BARC/2014/E/014B

AR

C/2014/E

/014

ESTIMATION OF TEMPERATURE PATTERN IN THE LATTICE LOCATIONADJACENT TO A CALANDRIA TUBE ROLLED JOINT DURING ITS

DETACHMENT BY SHOCK HEATING

byS. Chatterjee and K. Madhusoodanan

Reactor Engineering Division

BARC/2014/E/014

GOVERNMENT OF INDIAATOMIC ENERGY COMMISSION

BHABHA ATOMIC RESEARCH CENTREMUMBAI, INDIA

2014

BA

RC

/201

4/E

/014

ESTIMATION OF TEMPERATURE PATTERN IN THE LATTICE LOCATIONADJACENT TO A CALANDRIA TUBE ROLLED JOINT DURING ITS

DETACHMENT BY SHOCK HEATING

byS. Chatterjee and K. Madhusoodanan

Reactor Engineering Division

BIBLIOGRAPHIC DESCRIPTION SHEET FOR TECHNICAL REPORT(as per IS : 9400 - 1980)

01 Security classification : Unclassified

02 Distribution : External

03 Report status : New

04 Series : BARC External

05 Report type : Technical Report

06 Report No. : BARC/2014/E/014

07 Part No. or Volume No. :

08 Contract No. :

10 Title and subtitle : Estimation of temperature pattern in the lattice location adjacent to acalandria tube rolled joint during its detachment by shock heating

11 Collation : 26 p., 38 figs., 6 tabs.

13 Project No. :

20 Personal author(s) : S. Chatterjee; K. Madhusoodanan

21 Affiliation of author(s) : Reactor Engineering Division, Bhabha Atomic Research Centre, Mumbai

22 Corporate author(s) : Bhabha Atomic Research Centre, Mumbai - 400 085

23 Originating unit : Reactor Engineering Division, Bhabha Atomic Research Centre, Mumbai

24 Sponsor(s) Name : Department of Atomic Energy

Type : Government

Contd...

BARC/2014/E/014

BARC/2014/E/014

30 Date of submission : November 2014

31 Publication/Issue date : December 2014

40 Publisher/Distributor : Head, Scientific Information Resource Division, Bhabha Atomic Research Centre, Mumbai

42 Form of distribution : Hard copy

50 Language of text : English

51 Language of summary : English, Hindi

52 No. of references : 4 refs.

53 Gives data on :

60

70 Keywords/Descriptors : PHWR TYPE REACTORS; PRESSURE TUBES; SHOCK HEATING; REACTOR OPERATION; ROLLING; FINITE ELEMENT METHOD; COOLANT LOOPS; ZIRCONIUM ALLOYS

71 INIS Subject Category : S21

99 Supplementary elements :

Abstract : In Pressurised Heavy Water Reactors, the coolant channel assembly, carrying the fuelbundles consists of a pressure tube, surrounded by a concentric calandria tube. Calandria tube isjoined at its ends to calandria side tubesheets through sandwich type rolled joints. During reactoroperation, there is a gradual increase in the sag of the coolant channel assembly due to irradiationcreep and growth. As the life of the pressure tube is limited due to degradation issues, there is aneed to replace it multiple times during the licensing period of the reactor. However, excessivesag of the calandria tube makes the installation of a new straight pressure tube very difficult,necessitating replacement of the calandria tube also. Hence a system is being developed inReactor Engineering Division to detach the calandria tube from its rolled joints with an intentionto reroll a new calandria tube with minimum refurbishment of the tubesheet rolling area. Themethod adopted for removal of calandria tube is induction based shock heating and cooling of therolled joint area, followed by application of pulling load on the calandria tube. As the rolled jointdetachment process involves multiple heating and cooling cycles, due to conduction, the temperatureof the tubesheet at adjacent lattice position will increase. The increase in temperature at adjacentlattice position needs to be limited for protection of the calandria tube rolled joints located there.Considering this, the temperature distribution of tubesheet during induction heating has beenestimated by carrying out a 2-D finite element thermal analysis. In this report the model preparation,its validation and results have been discussed in detail. It also highlights the effects of differentparameters involved in the heating process on the temperature of tubesheet at the adjacentlattice location

i

सार

दाबित भारी पानी ररएक् टरं के कूलनै ्ट चैनल असेम ्िली मं ईंधन िडंल रहत े हं। इस असेम ्िली की दाि नललका, सकेंन्द्रित कैलेन्द्रिया ट्यिू से लिरी रहती है । कैलेन्द्रिया ट्यिू, अपने छोरं पर सडंबिच प्ररूपी रोल ्ड जोडं के माध ्यम से कैलेन्द्रिया साइड ट्यिू शीटं से जुडे़ रहत े हं। ररएक् टर प्रचालन के दौरान, ककरणन के फैलने और िढ़न ेके कारण, कूलनै ्ट चैनल असेम ्िली के सगै मं धीरे-धीरे िबृि होती है । चूंकक दाि नललका का जीिन डीग्रेडेशन के कारण सीलमत होता है इसललए ररएक् टर की लाइससं अिलध के दौरान, दाि नललका को अनेकं िार िदलने की जरुरत होती है । यद्यबप, कैलेन्द्रिया ट्यिू के अत ्यलधक सगै के कारण, नई सीधी दाि नललका को स ्थाबपत करना िहुत मनु्द्ककल होता है न्द्जस कारण से कैलेन्द्रिया ट्यिू को भी िदलना आिश ्यक हो जाता है । इसललए, ररएक् टर इंजीलनयरी प्रभाग मं एक ऐसे ततं्र का बिकास ककया जा रहा है ताकक कैलेन्द्रिया ट्यिू को इसके रोल ्ड जोड़ं से अलग ककया जा सके न्द्जसस ेकक ट्यिू शीट रोललगं एररया का कम से कम पनुससज ्जा करके एक नई कैलेन्द्रिया ट्यिू को कफर से रोल ककया जा सके । कैलेन्द्रिया ट्यिू को हटान ेके ललए अपनाई गई बिलध मं प्रेरण आधाररत शॉक हीकटंग तथा रोल ्ड जॉइंट एररया की कूललगं के िाद कैलेन्द्रिया ट्यिू पर पलुलगं लोड का अनपु्रयोग करना शालमल है । चूंकक रोल ्ड जॉइंट कडटैचमेन ्ट प्रकिया मं मन्द्टटपल टीकटंग और कूललगं साइकल शालमल है इसललए चालन के कारण, समीपिती लकैटस पोन्द्जशन पर ट्यिू शीट के तापमान मं िबृि होगी । िहां न्द्थथत कैलने्द्रिया ट्यिू रोल ्ड जॉइंट के िचाि के ललए, समीपिती लकैटस पोन्द्जशन के तापमान मं िढ़ोत ्तरी को सीलमत रखना जरूरी है । इसको ध ्यान मं रखत े हुए, प्ररेण तापन के दौरान ट्यिू शीट के तापमान बितरण का आकलन, 2- डी तापीय FEM बिश ्लेषण करके ककया गया है। इस ररपोटस मं, मॉडल की तयैारी, इसका मान ्यकरण और पररणामं की चचास बिस ्तारपिूसक की गई है । समीपिती लकैटस लोकेशन पर ट्यिू शीट के तापमान पर तापन प्रकिया मं शालमल बिलभन ्न परैामीटरं के प्रभािं को भी यह उजागर करता है ।

ii

Abstract

In Pressurised Heavy Water Reactors, the coolant channel assembly, carrying the fuel

bundles consists of a pressure tube, surrounded by a concentric calandria tube. Calandria tube

is joined at its ends to calandria side tubesheets through sandwich type rolled joints. During

reactor operation, there is a gradual increase in the sag of the coolant channel assembly due to

irradiation creep and growth. As the life of the pressure tube is limited due to degradation

issues, there is a need to replace it multiple times during the licensing period of the reactor.

However, excessive sag of the calandria tube makes the installation of a new straight pressure

tube very difficult, necessitating replacement of the calandria tube also. Hence a system is

being developed in Reactor Engineering Division to detach the calandria tube from its rolled

joints with an intention to reroll a new calandria tube with minimum refurbishment of the

tubesheet rolling area. The method adopted for removal of calandria tube is induction based

shock heating and cooling of the rolled joint area, followed by application of pulling load on

the calandria tube. As the rolled joint detachment process involves multiple heating and

cooling cycles, due to conduction, the temperature of the tubesheet at adjacent lattice position

will increase. The increase in temperature at adjacent lattice position needs to be limited for

protection of the calandria tube rolled joints located there. Considering this, the temperature

distribution of tubesheet during induction heating has been estimated by carrying out a 2-D

finite element thermal analysis. In this report the model preparation, its validation and results

have been discussed in detail. It also highlights the effects of different parameters involved in

the heating process on the temperature of tubesheet at the adjacent lattice location.

iii

CONTENTS

1.0 Introduction 1

2.0 Description of problem 1

2.1 Geometry modelling 2

2.2 Material properties 2

2.3 Loading 3

3.0 Mesh generation 4

4.0 Validation of model 5

5.0 Results and discussion 6

5.1 Parametric study 8

5.1.1 Heat generation method 8

5.1.1.1 Effect of heat transfer coefficient 8

5.1.1.2 Effect of heat generation period 9

5.1.1.3 Effect of time gap between heat generation cycles 11

5.1.2 Cyclic temperature control method 11

5.1.2.1 Effect of heat transfer coefficient 11

5.1.2.2 Effect of calandria tube temperature 12

5.1.2.3 Effect of duration of peak temperature 13

5.1.3 3-D analyses 14

6.0 Conclusions 17

Acknowledgements 17

Nomenclatures 17

References 17

iv

List of Figures

Figure-1 : Rolled joint detachment system for calandria tube-to-tubesheet rolled joint

Figure-2 : Geometry Modeling

Figure-3 : Enlarged view of calandria Tube

Figure-4 : Typical Heat Generation cycle

Figure-5 : Typical Temperature Control Cycle

Figure-6 : Meshed model

Figure-7 : Enlarged view of the meshed model showing calandria tube

Figure-8 : Tubesheet sleeve

Figure-9 : Experimentally observed temperature profile of tubesheet sleeve at OD and

near to ID

Figure-10 : Analytical estimation of temperature at half pitch distance of tubesheet sleeve

Figure-11 : Estimated temperature at points A, B and C with cyclic heat generation

method

Figure-12 : Temperature distribution of tubesheet during maximum pitch circle

temperature

Figure-13 : Temperature distribution along the pitch circle of the tubesheet in heat

generation method

Figure-14 : Temperature distribution of tubesheet showing when point C attains the

maximum value

Figure-15 : Variation of temperature of point C of tubesheet with time

Figure-16 : Temperature profile at points 'A', 'B' and 'C' in cyclic temperature control

method

Figure-17 : Temperature distribution along the pitch circle of the tubesheet in cyclic

temperature control method

Figure-18 : Temperature at calandria tube ID (point A) with varying heat transfer

coefficient (h)

Figure-19 : Temperature profile at half pitch distance (point B) with varying heat transfer

coefficient (h)

v

Figure-20 : Temperature profile at end shield tubesheet adjacent lattice location (point C)

with varying heat transfer coefficient (h)

Figure-21 : Variation of temperature profile of calandria tube ID (point A) with heat

generation time

Figure-22 : Variation of temperature profile at point B of end shield tubesheet with heat

generation time

Figure-23 : Variation of temperature profile at point C of end shield tubesheet adjacent

lattice location with heat generation time

Figure-24 : Variation of temperature profile of point B at half pitch distance of tubesheet

with time gap between heat generation cycles

Figure-25 : Variation of temperature profile of point 'C' at adjacent lattice location with

time gap between heat generation cycles

Figure-26 : Variation of temperature profile of point A with heat transfer coefficient

Figure-27 : Variation of temperature profile of point B with heat transfer coefficient

Figure-28 : Variation of temperature profile of point C with heat transfer coefficient

Figure-29 : Variation of temperature distribution profile of point B of tubesheet with

calandria tube temperature

Figure-30 : Variation of temperature distribution profile of point C of tubesheet with

calandria tube temperature

Figure-31 : Variation of temperature profile of point B with varying period of calandria

tube peak temperature

Figure-32 : variation of temperature profile of point C with varying period of calandria

tube peak temperature

Figure-33 : Meshed 3D geometry

Figure-34 : Temperature contour of the model at the end of heat generation

Figure-35 : Heat generation cycles and temperature at point A

Figure-36 : Estimation of temperature profile of points B and C in 3-D analysis in heat

generation method

Figure-37 : Temperature contour of the model at the end of temperature cycles

Figure-38 : Estimation of temperature profile of points B and C in 3-D analysis in cyclic

temperature method

1

Estimation of temperature pattern in the lattice location adjacent to a

calandria tube rolled joint during its detachment by shock heating

S. Chatterjee* and K. Madhusoodanan

Reactor Engineering Division,

Bhabha Atomic Research Centre,

Trombay, Mumbai 400085.

*email: subrata@barc.gov.in

1.0 Introduction

In Pressurized Heavy Water Reactor (PHWRs) fuel bundles are located inside Zr-2.5Nb pressure

tubes through which high pressure, high temperature heavy water coolant flows. Pressure tubes are

surrounded by concentric zircaloy-2 calandria tubes. Calandria tubes, arranged in a 229 mm square

lattice pitch are joined at both ends to the end shield tubesheets through sandwich type rolled joints.

Pressure tubes undergo creep and growth during service, leading to increase in diameter and sag,

necessitating its replacement in 12-15 years of operation. The weight of pressure tube, coolant and

fuel bundle is partially transmitted to the calandria tube through garter springs. After a long period of

operation under radiation environment, the calandria tubes also undergo sag. The sagged calandria

tube will restrict the entry of a straight new pressure tube during the replacement programme. Under

these circumstances, along with the pressure tube, the calandria tube will also needs to be replaced.

A system based on induction based shock heating technique is being developed to detach the sagged

calandria tube from its rolled joints with the end shield tubesheets as shown in Fig. 1 [1-4]. In this

technique, fast heating of the insert and calandria tube followed by sudden cooling facilitates the

detachment from the rolled joint. As the rolled joint detachment process involves multiple heating and

cooling cycles, due to conduction, the temperature of the tubesheet at adjacent lattice position will

increase. The increase in temperature at adjacent lattice position needs to be limited for protection of

the calandria tube rolled joints located there. Considering this, the temperature distribution of

tubesheet during induction heating has been estimated by carrying out a 2-D finite element thermal

analysis. In this report, the model preparation, its validation and results have been discussed in detail.

It also highlights the effects of parameters like heat transfer coefficient (h), period of heat generation

(tq), gap between heat generation (tg), calandria tube temperature (TCT), period of temperature cycle

(theating cycle), period of fixed temperature (tFT) etc. on temperature of end shield tubesheet ID at adjacent

lattice position.

Fig. 1: Rolled joint detachment system for calandria tube-to-tubesheet rolled joint

2

2.0 Description of problem

In PHWR, the removal of calandria tube from the core is envisaged by detaching it from the rolled

joints at both ends by shock heating and cooling technique. However, during multiple shock heating

cycles, the temperature of tubesheet will gradually increase, which can affect the performance of

adjacent rolled joints. As per requirements, the maximum temperature of calandria tube rolled joint

needs to be limited to 80 oC. In order to estimate the temperature pattern, a 2D finite element model

has been prepared and thermal analyses have been carried out. In this problem, temperature

distribution is analyzed using two modes of heat transfer, i.e. conduction and convection. Heat is

supplied to the calandria tube either by cyclic heat generation or by cyclic temperature control curve.

Different heat loading cycle has been applied in both the methods and effects of different parameters

have been analyzed.

2.1 Geometry modeling

Since the geometry is symmetrical about x and y axes, a rectangular section has been selected from

one quadrant. Figure 2 shows the geometry of the model. The areas shown in blue and green colours

represent the end shield tubesheet material and the area in red colour represents calandria tube. Figure

3 shows the enlarged view of the geometry at calandria tube location. Dimensions of the geometry are

given in Table 1.

Points A, B and C in Fig. 2 represent calandria tube ID, half the pitch length (p/2) and adjacent end

shield tubesheet ID respectively.

Fig. 2: Geometry Modeling Fig. 3: Enlarged view of calandria Tube

Table 1: Dimensions of calandria tube

Sr. No. Parameters of CT Dimension (mm)

1 Outside diameter (OD) 119.5

2 Pitch (p) 229

3 Thickness 1.2

Calandria Tube

p

p/2 End Shield Tubesheet

A

B

C

3

2.2 Material properties

Calandria tube is made of zircaloy-2 alloy and the end shield tubesheet is made of SS 304L. The

thermal conductivities of these materials are assumed to be constant as the thickness of calandria tube

is very small and the temperature of end shield tubesheet does not exceed 150 oC. Table 2 shows the

properties of materials considered in the finite element analyses.

Table 2: Material Properties

Sr. No. Parameters Zircaloy-2 SS 304L

1 Density 6560 kg/m3 7900 kg/m

3

2 Heat capacity 285 J/kg-K 500 J/kg-K

3 Thermal

conductivity

21.4 W/m-K 16.2 W/m-K

2.3 Loading

As the geometry is symmetric about x and y axes, these two axes are assumed to be adiabatic. The

heat generation in calandria tube due to induction heating is simulated by two methods mentioned

below:

1. Defined cyclic heat generation in calandria tube

2. Defined temperature cycle in calandria tube

In the first method, cyclic heat generation in calandria tube is carried out in four consecutive cycles as

described in Fig. 4. The effects of different parameters like heat transfer coefficient (h), heat

generation cycle gap (tg) and the period of heat generation (tq) on temperature distribution have been

studied.

Fig. 4: Typical Heat Generation cycle.

tq

tg

theating cycle

4

Similarly in temperature control method, cyclic temperature distribution is applied to the calandria

tube in four successive cycles as shown in Fig. 5. The effects of heat transfer coefficient (h), calandria

tube temperature (TCT), period of temperature distribution cycle (theating cycle), and period of fixed

temperature (tFT) on temperature distribution of tubesheet have been studied.

Fig. 5: Typical Temperature Control Cycle.

During all the analyses the initial temperature of the calandria tube and end shield tubesheet has been

assumed to be 30 °C.

3.0 Mesh generation

Meshing of the geometry has been done using four nodded quadrilateral elements. Area of end shield

tubesheet has been free meshed using finest possible element size and area of calandria tube has been

mapped meshed. Figure 6 shows the meshed model of the entire geometry considered for the analyses

and Fig. 7 gives an enlarged view of the meshed model showing calandria tube.

tg tFT

theating cycle

5

Fig. 6: Meshed model Fig. 7: Enlarged view of the meshed model

showing calandria tube

4.0 Validation of model

Figure 8 shows the end shield tubesheet sleeve after an experimental trial for detachment of the rolled

joint. The half pitch distance (p/2) is shown in Fig. 8. During the detachment trials, temperature was

recorded at two locations of the sleeve using K type thermocouples. Temperature profiles recorded at

half pitch distance or at pitch circle, which is at its outside diameter (OD), and near to tubesheet inside

diameter (ID) are shown in Fig. 9.

Fig. 8: Tubesheet sleeve Fig. 9: Experimentally observed temperature profile of

tubesheet sleeve at OD and near to ID

Fig.10 shows the FEM estimated temperature profile of the end shield tubesheet at half pitch distance.

It can be observed that the temperature profile obtained from the finite element analysis is similar to

that from the experimental trial. Moreover the purpose of this analytical work is to estimate the

temperature of the adjacent lattice ID of end shield tubesheet when the peak temperature at half pitch

distance follows the experimentally observed peak temperature at same location.

p/2

6

Fig. 10: Analytical estimation of temperature at half pitch distance of tubesheet sleeve.

5.0 Results and discussion

The analyses have been carried out by defining cyclic heat generation in the calandria tube and cyclic

temperature control methods as described earlier. In heat generation method, four consecutive cycles

of heat at a rate of 4.7×106 kJ/m

3/s for 10 s is applied to the area representing the calandria tube. With

this mode of analysis, temperature at half pitch distance (p/2) from the centre of calandria tube has

been estimated to be about 114 oC and temperature at the ID of adjacent lattice location in end shield

tubesheet has been estimated to be about 78 oC. The estimated temperature with cyclic heat generation

at points A, B and C as described in Fig. 2 is plotted in Fig. 11.

Fig. 11: Estimated temperature at points A, B and C with cyclic heat generation method.

The temperature distribution of the tubesheet shown in Fig.12 is plotted when the temperature at half

pitch distance reaches the maximum value. Figure13 shows the temperature pattern along the pitch

circle. It can be observed from Fig. 13 that temperature remains the same at pitch circle. X and Y axes

represent the coordinates of pitch circle.

7

Fig. 12: Temperature distribution of tubesheet

during maximum pitch circle temperature

Fig. 13: Temperature distribution along the pitch

circle of the tubesheet in heat generation method

Maximum temperature of end shield tubesheet sleeve at adjacent lattice location (point C) has been

estimated to be 78 oC. Figure 14 shows the pattern of temperature distribution when maximum

temperature is observed at point C. Figure 15 shows the variation of temperature of point C of

tubesheet with time.

Fig. 14: Temperature distribution of tubesheet

showing when point C attains the maximum value

Fig. 15: Variation of temperature of point C of

tubesheet with time

In cyclic temperature control method, four consecutive cycles of temperature are applied to calandria

tube as illustrated in Fig. 5. The peak value of temperature applied to calandria tube is fixed at 830 oC

for 10 s. In this method, the maximum temperature at point C and B has been observed as 70 oC and

117 oC respectively. Figure16 shows the temperature distribution profile of points 'A', 'B' and 'C' and

Fig.17 shows the temperature profile at pitch circle when it reaches the maximum value. The

temperature has been found out to be constant along the pitch circle.

8

Fig. 16: Temperature profile at points 'A', 'B'

and 'C' in cyclic temperature control method Fig. 17: Temperature distribution along the

pitch circle of the tubesheet in cyclic

temperature control method

5.1 Parametric study

Certain parameters affect the temperature profile at the adjacent lattice location (point C) of the end

shield tubesheet.

1. Parameters studied in cyclic heat generation

Heat transfer coefficient (h),

Period of heat generation (tq),

Gap between heat generation (tg)

2. Parameters studied in cyclic temperature control

Heat transfer coefficient (h),

Calandria tube temperature (TCT),

Period of fixed temperature (tFT)

5.1.1 Heat generation method

5.1.1.1 Effect of heat transfer coefficient

Different values of heat transfer coefficients such as 1, 2, 5 and 10 W/m2.K have been considered and

their effect have been studied on the estimation of temperature at point C. The effects of heat transfer

coefficient have been found to be negligible in all the cases as shown in Figs. 18-20. Figure 18, Fig.19

and Fig.20 show the effects of heat transfer coefficient at points 'A', ‘B’ and ‘C’ respectively.

9

Fig. 18: Temperature at calandria tube ID (point A) with varying heat transfer coefficient (h)

Fig. 19: Temperature profile at half pitch distance

(point B) with varying heat transfer coefficient (h)

Fig. 20: Temperature profile at end shield

tubesheet adjacent lattice location (point C) with

varying heat transfer coefficient (h)

From the above study in which the heat transfer coefficients have been varied, no significant change

in the temperature profile of points A, B and C has been observed. In natural convection, the heat

transfer coefficient generally varies from 2 to 5 W/m2.K. For the sake of conservative analysis, the

minimum and maximum values of heat transfer coefficients considered in these parametric analyses

are 1 W/m2.K and 10 W/m

2.K respectively.

5.1.1.2 Effect of heat generation period

The effects of period of heat generation on the temperature profile of points A, B and C have been

studied by considering three different time periods such as 10 s, 12 s and 15 s. Considerable amount

of deviation in temperature profile of the calandria tube and the end shield tubesheet adjacent lattice

location has been observed. Figures 21, 22 and 23 show the temperature profile at points A, B and C

respectively.

10

Fig. 21: Variation of temperature profile of calandria tube ID

(point A) with heat generation time.

Fig. 22: Variation of temperature profile at point

B of end shield tubesheet with heat generation

time.

Fig. 23: Variation of temperature profile at point

C of end shield tubesheet adjacent lattice location

with heat generation time.

It has been observed that the temperature at all locations of tubesheet increases with increase in heat

generation time. Table 3 shows the maximum temperature obtained at points A, B and C for different

time period of heat generation.

Table 3: Maximum Temperature at different locations for different period of heat generation

Sr. No. Location tq=10 s tq = 12 s tq = 15 s

1 A 830.82 oC 848.66

oC 873.36

oC

2 B 114.14 oC 119.66

oC 130.96

oC

3 C 78.87 oC 82.14

oC 88.85

oC

It can be observed from the above table that the temperature of end shield tubesheet adjacent lattice

location (point C) is below 80 oC for heat generation period (tq) of 10 s. Therefore this period of heat

generation (tq) has been selected for further studies.

11

5.1.1.3 Effect of time gap between heat generation cycles

The time gap between two successive heat generation cycles has significant effect on peak

temperature of end shield tubesheet adjacent lattice location. In order to understand the effect,

analyses have been carried out with three different time gaps (tg) such as 30 s, 45 s and 60 s.

Maximum rise in temperature is observed when the time gap is minimum, i.e. 30 s. Figure 24 and Fig.

25 show the temperature profile of points B and C respectively.

Fig. 24: Variation of temperature profile of point

B at half pitch distance of tubesheet with time gap

between heat generation cycles.

Fig. 25: Variation of temperature profile of point

'C' at adjacent lattice location with time gap

between heat generation cycles.

Table 4 shows the maximum temperature observed at points A, B and C for different time gap

between heat generation cycles (tg).

Table 4: Maximum temperature at different locations for different time gap between heat generation

cycles

Sr. No. Location tg = 30 s tg = 45 s tg = 60 s

1 A 875.40 oC 830.82

oC 739.70

oC

2 B 113.10 oC 114.14

oC 107.80

oC

3 C 78.11oC 78.87

oC 75.80

oC

It can be observed from the experimental trial that the temperature of calandria tube generally reaches

around 830 oC. Hence, the time gap of 45 s between two successive heating cycles is most

appropriate.

5.1.2 Cyclic temperature control method

5.1.2.1 Effect of heat transfer coefficient

In order to study the effect of heat transfer coefficient (h) in cyclic temperature control method on the

temperature profile of tubesheet, different values like 1, 2, 5 and 10 W/m2.K have been considered in

the analyses. The effects of heat transfer coefficient on the temperature profile of tubesheet have been

found to be negligible. Figures 26-28 show the effects of heat transfer coefficient at points A, B and C

respectively.

12

Fig. 26: Variation of temperature profile of point A with heat transfer coefficient.

In order to maintain the clarity of the above plot, the temperature profile is shown till 500 s only,

though the study has been carried out up to 1000 s.

Fig. 27: Variation of temperature profile of point

B with heat transfer coefficient.

Fig. 28: Variation of temperature profile of point

C with heat transfer coefficient.

5.1.2.2 Effect of calandria tube temperature

The effect of calandria tube temperature on end shield tubesheet has been studied by considering three

different peak temperatures such as 800 oC, 830

oC and 900

oC in cyclic temperature control method

and its effects on the temperature of points B and C have been plotted in Fig. 29 and Fig. 30

respectively. Inspite of considering the peak temperature of calandria tube as 900 oC, the temperature

at adjacent lattice ID (point C) of end shield tubesheet has not crossed 80 oC.

13

Fig. 29: Variation of temperature distribution

profile of point B of tubesheet with calandria tube

temperature.

Fig. 30: Variation of temperature distribution

profile of point C of tubesheet with calandria tube

temperature.

Table 5 shows the maximum temperatures observed at different locations, point A, B and C for

different calandria tube peak temperature.

Table 5: Maximum temperature at different locations for different calandria tube peak temperature

Sr. No. Location TCT = 800 OC TCT = 830

OC TCT = 900

OC

1 A 800 O

C 830 O

C 900 O

C

2 B 114.94 O

C 117.85 O

C 124.68 O

C

3 C 68.73 O

C 70.00 O

C 72.99 O

C

5.1.2.3 Effect of duration of peak temperature

The effect of duration of peak calandria tube temperature has been studied for two different cases of

10 s and 15 s. The rise in temperature of tubesheet is maximum when the duration of peak

temperature is 15 s because the generation of heat in the calandria tube becomes more when the peak

temperature stays for 15 s. Figure 31 and Fig.32 represent the temperature profile at points ‘B’ and

‘C’ respectively. Table 6 shows the maximum temperature observed at different points for different

period of calandria tube peak temperature (tFT).

14

Fig. 31: Variation of temperature profile of point B

with varying period of calandria tube peak

temperature.

Fig. 32: variation of temperature profile of point

C with varying period of calandria tube peak

temperature.

Table 6: Maximum temperatures at different locations for different period of calandria tube peak

temperature (tFT)

Sr. No. Location tFT = 10 s tFT = 15 s

1 A 830 oC 800

oC

2 B 117.85 oC 124.55

oC

3 C 70 oC 73.51

oC

5.1.3 3-D analyses

3D analyses also have been carried out for more realistic estimate of the temperature distribution in

the tubesheet. Due to symmetric nature of the problem, one fourth of the geometry has been modeled.

Figure 33 shows the meshed model of the 3D geometry analyzed. The model has been analyzed in

both heat generation and temperature controlled method. In heat generation method, heat is generated

in the calandria tube at a rate of 1.2×106 kJ/m

3/s and heat transfer coefficient of 2 W/m

2.K has been

considered. Figure 34 shows the temperature contours after completion of four heat generation cycles.

Figures 35 shows the temperature profile of point A along with applied heat generation cycle and Fig.

36 shows the temperature profile of points B and C in heat generation method. Figure 37 shows the

temperature contours after completion of four temperature cycles. In temperature control method, four

cycles of high temperature of 830 oC, as shown in Fig. 6, has been applied to all nodes of the calandria

tube. Figure 38 shows the temperature profile of points B, C obtained in temperature control method.

15

Fig. 33: Meshed 3D geometry

Fig. 34: Temperature contour of the model at the end of heat generation.

Fig. 35: Heat generation cycles and temperature at

point A

Fig. 36: Estimation of temperature profile of

points B and C in 3-D analysis in heat generation

method

16

Fig. 37: Temperature contour of the model at the end of temperature cycles

Fig. 38: Estimation of temperature profile of points B and C in 3-D analysis in cyclic

temperature method

In 3D analysis it has been observed that the temperature at the inside diameter of the adjacent

tubesheet lattice location is lower than that obtained from 2D analysis. This is due to the fact that in

3D analysis the heat conduction along the length of the calandria tube has been simulated, which is

not the case with 2D analysis. It can be concluded that, as compared to 3D analysis, 2D analysis is

more conservative. Moreover radiation mode of heat transfer has not been considered in this

analytical work. It may be noted that inclusion of radiation mode of heat transfer will increase the loss

of heat from the calandria tube to the ambient resulting in further reduction in the estimated

temperature of point C. Hence for the sake of performing conservative analysis, radiation mode of

heat transfer has not been considered.

17

6.0 Conclusions

2D Finite Element Analysis has been carried out for the estimation of the temperature of end shield

tubesheet at the adjacent lattice location during shock induction heating of calandria tube for rolled

joint detachment process. Heat has been supplied to the calandria tube either by cyclic heat generation

or specified cyclic temperature control methods. Two modes of heat transfer, conduction and

convection have been considered for the sake of conservative analysis. Analysis with additional

radiation mode has not been considered as it will further increase the loss of heat to the atmosphere,

thereby reducing the temperature of adjacent end shield tubesheet lattice location. Effect of several

parameters like heat transfer coefficient (h), period of heat generation (tq), gap between heat

generation (tg), calandria tube temperature (TCT), period of peak cyclic temperature (tFT) on

temperature of end shield tubesheet have been studied. A few cases of 3D analyses have also been

carried out to bring out the conservatism involved in 2D analysis.

It can be concluded from the results that during the rolled joint detachment trials, the temperature of

the adjacent lattice location can be limited to be below 80 oC. Hence, the induction heating technique

being considered for removal of calandria tube is suitable and will not affect the performance of

adjacent rolled joints. The gap between successive cycles can be increased to reduce further the

temperature at adjacent lattice location.

Acknowledgements

Authors express their deep sense of gratitude to Dr. P. K. Vijayan, Director, Reactor Design and

Development Group for his constant encouragement and support during the course of the work. The

authors also like to thank Shri Rajeev Kumar Thakur, project trainee from Delhi Technological

University, Delhi for carrying out some of the finite element analyses.

Nomenclatures

CT Calandria Tube

ID Inner diameter

OD Outer diameter

tg Time gap between two heat generation

h Heat transfer coefficient (W/m2-K)

tq Period of heating generation

theating cycle Period of heating cycle

TCT Temperature of calandria tube

tFT Time of fixed temperature

References:

1. Pritchard, D.F.; Cenanovic M.B., “Pickering large scale fuel channel replacement separation of

pressure tube rolled joints by rapid induction heating”, Canadian Nuclear Society, 6th Annual

Conference Proceedings, 1985, p. 537-541.

2. Cenanovic M.; Ng M.; Malkiewicz T.; Lee J.; Morcom J.; Pritchard D., “The improved induction

heating technique for calandria tube rolled joint separation”, Canadian Nuclear Society, 2nd

international conference on CANDU maintenance Proceedings, 1992, p. 353-362.

3. S. Chatterjee and K. Madhusoodanan, "Development of rolled joint detachment system for

AHWR-LEU", BARC Internal Report No.: BARC/2013/I/20, [2013]

4. S. Chatterjee and K. Madhusoodanan, "Development of Rolled Joint Detachment System for Low

Enriched Uranium Based Advanced Heavy Water Reactor”, Journal of Nuclear Engineering and

Design 273 (2014) 181-189.