ML20057B953
| ML20057B953 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 09/15/1993 |
| From: | Long R GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20057B954 | List: |
| References | |
| C-93-2202, C000-93-2202, C312-93-2063, NUDOCS 9309240202 | |
| Download: ML20057B953 (5) | |
Text
1 1
GPU Nuclear Corporation Q
f Post Office Box 480 Route 441 South Middletown, Pennsylvania 17057-0191 717 944 7621 TELEX 84 2386 Writer's Direct Dial Number:
(717) 948-8400 September 15, 1993 C312-93-2063 C000-93-2202 US Nuclear Regulatory Commission Attn: Document Control De.sk Washington, DC 20555 Three Mile Island Nuclear Station Unit 2 (TMI-2)
Operating License No. DPR-73 Docket No. 50-320 Contamination Estimate for Two TM1-2 AFHB Cubicles Dear Sir-The Post-Defueling Monitored Storage (PDMS) Safety Analysis Repon (SAR), Supplement 4, Question No. I requested an estimate of the total quantity of contamination in the Auxiliary and Fuel Handling Buildings (AFHB). As agreed, GPU Nuclear would provide an assessment of the quantity of contamination in two AFHB cubicles for NRC review. If the methodology used to assess the contamination was acceptable to the NRC, contamination in the rest of the AFHB would be so estimated. provides the methodology for estimating the curie loading of the TMI-2 AFHB cubicles and other areas. As stated therein, an initial estimate of the curie loading in each cubicle / area will be made using a simplified model.
Based on peliminary estimates, approximately 95 % of the contamination in the AFHB is contained in nine cubicles / areas. Those nine cubicles / areas will then be evaluated to determine whether to construct a more precise model based on their propensity for significantly increasing the original curie estimate.-
The assessment of the two cubicles / areas chosen for assessment by NRC are included as Enclosures 2 and 3. The enclosums present the calculations of the curie loading in the two makeup demineralizers and the "A" spent fuel pool, respectively. It its notewonhy that these areas represent several of the more difficult cubicles / areas to evaluate.
j230C60 9309240202 930915 Es 1I PDR ADOCK 05000320 W Y\\
'\\
(
GPU Nuclear Corporation is a subsid:ary of General Pubhc Utikt:es Corporation s
4 Document Control Desk September 15, 1993 C312-93-2063 C000-93 ^";
i Page 2 l
I As stated above, NRC acceptance of the methodology is necessary for completion of the AFHB contamination estimates. However, GPU Nuclear shall proceed under the assumption that the methodology described in Enclosure 1 is acceptable and will calculate the total quantity of l
contamination in the AFHB accordingly.
Sincerely,
[
Q 8
R. L. Long Director, Services Division /TMI-2 EDS/dlb Enclosures l
cc:
M. Evans - Senior Resident Inspector, TMI T. T. Martin - Regional Administrator, Region I M. T. Masnik - Project Manager, PDNP Directorate L. H. Thonus - Project Manager, TMI 1
l l
i I
i l
i i
't ENCLOSURE 1 Methodology for Estimating the Curie Iradine of the TMI-2 Auxiliary and Fuel Handling Building Cubicles and Other Areas INTRODUCTION While the majority of the radioactive contamination resulting fmm the TMI-2 reactor accident of 1979 remains within the TMI-2 Reactor Building, approximately 145 locations within the Auxiliary and Fuel Handling Buildings (AFHB) and other areas are listed in the Post-Defueling Monitored Storage (PDMS) Safety Analysis Report (SAR) as locations (cubicles / areas) containing some levels of radioactive contamination. Some of these cubicles / areas were exposed to radioactive material concentations that left them severely contaminated. Others were only moderately contaminated, and r,ome cubicles were largely unaffected by the accident and the subsequent defueling operations.
Prior to entering PDMS, GPUNC has committed to provide an estimate of the curie content of these cubicles / areas showing the estimated total activity (fixed and removable), that will be present upon entry into PDMS. To provide specific (room-by-room) estimates that pmvide the curie content at some level of accumcy is a difficult task if each room or area were to be modeled precisely.
Constructing an exact representation of each ama/ cubicle, including equipment and room size, would expend many man-hours. The end product would still be an estimate with an error band of appmximately i 50%.
To simplify this task, most of the locations will be modeled using the Microshield radiation shielding computer code, a common geometry for all areas, and the average general area radiation survey reading as the modeling parameters. A few of the areas containing the majority of the contamination will be modeled more precisely. The below listed assumptions are necessary to the simplify this effort.
ASSUMPTIONS l
1.
The radioactive material within a selected area is composed of typical TMI-2 isotopes than can be classified into one of three groups: Defueling, Make-up and Purification (MUP), or Normal waste. These TMI-2 classifications are used to represent materials for waste shipments and are based on specific isotopic distributions.
2.
The " Average General Area". radiation measurement for a selected room is the average j
of a number of measurements taken from a typical TMI-2 Radiological Controls Survey -
as described in GPUNC Radiological Controls Pmeedure 6610-ADM-4200.04 and GPUNC Radiological Controls Standing Order Memorandum 6610-92-53.
)
i
i 1
-3.
The geometry used for modeling a cubicle / area having a small quantity of radioactive material (i.e., less than 50 curies) is typically a cylinder with an internal exposure rate point. The cylinder's size is increased or decreased depending on the actual size of the room. For example, a room that is 18 feet wide,20 feet long and 21 feet high has a total surface area of 2,316 square feet. The internal cylinder model for this room would have a diameter of 19.5 feet ((18+21)/2) and a length of 37.8 feet. The total internal surface area for the model is the same, i.e., about 2,316 square feet.
4.
Cubicles that do not have a rectangular floor are considered to be rectangular, by choosing the longest path through the room as the length of the room. This path may be diagonal for some areas but will always represent a conservative room size. The width of some cubicles may be determined in a similar fashion.
s 5.
Equipment and other obstructions are ignored in estimating the room size. Only the outermost walls are considered.
6.
The equipment or piping in a cubicle is not considered to be the deposition site of the radioactive material.
7.
All of the radioactive material is equally distributed over the interior of the cylindrical model.
8.
The exposure rate site is about head-high at the center of the room.
9.
For those cubicles containing greater than 50 curies based on previous knowledge or the i
above modeling technique, an engineering evaluation will be made to determine whether to construct a more precise model. The propensity for measurably increasing the original curie estimate will be the determining factor in this decision process. A preliminary estimate indicates that the AFHB contains greater than 10,000 curies; therefore, a
" measurable increase" is presumed to be 50 curies (i.e.,0.5% of the total). The more precise model will be developed using the actual room dimensions, specific equipment involved and other relevant information (e.g., contained water).
EFFECT OF ABOVE MODELING TECHNIOUE The method outlined above will produce a reasonable estimate of activities for the AFHB and -
4 other areas since approximately 95 % of the activity is contained in the nine cubicles / areas within the AFHB having greater than 50 curies. Each of these nine cubicles will be evaluated to 1
determine whether a more precise model should be developed. This is an effort to apply the i
greatest precision to the areas where most of the activity resides. The other cubicles individually contain much less activity; minor inaccuracy in modeling these cubicles will have an insignificant impact on the final total inventory.
The cubicles / areas modeled using the equivalent cylindrical surface area technique will provide a conservative estimate of the activity present, since the activity will be assumed to b6 on the inside surface of the cylinder and not in the equipment or piping in the room. In addition, the i
1 curies associate ' with any fuel debris previously determined to be present in a mom or ama, will be added to the. Jvity estimated from the exposure rate modeling. Since the number of curies present in fue..
. iris is generally a contributor to the soume of the general area exposure rate for that room,
" double-counting" of curies for these locations will take place, resulting in an ovemstimate of the total activity in the cubicle.
SUMMARY
The methodology described above will optimize the use of GPU Nuclear's time, resources and analytical ability to estimate the number of curies present in the cubicles / areas containing the largest amount of activity (i.e., those accounting for about 95% of the total). The remaining cubicles / areas will be estimated with less accuracy using the equivalent cylindrical technique to reduce the number of modeling problems.
1 i