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

From mn/safe/nukwik

(→Lab-exercise and Rapports) |
|||

Line 6: | Line 6: | ||

#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 | + | #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 | + | #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. |

==== Preparation of the Sample ==== | ==== Preparation of the Sample ==== |

## Revision as of 12:25, 3 July 2012

#### Lab-exercise and Rapports

Return to Main

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 is coupled to a water pump. Test it with water first to check if there is a leakage.
*All equipment should be in plastic trays with absorbing paper.* - A preparation paper is prepared with three double layer of tape (in a cross) at one of the sides.
*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.*

- Weigh in the calculated amount of UO
_{3}ca precisely in a weighing ship. Do a rough weighing first on a laboratory weight (50-150 mg). - Transfer the weighed amount of UO
_{3}into the filter-holder use as little as possible water the filter-holder should be filled with water. Try to get the sample as even as possible. - The solution is vacuumed until it is dry and the filter-paper is mounted onto the counting card with seven layers of tape in a cross over the hole. The sample must be completely sealed.