jilebinator
Badges: 12
Rep:
?
#201
Report 6 years ago
#201
Does anyone have the Jan 2013 physics papers?
0
reply
lantern
Badges: 1
Rep:
?
#202
Report 6 years ago
#202
(Original post by jilebinator)
Does anyone have the Jan 2013 physics papers?
There isn't one because there are only June exams for Unit 5
0
reply
vgautam
Badges: 0
Rep:
?
#203
Report 6 years ago
#203
How synoptic is this module? Also can we expect to be assessed on topics on the last module?
0
reply
JRP95
Badges: 2
Rep:
?
#204
Report 6 years ago
#204
(Original post by vgautam)
How synoptic is this module? Also can we expect to be assessed on topics on the last module?
Yeah 10% of the marks on the paper (out of the marks that will get you 120ums minimum) will be synoptic, it could be anything including from the last module although most likely will be something particle physics to do with binding energy I think.
0
reply
fayled
Badges: 2
Rep:
?
#205
Report 6 years ago
#205
Just special relativity left to study but I'm putting it off until I have a few solid days where I can concentrate solely on it.
0
reply
vgautam
Badges: 0
Rep:
?
#206
Report 6 years ago
#206
(Original post by JRP95)
Yeah 10% of the marks on the paper (out of the marks that will get you 120ums minimum) will be synoptic, it could be anything including from the last module although most likely will be something particle physics to do with binding energy I think.
Source?
0
reply
igloo1
Badges: 0
Rep:
?
#207
Report 6 years ago
#207
Can anyone explain to me how nuclear fission reactors work? Thanks!
0
reply
JRP95
Badges: 2
Rep:
?
#208
Report 6 years ago
#208
(Original post by vgautam)
Source?
My physics teacher... The A* questions in the paper are all going to be synoptic.
0
reply
posthumus
Badges: 20
Rep:
?
#209
Report 6 years ago
#209
(Original post by igloo1)
Can anyone explain to me how nuclear fission reactors work? Thanks!
Some nuclear reactors have fuel rods which increase the amount of uranium-235 in the reactor, this increases fission as Uranium-235 readily undergoes fission. This is called enriched nuclear fuel. The downside to this is, that Uranium-235 is rare and it's rate is slow

So there's an alternative method called induced fission...

when the uranium-235 is bombarded with high energy neutrons (this increases fission rate).
When this happens the nuclei is split in half and a number of extra neutrons are increased which may induce further fission reactions. This is known as a chain reaction But the neutrons can do other things too.... they don't always get induced in practice :
  • The neutron may leave the same of uranium without causing any further reactions. This is unlikely in large amounts of uranium however, there's a critical volume from where the fission would be feasible
  • The neutron may even be absorbed by a uranium-238 without causing any further fission, as this is much more stable


Now, the fission needs to be controlled.... because you don't want the rate to be too fast and reactors explode. There's a much greater chance of absorption of the neutron taking place at low speeds.
In a nuclear reactor there are fuel rods containing less critical mass of fissionable uranium, neutrons are emitted from here.
A moderator which usually consists of water at high pressure slows down the neutrons, increasing fission
This may get out of control... so you may want to use control rods These are usually made of boron or cadmium and absorb the neutrons which therefore decrease the rate of fission in the reactor the more you lower them.... the more the rate will decrease. And when you want to increase the rate - just raise the control rods
With all this going on, the moderator may get very hot, so a coolant is pumped around the reactor core.... you want it to have a large specific heat capacity, therefore water can be used for example
1
reply
JoshL123
Badges: 2
Rep:
?
#210
Report 6 years ago
#210
(Original post by posthumus)
Some nuclear reactors have fuel rods which increase the amount of uranium-235 in the reactor, this increases fission as Uranium-235 readily undergoes fission. This is called enriched nuclear fuel. The downside to this is, that Uranium-235 is rare and it's rate is slow

So there's an alternative method called induced fission...

when the uranium-235 is bombarded with high energy neutrons (this increases fission rate).
When this happens the nuclei is split in half and a number of extra neutrons are increased which may induce further fission reactions. This is known as a chain reaction But the neutrons can do other things too.... they don't always get induced in practice :
  • The neutron may leave the same of uranium without causing any further reactions. This is unlikely in large amounts of uranium however, there's a critical volume from where the fission would be feasible
  • The neutron may even be absorbed by a uranium-238 without causing any further fission, as this is much more stable


Now, the fission needs to be controlled.... because you don't want the rate to be too fast and reactors explode. There's a much greater chance of absorption of the neutron taking place at low speeds.
In a nuclear reactor there are fuel rods containing less critical mass of fissionable uranium, neutrons are emitted from here.
A moderator which usually consists of water at high pressure slows down the neutrons, increasing fission
This may get out of control... so you may want to use control rods These are usually made of boron or cadmium and absorb the neutrons which therefore decrease the rate of fission in the reactor the more you lower them.... the more the rate will decrease. And when you want to increase the rate - just raise the control rods
With all this going on, the moderator may get very hot, so a coolant is pumped around the reactor core.... you want it to have a large specific heat capacity, therefore water can be used for example
Does it not, the fuel rods, contain more than the critical mass of Uranium 235? Otherwise the surface area to mass ratio would result in nuetrons escaping and so self induced fission cannot occur. And I also thought that uranium 235 is not rare. I thoguht of the naturally occuring form approximately 97-98 percent was Uranium 235 while the 2-3 percent was Uranium 238 Please corrext me if I am wrong

Posted from TSR Mobile
0
reply
JoshL123
Badges: 2
Rep:
?
#211
Report 6 years ago
#211
(Original post by JRP95)
My physics teacher... The A* questions in the paper are all going to be synoptic.
Durka durka durka

Posted from TSR Mobile
0
reply
posthumus
Badges: 20
Rep:
?
#212
Report 6 years ago
#212
(Original post by JoshL123)
Does it not, the fuel rods, contain more than the critical mass of Uranium 235? Otherwise the surface area to mass ratio would result in nuetrons escaping and so self induced fission cannot occur. And I also thought that uranium 235 is not rare. I thoguht of the naturally occuring form approximately 97-98 percent was Uranium 235 while the 2-3 percent was Uranium 238 Please corrext me if I am wrong

Posted from TSR Mobile
Ah damn, it's been so long since I've done this.... can't remember exactly but I think the reason is, if your fuel rod themselves have more uranium than the critical mass then you will have a fuel rod exploding after you've made the rod... which is kind of useless and dangerous I guess
My teacher use the example of an atomic bomb, there were 2 pieces of uranium/plutonium... less than the critical mass - when they are pushed together then the fission occurred

So yup you are correct, in the reactor they probably do exceed critical mass for fission to occur, but the rods themselves are less than critical mass.

And no, over 99% of natural uranium is uranium-238
0
reply
jon.c
Badges: 0
Rep:
?
#213
Report 6 years ago
#213
Does anyone have the mark scheme for the 2012 paper?? Thanks
0
reply
JoshL123
Badges: 2
Rep:
?
#214
Report 6 years ago
#214
(Original post by posthumus)
Ah damn, it's been so long since I've done this.... can't remember exactly but I think the reason is, if your fuel rod themselves have more uranium than the critical mass then you will have a fuel rod exploding after you've made the rod... which is kind of useless and dangerous I guess
My teacher use the example of an atomic bomb, there were 2 pieces of uranium/plutonium... less than the critical mass - when they are pushed together then the fission occurred

So yup you are correct, in the reactor they probably do exceed critical mass for fission to occur, but the rods themselves are less than critical mass.

And no, over 99% of natural uranium is uranium-238
I kind of see what you mean. I just thought that given that Uranium 238 is non-fissionable we do not really really refer to as critical mass being of importance as it is not fissile. However given the Uranium 235 is fissile critical mass is of importance. Ah yes, thats an experiment Feynman did with his students at university but when he pushed the pieces of Uranium together it gave a small explosion :P! Ah yes I remember now! Getting my figures muddled up :L
0
reply
posthumus
Badges: 20
Rep:
?
#215
Report 6 years ago
#215
(Original post by JoshL123)
I kind of see what you mean. I just thought that given that Uranium 238 is non-fissionable we do not really really refer to as critical mass being of importance as it is not fissile. However given the Uranium 235 is fissile critical mass is of importance. Ah yes, thats an experiment Feynman did with his students at university but when he pushed the pieces of Uranium together it gave a small explosion :P! Ah yes I remember now! Getting my figures muddled up :L
Ah cool, I need to check that out !
0
reply
Pinkhead
Badges: 14
Rep:
?
#216
Report 6 years ago
#216
How is revision going, guys? I kind of miss posting after all the time I spent here during Jan exams.

I'm only going to start doing any work for this after my S2 exam on the 24th though. I've got far too many maths exams to be worrying about .
0
reply
posthumus
Badges: 20
Rep:
?
#217
Report 6 years ago
#217
(Original post by Pinkhead)
How is revision going, guys? I kind of miss posting after all the time I spent here during Jan exams.

I'm only going to start doing any work for this after my S2 exam on the 24th though. I've got far too many maths exams to be worrying about .
Haven't really started revising at home or doing past papers, in pretty much the same situation... will be starting after 24th (C2 exam). I have 5 exams this month & 8 next month

Best of luck with yours exams though !
0
reply
Pinkhead
Badges: 14
Rep:
?
#218
Report 6 years ago
#218
(Original post by posthumus)
Haven't really started revising at home or doing past papers, in pretty much the same situation... will be starting after 24th (C2 exam). I have 5 exams this month & 8 next month

Best of luck with yours exams though !
13 exams?! Retakes I assume?

I thought I had it bad but you have twice mine! Good luck to you too
0
reply
S1L3NTPR3Y
Badges: 13
Rep:
?
#219
Report 6 years ago
#219
PHYA5D is my last exam but I've started doing some revision already as I know that I will be pressed for time once my exams get under way. The Unit 5 Core material (Nuclear & Thermal/Gas Laws) isn't too bad. I am doing Turning Points as optional topic, done most of it but still need to finish wave particle duality; the maths side of isn't hard but the written questions can be tough, especially the 6 mark ones. My plan is to do loads of past paper questions, and to make up for the fact that there are only 3 papers (+1 if you count specimen); I've downloaded AQA PHAW8 papers from Jan 2002 to June 2008 which cover Nuclear & Turning points, they seem almost identical to the current specification.
0
reply
ehtisham_1
Badges: 0
Rep:
?
#220
Report 6 years ago
#220
There's al
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • Bournemouth University
    Midwifery Open Day at Portsmouth Campus Undergraduate
    Wed, 16 Oct '19
  • Teesside University
    All faculties open Undergraduate
    Wed, 16 Oct '19
  • University of the Arts London
    London College of Fashion – Cordwainers Footwear and Bags & Accessories Undergraduate
    Wed, 16 Oct '19

How has the start of this academic year been for you?

Loving it - gonna be a great year (128)
18.18%
It's just nice to be back! (193)
27.41%
Not great so far... (251)
35.65%
I want to drop out! (132)
18.75%

Watched Threads

View All