3 11.1 –
MC NFD N 2 12.5 12.6 12.4 –
MC NFD N 3 16.3 13.9 13.7 –
MC NFD N 4 >15 14.4 14.2 –
MC NFD N 5 13.7 9.8 9.6 –
MC NFD N 6 14.1 12.7 9.5 Move 3 m (all the way)
MC NFD N 7 11.2 11.2 11.0 –
MC NFD N 8 10.76 10.5 10.2 –
MC NFD N 9 11.1 12.0 11.8 –
MC NFD N 10 14.5 12.2 11.1 Move 0,9 m (all the way)
MC NFD N11 12.5 14.2 14.0 –
3. It is proposed to test the informati-
veness/effectiveness of the new detection points for
NFD with the help of the currently working expert
research system of the Institute for Safety Problems of
NPPs.
4. In order to reliably ensure monitoring of overhead
protection and compliance with the requirements of the
NSR, it is necessary to ensure duplication/redundancy
of monitoring points for overhead protection. Also, in
the localization zone of the potentially most dangerous
clusters of nuclear weapons (room 305/2 and CH), it is
desirable to implement such a number of information
points that the requirement of mutual overlap of the
monitored FCM arrays is fulfilled, which will make it
possible to repair or maintain one of the detectors.
Therefore, in the localization zone of each cluster of
NHFM, there must be at least three DU. At the same
time, the requirement of mutual overlap of the
controlled volumes of FCM means that the expected
rate of attenuation of the response to the anomaly at the
nearest detectors should not exceed one order. The
degree of mutual overlap of the observation zones of the
detectors is proposed to be estimated experimentally
(using the short-term introduction of an external neutron
source at points with determined coordinates). This
approach is caused by the fact that the attenuation of the
response of the detector to the source is purely
individual for each information point of the controlled
object, which is associated with different “geometry of
the source-receiver mutual arrangement” (different
distance and angular orientation), as well as with
various absorbing properties of a particular interface
between the source and DU.
5. For reliability of nuclear safety (NFD
monitoring), it is also necessary to purchase several
spare MC kits so that in the event of a single equipment
failure it would be possible to restore the MC
operability during the regulated 72 h.
6. A layout of detection points and access routes to
them in the central hall is proposed (Table 3), the
implementation of which will provide a function for
effective monitoring of the state of subcritical in the
areas where NHFM clusters are located. The optimal
routes for the delivery of detectors to detection point
No. 2–4 are penetrations in the pipe run of the roof.
Through these penetrations, detectors can be hung out in
the given coordinates (at elevations from +36.00 m to
+37.00 m). Detectors can be delivered to the lower floor
via well Yu-22-129 from room 515/3. Detectors can be
connected to the monitoring system through cable lines
that go to rooms 6004 and 208/10. The location of the
preamplifiers must be determined in the working order
based on restrictions on the length of the permissible
distance between the detector and the preamplifier.
Table 3
Location and access routes to detection points in the areas where potentially dangerous nuclear fuel assemblies FCM
are located in CH
P
o
in
t
n
u
m
b
er
co
n
tr
o
l
p
ar
am
et
er
Control Point Coordinates
Delivery
route
Route Characteristics Cable exit address
Altitude Coordinates Beginning Coordinates
Diameter,
mm
No.
room.
No.
box
1
NFD,
GDR
+35.00 К; 42
Slant
borehole
515/3 И43; 22 127 208/10 Д11
2
NFD,
GDR
+37.00 К-Л; 45-46 Sunroof Pipe roll
К-Л; 45–46;
отм. +72,00
200 6004 Д5
3
NFD,
GDR
+37.00 Л-М; 45-46 Sunroof Pipe roll
Л-М; 44-45;
отм. +72,00
200 6004 Д5
4
NFD,
GDR
+37.00 Л-М; 40-41 Sunroof Pipe roll
Л-М; 40-41;
отм. +72,00
200 6004 Д5
CONCLUSION
Based on the results of a comprehensive analysis, it
was established that NSMS (as a system of routine
monitoring of the nuclear safety of a SO — a temporary
storage facility of SNF) does not fully meet the
requirements put forward by it, in particular: monitoring
of all NHFM clusters in the scope of which the
occurrence of SCR is possible (CH and room 305/2);
the requirement for the maximum distance from the DU
to the point of the possible occurrence of the SCR is not
complied with; individual response thresholds for
specific detection points were not evaluated (not
calculated); the requirement that “NFD at the control
points should be determined to take into account the
individual energy dependence of the spectrum and the
sensitivity of each DU” has not been practically fulfilled
since the decision to use the characteristics of other
fission cameras has not been verified/confirmed (KNT-
31). In addition, the efficiency of the FC MC NFD
NSMS (FC216/2000/U
235
) has a strong angular
dependence, significantly exceeding the permissible;
there is no backup/spare equipment, which in the future,
in the event of a single failure of the MC, will inevitably
lead to a violation of the requirement for continuity of
measurements. In addition, unacceptable violations of
the rules/norms of operation of the attorney/certified
regulatory system for monitoring a nuclear hazardous
facility are recorded, namely: unauthorized
interventions in the measuring and converting paths of
the MC (changes in discrimination thresholds –
attenuation coefficients); non-informative data are
transferred to the controlling state bodies, while
dangerous changes in the dynamics of the NFD, which
have been recorded for more than two years, are
ignored.
There are other problems: the measuring equipment
of the NSMS is not provided with individual ground,
but is grounded to the general circuit of the SO, which
significantly reduces the noise immunity of the MC
system (there are interference in the MC); During the
MC casing, informative points were lost, and the
existing control points are not optimal. A set of optimal
and economically acceptable priority measures has been
proposed that can significantly increase the
effectiveness of the NSMS and bring it in line with
regulatory requirements.
Firstly, according to the results of a comprehensive
analysis, it was established that there is “unnecessary”
MC whose DU is located far from the accumulations of
NHFM and do not participate in the function of
providing nuclear safety SO. Therefore, it is necessary
to carry out a set of works to evaluate the effectiveness
of the NSMS, decommissioning of these
“unnecessary”/non-informative MC, and rearrange the
NSMS to organize new effective monitoring points with
the possibility of using this vacant equipment as a
backup. The information content of the new monitoring
points can be checked using the expert research system
of the Institute for Safety Problems of NPPs. To
increase the efficiency of NFD measurements, it is
proposed to change the installation coordinates (along
with the depth of the MC) of neutron radiation detectors
(see Table 2). In addition, it is necessary to carry out
evaluative calculations of the adequacy of the control
points of the NSMS taking into account the
requirements of paragraph 2.2.2–2.2.5 [16], as well as
evaluate/calculate the system's compliance with the
requirements of duplication and the condition for
overlapping nuclear hazardous areas.
It is also necessary to upgrade the software of the
NSMS, for which the following is proposed: consider
introducing new filters to improve noise immunity (for
reliable rejection of knowingly false measurement
results caused by high-frequency interference); To
identify dangerous changes in the subcritical at the early
stages of development, it is necessary to develop and
implement an effective (taking into account the two-
layer structure of FCM clusters) procedure for
identifying dangerous changes in the level of subcritical
in the most potentially dangerous clusters of nuclear
weapons located in room 305/2.
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Article received 18.02.2020
ОЦЕНКА ЭФФЕКТИВНОСТИ РЕГЛАМЕНТНОЙ СИСТЕМЫ КОНТРОЛЯ ЯДЕРНОЙ
БЕЗОПАСНОСТИ КОМПЛЕКСА НБК-ОУ
Р.Л. Годун, А.А. Дорошенко, Д.А. Муляр
По результатам комплексного анализа установлено, что система контроля ядерной безопасности (СКЯБ)
не полностью соответствует выдвигаемым к ней требованиям. По оценке достаточности точек
детектирования этой регламентной системы установлено, что отсутствует мониторинг скоплений ядерно-
опасных делящихся материалов (ЯОДМ) в центральном зале и «северного» скопления ЯОДМ в помещении
305/2. Эффективность мониторинга «южного» скопления ЯОДМ в помещении 305/2 недостаточна и не
соответствует нормам, регламентируемым «Правилами ядерной безопасности» (ПБЯ). Также не
выполняется ряд других требований к СКЯБ как системы аварийной сигнализации хранилища отработанных
ядерных отходов. Предлагается выполнить перекомпоновку измерительных каналов (ИК) системы, вывести
из эксплуатации избыточные (неинформативные) ИК и использовать их оборудования для организации
новых эффективных точек мониторинга; произвести модернизацию программного обеспечения и
организовать индивидуальное заземление системы, чтобы снизить влияние высокочастотных наводок и
помех.
ОЦІНКА ЕФЕКТИВНОСТІ РЕГЛАМЕНТНОЇ СИСТЕМИ КОНТРОЛЮ
ЯДЕРНОЇ БЕЗПЕКИ КОМПЛЕКСУ НБК-ОУ
Р.Л. Годун, А.О. Дорошенко, Д.О. Муляр
За результатами комплексного аналізу встановлено, що система контролю ядерної безпеки (СКЯБ) у
повному обсязі відповідає висунутим до неї вимогам. За оцінкою достатності точок детектування цієї
регламентної системи встановлено, що відсутній моніторинг скупчень ядерно-небезпечних матеріалів, що
діляться (ЯНДМ), у центральному залі і «північного» скупчення ЯНДМ в приміщенні 305/2. Ефективність
моніторингу «південного» скупчення ЯНДМ у приміщенні 305/2 недостатня і не відповідає нормам, що
регламентуються «Правилами ядерної безпеки» (ПЯБ). Також не виконується ряд інших вимог до СКЯБ як
системи аварійної сигналізації сховища відпрацьованих ядерних відходів. Пропонується виконати
перекомпонування вимірювальних каналів (ВК) системи, вивести з експлуатації надлишкові
(неінформативні) ВК і використовувати їх обладнання для організації нових ефективних точок моніторингу;
провести модернізацію програмного забезпечення та організувати індивідуальне заземлення системи, щоб
знизити вплив високочастотних наведень і перешкод.
|
| id | nasplib_isofts_kiev_ua-123456789-194366 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T16:26:03Z |
| publishDate | 2020 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Godun, R.L. Doroshenko, A.O. Muliar, D.О. 2023-11-23T11:07:54Z 2023-11-23T11:07:54Z 2020 The efficiency assessment of the state system of nuclear safety control of NSC-SO / R.L. Godun, A.O. Doroshenko, D.О. Muliar // Problems of atomic science and tecnology. — 2020. — № 2. — С. 71-80. — Бібліогр.: 24 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/194366 621.039 According to the results of a comprehensive analysis, it was found that the nuclear safety monitoring system (NSMS) does not fully comply with the requirements put forward to it. By assessing the sufficiency of the detection points of this monitoring system, it was found that there is no monitoring at the cluster of nuclear fissile materials (NFM) in the central hall and at the "northern" cluster in 305/2 rooms. The effectiveness of monitoring the "southern" cluster of NFM in the room. 305/2 is insufficient and does not comply with the standards regulated by the rules of nuclear safety. Also, a number of other requirements to the NSMS (as the emergency alarm systems of the spent nuclear waste storage facility) are not fulfilled. It is proposed to re-arrange the measuring channels (MC) of the system, decommission excess (non-informative) MC and use their equipment to organize new effective monitoring points; to upgrade the software and arrange individual ground of the system to reduce the influence of high-frequency interference. За результатами комплексного аналізу встановлено, що система контролю ядерної безпеки (СКЯБ) у повному обсязі відповідає висунутим до неї вимогам. За оцінкою достатності точок детектування цієї регламентної системи встановлено, що відсутній моніторинг скупчень ядерно-небезпечних матеріалів, що діляться (ЯНДМ), у центральному залі і «північного» скупчення ЯНДМ в приміщенні 305/2. Ефективність моніторингу «південного» скупчення ЯНДМ у приміщенні 305/2 недостатня і не відповідає нормам, що регламентуються «Правилами ядерної безпеки» (ПЯБ). Також не виконується ряд інших вимог до СКЯБ як системи аварійної сигналізації сховища відпрацьованих ядерних відходів. Пропонується виконати перекомпонування вимірювальних каналів (ВК) системи, вивести з експлуатації надлишкові (неінформативні) ВК і використовувати їх обладнання для організації нових ефективних точок моніторингу; провести модернізацію програмного забезпечення та організувати індивідуальне заземлення системи, щоб знизити вплив високочастотних наведень і перешкод. По результатам комплексного анализа установлено, что система контроля ядерной безопасности (СКЯБ) не полностью соответствует выдвигаемым к ней требованиям. По оценке достаточности точек детектирования этой регламентной системы установлено, что отсутствует мониторинг скоплений ядерноопасных делящихся материалов (ЯОДМ) в центральном зале и «северного» скопления ЯОДМ в помещении 305/2. Эффективность мониторинга «южного» скопления ЯОДМ в помещении 305/2 недостаточна и не соответствует нормам, регламентируемым «Правилами ядерной безопасности» (ПБЯ). Также не выполняется ряд других требований к СКЯБ как системы аварийной сигнализации хранилища отработанных ядерных отходов. Предлагается выполнить перекомпоновку измерительных каналов (ИК) системы, вывести из эксплуатации избыточные (неинформативные) ИК и использовать их оборудования для организации новых эффективных точек мониторинга; произвести модернизацию программного обеспечения и организовать индивидуальное заземление системы, чтобы снизить влияние высокочастотных наводок и помех. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Problems of modern nuclear power engineering The efficiency assessment of the state system of nuclear safety control of NSC-SO Оцінка ефективності регламентної системи контролю ядерної безпеки комплексу НБК-ОУ Оценка эффективности регламентной системы контроля ядерной безопасности комплекса НБК-ОУ Article published earlier |
| spellingShingle | The efficiency assessment of the state system of nuclear safety control of NSC-SO Godun, R.L. Doroshenko, A.O. Muliar, D.О. Problems of modern nuclear power engineering |
| title | The efficiency assessment of the state system of nuclear safety control of NSC-SO |
| title_alt | Оцінка ефективності регламентної системи контролю ядерної безпеки комплексу НБК-ОУ Оценка эффективности регламентной системы контроля ядерной безопасности комплекса НБК-ОУ |
| title_full | The efficiency assessment of the state system of nuclear safety control of NSC-SO |
| title_fullStr | The efficiency assessment of the state system of nuclear safety control of NSC-SO |
| title_full_unstemmed | The efficiency assessment of the state system of nuclear safety control of NSC-SO |
| title_short | The efficiency assessment of the state system of nuclear safety control of NSC-SO |
| title_sort | efficiency assessment of the state system of nuclear safety control of nsc-so |
| topic | Problems of modern nuclear power engineering |
| topic_facet | Problems of modern nuclear power engineering |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/194366 |
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