DP Physics (first assessment 2025)

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Question EXE.2.HL.TZ0.21

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Date Example questions Example questions Marks available [Maximum mark: 9] Reference code EXE.2.HL.TZ0.21
Level HL Paper 2 Time zone TZ0
Command term Calculate, Determine, Discuss, Suggest Question number 21 Adapted from N/A
21.
[Maximum mark: 9]
EXE.2.HL.TZ0.21
(a)

Suggest one problem that is faced in dealing with the waste from nuclear fission reactors. Go on to outline how this problem is overcome.

[2]

Markscheme

Waste is very hot …

… So has to be placed in cooling ponds to transfer the (thermal) energy away ✓

 

OR

Waste is very radioactive … ✓

… So has to be placed in cooling ponds to absorb this radiation

OR

… So has to be handled remotely

OR

… So has to be transported in crash resistant casings / stored on site ✓

 

OR

Waste will be radioactive for thousands of years … ✓

… So storage needs to be (eventually) in geologically stable areas ✓

(b)

Strontium-90 is a waste product from nuclear reactors that has a decay constant of 7.63 x 10−10 s−1. Determine, in s, the time that it takes for the activity of strontium-90 to decay to 2% of its original activity.

[2]

Markscheme

ln 0.02=-7.63×10-10t or equivalent seen ✓

t=5.1 Gs ✓

(c)

The decay of one Strontium-90 nucleus leads to an energy release of about 0.52 MeV. The decay product of Strontium-90 is Yttrium-90 which itself decays to stable Zirconium-90 with a decay constant of 3.0 x 10−6 s−1. The energy released in the decay of one Yttrium-90 nucleus is 2.3 MeV.

(c.i)

Calculate the energy released when one mole of strontium-90 decays to 2% of its original activity forming the stable daughter product.

[3]

Markscheme

Idea that the Yttrium half life is much less than Strontium so can assume all Yttrium energy is included. ✓

0.98×6.02×1023×0.52+2.3×106 seen ✓

=1.67×1030 eV

Answer ×1.6×10-19=270 GJ ✓

(c.ii)

Strontium-90 decays to Zirconium-90 via two successive beta emissions. Discuss whether all the energy released when strontium-90 decays to Zirconium-90 can be transferred to a thermal form.

[2]

Markscheme

(No)  
(anti-)neutrinos are released in (both) decays ✓

Carrying away energy because they interact poorly with matter ✓

 

Ignore arguments relating to energy transferred to nucleus as this appears eventually as thermal energy.

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