Introduction to Health Physics: Fourth Edition - Ruang Baca FMIPA UB

CRITICALITY 663
12.10. The blood plasma from a worker who was overexposed during a criticality accident
had a 24Na specific activity of 37 Bq (0.001 μCi) per mL 15 hours after the
accident. The accidental excursion lasted 10 milliseconds. All the Na in nature
is 23Na. The thermal neutron activation cross section for 2200 m/s neutrons is
0.53 b. What was the absorbed dose due to (a) the 14N(n, p) 14C reaction and (b)
the autointegral gamma-ray dose due to the n,γ reaction on hydrogen?
12.11. (a) For the case where k = 1.0025 and the initial number of neutrons is 1000,
how many neutrons will be present after 10 generations?
(b) After how many generations will the neutron flux be doubled?
12.12. At 20 minutes after a criticality accident the dose rate in a laboratory from the
fission products was 15 Gy/h (1500 rad/h). If the laboratory ventilation system
was shut down at the time of the criticality, how long would it take before a person
could enter the laboratory if his dose equivalent during a projected 15-minute
exposure time is not to exceed 50 mGy (5 rads)?
12.13. A transient burst of 1 × 1015 fissions in an unshielded accumulation of fissile
materials causes a total dose equivalent of 0.25 Sv (25 rems) at a distance of 2 m.
If the neutron-to-gamma dose-equivalent ratio is 9 : 1, what were the absorbed
doses from the gammas and from the neutrons?
12.14. The composition, by weight percent, of a concrete mix used in reactor shielding
consists of oxygen, 52.17%; Si, 34.0%; Ca, 4.4%; Al, 3.5%; Na, 1.6%; Fe, 1.5%;
K, 1.3%; and H, 1.0%. The density of the concrete is 2.35 g/cm3 .
(a) Find and tabulate the thermal (2200 m/s) absorption cross section for each
element.
(b) Calculate the linear absorption coefficient (macroscopic cross section) of
the concrete.
12.15. The 131I fission yield is 2.77%. What is the 131I activity in the core of a power
reactor that had been operating at a power level of 3000 MW (t) for
(a) 8 days,
(b) 30 days,
(c) 60 days, and
(d) 180 days?
12.16. Tritium is produced in a nuclear reactor in ternary fission, in which one 3H nucleus
is produced in every 104 fissions. What is the tritium activity in a reactor core that
had been operating at a mean power level of 3000 MW(t) for 2 years?
SUGGESTED READINGS
Ayers, J. A., ed. Decontamination of Nuclear Reactors and Equipment. Ronald Press, New York, 1970.
Clark, H. K. Handbook of Nuclear Safety. Report No. DP-J32, TID-4500, Office of Technical Services, Washington,
DC, 1961.
Etherington, H., ed. Nuclear Engineering Handbook. McGraw Hill, New York, 1958.
Farmer, F. R., ed. Nuclear Reactor Safety. Academic Press, New York, 1977.
Foster, A. R., and Wright, R. L., Jr. Basic Nuclear Engineering, 4th ed. Allyn and Bacon, Boston, MA, 1983.