How Insurance Works

Mod-09 Lec-17 Quality Assurance


Good morning, everybody. In the last two lectures, we had a glimpse
into how the various events are being analyzed and how we are predicting the response of
different types of reactors to an initiating event. We also saw how we validate the computer codes,
which we have developed for predicting the response of the plant to these transients. Now let us go into the most important aspect,
which is very truthfully followed right from the conception of nuclear power plant and
till the plant is designed, operated and even the commission. So, in this respect, I will take you through
this lecture on quality assurance. This quality assurance is not a new word at
least as far as any industry is concerned because in every manufacturing industry, before
we start the manufacture, we do have a quality assurance plan. Then we go about the manufacture. So what is a quality assurance? So now let us look at what is this Quality
Assurance. Basically, it is a set of planned and systematic
actions, which need to be carried out so that an item or an operation is done to satisfy
the requirements of quality. So then what is quality means any equipment
should operate reliably with maximum availability when we want it to operate. So this in total picture is called as a quality
assurance plan. Now if I want to have quality assurance, we
must have list down what is our plan, at every stage what I must do. So, first, when we look at a nuclear power
plant, we look at the design. So in design, how do we achieve quality assurance? Okay. I have designed the thing. Have I verified my calculations? Is my model right? Here in the last lecture, I gave you an example
of validation. This is a part of quality assurance. Then in case we find a deviation, so we need
to correct it and then implement the rest of the program. So not only that, in quality assurance, every
stage is documented. So the clear history is available at any stage. I can just give you an idea. Suppose a component has been manufactured
for the Fast Breeder Test Reactor in — in the 70s. Today if there is a fault with that equipment,
I can trace out completely fabrication, whether there was anything missing, anything inspection
or anything I can find out. All the things are documented and safely kept. So to achieve first is as I said design, quality
in design. Then when you go to the manufacturing, at
every step what sort of tests I had to do? How I should satisfy myself that my manufacturing
is perfect? Then I go to commissioning. When I go to commissioning, when should I
say my plant is commissioned? What are the things to be — points to be
checked? What is the checklist based on which I will
say it is commissioned? Same thing in operation. How do we achieve? Then maintenance, then surveillance and in-service
inspection. So an organization has to be set up which
is responsible for quality assurance at every stage of the plant. So in this lecture I will take you through
the various aspects of quality assurance. Now, if you ask me, if you say quality assurance
plan, we always say QAA. QAP is a common jargon used in the industry,
manufacturing industry is very common. Of course, in our nuclear plant, we talk about
it every day. So what it is? It’s the endless thing. It includes procedures. It includes instructions. It includes drawings. For example, you have to achieve a certain
dimension and certain dimensional tolerance. Let us say I want 12 plus minus 0.1 mm in
one part. Another part may be 25 plus minus 0.2. Everything, all these are reflected in the
drawings with necessary instructions. Then when we review the drawings and any — every
stage where there was a review, these reviews are to be recorded. Then in the QAP, we also have to tell who
is the person responsible and who has the authority. Every stage is not cleared by the same person
to say, “Yes, it is okay.” If one person checks, there will be another
person who says is it okay and these things need to be communicated up and down so that
everybody is aware. So it includes interfaces between different
stages of the manufacture, of the design, everywhere. So interfacing, it should be very clear. So a document is made. It must be sent to whom? Who all it should be sent? Even that is a part of the Quality Assurance
plan. Staffing. Let us say I have to operate a plant. I know that there is a minimum requirement
of at least one engineer in the control room and assisted by two operators. Then there is need for local operators at
different places. So I have to tell what is the minimum staff
requirements and that should be followed. Then training the people. It is very common. Training is without a training. And document preparation and document control. I mentioned every stage you need to have a
document. Then reviewing and approving. Who approves this document? And its release and its distribution to the
different agencies. Then document change control. Suppose let us say there is a design change
or there is a revision of a particular document in view of the observations. Then there has to be a change. So who approves that? Then design interfaces. The designer might have an interface with
a manufacturing agency. So where is a designer come in the interface? For example, if there is a deviation in any
manufactured product from what is indicated in the drawing, there are two approaches. One is the designer looks at it. He says no, it is still acceptable. He agrees. So he gives a design concession to the manufacturer
saying that you can go ahead. This is a document which is cleared by the
designer. Otherwise designer says no, it is not acceptable. He gives a rejection. So these things are the designer interface. Then design verifications. I mentioned you must know that the design
verification is there. Design changes. Maybe we had made the documents of the design. We discussed it in the safety committees. The safety committee on review let us say
suggested a change. In the light of the regulatory authorities’
observation, you make a change. This design chain must be again put revisions
of the design document made. Then what are the requirements for procurement
and control? I have to procure a material. I have to procure a machine. What should be the agency? How we should go about it? So all these are — will be there in the document
plan. Then supplier. Evaluate a supplier. There may be many suppliers of a particular
equipment, but you need to buy the equipment from a supplier who has got a very reliable
— he should be a really reliable supplier. He should preferably be a original manufacturer
or he should be a very reputed agent plus he must have provision for after sales service
and maintenance. So all these need to be assessed. That is where we say supplier evaluation and
then selection. In fact, in the nuclear power industry, before
we get into ordering the components for a plant, we go around manufacturers in that
area, and we evaluate them, and then only we shortlist who are the people. Then only we start issuing the documents or
tender documents for the procurement. Then let us say you have ordered. Your items are coming. So quality assurance, quality control at the
plant is anyway there. Now how the items which are purchased, how
they are to be controlled? How they should be preserved? Because a component might come this year. It might be put into the plant next year. So how do you preserve it? Even this is a part of the quality assurance
plan. Then you must be having your tag or identification
of different materials. You must know where different parts are located,
where should be all these things, again, appears to be simple, but for a large plant, everything
is systematically has to be planned. Then when it comes from the company, how it
is to be shipped? I forgot. Shipping is very important aspect. During shipping it should not get damaged. So how the packaging should be? These things are very, very important for
the assuring the quality of a nuclear power plant. I repeat no doubt such plans are in existence
for other industries also, but in the nuclear, we follow it threadbare because we know that
at any stage, there should not be a cause for release of radioactivity due to anything
which is not a quality product. Inspection test control I mentioned, so the
inspection program. Who will do the test? Whether the operator who is going to do the
welding, whether he is trained? Whether he has been tested? In fact, you would be surprised many times
a welder is qualified on the day morning and then only he will be put. He won’t be every day or every alternate day
he need to be tested because we need to see that he is in the best of health to do the
job. Then the equipment which he is using for inspection,
whether they are calibrated? Whether they are really giving you the actual
condition of the equipment or the actual dimension? So all these things are included in the quality
assurance plan, and as I mentioned in case there is a non-conformance, how do you go
about it? There should be to whom it should be given
or this much range you can accept. All these need to be documented. Then what sort of records, how do we preserve
them? And earlier and all we used to preserve them
in hard copies. Today we have soft copies and then not only
that, the quality assurance records are audited from time to time by different agencies. We will look into this in the further slides. Okay. Classification of plant components. What does this classification — why we talk
about classification? Let us look at a nuclear power plant. You have got the reactor core, very important,
up to the steam generator, yes. If you take a reactor, if there is any problem,
radioactivity again come out, but in the case of steam generator, it is not that much. Only water may come leak out. But if you go further to the steam water system,
let us say there is a valve leakage or something, it is not that much of a worry. So we want to give the highest quality assurance
to the reactor core components, may be a second level in the — to the steam generator and
your third level. Why? All these quality assurance involves large
amount of testing, documentation, and verification and audit. So it becomes uneconomical if you do it for
a component, which is not that much in the safety category. So, basically, we need to make a decision
on how to classify the different components. Now let us look what are the points we have
to keep in mind. So for every class, we have to tell what should
be the design criteria, what should be the construction criteria and operation criteria. For every class, there would be a difference. Then what about the redundancy, emergency
power supply, and how they are for each every class, and whether the availability of that
those systems should will come in the way of safe operation of the plant? In a similar way, the Quality Assurance also
is graded. If this is Class 1 on the reactor, Class 2
for the steam generator, and Class 3 for the rest of the plant. Let us see what are the classifications. So this is basically on the safety function. You take a pressure component, basically,
a pressure vessel. Yes, it should be in the highest class. Then coming to earthquakes, again, we have
to see whether that component, if it gets damaged, whether it can affect the operation
of the plant. If it is going to operate the safety of the
plant, then again it has to be in a higher class. Similarly, the instrumentation, the control
systems, again, based on what sort of a safety function they need to adopt. So, finally, safety is the watchword. So the vessels, the pipe, and the pressure
components or the primary cooling system of a nuclear power plant are put in Class 1. Let us take — we are talking about a pressurized
water reactor so that you know in case of any failure of this, we can have a loss-of-coolant
accident, so we need to give it the highest class. The emergency cooling system for the core,
anyway, that won’t be continuously in operation. It will come only when there is a failure
like LOCA, which is a bit of a lesser probability. So we put it in Class 2. Then we look at the support systems like the
compressed air system and other which are going to be supporting the emergency cooling
system. We put it as Class 3. Then we look at the station firefighting system. You know in a heavy water reactor, this fire
water system is used for quenching the — putting the reactor core, submerging the reactor core
in case of a very large LOCA, but here there are enough industrial standards which are
being followed presently, so there is no need to unnecessarily put a another new classification. So we follow the industrial safety standards,
which are being followed everywhere for this firefighting system. Okay. We come to the materials. Now when you say the materials, we will say
austenitic stainless steel as per some standards, let us say ASTM standards. Okay. If there is any deviation from the ASTM standards,
we need to mention. Then what would be the fabrication standards? If it is as per ASME, we can code the relevant
ASME sections, and then need not stress further because most or nearly all of the fabricators
know the ASME codes. Then any other additional requirements, for
example, when we buy pipes, we normally go for measurements of the pipe, how they are,
we procure them, and then we do random ultrasonic testing to know the thickness, but in case
of sodium systems where the austenitic stainless steel pipes are used, we want 100% ultrasonic
and when it is welded, again, 100% radiography plus 100% ultrasonic testing. So these are some additional tests. So we need to tell what are the additional
tests. Of course, the designer will specify this
additional testing. Then any limits on the alloying elements. For example, Carbon should be less than 0.15
to 0.25 for weldability consideration or what sort of impurities you would not like to have,
which because it can cause corrosion by the coolant. So these sort of things are to be specified. This specification has to be drawn up for
the materials very clearly. Then how do I qualify the procedure? You have got a certain procedure for welding,
and the welder has to follow that procedure, and he — we should satisfy that he is able
to do a good sort of weld. Then the destructive tests, if any, of course,
in the case of nuclear power plants, we mostly go for non-destructive testing, and whether
there is any need to do a metallograph of the heat affected zones. Basically, when you do welding, you know,
the area around the weld does get affected by the heat. Whether it has changed any characteristics
of the material if you would like to know? I think that also needs to be specified. Then okay, now defects are found. How do I evaluate the defects? And how much of defect I can accept? So all these things. Then of course, in the material choice when
I do, I have to keep in mind that in the presence of water and stress, corrosion can take place. So whether that is basically even though this
is a part of the design basically, whether this is okay. So the material right from the beginning,
the pro-fabrication, everything has to be under — follow the Quality Assurance procedures. Now in the design, what we do? One, we talk about the postulated initiating
events in the last few lectures. So every event gives a temperature or pressure
transient to the plant and the design is governed not only by the temperature transient or the
pressure transient seen. It also depends on number of times because
repeated things can cause fatigue of the material. So this needs to be very clearly given by
the designer. Then if you look at a safety valve, what should
be the capacity of the safety valve so that in a given condition it is going to relieve? So this a designer has to in the — assure
that this will really take place. This is a quite an important aspect because
in many times when safety valves are open and the pressure surges are there, something
like water hammers, something like a hammering noise have been heard, and that is because
of the layout of the piping and it can fail. Sometimes the pipes have failed when the safety
valves are opened. So these things need to be kept in mind by
the designer. So this is a verification, and the designer,
and we may do a 1-D analyses or a 2-D analyses. Many times we do a 2-D analyses because 3-D
analyses is very time consuming, but in areas which are very critical areas, critical belts
areas, we do a 3-D analyses and satisfy ourselves that the 2-D analyses is okay, well meeting
our requirements. That is it is able to give an accurate prediction
for our transient. Of course, detailed LOCA analysis needs to
be done that has to be done for any light water reactor. So fabrication, and inspection, weld procedure
qualification, then how to qualify the weld, procedure qualification, then qualifying the
weld, then positions of repairs to welds, and base metal. This position is very important. A component is in position, in a particular
position, but the operatory will be having different positions. His ability to do a weld, blind weld, suppose
he is here and he has to do a weld here, he can’t see. It has to be seen. So what is the position? All these things need to be recorded so that
you know if there is a problem in the weld, maybe if I change the position, the weld could
be repaired. In fact, these are tested before we do the
final weld on the actual component. Now non-destructive examination. You have produced — you’ve procured plates,
forgings. Then you must check it before you fabricate. Then after you fabricate also, if you want
to see some metallograph you need to see. Then suppose you want to do some hydro tests,
you need to do them and satisfy yourself that everything has been fabricated well, and record
all these tests so that we can have a record in case there’s a problem, we can trace out
the cause or the stage at which the error has happened, and once we do that, we will
review our procedures so that next time when we make the same component, we don’t get into
similar problems. As I mentioned we have to learn from our own
mistakes. Nowadays, it has been a practice to not only
have a written record. We also have a video record of the fabrication
process so that we can easily find out how the thing has gone over. Then these things, the customer will have
a surveillance of the fabrication facility at all stages so that he’s satisfied that
this — it is moving at different stages. Then as I mentioned ultrasonic testing is
a very special art. We do have equipments which are automatic
and very good. Nevertheless, we need to qualify these operators
who do the ultrasonic testing. Then for any equipment, any quality check
we do, we need to tell what is the acceptance level, what is the rejection level. Let us say in a weld, there is a porosity. How much porosity I can accept? How much porosity I cannot accept? So these things they have to be — these things
need to be specified even before the fabrication starts and one more thing. Many times as I mentioned about a blind welding,
sometimes inspection also becomes difficult. So if the inspection is going to be difficult,
we need to accord the highest importance to those areas so that inspectability is not
there for that area. No doubt it is our endeavor to all — make
all components, fabricate all components such that all welds are inspectable, but in some
cases it becomes difficult. So in all these steps, adequate Quality Assurance
is very essential. Now let us say we have moved, fabricated. We have put in the plant. We are going to commission and operate the
plant. When we operate the plant, we need to record
what all sort of transients the equipment sees. Of course, for some components like the turbine
generator, all manufacturers of turbines, along with their turbine, they have a unit
which records all the conditions through which the turbine is going, when it starts, what
is the temperature of the steam it receives, what is the pressure of the steam it receives,
how the pressure went down, how the temperature went down, everything is recorded. So like that we need to record practically
the whole plant, especially, the safety related equipment very close to the primary sodium
system and the associated things. The reason is in case of a problem, we will
be able to trace when it happened and how it happened. So then, in operation, we have to have inspection
by the quality control or by some other means so that we know in service if anything has
happened, we will know. For example, there are welds on the reactor
vessel which are actually inspected from time to time to know their health because vessel
pressure vessel is the main boundary for the release of any coolant and LOCA can occur. So we must see that the boundary is intact. In case we find some change in the weld based
on the ultrasonic testing, we can stop the reactor. Then in all places, you may not be do in-service
inspection so maybe you have to do the — stop the plant and do the inspection. So this also will be recorded. Then let us come to the maintenance. Now there are two types of maintenance. One, we can call as preventive maintenance. Then in preventive maintenance, we do a maintenance. We know this component can get some problem
let us say after operation for six months. So I decide after four months, I will inspect
this component and see whether it is in good condition. So here it involves an administrative and
a technical aspect to be done that is at the end of four months I need to do it. So it needs to be — if it is not done, the
further operation clearance should not be given. So this is done on all structures, systems
and components so that at any stage, if there is a tendency to fail, we know that is going
to fail. Then this can include also repair, any servicing. So all these things need to be scheduled,
so scheduled in the Quality Assurance plan for maintenance. So that is a preventive maintenance and when
we do repair, a fault has happened, we call as a corrective maintenance. So as I mentioned, we need to draw the schedule,
what is the period of inspection? What is the period of maintenance? Everything needs to be planned well in advance. Then surveillance. What is surveillance? Surveillance means, you know, we talk about,
you know, somebody, you know, surveillance has been kept over this person and that person. That means we observe the movement of the
person and here in a nuclear power plant, we look at the equipment to see whether it
is operating as per our requirements, whether it is operating as per the operating conditions,
which we have said, and we should be able to — when you do this, you can detect any
abnormal condition. Let us say an equipment was operating and
there was a small bearing failure or bearing, you know, loss of cooling. What will happen? When you — when you are very close to the
equipment, you may hear different noise, screeching noise. Oh, now I know that the bearing is going to
be a problem. I take a — immediately, I stop the motor
and do what I should do. So here this is called you can call it as
a walkthrough. Surveillance could be a walkthrough, and we
should put in our program, what sort of abnormal conditions which we expect and we should also
put down what sort of acceptable limits? Suppose let us say there is a noise. Maybe normal noise was about 20 or 25 dB. It has increased to 30 dB. Should I act or should I worry only when it
should be 40 DB or 40 decibels? So these are the things. So, basically, the operating organization
will establish a surveillance program so that all the system’s components are which are
basically most important is safety are operational at all times. You might many times wonder sometimes people
just walking through the plant just looking at things and going. You might be wondering they’re roaming. It is not. They are doing surveillance. Sometimes the surveillance is done to see
whether the operator is at the seat, at his position. Operator should not be moving away from his
position for a very long time. The purpose of an operator is to attend to
the function. So this is also one part of the surveillance,
and we need to see that slightest changes which are there, we immediately react to the
situation. Then we come to the in-service inspection. Now as I mentioned earlier, inspecting the
components in service is quite tough, difficult. So we need to define which components are
very essential for continued and safe operation and in the fabrication of that component,
this point has to be kept in mind that this needs to be inspected. So he has to make provisions in the design
such that it can be inspected. For example, we have tube to tube sheet welding
for many steam generators. Basically, I am talking with reference to
the fast reactor, sodium-cooled fast reactors, and the experience has shown that the leaks
in the steam generator have mostly taken place at the welds, tube to tube sheet welds. Then when we looked at the tube to tube sheet
welds we found it is not inspectable 100%. So designs developed by which the tube to
tube sheet welding could be — was made in such a way that it could be inspected 100%. So this way in the design itself you foresee
that it requires in-service inspection. So I must design such that it is inspectable
and again, as I mentioned, the emphasis is placed on inspecting the pressure boundaries
because that is where our loss of coolant can happen. So when you say something has gone wrong,
you require a baseline data. So baseline data before operations started,
so we have the baseline data when it was fabricated. Then we have a next set of data when it has
been commissioned, and then further during operation and if you see the change in that
pattern, you immediately change a signature as they call. You look at it. Now, again, I can give you another example. In one of the reactors, there was a component
which was vibrating inside, but there are no vibration monitors, which can be kept inside
the plant, but they had inspection, ultrasonic inspection of the primary vessel. So, and this was being done when the reactor
was in service because it is outside the vessel, and that ultrasonic probe picked up some noise
level and this noise level picked up, they found that this is not anything to do with
the vessel because the resonance frequency of the — frequency of the noise didn’t match
with the — that natural frequency of the vessel. Then slowly when they studied further, they
found it was due to a baffle movement inside. They shut down the plant and it was. So here, again, you see how an inspection,
in-service inspection or a surveillance can help you. But mind you the same equipment which you
used for inspecting earlier should be used later. You should not because again, the calibration,
everything would change. So this is a very important aspect to be kept
in mind. Then all this maintenance, surveillance and
inspection should include all generation of adequate records, procedures. Then work authorizations. This you must have seen whenever you go to
a power plant, you will see some tag on some of the switches or some of the valves with
some notings. Basically, it is an authorization given based
on a work permit. Suppose the maintenance person needs to do
maintenance on a certain equipment, he just cannot go and start doing something. The plant might be in operation or it might
not be right to go and work on that equipment now. Maybe there is a high level of radioactivity
in that area. So he has to get a permit from the operation
crew to say, “Hey, I want to work here. Can I work? When will you allow me to work?” All these things has to be there. And if he is going to work in an area where
there is radiation, one has to see that there is an adequate protection which is equipments
being taken by the people who are going to do the maintenance. Again, calibration of whatever tools and equipment
they take, you should not forget industrial safety. Nuclear safety doesn’t mean you don’t follow
industrial safety. Nuclear safety is in addition to industrial
safety. Then like fire hazards or any other general
risks you can take. Then use of interlocks and keys. Many times we need to have an administrative
look into before we start a particular operation. For example, I want to start up the reactor. Now when I have to start up the reactor, many
systems need to be available, but whether all the systems are available, that will be
individual crews, you know, decision, okay, to say that okay this is available. I have tested and then maybe he gives a signal
to the control room saying that this is over. Like that all systems come. So when all these systems had come, then the
reactor superintendent decides, “Oh, everything is correct. Now I can start it.” Then he will give put his key and give startup
authorization. So this is again a, what we call, a part of
the quality assurance so that it doesn’t happen that just like that your plant can — person
— any person can start. So these are all called for administrative
control this gives. If it is automatic, there is no need for this. Then training and qualification of personnel
is a very, very important aspect of quality assurance. We have to decide what sort of a training
I should give? What sort of a training I should give to an
operator? What sort of a training I need to give to
your tradesman? What sort of a training I need to give a diploma
holder? What sort of a training I need to give a person
who is going to work in the radiation area? So all these are put down and the trainings
are vetted. The person goes to the training. He goes through exams. He goes through checklists before he is authorized
to operate. Then the control of materials and spare parts
is very important. There is need to maintain a certain amount
of spares. Then housekeeping is very important. We talk about Swachh Bharat. We should be everywhere it should have a clean
condition. In fact, you might be — I tell — I see people
telling hey, nuclear clean condition, nuclear clean condition means absolute cleanliness
to the maximum possible. Then preventive maintenance programs, then
generation of records. So this is what I said about the training
of qualification personnel is very important and they need to be reviewed at every stage
based on the feedback from the operating organization and the auditing of this should be done by
the regulatory agencies so that to see. In fact, many times when the licenses are
given to the operating personnel, the regulatory people need to be involved. Now plant ageing, for example, I say I have
put up a plant for design life of 20 years. Now 20 years is going to be over. I need to know whether I can extend the life
of the plant. So this requires special attention. We need to be aware what sort of mechanisms
are important which can cause material corrosion. It should be important or what is important? So we have to monitor the plant specifically
for whether any degradation has taken place, whether the pipe thickness has come down,
how much it has come down, whether the residual thickness is okay for continued operation? If so, how much? So besides the thickness etc., we also do
strain gauge measurements in normally pipings in different parts of the plant to know what
is the strain that the component is seeing and whether it is within the limits. Surely, we use a lot of non-destructive examinations
under this stage like ultrasonic inspection, eddy current inspection so that we get to
know the true state of the equipment at the end of its operation and this data we give
to the regulatory authorities before getting clearance for further operation. Now as I mentioned initially, when we are
going to procure any component or service, we do a quality survey of all the agencies
and then only we award the contract. So this is called as a quality system survey. Then audit, quality audit. Now within the vendor, he may have an internal
inspection so that is the first stage in which he, his own people do the job and his own
— some another set of his own people may do the auditing to see whether everything
is in line with the requirements. Then if suppose it is a very important equipment,
we go for a second party to audit from outside organizations or it could be the customer
himself the second party. Third, totally, neither the customer, neither
supplier. It could be a third party inspection and this
is decided based on the importance of safety of the components. If you look what all I have told you, there
are lot of advantages of quality assurance program that you are assured a very good what
you call implementation of what is happening and it is you get a reliable component, reliable
— you’re assured that plant is safe, but disadvantage it is complex. It is quality manpower would be very costly,
and it may many times results in resistance, but then we have got to do that. In summary, this lecture has given enough
assurance about the quality practices in all facets of the design, construction, operation,
maintenance, surveillance and inspection of a nuclear power plant. Thank you.


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