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Hot Spots of Radiation

During daily operations at the Hanford nuclear site radioactive substances were released into the air. These included iodine-131, plutonium and ruthenium particles. Due to the effects of weather, situations can be created were, for a period of time, people who live farther away from Hanford could received higher levels of exposure than those living closer to Hanford. It certain areas, called hot spots, the concentration of contaminates was greater than in others.

The Hanford Environmental Dose Reconstruction Project was created to estimate what radiation exposure people living near Hanford between 1944 and 1992 might have received. Computer models were using mathematical calculations and historical weather information was used to simulate the likely spread of Hanford's radiation. Even with these models it is nearly impossible to determine exactly where hot spots actually occurred during the 40 years that Hanford was releasing radiation into the air. Part of the reason for this is because of limited precipitation data, the amount of time that has passed and the large geographical area that was exposed. The historical information does give enough information to reconstruct the general pattern of contamination.

Radioactive pollution became airborne by escaping through the 200 foot smoke stacks on top of Hanford's plutonium separation plants. Where and how much of this radioactive material returned to earth was greatly affected by weather conditions such as precipitation and the speed and direction of the wind.

Hanford officials ordered that emissions be released at night when the air was cooler at ground level than at the top of the stack. These conditions made it less likely that the radioactive material would fall back to earth near the operating plants. This was done to prevent serious exposure to workers, a practice that began in May of 1945 after there were two serious instances of worker contamination. Although releasing emissions at night protected the workers, the windy conditions often experienced in this part of the State meant that more radiation was being carried out of the Hanford than if releases were done during the day.

When determining where the radiation that was released into the air went, the two most important factors are the speed and direction of the wind. The wind from the Hanford stacks generally blew southeastward to the Tri-Cities, on to Walla Walla, and then northeast toward Spokane and Northern Idaho. Yakima and other areas outside of this pattern did not receive as much exposure from Hanford's airborne radiation. Of the people who lived and worked in this downwind pattern, the closer they lived to Hanford the greater their exposure to airborne releases was. However, other factors could contribute to exposure such as reoccurring hot spots, where the food people consumed came from (especially their milk and fresh leafy vegetables), and the time periods a person you lived in a particular area.

Since the releases of pollution from the stacks at Hanford could take many minutes or hours, the wind direction could change while the release was still happening. This could send a pollution plume in two or more directions. If the winds changed again later it could cause the plumes to combine together. The combination of plumes caused by regular weather patterns would result in a reoccurring hot spot. The Hanford Environmental Dose Reconstruction Project believes that the area around Spokane was this type of hot spot.

If the wind that carried radioactive material became calm, the radioactive plume would stay over one particular area for a longer amount of time which could create a hot spot. In 1949, when workers at Hanford released a large amount of iodine-131 into the air, known as the Green Run, the wind died down over Walla Walla for several days before carrying the remaining radioactive material toward Spokane, Northern Idaho and Canada.

When the wind is carrying radioactive materials in the air and encounters participation this would affective where the contamination fell to earth. If it was raining or snowing over an area while radiation was in the air, that area could have received greater exposure than the areas surrounding it.

If wind carrying a pollution plume hits the side of a hill or mountain it will cause greater amounts of contamination than other areas at the same elevation. This can be seen in areas such as the Wahluke Slope and Rattlesnake Mountain, both in close proximity to Hanford.

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