Structural Integrity

1. INDIAN STRUCTURAL INTEGRITY SOCIETY
Workshop on Structural Integrity
Assessment of Nuclear Energy Assets
9th – 10th May 2018
AERB Auditorium, Niyamak Bhavan-B, Mumbai

2. PRESSURE TUBE SECTION TRANSPORTATION FLASK FOR KAPS -1
Qualification under hypothetical accident conditions during transport
R. Pal, DCE(RTS-TD), NPCIL
S. Sharma, RTD, BARC
J. V. Mane, RTD, BARC
V. M. Chavan, RTD, BARC.

3. PRESSURE TUBE SECTION TRANSPORTATION FLASK FOR KAPS -1
Description:
Content Q-15 PT of length 1200 mm from rolled joint along with the partly
cut end fitting 200mm
Activity contact dose rate on PT segment is varying from 20000R/hr to
5000R/hr along its length
Shielding 150mm lead Shielding & 22mm steel of inner & outer shell
Dose rate on contact 48mR/hr on surface of the flask
Size 548mm outer shell dia. & 2872mm length along with shielding
plugs
Weight 6.3 tons along with plugs
Transportation
requirement
One time transportation under special arrangement with
administrative controls

4. Component Material
O.S. IS 2062 Gr. B
I.S. IS 2062 Gr. B
Bolts IS 2269 property class 8.8
TRANSPORTATION ARRANGEMENT WITH TIE DOWN ON TRAILER

5. R1
QUALIFICATION TEST – 3m FREE DROP ON UNYIELDING SURFACE
• End drop:
No Failure observed . Results are
within acceptable limit.

6. • Corner drop:
Failure of end plug bolts
observed . Failure of end plug
outer shell as strains at local
points above acceptable limit.

7. To mitigate the failure various option were considered. Initial
arrangement with minimal changes in flask is presented here
Initially designed Shock absorber at both ends
End ring: 875mm dia.
Pipe size: 3”NB std.(MS)
Total additional wt.: 70Kg x 2nos.

8. 22/11/2016 R1
End drop with
shock absorber:
No Failure observed .
Results are within
acceptable limit.

9. Corner drop with
shock absorber:
No Failure observed .
Results are within
acceptable limit.

10. Horizontal drop with
shock absorber:
No Failure observed .
Results are within
acceptable limit.

11. Results with shock absorber designed initially:
Parameter End drop Corner drop Horizontal drop
on lifting lug side
Acceptance
limit
Maximum
plastic strain in
outer shell
Within elastic
limit
Within
elastic limit
12.25% ** 15% (strain
limit for
IS 2062)
Maximum
reduction in
shielding
1mm at top 1mm at top 15mm at lifting
lug
24mm in
shielding
Maximum
loading on plug
bolts
Within elastic
limit
Within
elastic limit
Within elastic
limit
Y.S of bolt
material
Available
shielding
thickness post
drop
150mm all
around. Lead
slump is only
1mm at top
150mm all
around. Lead
slump is only
1mm at top
150mm all
around & 135mm
at lifting lug
124mm all
around
** - Maximum plastic strain in outer shell observed is 12.25% though in acceptable limit but
nearing the boundary limit. It was decided to increase the effectiveness of shock absorber by
providing additional ring primarily to absorb the energy due to impact in horizontal direction. Since
the shock absorber was modified hence horizontal drop test on support side was not carried for
shock absorber containing one ring only.

12. End ring: 1175mm dia.
Pipe size: 3”NB std.(MS) of end rings
Total additional wt.: 122Kg x 2nos.
PT flask fitted with Modified Shock absorber
on both ends

13. R1
End drop with
modified shock
absorber:
No Failure observed .
Results are within
acceptable limit.

14. 22/11/2016 R1
Corner drop with
modified shock absorber:
No Failure observed .
Results are within
acceptable limit.

15. 22/11/2016 R1
Horizontal drop with modified
shock absorber on lifting lug side:
No Failure observed .
Results are within
acceptable limit.

16. 22/11/2016 R1
Horizontal drop with modified
shock absorber on support side:
No Failure observed .
Results are within
acceptable limit.

17. 22/11/2016 R1
Slap down at 15 deg. with
modified shock absorber:
No Failure observed .
Results are within
acceptable limit.

19. Slap down at 30 deg. with
modified shock absorber
on support side:

20. Results with modified shock absorber :
Parameter End drop Corner drop
at 30 deg
from vertical
Horizontal
drop on lifting
lug side
Horizontal
drop on
support side
Slap down at
15 deg from
horizontal
Acceptance
limit
Maximum
plastic strain
in outer shell
Within elastic
limit
Within elastic
limit
6.5% 5% 7.5% 15% (strain
limit for
IS 2062)
Maximum
reduction in
shielding
1mm at top 1mm at top 10mm at
lifting lug
3 mm at
supports
14mm at one
support on up
side
24mm in
shielding
Maximum
loading on
plug bolts
Within elastic
limit
Within elastic
limit
Within elastic
limit
Within elastic
limit
Within elastic
limit
Y.S of bolt
material
Available
shielding
thickness post
drop
150mm all
around. Lead
slump is only
1mm at top
150mm all
around. Lead
slump is only
1mm at top
150mm all
around &
140mm at
lifting lug
150mm all
around &
147mm at
lifting lug
150mm all
around &
136mm at
lifting lug
124mm all
around

21. R1
Lead slump with modified shock absorber on end drop:

22. Lead slump with modified shock absorber on horizontal drop on lifting lug
side:

23. Lead slump with modified shock absorber on horizontal drop on support
side:

24. Lead slump with modified shock absorber on 15 degree slap down:

25. Reason of 3 meter drop test
While transportation, flask will be mounted on trailer whose mounting base
is 1.5 m from ground. While handling & transportation there is no
possibility of flask being lifted above 3mtr. Hence for qualification purpose
drop height is considered as 3 m. Since this is a one time transport
application under administrative control with special arrangement
therefore 9m drop height has been precluded.

26. • Drop test qualification : safe under 3 m drop height in all
orientations. 9 m drop height precluded as this is one time transport
application under administrative control with special arrangement.
• Drop on punch: outer shell thickness (14mm) sufficient as per
empirical formula.
• Thermal test qualification: not considered as this is one time
transport application under administrative control with special
arrangement.
• Tie down arrangement: designed for 1g (lateral), 2g(longitudinal),
2g(vertically up) & 3g(vertically down) as per IAEA Safety Standard
Series TS-G-1.1 regulations .
• Water immersion test qualification: not considered as there is no
possibility of activity release due to leaching. Sealing is precluded.

27. Tie-Down System on Trailer chassis for 'Pressure Tube
Transportation flask
Shear Stress on outer bolts
n = 24 (for longitudinal and lateral load calculation)
Shear stress = (M * ax)/ (n * Ab)
= (6524 * 2 * 10)/(24*0.000201)
= 27.04 MPa (for longitudinal)
= 13.5MPa (for lateral)
Tensile strength = 880 MPa (Bolt as per IS 2269 property class 8.8 selected for use)
Tensile load on bolts farthest from point ‘O’
T = [M{ Hg (az-g)+ Zga}]/Hn
T = 68558.9 N
Stress = = 341.0 Mpa (M20 bolts)
Fig. Force diagram used in analysis

28. EFFECT ON LEAD SHIELDING OF FLASK DUE TO 1 METER DROP ON PUNCH ( TEST FOR ACCIDENT CONDITIONS
IN TRANSPORT)
The effect of 1 meter drop of flask on the punch of 15 cm is of local nature and will be on the outer shell and
on the shielding. The effect on shielding will be only analyzed here.
The deformed on frustum of a cone with major diameter = ‘3d’ & minor diameter = ‘d’;
where ‘d’ is the diameter of the punch.
This is based on the puncture tests of many flasks, which shows that maximum deformation is within 3d
diameter circle around the punch. (Ref: ORNL NSIC-68 article 2.2.1 )
Let X be the depth of deformation, then from the geometry, the height of the cone is equal to 1.5 X.
Therefore, the volume of the frustum
V=1/3 x /4 x [(3d) 2 x 1.5 X – d2 x 0.5 X] … … (1)
Energy absorbed by lead : EPb = V x Pb … … … (2)
This energy has to be equal to the energy acquired by the flask by 1 meter drop.
W x h =V x Pb … … … …
… (3)
Where,
W = weight of the package = 6300 kg.
h = height of the drop = 100 cm
Pb = dynamic flow pressure of lead = 350 kg/cm2
d = punch diameter = 15 cm
V = 1714.285cm3
Therefore from equation (1); we get X = 2.510cm =25.1 mm

29. Energy absorbed by outer shell plate can also be estimated from the depth of deformation of lead.
Energy absorbed by shell = Force to puncture * movement of plate
E s =  x d x t x  x X/2
=  x 15 x 1.4 x 800 x 2.51/2 = 66237.34kg-cm
V = (W x h – Es )/ Pb = 533762.660/ 350 = 1525.036 cm3
Depth of deformation = 2.233cm = 22.33 mm

30. OUTER SHELL THICKNESS OF THE FLASK RESISTANCE TO PUNCTURE DURING 1 METER DROP TEST
The outer shell thickness of the flask has to be designed to conform to :
The resistance to puncture during 1 meter drop test on a mild steel punch of 15.0 cm diameter and 20.0 cm
long as mentioned in para 26(b) Schedule III of mechanical test of accident conditions in transport of AERB
Safety Code SC/TR-1, 1996(1).
For hot rolled Carbon Steel and Stainless Steel, the minimum outer shell thickness of flask required to
withstand puncture action is given by the following equation. (Ref. ANSI–N 433.1-1977(7) and ORNL. NSIC
– 68, Cask Designer Guide- Feb 70) (8)
t = 1.3016 x ( 1.3 x W / S )0.71 … … …(1)
where,
t = shell thickness in mm
W = flask weight in kg
S = Ultimate Tensile Strength of the outer shell in MPa (1 MPa = 0.102 kg/mm2)
= 518 MPa (75129.55 psi)
Ref. 1998 ASME Boiler and pressure vessel code Section II, Part D (15)
Substituting the above values:
t = 1.3016x ( 1.3 x 6000 / 518 ) 0.71
= 8.926 mm
where, W = weight of the flask / package in pounds
t = thickness in inches.
Substituting the above values;
t = 0.2738” = 6.955mm

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