PRESENTATION ON RADIOGRAPHY Danish Khan

000CE11DD07

Ayush

Bhardwaj

000CE11DD05

RAJIV GANDHI PROUDYOGIKI

VISHWAVIDYALAYA

DUAL DEGREE PG PROGRAM

OUTLINE

Principle

Gamma Ray Radiography

Application in Structural Engineering

X Ray Radiography

Safety Measures

Conclusion

INTRODUCTION

Rad

iogr

aphy

Gamma Ray Radiography

X-Ray Radiography

Neutron Radiography

Micro Radiography

PRINCIPLE

When radiographic rays are directed into an

object, some of the photons interact with the

particles of the matter and their energy can be

absorbed or scattered. This absorption and

scattering is called “Attenuation”.

ATTENUATION

The relationship between the intensity of photons

incident and transmitted is:

where

I is transmitted photon intensity,

I0is incident photon intensity,

µ is attenuation coefficient,

x is thickness of object

EFFECT OF ATTENUATION

As the radiation passes through the member its

intensity is reduced according to the thickness,

density and absorption characteristics of the

materials within the member.

The quantity of radiation passing through the

member is recorded on a film.

GAMMA RAY RADIOGRAPHY

Gamma rays are types of electromagnetic radiation

of shorter wavelengths than visible light

Shorter wavelengths permit penetration through

materials

High energy levels break chemical bonds

allows “looking” inside structures with

photographic fidelity

ELECTROMAGNETIC SPECTRUM

GAMMA RAYS

Gamma radiation is the product of radioactive atoms.

Depending upon the ratio of neutrons to protons

within its nucleus, an isotope of a particular element

may be stable or unstable.

Over time, the nuclei of unstable isotopes

spontaneously disintegrate, or transform, in a

process known as “radioactive decay” and such

material is called “radioactive

material”.

RADIOACTIVE DECAY

GAMMA RAY SOURCES USED

Two of the most common industrial gamma-ray

sources for industrial radiography are Iridium-192 and

Cobalt-60

Iridium 192 –

Energy : 0.317 to 0.468 MeV

upto 25 to 250 mm thick concrete

Cobalt 60 –

Energy : 1.332 to 1.173 MeV

upto 125 to 500 mm thick concrete

RADIOGRAM AND ITS INTERPOLATION

SETUP FOR CONCRETE TEST

APPLICATION IN STRUCTURAL ENGINEERING Moisture Content

Detection of reinforcement location

Detection of Voids and Cracks

Detection of quality of grouted post-tensioned tendons

Measurement of bar depth and flaw depth

The failure of cables

Discontinuities of the ducts

Broken wires or cables in some cases

MOISTURE CONTENT

For materials with uniform thickness and porosity,

the transmitted intensity of gamma rays is

dependent only on the moisture content of the

pores.

Find Gamma ray intensity transmitted by that same

material when it is dry.

DETECTION OF REINFORCEMENT

Reinforcing bars absorb more energy than the

surrounding concrete and show up as light areas

on the exposed film.

DETERMINATION OF CRACKS

Cracks and voids, on the other hand, absorb less

radiation and show up as dark zones on the film.

Crack planes parallel to the radiation direction are

detected more readily than cracks perpendicular to

the radiation direction.

QUALITY OF POST TENSIONED MEMBER

Gammagraphy at 3 different location of bridge,Observe the marked void in upper duct of Plate 1 (dark band)

In Argentina’s largest bridge complex, Zárate-Brazo Largo,

MEASURING DEPTH

Depth of bar and depth of flaw can be measured by

many ways :

Rigid formula Method

Single Marker Method

Double Marker Method

RIGID BAR METHOD

B D BT, D

A T D A B

H D K

T - D

D

H

K

FILM PLANE

FLAWCONCRETESPECIMEN

SHADOWS

MARKER METHOD

MARKER

T

H

K

SOURCE PLANE

FILM PLANE

FLAWCONCRETESPECIMEN

SHADOWS

B1

A

B2

IF B2 = 2 B1FLAW IS AT CENTRE

X-RAYS

XRAY EQUIPMENT

Three basic requirements must be met to produce X

rays, namely,

(a)source of electrons as a heated filament,

(b)means of directing and accelerating the electrons

as a high voltage supply,

(c)target which the electrons can bombard, normally

in the form of heavy metal

PRINCIPLE

The specimen absorbs radiation but where it is thin

or, where there is a void, less absorption takes

place. Since more radiation passes through the

specimen in the thin or void areas, the

corresponding areas of the film are darker.

X RAY TUBE

REQUIREMENT FOR OPERATION • the X ray tube must be powered by a stable electrical supply. Power

variations in the filament and the high voltage circuit alter the

spectrum and intensity of the generated X ray.

• the target anode and its connecting support structure must be

cooled and be designed to facilitate heat dissipation. A large rotating

anode, which spreads the heat produced over a larger area of the

anode, is often used to extend the serviceable life of the anode and

provide a stable emission of spectra.

• the electron beam emitted from the cathode and the X ray beam

emitted from the anode be focused so that a narrow, high intensity

beam of X rays is produced.

GENERAL CAUTIONS IN RADIOGRAPHY

Specifically trained and accredited persons for

implementing the technique

Define a protection area around structure

Move away all the persons during the entire test

RADIATION PRECAUTIONS AND SAFETY No practice involving exposures to radiation should be adopted unless

it produces sufficient benefit to the exposed individuals or to society to

offset the radiation detriment that it causes.

In relation to any particular source, the magnitude of individual doses,

the number of people exposed and the likelihood of incurring exposure

where these are not certain to be received shall be kept as low as

reasonably achievable economic and social factors taken into account

The exposure of individuals resulting from the combination of all the

relevant practices should be subject to dose limits. These are aimed

at ensuring that no individual is exposed to radiation risks that are

judged to be unacceptable in normal circumstance

The most important aspect of radiation protection, assuming

that the practice is justified, is to keep radiation doses as low

as reasonably achievable.

REQUIREMENTS

Role of Authorities

Inspection and enforcement

Safety culture

Local rules and supervision

Quality assurance

PRACTICAL PROTECTION

Time

Distance

Shielding

Prevention of access

ADVANTAGES

Both surface and internal discontinuities can be detected.

Significant variations in composition can be detected.

It has a very few material limitations.

Can be used for inspecting hidden areas (direct access to

surface is not required)

Very minimal or no part preparation is required.

Permanent test record is obtained.

Good portability.

DISADVANTAGES

Hazardous to operators and other nearby personnel.

High degree of skill and experience is required for

exposure and interpretation.

The process is generally slow.

Highly directional (sensitive to flaw orientation).

Depth of discontinuity is not indicated.

It requires a two-sided access to the component.

DISADVANTAGES

For application in Bridges with long span, the

power required will be very high

Several hundred metres of area will need to be

cleared so that no possibility of accidental

exposure.

Not feasible in densely populated area

CONCLUSION

Gamma Ray Radiography is a powerful technique as it

enables us to look inside the structure literally

possible to study concrete reinforcements with

unprecedented detail and accuracy

Applications fall outside the scope of the routine

inspections of reinforced concrete beams columns and

slabs

Safety issues are there which needs to be taken care of

properly

Thank You

REFERENCES

Guideline on Non Destructive Testing, Ministy of Railway,

Government of India

Non-Destructive Assessment of Concrete Structures:

Reliability and Limits of Single and Combined Techniques -

RILEM STATE-OF-THE-ART REPORTS

Guidebook on NDT, Department of Atomic Energy

Investigations With Reinforced Concrete Tomography M.

A.J. Mariscotti, P. Thieberger, T. Frigerio, F. Mariscotti And

M. Ruffolo Thasa