ML20084F104
| ML20084F104 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 04/20/1984 |
| From: | Zimmerman S CAROLINA POWER & LIGHT CO. |
| To: | Vassallo D Office of Nuclear Reactor Regulation |
| References | |
| NLS-84-178, NUDOCS 8405030124 | |
| Download: ML20084F104 (5) | |
Text
_
a Cp&L Carolina Power & L!ght Company APR 2 01984 SERIAL: NLS-84-178 j
Director of Nuclear Reactor Regulation Attention:
Mr. D. B. Vassallo, Chief Operating Reactors Branch No. 2 Division of Licensing United States Nuclear Regulatory Commission Wasnington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS. 1 AND 2 DOCKET NOS. 50-325 & 50-224/ LICENSE NOS. DPR-71 & DPR-62 REQUEST FOR ADDITIONAL INFORMATION ON BURNING OF WASTE OIL
Dear Mr. Vassallo:
In a letter dated February 15, 1984, Carolina Power & Light Company (CP&L) was requested to provide some additional information concerning the combustion of waste oil at the Brunswick Steam Electric Plant (BSEP).
Please find enclosed our responses to the questions raised by your staff.
Should you have further questions, please contact a member of our Licensing Staff.
Yours very truly, S
R.
Immerman Manager Nuclear Licensing Section PPC/gvc (9865PPC)
Enclosures cc:
Mr. D. O. Myers (NRC-BSEP)
Mr. J. P. O'Reilly (NRC-RII)
Mr. M. Grotenhuis (NRC)
PDR ADOCK8405030124 040420 05000324 P
PDR 411 Fayettevette Street
- P. O. Box 1551
- Haleigh. N C. 2760
i RESPONSE TO A REQUEST FOR ADDITIONAL INFORMATION BRUNSWICK STEAM ELECTRIC PLANT DOCKET NOS. 50-324/325 EVALUATION OF BRUNSWICK REQUEST TO BURN CONTAMINATED OIL CP&L is requesting permission 'o burn contaminated oil in both an auxiliary boiler and a clean trash incinerator.
Questions related to solids retention, solids disposal, and occupational exposure are addressed for both of these options.
Question Provide the quantities of radioactive materials that may be retained by dust collection systems, ash collection systems, and other portions of the combustion system and the means to be provided for disposal of these radioactive materials.
Response
The auxiliary boiler has no ash or dust collection systems because No. 2 fuel oil has < 0.01 percent ash (Table 9-11, Chemical Engineers Handbook, Perry and Chilton).
A thin layer of soot is deposited in the fire tubes, smoke boxes, and stack.
Routine periodic maintenance or the detection of measurable levels of radiation could present occasions for cleaning out this soot.
All such maintenance procedures will follow applicable OSHA and NRC guidelines.
CP8L's request states that the total quantity of radioactivity which may be released from the site by combustion of waste oil shall be limited to 50 pCi per calendar year. As indicated in the appendix to our applica-tion of November 21, 1983, the only isotope routinely seen in cleaned waste oil is Co-60.
If 50 Ci of Co-60 was deposited on the walls of the auxiliary boiler and was depleted only by radioactive decay, then the max-imum total activity can be determined using the decay equation for secular equilibrium (Introduction to Health Physics, Herman Cember,1st edition,
- p. 98).
In secular equilibrium, an isotope is assumed to be formed (or in 1
\\
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this case, introduced to the boiler) at a constant rate and to decay expo-nentially at a rate governed by its decay constant, A.
Using ' this
- equation, ACo-60
- x (1 - e
)
Co-60 Where: ACo-60 = activity of Co-60 in pCi at time t K = " formation" rate of Co-60 = 50 pCi/ year
-A t
(1 - e Co-60 As t + =, ACo-60
- xCo-60 ACo-60 = 379 pCi This value, 379 Ci, is the equilibrium value (point at which rate of formation = rate of decay).
This is the largest possible activity that could be present in the boiler.
This value would be approached in 20-30 years.
The auxiliary boiler to be used is a Johnston fire tube boiler.
The design of this boiler features a steel shell which encloses water-jacketed fire tubes. As mentioned, soot will deposit in these fire tubes, in smoke boxes, and in the stack.
The activity in the fire tubes would be well shielded by the water and steel.
The smoke boxes and stack are manufac-tured of 10-gauge steel which provides very little shielding.
If all 379 pCi were deposited at a point on the smoke box, the 1-foot exposure rate would be approximately 6 mR/hr from a Co-60 source (from 6CEn approxima-tion of a gama point source).
This rate could only be achieved if all the Co-60 introduced into the boiler collected at one point for a period of 30 years or more.
In conclusion, the auxiliary boiler will produce no solid waste for disposal (other than a slight soot buildup) and will under all conditions contribute only negligible occupational exposures.
The alternative disposal route is to use a clean trash incinerator.
Such an incinerator will be required to have a heat release capacity of at least 7,000,000 Btu /hr. At this rate, approximately 7,000 lb/ day of clean 2
O e
trash could be incinerated on an 8-hour per day burn rate.
To incinerate 12,000 gallons of waste oil per year containing 50 Ci of Co-60, a con-stant feed rate of 6 gph would be required.
For conservatism, we can assume a waste oil feed rate as high as 20 gph.
Twenty gallons has a Btu value of approximately 2,900,000. At this rate, the clean trash burn rate (based on the BSEP waste profile) would drop to ~ 4000 lb/ day.
If for conservatism a mass reduction of 20:1 is assumed, there there would be 200 lb of ash occupying 10 cubic feet generated per day (assume 20 lb/cu ft ash density).
If the 50 pCi of Co-60 is contained in 12.000 gallons of waste oil, then a 20-gph burn rate would introduce 0.67 Ci of Co-60 in an 8-hour burn.
If all the activity remained in the ash, there would be a Co-60 concentration of 2.37 x 10-6 Ci/cc in the ash.
The concentration in the ash would therefore be greater than in the waste oil.
The dose reading of a 55-gallon drum of ash (7.5 cu ft containing 5 x 10-7 Ci) can be estimated.
From Bowman and Swindle (Health Physics, November 1976, p. 445-450),
the exposure rate to curie content conversion formula is given by:
i Ci = R/hr x K x Energy conversion factor K is a conversion factor bae.ed on the dimensions of a right circular l
cylinder and the density of the material in the cylindrical container.
)
In this case, a 55-gallon drum of ash is considered with:
1 i
height = 85 cm diameter = 57 cm 3
l density of ash = 0.3 g/cm K = 0.7 l
K is determined for an average gamma energy of 0.5 MeV.
For Co-60, the average gamma energy is 1.25 MeV.
The energy correction factor, which varies with energy and density, must be applied.
In this case, the energy correction factor is given as 0.387.
Solving for R/hr, Exposure rate = 5.0 x 10-7 Ci/(0.7) (0.387) i
{
Exposure rate = 1.9 pR/hr 3
I f
Question Describe means for minimizing occupational exposures from radioactive material in the oil and from radioactive materials accumulated in the l
combustion system.
)
i
Response
t The state of North Carolina currently allows containers to be buried in the on-site clean trash lendfill with exposure readings up to 5 R/hr.
f Since the assumptions made thus far are conservative, there should be no j
special concern for handling the clean trash incinerator ash.
The work crew at the clean trash incinerator will be trained in health physics practices and issued TLDs.
Given that the cleaned waste oil and ash will have exposure rates that are ALARA, there should be no additional concerns for occupational exposure.
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