7.19 and 7.20

7.19 and 7.20

12 January 2012

10:32
· 7.19 understand that a chain reaction can be set up if the neutrons produced by one fission strike other U-235 nuclei
· 7.20 understand the role played by the control rods and moderator when the fission process is used as an energy source to generate electricity
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7.17 to 7.20 Plenary Answers

13 January 2012

14:17
1. What is the process of splitting large nuclei called?

Fission
2. How is 235U made to decay inside a nuclear reactor?

It is bombarded by a neutron to turn it into 236U which is unstable and rapidly decays

[cid:image001.png@01CD01EA.AD5C6120]
3. What are the generic names for the products of a fission reaction?

Two daughter nuclei and either two or three neutrons are produced

[cid:image002.jpg@01CD01EA.AD5C6120]
4. In what form is energy produced during a fission reaction?

Energy is released in the form of Kinetic Energy of the products of the reaction - the two daughter nuclei and the neutrons
5. For a stable chain reaction to occur how many neutrons must, on average, collide with another nucleus of 235U?

Exactly one. If the value is less than this the reaction will eventually finish. If the value is more than this the reaction will very rapidly accelerate to explosive rates - utilised in nuclear weapons

[cid:image003.jpg@01CD01EA.AD5C6120]
6. What is the purpose of the moderator?

The moderator slows down the neutrons produced by fission so that they can be captured by other 235U nuclei and thus sustain the chain reaction
7. What do the control rods do?

Control rods absorb excess neutrons in the reactor and thereby provide a method for controlling the chain reaction

[cid:image004.jpg@01CD01EA.AD5C6120]

reaction with control rods animation.swf Download this file

Fission for energy.pptm Download this file

DJFPh110chain2.swf Download this file

chain reaction animation.swf Download this file

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7.17 and 7.18

7.17 and 7.18 starter

13 January 2012

14:02

A fuel that doesn’t burn. What is it?

Answers
· Uranium. When Uranium atoms split into two (fission) they release energy which can be captured in a nuclear power station. This is a nuclear reaction and is fundamentally different to burning (combustion is a chemical reaction)

7.17 and 7.18 starter 2

13 January 2012

14:02

How many protons and neutrons are there in
· 23592U?
· 23692U?

Answers
· 23592U = 92 protons; 143 neutrons.

This radioisotope of Uranium is commonly used as a fuel for nuclear power stations
· 23692U = 92 protons; 144 neutrons

This radioisotope of Uranium is highly unstable and is artificially created in nuclear power stations where it undergoes fission

7.17 and 7.18

12 January 2012

10:32
· 7.17 understand that a nucleus of U-235 can be split (the process of fission) by collision with a neutron, and that this process releases energy in the form of kinetic energy of the fission products
· 7.18 recall that the fission of U-235 produces two daughter nuclei and a small number of neutrons
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PhET animation - nuclear fission

31 January 2012

13:34
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Website

http://phet.colorado.edu/en/simulation/nuclear-fission

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U235 fission animation.swf Download this file

Nuclear Fission.pptm Download this file

7.15 and 7.16 Plenary Answers

7.15 and 7.16 Plenary Answers

12 January 2012

10:24
1. How are alpha particles deflected by the "Plum Pudding Model"

[cid:image001.jpg@01CD01E5.DFD5ED10]

The alpha particles are not deflected - they pass straight through

2. How are alpha particles deflected by "Rutherford's Nuclear Model"

[cid:image002.jpg@01CD01E5.DFD5ED10]
· Most alpha particles are undeflected and pass straight through
· Some alpha particles are deflected through a small angle
· A few alpha particles are deflected through a large angle

· What happens if you increase the speed of the alpha particles?

[cid:image003.jpg@01CD01E5.DFD5ED10]

The amount of deflection decreases as the alpha particles have more Kinetic Energy to overcome a greater amount of Electrostatic Potential Energy of their repulsion with the nucleus.

4. What happens if you increase the charge of the nucleus?

[cid:image004.jpg@01CD01E5.DFD5ED10]

The amount of deflection increases as there is now greater electrostatic repulsion between the nucleus and the alpha particle

5. What happens if you increase the number of neutrons in the nucleus?

[cid:image005.jpg@01CD01E5.DFD5ED10]

The amount of deflection is unaffected (increasing the number of neutrons does not affect the charge on the nucleus)

See the full gallery on Posterous

Fw: 7.15 and 7.16

Sent from my BlackBerry® by dtac.

---

From: Matt Baker <maba@patana.ac.th>

Date: Wed, 7 Mar 2012 14:29:10 +0700

To: Andrew Koomenjoe Nyaga<anny14@patana.ac.th>; Arisara Amrapala<aram14@patana.ac.th>; Boondaree Chang<boch14@patana.ac.th>; Chrischawit Chomsoonthorn<chcm14@patana.ac.th>; Christopher Lo<chlo14@patana.ac.th>; Connor Blair Sailes<cosa14@patana.ac.th>; Frazer Allen Briggs<frbr14@patana.ac.th>; Huei-Yu Daniel Lo<hulo14@patana.ac.th>; Isabel Catriona McDonald<ismd14@patana.ac.th>; Kavin Supatravanij<kasu14@patana.ac.th>; Luke Michael Gebbie<luge14@patana.ac.th>; Lydia Anna Foley<lyfo14@patana.ac.th>; Morrakot Sae-Huang<mosa14@patana.ac.th>; Puchawin Borirackujarean<pubo14@patana.ac.th>; Qing Tang<qita14@patana.ac.th>; Sanyam Grewal<sagr14@patana.ac.th>; Sebastien Grimm<segr14@patana.ac.th>; Soo Hyun Lee<sole14@patana.ac.th>; Tatiksha Singh<tasi14@patana.ac.th>; Usa Wongsanguan<uswo14@patana.ac.th>; Yanida Areekul<yaar14@patana.ac.th>; Yi-Lin Huang<yihu14@patana.ac.th>

Subject: 7.15 and 7.16

 

 

7.15 and 7.16 starter

12 January 2012

10:36

·         What is the charge on an alpha particle?

·         What is the charge on the nucleus of a gold atom, ¹⁹⁷₇₉Au?

·         If an alpha particle came close to the nucleus of a gold atom, what would happen?

 

 

 

 

 

 

 

 

 

 

Answers

·         Alpha particle, charge = +2

·         Nucleus of gold atom, charge = +79

·         The positive charge on the alpha particle will repel with the positive charge on the gold nucleus and the alpha particle would be deflected.  Have a look at the animation to see this happening

 

<<alpha particle scattering - atomic structure evidence.swf>>

 

 

7.15 and 7.16

12 January 2012

10:24

·         7.15 describe the results of Geiger and Marsden’s experiments with gold foil and alpha particles

·         7.16 describe Rutherford’s nuclear model of the atom and how it accounts for the results of Geiger and Marsden’s experiment and understand the factors (charge and speed) which affect the deflection of alpha particles by a nucleus

	Alpha particle scattering experiment and the nuclear atom - taken from BBC "The Atom"   Rutherford's Experiment: Nuclear Atom
			<<Alpha particle scattering experiment and the nuclear atom.wmv>>

<<alpha particle scattering.pptx>>

<<DJFPh105rutherford.swf>>

DJFPh105rutherford.swf Download this file

alpha particle scattering.pptx Download this file

alpha particle scattering - atomic structure evidence.swf Download this file

Fw: 7.14

Sent from my BlackBerry® by dtac.

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From: Matt Baker <maba@patana.ac.th>

Date: Wed, 7 Mar 2012 14:28:42 +0700

To: Andrew Koomenjoe Nyaga<anny14@patana.ac.th>; Arisara Amrapala<aram14@patana.ac.th>; Boondaree Chang<boch14@patana.ac.th>; Chrischawit Chomsoonthorn<chcm14@patana.ac.th>; Christopher Lo<chlo14@patana.ac.th>; Connor Blair Sailes<cosa14@patana.ac.th>; Frazer Allen Briggs<frbr14@patana.ac.th>; Huei-Yu Daniel Lo<hulo14@patana.ac.th>; Isabel Catriona McDonald<ismd14@patana.ac.th>; Kavin Supatravanij<kasu14@patana.ac.th>; Luke Michael Gebbie<luge14@patana.ac.th>; Lydia Anna Foley<lyfo14@patana.ac.th>; Morrakot Sae-Huang<mosa14@patana.ac.th>; Puchawin Borirackujarean<pubo14@patana.ac.th>; Qing Tang<qita14@patana.ac.th>; Sanyam Grewal<sagr14@patana.ac.th>; Sebastien Grimm<segr14@patana.ac.th>; Soo Hyun Lee<sole14@patana.ac.th>; Tatiksha Singh<tasi14@patana.ac.th>; Usa Wongsanguan<uswo14@patana.ac.th>; Yanida Areekul<yaar14@patana.ac.th>; Yi-Lin Huang<yihu14@patana.ac.th>

Subject: 7.14

 

 

7.14 starter

01 February 2012

13:08

Tell the person next to you…

·         What is the most dangerous type of radiation outside the body?  Why?

·         What is the most dangerous type of radiation inside the body?  Why?

<<alpha, beta, gamma - effect on human body.pptx>>

<<BBC NEWS  Health  What is polonium-210.mht>>

Answers

·         Gamma radiation is the most dangerous type of radiation outside the body because it is extremely penetrating.  (Alpha radiation is not dangerous because it is stopped by skin)

·         Alpha radiation is the most dangerous type of radiation inside the body because it is highly ionising due to its high charge (+2) and high mass (RAM=4).  (Gamma radiation is only very weakly ionising)

 

 

7.14

12 January 2012

10:24

·         7.14 describe the dangers of ionising radiations, including:

·         radiation can cause mutations in living organisms

·         radiation can damage cells and tissue

·         the problems arising in the disposal of radioactive waste

<<Dangers of radioactivity.pptm>>

Chernobyl Disaster

Hiroshima and Nagasaki - the first nuclear bombs

After the Hiroshima bomb

Dangers of radioactivity.pptm Download this file

alpha, beta, gamma - effect on human body.pptx Download this file

Fw: 7.13

Sent from my BlackBerry® by dtac.

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From: Matt Baker <maba@patana.ac.th>

Date: Wed, 7 Mar 2012 14:28:31 +0700

To: Andrew Koomenjoe Nyaga<anny14@patana.ac.th>; Arisara Amrapala<aram14@patana.ac.th>; Boondaree Chang<boch14@patana.ac.th>; Chrischawit Chomsoonthorn<chcm14@patana.ac.th>; Christopher Lo<chlo14@patana.ac.th>; Connor Blair Sailes<cosa14@patana.ac.th>; Frazer Allen Briggs<frbr14@patana.ac.th>; Huei-Yu Daniel Lo<hulo14@patana.ac.th>; Isabel Catriona McDonald<ismd14@patana.ac.th>; Kavin Supatravanij<kasu14@patana.ac.th>; Luke Michael Gebbie<luge14@patana.ac.th>; Lydia Anna Foley<lyfo14@patana.ac.th>; Morrakot Sae-Huang<mosa14@patana.ac.th>; Puchawin Borirackujarean<pubo14@patana.ac.th>; Qing Tang<qita14@patana.ac.th>; Sanyam Grewal<sagr14@patana.ac.th>; Sebastien Grimm<segr14@patana.ac.th>; Soo Hyun Lee<sole14@patana.ac.th>; Tatiksha Singh<tasi14@patana.ac.th>; Usa Wongsanguan<uswo14@patana.ac.th>; Yanida Areekul<yaar14@patana.ac.th>; Yi-Lin Huang<yihu14@patana.ac.th>

Subject: 7.13

 

 

7.13

12 January 2012

10:24

·         7.13 describe the uses of radioactivity in medical and non-medical tracers, in radiotherapy and in the radioactive dating of archaeological specimens and rocks

<<Uses of radioactivity.pptm>>

Medical Tracers

Radioactive Dating

<<DJFPh106carb2.swf>>

<<DJFPh108dating5.swf>>

Thickness control mill

<<thickness of metal using beta radiation.swf>>

Uses of radioactivity.pptm Download this file

thickness of metal using beta radiation.swf Download this file

DJFPh108dating5.swf Download this file

DJFPh106carb2.swf Download this file

Fw: 7.10 to 7.12 answers

Sent from my BlackBerry® by dtac.

---

From: Matt Baker <maba@patana.ac.th>

Date: Wed, 7 Mar 2012 14:28:12 +0700

To: Andrew Koomenjoe Nyaga<anny14@patana.ac.th>; Arisara Amrapala<aram14@patana.ac.th>; Boondaree Chang<boch14@patana.ac.th>; Chrischawit Chomsoonthorn<chcm14@patana.ac.th>; Christopher Lo<chlo14@patana.ac.th>; Connor Blair Sailes<cosa14@patana.ac.th>; Frazer Allen Briggs<frbr14@patana.ac.th>; Huei-Yu Daniel Lo<hulo14@patana.ac.th>; Isabel Catriona McDonald<ismd14@patana.ac.th>; Kavin Supatravanij<kasu14@patana.ac.th>; Luke Michael Gebbie<luge14@patana.ac.th>; Lydia Anna Foley<lyfo14@patana.ac.th>; Morrakot Sae-Huang<mosa14@patana.ac.th>; Puchawin Borirackujarean<pubo14@patana.ac.th>; Qing Tang<qita14@patana.ac.th>; Sanyam Grewal<sagr14@patana.ac.th>; Sebastien Grimm<segr14@patana.ac.th>; Soo Hyun Lee<sole14@patana.ac.th>; Tatiksha Singh<tasi14@patana.ac.th>; Usa Wongsanguan<uswo14@patana.ac.th>; Yanida Areekul<yaar14@patana.ac.th>; Yi-Lin Huang<yihu14@patana.ac.th>

Subject: 7.10 to 7.12 answers

 

 

7.10 to 7.12 answers

01 February 2012

09:46

1.              What happens to the amount of ‘mother’ nuclei as time passes?

Decrease

2.              What sort of radioisotope will decay the fastest - one with a long half life or one with a short half life?

One with a short half life

3.              Does half life tell us exactly when a particular nucleus in a radioisotope will decay?

No.  It is a random process - we can not know exactly when a particular nucleus will decay

4.              What are the two definitions of half life?

a.                  The time taken for the activity of a sample to halve

b.                  The time taken for the number of radioactive atoms in a sample to halve

5.              What does the activity of a source mean?

The number of decays per second

6.              What is the unit of activity?

Becquerel (Bq)

7.              What will happen to the number of ‘mother’ nuclei after two half lives?

1    è    ½     è    ¼  

     1xhalf life       2xhalf life 

The number of mother nuclei will be ¼ of the original number

8.              What will happen to the activity of a source after two half lives?

1    è    ½     è    ¼  

     1xhalf life       2xhalf life 

The activity will be ¼ of the original activity

 

 

7.10 to 7.12 calculation answers

12 January 2012

10:24

1.              A radioisotope has a half life of 12 years. What fraction of the radioisotope will be left after 60 years?

Fraction remaining:

1    è    ½     è    ¼    è   1/8    è   1/16    è   1/32

1xhalf life       2xhalf life          3xhalf life        4xhalf life          5xhalf life

      12 years        24 years            36 years          48 years            60 years

 

2.              If the activity of a sample falls to 1/64th of its original level after 2 hours, what is the half life of the sample?

 

1  è  ½  è  ¼  è  1/8  è  1/16  è  1/32  è  1/64

      1xhalf life    2xhalf life     3xhalf life      4xhalf life         5xhalf life         6xhalf life

Decay takes 2 hours (= 120 minutes)

This is 6 half lives

So 1 half life = 120 minutes / 6 half lives = 20 minutes

 

3.              The background radiation in a laboratory is 7 Bq. The count rate from a radioisotope is measured and it has a reading of 119 Bq. If the half life of the radioisotope is 10 minutes, what will be the reading 20 minutes later?

 

Initial count rate at detector = 119 Bq

But Background rate = 7 Bq

So activity of radioisotope = 119 – 7 = 112 Bq

 

1  è  ½  è  ¼

      1xhalf life    2xhalf life

    10mins   +  10mins = 20mins

112Bq  è  56Bq  è  28Bq = activity of radioisotope after 20 mins

 

But this doesn’t include the background rate!

Detector reading = 28Bq + 7Bq = 35Bq

 

4.              Potassium decays into argon.  The half life of potassium is 1.3 billion years.  A sample of rock from Mars is found to contain three argon atoms for every atom of potassium.  How old is the rock?

 

Proportion of K:       1  è  ½  è  ¼

Proportion of Ar:      0  è  ½  è  3/4   

                                                   1xhalf life    2xhalf life

So after 2 half lives there will be 3 times as many Ar atoms as K atoms

Age of rocks = 2 x half life = 2 x 1.3x10⁹ = 2.6 billion years