Higher -o-o-o- Past Paper questions o-o-o- 3.6 Radiation

Transcription

1 Higher -o-o-o- Past Paper questions o-o-o- 3.6 Radiation

2 1992 Q35 A typical reaction produced in the core of a nuclear reactor can be described by the following equation: (a) State the name given to the above type of reaction. (b) Large amounts of kinetic energy are released in this reaction. Explain how this kinetic energy is produced Q37 In a famous experiment to investigate the structure of the atom, a beam of radiation is directed at a thin, gold foil target as shown in the diagram below. The experiment shows that most of the radiation passes through the gold foil but some "bounces back" without passing through the foil. (a) State the type of radiation used. (b) Explain how the results of the experiment suggest that the mass of the atom is concentrated at its centre (nucleus) Q37 Energy is produced within the Sun by fusion reactions. (a) State what is meant by a fusion reaction. (b) Explain briefly why a fusion reaction releases energy.

3 1999 Q36 Energy is released from stars as a result of nuclear reactions. One of these reactions is represented by the statement given below. (a) What type of nuclear reaction is described by this statement? (b) Explain why this reaction results in the release of energy. You should make reference to an equation in your explanation Q37 Ernest Rutherford arranged for alpha particles to be fired at a thin gold foil. Apparatus similar to that shown below was used. (a) Most of the alpha particles passed straight through the foil. What does this suggest about the structure of atoms of gold? (b) A small but significant number of alpha particles were scattered through angles greater than 90º. What two features about the nucleus does this suggest? 2001 Q37 A gamma ray source is stored in a lead container. The corrected count rate just outside the container due to the radiation from the source is 250 counts per minute. Without the lead container, the corrected count rate at the same distance from the source is 1000 counts per minute. The lead wall of the container has a thickness of 22.4 mm. Calculate the half-value thickness of the lead.

4 1991 Q12 (a) The following describes a typical fission reaction. (i) Determine x, Y and z in. the equation. (You may have to refer to the Data Booklet.) (ii) Account for the release of energy in this fission process. (b) Radiation from a nuclear reactor can affect human tissue. A health physicist is investigating the effect of a neutron beam and a gamma my beam on some human tissue. A lead shield of half value thickness 12 mm can be placed in the gamma ray beam. The health physicist records the following data: (i) Using the values from the table, calculate the thickness of the lead shield used. (ii) Show that the dose equivalent rate of the neutron beam is 4 times that of the shielded gamma ray beam.

5 1992 Q11 Smoke detectors are important in giving early warning of fire starting in the home. (a) The simplified layout of one type of smoke detector is illustrated below. The following is an extract from the manufacturer's data sheet. "The detector uses a low energy source of ionising radiation, 30 kbq Americium 241, which causes ionisation of the air molecules, and hence a small current between the electrodes. When smoke particles enter the space between the electrodes, they impede the flow of ions and the current is reduced. When the current falls below a certain value, the buzzer sounds." (i) The symbol for the radioactive source used is What information is given by the numbers 95 and 241? (ii) What is meant by "30 kbq"? (iii) Explain what is meant by "ionising radiation". (iv) The equation for the decay of this source is Identify the type of radiation emitted in this decay and explain why this particular type of radiation is used in the smoke detector. (v) The half-life of Americium 241 is 458 years. Discuss the advantage of using this source compared to one with a half-life of 5 years. (b) The workers in the factory assembling this type of smoke detector will experience a higher radiation dose equivalent than that due to background radiation alone. (i) State one factor contributing to background radiation. (ii) It is recommended that the workers assembling the smoke detectors should not receive a dose equivalent rate greater than 5.0 msv per year above the background level. A worker in a factory making smoke detectors assembles detectors in a year. An absorbed dose of 1.2x10-8 Gy is received by the worker in assembling one detector and the quality factor of the radiation is 20. Show, by calculation, whether the permissible level of 5.0 msv per year will be exceeded for the worker.

6 1993 Q11 (a) A certain radioactive source emits only gamma radiation. A technician is asked to determine the half-value thickness of lead for the radiation from this source. The technician sets up the apparatus shown below and keeps the distance between the source and the gamma ray detector the same throughout the experiment. The technician measures the count rate several times for a certain thickness of lead sheet, and obtains an average value for the count rate. The measurements are repeated with several different thicknesses of lead sheet and also with no lead present. The source and the lead are then removed and the background count rate is measured. The technician corrects each average count rate for background and records the results as shown in the table. (i) Draw a graph of corrected average count rate against thickness of lead sheet, using the squareruled paper provided. Find the half-value thickness of lead for this source. (ii) On the same axes, sketch a graph which might be obtained if the average count rate was not corrected for background radiation. (b) 21 years later, another technician repeats the experiment with the same source. The gamma ray source has a half-life of 5.25 years. What corrected average count rate would be recorded with no lead sheet between the source and the detector?

7 1994 Q11 A nuclear medicine laboratory contains a small radioactive source in a scaled container. The following information is displayed on the label. (a) When the source has the activity stated on the label, how many nuclei decay in one minute? (b) A technician needs to work at a distance of 1 m from a freshly prepared source. For what period of time can the technician work at this distance so that the absorbed dose does not exceed 50 µgy? (c) Lead shielding is used around the source to reduce the dose equivalent rate at a distance of 1 m to 2.5 µsvh -1. (i) On the square ruled paper provided, draw a graph to show how the dose equivalent rate at a distance of one metre varies with the thickness of lead shielding. (ii) Use your graph to estimate the thickness of lead needed to provide the required level of shielding.

8 (d) A gamma ray source is often transported in a cardboard container carried by two Porters. The source is inside a small lead pot surrounded by, a large volume of polystyrene packaging. The lead pot provides shielding. What other feature of this packaging system reduces the dose equivalent rate for the porters? Give a reason for your answer Q11 The following statement represents a nuclear reaction which may form the basis of a nuclear power station of the future. (a) State the name given to the above type of nuclear reaction. (b) Explain, using E = mc 2, how this nuclear reaction results in the production of energy. (c) Using the information given below, and any other data required from the Data Sheet, calculate the energy released in the above nuclear reaction. (d) Calculate how many of the reactions of the type represented above would occur each second to produce a power of 25 MW.

9 1996 Q10 In investigating the effect of different types of radiation on the human body, the data in the table below was obtained for one particular type of body tissue. (a) Show, using the data in the table, which radiation is likely to be the most harmful to this tissue. (b) (i) The maximum permitted dose equivalent for this tissue is 5 msv. Calculate the time the tissue can be exposed to fast neutrons without exceeding this limit. (ii) A sample of this tissue has a mass of 25 grams. How much energy will it absorb from fast neutrons in 2 hours? (c) The effect of radiation on tissue can be reduced by putting shielding material between the source of radiation and the tissue. The effectiveness of this shielding material can be described by the halfvalue thickness of the material. (i) Explain the meaning of "half-value thickness". (ii) The half-value thickness for a particular material is 7 mm. A block of this material of thickness 3.5 cm is inserted between the source and the tissue. What fraction of the radiation which is directed at the tissue is received by the tissue?

10 1996 Q11 (a) Two possible nuclear reactions involving uranium are represented by the statements shown below. The masses of the nuclei and particles involved in the reactions are as follows. (i) What type of nuclear reaction is described by statements A and B? (ii) Show by calculation how much mass is "Lost" in each of reactions A and B. (iii) Explain which of the reactions A and B releases the greater amount of energy. (b) A third possible nuclear reaction involving is represented by the following statement. (i) The symbol for the uranium nucleus is What information about the particles in the nucleus is provided by the numbers 92 and 235? (ii) Determine the number represented by y.

11 1997 Q11 (a) The diagram shows the apparatus used by Rutherford to investigate the scattering of alpha particles by a gold foil. From the observations made as the microscope and screen were moved from P to Q, Rutherford deduced that an atom has a nucleus which is: (A) positively charged; (B) massive; (C) much smaller than the volume of the atom. Explain how the observations from the scattering experiment led to these three deductions. (b) A pupil reads in a textbook about the possible effects of a source of gamma rays and neutrons on one type of body tissue. A table in the textbook provided information relating to the radiations and absorbed doses for this body tissue. This table is shown below. (i) Calculate the total dose equivalent received by the body tissue. (ii) Calculate the thickness of lead which would have to surround the above source to reduce the absorbed dose from the gamma rays to 25 µgy. The half-value thickness of lead for the gamma radiation is 8 mm.

12 1998 Q11 (a) The first three stages in a radioactive decay series are shown below. (i) What particle is emitted when Thorium (Th) decays to Palladium (Pa)? (ii) How many neutrons are in the nuclide represented by (iii) In the next stage of the above decay series, an alpha particle is emitted. Copy and complete this stage of the radioactivity decay series shown below, giving values for a, b, c and d, and naming the element X.

13 (b) The following graph shows how the effective dose equivalent rate due to background radiation varies with height above sea level. (i) Name two sources of background radiation. (ii) The graph shows that there is an increase in effective dose equivalent rate at altitudes greater than 4 km. Suggest a reason for this increase. (iii) An aircraft makes a 7 hour flight at a cruising altitude of 10 km. (A) Calculate the effective dose equivalent received by a passenger during this flight. (B) A regular traveller makes 40 similar flights in one year and spends the rest of the year at sea level. Calculate the effective dose equivalent of background radiation received by this traveller in that year.

14 1999 Q12 (a) The radiology department in a hospital uses radioactive iodine to examine the functioning of the thyroid gland in a patient. Radioactive iodine is produced by a nuclear reaction when the nuclei of Tellurium atoms absorb neutrons. The statement for this reaction is shown below. State the type of radiation emitted in this reaction. (b) The thyroid gland of the patient receives an absorbed dose of 750 µgy of radiation from the radioactive iodine. (i) Calculate the total energy absorbed if the gland has a mass of 0.04 kg. (ii) The average dose equivalent rate for the gland is 12.5 µsvh -1. The radioactive iodine is present in the gland of the patient for 120 hours. What is the quality factor of the radiation? (c) A source of gamma radiation is stored inside a cabinet in a room where background radiation is negligible. The count rate outside the cabinet is 1200 counts per minute. The cabinet is now lined with lead 24 mm thick. The lead has a half-value thickness of 8 mm for the radiation. What is the new count rate outside the cabinet?

15 2000 Q12 (a) Part of a radioactive decay series is shown below. (i) In what way is the nuclide represented by different from the nuclide represented by (ii) Write down one decay from the above series which involves the emission of a beta particle. (iii) Why is it not possible to tell from the decay series above whether gamma radiation is emitted at any stage? (b) A particular nuclear reaction can be described by the following statement. (i) State the name given to the above type of nuclear reaction. (ii) The masses of the nuclides and particle involved in the nuclear reaction are as shown in the table. Calculate the energy available from the above reaction.

16 2001 Q12 (a) Three stages of a radioactive decay series are shown below. (i) Name the type of radiation involved in stage 1. (ii) Name the type of radiation involved in stage 2. (iii) In stage 3, what are the numerical values of x and y? (b) A sample of body tissue is exposed to two types of radiation for the same length of time. Information on these radiations and the absorbed dose is shown below. (i) Calculate the total dose equivalent received by this tissue. (ii) Which of the above radiations is potentially the more harmful? You must justify your answer.