# Difference between revisions of "Introductory Questions and Preparation of the Sample (Introduction to Radiochemistry)"

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==== Lab Exercise and Rapports ==== | ==== Lab Exercise and Rapports ==== | ||

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− | In this exercise you are going to make a sample of uranium, and do measurements which will show the uncertainty in measurements and decide the efficiency of the detector. Be certain that you know how the GM-detector works, before you prepare the uranium sample. You must calculate the amount of uranium needed for the sample. Therefore you should complete the following before preparing the sample. | + | |

+ | [[Introduction to Radiochemistry - Counting statistics|Return]] <br><br>In this exercise you are going to make a sample of uranium, and do measurements which will show the uncertainty in measurements and decide the efficiency of the detector. Be certain that you know how the GM-detector works, before you prepare the uranium sample. You must calculate the amount of uranium needed for the sample. Therefore you should complete the following before preparing the sample. | ||

#Draw the disintegration schematic of the uranium series from <sup>238</sup>U to <sup>230</sup>Th. Write down the half-lives and the type of disintegration. | #Draw the disintegration schematic of the uranium series from <sup>238</sup>U to <sup>230</sup>Th. Write down the half-lives and the type of disintegration. | ||

#Assume that the sample of uranium that you have is one year old. (The uranium is chemically separated from the other elements). Why is <sup>234</sup>Th, <sup>234</sup>Pa and <sup>234</sup> in equilibrium with <sup>238</sup>U, while <sup>230</sup>Th is not. | #Assume that the sample of uranium that you have is one year old. (The uranium is chemically separated from the other elements). Why is <sup>234</sup>Th, <sup>234</sup>Pa and <sup>234</sup> in equilibrium with <sup>238</sup>U, while <sup>230</sup>Th is not. | ||

− | #Show that the amount of <sup>238</sup>U and <sup>234</sup>U is correct with the equilibrium defenition <span class="texhtml">λ</span><sub>1</sub>N<sub>1</sub>=<span class="texhtml">λ</span><sub>4</sub>N<sub>4</sub>. Assume the abundance of the two isotopes will be equal to abundance in natural uranium.<br><math>\frac{H_{1}}{H_{4}}=\frac{N_{1}}{N_{4}}</math> compare this with <math>\frac{T_{1/2}(1)}{T_{1/2}(4)}</math><br> Does this agree with the claim the two isotopes are in equilibrium? | + | #Show that the amount of <sup>238</sup>U and <sup>234</sup>U is correct with the equilibrium defenition <span class="texhtml">λ</span><sub>1</sub>N<sub>1</sub>=<span class="texhtml">λ</span><sub>4</sub>N<sub>4</sub>. Assume the abundance of the two isotopes will be equal to abundance in natural uranium.<br><math>\frac{H_{1}}{H_{4}}=\frac{N_{1}}{N_{4}}</math> compare this with <math>\frac{T_{1/2}(1)}{T_{1/2}(4)}</math><br>Does this agree with the claim the two isotopes are in equilibrium? |

#What is the mass of UO<sub>3</sub> that must be weighted in to get the radioactive sample. Assume that the the counting speed '''R''' should be equal to 100 cps from disintigration of <sup>234</sup>Am and that the counting efficiency is <span class="texhtml">ε</span> = 0.15. | #What is the mass of UO<sub>3</sub> that must be weighted in to get the radioactive sample. Assume that the the counting speed '''R''' should be equal to 100 cps from disintigration of <sup>234</sup>Am and that the counting efficiency is <span class="texhtml">ε</span> = 0.15. | ||

## Revision as of 08:02, 25 September 2012

#### Lab Exercise and Rapports

Return

In this exercise you are going to make a sample of uranium, and do measurements which will show the uncertainty in measurements and decide the efficiency of the detector. Be certain that you know how the GM-detector works, before you prepare the uranium sample. You must calculate the amount of uranium needed for the sample. Therefore you should complete the following before preparing the sample.

- Draw the disintegration schematic of the uranium series from
^{238}U to^{230}Th. Write down the half-lives and the type of disintegration. - Assume that the sample of uranium that you have is one year old. (The uranium is chemically separated from the other elements). Why is
^{234}Th,^{234}Pa and^{234}in equilibrium with^{238}U, while^{230}Th is not. - Show that the amount of
^{238}U and^{234}U is correct with the equilibrium defenition λ_{1}N_{1}=λ_{4}N_{4}. Assume the abundance of the two isotopes will be equal to abundance in natural uranium.

compare this with

Does this agree with the claim the two isotopes are in equilibrium? - What is the mass of UO
_{3}that must be weighted in to get the radioactive sample. Assume that the the counting speed**R**should be equal to 100 cps from disintigration of^{234}Am and that the counting efficiency is ε = 0.15.

#### Preparation of the Sample

- A filter-holder with vacuum suction will be used to make the uranium calibration source. The setup will be demonstrated by your supervisor. Before you start with the uranium, test the setup thoroughly for leaks and other problems (with water).
*All equipment and radioactive material should be in a tray with absorbing paper at the bottom. Non-active equipment and materials should be kept separately. Keep your workspace tidy.* - On the high-precission scale (demonstrated by your supervisor) measure the exact weight of your weighing ship.
- Transfer the calculated amount of uranimoxide to your weighing ship using the laboratory scale (low precision) to control the amount.
- Measure the exact amount of uraniumoxide you have on the high-precission scale by weighing the ship with the oxide. Calculate the exact amount of uraniumoxide you have.
- Transfer the UO
_{3}into the filter-holder setup by flushing out the ship with water. Make sure everything is transfered and try to do it in such a way that the oxide is evenly distributed on the filter. - Apply vacuum to remove the water and leave it on until the uraniumoxide on the filter is reasonably dry.
- A sample holder card (cardboard with a punch-out hole slightly larger than the filterpaper you are going to use) is prepared for holding and sealing the uraniumoxide: Put seven layers of tape on one side such that the hole is completely and securly covered.The seven layers of tape will ensure that low-energy betas will not pass through (why is this important?).
*On the left side is a prepared counting paper with a filter with uraniumoxide taped on. On the right side there is a unprepared filter.* *Disconnect the vacuum suction and "catch" the filter with the tape on the sample holder card. Remove it very carefully, turn it and securly seal the filter/uraniumoxide with tape.**Write your initials, date, and amount of UO*_{3}on the sample card.*Check the sample card holder for surface contamination by using a swipe (your supervisor will explain/demonstrate).**Clean up your workplace and make sure that all radioactive waste is disposed of properly in appropriate waste containers. Update the waste accumulation logs.*