Test examination

RPO MR-b

Tag one of the four alternatives (a, b, c or d) for each of the multiple-choice questions. Only one answer is correct. For the open questions 41 and 42, the complete calculations must be attached.

The examination is based on the syllabus Health physics for radiation protection officers - measurement and control applications - sealed radioactive sources, written by F. Pleiter and H.F. Boersma. You will find the correct answers here .

Complete the sentence correctly : The number of electrons in an electrically neutral atom is equal to the...
1. neutron number
2. atomic number
3. mass number
4. difference between mass number and atomic number
Complete the sentence correctly: The two nuclides ¹⁸ ₉F and ¹⁹ ₉F...
1. are isotopes
2. are isomers
3. have the same mass number
4. none of the answers [a], [b] and [c] is correct
A radioactive source contains an activity of 1 MBq. After a period of 20 weeks, the remaining activity turns out to be 1 kBq. What is the half-life?
1. about 1 week
2. about 10 days
3. about 2 weeks
4. about 20 weeks
The results of an activity measurement are plotted in Figure A . It shows the count rate (vertical scale) as a function of the elapsed time in seconds (horizontal scale). Answer the next question.
What is the half-life of this radionuclide?
1. about 15 seconds
2. about 25 seconds
3. about 55 seconds
4. about 100 seconds
The radionuclide ²¹⁰ ₈₄Po decays by α-emission. Which is the daughter nuclide?
1. ²⁰⁸ ₈₀Hg
2. ²⁰⁶ ₈₀Hg
3. ²⁰⁶ ₈₂Pb
4. ²⁰⁸ ₈₂Pb
First, carefully examine the decay scheme of the nuclide ^115mIn and then answer the next question.
Which of the following statements is correct?
1. ^115mIn is a pure ß-emitter
2. ¹¹⁵In is a pure ß-emitter
3. there is no isomeric state of¹¹⁵In
4. ¹¹⁵Sn is radioactive
What happens during the photo-electric effect?
1. the energy of a ß-particle is transferred to an electron
2. a photon is absorbed by an electron
3. a photon loses part of its energy
4. a photon is scattered
Complete the sentence correctly: The probability of the photo-electric effect to occur...
1. increases if the atomic number of the material becomes larger
2. hardly depends on the atomic number of the material
3. increases if the photon energy becomes higher
4. hardly depends on the photon energy
What is the range in air of 5 MeV α-particles?
1. a few micrometers
2. a few millimeters
3. a few centimeters
4. a few meters
Which is the maximum range in air of 1 MeV ß-particles?
1. about 0.4 cm
2. about 4 cm
3. about 40 cm
4. about 400 cm
What is accounted for by the build-up factor B ?
1. the contribution of scattered radiation to the dose
2. the accumulation of repeated external radiation doses
3. the accumulation of several internal contaminations
4. the accumulation of several radioactive surface contaminations
The nuclide ³²P is a pure ß^--emitter with a maximum energy of 1.71 MeV. A ³²P source is sealed inside plexiglass with a thickness of 1 mm. The specific mass of plexiglass is 1.2 g/cm³.
Which ³²P-produced radiation is transmitted by this enclosure?
1. no radiation
2. only ß-radiation
3. only annihilation radiation
4. both ß-radiation and annihilation radiation
Which is the least effective material for shielding neutrons?
1. water
2. polythene
3. paraffin
4. lead
In an organ with a mass of 100 grams, an energy of 2 joules is deposited by X-rays.
How high is the absorbed dose in that organ?
1. 0.02 Gy
2. 0.05 Gy
3. 20 Gy
4. 50 Gy
Complete the sentence correctly: The tissue weighting factor w_T is used for the conversion from...
1. only equivalent dose to effective dose
2. only absorbed dose to equivalent dose
3. neither equivalent dose to effective dose nor absorbed dose to equivalent dose
4. both equivalent dose to effective dose and absorbed dose to equivalent dose
A worker at a particle accelerator has been exposed to an absorbed γ-dose of 1.0 mGy and an absorbed neutron dose of 0.5 mGy. The radiation weighting factor of the involved neutrons is w_R = 8.
What is the received equivalent dose?
1. 1 mSv
2. 1.5 mSv
3. 4 mSv
4. 5 mSv
Complete the sentence correctly: A large value of e(50) implies...
1. a large radiotoxicity
2. a small radiotoxicity
3. that the activity is slowly removed from the body by excretion
4. that the activity is quickly removed from the body by excretion
Almost half of the radiation dose due to natural sources in the Netherlands is caused by a single type of source.
Which type of radiation source is this?
1. soil
2. cosmic radiation
3. radon
4. food
For which application can a Geiger-Müller counter be used?
1. to measure the energy of α-particles
2. to measure the energy of ß-particles
3. to measure the energy of γ-fotons
4. for none of the applications named at [a], [b] and [c]
Each interaction of a γ-ray photon with the detector material produces an electrical signal at the output of a NaI detector.
Complete the sentence correctly: At a fixed setting of the electronic equipment, the pulse height of this electrical signal is proportional to the...
1. intensity of the radiation
2. energy transferred to NaI
3. number of incoming photons
4. inverse of the square of the distance between source and detector
Which detector can in principle be used as a dose-rate monitor?
1. proportional counter
2. Geiger-Müller counter
3. NaI detector
4. any of the detectors named at [a], [b] and [c]
You want to measure the equivalent dose rate of a ß-source. The maximum ß-energy is 1 MeV.
Which detector is the best choice in this case?
1. end-window Geiger-Müller counter that displays the counting rate in counts per second
2. Geiger-Müller counter with an all-sided mass wall-thickness of 1 g/cm², that is calibrated in mSv/h
3. proportional counter with a mass window-thickness of 7 mg/cm², that displays µSv/h
4. proportional counter with an all-sided mass wall-thickness of 1 g/cm², that is calibrated in mSv/h
The electronic output signals of a detector can be sorted according to pulse height in a so-called multi-channel analyser, which makes it possible to display the energy distribution (= spectrum) of the radiation on a monitor.
For which type of measurement is a multi-channel analyser never used?
1. activity measurement
2. dose rate measurement
3. contamination measurement
4. γ-ray spectrometry
In which type of tissue are cells most sensitive to ionizing radiation
1. tissue that receives the largest dose
2. tissue that is located in the abdominal region
3. tissue with cells that no longer divide
4. tissue with cells that divide quickly
Which effect of ionizing radiation occurs with a probability that is not proportional to the received radiation dose?
1. a genetic effect
2. a stochastic effect
3. a tissue reaction
4. leukemia
Which disease can be regarded as a stochastic effect due to ionizing radiation?
1. leukemia
2. permanent sterility
3. temporary sterility
4. reduction in the number of white blood corpuscles
An unborn child receives an absorbed dose of 0.5 Gy during the first ten days after the conception.
What is the possible consequence of this irradiation for the child?
1. a tumor in later life
2. malformation of an organ
3. death shortly after birth
4. prenatal death
Which is the risk coefficient for fatal stochastic effects due to ionizing radiation?
1. about 0.01 per sievert
2. about 0.02 per sievert
3. about 0.05 per sievert
4. about 0.10 per sievert
What does the ALARA principle mean?
1. preference for any alternative method in which no ionizing radiation is applied
2. the received dose must be kept as low as reasonably achievable
3. the application must be justified, which means that the benefits outweigh the disadvantages
4. no dose limit shall be violated
According to the Decree on Basic Safety Standards Radiation Protection, which is the annual limit for the effective dose of an exposed category-A worker?
1. 100 μSv
2. 2 mSv
3. 20 mSv
4. 50 mSv
According to the Decree on Basic Safety Standards Radiation Protection, which is the annual limit for the equivalent dose on the lens of the eye of an exposed category-A worker?
1. 20 mSv
2. 50 mSv
3. 150 mSv
4. 500 mSv
According to the Decree on Basic Safety Standards Radiation Protection, an area in which ionizing radiation is applied must be designated as a supervised or controlled area. The criterion for this is the maximaum effective annual dose that may be received in this area.
What criterion must the effective annual dose in a supervised area meet?
1. higher than 1 mSv, but lower than 6 mSv
2. higher than 6 mSv, but lower than 10 mSv
3. higher than 10 mSv, but lower than 20 mSv
4. higher than 20 mSv

Does a risk inventory and evaluation (RI&E) always have to be carried out by the radiation protection officer?

yes
no, this may only be done by a registered radiation protection expert
no, this may only be done by radiation protection experts
no, this may in principle be done by everyone

According to the Decree on Basic Safety Standards Radiation Protection, a radioactive substance is exempt from government control if either the activity or the activity concentration is lower than the exemption values for moderate quantities (up to 1000 kg).

nuclide	activity (Bq)	activity concentration (Bq/g)
³H	10⁹	10⁶
¹⁴C	10⁷	10⁴
¹³¹I	10⁶	10²
²²⁶Ra	10⁴	1
²⁴¹Am	10⁴	1

Consider the exemption values in the above table.

Which of the following radioactive substances, each less than 1000 kg, is not exempt?
1. 6×10⁸ Bq ³H with an activity concentration of 6×10⁷ Bq/g
2. 3.7×10⁶ Bq ¹³¹I with an activity concentration of 3×10² Bq/g
3. 3.7×10³ Bq ²²⁶Ra with an activity concentration of 3.7×10¹⁰ Bq/g
4. 3×10³ Bq ²⁴¹Am with an activity concentration of 3×10⁹ Bq/g
The ISO-classification code of a sealed source consists of the letter C followed by five digits, each referring to a specific test on the items temperature and thermic shock, pressure, mechanical shock, vibration, and puncture. The value of the digit represents the strength of the test to which the source was subjected.
Complete the sentence: A sealed ⁶³Ni source with ISO-classification code 32211, used in a gas chromatograph, has been tested on...
1. all items
2. all items, with the most severe test for temperature
3. all items, with the most severe test for vibration and puncture
4. not all items
The radiation protection officer has a number of tasks relating to practices with sealed sources.
What belongs to these tasks?
1. introducing new employees into the house rules
2. introducing new employees into the written instructions
3. introducing new employees into both the house rules and the written instructions
4. none of the tasks named at [a] and [b] because they are reserved to the radiation protection expert
Which of the following precautions must ensure that sealed sources do not get lost?
1. a suitable record of the use of all sources
2. raising awareness among workers about the risk of theft
3. storage of the source in a vault when it is not in use
4. all precautions named at [a], [b] and [c]
In a set-up for X-ray fluorescence, a source containing the nuclide ⁵⁷Co is used. The equivalent dose rate at 1 meter from this source is 85 μSv per hour. The source constant of ⁵⁷Co is h = 0.023 μSv·m^2·MBq^-1·h^-1.
What is the activity of this source?
1. 3.7 MBq
2. 37 MBq
3. 0.37 GBq
4. 3.7 GBq
Point source A emits only γ-photons with an energy of 500 keV and point source B emits only β-particles with an average energy of 500 keV. Both sources contain the same amount of activity and absorption of radiation is negligible.
Which of the following statements is correct?
1. A gives rise to a much lower skin-dose rate than B
2. A and B give rise to approximately equal skin-dose rates
3. A gives rise to a slightly higher skin-dose rate than B
4. A gives rise to a much higher skin-dose rate than B
An old smoke detector containing 33 kBq ²⁴¹Am is disposed of by dropping it into the waste bin. A little child finds the smoke detector, takes it apart, and ingests an estimated 10% of the original activity. The dose conversion coefficient for ingestion of ²⁴¹Am is 2.0×10^-7 Sv/Bq.

Which is the committed effective dose for the child due to this contamination?

about 0.007 mSv
about 0.07 mSv
about 0.7 mSv
about 7 mSv

To answer questions 41 and 42, the full calculation must be given. Clearly indicate the calculation method and/or reasoning you use to arrive at the solution. Always state the quantities and units used.

Data for question 41
dimensions of box	40 cm × 40 cm × 40 cm
activity	4 GBq ¹³⁷Cs
source constant	0.093 μSv·m²·MBq^-1·h^-1
transmission lead container	0.1 s

The RPO prepares a box in which a radioactive source will be sent. The source is packaged in a lead container to ensure that the equivalent dose rate on the surface of the box is nowhere higher than the maximum allowable value. The lead pot is placed in the center of the box.

calculate the equivalent dose rate on the surface of the box
(maximal 4 points).

Data for question 42
activity	100 GBq
source constant	0.12 μSv m² MBq^-1 h^-1
length pair of tongues	50 cm
exposure time	10 s
the RPO is classified as exposed A-worker

During inspection of welds, a sealed ¹⁹²Ir source falls on the street. The source is returned to the lead container by the RPO using a pair of tongues.

1. calculate the effective dose received by the RPO
2. calculate the time that the job should have lasted until the annual limit for the effective dose of this worker is reached
(maximal 6 points)

Last modified:11 December 2025 2.57 p.m.

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Test examination

To answer questions 41 and 42, the full calculation must be given. Clearly indicate the calculation method and/or reasoning you use to arrive at the solution. Always state the quantities and units used.

Data for question 41