ML022750270

Dcgl Tables and Bounding Equation Submittal

ML022750270
Person / Time
Site:	Saxton File:GPU Nuclear icon.png
Issue date:	09/17/2002
From:	Kuehn G GPU Nuclear
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
-nr, E910-02-044
Download: ML022750270 (4)

Text

GPU Nuclear, Inc.

o P U Three Mile Island Nuclear Station NUCL EAR Route 441 South Post Office Box 480 Middletown, PA 17057-0480 Tel 717-948-8461 September 17, 2002 E910-02-044 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Gentlemen,

Subject:

Saxton Nuclear Experimental Corporation (SNEC)

Operating License No., DPR-4 Docket No. 50-146 DCGL Tables and Bounding Equation Submittal On September 12, 2002, two electronic files were e-mailed to you. These files contained an Excel spreadsheet with the latest SNEC DCGLs and a Word document with a bounding equation to calculate radiation dose. The purpose of this letter is to provide you with the hardcopy information that was contained in the e-mail. These hardcopies are attached for your information.

If you have any questions on this information, please contact Mr. James Byrne at (717) 948-8461.

Sincerely, Program Director, SNEC cc: NRC Project Manager NRC Project Scientist, Region 1

SNEC DCGLs 25 mrem/yr Limit Isotope DCGL (pCi/g)

Model - All Pathways Scenario Dose Run File Location 1 Am-241 9.9 Subsurface - Undisturbed Bedrock AW-Bedrock\\Am-241\\Deterministic\\Summary.REP C-14 2

Subsurface - Spray Pond Overburden AW-Overburden\\C-14\\Deterministic\\Summary.REP Co-60 3.5 Surface - Upper 1 Meter of Soil ALL RUNS\\NEW CO-60\\NEW C060.SUM Cs-137 6.6 Surface - Upper 1 Meter of Soil ALL RUNS\\NEW CS-137\\NEW CS137.SUM Eu-152 10.1 Surface - Upper 1 Meter of Soil ALL RUNS\\NEW EU-152\\NEW EU152.SUM H-3 132 Subsurface - Undisturbed Bedrock AW-Bedrock\\H-3\\Deterministic\\Summary. REP Ni-63 747 Surface - Upper 1 Meter of Soil ALL RUNS\\NEW NI-63\\NEW N163.SUM Pu-238 1.8 Subsurface - Undisturbed Bedrock AW-Bedrock\\Pu-238\\Deterministic\\Summary.REP Pu-239 1.6 Subsurface - Undisturbed Bedrock AW-Bedrock\\Pu-239\\Deterministic\\Summary.REP Pu-241 86 Subsurface - Undisturbed Bedrock AW-Bedrock\\Pu-241\\Deterministic\\Summary.REP Sr-90 1.2 Surface - Upper 1 Meter of Soil ALL RUNS\\NEW SR-90\\NEW SR90.SUM 4 mrem/yr Drinking Water (DW) Goal Isotope DCGL (pCilg)

Model - DW Scenario Dose Run File Location Am-241 2.3 Subsurface - Undisturbed Bedrock Bedrock\\DW From BedrockýAm-241\\Deterministic\\Summary.Rep C-14 5.4 Subsurface - Undisturbed Bedrock Bedrock\\DW From Bedrock\\C-14\\Deterministic\\Summary.Rep Co-60 67 Subsurface - Undisturbed Bedrock Bedrock\\DW From Bedrock\\Co-60\\Deterministic\\Summary.Rep Cs-1 37 397 Subsurface - Undisturbed Bedrock Bedrock\\DW From Bedrock\\Cs-137\\Deterministic\\Summary.Rep Eu-1 52 1440 Subsurface - Undisturbed Bedrock Bedrock\\DW From Bedrock\\Eu-1 52\\Deterministic\\Summary.Rep H-3 31.1 Subsurface - Undisturbed Bedrock Bedrock\\DW From Bedrock\\H-3\\Deterministic\\Summary. Rep Spray Ponds\\Overburden\\DW From Overburden\\Ni Ni-63 1.90E+04 Subsurface - Undisturbed Overburden 63\\Deterministic\\Summary.Rep Pu-238 0.41 Subsurface - Undisturbed Bedrock Bedrock\\DW From Bedrock\\Pu-238\\Deterministic\\Summary. Rep Pu-239 0.37 Subsurface - Undisturbed Bedrock Bedrock\\DW From Bedrock\\Pu-239\\Deterministic\\Summary.Rep Pu-241 19.8 Subsurface - Undisturbed Bedrock Bedrock\\DW From Bedrock\\Pu-241\\Deterministic\\Summary. Rep Sr-90 0.61 Subsurface - Undisturbed Bedrock Bedrock\\DW From Bedrock\\Sr-90\\Deterministic\\Summary.Rep Footnote 1: Subsurface files are found in URS CD ROM disks. Surface files are found on SNEC CD ROM disks.

6.2.1 Building Occupancy Scenario For the two-dimensional surface area model, the building occupancy scenario is used as the best representation. This model applies to the SNEC Containment Vessel (CV), SSGS, tunnels and/or other impacted site structures. Since these structures will either be demolished or left behind, the building occupancy scenario is most representative. Other buildings (garages and support structures) left behind will be surveyed and released using the building occupancy scenario. DandD Version 1.0 has been used as the preferred modeling software for the building occupancy scenario.

The exposure pathways selected for analysis in the building occupancy scenario include external exposure to penetrating radiation from surface sources, inhalation of resuspended surface contamination, and inadvertent ingestion of surface contamination. The selection of these pathways provides a balanced analysis for a) External exposure to penetrating radiation from surface sources; b) Inhalation of resuspended surface contamination; c) Inadvertent ingestion of surface contamination; and d) External exposure to penetrating radiation from embedded sources.

This scenario accounts for exposure to both fixed and removable thin-layer or surface radioactivity within a structure. This scenario assumes individuals (critical group) occupy the building in a passive mode without deliberately disturbing the residual radioactivity on building surfaces. Occupancy of the building is assumed to begin immediately after license termination. The exposure duration is assumed to be a full work year (approximately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />). The selection of this scenario assumes the following site conditions will exist to qualify:

1. The contamination on building surfaces (e.g. walls, floors, and ceilings) should be surficial and non-volumetric.

2. Contamination on surfaces is mostly fixed (not loose) with the fraction of loose contamination not to exceed 10% of the total surface activity.

3. This screening criteria will not apply to surfaces such as on buried components or conduit (e.g. drainage or sewer pipes). Such component and conduit surfaces will be treated on a case by case basis.

Surface contamination DCGLs were developed through the use of the DandD computer code using the standard default parameters. The results from the DandD runs for each of the 11 site related radionuclides are in units of mrem TEDE per dpm/1 00 cm 2. Default surface area DCGLs (Reference 6-8) are listed in Table 6-2. These default values were verified using DandD. The DandD output for the building occupancy scenario model is contained in Appendix 6-1.

Building and component surfaces will be decontaminated to as low as reasonably achievable to meet the release criteria building occupancy screening levels. For building debris that cannot be assessed using the surface screening criteria, a volumetric assessment of the materials will be made. These materials will be characterized (if not already known) as to radionuclide contaminant(s), type of material, corrosivity rates (metals),

and leach rates (concrete/debris) for input. This switch to volumetric consideration brings the resident farmer scenario back as the release scenario. Since some of the material will

be buried 3 feet below grade the contamination zone may be in the saturated zone. A subsurface volumetric dose model has been developed to evaluate this condition.

Exposure pathway (d) listed above applies to areas where there is penetrating radiation from embedded sources of radioactivity, such as embedded piping. To the extent practical embedded sources will be encapsulated in a grout/concrete matrix. For modeling this scenario a bounding calculation using sum of the fractions method will be employed. This method will combine applicable surface and volumetric DCGLs along with a shielding code (e.g. MicroShield) to calculate the respective dose from residual activity remaining on structural surfaces, within residual piping, walls and floors or within activated metal (e.g. CV steel liner). Use of Equation 6-1 will ensure the combined exposure is bounded for all applicable sources and less than the 25 mrem/yr limit.

Equation 6-1

+

CG

) [Direct y Dose]

,=1DG, DCGL,,, )

25

<1 Where: Csi = Surface contamination of radionuclide i (dpm/lO0 cm2).

Cvj = Specific volume concentration of radionuclide i (pCi/g).

DCGLSi = Surface contamination DCGL of radionuclide i from Table 6-2.

DCGLVi = Volumetric DCGL (25 mrem/yr) of radionuclide i from Table 6-2.

Direct y Dose = Microshield (or equivalent) shielding code calculation (mrem/yr).