Ion lifetimes in irradiated gaseous HCl

1967 ◽  
Vol 45 (24) ◽  
pp. 3079-3082 ◽  
Author(s):  
D. A. Armstrong ◽  
R. A. Back
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
Gamma Rays ◽  
Half Life ◽  
Field Method ◽  
Dose Rates ◽  
Phase Combination

An intermittent-field method has been used to measure ion lifetimes in gaseous HCl during irradiation by gamma rays under conditions of pressure, dose rate, and vessel geometry similar to those employed in radiolysis studies. At 23 °C, with HCl pressures from 119 to 660 Torr and dose rates from 5.5 to 86 × 1010 eV cc−1 s−1, the ion half-life ranged from 6 to 30 ms. The dependence on dose rate and pressure strongly indicated that ion neutralization occurred almost entirely in the gas phase. Values of α, the gas-phase combination coefficient, were calculated; at pressures above 246 Torr the value was constant and equal to 3.1 ± 0.3 × 10−6 cc ions−1 s−1. The addition of SF6 had little effect on α, while reducing the temperature to −79 °C increased α to 5.1 × 10−6.

Ion lifetimes in gaseous radiolysis systems

1967 ◽  
Vol 45 (24) ◽  
pp. 3071-3078
Author(s):  
C. J. Wood ◽  
R. A. Back ◽  
D. H. Dawes
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
Applied Field ◽  
Wave Period ◽  
Ion Currents ◽  
Square Wave ◽  
Dose Rates ◽  
Phase Combination

A technique is described for measuring ion lifetimes in irradiated gases. Gases were irradiated continuously, and lifetimes were determined by measuring average ion currents, obtained with an intermittent square-wave applied field, as a function of square-wave period. The dose rates, pressures, and vessel geometry were similar to those commonly used in radiolysis experiments, so that the information obtained can be applied directly to an understanding of radiolysis mechanisms. The theory of the method and analysis of ion-loss processes are discussed in some detail.Measurements in oxygen at pressures from 30 to 300 Torr and dose rates from 1.5 to 56 × 1010 eV cc−1 s−1 gave mean ion lifetimes ranging from 0.014 to 0.082 s. The dependence of lifetime on dose rate and pressure indicated that ion loss under these conditions was almost entirely by gas-phase combination. Values of α, the gas-phase combination coefficient, are compared with those measured by other methods.

Isotope effects in the gas phase radiolysis of H2S and D2S

1976 ◽  
Vol 54 (17) ◽  
pp. 2767-2772
Author(s):  
Robert D. McAlpine ◽  
O. A. Miller ◽  
A. W. Boyd
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
Isotope Effects ◽  
High Dose ◽  
Dose Rates ◽  
Kinetic Isotope ◽  
A Value ◽  
Straight Line ◽  
Separation Factors ◽  
Very High

Gas phase radiolysis studies have been carried out on mixtures of H2S and D2S using as irradiation sources, either a Gammacell or a Febetron 705 pulsed electron accelerator. Separation factors (α = (H/D)prod ÷ (H/D)react) were obtained for various values of xD (the mole fraction of D2S), dose rate and temperature, as well as with the addition of SF6. All of the observed α values, for 0.2 ≤ xD ≤ 0.8, fall on the following empirical straight line.[Formula: see text]The addition of neon to a D2S/H2S mixture gives a value of α which decreases as the partial pressure of neon increases. For a 70% D2S/30% H2S mixture, &([a-z]+); = 1.9 ± 0.1 for the pure mixture and 1.28 ± 0.08 when 90 kPa of neon has been added to 10 kPa of the mixture. The &([a-z]+); values described by eq. 1 are interpreted as arising from kinetic isotope effects in the reactions of (translationally) hot H or D atoms with H2S, HDS, or D2S to form H2, HD or D2.Hydrogen yields from the gas phase radiolysis of pure H2S and pure D2S have been determined for dose rates from 4 × 1016 to 2 × 1028 eV g−1 s−1. Using dose rates of up to 2 × 1027 eV g−1 s−1, ΔG = G(H2) − G(D2) = 0.5. For the highest dose rate used (2 × 1028 eV g−1 s−1), ΔG = 1.5. The larger value of ΔG at very high dose rates is thought to arise from the dissociative neutralization processes. A possible mechanism is discussed.

Radiation exposure around patients after administration of 123I-MIBG

2002 ◽  
Vol 41 (05) ◽  
pp. 221-223
Author(s):  
S. Ofluoglu ◽  
J. Preitfellner ◽  
B. J. Fueger ◽  
T. Traub ◽  
C. Novotny ◽  
...  
Keyword(s):  
Radiation Exposure ◽  
Dose Rate ◽  
Half Life ◽  
Maximum Dose ◽  
Radiation Detectors ◽  
Mibg Scintigraphy ◽  
Dose Limit ◽  
Annual Dose ◽  
Dose Rates ◽  
M 12

SummaryAim: Estimation of the radiation exposure to neighbouring patients, personnel and relatives deriving from patients undergoing 123I-MIBG scintigraphy. Methods: For scintigraphic studies, 16 patients with suspected pheocromocytoma were injected with 340 ± 30 MBq 123I-MIBG. Dose rates were measured at a distance of 0.5 m, 1 m, and 2 m after 10 min, 3 h, 21 h, 45 h, and 68 h using three calibrated portable radiation detectors. The measured values were background corrected. Results: Ten minutes after injection the dose rate was 10.5 µS/h at a distance of 0.5 m, 3.78 µS/h at 1 m, and 0.95 µS/h at 2 m. The effective half-life was estimated to 8.68 ± 0.15 h. The maximum dose in a distance of 1 m for neighbouring patients was 46 µS/h, for personnel in a ward 27 µS/h, and to relatives in a distance of 2 m 12 µS/h. Conclusion: This study demonstrates that the calculated exposure to people around patients after 123I-MIBG injection is well below the maximum permissible annual dose limit of 1 mSv for not professionally exposed persons.

EFFECT OF BUILDUP FACTORS ON INDOOR GAMMA DOSE RATE

2020 ◽  
Vol 190 (2) ◽  
pp. 132-138
Author(s):  
V Manić ◽  
G Manić ◽  
D Nikezić ◽  
D Krstić
Keyword(s):  
Effective Dose ◽  
Dose Rate ◽  
Gamma Rays ◽  
Building Materials ◽  
Absorbed Dose ◽  
Gamma Dose ◽  
Gamma Dose Rate ◽  
Absorbed Dose Rate ◽  
Dose Rates ◽  
Buildup Factors

Abstract The effect of buildup factors on absorbed dose rate in air and the effective dose from gamma rays of primordial radionuclides in building materials, was investigated in the article. Specific absorbed dose rates were calculated for the standard concrete room, as well as, for rooms where brick and covering building materials were used. For all room models the Harima (G-P) buildup factors were applied, while for the standard room the Berger’s and Taylor’s buildup factors were used, too. The contribution of the radiation buildup to absorbed dose rate and effective dose was determined as large as 41%.

Radiation dosimetry with acetylene

1971 ◽  
Vol 24 (10) ◽  
pp. 2053
Author(s):  
KG McLaren
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
No Value ◽  
Free Radical Scavengers ◽  
Lower Yield ◽  
Γ Irradiation ◽  
Dose Rates ◽  
Wide Range ◽  
Absolute Basis ◽  
Dose Rate Effect

The suitability of acetylene as a gas-phase radiation dosimeter has been studied. Yields were obtained on an absolute basis, using ionization current dosimetry. Radiolysis of acetylene produces two products, benzene and polymer. The yield of benzene is dependent on dose, dose rate, presence of hydrogen or free radical scavengers, and temperature, and is of no value for estimating dose. ��� For 60Co γ irradiation at a dose rate of 4.1 x 1013 eV cm-3 mmHg-1 hr-1 and acetylene pressure 500 mmHg (6.6x104 N m-2) at 30�C, G(-C2H2) = 82.1�0.5. ��� 1-MeV electron irradiation at a dose rate of 3.9 x 1016 eV cm-3 mmHg-1 hr-1 gave a much lower yield, G(-C2H2) = 55.0�1.9, believed to be due to a dose rate effect. G(-C2H2) increased by about 67% when the temperature was increased from 25�C to 125-250�C. ��� Comparison with ethylene indicates the latter is the more useful dosimeter, as the yields do not vary significantly over a wide range of dose rates and temperatures.

scholarly journals Dose Estimates of Occupational Radiation Exposure During Radioguided Surgery of [99mTc]Tc-PSMA-labeled Lymph Nodes in Recurrent Prostate Cancer

2020 ◽  
Author(s):  
Daniel Schmidt ◽  
Jirka Grosse ◽  
Jutta Moosbauer ◽  
Roman Mayr ◽  
Maximilian Burger ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Dose Rate ◽  
Radiation Protection ◽  
Half Life ◽  
Operation Time ◽  
Radioguided Surgery ◽  
Dose Rates ◽  
Measured Dose ◽  
External Exposures ◽  
Occupational Radiation

Abstract Background and objective[99mTc]Tc-PSMA-based radioguided surgery (TPRS) represents a curative approach for localized relapse of prostate cancer. For its simplified regulatory permission, the radiation protection authorities require a 99mTc activity below the exemption limit of 10 MBq at the time of surgery. Our aim was to determine the optimal amount of radioactivity (OAR) to comply with that limit and to estimate the maximum number of TPRS procedures per year and surgeon without triggering the full monitoring obligations.MethodsIn this retrospective study, a dose rate meter was calibrated using measurements on phantoms and from recently injected (1 min p.i.) patients to determine the activity in the patient from measured dose rates. The effective half-life of [99mTc]Tc-PSMA-I&S in patients was determined from repeated dose rate measurements up to 27 h p.i. to estimate dose parameters of relevance for radiation protection. External exposures of the surgeons were measured with personal dosimeters calibrated in Hp(10). ResultsFrom the first 6 subsequent patients, an effective half-life of 4.15 h was observed. Assuming an operation time 24 h p.i., the OAR was 550 MBq. Operations lasting in average 2 h in a distance of 0.25 m to the patient imply a body dose for surgeons of 4,16 µSv per procedure. Based on these estimates, the surgeon’s Hp(10) is less than 1 mSv per year with up to 241 operations per year. The effective dose for surgeons during the procedure determined with an electronic dosimeter is 4±1 µSv. SummaryAll radiation protection regulations are met with adherence to OAR recommended here without triggering the full monitoring obligations from radiation protection regulations.

Dose estimates of occupational radiation exposure during radioguided surgery of Tc-99m-PSMA-labeled lymph nodes in recurrent prostate cancer

2021 ◽  
Author(s):  
Daniel Schmidt ◽  
Jirka Grosse ◽  
Roman Mayr ◽  
Maximilian Burger ◽  
Dirk Hellwig
Keyword(s):  
Prostate Cancer ◽  
Lymph Nodes ◽  
Dose Rate ◽  
Radiation Protection ◽  
Half Life ◽  
Operation Time ◽  
Radioguided Surgery ◽  
Dose Rates ◽  
99Mtc Activity ◽  
External Exposures

Abstract Aim [99mTc]Tc-PSMA-based radioguided surgery (TPRS) represents a curative approach for localized relapse of prostate cancer. For its simplified regulatory permission, the radiation protection authorities require a 99mTc- activity below the exemption limit of 10 MBq at the time of surgery. Our aim was to determine the optimal amount of radioactivity (OAR) to comply with that limit and to estimate the maximum number of TPRS procedures per year and surgeon without triggering the full monitoring obligations. Methods In this retrospective study, a dose rate meter was calibrated using measurements on phantoms and from recently injected (1 min p. i.) patients to determine the activity in the patient from measured dose rates. The effective half-life of 99mTc-PSMA-I&S in patients was determined from repeated dose rate measurements to estimate dose parameters of relevance for radiation protection. External exposures of the surgeons were measured with personal dosimeters calibrated in Hp(10). The surgeon’s finger dose Hp(0.07) is estimated from radioactivity measured in resected lymph nodes. Potenzial incorporations were estimated for an activity of 10 MBq. Results From the first 6 subsequent patients, an effective half-life of 4.15 h was observed. Assuming an operation time 24 h p. i., the OAR was 550 MBq. Operations lasting in average 2 h in a distance of 0.25 m to the patient imply a body dose for surgeons of 4.16 µSv per procedure. Based on these estimates, the surgeon’s Hp(10) is less than 1 mSv per year with up to 241 operations per year. Hp(0.07) and potential incorporation of activity do not lead to further limitations. Summary All radiation protection regulations are met with adherence to OAR recommended here without triggering the full monitoring obligations from radiation protection regulations.

REDUCTION IN AMBIENT GAMMA DOSE RATE FROM RADIOCESIUM DUE TO SNOW COVER

2019 ◽  
Vol 184 (3-4) ◽  
pp. 510-513
Author(s):  
Y Omori ◽  
S Inoue ◽  
T Otsuka ◽  
Y Nagamatsu ◽  
A Sorimachi ◽  
...  
Keyword(s):  
Snow Cover ◽  
Dose Rate ◽  
Gamma Rays ◽  
Snow Water Equivalent ◽  
Gamma Dose ◽  
Gamma Dose Rate ◽  
Dose Rates ◽  
Gamma Dose Rates ◽  
Snow Water ◽  
Ambient Gamma Dose Rate

Abstract In the present study, variations in ambient gamma dose rate associated with snow cover were examined in a radioactive-contaminated site in Fukushima Prefecture, Japan. The ambient gamma dose rates decreased with increasing snow depth. The reduction trends were different between fresh snow (0.1–0.2 g/cm3) and granular snow (0.3–0.4 g/cm3) depending on snow density. Snow cover water content (snow water equivalent) calculated from snow depth and density was a key parameter governing the reduction in the ambient gamma dose rate. The ambient gamma dose rates reduced to 0.6 and 0.5 at 4 g/cm2 and 8 g/cm2 of snow water equivalent, respectively. Based on gamma-ray flux density distributions, the ambient gamma dose rates from the primary gamma rays decreased more compared to those from scattered gamma rays due to snow cover.

THE EFFECT OF ELECTRIC FIELDS, AND A RELATED DEPENDENCE ON DOSE RATE, IN THE γ-RADIOLYSIS OF HYDROCARBON GASES

1963 ◽  
Vol 41 (6) ◽  
pp. 1463-1468 ◽  
Author(s):  
T. W. Woodward ◽  
R. A. Back
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
Electric Fields ◽  
Low Dose ◽  
High Dose ◽  
Hydrogen Yield ◽  
Hydrocarbon Gases ◽  
Saturation Field ◽  
Dose Rates ◽  
And Diffusion

The effect of electric fields on the γ-radiolysis of ethane, propane, and the butanes has been investigated briefly at 800 mm pressure, with dose rates between 2 × 1010 and 400 × 1010 ev/cc sec. Yields of hydrogen were reduced when a saturation field was applied, except with ethane at low dose rate, where a slight increase in hydrogen yield was observed. With propane and n-butane, the yield of hydrogen in the presence of a saturation field was independent of dose rate, while with ethane, it decreased with decreasing dose rate. At the same time, a dose rate dependence was discovered in the simple radiolysis, in the absence of any field, of ethane, propane, and n-butane, a decrease in the yield of hydrogen at low dose rates being observed. An explanation of these observations is suggested in terms of a competition between neutralization of ions in the gas phase and diffusion of ions to the wall. High dose rates should favor the former process, and low dose rates the latter. At sufficiently high dose rates, all ions should be neutralized in the gas phase. At sufficiently low dose rates, all ions should diffuse to the wall before neutralization, and it is suggested that the radiolysis under these conditions should closely resemble that in the presence of a saturation field at higher dose rates.

Ovarian Dysfunction in Fetally Irradiated Beagles

1977 ◽  
Vol 35 ◽  
pp. 658-659
Author(s):  
T. M. Seed ◽  
M. H. Sanderson ◽  
D. L. Gutzeit ◽  
T. E. Fritz ◽  
D. V. Tolle ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Low Dose ◽  
Long Term Effects ◽  
Ovarian Dysfunction ◽  
Dose Rates ◽  
Highly Sensitive ◽  
Microscopic Evaluation ◽  
Ovarian Pathology ◽  
Normal Offspring

The developing mammalian fetus is thought to be highly sensitive to ionizing radiation. However, dose, dose-rate relationships are not well established, especially the long term effects of protracted, low-dose exposure. A previous report (1) has indicated that bred beagle bitches exposed to daily doses of 5 to 35 R 60Co gamma rays throughout gestation can produce viable, seemingly normal offspring. Puppies irradiated in utero are distinguishable from controls only by their smaller size, dental abnormalities, and, in adulthood, by their inability to bear young.We report here our preliminary microscopic evaluation of ovarian pathology in young pups continuously irradiated throughout gestation at daily (22 h/day) dose rates of either 0.4, 1.0, 2.5, or 5.0 R/day of gamma rays from an attenuated 60Co source. Pups from non-irradiated bitches served as controls. Experimental animals were evaluated clinically and hematologically (control + 5.0 R/day pups) at regular intervals.

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