Ground shine dose

Therefore the ground shine dose from caesium-137 is ... 

Evaluation of the doses of radiation from caesium-137 deposited on the ground Cground-shine dose)... 

The integrated dose due to ground shine with absorption in the soil, corresponding to a ground initial concentration of 1 Bq cm of caesium-137 (a contribution by other nuclides exists but is not evaluated here) ... 

On the assumption that in the vicinity of the plant there is no intake of caesium through the food chain, the doses to the population can be caused by ground shine (on the assumption the population have not been evacuated). The doses at 1 year and at 50 years can be calculated on the basis of the factors shown in Table A4-3, corresponding to a contamination of 1 kBq m (Ferreli and Bologna, 1991). 

Delayed actions Actions involving public temporary relocation, based on projected doses up to 30 days caused by ground shine and aerosol resuspension, which may be implemented after the practical end of the releases phase of an accident. 

During a release, the dose from cloud shine, ground shine, skin contamination, and inhalation is predominant. After the plume has passed, the dose from ground shine and ingestion of contaminated food and milk becomes predominant. 

Sheltering. As discussed above under Public Protective Actions, sheltering can be effective protection from exposure from the cloud shine, ground shine, and inhalation dose resulting from a plume. The degree of effectiveness depends on the building type. 

Results of dose calculation (immersion, ingestion and/or ground shine). 

A.164S. Ground contamination. This section shall discuss possible ground contamination, by eidier direct dispersion of particulate radioactive material or deposition from airborne or aqueous releases. The surface contamination by radionuclides shall be estimated and the doses (due to ground shine and ingestion) assessed. 

The top right figure shows the contributions to the 24-hr whole body dose. The inhalation pathway would contribute the least to projected whole body dose the cloud shine dose would be sublethal, but the additional 24-hr ground shine contribution would lead to projected doses in excess of the early injury threshold (50 to 100 rem) out to 7 miles or so and the early fatality threshold (250 rem) out to about 3 miles. 

Most of the total dose increase between 4 hr and 7 days (shown in the top left part of Figure 5.2-8) results from ground contamination deposited by the passing plume. This shows the importance of ground contamination. In this example, the direct dose from the plume (cloud shine and inhalation) is not sufficient to result in early deaths or injuries but if people remain on contaminated ground, their dose will increase until, at about 6 hr, the dose could result in injuries and, at 12 hr, cause death. Obviously, after a major release, areas of substantial ground contamination must be identified, and the population must be evacuated. 

The 95 Quantile X/Q at 3000 m for a ground release with wake as calculated by the MACCS2 code is 5.16E-05 sec/m at 3000 m and 1.16E-03 secern at a distance of 300 m, yielding a X/Q ratio of. 044. Thus, the calculated bounding dose at 3000 meters is. 044 (1 rem) or 44 mrem. The DOE calculated dose and this dose that is derived from it include dose contributions from committed effective dose for 50 years (CEDE) and immersion in the radioactive plume (cloud shine). This potential dose consequence represents a conservative upper bound on the public dose since the maximum radiological inventory corresponding to HC2 levels was used in the analysis, and no mitigation of the release was taken into account. 

From the bottom figures, it can be seen that projected thyroid doses are dominated by inhalation doses. The ground and cloud shine contributions increase the thyroid dose only marginally within 24 hr. Thyroid ablation would occur at thyroid doses abovfc about 1000 rem. This would not be expected beyond about 3 miles for the postulated (PWR 4) source term and weather conditions. Whole-body dose (not thyroid dose) would be the most important dose for most accidents in terms of early fatalities and injuries. 

Improvised respiratory protection, such as placing a towel over the mouth and nose, reduces only the inhalation exposure, not the exposure to cloud shine or the exposure to contaminated ground and other surfaces. Since, for most severe accidents, inhalation dose would... 

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