ORIG. RUSSIAN:- THE APBYC ORGANIC COOLED AND MODERATED NUCLEAR POWER STATION

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP88-00904R000100100010-9
• Release Decision: RIPPUB
• Original Classification: U
• Document Page Count: 20
• Document Creation Date: December 22, 2016
• Document Release Date: August 12, 2009
• Sequence Number: 10
• Publication Date: May 1, 1964
• Content Type: STUDY

 Third United Nations
International Conference
on the Peaceful Uses
of Atomic Energy
Confidential until official release during Conference
A/CONF.28/P/307
USSR
May 1964
original: RUSSIAN
THE ATBYC ORGANIC COOLED AND MODERATED
NUCLEAR POWER STATION
K. K. Polushkin, I. Ya. Enelyanov, P. A. Delens, N. Vo Zvonov,
U.N.Aleksenko, I. LGrozdov, S. P.Kuznetsov, A.P. Sirotkin,
U.I.Tokarev, K.P. Lawrovsky, A.M.Brodsky, A.R.Belov,
E. V. Borisyuk, V. M. Gryazev, V. D. Tetyukov, D.N. Popov,
U. I.Koryakin, A. G. Filippov, K. V. Petrochuk, V. D. Khoro-
shavin, N.P.Savinov, M.N.Meshcheryakov, V.I.Pushkarev,
V.A. Suroyegin, P. A. Gavrilov, L. N. Po dlazov, I.N. Rogozhkin
The concept of utilization of small-sized nuclear power
plants appeared in connection with the necessity of supplying
electric power to the USSR remote difficult-to-reach areas, where
the construction of conventional electric plants was not justified
from the economic view point mainly due to high costs of fuel
transport or its output on the spot. Technical and economic calcu-
lations show that for a number of such areas small-sized nuclear
engineering may be advantageous even today. As it is known, -.oat
of electric nuclear power is characterized by a relatively high
capital. cost, notably for small nuclear plants.
Reduction in capital cost may be achieved by using organic
coolants, which allow to utilize cheap structural materials,
serial equipment and instruments, and due to the primary circuit
light biological shield or even absence of it.
But up to date a wide use of organic coolants in nuclear
power engineering is restricted due to several undesirable effects
connected with radiolytic processes in organic compounds. First
of all, these are: build-up of high boilers (B.K) resulted from
radiation-induced polymerization which finally might give rise to
formation of insoluble compounds deposited as films on fuel ele-
ment surfaces and to deterioration of coolant thermal and physical
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properties. As the operating experience with the OMRE reactor in
the USA showed, the most simple system of coolant purification
con3isting in distillation and rectification although makes it
po,a3ible to maintain high boilers concentration at a given level,
but it does not guarantee against deposits formation at the fuel
element surface. In addition, using this purification method, it
is necessary to add fresh coolant make-up and dispose high boi-
lers released from the circuit. This fact considerably limits
the number of organic fluids which can be used due to high
requirements for their radiation stability.
In this connection, in solving the problem of using organic
coolants in the nuclear power plant every effort has been made
to find the possibility of regeneration of radiolysis high boi-
l 's without their removal from the circuit. This makes it possi-
le to use a number of standard materials at low cost, and with
;omparatively low thermal and radiation stability. As a result,
a regeneration system was developed based on catalytic hydrocra-
cking. As preliminary loop tests showed, the parameters having
been chosen correctly, this process ensured hydrogenation of
unsaturated products of radiation dehydrogenation and selective
destruction of radiolysis high boilers. This purification method
enabled hydrostabilized gas oil obtained on the basis of direct
distillated gas oil fraction of naphtene - aromatic base petro-
leum to be used as coolant for the first nuclear power plant.
Alongside with the well-known advantages of organic coolants
there are some more:
1. Low freezing point (-40?C, -70?C), thus, the circuit warming-
up is not required.
2. Low cost. Gas oil characteristics are given in Table II.
The first nuclear power station of the APBYC type (Arctic
modular reactor plant) has been built at the Nuclear Reactor
Research Institute (Melekess, Ylyanovsk district). The APE.YC
main parameters are given in Table I.
...ha nuclear power plant reactor with organic coolant was
put into p~ of operation on June 23, 1963, after thermal and
physical. t 6ts the plant went into operation on August 11, 1963?
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Table I.
The APEYC Main Parameters
Reactor output
Turbogenerator output
Pressure in the primary circuit pressurizer
5000 kw
750 kw
6 atm
Coolant temperature:
at reactor inlet
230?C
at reactor outlet
243?C
Coolant flow rate of the primary circuit
600 t/hr
Saturated steam temperature in steam Generator
223?C
Table II.
Hydrostabilized gas oil characteristics
Specific we4:ght at 200C
0.8558 g/c.c
Iodine number, not greater than 1
Sulfurizing total
30% (by weight)
Boiling initiation
2120C
Boiling termination
300?C
Carbon content
86.89%
Hydrogen content
1.3.11%
H: C ratio
1.8
Sodium content
Sulfur content
2.105%
(by weight)
3.10-3 %
Vapour pressure at 350?C
(by weight)
4.85 atm
Chemical compound:
paraffin
30.12%
aromatic
30,03%
napht ene
3p9.85%
Nuclear Power Station General Diagram
The plant design has been chosen to be of s two E~.~`CL: To
(Fig. 1) .
The coolant is circulated i1n. the primary circuit by
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electric pumps over two parallel circulation passes. Each pump
capacity is 430 crr3/hr at the head of 43 m liquid gauge. Electric
motor power is 50 kw. The coolant is fed from the reactor to the
steam generators with free surface evaporation, their advantages
are as follows: simplicity, reliability and less severe require-
ments for the feed water. The heat is transferred to the second
circuit water in the generators by the coolant, then the coolant
comes to pressurizers, which serve degassers as well. Gas is
removed from the coolant surface and in special degassing devices,
to which 10% of the coolant total flow rate is fed. Coarse gauze
filters are also installed in the pressurizer. The coolant is
passed from the pressurizers by circulation pumps and it is
returned to the reactor.
In the primary circuit pressure is maintained due to gases
which are emanated during coolant radiolysis and at the nuclear
power' plant start-up it is rendered by nitrogen.
Excess gas is rejected to the atmosphere by the pressure
regulator.
In the reactor at the initial period residual heat is remo-
ved by two turbine pumps in case of de-energizing the primary
circuit circulation pumps at the expense of steam accumulated in
steam generators, this steam operates turbine pumps for 90 min.
and coolant flow rate is 96 t/hr. Then the heat is removed by
natural circulation.
The primary circuit coolant is purified by metal ceramic
filters installed in bypasses of the circulation pumps. These
filters hold suspended particles of greater than 1.5-3 mu in size
ans they do not let the iron concentration in the coolant be more
than 0.3 mg/1. The flow rate through these filters is about 10%
of the coolant total flow rate.
The primary circuit filling-up and its making-up are obtai-
ned by a pump from a 20 m3 dump tank. The coolant is passed to
dump or drain tank depending on its contamination. Gas oil low-
boilers fractions (boiling point up to 120?) forming during the
coolant decomposition are condensated in the receiver, then
they are periodically drained.
The coolant for regeneration is taken from the primary
circuit line and regenerated gas oil is passed to the dump tank,
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The scheme and principal features of regeneration system are
described below.
The second circuit is a part of a conventional condensation
steam turbine power plant. In case of an abrupt drop of turboge-
nerator loading a throttling-welting device is provided in the
circuit for direct dumping the excess steam into the conder,cer.
The latter is water cooled. Pig.3.
Nuclear Power Station layout and its Equipment
The AP.BYC plant consists of separate fully mounted factory-
assisted and tested units. It comprises 19 units eawckt neighing not
greater than 20 tons. The plant total weight together the reactor
shield is 365 tons. The unit weights and size make it possible to
transport them to the building site by water or by land. The
plant may be 7ncunted on-site in two or three months.
The APEYC occupies a 12.36 x 28.5 m building and 6.36 m
high. An electrolizer and drained devices are located outside the
building.
The equipment layout in the buiding is shown in Fig.2.
At the plant start-up the electric equipment is supplied
from a 1;5 kw Diesel-generator.
The primary circuit warming-up and its emergency cooling are
accomplished under natural circulation conditions owing to diffe
rent levels of the reactor and steam generator layout.
The plant is equipped with a container, guider and special
tools for reactor refuelling and spent-fuel assembly storage,
control and safety system thimbles with rods and manual regula-
tors, The reactor is refuelled with a 12 tons special bridge-
crane.
The total personnel is 17.
The equipment, fittings and pipes of the primary circuit are
made of carbon steel.
Aerial oil pumps and standard oil equipment with increased
requirements for the quality of inner surface clean-up are used.
Non-standard equipment is made of Itsteel 20" structural steel,
the
the casings and bottom, dimentions of
reacto-rr steam generatcre
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and pressurizers are unified. Pipes were argon-arc welded in the
mixture with carbon dioxide.
The estimation of primary circuit coolant activity showed
that it should be not greater than 1.5 . 10-4curie/l maximum
considering possible fission product release in case of fuel ele-
ment burst defined at artificial damage of a fuel element can
during loop tests. This made it possible not to use the primary
circuit shield, except only the reactor shield w'aich may be built
from conventional shielding materials (concrete, graphite, poly-
ethilene and iron).
Taking into consideration the plant equipment layout and
its operating conditions, the dose rate was estimated to be
0.5 Jt/rem/sec in the serviced rooms and in partially serviced
rooms to be 1.7 rem/day, this meets personnel radiation safety
requirements.
During test operation at reactor 100% power the dose rate
of the pressurizer was 40jrem/sec, and that for pipes was 3 to
4 J61rem/sec. Activity of gases emanated from the coolant radio-
lytic decomposition was 10r12curie/1. The total gas activity of
the plant was about 7.2 . 10-8curie/day.
Reactor
enriched to 36% is 22.5 kg.
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The reactor is a welded cylinder, 4365 mm high, 1340 mm in
diameter, 20 mm wall thick, at the upper end of which there is a
flange with supporting legs and 8 nozzles 150 mm in diameter for
the coolant inlet (fours upper) and outlet (four, lower). To
reduce the vessel irradiation lateral and lower thermal shields
are provided.
There is an inner vessel in the reactor which forms the
coolant flow and at the same time serves as the core supporting
structure. Uniform distribution before the core is achieved with
the help of two perforated plates.
Uranium-aluminium alloy UA14+A1 has been used as a fuel
which gave a minimum fission product release into the circuit in
case of fuel element can burst. Total loading of uranium-235
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Dynamic Characteristics Studies and Plant
Regulation
2 years. The reactor control system includes cylindrical rods,
moving in the reactor core.
Two boron steel rods are designed for automatic control
(rods AP).
30 boron steel rods compensate the temperature and poisoning
effects (rods KC). These rods account for about 12% reactivity.
In case of accidental conditions of the first kinds (that is
coolant flow rate failure in the primary circuit or increase in
the runaway rate) all these rods fall into the core.
Two rods KC connected in pairs are of safety system (A3) of
the second kind. The safety system signals include the signals
of design power-level overshoot, power supply failure and other
technological signals.
37 boron carbide rods are designed for compensating the
burn-up effect. These are used as two position rods and account
for about 18% reactivity.
Reactor control, regulation and power eafetyare provided by
measuring the neutron flux with compensated ionization chambers.
The latter are placed in special hermetically sealed hangers loca-
ted in the space between the chimney and reactor weasel.
The hangers occupy 12 channels, 5 channels with lead shrouds
are designed for start-up hangers. Magnetic amplifiers are chiefly
used in control and safety system which ensure stable operation
at low remperatures and are easily transported over long distan-
ces.
Reactor is controlled by one automatic regulator, the second
one being stand-by, The design power level stability is kept
within +1%.
The reactor automatic start-up is provided by an instrument
which brings the reactor from (10-4 - 10-5 )%N nominal to (1-10)76N
nominal with preset period. Within this range this automatic
start-up instrument ensures safety when the power rate increases;
The plant dynamic characteristics have been studied on an el-
ectronic model and then directly on the ApBYC plant.
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As a result of these investigations it was found that all
the proi,esses are relatively slow both under operating and
emergency conditions, this being a special feature of the plant.
All these transients are slow, this is attributed to rela-
tively large amount of the coolant in the primary circu.-St and
boiling water in the steam generators and 'avourable from the
view point of thermal conditions of the fuel elements and the
primary circuit structures.
The temperature self-regulation research of the plant has
shown that its sufficient stability ensures its normal operation
under design conditions without an automatic regulator of the
reactor neutronic power. The maximum permissible sudden increase
in reactivity of the system at an acceptable deviation of tech-
nological parameters, being about + 0,1 B and - 0.3 13.
Under self-regulation conditions the plant automatic transi-
tion from one power level to another is possible with the automa-
tic regulator off, when the coolant temperature level and steam
pressure being changed in the proper way. (Fig.7 ).
Investigations of the coolant flowrate perturbations showed
that the flowrate variations with an amplitude t'p to 105 and
frequency from 0.01 cps and up proved to be permissible. No
changes in parameters were observed at a .frequency greater than
0.3 cps.
During the plant operation under nominal conditions an in-
stantaneous rejection of 260 kw leads to the steam pressure rift.
in the second circuit about by 3 atm; at subsequent loading of
260 kw the system parameteraacquire again their original values.
AB a result of the emergency shut-down cooing of the pri-
mary circuit when the circulation pumps fail it was found that
the temperature of the fuel element surface does not exceed the
permissible value if the emergency turbopumps begin to operate
not later than in 3 seconds. The experience gained directly at
the plant showed this time being equal to 0.2 sec.
The normal operation time of the turbogenerator for its cwn
purposes after the scram shut-down is equal to 18 sec.
The results of studies on an electronic simulator were ccr-
firmed during the plant testing. Change in plant parameters v:- t?
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increase in electric load is shown in Fig.4.
Conservation and the primary circuit
purification
The power plant, where the primary circuit is made of carbon
steels and without a biological shield, should meet the main
requirement, that is organic coolant purity. For this purpose the
equipment and piping of the primary circuit were subjected to
tho.rough chemical or mechanical treatment to remove contamination
ar. t corrosion products with subsequent conservation with a vola-
tile Inhibitor (50% water solution of monoethanolamine) and they
were sealed for transportation and mounting.
After mounting and. dried air pressing the circuit was filled
with a petroleum fuel "]A" type (similar in composition to gag
oil) containing i mg of iron per liter, the circuit has been
subjected to Ylpt washing. When washing the temperature was kept
close to operating one. To achieve maximum effect the circuit
was washed in three stages. After each stage the fuel was poured
out and replaced with a new portion. The washing process was
controlled according to iron content in the fuel. The conserva-
tion and purification technology described made it possih'.. :-j
start the plant with 0.2 - 0.3 mg of iron per liter.
Coolant Regeneration
To remove polymers orzd unsaturated compounds from the APLYC
primary eircui.t a special system of organic coolant regeneration
was developed by a continuous partial removing it to a hydrogena-
ted reactor. in this reactor with alumocobalto-molybdenum cata-
lyst unsaturated unstable compounds are hydrogenated and polymers
are destructed under hydrogen pressure, a total of 80 per cent of
compounds being formed, their physical and chemical properties
are similar to original ones. The rest of 20 per cent compounds
are light products and coke. During such a regenerating process
the coolant is additionally purified from metal and sulfur tra-
ces. It should be noted that in this case the hydrocracking prow
'mess is more simple due to character of linking in chemical..
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radiation polymers. Tne regeneration conditions are chosen in
such a way as not to allow aromatic compounds to be hydrogena-
ted.
The results of investigations showed that when applying
hydrogenated regeneration to coolants prepared from gas oil frac-
tions of petroleum the optimal parameters were as follows:
Hydrogen pressure . . . . . . . . . . . . . . . 40-60 atm
Temperature in reactor . . . . . . . . . . . . 350-380?C
Volumetric velocity . . . . . . . . . . . . . . 0.5 hr-1
Raw material-hydrogen molar ratio . . . . . . . 1:5 to 1:10
The general arrangement of the regeneration system is shown
in Fig.1. The coolant comes from the primary circuit (200-250
liter/hour) to the regeneration system gas oil pump. Then the
gas oil at a pressure of 45-b0 atm is mixed with an inflow of
circulating hydrogen. The latter is obtained by water electroly-
sis in an electrolyzer from which it is transported to the system
by a displacement compressor of the regeneration system. The gas
oil and hydrogen mixture is heated in the regenerative heat ex-
changer, and then it is heated up to the working temperature in
an electric furnace. After that the gas oil and hydrogen mixture
is fed to the reactor filled with catalyst. The hydrogen and rege-
nerated gas oil mixture coming from the reactor transfers its heat
in the heat exchanger, and is finally cooled down to 30-50?C in
the cooler. Then the mixture is separated in a gas separator from
which the gas oil comes through cermet and felt filters to the
p :J.,mary circuit feed tanks, and hydrogen flows to the circulating
compressor. Owing to formation of destru';tion gas products (meth-
ane), errall amounts of the circulating gas are continuously reje-
cted to an exhaust stack, Hydrogen total flowrate is found to be
0.45 kg/hr, hydrogen in the amount of 0.36 kg/hr directly takes
part in the reaction.
Radiation-induced Chemical Changes of Coolant
In general good agreement was obtained between the radiation-
induced chemical characteristics of the hydrogenated gas oil and
the results of preliminary experiments and loop tests carried
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out on APEYC. Fig.7 shows the temperature relation of viscosity
for original and irradiated gas oil of the APBYC primary circuit
containing 9.03% high boiling products of radiolysis (BK).Changes
in density, viscosity, iodine number and content of radiolysis
high-boiling products with growth of integral dose are shown in
fig.6 and 7 during operation without regenerating unit. Absorp-
tion curve of radiation energy p *r 1 g gas oil is shown in Fig-7.
On the basis of the results obtained an initial value of
high boilers formation has been calculated,that is, about 2 mole-
cules/100 ev. In prolonged operation this value reduces to about
0.5 molecules/100 ev.
The composition of gas formed as a result of radiolysis has
been tabulated (Table III). Coolant flowrate to fill up the losses
due to radiolytic decomposition at 100%o power operation amounts
to 20-30t/year.
Table III. Gas Composition Formed During radiolysis
onent s
Com
J ? V V
ua
p
weight t
volume
Hydrogen
26.670
83.077
Methane
24.191
9.415
Ethane-ethylene
13.634
2.829
Propane
11.079
3.566
Propylene
9.060
1.343
N -Butane
5.496
0.590
Acetylene
0.548
0.132
Butane
2.081
0.224
Allene
0.386
0.061
B, i + d - Butylenes
6.219
0.692
B - Butylene + Divinyl
0.636
0.071
Conclusion
Construction and pilot operation of the APEYC powe-? plant
showed the possibility of building nuclear power plants with
organic moderated reactor in remotely sited areas of the USSR.
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The uperutiing experience confirmed the correctness of cal-
culations and principal considerations underlying the design, the
possibility of making the primary circuit equipment and pipes
of carbon steel without shielding and the possibility of using
serial petroleum equipment and standard fittings considering the
requirements for a power plant. This nuclear power plant is
rather stable, simple and reliable in operation under various
conditions.
There is a possibility of further improving technical-eco-
nomic characteristics of the plant of this type by improving
parameters (use more heat resistant regenerated coolant) and
modifying the plant on the basis of operating experience accu-
mulated.
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35 a a
oo( 1