ML17326B437
| ML17326B437 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 08/23/1988 |
| From: | Virgilio M Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17326B438 | List: |
| References | |
| NUDOCS 8809080294 | |
| Download: ML17326B437 (9) | |
Text
~
~
A UNITED STATES NUCLEAR REGULATORY COMMISSION INDIANA MICHIGAN POWER COMPANY DONALD C.
COOK NUCLEAR PLANT UNITS NOS.
1 AND 2 DOCKETS NOS. 50"315 AND 50-316 ENVIRONMENTAL ASSESSMENT AND FINDING OF NO SIGNIFICANT IMPACT 7590-01 The U.S. Nuclear Regulatory Commission (the Commission) is considering the approval of a procedure for the disposal of contaminated concrete at the Donald C.
Cook Nuclear Plant, pursuant to 10 CFR 20.302, as requested by Indiana Michigan Power Company (the licensee).
D.
C.
Cook Nuclear Plant is located in Berrien County, Michigan.
ENVIRONMENTAL ASSESSMENT Identification of Pro osed Action:
The proposed action would approve the onsite disposal of contaminated concrete resulting from the replacement of the steam generators in D.
C.
Cook Unit No.
2.
The Need for the Pro osed Action:
To provide access for complete replacement of the four steam generator lower assemblies, a large opening will be cut in each of the reinforced concrete doghouses surrounding the steam generators.
Large sections of reinforced concrete will need to be removed from the Unit 2 steam generator doghouse enclosures and must be disposed of.
The licensee proposes to decontaminate the concrete to the extent practical.
Following decontamination of the concrete, the licensee intends to dispose of the concrete outside the protected area fence, but within the 880908025'4 880830 PDR ADOCK 050003i5 P
PDC D.
C.
Cook Nuclear Plant site boundary.
The chosen site is presently the site of concrete spoils and other construction remnants left from the construction of the plant.
Environmental Im acts of the Pro osed Action:
By letter dated February 29, 1988 the licensee submitted an application for the onsite disposal of contaminated concrete slabs, a licensed material not previously considered by the Commission's staff in the D.
C.
Cook Final Environmental Statement (FES) dated August 1973.
The application, prepared in accordance with 10 CFR 20.302(a),
contains a detailed description of the licensed material, thoroughly analyzes and evaluates the information pertinent to the effects on the environment of the disposal of the licensed material, and commits the licensee to follow specific procedures to minimize the risk of unexpected or hazardous exposure.
The proposed action would allow the licensee to retain contaminated concrete on site at the D.
C.
Cook Nuclear Plant.
Large sections of reinforced concrete will be removed from the D.
C.
Cook Unit No.
2 steam generator doghouse enclosures and must be disposed of.
Decontamination by mechanical removal of paint, and surface concrete to a depth of 1/16",
will eliminate the majority of the contamination accumulated in the concrete.
However, the concrete sections will have trace quantities of Cobalt-60 (Co-60),
Cesium-134 (Cs-134),
and Cesium-137 (Cs-137) distributed in the remaining outer surfaces.
The concrete will be removed in 24 to 30 large slabs ranging in weight from 25 to 70 tons each.
It is planned to dispose of the material in this form, as large structural segments.
The roof sections are three feet thick, and the wall portions are two feet thick.
The estimated total weight of the slabs is 920 tons.
This total includes an estimated 65 tons of reinforcing steel and steel structural supports.
The outer surfaces of the doghouse structures are in the upper containment volume.
The surfaces were painted with nuclear Grade I paint prior to operation of the unit.
However, the airborne contamination inside containment, arising due to normal operations, has brought small amounts of radioactive contamination into contact with the surfaces.
Over the ten years of plant operation, the small amounts of contamination have diffused through the paint and into the outer layer of concrete.
Inside the doghouse structure, airborne contamination again has contributed to the deposition of radioactivity on the walls.
Radiological analysis was performed on samples of paint and underlying concrete from the outside wall of the doghouse structures.
Three nuclides were found in the concrete:
Cobalt-60, Cesium-134, and Cesium-137.
The average of the measured sample concentration of each nuclide is given in the licensee's application and is shown below in Table 1.
The licensee indicated in the application that the concentrations represent the activity expected in the surface of the concrete when it is disposed of after decontamination.
The licensee used maximum measured sample concentration in portions of the radiological impact assessment to insure conservatism in the calculations, and these values are summarized in Table 1 also.
To calculate the total activity present in the concrete, the licensee's estimate was made, based on the sample data, of the amount of diffusion of the radionuclides into the concrete.
Diffusion is a physical phenomena generally applied to gaseous and liquid materials 'migrating'nto a
host material.
The amount of diffusion of one material into another is dependent on the properties of both materials, the temperature, and the
concentration of the diffusing material at the surface of contact.
Mater evaporating into air is an example of diffusion. 'he process of diffusion for the subject concrete was modeled mathematically according to Fick's Law which is a natural exponential function.
The concentration of the diffusing material (i.e., the radioiosotopes) at the contact surface migrates into the host material, here being the concrete, and gradually decreases with depth from the surface.
The mathematical model never reaches zero concentration due to the properties of exponential functions, therefore practically, one chooses a very small cut off point at which it can be assumed the concentration has essentially reached zero.
The licensee chose the cut off in this case to be the depth at which the surface activity concentration was decreased by 100,000 times.
Actual activity at this level would be impossible to measure and is several times below natural background levels of radiation.
This depth was calculated be to approximately one inch.
To be more conservative, the licensee assumed that all of the calculated activity in the one inch of concrete was uniformly near the surface.
Based on this conservative assumption it would be contained in the first one-tenth of an inch.
This assumption was used in the exposure pathway dose calculations.
The licensee calculated the total activity by integrating the concentration to this depth over the entire surface area of the concrete blocks.
The licensee indicated in the application that several conservative assumptions were made in calculating the total activity content of the concrete.
First, the surface area was calculated based on total volume of concrete and a uniform thickness of two feet.
This effectively
creates approximately 25 percent more potentially contaminated surface area than actually exists.
Second, all surfaces were assumed to be equally contaminated.
Due to the presence of the protective steel liner
- plate, any contamination on the inner concrete surface is expected to be small relative to that measured on the outer surface.
Table 1
indicates the licensee's total calculated activity of each radionuclide based on both the average of the sample concentrations and on the maximum concentrations measured in the surface.
Table 1
Radioactivity Content of the Doghouse Concrete Nuclide Half-life (years)
Ave.
Based Max.
Based Ave.
Conc.
Max.
Conc.
Activity Activity (pCi/gm)
(pCi/Gm)
(uCi)
(uCi)
Co-60 5.3
- 1. 33
- 2. 70 7.8
- 16. 0 Cs-134
- 2. 1 Cs-137
- 30. 0
- 0. 33
- 2. 60
- 0. 70
- 7. 70 1.9
- 15. 4
- 45. 6 Total
- 4. 26
- 11. 10
- 25. 1
- 65. 7 Prior to disposal, items embedded in the concrete such as equipment
- supports, anchor bolts, and conduit and piping restraints shall be cut off flush with the concrete surface.
The painted surface of the concrete will be removed to a minimum depth of 1/16" into the underlying concrete by a mechanical scarifying process.
The decontaminated blocks will again be surveyed prior to release for disposal.
Any areas on the blocks which do not meet radiation protection release criteria, or exceed the assumptions made in the radiation dose evaluation of the application, will be further decontaminated prior to release for disposal.
~
~
~
The proposed disposal method for the concrete blocks is to remove them to an area outside the protected area fence, but within the Donald C.
Cook Nuclear Plant site boundary.
The Cook Nuclear Plant is located in Lake Township, Berrien County, Michigan, approximately 11 miles South-Southwest of the center of Benton Harbor, Michigan.
The plant site consists of approximately 650 acres situated along the eastern shore of Lake Michigan.
A more detailed description of the plant site area can be found in the "Final Environmental Statement Related to Operation of Donald C.
Cook Nuclear Plant Units 1 and 2" (FES), August 1973.
The chosen site is presently the site of concrete spoils and other construction remnants left from the construction of the plant.
The site is more than 200 yards away from any area occupied by plant personnel on any regular basis, and is 150 yards away from Thornton Road.
The site is also surrounded by earthen mounds on all sides, with the exception of the access point.
Once the concrete is in place, it will not be visible except at the access point. It has not yet been determined whether or not the slabs wil] be stacked or individually laid down, but the maximum actual area occupied by the blocks will be less than 20 x 25 yards.
An evaluation of the potential radioactive dose to a plant site worker and to a member of the general public was performed by the licensee to determine the radiological impact of placing the concrete in the proposed location.
The calculations were performed using applicable methodologies in Regulatory Guide 1.109, NUREG/CR-3332, and Introduction to Health Ph sics, Cember.
The licensee, in the application, stated all potential exposure pathways recommended by Regulatory Guide 1.109 were evaluated with the exception of potential dose from incineration of the waste.
There is no feasible scenario by which the concrete would be burned.
The licensee's evaluation consisted of a determination of the environmental pathways through which radiological exposure could be expected to occur and an evaluation of the radiological consequences of the disposal of the concrete for each of the pathways considered.
The following environmental pathways were considered:
(1)
External exposure from the concrete - occupational and intruder (2)
Internal exposure due to release of contaminants to surface and ground water - ingestion of drinking water, fish and other aquatic
- foods, and well water (3)
Internal exposure due to agricultural activities on the disposal site following loss of institutional control-ingestion of vegetables, meat and diary products (4)
Internal exposure due to inhalation of resuspended contaminated concrete dusts - occupational, and intruder following loss of institutional control This evaluation demonstrates that any doses to occupational
- workers, intruders, and members of the general public would be very small, and far lower than the levels permitted for unrestricted areas by 10 CFR
- 20. 105.
"8-In the FES for the operation of D.
C.
Cook, the Commission's staff considered the potential effects on the environment of licensed material from operation of the plant and, in the summary of radiological
- impacts, concluded that "...the routine operation of the Cook Station is expected to add only a small increment to the natural background dose."
"...these doses correspond to concentrations which are a small percentage of permissible standards set forth in 10 CFR Part 20.
Since the disposal proposed in the licensee's application dated February 29, 1988, involves licensed materials containing much less than
- 0. 1 percent of the radioactivity, primarily Cobalt-60, Cesium-134, and Cesium-137, already considered acceptable in the
- FES, and involve exposure pathways much less significant and radiochemical forms much less mobile than those considered in the FES, the Commission s staff considers this site-specific application for the D.
C.
Cook Nuclear plant to have insig-nificant radiological impact.
The Commission s staff accepts the evaluations of the licensee documented in Attachment 1 of the February 29, 1988, application as further assurance that the proposed disposal procedures will have a negligible effect on the environment and on the general population in comparison to normal background radiation.
Alternatives to the Pro osed Action:
An alternative to on-site burial would be to ship and dispose of the concrete slabs at an offsite 'licensed disposal site.
The overall benefit from the proposed method for the disposal of these slightly contaminated concrete slabs will be a cost saving of approximately
$1.6 million and a saving of burial site space of approximately 16,000 cubic feet, which can be used for other radwaste of higher activity.
The alternative would not be environmentally preferable.
Alternative Use of Resources:
This action involves no use of resources not previously considered in connection with the "Final Environmental Statement Related to Operation of Donald C.
Cook Nuclear Plant Units 1 and 2" dated August 1973.
A encies and Persons Consulted:
The Commission's staff reviewed the licensee's request and did not consult other agencies or persons.
FINDING OF NO SIGNIFICANT IMPACT The Commission has determined not to prepare an environmental impact statement for the proposed action.
Based upon the foregoing environmental assessment, the Commission concludes that the proposed action will not have a significant effect on the quality of the human environment.
For further details with respect to this action, see the application dated February 29, 1988, which is available for'ublic inspection at the Commission s Public Document
- Room, 1717 H Street, NM.,
Mashington, DC, and at the Maude Preston Palenski Memorial Library, 500 Market Street, St.
day of August 1988.
FOR THE NUCLEAR REGULATORY COMMISSION J~
Q Martin J. Yirgilio, Director Project Directorate III-1 Division of Reactor Projects - III, IV, V 8 Special Projects