Journal of Power and Energy Engineering, 2015, 3, 29-34
Published Online April 2015 in SciRes. http://www.scirp.org/journal/jpee
How to cite this paper: Bessonov, A.A., Kulyukhin, S.A., Konovalova, N.A., Mizina, L. V. and Rumer, I.A. (2015) Granular Sor-
bents for Passive Environment Protection System during Severe Accidents with Total Loss of Power Supply at NPPs. Journal
of Power and Energy Engineering, 3, 29-34. http://dx.doi.org/10.4236/jpee.2015.34005
Granular Sorbents for Passive Environment
Protection System during Severe Accidents
with Total Loss of Power Supply at NPPs
Alexey A. Bessonov, Sergey A. Kulyukhin, Natalya A. Konovalova, Lubov V. Mizina,
Igor A. Rumer
Frumki n’s Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, Russia
Received N ovemb er 2014
Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences has developed
some novel sorbents designed for the filter units of the passive filtration system for radioactive
discharge from the intercontainment space during heavy accidents with a complete loss of elec-
tricity supply at nuclear power plants. These are granulated sorbents based on large-pore silica
gel containing nanometric particles of Ag or Ag-Ni compounds (trademark Fizkhimin). The sor-
bents allow to remove various radioactive iodine species (inorganic ones and methyl iodide) from
a steam-gas phase with at least 104 decontamination factor. The high sorption properties of Fizk-
himin sorbent with Ag particles were confirmed during tests at a test facility of the TUV Sudwest
company (Karlsruhe, Germany). This passive filtration system is installed at the 1st and 2nd units of
the Kudankulam nuclear power plant (India) and it is unique in the world practice.
Nuclear Power Plant, Sor bent, Radioactive Iodine
The problem of reliable environmental protection measures in the event of severe nuclear power plant accidents
appears to be an important factor restraining the development of nuclear energy. It is known that a hypothetic
severe accident accompanied by a partial or complete destruction of the reactor’s active zone, bring about the
formation of large quantities of gaseous products. This leads to an abrupt increase in pressure inside the con-
tainment and there is a risk of its destroying. Besides, due to leakage through non-airtight sectors of the con-
tainment the radioactive steam-air mixture may penetrate to the other areas of plants, such as the intercontain-
ment space, technical and service zones and than from these areas to the environment. For decreasing of the
pressure inside the containment, the some nuclear power plants are equipped with pressure release system. The
modern designs of new-generation nuclear power plants with two protective shells do not provide for pressure
release systems -. It is planned that during hypothetical severe accidents all radioactive products will be
A. A. Bessonov et al.
localized inside containment. But calculations, which was made for LOCA accidents at PWR NPP, show that
during accident during 122 h, pressure under the containment can rise up to 0.7 MPа, with the steam/air ratio
being 2.7 to 1. This time is enough for penetration of the radioactive steam-air mixture from containment into
the intercontainment area and then into the environment. To prevent radioactive contamination of the environ-
ment, modern designs are equipped with active venting filtering systems, which require regular electric power
supply. However, in accordance with the general requirements for safety systems, alongside active ventilation
systems for intercontainment space, nuclear power plants should include a passive ventilation system, which can
be used during hypothetical severe accident with a complete loss of power supply.
2. Results and Discussion
Based on the fundamental studies on localization of volatile fission products the new passive environment pro-
tection system during severe accidents at new generation NPPs is suggested -. The main purpose of de-
veloped passive filtration system is creation of a rarefaction in an intercontainment space due to the organized
removal of the radioactive steam-air mixture from an intercontainment space at full loss of all power sources.
Steam-air mixture containing radioactive aerosols and flying fission products removal from an intercontainment
space is passed through the special filtering module (Figure 1). Efficiency of cleaning of a radioactive steam-air
mixture is determined by filtration and sorption properties of used filtering elements. The following engineering
requirements to given filter under development were showed.
The flow rated speed of the filtered medium is not less than 400 m3/h (0.135 kg/s by dry air) at temperature
20˚C and pressure 0.1 MPa. At the specified rated speed pressure difference on the filtering module should not
exceed 20 Pa at 20˚C and 0.1 MPa (or 48 Pa at temperature 280˚C). The filtering module should provide filtra-
tion and sorption properties in a temperature range from 20˚C to 300˚C. Under these conditions, efficiency of
the decontamination of the steam-air environment with water vapor content up to about 30 vol.% should be not
less than 99.9% from molecular iodine (I2) and not less than 99.0% from organic compounds of iodine (CH3I).
At the same time during filtering module heating up to temperature 300˚C the level of radioactive iodine desorp-
tion should not exceed 0.1% from a total quantity of the compounds located in the module.
Fundamental studies on localization of molecular and organic forms of radioactive iodine from a steam-air
flow in operating conditions of passive filtering system allowed to select for this filtering module sorbents
“Fizk hi mi n”TM, including nanometric particles of Ag or Ag-Ni compounds.
The granulated sorbent “Fizk himin”TM represents silica impregnated by Ag or Ag-Ni and modified on tech-
nique of IPCE RAS (Figure 2 and Figure 3)  .
Fig ure 1. The layout of the passive filtering system for decontamination of intercontainment area (1-heat-exch anger
of the passive heat-removal syst e m, 2-intercontainment area, 3-pipe of the passive heat-removal s yst em, 4-deflect or,
5-coll ector of the passive heat-removal s yst em, 6-filtering unit, 7-piping, 8-valve with pneumatic drive ).
A. A. Bessonov et al.
Figure 2. The sorbent “Fizkhimin”TM based on Ag nanometric com-
pounds (Electronic microscope ЕМ-301 “Philips”).
Figure 3. The sorbent “Fizkhimin”TM based on Ag-Ni nanometric com-
pounds (Electronic microscope ЕМ-301 “Philips”).
The sorbent is manufactured in several types and represents granules of dark color with the sizes of particles
0.5 - 6.0 mm. The studies of sorbent properties have shown, that it is radiationally resistant at a doze 500 MRad
and does not initiate ignition of hydrogen. The basic physical and chemical characteristics of these sorbents are
presented in Table 1. As shown from Tab le 1, the given sorbents have high sorptive efficiency in relation to
molecular iodine and iodide methyl. At that it is necessary to note, that they do not lose the sorptive efficiency
up to temperature 300˚C and up to temperature 600˚C from them does not occur the desorption of radioactive
iodine in a gas phase (Table 2).
Taking into account novelty of development and an opportunity of the international application of passive fil-
tering system (the Russian project of the NPP WWER-1000 in India), expert international tests of efficiency of
A. A. Bessonov et al.
sorbents “Fizkhimin”TM on absorption of volatile radioactive iodine compounds at the stand of “ТUV Energie
und System Technic” (TUV ET) (Karlsruhe, Germany) have been carried out. Testing passed on localization
most difficult sorptive form of the radioactive iodine - methyl iodide. Test facility concluded the following basic
parts: a thermostatically controlled by hot air two-section tight chamber; a steam generator; a condenser; a col-
umn with a tested sorbent; columns with a control sorbents; rotameters; container with water; balance; peristaltic
pump; manometers; the compressor or preevacuation pump.
Experiments were carried out as follows. A columns with sorbent “Fizkhimin”TM and control sorbents, a
steam generator installed in a two-section tight chamber. Their heating was carried out with the help of heated
up air. Amount of water in a steam-air mixture created as follows. Strictly given amount of water submitted to a
steam generator with help of peristaltic pump. Simultaneously the certain amount of air submitted to a steam
generator. In a steam generator water evaporated, mixed up with air and moved into superheater of a steam-air
mixture. During passing of a steam-air mixture through superheater there is occured a thermostating of a gas
phase. The column containing sorbent “Fizkhi mi n”TM preliminary heat up and blow a steam-air mixture of the
certain content within 2 h. Simultaneously the heating of a steam generator, columns with control sorbents, and
also superheater of steam-air mixture carried out. After the ending of preliminary blowing and thermostating of
facility a gaseous CH3131I from special vessel began to include on a facility. The steam-air mixture mixed with
CH3131I and than directed on a column with a tested sorbent within 30 min. After the ending of including of
CH3131I a thermostating steam-air mixture blowed through a column during 16 - 18 h. After a column with a
sorbent “Fizkhimin”TM the radioactive steam-air mixture goes on a column with control sorbents and than into a
condenser. In a condenser there is occured the condensation of the basic amounts of water. After the ending of
test a distribution of 131I in a column with sorbent “Fizkhimin”TM and columns with control sorbents was inves-
tigated. On the basis of the data of the 131I distribution the decontamination factor DF of cleaning of a steam-air
mixture from CH3131I was calculated. Results of tests (Table 3) have shown, that sorbents have very high sorp-
tive efficiency relative to most difficult localize form-to methyl iodide, at various experimental parameters.
Table 1. Main properties of the granular sorbent “Fizkhmin”TM.
Particle size, mm 0.25 ÷ 6.0
Metal concentration in the sorbent, wt.% 3 ÷ 10
Heat capacity, J∙kg−1∙К−1 ≥795.5
Heat conductivity, W∙m−1∙К−1 ≥1.4
P, kg/m3 550 ± 100
Unconfined space, % 60 ÷ 80
Specific surface, m2/g 310 ± 20
Average pore radius, Å 55 ± 10
Total pore volume, сm3/g 1.4 ± 0.2
Sorptive capacity, g per 1 kg of sorbent
6 ÷ 25
15 ÷ 60
Sorptive efficiency*, %
Decontamination factor (DF)
Notes: P-s the amount of the sorbent per 1 cm3 (“dry density”). *Sorptive efficiency was determined under follow conditions: Tsteam-air flow = 35˚C ÷
280˚C; υgas flow = 2 ÷ 60 cm/s; steam content in gas flow-3÷ 80 vol.%; τ (“gas flow-sorbent”) = 0.3 ÷ 6.0 s; Tsorbent = 35˚C ÷ 280˚C; msorbent = 50 ÷ 100
g; hcolumn = 20 ÷ 50 cm; Scolumn = 4.5 ÷ 7.0 cm2 ; m(CH3I) = 5 ÷ 200 mg; m(I2) = 5 ÷ 200 mg.
A. A. Bessonov et al.
Table 2. Technical parameters of effective work of the sorbents “Fizkhimin”TM.
Temperature of the filtered medium, ˚C 35
Relative humidity of a filtered steam-air stream, % 1.5
Linear speed of a stream of the filtered medium, cm/s 1.6
Concentration of vola tile radioactive iodine compound s, g/m3 0.0003
Quantity of radioactive iodine compounds on 1 m2
of filter cross- secti on, g 0.11
Temperature of effective sorbent work, ˚C 30
Temperature of the radioa ctive iodine desorption beginning, ˚C
Pressure difference on the 250-mm layer of the sorbent at temperature 20˚C and linear speed of dry air flow
1.6 cm/s, Pa 6
Table 3. Sorption of the CH3131I on the granulated sorbent “Fizkhmin”TM based on Ag nanometric compounds from a steam-
Type of sorbent
The size of particles,
mm h, cm Tsorb,
% υ, cm/s τ, sec A degree of absorption on a
-"- 0.25 - 2.0
3.0 - 6.0
Notes: h-height of a layer of a sorbent in a column (the area of a column of 4.9 cm2), Tsorb-temperature of a sorbent; Tgas-temperature of a steam-air
stream; υ-linear speed of a steam-air stream in a column; τ-time of contact “a sorbent-a steam-air flow” (for all layer of a sorbent); RH-relative hu-
midity of a steam-air stream.
In conclusion, it is necessary to note, that the granulated sorbents “Fizkhmin”TM have very high sorptive effi-
ciency in a wide range of experimental parameters. Therefore, they can efficiently be used for localization of
volatile radioactive iodine compounds not only in passive filtering system, but also in other filtering devices, for
example in the filters of emergency pressure release from containment operational NPPs during severe acci-
Work is supported by Council about grants of the President of the Russian Federation for the state support of
leading scientific schools of the Russian Federation (grant SS-5418.2014.3).
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