NRRPT Prep Complete Study Guide 2025/2026 Full Practice Examination (190+ Questions)

NRRPT Prep Complete Study Guide
2025/2026
Full Practice Examination (190+
Questions)

Section 1: Radiation Fundamentals (Questions 1–25)
1. What is the activity of 1 gram of pure radium-226?
A. 1 Ci
B. 3.7 × 10¹⁰ Bq
C. 1 mCi
D. 3.7 × 10³ Bq
Correct Answer: A
Rationale: 1 g of Ra-226 has an activity of approximately 1 Ci (3.7 × 10¹⁰ Bq) by
definition. Option B is numerically equivalent but expressed in Bq; the question
asks for activity in Ci, so A is correct.
2. The half-life of Cs-137 is approximately:
A. 2 years
B. 5 years
C. 30 years
D. 5730 years
Correct Answer: C
Rationale: Cs-137 has a half-life of about 30.17 years. Co-60 is 5.27 years, C-14 is
5730 years.
3. Which type of radiation has the highest linear energy transfer (LET)?
A. Gamma
B. Beta
C. Alpha
D. Neutron (fast)

,Correct Answer: C
Rationale: Alpha particles have high LET (~100 keV/μm) due to their double
charge and mass, causing dense ionization. Gamma and beta are low-LET.
4. The energy of a photon with wavelength 0.01 Å is approximately:
A. 1.24 keV
B. 12.4 keV
C. 124 keV
D. 1.24 MeV
Correct Answer: D
Rationale: E (keV) = 12.4 / λ(Å) = 12..01 = 1240 keV = 1.24 MeV.
5. 1 Roentgen (R) produces in air:
A. 1 Gy
B. 1 Sv
C. 2.58 × 10⁻⁴ C/kg
D. 1 rad
Correct Answer: C
Rationale: 1 R = 2.58 × 10⁻⁴ C/kg in air. 1 R ≈ 0.877 rad in air.
6. The specific activity of Co-60 (half-life 5.27 years) is approximately:
A. 1.1 × 10³ Ci/g
B. 1.1 × 10² Ci/g
C. 1.1 × 10¹ Ci/g
D. 1.1 × 10⁰ Ci/g
Correct Answer: A
Rationale: Specific activity (Ci/g) = (1.3 × 10⁸) / (A × T½ in years) for A=60,
T½=5.27 → ~1.1 × 10³ Ci/g.
7. Which of the following is a pure beta emitter?
A. Co-60
B. Cs-137
C. Sr-90
D. Am-241

,Correct Answer: C
Rationale: Sr-90 decays to Y-90 (also beta) with no gamma. Co-60 and Cs-137
emit gammas; Am-241 emits alpha and gamma.
8. The range of a 5 MeV alpha particle in air is approximately:
A. 1 cm
B. 3.5 cm
C. 10 cm
D. 35 cm
Correct Answer: B
Rationale: Range (cm) ≈ 0.3 × E(MeV)^(3/2) for alpha in air → 0.3 × (5^1.5) = 0.3 ×
11.18 ≈ 3.35 cm.
9. A radionuclide decays by 75% in 12 days. Its half-life is:
A. 3 days
B. 4 days
C. 6 days
D. 8 days
Correct Answer: C
Rationale: After 2 half-lives, 75% decay (25% remains). 12 days = 2 half-lives →
half-life = 6 days.
10. The mass attenuation coefficient (μ/ρ) depends on:
A. Atomic number of absorber only
B. Photon energy only
C. Both photon energy and absorber Z
D. Absorber density only
Correct Answer: C
Rationale: μ/ρ depends on photon energy and absorber atomic number
(photoelectric ∝ Z³/E³, Compton ∝ Z/E).
11. 1 Gray (Gy) equals:
A. 100 rad
B. 1 rad
C. 1000 rad
D. 0.01 rad

, Correct Answer: A
Rationale: 1 Gy = 100 rad = 1 J/kg.
12. The quality factor (Q) for thermal neutrons (ICRP 26) is:
A. 2
B. 5
C. 10
D. 20
Correct Answer: B
Rationale: ICRP 26 assigned Q=5 for thermal neutrons. ICRP 103 uses w_R.
13. Which of the following has the highest specific activity?
A. H-3
B. C-14
C. Co-60
D. I-125
Correct Answer: A
Rationale: Shorter half-life → higher specific activity. H-3 (12.3 y) vs C-14 (5730 y),
Co-60 (5.27 y), I-125 (60 d). I-125 has shorter half-life but low atomic mass? Wait:
Specific activity (Ci/g) ∝ 1/(A×T½). I-125: A=125, T½=0.164 y; H-3: A=3, T½=12.3 y
→ H-3 much higher.
14. The unit of absorbed dose is:
A. Roentgen
B. Coulomb/kg
C. Gray
D. Sievert
Correct Answer: C
Rationale: Gray (Gy) is absorbed dose. Sievert is equivalent dose. Roentgen is
exposure.
15. A 10 mCi source of Tc-99m (half-life 6 hours) will decay to what activity after
24 hours?
A. 2.5 mCi
B. 1.25 mCi