ORIG. RUSSIAN: OPERATIONAL EXPERIENCE OF THE FIRST ATOMIC POWER STATION AS AN EXPERIMENTAL SET-UP

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP88-00904R000100100016-3
• Release Decision: RIPPUB
• Original Classification: U
• Document Page Count: 17
• Document Creation Date: December 22, 2016
• Document Release Date: August 12, 2009
• Sequence Number: 16
• Publication Date: May 1, 1964
• Content Type: STUDY

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International Conference
on the Peaceful Uses
tt ~ of Atomic Energy
Confidential until official release during Conference
A/CONr. 28/P/314
USSR
May 1964
Original: RUSSIAN
JA 1 /1c e i
OPERATIONAL EXPERIENCE OF TILE FIRST
ATOMIC POWER STATION AS AN EXPERIMENTAL
SET -- UP
C.N.Ushakov, L.A.Kochetkov, V:C.Konochkin, V.S.Severjanov, V.Y.Kozlov, O.A.Sudnitsin, N.T.Belin-
skaja, P.N.Slusarev, V.A.h'anov
A great number of special experiments had to be when designing new nuclear power plants
and in the first place the Kurchatov Atomic Power Station. These experiments included: a study
of water boiling conditions and steam superheating ones in tubular fuel elements; a study of
the formation, accumulation and release of radiolytic 02 and 1.12; a study of the water condi-
tions; a-study of the radioactive deposits from superheated steam; a study of the behaviour
of graphite and steel in the pile.
However, the major problem in designing new atomic power plants was the experimental
study of fuel elements. In order to solve all these problems it was necessary to build a number
of experimental loops in the pile of the First Atomic Power Station.
?1. EXPERIMENTAL LOOPS
At present, tests are being conducted on the following experimental loops in the pile:
1. two-circuit steam-superheat loop;
2. natural-circulation water loop;
3. water unit for chemical experiments;
4. high-pressure -water unit;
5. high-melting organic coolant loop;
6. low-melting organic coolant loop.
Following is a brief description of these-loops.
TWO-CIRCUIT STEAM-SUPERHEAT LOOP
A study was made of the transient conditions on the loop, a study of the water conditions
in radioactive coolant circuit, including problems of the formation, accumulation and release
of radiolytic 02 and H2 and problems of deposits on fuel elements and turbine vanes.
A study was also made hereof the behaviour of steel in contact with the coolant in its
operating parameters. But the basic problems studied on that loop were testing fuel elements
and certain structure elements of the fuel channels for the - Kurchatov Atomic Power Station.
~~k Third United Nations
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A schematic diagram of a two circuit water loop with nuclear steam-superheating is shown
in Fig. 1. The pipes and equipment are made of stainless steel. The loop has two radioactive
circuits; its diagram is similar to the Kurchatov Atomic Power Station.
The coolant circulation in the primary circuit may be followed on the diagram. From the
pressure pump the water is fed into the distributing collector after which it flows along separate
evaporating channels. Water consumption is regulated with valves mounted on the inlets of
the-pipe channels. After the evaporating channels, the water or the steam-and-water mixture
flows through separate circulation circuits and gathers in the general header then directed
along a pipe into the evaporator. Then if need be, the water completely or partially goes
through an additional cooler.
In the evaporator the heat of the primary circuit is wholly or partially transferred to the
water of the secondary circuit. The secondary circuit is designed as an open circuit of circula-
tion and makes it possible to conduct simultaneous tests of three steam superheating channels.
With the aid of a plunger feed pump, the water of the secondary circuit is fed to the preheater
(4) - regenerative heat exchanger where it is heated by cooling the superheated steam. Then,
heated to the saturation temperature, the water is directed to the evaporator. Here it completely
evaporates, due to the heat received from the primary circuit. The humid steam is further dried
in the linear separator (2) and then in the header it is distributed along separate loops of the
steam superheating channels. Each loop of the superheating channels has regulating valves
and additional individual separators to remove moisture from the steam, which was formed in
the supply loops, because of the decrease in pressure and heat lost through the walls of the
pipes.
Superheated steam after the superheating channels is directed to the make-up water heater
and may also be partially selected for experimental units (for example, on a stand of a running
part of a turbine). The steam is finally condensed and cooled in the condenser and auxiliary
cooler (5), and then dumped into the water tank (6) through the throttling device.
Any deviations detrimental to the operation of the unit (increase oi- decrease of pressure
in the primary circuit, temperature increase in the fuel elements, increase of temperature in
the superheated steam, increase or drop in water and steam consumption, deviations in the
circulating pump) automatically stops the reactor by the safety trip system.
NATURAL - CIRCULATION WATER LOOP
Mention must be made of two peculiarities of the water loop with natural-circulation of cool-
ants which make it possible to consider it as a highly prospective unit, to conduct ampoule
tests of new fuel element compositions. Firstly, is its simple maintenance and reliability,
and secondly, is its small dimensions which makes it possible to liquidate quickly the con-
sequences of an accident caused by the destruction of the fuel elements.
The loop is assembled according to the double-circuit design (Fig. 2). The primary circuit
is closed; it includes experimental ports (1), heat exchanger (2), compensator (3), inlet
and outlet headers (4), sampling cooler (5). ~
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WATER - L00P FOIL CHEMICAL. EXPERIMPNTS
This loop is designed to study water chemistry, diffusion of nitrogen from volume com-
pensators, corrosion of low-alloy steels, protection of these steels to cut down the rate of
corrosion, testing filters to withdraw corrosion products from the circuit etc. A circuit diagram
of the loop is shown in Fig. 3.
A regenerative heat exchanger (4) and an experimental port (2) are used to heat the cool-
ants. Heat removal takes place in the heat exchanger (5) where the heat is conveyed to the
water of the secondary circuit. There is a tank (6) with attachments to prepare the necessary
solutions, ion-exchange filters (7) and sampling equipment to conduct chemical experiments
in the circuit.
The thermo-mechanical equipment makes it possible to conduct experiments in tempera-
tures of 500 to 300?C. The basic constructive peculiarity of this loop is that it has two paral-
lel circuits-: one of which is stainless, and the other - made of carbon steel. Such a system
was used to get a more objective comparison of the speed of corrosion of various steels under
similar conditions.
HIGH - PRESSURE WATER LOOP
This loop was built to check the various designs of fuel elements, to high burn-up fuel
compositions, and to make a study of materials. Heat removal from the experimental ports was
done-by the water of the primary circuit, which was circulated by a glandless pump. The water
of the primary circuit is cooled by the water of the secondary circuit in the heat exchanger,
.and the final heat removal, - by the circulating water from the general system. When conduct-
ing experiments, it is possible to change the water temperature at the channel inlets from
100 to 200?C. The water temperature is regulated at the channel inlets with a bypass line and
valve on the primary circuit in the master heat exchanger. There is a probability of fission -
fragment activity in the circuit if experiments are conducted in this loop. That is why all the
basic equipment of the primary circuit is placed into a specially protected box: Counters are
mounted on the channel exit pipes to control the dose capacity y-radiation of the coolant leav-
ing the reactor channel.
LOOPS FOR STUDYING ORGANIC LIQUIDS
It was necessary to build these loops in order to study the radiation resistance of organic
coolants, their activation, the deposits of polymerization products on heating surfaces etc.
It was also necessary to obtain some experience,in operating a unit with organic coolants,
to study the corrosion resistance of construction material in an organic medium under condi-
tions of neutron radiation and to study the'thermo-physical properties of the coolant during
loop operation.
HIGH - MELTING ORGANIC COOLANT LOOP
The-unit consists of the basic circulating circuit and a number of auxiliary systems. The
coolant of the basic circuit, after passing through the hot channel where it undergoes heating
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and radiation, enters the heat exchanger and is cooled there with process water. From the heat
exchanger, the coolant enters an expansion tank and from the tank it is pumped again to the
channel. The unit has a charging tank where solid matter is melted down with subsequent re-
pressuring into the expansion tank. Commercial nitrogen is used in the expansion tank and in
the auxiliary units to create a blanket of inert gas.
An electric heating system is mounted on the pipes because the loop is designed to
operate with organic matter having a melting point higher than the room temperature. The
heat exchangers of the master circuit and the sampling coolers are heated with hot water.
LOW -- MELTING ORGANIC COOLANT LOOP
The master circulating circuit loop includes: hot channel with fuel elements, circulating
pumps, master heat exchanger, expansion deaerating tank, mechanical purification filter of
the coolant, fittings and pipes.
There is a by-pass with a regulating valve in the main heat exchanger to regulate the
temperature in the circuit.
The operating pressure is fixed in the circuit by feeding inert gas (nitrogen) into the gas
volume of the expansion tank. The gas volume of the expansion tank is a receiver and collector
of gases emitted from the coolant. The basic mass of the coolant is in the expansion tank.
The required coolant level in the tank is maintained in the circuit with fresh coolant or dump-
ing it into the drainage tank. An emergency cooling pump is automatically switched on if the
main circulating pumps stop . This pump serves as a make-up and fills the circuit with fresh
coolant which is preliminarily poured into the filling tank.
?2. GRAPHITE CORE OF REACTOR
The high temperature of the coolant and the large volume heat release in thk: fuel elements
resulted in high temperatures of the graphite core. Nitrogen with an oxygen content of up to 0.2%
in volume was added to the core at the APS in order to protect the graphite from burning up at
high reactor temperatures.
A ten-year period of operation of the graphite core at temperatures up to 800?C and a high
neutron flux showed that there was a low burn-up of the graphite in a nitrogen medium. It must
be noted, that operating in nitrogen conditions filling the reactor core, there was a constant
maintenance of oxygen, hydrogen and carbon dioxide content at a level of 1% in volume. A vi-
sual check of the surface of the graphite-blocks in the reactor, and measuring the diameters of
their. holes.at different points of the height of the core, made it possible to draw the conclusion,
that the graphite core of the reactor at the-APS after 10 years of operation was in a quite
satisfactory condition.
Fig. 4 shows a chart of the diameter changes of the holes in one of the core cells along tho
reactor height,. after ten years.of core operation under conditions of neutron irradiation and high
temperatures in a nitrogen medium.
The chart shows that there was a maximum decrease of the diameter holes of the graphite
blocks in the centre of the core. The hole decreased from the nominal diameter of 65.0 mm to
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a diameter `of 64.8 mm, i.e, by 0.1 mm along the radius., Such large deformations of the
graphite-blocks do not eliminate -the -designed -gaps between the-block and channel and that
is why they areno hindrance to installing and-removing channels from the reactor.
The, integrated flux of fast and thermal neutrons along the centre -of the core in a given
cell was 0.5.1022n/cm2, and the graphite temperature on the inner surface of the block,in
operating conditions was 6500C. The diameter of the holes was measured with an expecially
designed meter with an automatic recording device. Taking into account the accuracy of the
measurements, it can be considered that the volume changes in the graphite blocks after a
long period of operation in the reactor of the First A.P.S. do not exceed 0.15%.
In order to determine the further increase of the operating temperatures of the graphite,
a study was made of the graphite behaviour in a nitrogen medium at temperature intervals of
7000-11500C. The continuous method of weighing the sample in a gas flow was used to deter-
mine the speed of graphite oxidation.
In order to eliminate the influence of the gas flow velocity, the study was made in so-cal-
led "kinetic conditions", where the speed of oxidation reaction does not depend on the velocity
of the gas flow (with consumption more than 200 1/hr).
For a quantitative determination of the process the specific speed of oxidation Ks, was
used which is equal:
Ks =
Ax P
S A t CM2 COK
where Ax - change of sample weight, grins.,
At - time of experiment, secs.,
S - surface of sample, cm2.
The experiments were made on graphite samples irradiated with an integral dose
(0.4 + 0.8) ? 1021P/cm2 (fast and thermal neutrons), in a medium of irradiated and unirradia-
ted nitrogen in the reactor.
On the basis of the experiments a dependence of the specific velocity of oxidation to the
temperature was drawn up which is shown in Fig.5. The chart shows, that by increasing' the
temperature from 7000 to 1150?C the oxidation speed in a nitrogen medium increases approxima-
tely ten-fold. Certain differences of the oxidation speed in irradiated and..unirradiated nitrogen
in temperatures of 7000-1000?C may be explained by the distinctions in the integral doses of
irradiation of the sample (as is known in practice, the higher the integral dose, the greater the
oxidation speed).
It is interesting to note, that beginning with 1000?C this difference in oxidation speed
decreases and completely vanishes at 11500C. This phenomenon found in high temperatures,
can be explained to a certain extent by the annealing of 'radiation damage in the graphite.
The initial nitrogen used in the experiments contained the following admixture':
oxygen 0.001 0.002%,
carbon dioxide 0.04 - 0.4%,
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carbon* monoxide