BEST TWO REACTORS FOR MALAYSIA

Hi guys, i would like to share with you that i think the best reactor for Malaysia. This is my opinion based on the features and primary risk factors. If you have any opinion, please leave your comment..  : D

 

Based on the analysis of the features and primary risk factors of the reactors, The first reactor suitable for Malaysia is ABWR. This is because, ABWR gives more benefits to Malaysia than the other reactors. These are the features for ABWR, The vendor for ABWR is GE-Hitachi and Toshiba. It combines best BWR features from Europe, Japan and USA. ABWR outputs has margin to up rate from 1370MWe to 180Mwe and ABWR plant efficiency is 35%. ABWR also has 60 year of design life. Besides that, ABWR construction, month from first concrete to COD are 48 and 44 in Japan. The first COD unit for ABWR operation in Japan(1996) and in will start the operation in USA(2016). ABWR also extensive use of Prefab modules and it use GE digital I&C. ABWR also has single containment and four train active for safety system. For core catcher function ABWR is function partially than the other reactors which is has no core catcher function. Fuel lattice type for ABWR is 10 × 10, its discharge burn up is 60 MWd/kg and steam generator for ABWR is n/a.In term of Primary risk factors, ABWR give many advantages than the other reactors. ABWR has certification from EUR and UNC. Other reactors have not yet get the certification from UNC. ABWR in operation in Japan while mostly other reactors are still under construction. ABWR have advantages in completed engineering, operating certainty, construction certainty, cost certainty, manufacturing capability and for the others ABWR have neutral in license certainty, labor supply and life-cycle-cost. The most important things is ABWR have no disadvantages.

The second reactors are suitable for Malaysia is APR1400. APR1400 vendor is KHNP. APWR has output capacity of 1400MWe. APWR has plant 35% of plant efficiency, 35 years of design life. For the construction, month from one concrete to COD of APR1400 is 48. First unit COD of APR1400 in South Korea (2014). APR1400 use Korean digital I&C. It also has single containment, four train active safety systems and no core catcher function. APWR has fuel lattice type of 16 × 16, discharge burn up of 62 MWd/kg and it’s steam generator is two U-tube which is the largest in the world. Although APR1400 have no certification yet and still under construction. In terms of primary risk factors, APR1400 gives more advantages than the other reactors. APR1400 have advantages in completed engineering, operating certainty, construction certainty, cost certainty, manufacturing capabilities, and life-cycle cost. APR1400 have neutral in licensing certainty and labor supply and most important same with ABWR, it has no disadvantages.

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XENON-135 and SAMARIUM-149 POISONING ???

Yes my fellow friends.,.Xenon-135 and Samarium-149 was the fission products poisons !!

Believe it or not Xenon-135 has a cross-section of approximately 3,000,000 barns, over 4000 times

that of U-235. That is, each atom of xenon-135 absorbs as many neutrons as 4000 U-235 atoms. About 6.6% of all fissions produce a nuclide of Xe-135, either directly as a fission product or indirectly as a

fission product daughter. Xenon is a major problem in our reactors because of its remarkable neutron absorption and high yield.

Xenon Production:

Xe-135 is produced directly in only 0.3% of all U-235 fissions. The

following example is typical:

Did you know that Xenon-135 is mainly produced as a fission product daughter, by iodine

decay as follows:

Iodine-135 = 6.3% of U-235 fissions.

xenon production =95% (6.3/6.6 = 0.95).  (banyak racun !!)

You should know that Iodine-135 does not absorb neutrons.,.,BECAUSE  many fission products absorb neutrons. Most absorption cross-sections are small and are not important in short-term operation....=)

Xenon Loss:

Xenon is removed from the reactor by decay as follows:

or by neutron absorption (radiative capture):

The rate of burnout depends on the neutron flux. For a CANDU at full\power, neutron absorption accounts for about 90% of Xe-135 loss, decay for only 10%. Cesium-135 and xenon-136 do not absorb neutrons.

Equilibrium Xenon Load:

Guys,you need also to know that Xenon slowly builds to an equilibrium level after the reactor is started because there is no xenon in the fuel of a reactor that has been shut down for a
long time (or has never been operated)..

The equilibrium level depends on the steady state reactor power.

ILLUSTRATION OF XENON TRANSIENT TERMINOLOGY

 
· reactor start-up at time = 0 after a shutdown of one month
· reactor trip at t = 50 hours !!!!

see this graph to beleive: 

 

Samarium-149  and Other  Fission  Product Poisons:

 WHAT IS SAMARIUM-149 ?? Samarium-149 is produced directly from fission and from the decay of promethium-149 during reactor operation.   Samarium-149 is removed from the core by neutron absorption. 

Production  and  Removal  of  Samarium-149:

  

For your information,Samarium-149 is the second most important fission-product poison because of its high thermal neutron absorption cross section of 4.1 x 10⁴ barns.  Samarium-149 is produced from the decay of the neodymium-149 fission fragment as shown in the decay chain below. 

So guys,Why does this matter?? 

Because if we had it our way, we wouldn’t want any Xe-135 or Sm-149 gobbling up neutrons in our reactor. Neutrons they eat are neutrons that we can’t use to make energy by splitting fissile nuclides like Pu-239 or U-233.  

Xe-135 has two major differences from Sm-149. The first is that it is radioactive. It goes away if you leave it for awhile. It has a half-life of about nine hours.

While Sm-149 doesn’t go away. It is not radioactive. It is stable. 

 

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Lecture Summary ( Monday, 4 October 2010 )

Today, we learned about the Control Rods(CR).
1 ) Selection of CR materials
2) Types of CR
3) CR effectiveness
4) Integral CR worth
5) Differential CR worth
6 ) Rod control mechanism
7 ) CR for different Nuclear Power Plant (PWR and BWR)


Selection of CR materials : 

These are the materials of the CR,  Silver(Ag), Indium(In) Cadmium( Cd), Boron (B) Hafnium(Hf)

Most reactors contain CRs made of n absorbing materials that are used to provide precise and adjustable control of the core (move in and out).
A “black” neutron-absorbing material  absorbs essentially all incident neutrons while A “grey” neutron-absorbing materia labsorbs only part of the incident neutrons.

The grey absorber causes smaller depressions in n flux and power in the vicinity of the rod like a flat tern flux profile and more even power distribution in the core.
Resonance absorber sometimes preferred to thermal absorber.


Types of CR :


There are three types of CR.
1) Shim rods :coarse control and /or to remove in relatively large amounts.
2) Regulating rods : fine control/adjustment and to maintain desired power or temperature.
3 )Safety rods : provide a means for very fast shutdown in the event of an unsafe condition. Addition of a large amount of –ve by rapidly inserting the safety rods is referred to as a "scram" or " trip“– fast shutdown.

'SCRAM' stand for Safety Control Rod Axe Man.

CR effectiveness :


It depends primarily upon the value of the ratio of the at the location of the rod to the avarage flux in the reactor.





Integral CR worth :
The total reactivity worth of the CR at a particular degree of withdrawal from the core – greatest when the CR is fully withdrawn. Integral CR curve has an 'S' shape.





Differential CR worth :
Differential CR worth is the change per unit movement of a rod (a plot of the slope of integral CR worth curve) and is normally expressed as ρ/inch, Δk/k perinch, or pcm/inch. Typical integral CR curve has an bell shape.





Rod control mechanism :


The CR insertion rates on a scram are designed to be sufficient to protect the reactor against damage in all transients that are expected to occur during he life of the reactor.

Normal rod motion : the CR must be able to move rapidly enough to compensate for the most rapid rate at which +ive p is expected to build within the reactor in order to provide +ive control.

Minimum rod speed setting : the transient that is normally considered is the burnout of maximum peak Xe while at full power . Xenon burnout is usually the most rapid, non-accident transient expected.

Maximum rod speed setting : normally limited in order to reduce the severity of an accident involving the continuous withdrawal of control rods.

CR for different Nuclear Power Plant (PWR and BWR) :


PWR : control rod at the top






http://www.mnf.co.jp/pages2/pwr2.htm


BWR : control rods at the bottom








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