As pointed out in Sec. 5-3, radioactive materials are released to special pits scooped out of the ground (as at ORNL) or to subsurface formations through cribs (as at HAPO). Since the pits at Oak Ridge are on the surface and open, certain hazards are associated with these operations which are not present at Hanford.

(a) Oak Ridge National Laboratory Operations. Several surface pits have been used at ORNL for disposal of radioactive wastes containing Sr90, Cs137, and Ru106. With the exception of Ru106 and traces of Co60 and Sb124, the bulk of the residual radionuclides is retained close to its point of introduction. This accumulation of radionuclides is a radiation hazard to maintenance and research personnel. A radiation survey made on May 16, 1956, in the immediate vicinity of the three pits then being used showed maximum radiation levels of 3000 and 4000 mr/hr at the edge of one of the pits.13 With

a permissible occupational level at that time of 7.5 mr/hr, the time spent by personnel in the vicinity of these pits was severely restricted. A person could remain in an area where levels amounted to 1000 mr/hr for only 27 sec out of each hour without exceeding the permissible exposure of 7.5 mr/hr. The radiation levels encountered are shown in Fig. 15.1.

So that wild fowl which alight on the surface will not be exposed, waste pits at ORNL are covered with chicken wire. White Oak Lake, which, when it existed, received waste discharges from ORNL, also served as a flyway for migratory water fowl. Studies at ORNL with ducks, caught and banded, showed large-scale geographical distribution of the birds, indicating possible widespread carriage of radioactive material and potential exposure to persons many miles from the waste-disposal site.

(b) Hanford Operations. The shielding afforded by the ground cover in the use of cribs and subsurface disposal facilities at Hanford precludes external radiation exposure to plant personnel. Disposal of very large volumes of waste into the Hanford subsoils is not without potential hazard, however, since the possibility exists of direct groundwater contamination. In addition, the water table in the area has been modified, and a change in the time of travel of groundwater to surface water sources has resulted.

At Hanford, low-level radioactive solutions are disposed of into surface ponds. In such disposal practices one of the problems encountered in semiarid regions is the subsequent drying of contaminated soils, permitting them to be picked up and carried by the wind. In recognition of this some of the earlier pits used for this purpose have been abandoned and back filled. Some ponds are still in use, but the

Radiation contours

Fig. 15.1-Radiation levels, ORNL chemical-waste pit area. are in milliroentgens per hour. Paper-chamber Cutie Pie measurements, May 16, 1956.

concentration of radioactive material released to them is limited to less than 5X10-5 μc/ml.

15-4.2 Accumulation in Soil

Where radioactive materials are exchanged by or adsorbed or precipitated on soils, potential hazards exist. External exposure from contact exists. Not so obvious, however, are two other possibilities for exposure: the first results from movement of deposited materials during periods of flood with subsequent deposition on land used for agriculture, and the second arises from removal of such sediments in dredging operations associated with channel improvements.

692-623 - 64-23

Deposition of specific radionuclides released from stacks has been discussed. The radionuclide studied most extensively at Hanford was [131, which was released during fuel-reprocessing operations. As a result of these studies, the permissible concentration of I131 in air was reduced from 3X10-9 uc/cm3 to 3X10-13 μc/cm3. From these studies a level of 1X10-5 μc of I131 per gram of vegetation was also established. This reflects a situation where the pathway of a radionuclide changes from inhalation to ingestion. In this instance inhalation at the given level posed no problem, but deposition of the [131 followed by ingestion by grazing animals and subsequent utilization of food products by man resulted in a greater degree of potential hazard. Control of I131 at the source of release offered a comparatively simple solution to the problem, and the permissible I131 levels were reduced.

15-6 SUMMARY

By means of examples of operations currently under way, the procedures taken to minimize radiation exposure of the population from nuclear energy operations are indicated. These examples show that permissible levels of discharge do not depend solely upon values given in the various handbooks but must be derived from a study of local conditions. Such study cannot be limited to the immediate vicinity of the plant but must encompass a much broader area, particularly where a change in environmental conditions may bring additional factors into play which were nonexistent at the disposal point. It is also pointed out that certain materials (seaweed, fish, and migratory water fowl) are sometimes consumed at great distances from their source of contamination. Each release of radioactive materials must be studied in terms of its effect on the populations involved.

REFERENCES

1. INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Recommendations of the International Commission on Radiological Protection, Pergamon Press, Inc., New York, 1959.

2. C. P. STRAUB, A. S. GOLDIN, and A. G. FRIEND, Environmental Implications of Radioactive Waste Disposal as Related to Stream Environments, in Disposal of Radioactive Wastes, Proceedings Conference, Monaco, 1959, Vol. 2, pp. 407-419, International Atomic Energy Agency, Vienna, Austria, 1960.

3. H. M. PARKER, Hanford Waste Management, in Hearings before the Special Subcommittee on Radiation of the Joint Committee on Atomic Energy, Congress of the United States, 86th Congress, First Session on Industrial Radioactive Waste Disposal, January 28, 29, and 30; February 2 and 3, 1959, Vol. 1, pp. 220-226, Superintendent of Documents, U.S. Government Printing Office, Washington, D. C., 1959.

4. NATIONAL COMMITTEE ON RADIATION PROTECTION, Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposure, National Bureau of Standards Handbook 69, Superintendent of Documents, U.S. Government Printing Office, Washington, D. C., June 5, 1959.

5. U.S. ATOMIC ENERGY COMMISSION, Part 20-Standards for Protection Against Radiation, Federal Register, 25 (224): 10914-10924, Nov. 17, 1960; see also Appendix B of this book.

6. F. MORGAN, Fisheries Radiobiology and the Discharge of Radioactive Wastes, in Disposal of Radioactive Wastes, Proceedings Conference, Monaco, 1959, Vol. 2, pp. 19–24, International Atomic Energy Agency, Vienna, Austria, 1960.

7. R. F. FOSTER, The Need for Biological Monitoring of Radioactive Waste Streams, Sewage Ind. Wastes, 31: 1409–1415 (1959).

8. C. R. McCULLOUGH, Safety Aspects of Nuclear Reactors, p. 112, D. Van Nostrand Co., Inc., Princeton, N. J., 1957.

9. RADIOLOGICAL HEALTH RESEARCH ACTIVITIES, Robert A. Taft Sanitary Engineering Center, Cincinnati, Ohio, unpublished data, 1960.

10. A. W. KENNY, Radioactive Discharge to Sewers and Rivers, Inst. Sewage Purif., J. Proc., Part 4: 383-390 (1957).

11. C. C. RUCHHOFT and J. FEITELBERG, Estimates on the Concentration of Radioiodine in Sewage and Sludge from Hospital Wastes, Nucleonics, 9(6): 29 (December 1951).

12. K. G. SCOTT, Radioactive Waste Disposal-How Will It Affect Man's Economy?, Nucleonics, 6(1): 18 (January 1950).

13. K. Z. MORGAN, Health Physics Division Semiannual Progress Report for Period Ending July 31, 1956, USAEC Report ORNL-2151, Oak Ridge National Laboratory, Nov. 2, 1956.