ML20043B294
| ML20043B294 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 05/17/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20043B293 | List: |
| References | |
| NUDOCS 9005290003 | |
| Download: ML20043B294 (11) | |
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l SAFETY ASSESSMENT BY THE OFFICE OF NUCLEAR REACTOR REGULATION YANKEE ATOMIC ELECTRIC COMPANY YANKEE NUCLEAR POWER STATION DOCKET NO.50-029 t
1.0. INTRODUCTION By letter of April 11, 1990, the Yankee Atomic Electric Company (Yankee).
submitted, pursurnt to 10 CFR 20.302(a), a method for the routine disposal of septic tank waste containing very low levels of licensed material. Yankee proposed to periodically dispose of accumulated septic waste solids from the plant's sanitary system septic tank by transferring them to a public Sanitary Waste-Water Treatment Facility (SWTF) where they will be mixed with - processed with, and disposed es part of the sanitary waste generated from many sources.
Yankee proposed to make such disposals every one to two years over a period of 1
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30 years.
l In.the submittal, the licensee addressed specific information requested in accordance with-10 CFR 20.302(a), provided a detailed description of.the
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licensed materiel, thoroughly analyzed and evaluated the information pertinent p
to the effects on the environment of the proposed disposal of the licensed material, and committed to follow specific procedures to minimize the risk of l
unexpected or hazardous exposures.
1 9005290003 900517 PDR ADOCK 05000029 P
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2.0 WASTE WATER STREAM DESCRIPTION 2.1. Physical and Chemical Properties The waste involved consists of residual septage (the accumulated settled and suspended solids and scum) produced by the sanitary sewerage collection and treatment system at the Yankee plant. To safely dispose of the plant's sanitary waste stream, the Yankee plant supplements the onsite septic system supplemented with offsite treatment at a SWTF.
The onsite septic system consists of a 7,000-gallon buried septic tank and a subsurface soil-absorption leach field.
In the overall system design, the septic tank collects sludge.and scum and partially separates liquids from the incoming sanitary waste.
The septage is retained in the septic tank, and the remaining conditioned waste-water liquid flows into the underground leaching field for treatment.
The leach field is the terminal point of the onsite portion of the plant sanitary waste treatment process.
In the offsite portion of this process, the septage is removed from the septic tank and transported to a SWTF.
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2.2 Radiological Properties The plant's sanitary system septic tank collects waste from the lavatories, showers, and janitorial facilities outside the Radiological Control Area (RCA).
'No radioactivity is intentionally discharged to the septic system.
- However, plant investigations into the source of low levels of licensed material found
-in septic tank waste have identified very small quantities of radioactive materials, which are below detection limits for radioactivity releases from the RCA.
It is suspected that these materials are carried out of the control area on individuals and spread to floor areas outside the RCA.
Floor wash water from these areas is poured through a filter bag to remove suspended solids and dirt before the water is released into a janitorial sink.
Although the wash water is returned to the RCA for disposal, if it is known to contain radioactivity, very small quantities can be released to, and accumulate in the sceptic tank.
The following values are estimates of the maximum total activity presently in the septic tank based on measurements of radionuclide concentrations in the liquid and solid phases:
Total Activity Nuclide (uCi)
Co-60 1.94 Mn-54 0.057 Cs-134 0.082 Cs-137 0.248 TOTAL 2.33
a' 3.0 pR0p0 SED DISP 0 SAL METHOD Yankee proposes to periodically dispose of accumulated septage from its septic tank by contracting with a septic tank pumper that is approved by the Board of Health, Rowe, Massachusetts and transfer the septage to a Massachusetts SWTF for treatment. This septic tank pumper will transfer the septage to an SWTF, where it is mixed and diluted with other raw sewage and introduced either into an anaerobic digester or an aeration pond for biological treatment. The resulting processed sludge from the SWTF is then mixed with sand and disposed of in a sanitary landfill, where it will be covered by clean soil daily. An alternate disposal means could result in the processed sludge being' spread as a fertilizer, though generally for vegetation, such as sod, which is not consumed by humans. None of the region's SWTFs that receive sewage from local septic tank pumpers incinerate their sludge as a means of treatment.
This method of pumping the tank and transferring the septage to an SWTF is the same method normally applied to septic tank systems, regardless of the presence of licensed material.
3.1 Septic Tank Waste Procedural Requirements and Limits The licensee will perform a gamma isotopic analysis on a representative sample of waste from the septic tank no more than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> before a contracted septic tank pumper begins to pump the waste from the tank to transfer to a SWTF.
The licensee will collect at least two septage samples from the plant's septic tank by taking a volumetric columr. sample that will allow the licensee to
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-determine the ratio of the solid content to the total content of the tank. By determining the weight of the percentage of solid content of the collected sample and applying this value to the gamma isotopic analysis, the licensee will be able to estimate the total radioactivity of the contents of the tank.
To document the estimation of radiological effect of septage disposal, t.he licensee will perform these gamma isotopic analyses of.the representative samples attheTechnicalSpecificationEnvironmentalLowerLimitofDetection(LLD) requirements for liquids, as required in Technical Specification Table 4.12-1,
" Detection Capabilities for Environmental Sample Analysis,"
The radionuclide concentrations and total radioactivity identified in the septage will be compared to the concentration and total curie limits established herein before disposal. The following limits apply to these anaiyses:
1.
The concentration of radionuclides detected in the volume of septage to be pumped to a disposal truck shall be limited to a combined sum of fractional Maximum Permissible Concentrations in
' Water (MPC) (as listed in 10CFR Part 20, Appendix B, Table II, Column 2), summed over all nuclides present, of less than or equal to 1.0.
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The total gamma activity that can be released during septage transfer to any SWTF or combination of such facilities in one year (12 consecutive-months) is limited to not more than 20 microcuries (equivalent to a maximum whole-body dose of 1 mrem to any individual in the public).
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A 6-3.2 Administrative Procedures s
The licensee will maintain complete records of each disposal.
In addition to copies of invoices with approved septic tank pumpers, these records will include the concentration of radionuclides in the septage, the total volume of septic waste disposed, the total activity in each batch, and the total accumulated activity of the septage pumped in any 12 consecutive months.
For periods in which disposal of septage occurs under this application, the-licensee shall report, to the Nuclear Regulatory Commission (NRC) in the plant's Semiannual Effluent Release Report, the volume, liquid, and solid mass fractions, radionuclide concentrations in the liquid and solid fractions, and the total activity disposed, 4.0 EVALUATION OF ENVIRONMENTAL IMPACT The proposed method for disposal of septage is the same as currently used by u
all facilities designed with septic tanks for the collection of septic waste.
'No new structures or facilities need be built or modified, nor any existing land uses changed.
Septage from Yankee will be transported to an existing SWTF, where it will make up a small fraction of the total volume of sanitary waste treated each year.
The normal method of septage handling and treatment
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would involve dilution of Yankee's septage with other waste-water at a public
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SWTF. The processed sludge from the SWTF is usually buried in a sanitary landfill, thus limiting the potential exposure pathways to man. Otherwise, the sludge is widely dispersed in fertilizer, thereby preventing any buildup of activity from successive annual pumpouts from the plant's septic tank. This method of disposal will oct affect topography, geology, meteorology, hydrology, or nearby fecilities.
5.0 PAD 10t0GICAL IMPACTS The licensee has evaluated the following potential exposure pathways to members of the general public:
(1) inhalation of resuspended radionuclides, (2) ingestion of food grown on the disposal site, (3) external exposure to a truck driver or SWTF worker, and (4) external exposure caused by long-term buildup and external exposure from standing on the ground above the disposal site. The staff has reviewed the licensee's calculational methods end assumptions, and finds that they are consistent with regulatory Guide 1.109.1 The staff finds the assessment methodology acceptable, l
l 1 Regulatory Guide 1.109, "Calculetion of Annual Doses to Man from Routine Releases
.of Rt. actor Effluents for the Purpose of Evaluatins Compliance Vith 10 CFR Part 50, i
AppenrHy I." Revisicn 1, October 1977.
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'4 Doses calculated in this manner by the licensee for the maximum exposed member-
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of the public were as follows (based on a total activity awaiting disposal I
of 2.3 pCi, more.than 80% of which is Co-60):
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t Maximally Exposed 6
. Individual /Whole Body (Child)
Pathway (mrem / year)
Ground Irradiation 0.099 Inhalation 0.0001 Stored Vegetables 0.0214 Leafy Vegetables 0.0011 Milk Ingestion *
(0.0036)
TOTAL 0.12 i
The licensee then performed a similar calculation using a concervative upper bound activity of 20 pCi to be discharged in any one year.
Based on this upper bound analysis, the dose to the maximally exposed individual member of
. the general public was estimated to be 1.1 mrem / year, as shown in the following table:
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Maximally Exposed i
Individual /Whole Body Pathway (arem/ year)
Ground Irradiation 0.980 inhalation 0.0004 Stored Vegetables 0.13 l
a Leafy Vegetables 0.007 4
TOTAL 1.1 Based on this same total activity, the dose to truck drivers and SWTF workers
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was estimated to be 0.01 mrem /yr.
These doses are within the-design objectives of 10 CFR 50, Appendix I and well within the environmental standards for uranium fuel cycle activities as stated in 40~CFR 190.10(a) and are therefore acceptable.
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SUMMARY
AND CONCLUSIONS-I i
i The disposal of septage by-transferring it to a public SWTF is in accordance with standard practices for treatment of the type of waste material generated by a septic tank and leach field sanitary waste system.
Periodic pumping of the septic tank is necessary for the maintenance and continued operation of Yankee's i
sanitary waste system.
Yankee requested approval for disposal of septic waste from the Yankee sanitary system to prevent failure of the sanitary system to adequately handle plant domestic waste.
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An alternate means of disposal would involve the treatment of the septage as radwaste.
Such a disposal would require that the licensee stabilize, solidify, and dispose of the material at a licensed burial ground, requiring excessive-cost and valuable disposal ground, i
The results of the radiological analysis indicate that the public health effects of the biological activity and pathogenic constituents of such sanitary waste far outweigh the concerns related to any radioactivity that is present.
By setting release limits that restrict the exposure for an individual to a maximum value of 1 millirem per year, Yankee-ensured that radiological risks 4
from the proposed disposal method are insignificant.
The proposed release limits represent a small fraction of NRC limits permitted for disposal of similar waste by licensed facilities who have their sanitary l
systems connected directly to a public sanitary sewerage system.
These proposed
' limits are also well within the plant's allowable release limits for the discharge 1
of normal liquid waste to the environment.
Any resulting dose to any individual in.the public is less than exposurec caused by natural background radiation.-
Based on our review of the proposed disposal of septage, the staff makes the following conclusions:
(1) the radionuclide concentrations in disposed septage will be a small percentage of permissible standards set forth in 10 CFR Part 20; (2) the radiation risk to workers involved in the disposal would be small compared to the routine occupational exposures at the Yankee Nuclear Power Station; (3) because the proposed action involves such very low levels of radioactivity, it will require no change in the decommissioning aspects of the
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facility and will require'only insignificant changes in the handling or transport of radioactive material (septage);
and (4) the licensee's procedures with commitments as documented in the submittal are acceptable, provided that the submittal is permanently incorporated into the licensee's 0ffsite Dose Calculation-Manual (ODCM) as an Appendix, and future modifications will be reported to NRC in accordance with licensee commitments regarding ODCM changes, Contributors:
J. Minns i
P, Sears x
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