Schedule and Nuclear School Experiment

SCHEDULE OF NUCLEAR SCHOOL EXPERIMENT

WaktuTuesday

April 14, 2015

08.00 ~ 09.00 Overview of experiment

09.00 ~ 09.30 experiment star-up and operation reactor (protocol 2)

09.30 ~ 10.00 Rod Callibration experiment (protocol 4)

10.00 ~ 10.30 experiment on Reactor Kinetics and dynamics (protocol 3)

10.30 ~ 12.00experiment on Coefficient negative temperature (protocol 5)and power callibration

(protocol 7)

12.00 ~ 13.00

13.00 ~ 14.00

Discussion and evaluation14.00 ~ 15.00

15.00 ~ 16.00

Reactor Physics and Nuclear Engineering

Kartini reactor

General

Kartini reactor is located in Yogyakarta Special District of Indonesia. This reactor is TRIGA type reactor (Training, Research, Isotope production/irradiation of General Atomic). Uranium Zirconium Hydride (UZrH) fuel with 19.75% enrichment is used.The reactor has a nominal power of 100 kW, it is cooled by light water. The cooling waterisdemineralized and circulated by the primary cooling system. The reactor hall is equipped with a ventilation system in order to maintain the negative air pressure in reactor hall above0.1 cm H2O.Inherent safety of a TRIGA fuel type is robust to handle the changes in reactor power operating due to large reactivity temperaturecoefficient. The reactor is equipped with three control rods: a safety rod, a shim (compensating) rod, and a regulating rod, which is used to regulate the reactor operation. Any abnormal operation will cause the reactor to scram, i.e.all control rods will fall in the core. The rods being in their lower position, the reactor will be in a shutdown state.

The applications of the Kartini reactor are: the education and training, research and neutron activation analysis.

The three safety principles in Kartini reactor are:- The control of the neutron production due to the fission reaction in the reactor core

using the control rods as well as a the neutron detection systems, - the confinement of the isotope production, due to fission reaction in fuel, usingthe

claddingof the fuel,- the cooling of the core by the removal of the energy produced by fission and gamma

heating in the fuel element, using the primary and secondary cooling system.

Kartini reactor is typically operated in level of power ranging from 10 W to 100 kW. One of the safety parameter of the reactor is the reactor period. The period of the reactor has to be kept above 7 seconds when increasing the power of the reactor. A period below 7 seconds leads to a reactor SCRAMby the reactor protection system. Another safety parameter is the maximum power of the reactor: if the power reaches 110 % of the nominal power the reactor is scramed by the reactor protection system. In both case, the reactor is shut down. These two parameters, the period and the power, are safety setting limit of the reactor safety system on theKartini reactor.

In the reactor hall, for radiation protection purposes, radiation monitoring systemsand gamma area monitoring (GAM) are installed. The personnel working on the Kartini reactor, including researchers, must worn personal film badge dosimeter. As for guests and students pocket

dosimeter are used.The air circulation in reactor hall uses the ventilation system which is equipped witha high efficiencyfilter in order to filter potentially activated particulates before the air is released to the environment.

Environment monitoring is done regularly everymonth in order to characterize the environmental radioactivity conditions related to the impact of reactor operation. The concentrate activities and exposure are measured using survey meter and environment material sampling such as air, sand, grass, surface water and ground water.

In order to perform reactor operation safely, all the systems of the reactor must be operational, with theirroutine calibration and maintenance schedules accomplished, and used accodrding to their operating procedures and guidelines..


Protocol N°1 - Kartini Reactor

Reactor criticality

I. Purpose

The purpose of this training course is double.

Part 1: At first, by the loading of fuel assemblies into the core, we will determine the critical mass of fissile material for the reactor.

Part 2: Once the fuel loading sequence is finalised, we will determine a critical configuration of the rods by the approach to criticality technique.

II. Theoretical Background

Reactor criticality is a condition in which the population of neutrons in the reactor core isin a steady state. The minimum mass of fissile material that allows the reactor to reachcritical state is called the critical mass.

Criticality of a reactor is measured by defining a quantity called the Keff which is the ratio of neutrons in one generation to the number of neutrons in the previous generation (without external source of neutrons). For Keff> 1 the reactor is in supercritical conditions, in this case the population of neutrons in the reactor core continuously increases with time. Conversely, if K eff< 1,the reactor is subcritical and the number of neutrons decreases with time. The reactor is in a critical condition when the Keff = 1.

In this experiment, the determination of the critical mass is done by recording the neutron detector signal (proportional to the neutron density) against the number of additional fuel into the core, searching for Keff = 1 conditions.

For that purpose the neutron source (AmBe) has to be inserted into the reactor core. From the number of neutrons ( S ) that enter the core at the beginning, will produce a number (Keff. S) neutrons at the end of the first generation and the number (Keff

2 . S) at the end of the second generation and so on.

The total multiplicity of neutrons in the core becomes

forKeff<1 the total number of neutrons in the core becomes

When the detector is placed around the core, the count rate (C) is a portion of the number of neutrons in core.

with F = fraction of neutrons that is detected.

Keff value will increase by increments of fuel, if the condition has reached a critical (Keff = 1) parameters 1/C will be zero. By knowing the weight fraction of fissile material in each fuel elements that have been inserted, the reactor critical mass can be determined.

The same technique can be applied for the determination of the critical configuration of the rods by moving the regulating rod up step by step and recording the count rate. By ploting 1/C versus the position of the rod, the critical position of the rod can be found by extrapolation.

III. Equipment

1. Counting system

2. Binocullar

3. Flashlight

4. Calculator

5. Graph paper

Part 1 – Experimenal procedures for the determination of the critical mass

1. In order to proceed with the critical mass determination, the reactor should be in the following state: 7 fuel elements in the ring F are removed and placed on a shelf in the tank. The reactor is in a sub-critical condition.

2. The neutron source is inserted into the core. The three control rodsare raised up to their

top position (fully-up). In this condition, the neutron counting rate C of the fission chamber detectors is recorded.

3. Then adjust the position of the control rods as follows

Safety rod at the top position,

Compensation rod at 50% up

Regulating rod at the bottom

4. A fuel element is inserted into its original position in the core, and then all control rodsare raised up to their top position. The counting rate C of the fission chamber detectors is recorded.

5. Plot the graph 1/C versus mass of fissile material (U-235) and check if the next fuel assembly can be loaded.

The sequence for the fuel loading, the fuel assembly number, its position in the core and its mass of U-235, are given in the following table. Report in this table the values of C and 1/C.

Fuel loading sequence

Assembly reference

Position in the core

Mass of U-235 (g)

Count rate C(c/s)

1/C

Initial state

N° 1 9538 F 03 36.83

N° 2 9891 F 05 37.37

N° 3 9875 F 13 36.94

N° 4 9535 F 18 35.70

N° 5 9542 F 22 36.15

N° 6 9541 F 23 36.10

N° 7 9539 F 25 36.73

6. Repeat the step number (3) to (5) until all the fuel elements are loaded in the core, checking that the reactor doesn’t become supercritical through theincrease of fissile material, the control rods in positions indicated in number (3).

7. When the core is loaded move all control rods down.

8. Using the graph 1/C versus the mass of fissile material (U-235), determine the critical mass of fissile material.

Notes:

One can notice that the graphical form to the critical conditions can vary, as shown in Figure 1.

Linear-shaped graph is the most ideal for extrapolating the addition of fuel on phase 1 has been able to provide estimates of the critical mass of the reactor well. Estimates obtained from stage 1 a concave curve gives the number of the critical mass that is too small, while the convex curve provides estimates that are too large. Concave shape of the curve is generally obtained when the detector position is too far away from the neutron source, while the convex curve obtained when the detector position is too close to the neutron source.

1/C

mass of fissile material

Fig.1 Graphical form to the critical conditions.

Part 2 – Experimental procedure for the determination of the critical configuration

1. In order to proceed with determination of the critical configuration of the rods, the reactor will be brought to the following state: all fuel elements are loaded, the neutron source is inserted into the core, the reactor is in a sub-critical condition with the rods in the following position :

Safety rod at the top position

Compensation rod at the 70% up

Regulating at the bottom

2. The regulating rod will be extracted step by step up to a position close to the critical position. For each position of the rod, we wait for the count rate to stabilise. Then we

record the counting rate Cand calculate 1/C (use the following table).

3.

Rod position (% )

Counting rate C(c/s)

1 / C

0

15

30

40

4. Using the recorded count rate, plot the graph 1/C versus the position of the rod (in % of the upper position).

5. From the curve, decide to move further the rod until the critical position is approached: 1/C going to zero.

6. Using the three last values (linear part of the curve for better estimate) determine the critical position of the regulating rod.

V. Reference

1. A. EDWARD PROFIO. Experimental Reactor Physics, John Wiley & Sons, New Jork, USA.

2. Course Manual Regional Training Course on the Use of PC in Research Reactor Operation and Management, Bandung, Indonesia, November 1991.


Protocol N°2- Kartini Reactor

Reactor Start Up and Operation

1. Purpose

The purpose of this training course is to get an insignth into research reactor operation,

checking the reactor state before reactor strat up and then starting up the reactor.

2. Theorical Background

Kartini reactor is used for service neutron activation analysis, gamma irradiation

experiments, education and training as well as research in the field of nuclear technology and

reactor physic. For the purposes of these services, the reactor has a number of facilities

irradiation include a Lazy Susan (LS) that can load 40 shots with a circular position outside the

reactor core, Pneumatic Transfer System, a Thermal couloumn and 4 beam ports.

At the nominale power, i.e 100 kW,the neutron flux is of about 1012 n/cm2.sec in the

centre of the core and 2.5x1011 n/cm2.sec in the LS irradiation facility.

In routine circumstances, the reactor is operated an average of 6 hours per days. It can

also be operated a longer period of time according to the needs of the experiments.

The TRIGA reactor use pure water as the coolant. The pH of water ranges from 5.5 to 7.

Water is also acting as a moderator (delay) neutrons, a shielder to prevent scattered radiation

exposure to the surface. Primay water circulation through the heat exchanger (HE) ensures that

the temperature of the water of the tank of the reactor (ATR) remains low and does not exceed

the allowed limit of 40 oC.

3. Kartini Reactor Operation

Before the reactor can be operated, 2 operators leaded by a supervisor, checkthat all the

systems are functioning properly according to checking lists. This instrumentation and control

system (I&C System) and various parameters of the reactor auxiliary systems are contrled.

There 3 kinds of checklist : start up checklist, power operationchecklist and shutdown checklist.

An additional list gives the technical specifications of the Kartini recator.

4. Experimental procedure to start up the reactor

1. As a trainee on the reactor, you will follow the procedures of the reactor. Together with the staff of the reactor you will fill the checklists and verify that the measured parameters are in accordance with the reactor specifications before starting up the reactor, operating the reactor or Shuting down the reactor.

2. In addition to the completion of this work you will have to established to conditions necessary for the start up of the reactor.

For this you need to have the following information :

- A critical configuration of the reactor, for example the one found at the end of the approach to criticality

- The calibration curve of the regulating rod – given curve specific to the reactor and to a core configuration

- The in-hour curve which relate the reactor period (or the time to multiply by 1,5 or 2 the power) and the reactivity of the core – given curve specific to the reactor

You can fill the folowing table to help you defining the actions to be taken to start up the reactor with a period of 30 secondes and to later on stabilise it at 100 W.

Position regulating rod

(%)

keff Reactivity of the core

($)

Period (s)

End of the approach to criticality < 1 < 0

Critical configuration - position

Super critical with a period of 30 secondes

30 secondes

Critical at 100 W

3. Complete the following curves showing the evolution of the power of the reactor (up to 100 W) and the corresponding evolution of the position of the regulating rod and of the reactivity of the core.

4. Due to the inherent safety of the TRIGA reactors (due to the strong and very fast temperature

feedback effect), other procedures specific to this type reactor can be applied. Thus on the Kartini reactor the common procedure to start up the reactor is as follow:

Withdraw safety rod up to 100% position Withdraw shim rod up to about 75 % position Withdraw regulating rod up to critical power 100 watt

To increase or decrease the power, operator can pull up or pull down the regulating rod due to interest power position.

5. Why is it not possible to apply this procedure on other research reactors that are not inherently safe ?

CHECKLIST STARUP

Operator : 2 persons.

Supervisor : 1 person.

Radiation Protection : 1 person

A.

B. Auxiliary System

- Primary flow rate : ........ liter/menit

- Secondary flow rate: ........ liter/menit

- Primary coolant Temperature (HE) :

- In HE : ........oC

- Out HE : ........oC

Primary Coolant Resistivity

- Demin In : ......MOhm/cm.

- Demin Out : .......MOhm/cm

- pH react. wat. tank : .......

- Secondary flow rate : .........liter/mn

Ventilation System

Blower : [.....]

C.

D. Reactor components

* Teras reaktor : [....]* Sumber neutron : [....]* Beamport : [....]* Beamport : [....]

Keterangan:

[] : Baik[X] : tidak Baik

E. Interlock

Interlock dari batang kendali:.....

F. Calibration

LCR :.......

Campbell : [....]

Periode : [....]

Linear power : [....]

G. SCRAM test

Safety rodsCompensating rods Regulating rods

Manual : [....] [....] [....]

% Power: [....] [....] [....]

Periods : [....] [....] [....]

Power Supply

HV :[....]....(setting by maintenance schedule)

H.

I. Conclusion

J. ......................................................................

K.

L. Signature :

Supervisor

( .........................................)

POWER OPERATION CHECKLIST

The power operationchecklist is performed when the reactor is operated at a significant level of

power. It is typically performed every hours when the reactor is in operation. This procedure

needs to be done to evidence any significant event at any time,so if there is a deviation it can be

immediately identified and handled to garanty safe operation.

POWER OPERATION CHECKLIST

1. Time :

2. Power :

3. Control rod positions :

Safety rods Compensating rods Regulating rods

...... % ...... % ...... %

4. Water surface temperatur (ATR) :.......oC

5. Primary temperature : in HE ….oC out HE ….oC

6. Secondary temperature : in HE ….oC out HE ….oC

7. Primary flow rate : …….liter/menit

8. Secondary flow rate :……..liter/menit

9. Fuel temperature : oC (ring B)

10. Radiation expeosure :

Reactor Deck : mR/jam

Sub Critic : mR/jam

Demineralizer : mR/jam

Thermal couloumn : mR/jam

Bulk shielding : mR/jam

Main control room : mR/jam

SHUTDOWN CHECKLIST

1. Time of Shutdown :

2. Control Rod Position :

Safety rods Compensatingrods Regulating rods

..... % .....%.... %

3. Surface water temperature (ATR):

4. Primary coolant temperature : in HE …..oC out HE …..oC

5. Secondary coolant temperature : in HE…..oC out HE …..oC

6. Primary flow rate : ...... liter/menit

7. Secondary flow rate : ...... liter/menit

8. Fuel temperature : oC (ring B)

9. Radiation exposure :

Reactor Deck : ....... mR/jam

Sub critic : ....... mR/jam

Demineralizer : ....... mR/jam

Thermal couloumn : ....... mR/jam

Bulk Shielding : ....... mR/jam

Main control room : ....... mR/jam

10. Primary system off : .............. Western time of Indonesia

11. Power supplay off : ..............

12. Core condition : [.....]

13. Reactor tank water level : ........ cm

Supervisor Explanations

………………………………………………………………………………………………………

……………………………………………………………………………………………

Signature,

(........................................... )

TECHNICAL SPECIFICATION OF THE KARTINI REACTOR

1. Power Max 100 kW

2. Minimum Periods 7 detik

3. % Power Max 110 %

4. Water tank surface temperature (ATR) 40oC

5. Fuel Temperature Max 530oC

6. Primary flow rate 140LPM

7. Secondary flow rate 520 LPM (HE Plat), 820 LPM (HE Tube)

8. Consentrate of Si, Mg, Ca, Na in ATR < 1ppm

9. Conduktivity ATR 0,2 – 0,5 micro siemen

10. Resitivity ATR in demineralizer

Inlet > 2 M/cm

Outlet > 5 M/cm

11. Radiation exposure rate

Surface water tank ( ATR) < 100 mR/jam

Main control room < 2,5 mR/jam

Reactor deck <10 mR/jam

Demineralizer < 25 mR/jam

Thermal couloumn < 2,5 mR/jam

Sub critic < 10 mR/jam

Bulk Shielding < 2,5 mR/jam

REFERENCE

1. Lamarsh, Jhon R., Introduction to Nuclear Reactor Theory Addison-Wesley Publishing

Company, New York, 1972

2. Suprawardana, Salam M., Introduction Reactor Experiments, Center for Education and

Training, National Nuclear Energy Agency.

3. Safety Aanlysis Report, Center for Sains and Accelerator Technology, National Nuclear

Energy Agency, Yogyakarta.


Protocol N°3 – Kartini Reactor

Reactors Kinetics and Dynamics

I. Purpose

Study the change in the neutron density during a reactivity transient: from a critical state, decrease and increase of the reactivity during a short period of time (20 and 60 seconds) to go back to criticality.

Measure the critical position and the temperature of the fuel for different level of power of the reactor ranging from 10 W to 100 kW.


The neutron density evolution is described by the following equations of kinetics (1 groupe of precursors):

With : n the neutron concentrationC the precursors concentrationthe reactivitythe fraction of delayed neutronsc the neutron life time at criticalitythe radioactive constant of the precursors

Two types of neutrons are present in the reactor: the prompt (first term in the dn/dt equation) and the delayed neutrons (second term in the dn/dt equation).

The delayed neutrons are emitted by the precursors after a mean time of about 11 seconds.

We will see in this experiment what is the contribution of these two types of neutrons in the evolution of the neutron density during a fast transient in the reactivity.

III. Equipment

- Videorecording system- Graph paper

IV. Experiment procedure

Part 1 – Transient with a total duration of 20 s

1. The reactor is in a critical condition at a power of 100 W. Note the critical position of the rod Hc.

2. The camera of the videoconference system is switched on to record the TV screen of the control desk that shows the evolution of the reactor parameters.

3. The regulating rod is moved down continuously for 10 seconds to decrease the core reactivity. The height reached is noted: HLow. After this 10 seconds, the regulating rod is immediateley moved up for 10 seconds to go back to the critical state (rod moved back to Hc).

4. Stop the recording of the TV screen 1 minute after the rod is back to Hc

5. Using the recorded film plot on a graph the evolution of the reactor power and the position of the rod versus time.

6. Explain the evolution of the neutron density during the transient.

Part 2 – Transient with a total duration of 120 s

7. The reactor is brought to the same initial condition as that of step 1 : 100W, rod at Hc.8. The camera of the videoconference system is switched on to record the TV screen of the

control desk that shows the evolution of the reactor parameters.9. The regulating rod is moved down by succesive steps for about 60 seconds to decrease

the core reactivity. The position HLow will have to be reached after these 60 seconds. Thus typically the rod will be moved in such a way : rod moved down for 1 second, pause for 5 seconds, rod moved down for 1 second, pause for 5 seconds, and so on until HLow is reached. Once HLow is reached, after a pause of 5 seconds, the rod is moved up in the same way : rod moved down for 1 second, pause for 5 seconds, rod moved down for 1 second, pause for 5 seconds, and so on until HC is reached.

10. Stop the recording of the TV screen 1 minute after the rod is back to Hc

11. Using the recorded film plot on a graph the evolution of the reactor power and the position of the rod versus time.

12. Explain the evolution of the neutron density during the transient.

13. Compare and comment the difference observed in the neutron evolution for the 2 experiments (Part 1 and 2).

3 – Critical position at different levels of power

1. The reactor is critical at 10 W with the Safety rod up to 100% position, Shim rod up at 75 % position.

2. Record the critical position of the Regulating rod as well as the temperature of the fuel and report it in the following table.

3. Increase the power successively to 100 W, 1 kW, 10 kW and 100 kW recording the critical position of the Regulating rod and fuel temperature (about one minute after power stabilisation). Report it in the following table.

4. Comment the results.

Power Critical position (%) Fuel temperature (°C)

10 W

100 W

1 kW

10 kW

100 kW



Rods and Core reactivity measurements

I. Purposea. To establish the calibration curve ofthe regulating rod by the positive period technique,b. To deduce the differential reactivity curve of the regulating rod ( / H verusthe height H

of the rod),c. To establish the calibration curve of the shim rod by the swap technique using the

calibration curve of the regulation rod, and to extrapolate the total worth of the shim rod,d. To establish the total worth of the safety rod by comparison with the worth of the shim rod,e. calculate three control rod reactivities in the reactor,f. To calculate the reactor excess reactivity,g. To calculate the shutdown margin of the reactor.

II. Theoritical Background

Kartini reactor hasthree control rods :

- one safety rod, - one compensating or shim rod- one regulating rod.

The height of the rod is given in % of the maximum height, i.e. when the rod is fully extracted. When moving up the rod into the core the reactivity of the core is increased by the efficiency of the rod corresponding to .

The calibration curve of a rod gives the of the core as a function of the height of the rod H as shown in Figure.1. This curve is used to predict the change in the core reactivity related to the change in the position of the rod.

Figure 1 :Calibration curve, versus H

The differential curve /H versus H can be also established (see figure 2).

Figure 2 : Differential curve, /H versus H.

The region in which the reactivity of the core varies almost linearly with the position of control rod is found in the central part of the core height, typically in the region 20% << 80%.

Due to shadwing effect (the decrease of the neutron density induced by one road will decrease the effectiveness of the other rod), the total worth (maximum ) of the three control rods is generaly less than the sum of the worth of each of the three control rod taken idependantly. Nevertheless, assuming that the shadowing effect is negligible for rods that are far away one from other in the core, it is possible to assume that the total worth of the rod is the sum of the worth of each rod.

Core excess reactivity will be then calculate taking the difference between the total worth of the rod and the worth brought into the core by the three rods when this rods are placed in a critical configuration at low power (10 W for example).

H

/H

H

The shut down margin of the reactor is defined as the total worth of the rods minus the core excess reactivity. It is an important parameter for the safety of the reactor. This shut down margin has to be also calculated with a rod stuck in its upper position, taking the assumption that the rod with the larger worth is stucked.

In order to plot the calibration curve of the reagulating rod by the positive period method, in fact the measurement of the doublig time for the training course, we need to relate the doubling time and the reactivity of the core when it is super-critical.

When the reactor is super-critical, the neutron density increases exponentially (after the prompt jump and a transitory state). According to the reactivity of the core, the speed at which the neutron density is increased can be characterised by the reactor period, i.e. the time taken to increase the power by “e”, e = 2.718.

Experimentally, it is easier to measure the time taken to multiply the power by a factor 1.5 or 2.0. We will measure the doubling time in this training course.

Using the equation of kinetics it is possible to establish a curve called the In-hour curve which relates the reactivity of the core and the doubling time. This curve and a table giving the doubling time for particular values of the reactivity are given in appendix.

III. Equipmenta) PicoammeterKeithleyb) Stopwatchc) Reactivity graph versus time with factor 1.5 or 2.0

IV. Experiment Procedure

Part 1 – Plotting the calibration curve of the Regulating rod – doubling time measurement

1. The reactor is stabilised at low power (10 W) with the Safety rod in position up and Regulating rod in position down. The Shim rod is used for the control of the reactivity.

2. The Compensation Ionisation Chamber CIC is connected to the picoampermeterto record the current.

3. The Regulating control is moved up by a small step. The reactor becomes supercritical. The picoampermeteris used to measure the doubling time.

4. Once the measurement is done, the Shim rod is lowered to reduce the power back to its initial value (10 W) and later on it is moved to find a new critical state with the regulation rod at its previous position.

5. From the doubling time measured in step 3, the reactivity increase due to the extraction of the Regulation rod is determined. This value is reported on a graph as a function of the height of the rod.

6. The steps 3 and 4 up are repeated until the Regulating rod is fully extracted in its upper position.

7. The total worth of the Regulation rod is established.

Part 2 – Plotting the calibration curve of the Shim rod – swap method

1. The reactor is stabilised at low power (10 W) with the Safety rod in position up and Shim rod in position down. The Regulation rod is used for the control of the reactivity.

2. The Compensation Ionisation Chamber CIC is connected to the picoampermeter to record the current.

3. The Shim rod is extracted by a small step maintaining the reactor critical by moving the Regulating rod down to compensate for the change in the core reactivity.

4. The change in the reactivity related to the insertion of the Regulation rod is used to find the change in the reactivity related to the withdrawing of the Shim rod using the calibration curve of the Regulation rod.

5. The value is reported on a graph as a function of the height of the rod.6. Steps 3 to 5 are repeated until the Shim rod is fully extracted. The critical configuration

for the Shim rod at the height 50 % will be searched during this experiment in order to use the results in part 3.

7. Assuming that the core is symmetrical on the vertical axis, established the total worth of the Shim rod.

Part 3 – Establishment of the total worth of the Safety rod – related to the worth of the Shim rod

1. The reactor is started up with the Shim rod fully extracted (used as the Safety rod), the Safety rod being place at the height 50 %. The Regulation rod is used to increase and stabilize the power at 10W.

2. By comparing the critical configuration obtained in this condition to the on established in Part 2 with the Shim rod at 50 % and the Safety rod fully extracted, the total worth of the Safety rod will be estimated (making the assumption that the core is symmetric on the vertical axis).

Part 4 – Determination of the core reactivity

From the previous results calculate:

1. The total reactivity of the three control rods (assuming that there is no shadow effect)2. The excess reactivity of the core3. The shutdown margin of the core4. The shutdown margin of the core with one rod stuck (with the largest worth)


Protocol N° 5 – Kartini Reactor

Temperature Coefficient of the fuel

I. Purpose

To determine the amount of reactivity changes caused by each degree change in temperature reactor fuel.


Temperature change has a significant influence on the disruption of reactivity during reactor operation.These changes can be caused by changes in coolant flow rate, or by changes in the rate of heat removal, such as the changing needs of power and so on. In general the temperature reactivity coefficient is written as :

(1)

Under the condition:

= core reaktivity

T = Fuel element temperature

T = temperature reaktivity.

Therefore, the reactivity of the reactor depends on several parameters such as f, p, L 2, etc, where the values depends on the temperature of reactor components such as fuel, coolant, moderat and so on, then the reactor temperature changes will cause changes in reactivity. From the definition of reactivity is written as:

(2)

Then the temperature reactivity can be rewritten as:

for k = 1 can be written as : (3)

Due to k (effective multiplication factor) always has a positive value then Talways have same

sign . Positive or negative sign of this temperature reactivity coefficient dtermines the

properties of reactor stability.In Figure 1 below illustrates how the effect of temperature coefficient of reactivity to changes in power (which means also changes in temperature) due to positive reactivity insertion (withdrawal of control rods) of a reactor.

TemperatureT> 0

T ~ 0

T<< 0

Time

Gambar 1. The temperature of the reactor as function of time on the addition of positive reactivity

For ease of control, ussually the reactor is designed to have a negative temperature coefficient of reactivity. Temperature reactivity coefficient is determined by each parameter forming an effective neutron multiplication factors, namely:

or

(4)

Equation (4) is known as the temperature coefficient of the overall determinants of neutron multiplication factor.

It can be proved that T(p) is associated with a temperature moderator material which also means fuel temperature.

So by observing changes in fuel element temperature and reactor reactivity changes (change of control rod position) that operates on fixed power, can be determinedTof reactor fuel.

III. Equipment1. Instrumented fuel element (IFE)2. MicroamperemeterKeithley to read the fuel temperature.3. Instrumentation and Control System of the reactor

IV. Experiment Procedure

1. Place the IFE on the position ring B, connect the output of the IFE with Microameter2. Operate the reactor at a certain power level, for example, 100 kW with the

condition of primary coolant pump system on. For 10 minutes.3. The coolinbg sytem is turned off.

4. Observe the temeprature rise IFE and regulating rod position every 5 minutes or 10 minutes.

Time (mn) Power (kW) Fuel temperature (°C)

0

5

10

15

20

25

30

5. Take data at the item (3) within a period of approximately 30 minutes. Then turn on the primary cooling system, observe the IFE temperature changes andchanges in the position of regulating rod.

6. With the help of regulating control rod calibaration data, calculate equation (1) and using the linear regression equation to the data from step (3) and the data from step (4).



Reactivity measurements (graphite, fuel, devices)

V. Purpose

Measure and study the change in the reactivity of the core due to the removal or the insertion of different elements in the core:

- Removal of a graphite element in position XX- Insertion of a massive aluminium element in position XX- Successive unloading of 4 fuel elements in positions XX (each time the element is

reloaded before the next fuel element is unloaded)

VI. Theoretical Background

Any change in the configuration of the core will have an impact on the reactivity of the core.

Any device removed from the core will result in the replacement of its volume by the same volume of water. Water is a moderator.

Graphite is a good moderator with a capture cross section 100 times less than water. It can be used as a reflector for the neutrons.

Alimunium can be assumed as transparent to neutrons.

The worth in reactivity of a device doesn’t depend only on its caracteristics but also on the characteristics of the surrounding devices that will define the neutron density at the device’s location. The worth in reactivity of a device increases with the neutron density at its location.

VII.Equipment

- Calibration curve of the Regulating rod

VIII. Experiment procedure

Part 1–Influence of a graphite element

1. The reactor is in a critical condition at a power of 10W.The critical position of the Regulating rod HC1 is recorded.

2. The reactor is made sub-critical and the graphite element in position F14 is withdrawn from the core.

3. The reactor is brought critical at a power of 10W. The critical position of the Regulating rod HC2 is recorded.

4. From the difference between HC2 and HC1, determine the worth of the graphite element using the calibration curve of the Regulating rod (be carreful that the movement of the rod is compensating the change in the reactivity of the core due to the removal of the graphite element).

5. How do you explain the influence of the removal of the graphite element on the core reactivity ?

Part 2 – Influence of a aluminum element

6. The reactor is critical at a power of 10W, the Regulating rod being at the position HC2.7. The reactor is made sub-critical and the aluminum element in inserted in position F14.8. The reactor is brought critical at a power of 10W. The critical position of the Regulating

rod HC3 is recorded.9. From the difference between HC3 and HC2, determine the worth of the aluminum

element using the calibration curve of the Regulating rod (be carreful that the movement of the rod is compensating the change in the reactivity of the core due to the removal of the graphite element).

10. How do you explain the influence of the insertion of the aluminum element on the core reactivity ?

At the end of these experiment :

11. The reactor is made sub-critical.12. The aluminum element is removed from the core and replaced by the graphite element.

The reactor is back to the initial condition of step 1 with the Regulating rod at position HC1.

Part 3 – Worth of the fuel element according to their position

13. The reactor is critical at a power of 10W, the Regulating rod being at the position HC1.14. The reactor is made sub-critical and the fuel element on ring Fin position F13 is

unloaded.

15. The reactor is brought critical at a power of 10W. The critical position of the Regulating rod HC-F is recorded.

16. The reactor is made sub-critical en the fuel element is reloaded in its initiale position.17. The fuel element on ring E in position E11 is unloaded.18. The reactor is brought critical at a power of 10W. The critical position of the Regulating

rod HC-E is recorded.19. The reactor is made sub-critical en the fuel element is reloaded in its initiale position.20. The fuel element on ring D in position D08 is unloaded.21. The reactor is brought critical at a power of 10W. The critical position of the Regulating

rod HC-D is recorded.22. The reactor is made sub-critical en the fuel element is reloaded in its initiale position.23. The fuel element on ring C in position C06 is unloaded.24. The reactor is brought critical at a power of 10W. The critical position of the Regulating

rod HC-C is recorded.25. The reactor is made sub-critical en the fuel element is reloaded in its initiale position

and the reactor is shut down.26. Using the recorded critical positions for the Regulating rod, determine the worth of each fuel

element filling the following table.

Core state Critical position of the Reg. Rod

(%)

Worth of the element($)

All fuel element in place HC1 =

Element in ring E unloaded HC-F =

Element in ring D unloaded HC-E =

Element in ring C unloaded HC-D =

Element in ring B unloaded HC-C =

27. Comment the results of this experiment.



Reactor Power Calibration

I. Purpose

Perform calibration power reactor, which is looking for actual power generated in the reactor core comparing to the indicated power meter.


Reactor power generated by the energy released from fission reactions that occur in the reactor. The number of fission reactions that occur per second per unit reactor volume is determined byf.

If the number of fission reactions per second that need to generate a power of 1 watt is 3.2 x 1010 fissions, then the total power P of the reactor is given by the equation:

f = macroscopic fission cross-sections

Vf = volume of reactor.

So by measuring the neutron flux in core, the reactor power can be determined. Another method is using calorimeter method that can be done in 2 ways:

Method 1 - Reactor operated with the cooling system not in operation – cooling system Off

Method 2 - Reactor operated with cooling system is operation – cooling system On

In Method 1, when the cooling system is off, i.e. method of non-stationary, the heat generated by the reactor core reactors accumulate in the tank, so the water temperature in the reactor will rise. The maximum limit of the temperature allowed for the water tank at KARTINI reactor is 40 °C. The rate of temperature rise in the water tank, at a fixed power level, can be used to

determine the actual power of the reactor. The power of the reactor is expressed by the following equation:

Equation (1)

with P = real reactor power, in kW,

Q = heat that is formed in the reactor,

H = water value of KARTINI reactor = 19.0476 kWh / °C,

T = temperature of the water tank reactor in °C,

t = observation time interval, in hours.

In Method 2, when the cooling system is on, i.e. stationary method, the heat produced in the reactor tank is taken by the primary cooling system. Then, through a heat exchanger (HE), heat is transferred to a secondary coolant system. The coolant flow rate being constant, we obtain stationary conditions. In the stationary condition, the heat transferred from the reactor core depends on water discharge (G) and different inlet and outlet temperature of the primary coolant system. Reactor power is determined mathematically by the following equation:

P = 0.06 x G . c . TEquation (2)

With G = primary cooling water discharge system, in litre/min,

c = specific heat of water c = 4.187 W.s/g.°C,

T = the difference in temperature between the HE inlet and outlet, in °C.

At reactor console, the reactor power can be read using either:

- the linear power channel (% power) associated with the Compensated Ionisation Chamber (CIC) detector in reactor

- the logarithmic power channel (power) associated with the Fission Chamber (FC) detector in the reactor.

If the linear power channel (% power) meter indicates a value different from the one given by the power calibration by Method 1, it is necessary to calibrate the linear channel (% power) as well as the logarithmic channel.

III. Equipment

1. Thermometer 20 oC - 100 oC

2. Stopwatch

3. Small bucket to fetch water from reactor tank.

IV. Experiment Procedures

Method 1 – Cooling system Off

1. Reactor is operated in critical without reactor coolant system running.

2. Raise the reactor power to a constant level of power of 100 kW.

3. Observe during one hour the water temperature increase in the reactor tank. Record the temperature value every 5 minutes in the following table.

Time (mn) Temperature (°C)

0

5

10

15

20

25

30

35

40

45

50

55

60

4. Plot the graph of the temperatures versus time.

5. Calculate the slope of the curve.

6. From the value of the slope determine the actual power of the reactor using Equation (1).

7. Compare the value obtained to the power indicated by the linear power meter.

Method 2 – Cooling system On

8. The primary and secondary cooling systems are turned On.

9. Record and write in the following table the temperature of the water tank, of the HE inlet and of the HE outlet of the primary cooling system, every 10 minutes until the tank water temperature constant (stationary).

Time (mn) Tank Temperature

(°C)

HE inlet temperature

(°C)

HE outlettemperature(°

C)

0

10

20

30

40

50

60

10. Once the stationary state is obtained, use the Equation (2) to calculate the actual power reactor.

11. Compare the value obtained to the value obtained by Method 1 and to the power indicated by the linear power meter. Comment the results.

Documents

Schedule and Nuclear School Experiment