37

INCREASING EFFICIENCY OF FIXTURE PLANNING BY AUTOMATING SOME PLANNING STEPS

planning steps – they take remarkably less time.

Figure 8 Gearbox housings [11]

Table 1 The time needed for different stages of the fixture planning and design [11]

Stages of the fixture planning and design

Gearbox housings

Part A Part B Part C Part D

Regeneration of the model and feature recognition 1 min 8 s 9 s 10 s 7 s

Defining machining requirements 12 min 9 min 13 min 7 min

Finding the conceptual solution of the fixture 1 min 42 s 1 min 8 s 2 min 10 s 1 min 56 s

Fixture configuration Auxiliary setup 56 s

Main setup 32

s

Auxiliary setup 46 s

Main setup 22 s

Auxiliary setup 41 s

Main setup 28 s

Auxiliary setup 30 s

Main setup 24 s

References

[1] J. R.. Boerma, H. J. J. Kals: „FIXES, a System for

Automatic Selection of Setups and Design of Fixtures”,

Annals of CIRP Vol. 37/1, 1988. pp. 443-446.

[2] A. Joneja, T-C Chang „Setup and fixture planning in

autmated process planning systems”, IIE Transaction

31, 1999. pp. 653-665.

[3] W. Ma, J. Li and Y. Rong, „Development of Automated

Fixture Planning Systems”, Int. J. of Adv. Manuf.

Techn. 15, pp. 171-181, 1999.

[4] M. Horváth, A. Márkus, J. Váncza „Process planning

with genetic algorithms on results of knowledge-based

reasoning”, Int. J. Comp. Integ. Manuf. 9,No.2, 1996,

pp. 145-166.

[5] M. Marefat, J. Britanik „Case-based process planning

using an object-oriented model representation”, Robo.

and Comp.-Integ. Manuf. 13, No. 3, 1997. pp. 229-251..

[6] H. Paris, D. Brissaud „Process planning strategy based

on fixturing indicator evaluation”, Int. J. of Adv.

Manuf. Techn. 25, pp. 913-922, 2005.

[7] S. Bansal, S. Nagarajan, N. Venkata Reddy „An

integrated fixture planning system for minimum

tolerances”, Int. J. of Adv. Manuf. Techn. 38, pp. 501-

513, 2008.

[8] A. Rétfalvi “IGES-based CAD model postprocessing

module of a Setup and Fixture Planning System for box-

shaped parts”, IEEE 9th Symp. on Intel. Syst. and Inform.,

September 8-10, 2011, Subotica, Serbia

[9] M. Stampfer „Integrated Setup and Fixture Planning

System for Gearbox Casings”, Int. J. of Adv. Manuf.

Techn., 26, pp.310-318, 2005.

[10] M. Stampfer „Automated setup and fixture planning

system for box-shaped parts”, Int. J. of Adv. Manuf.

Techn. 45, pp. 540-552, 2009.

[11] A. Rétfalvi „Fixture Design System with Automatic

Generation and Modification of Compementary Elements

for Modular Fixtures”, Acta Polytechnica Hungarica,

vol.12, No.7, pp. 163-182, 2015

EXPRES 2017

ISBN 978-86-919769-1-0

Simulation result of a nuclear power plant cooling system using Matlab

A, SZENTE a , I. FARKAS

b, P. ODRY

c

a Paks Nuklear Power Plant, Paks, Hungary, E-mail: szentea@npp.hu b University of Dunaújváros/Computer Engineering, Dunaújváros, Hungary, E-mail: imka26@gmail.com c University of Dunaújváros/Computer Engineering, Dunaújváros, Hungary, E-mail: podry@uniduna.hu

It has been shown in recent years that there is a great need for additional security measures to be taken in high security systems in

case of occurrence of unanticipated events. A Nuclear Power Plant is exactly such kind of a sophisticated system. Thou, before

we begin to work on improving the overall security of a system, we must familiarize ourselves with the type of event that causes

the issue during an unanticipated event. For this we need a well-constructed simulation. The fortification of the removal of decay

heat following the subcritical stage of a reactor shutdown forms a significant portion of the workings of a nuclear power plant.

The lack of such a measure could lead to a catastrophic meltdown (Fukushima 2011). The necessary electrical energy for this

process under normal conditions is supplied by the primary (national and home power grids) and secondary (diesel generators)

electrical supply systems. One of the key factors of the insurance of higher plant safety could be the application of a third diverse

decay heat removal ensuring system. The solutions that we came up with were based on the observations of the Paks Nuclear

Power Plant in Hungary VVER440 type reactor cores, thou it could be reflected to any similar working nuclear power plant type.

Keywords: Nuclear Power Plant, subcritical stage of a reactor, primary electrical supply systems, security,

simulation

1. The basics of nuclear power plant

cooling

Once the adequate boric concentration is reached

during shutdown the reactor needs to be cooled down,

and kept at a desirable temperature. During cooldown

on the one hand the heat stored in the structure as well

as the decay heat generated by the active zone needs to

be removed.

During the first stage of the process, it’s necessary to

set the prescribed temperature difference of 60oC in the

primary circuit-pressurizer, using the cooling of the

pressurizer. Naturally, this implies that the pressure in

the primary circuit needs to be lowered. Later, besides

the cooling of the primary circuit it’s important to

constantly keep this difference.

Due to the constant pressure lowering in the primary

circuit, the hydro-accumulators need to be disengaged

from the primary circuit once a pI<75bar pressure is

reached, also as the primary circuit is being cooled, it’s

pressure needs to be let out by releasing the nitrogen

(to avoid any risk of brittle fracture). Once we reach a

pressure of pI≤20[bar] during the depressurization of

the primary circuit, the steam cushion in the

pressurizers needs to be changed to nitrogen. To

minimize the necessary quantity of nitrogen, it’s

imperative that the pressurizers are to be filled to their

maximal capacity (LYP10 = 7.5±0.5 m) before the

administration of nitrogen. In the following the precise

level in the pressurizers should be kept particularly in

mind, because the changes in that significantly affect the

primary circuit pressure. (Due to the continuous primary

circuit cooling, the constant level in the pressurizer can

only be ensured if the drop-in volume is substituted

continuously with water, unlike the power stage, where

per the average temperature we let the level change,

namely we keep a constant volume of water.) The

∆T=60oC between the primary circuit and the

pressurizer needs to be kept at until TI≤ 150oC,

following which it’s needs to be lowered to ∆T = 30oC.

Attention needs to be paid during the set of the

cooling speed, so as the maximum allowed is not

exceeded, therefore it must be approached from below.

In the case of huge supply tanks and big primary circuit

temperature differences the exceedance can easily

occur. The cooling must be carried out by the

Fig. 1. The remanans heat generation performance

Fig. 2. Diagram of the cooling for a normal cooling process

38

2

subtraction of steam from the fresh steam collector

until TI = 140oC is reached. The condensate condensed

in the technology condenser is returned to the

secondary supply tank. In the last third of the water-

steam cooling the heating of the supply containers

should be gradually reduced to ensure the temperature

step between the primary - secondary circuit.

While above TI>190oC it’s advisable to avoid a too

high active zone pressure difference, an FKSZ needs to

be shut down. Because of the even cooling of primary

circuit pipes, the shutdown FKSZ needs to be restarted

(TI =175 and at 160oC) once we stopped an operator.

Once TI< 150oC is reached the speed of cooling drops

significantly, because the ∆T between the supply water

and the primary circuit is low. Once a stable value of

below 150oC is reached, the system should be switched

from steam – water to water – water cooling. To do

this the GF, fresh steam lines, fresh steam collectors,

and the cooling system should be filled with feed

water. Before the start of the filling, prevention of

inadvertent defense operations must take place, the

security of the GF’s need to be paralyzed on the BER

panel, because LGF>Lnominal+600mm excludes the

upload path. The speed of the filling needs to be set in

such a way that it’s minimum 3.5h’s. At this stage of

the cool-down the migration from the Stepped Start

Programs to the SSP II should be checked. The switch

to this program also means that some elements of the

ZÜHR systems are no longer needed now, in fact their

trigger could lead to adverse consequences, and

therefore, they should be staggered.

(Eg., Under pressure, still closed, but cooled reactor, if

the TH pumps are started even if for a false signal, we

can go beyond the allowed pressure of the brittle

temperature in seconds, or the sprinkler system starts

for a wrong signal, since on this primary temperature

it’s unlikely that even in the event of a broken pipe the

pressure of the containment reaches the limit.)Since

the amount of heat removal is steadily declining over

the filling, care should be taken that the primary circuit

does not warm up to above 150°C.

After filling the secondary side, the cooling must

continue a water - water mode of operation using five

FKSZ while TI <100°C is reached. The secondary side

circulation is ensured by chilling pumps. If the primary

circuit average temperature is below 100°C, the FKSZ’s

need to be stopped by detaching the earlier used two

loops. Secondary side steam generators that have been

taken out of the plant loops should not be excluded,

ensuring their intense chilling. Their detachment should

be carried out at TGF fal≤ 4°C but no later than before the

reactor is depressurized. If the difference in temperature

between the pressurizer and the added water is ∆T < 80oC

the cooling of the pressurizer can be continued by using

supplement pumps

2. The simulation of the cooling

To be able to analyze the task, in the first step let’s see

how large this energy is [1,5]. The codes that use

numerical methods to estimate the remnant heat (decay

heat) (Melcor, Relap 1-2-3, Trac, Origen) are capable to

model the state with a precision of 3-5%.

A. The simulation of remanent heat

Using MATLAB R2013a with numerical methods we

simulated (Figure 5.), a T=335days constantly

operational P0 = 1485MWt („Megawatt thermal”) heat

energy producing reactor, it’s remnant heat 10 days

following it’s shutdown (864000s) is shown on figure6.

This value even after ten days is more than 3MWt.

Fig. 3. Tipical cooling diagram for a rector block

Fig. 4. Change of the remanent thermal power in six-month

period at the Fukushima power plant

3

The algorithm used [M. Ragheb, 3/22/2011] [2]:

P(t) = 6.48x10-3

P0 [t -0.2

– (t+T0) -0.2

] [MWt] (1)

B. The emergency stop in the system after shutdown

Hereinafter, we excited the SCRAM (emergency

stop) signal shutdown reactor and associated metalwork

combined transfer function with the current heat output

signal (Figure 7.).

The transfer function was determined by a single

proportional storage member (PT1) function,

determined because of water and metal mass,

considering the reactor, fuel, main water circuit lines,

primary coolant masses and specific heat values.

Without forced circulation or additional heat removal,

using an account with very high heat storage capacity,

the output function scaled in average temperatures

even after ten days shows a monotonic character

(Figure 4.). Assuming continuously available (fixed)

emergency stop heat extracting system and power, the

about 4MWt heat removal reverses its trend on the

seventh day, at a temperature of 300°C (Figure 8, the

third chart).

Fig. 5. Simulation modelling of remanent heat

Fig. 6. The simulated remanent thermal power

Fig. 7. Extended simulation model

39

2

subtraction of steam from the fresh steam collector

until TI = 140oC is reached. The condensate condensed

in the technology condenser is returned to the

secondary supply tank. In the last third of the water-

steam cooling the heating of the supply containers

should be gradually reduced to ensure the temperature

step between the primary - secondary circuit.

While above TI>190oC it’s advisable to avoid a too

high active zone pressure difference, an FKSZ needs to

be shut down. Because of the even cooling of primary

circuit pipes, the shutdown FKSZ needs to be restarted

(TI =175 and at 160oC) once we stopped an operator.

Once TI< 150oC is reached the speed of cooling drops

significantly, because the ∆T between the supply water

and the primary circuit is low. Once a stable value of

below 150oC is reached, the system should be switched

from steam – water to water – water cooling. To do

this the GF, fresh steam lines, fresh steam collectors,

and the cooling system should be filled with feed

water. Before the start of the filling, prevention of

inadvertent defense operations must take place, the

security of the GF’s need to be paralyzed on the BER

panel, because LGF>Lnominal+600mm excludes the

upload path. The speed of the filling needs to be set in

such a way that it’s minimum 3.5h’s. At this stage of

the cool-down the migration from the Stepped Start

Programs to the SSP II should be checked. The switch

to this program also means that some elements of the

ZÜHR systems are no longer needed now, in fact their

trigger could lead to adverse consequences, and

therefore, they should be staggered.

(Eg., Under pressure, still closed, but cooled reactor, if

the TH pumps are started even if for a false signal, we

can go beyond the allowed pressure of the brittle

temperature in seconds, or the sprinkler system starts

for a wrong signal, since on this primary temperature

it’s unlikely that even in the event of a broken pipe the

pressure of the containment reaches the limit.)Since

the amount of heat removal is steadily declining over

the filling, care should be taken that the primary circuit

does not warm up to above 150°C.

After filling the secondary side, the cooling must

continue a water - water mode of operation using five

FKSZ while TI <100°C is reached. The secondary side

circulation is ensured by chilling pumps. If the primary

circuit average temperature is below 100°C, the FKSZ’s

need to be stopped by detaching the earlier used two

loops. Secondary side steam generators that have been

taken out of the plant loops should not be excluded,

ensuring their intense chilling. Their detachment should

be carried out at TGF fal≤ 4°C but no later than before the

reactor is depressurized. If the difference in temperature

between the pressurizer and the added water is ∆T < 80oC

the cooling of the pressurizer can be continued by using

supplement pumps

2. The simulation of the cooling

To be able to analyze the task, in the first step let’s see

how large this energy is [1,5]. The codes that use

numerical methods to estimate the remnant heat (decay

heat) (Melcor, Relap 1-2-3, Trac, Origen) are capable to

model the state with a precision of 3-5%.

A. The simulation of remanent heat

Using MATLAB R2013a with numerical methods we

simulated (Figure 5.), a T=335days constantly

operational P0 = 1485MWt („Megawatt thermal”) heat

energy producing reactor, it’s remnant heat 10 days

following it’s shutdown (864000s) is shown on figure6.

This value even after ten days is more than 3MWt.

Fig. 3. Tipical cooling diagram for a rector block

Fig. 4. Change of the remanent thermal power in six-month

period at the Fukushima power plant

3

The algorithm used [M. Ragheb, 3/22/2011] [2]:

P(t) = 6.48x10-3

P0 [t -0.2

– (t+T0) -0.2

] [MWt] (1)

B. The emergency stop in the system after shutdown

Hereinafter, we excited the SCRAM (emergency

stop) signal shutdown reactor and associated metalwork

combined transfer function with the current heat output

signal (Figure 7.).

The transfer function was determined by a single

proportional storage member (PT1) function,

determined because of water and metal mass,

considering the reactor, fuel, main water circuit lines,

primary coolant masses and specific heat values.

Without forced circulation or additional heat removal,

using an account with very high heat storage capacity,

the output function scaled in average temperatures

even after ten days shows a monotonic character

(Figure 4.). Assuming continuously available (fixed)

emergency stop heat extracting system and power, the

about 4MWt heat removal reverses its trend on the

seventh day, at a temperature of 300°C (Figure 8, the

third chart).

Fig. 5. Simulation modelling of remanent heat

Fig. 6. The simulated remanent thermal power

Fig. 7. Extended simulation model

40

4

It should be noted, a lesser value is also capable of

reversing the trend, that is to cause cooling, since the

thermal decomposition function decreases

monotonically, the question is when and how long will

it allow the average temperature to climb up. In the

case of our operating systems protection signals are

formed at - 305°C and 310°C values, it is not

appropriate to allow a higher value for a standing

block either. An obvious question is whether the huge,

metal and water - weight stored heat energy should be

directly converted in to electrical energy by an

electrical (TEG) converter and used for powering the

residual heat removal as a "third kind" diverse

authoritarian type supply.

Main equipment otherwise covered with insulation if

you cover them with TEG –considering characteristics

of temperature and ventilation of the area (the box) will

continue, - it is required due to cold-side heat removal

by the TEG–to generate approximately 2.5 - 3.0MW of

electricity, if we assume current TEG efficiencies [4].

C. The installation of TEG as a residual heat-

absorber

A system thus formed, from a thermal perspective is a

negative feedback system, which guarantees safety (9)

for protection against overtemperature. The

thermoelectric generator in the feedback path can also

be modeled as a PT1 member, however, it’s time

constant is much smaller than the pre-coupling loop, the

time constant of the technology.

The thus constructed MATLAB model can be seen on

figure 10., while the cooling curves are shown on figure

11. The “minima” function that does not allow the

temperature to climb above 300°C, should have at least

a transfer function. Increasing the time

constant does not affect the shape of the curve, it

determines the availability of electric power that can be

extracted from the TEG, while the proportional transfer

component has effect on the slope of the cooling.

Fig. 8. Without forced circulation or additional heat

removal SCRAM

PT1

PT1

-

TEG

Technológia

Fig. 10. The model of effect for incorporated TEG heat removal

5

D. TEG as a residual heat-absorber

The increase of storage capacity can be resolved by the

storage of electricity generated by the TEG’s in

batteries (Figure 12).

During the campaign, the heat produced is

continuously "there" in a time after SCRAM as well in

the form of stored heat, so during the residual heat

removal’s critical stage of 2-3 days the multiple

amount of charger (conditioning)power could be

removed from the batteries to maintain the circulation.

Each plant has a battery-supported DC rail (220V or

24V), so building that will not be an additional cost.

3. Analysis of a nuclear power plant from

the usage perspective of a TEG

The thermopile technology is turning out to be an

interesting application in the field of nuclear power

plants. It has been successfully used for some time

now in outer space electric power generation [3]. It

holds additional capabilities in high-energy nuclear

systems. Continued, we explore these application

possibilities in this article.

Nuclear power plants are essentially thermal power

plants fueled by nuclear fission reactions. Instead of the

conventional burning of fuels like in the furnaces of

thermal power plants, nuclear reactions in the reactor

are generating the energy. However, using the hot water

coming out the reactor, only relatively low pressure (40-

60bar) saturated steam can be produced, so the cycle’s

parameters are rather moderate. This is the cause of the

relatively low efficiency of nuclear power plants (η = 30

- 40%). The following table shows the thermal

characteristics of the main types of thermal reactors:

Huge volumetric heat capacity and low efficiency

entail considerable heat loss. This parameter gives a

good chance for the study of the application of

thermopile effect. The study of the usage of thermopile

cells in nuclear power plants could cover case studies

of:

- detailed exploration of the heat loss in certain

reactors (holding tanks, heat exchange pipes, rotary

machines)

- for the calculation of recoverable electrical energy,

and the maximum increase in efficiency

- for the thus obtained usability of the electrical

energy for feed-in the safety system, increasing the

availability of the safety system.

4. Performance conditions, normal VVER 440

reactor shutdown needs

Given that only measuring circuits and signal

processing systems (providing feedback information)

are used and for emergency powering of about 4 -

20mA, this implies a few 100W of power demand. (In

this case, the wireless sensor technology, as a stand-by

measuring system can play a significant role, but power

consumption is not a major surplus.)

Power consumption of a residual heat removal

(cooling), after normal or emergency shutdown, during

the cooling period from 72 to 120 hours, considering the

main consumers:

- 2 pc of main circulation pumps 1600kW/pump

(6kV);

- 1 pc Feed pump 2500kW (6kV)

- 1 pc Emergency pump 200kW (0.4kV)

0.0015

700S + 0.1YTEG =

0.015

700S + 0.1

0.15

700S + 0.1

YTEG =

YTEG =

Fig. 11. The simulation results for the installated TEG

heat removal

SCRAM

PT1

PT1

-

TEG

Technológia

akkutelep

Fig. 12. Model of installated battery pack system

Table 1. Thermal charachterictic of reactor types

Reactor PWR BWR GGR AGR HTGR Volumetric heat capacity (W/cm3)

70-110 40-50 3-5 5-10 10-20

Efficiency (%)

30-40 30-40 30-40 40-45 40-45

PWR (Pressurized Water Reactor)

BWR (Boiling Water Reactor)

GGR (Gas cooled, Graphite moderated Reactor)

AGR (Advanced Gas cooled Reactor)

HTGR (High Temperature, Gas cooled Reactor)

41

4

It should be noted, a lesser value is also capable of

reversing the trend, that is to cause cooling, since the

thermal decomposition function decreases

monotonically, the question is when and how long will

it allow the average temperature to climb up. In the

case of our operating systems protection signals are

formed at - 305°C and 310°C values, it is not

appropriate to allow a higher value for a standing

block either. An obvious question is whether the huge,

metal and water - weight stored heat energy should be

directly converted in to electrical energy by an

electrical (TEG) converter and used for powering the

residual heat removal as a "third kind" diverse

authoritarian type supply.

Main equipment otherwise covered with insulation if

you cover them with TEG –considering characteristics

of temperature and ventilation of the area (the box) will

continue, - it is required due to cold-side heat removal

by the TEG–to generate approximately 2.5 - 3.0MW of

electricity, if we assume current TEG efficiencies [4].

C. The installation of TEG as a residual heat-

absorber

A system thus formed, from a thermal perspective is a

negative feedback system, which guarantees safety (9)

for protection against overtemperature. The

thermoelectric generator in the feedback path can also

be modeled as a PT1 member, however, it’s time

constant is much smaller than the pre-coupling loop, the

time constant of the technology.

The thus constructed MATLAB model can be seen on

figure 10., while the cooling curves are shown on figure

11. The “minima” function that does not allow the

temperature to climb above 300°C, should have at least

a transfer function. Increasing the time

constant does not affect the shape of the curve, it

determines the availability of electric power that can be

extracted from the TEG, while the proportional transfer

component has effect on the slope of the cooling.

Fig. 8. Without forced circulation or additional heat

removal SCRAM

PT1

PT1

-

TEG

Technológia

Fig. 10. The model of effect for incorporated TEG heat removal

5

D. TEG as a residual heat-absorber

The increase of storage capacity can be resolved by the

storage of electricity generated by the TEG’s in

batteries (Figure 12).

During the campaign, the heat produced is

continuously "there" in a time after SCRAM as well in

the form of stored heat, so during the residual heat

removal’s critical stage of 2-3 days the multiple

amount of charger (conditioning)power could be

removed from the batteries to maintain the circulation.

Each plant has a battery-supported DC rail (220V or

24V), so building that will not be an additional cost.

3. Analysis of a nuclear power plant from

the usage perspective of a TEG

The thermopile technology is turning out to be an

interesting application in the field of nuclear power

plants. It has been successfully used for some time

now in outer space electric power generation [3]. It

holds additional capabilities in high-energy nuclear

systems. Continued, we explore these application

possibilities in this article.

Nuclear power plants are essentially thermal power

plants fueled by nuclear fission reactions. Instead of the

conventional burning of fuels like in the furnaces of

thermal power plants, nuclear reactions in the reactor

are generating the energy. However, using the hot water

coming out the reactor, only relatively low pressure (40-

60bar) saturated steam can be produced, so the cycle’s

parameters are rather moderate. This is the cause of the

relatively low efficiency of nuclear power plants (η = 30

- 40%). The following table shows the thermal

characteristics of the main types of thermal reactors:

Huge volumetric heat capacity and low efficiency

entail considerable heat loss. This parameter gives a

good chance for the study of the application of

thermopile effect. The study of the usage of thermopile

cells in nuclear power plants could cover case studies

of:

- detailed exploration of the heat loss in certain

reactors (holding tanks, heat exchange pipes, rotary

machines)

- for the calculation of recoverable electrical energy,

and the maximum increase in efficiency

- for the thus obtained usability of the electrical

energy for feed-in the safety system, increasing the

availability of the safety system.

4. Performance conditions, normal VVER 440

reactor shutdown needs

Given that only measuring circuits and signal

processing systems (providing feedback information)

are used and for emergency powering of about 4 -

20mA, this implies a few 100W of power demand. (In

this case, the wireless sensor technology, as a stand-by

measuring system can play a significant role, but power

consumption is not a major surplus.)

Power consumption of a residual heat removal

(cooling), after normal or emergency shutdown, during

the cooling period from 72 to 120 hours, considering the

main consumers:

- 2 pc of main circulation pumps 1600kW/pump

(6kV);

- 1 pc Feed pump 2500kW (6kV)

- 1 pc Emergency pump 200kW (0.4kV)

0.0015

700S + 0.1YTEG =

0.015

700S + 0.1

0.15

700S + 0.1

YTEG =

YTEG =

Fig. 11. The simulation results for the installated TEG

heat removal

SCRAM

PT1

PT1

-

TEG

Technológia

akkutelep

Fig. 12. Model of installated battery pack system

Table 1. Thermal charachterictic of reactor types

Reactor PWR BWR GGR AGR HTGR Volumetric heat capacity (W/cm3)

70-110 40-50 3-5 5-10 10-20

Efficiency (%)

30-40 30-40 30-40 40-45 40-45

PWR (Pressurized Water Reactor)

BWR (Boiling Water Reactor)

GGR (Gas cooled, Graphite moderated Reactor)

AGR (Advanced Gas cooled Reactor)

HTGR (High Temperature, Gas cooled Reactor)

42

6

In the last stages of cooling only two cooling

pumps are operating (160kW/machine, 0.4kV voltage).

Additional one needs to add the above (typically relay

activated) control, measurement and control loops

consumption as well. During the stage of shut down

the greatest power requirement approximately is

6000kW (6MW), which after 72-120 drops to 300 -

400kW. It’s not negligible that the “big” pumps have

6kV 50Hz voltage needs.

Emergency core cooling systems power

consumption, for an automatic protection signal in case

of declared types of breakdown is:

- 3 pc High pressure emergency core pump

520kW/pump, 6kV

- 3 pc Low pressure emergency core pump

125kW/pump, 0.4kV

- 3 pc Spinkler system pump160kW/pump,

0.4kV.

Given for worst case emergency scenario, an

approximately 2500kW power demand occurs in the

emergency cooling period.

The surface temperature of the reactor (more

precisely the reactors metal walls temperature) is being

constantly monitored and registered, illustrated on a

self-made P&I schema which means the usage of 3

Pt46 resistance-thermometers (YA00T101B1, B3, B5

alphanumeric measurements, disposed 120° relative to

each other). During normal operation, at any point in

time these measurements show values of 240°C-

250°C. I am not aware of the surface temperature

distribution modeling, but this is the true value for

about the entire wall surface. The blue colored

measurements are computer measurement, they are

available in an archived (trend) form. The trend shows

the temperature measurements of six concrete consoles

(YA00T001B1-B6).

5. Approximation of the extractable power

with the TEG

An assessment of the potential primary circuit

surfaces: in the situation with six main water conduits,

their coverable length with TEG in total is 120m,

accounted for a hot and cold branch of 10-10m.

Obviously, the treatment, operation equipment, nozzles,

valves, thermometer bag places cannot be affected with

the TEG covering. With a 560mm diameter, main water

conduit, on most the pipe surfaces we can have access to

a usable surface of 210m2, with 270°C average

temperature. This means that on the cold end 250°C, on

the hot end 280°C temperatures can heat the placed

TEG’s. Calculating with six, 10m long, 4m diameter

steam generators we get a surface of 754m2, at 220°C

which is coverable. A major piece of equipment surface

is the pressurizer where the coverable area is 52m2, but

the temperature of the surface is 280°C. The similar

exploration of the secondary circuit: a 135m long,

465mm diameter main steam pipe means a surface of

197m2, at 220°C. Calculating with a water supply

system average temperature of 180°C, with a 426mm

diameter on 120m length, we get a similar surface of

160m2. The major secondary containers, low - and high-

pressure preheater lines, supply containers usable

surfaces relative to the block are: 395m2, 100°C average

temperature preheater, 480m2, 200°C average

temperature high pressure preheater, two 105m2, 150°C

temperature supply tanks. The above are the major

places for energy retrieval, leaving out the auxiliary

systems and small unusable surfaces. The room

temperatures, „cold side temperatures” are between

30°C - 50°C.

Fig. 13. Self-made P&I schema

Fig. 14. TEG material pair efficieny

7

Thanks to Thomson, Seebeck and Peltier’s research,

we use thermocouples for measurement purposes for a

long time now. However, the phenomenon of using it

as an energy source application is made possible

through experimenting with new materials. One of the

best types of such thermoelectric modules (TEG’s)

with the best thermoelectric properties is the bismuth-

telluride (Bi2TE3) based pseudo-binary group of alloys.

Figure 7. shows some of the more important TEG

material pairs efficiency as a function of temperature.

6. Summary

In this paper, we have tried to show how is it possible

to simulate processes taking place in an abandoned

nuclear power plant. As you can see this can be

resolved perfectly using MATLAB. We have outlined

the theoretical possibility of usage of residual heat

removal using a third, diverse way method. In further

studies, we try to put more emphasis on the fine tuning

of the simulated system and to clarify the physical

realization of the possibilities.

During the study, it can be concluded that, yes, there is

justification in using the TEG in nuclear power plants.

We may have to wait a few years so that TEG’s with

such parameters hit the market that enable greater power

generation (and thus enabling the operation of stronger

motors with them), but the results outlined here are said

to be promising. If we only consider that the resulting

2.68MW, the daily consumption of a small town, can be

covered by it, or it can supply the mentioned measuring

and signaling devices current needs, we should look at it

as it is worth it. In any case, its usage is worth further

consideration when critical outages, or emergencies

occur.

Acknowledgements This work/publication is supported by the EFOP-3.6.1-

16-2016-00003 project. The project is co-financed by

the European Union.

References [1] Laszlo Kajtar, Jozsef Nyers, Janos Szabo: Dynamic

thermal dimensioning of underground spaces;

Volume 87, 1 July 2015, Pages 361–368

[2] M. Ragheb: Decay heat generation in fission

reactors, 3/22/2011

[3] A. Szente, I. Farkas and P. Odry: The application of

ThermopileTechnology in high Energy Nuclear

Power Plants,Expres 2014

[4] http://www.tecteg.com/

[5] Nyers József, Kajtar Laszlo, Slavica Tomic, Nyers

ArpadInvestment-savings Method for Energy-

economic Optimization of External Wall Thermal

Insulation ThicknessENERGY AND BUILDINGS

86: pp. 268-274. (2014)

Hot side

Heat source temperature: 500°C Hot side temperature 480°C Cool side temperature: 45°C Open circuit voltage: 19.45V Output voltage: 9.75V Load current: 1.13 A Output power: 11.0 W Surface: 0.004 m2

Cool side Fig. 15. CMO-32-62S CASCADE TEG module

43

6

In the last stages of cooling only two cooling

pumps are operating (160kW/machine, 0.4kV voltage).

Additional one needs to add the above (typically relay

activated) control, measurement and control loops

consumption as well. During the stage of shut down

the greatest power requirement approximately is

6000kW (6MW), which after 72-120 drops to 300 -

400kW. It’s not negligible that the “big” pumps have

6kV 50Hz voltage needs.

Emergency core cooling systems power

consumption, for an automatic protection signal in case

of declared types of breakdown is:

- 3 pc High pressure emergency core pump

520kW/pump, 6kV

- 3 pc Low pressure emergency core pump

125kW/pump, 0.4kV

- 3 pc Spinkler system pump160kW/pump,

0.4kV.

Given for worst case emergency scenario, an

approximately 2500kW power demand occurs in the

emergency cooling period.

The surface temperature of the reactor (more

precisely the reactors metal walls temperature) is being

constantly monitored and registered, illustrated on a

self-made P&I schema which means the usage of 3

Pt46 resistance-thermometers (YA00T101B1, B3, B5

alphanumeric measurements, disposed 120° relative to

each other). During normal operation, at any point in

time these measurements show values of 240°C-

250°C. I am not aware of the surface temperature

distribution modeling, but this is the true value for

about the entire wall surface. The blue colored

measurements are computer measurement, they are

available in an archived (trend) form. The trend shows

the temperature measurements of six concrete consoles

(YA00T001B1-B6).

5. Approximation of the extractable power

with the TEG

An assessment of the potential primary circuit

surfaces: in the situation with six main water conduits,

their coverable length with TEG in total is 120m,

accounted for a hot and cold branch of 10-10m.

Obviously, the treatment, operation equipment, nozzles,

valves, thermometer bag places cannot be affected with

the TEG covering. With a 560mm diameter, main water

conduit, on most the pipe surfaces we can have access to

a usable surface of 210m2, with 270°C average

temperature. This means that on the cold end 250°C, on

the hot end 280°C temperatures can heat the placed

TEG’s. Calculating with six, 10m long, 4m diameter

steam generators we get a surface of 754m2, at 220°C

which is coverable. A major piece of equipment surface

is the pressurizer where the coverable area is 52m2, but

the temperature of the surface is 280°C. The similar

exploration of the secondary circuit: a 135m long,

465mm diameter main steam pipe means a surface of

197m2, at 220°C. Calculating with a water supply

system average temperature of 180°C, with a 426mm

diameter on 120m length, we get a similar surface of

160m2. The major secondary containers, low - and high-

pressure preheater lines, supply containers usable

surfaces relative to the block are: 395m2, 100°C average

temperature preheater, 480m2, 200°C average

temperature high pressure preheater, two 105m2, 150°C

temperature supply tanks. The above are the major

places for energy retrieval, leaving out the auxiliary

systems and small unusable surfaces. The room

temperatures, „cold side temperatures” are between

30°C - 50°C.

Fig. 13. Self-made P&I schema

Fig. 14. TEG material pair efficieny

7

Thanks to Thomson, Seebeck and Peltier’s research,

we use thermocouples for measurement purposes for a

long time now. However, the phenomenon of using it

as an energy source application is made possible

through experimenting with new materials. One of the

best types of such thermoelectric modules (TEG’s)

with the best thermoelectric properties is the bismuth-

telluride (Bi2TE3) based pseudo-binary group of alloys.

Figure 7. shows some of the more important TEG

material pairs efficiency as a function of temperature.

6. Summary

In this paper, we have tried to show how is it possible

to simulate processes taking place in an abandoned

nuclear power plant. As you can see this can be

resolved perfectly using MATLAB. We have outlined

the theoretical possibility of usage of residual heat

removal using a third, diverse way method. In further

studies, we try to put more emphasis on the fine tuning

of the simulated system and to clarify the physical

realization of the possibilities.

During the study, it can be concluded that, yes, there is

justification in using the TEG in nuclear power plants.

We may have to wait a few years so that TEG’s with

such parameters hit the market that enable greater power

generation (and thus enabling the operation of stronger

motors with them), but the results outlined here are said

to be promising. If we only consider that the resulting

2.68MW, the daily consumption of a small town, can be

covered by it, or it can supply the mentioned measuring

and signaling devices current needs, we should look at it

as it is worth it. In any case, its usage is worth further

consideration when critical outages, or emergencies

occur.

Acknowledgements This work/publication is supported by the EFOP-3.6.1-

16-2016-00003 project. The project is co-financed by

the European Union.

References [1] Laszlo Kajtar, Jozsef Nyers, Janos Szabo: Dynamic

thermal dimensioning of underground spaces;

Volume 87, 1 July 2015, Pages 361–368

[2] M. Ragheb: Decay heat generation in fission

reactors, 3/22/2011

[3] A. Szente, I. Farkas and P. Odry: The application of

ThermopileTechnology in high Energy Nuclear

Power Plants,Expres 2014

[4] http://www.tecteg.com/

[5] Nyers József, Kajtar Laszlo, Slavica Tomic, Nyers

ArpadInvestment-savings Method for Energy-

economic Optimization of External Wall Thermal

Insulation ThicknessENERGY AND BUILDINGS

86: pp. 268-274. (2014)

Hot side

Heat source temperature: 500°C Hot side temperature 480°C Cool side temperature: 45°C Open circuit voltage: 19.45V Output voltage: 9.75V Load current: 1.13 A Output power: 11.0 W Surface: 0.004 m2

Cool side Fig. 15. CMO-32-62S CASCADE TEG module