ML12025A087

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Plum Brook Reactor Facility - Technical Basis for Reevaluation of Structural Dcgls and Uranium Activity Fractions
ML12025A087
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Site: Plum Brook
Issue date: 01/23/2012
From: Kolb P
US National Aeronautics & Space Admin (NASA), John H. Glenn Research Ctr at Lewis Field
To:
Document Control Desk, NRC/FSME
References
Download: ML12025A087 (33)
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I National Aeronautics and Space Administration John H. Glenn Research Center Lewis Field Plum Brook Station Sandusky, OH 44870 January 23, 2012 Reply to Attn of: Q U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

Subject:

Plum Brook Reactor Facility, Licenses Nos. TR-3, Docket No. 50-30 and R-93, Docket No, 50-185, Technical Basis for Reevaluation of Structural DCGLs and Uranium Activity Fractions An Independent Confirmation Survey performed during the week of July 15, 2011, by the Oak Ridge Institute for Science and Education (ORISE) identified a potential issue regarding the calculation of gross beta DCGLs when Uranium-234 was present in the radionuclide mixture.

In a telephone conference call with NRC Staff on November 1, 2001, NASA agreed that ORISE was correct on the calculation error identified in their report dated October 31, 2011.

NASA agreed to evaluate the error and assess it's affect on all areas already surveyed under our Final Status Survey Program and to address any impacts on the conclusions stated in Final Status Survey Report Attachments previously submitted.

Technical Basis Document, PBRF-TBD- 11-002, "Re-evaluation of Structure DCGLs and Uranium Activity Fractions", Revision 0, dated January 4, 2012, is enclosed for your information. It addresses the issue with erroneous surrogate DCGL calculation, the impact of the presence of Uranium-234 in the radionuclide mixture, and the impact of the error on our conclusions documented in previous submittals.

Should you have any questions or need additional information, please contact me a NASA Plum Brook Station, 6100 Columbus Avenue, Sandusky, Ohio 44870, or by telephone at (419) 621-3242.

C.

Ar Kolb NASA Decommissioning Program Manager

~&A6

Enclosures

1. Technical Basis Document PBRF-TBD- 11-002, "Re-evaluation of Structure DCGLs and Uranium Activity Fractions", Revision 0, dated January 4, 2012.

cc:

USNRC/C. J. Glenn (FSME)

USNRC/J. Webb (FSME)

USNRC/J. Tapp RIII/DNMS/DB ODH/M. J. Rubadue bcc:

Q/Official File

Plum Brook Reactor Facility Technical Basis Document Re-evaluation of Structure DCGLs and Uranium Activity Fractions PBRF-TBD-11-002 Revision No. 0

- -4 -

Prepared By: B. Mann COW Date: ~('dl2~

/7 Independent Technical R. Case Date:

Review:

Other Review: U(A Date:

Other Review: Date:

Cognizant Manager Approval:

W. Stoner g -- - Date:

RSO Approval: W. Stoner Date:

Formn AD-04/02 Rev 0

TBD- 11-002, Rev. 0 NASA PBRF DECOMMISSIONING PROJECT CHANGE/CANCELLATION RECORD DOCUMENT TITLE: Re- DOCUMENT NO: PBRF- REVISION NO: 0 evaluation of Structure DCGLs TBD-11-002 and Uranium Activity Fractions Revision 0: Initial issue of document.

Form AD-01/ 3 Rev I ii

TBD- 11-002, Rev. 0 LIST OF EFFECTIVE PAGES DOCUMENT NO: PBRF-TBD-11-002 REVISION NO.:

0 Page No. Revision Level Page No. Revision Level Page No. Revision Level Cover Page 0 Change/Cancella 0 tion Record LOEP 0 TOC (1 page) 0 Text 18 pages 0 Appendix A 0 (3 pages)

Appendix B 0 (4 pages)

Appendix C 0 (2 pages) 4 4 4 I 4 4 4 4 I 4 9 4 4 I 4

  • 4 4 I 4
  • 4 4 I 4 Form AD-01/ 5 Rev 2 iii

TBD- 11-002, Rev. 0 TABLE OF CONTENTS E xecutive Summ ary .................................................................................................................... 1 1.0 Introduction ........................................................................................................ . . . .. 2 2.0 B ackground ............................................................................................................. 3 2.1 D C G L D evelopm ent ................................................................................................. 3 2.2 Radionuclide Mixtures and Activity Fractions ........................................................ 6 3.0 R eferences ............................................................................................................ .... 8 4 .0 An aly sis ............................................................................................................................ 9 4.1 Calculation of D CG Ls .............................................................................................. 9 4.2 Review of Uranium Activity Fractions ................................................................. 11 4.3 Revised Gross Activity DCGLs ............................................................................. 15 5 .0 C onclu sio n s .................................................................................................................... 17 6 .0 Ap p en d ices ..................................................................................................................... 18 Appendix A - Source Material and SNM at PBRF ..................................................................

Appendix B - U ranium Prim er .................................................................................................

Appendix C - Revised DCGL Calculations .............................................................................

LIST OF TABLES Table 1, Single Radionuclide Structure DCGLs from the FSS Plan .............................. 3 Table 2, Radionuclide Activity Fractions and DCGLs from TBD-07-001 Table 5-3 ........ 5 Table 3, Sample Basis for Activity Fractions in TBD-07-001 Table 5-3 ....................... 6 Table 4, Areas with Uranium in the Nuclide Mixtures Established in TBD-07-001 ....... 11 Table 5, Sample Uranium Analysis Results ................................................................. 13 Table 6, Uranium Background Core Sample Results ................................................... 14 Table 7, Revised Radionuclide Activity Fractions ...................................................... 15 Table 8, Revised PBRF Structure Gross Beta Activity DCGLs ................................... 16 Table B-1 Uranium Mass and Activity Fractions ............................................ B-3 Table B-2 Uranium Signatures ................................................................. B-3 Table B-3 Background Uranium Sample Results ............................................. B-4 LIST OF FIGURES Figure B-1, Principal Uranium Isotopes .................................................................... B-i Figure 2, Uranium Series Decay Chain .......................................................................... B-2 iv

TBD- 11-002 Page 1 of 18, Rev. 0 Executive Summary Concurrent with an NRC inspection at the Plum Brook Reactor Facility (PBRF)

Decommissioning Project in July 2011, radiological surveys and records review were performed by the NRC independent verification contractor, the Oak Ridge Institute for Science and Education (ORISE). The ORISE review included a review of gross beta activity derived concentration guideline (DCGL) values used by the PBRF to evaluate final status survey (FSS) measurements for compliance with the 25 mrem/y release criterion. The gross beta activity DCGL values and the radionuclide mixtures used to calculate them are published in a PBRF Technical Basis Document (TBD), PBRF-TBD-07-001.

The ORISE report, issued in October 2011, identified an error in the gross beta activity DCGL used for the -15 ft. elevation (Area 20) of the Reactor Building, 35,296 dpm/100-cm 2 . The ORISE report determined that this value did not correctly account for the use of beta surface activity measurements in areas such as the Reactor Building -15 ft. elevation where the radionuclide mixture reported in TBD-07-001 included alpha emitting U-234. According to the ORISE report, the correct DCGL value for this area is 17,084 dpm/l 00-cm 2.

In subsequent discussions with the NRC, it was agreed that NASA would re-evaluate the method used to calculate DCGLs, with particular attention given to areas where uranium was included in the radionuclide mixture. This evaluation would also include a review of the basis for determining that uranium was present in the radionuclide mixtures. As a result of this re-evaluation it was confirmed that the DCGLs published in TBD-07-001 for areas where uranium was included in the radionuclide mixture were indeed incorrect and they are corrected. The concrete core sample results used to establish radionuclide mixtures in TBD-07-001 were found not to be representative of residual contamination from enriched uranium, for which the activity is predominately U-234. The core sample results are consistent with natural uranium where U-234 and U-238 activities are equal and are at levels indistinguishable from the natural uranium in concrete. Thus, the radionuclide mixtures used to calculate DCGLs for the PBRF areas are revised by removing uranium (U-234 and U-235) from the mixture in all areas except the New Fuel Storage Vault (where the activity fractions are based on smear sample results and are indicative of enriched uranium).

The gross beta activity DCGLs for all 21 areas in the PBRF structures were recalculated using the revised radionuclide mixtures and the corrected method of calculating DCGLs. The changes in DCGL values which result are minor, except for the New Fuel Vault (a decrease from 30,831 to 11, 475 dpm/100-cm 2 , or -62.8%) and the Reactor Building -15 ft. elevation, Area 20 (an increase from 35,296 to 40,500 dpm/100-cm2 , or 14.7%). Note that the latter DCGL is different from the value calculated by ORISE (17,084 dpm/I00-cm 2) due to removal of U-234 from the mixture. The DCGL for the two areas where the "default" radionuclide mixture is used is also changed (from 27,166 to 23,146 dpmr/100-cm 2 , a decrease of 14.8%).

TBD- 11-002 Page 2 of 18, Rev. 0 1.0 Introduction An independent verification survey of several buildings and land areas undergoing final status survey at the NASA Plum Brook Reactor Facility was conducted in July 2011. The survey was conducted by ORISE, the independent verification contractor for the US Nuclear Regulatory Commission (NRC). The survey included total surface activity measurements (alpha plus beta) in the Reactor Building inner bioshield, Quads A through D and the -15 and -25 ft. elevations of the Reactor Building. The ORISE final report identified a potential issue regarding the manner in which the gross beta activity DCGL was determined where alpha-emitting U-234 was identified in the assigned radionuclide mixture [ORISE 2011 ].

The ORISE Report stated that the gross beta activity DCGL for the Reactor Building -15 ft.

elevation (also identified as Area 20), 35,296 dpm/100-cm 2, was not adjusted to account for the use of Cs-137 as a surrogate for hard-to-detect (HTD) radionuclides, including U-234. The ORISE report indicated that the correct DCGL for this situation is 17,084 dpmr/100-cm 2 [ORISE 2011]. The matter was discussed on a conference call with the NRC Headquarters and Region III Staff on Nov 1, 2011. It was agreed that the issue would be investigated, resolved by NASA/PBRF and the results provided to the NRC. In accordance with the PBRF QA procedure for corrective actions, a problem report was prepared for entry into the PBRF corrective action database (called the C/A-5 system) [PBRF 2011]. '

This document is prepared to address the technical issues identified in the ORISE Report in a manner that is responsive to the corrective actions identified in PBRF Problem Detail Report #

0421. Specific objectives of this report are to:

1. Review the method used in TBD-07-001 [PBRF 2007] to calculate DCGLs, and revise as necessary the DCGLs calculated for radionuclide mixtures in the PBRF structures.
2. Re-evaluate the radionuclide mixtures used in TBD-07-001 to develop DCGLs in areas identified as containing uranium. This is in light of the limited sample information used to develop the mixtures and the low activity concentration of uranium in the samples relative to the natural uranium content of concrete.

Background information is provided in Section 2.0. The method for calculating gross activity DCGLs in the PBRF FSS Plan is described. The information used to calculate DCGLs and to develop radionuclide activity fractions in TBD-07-001 is summarized. References are provided in Section 3.0. In Section 4.0, revised DCGLs are presented and radionuclide mixtures and activity fractions in uranium areas are re-evaluated. Section 5.0 presents the conclusions reached from the review and evaluations. Supporting information is provided in Appendices.

Appendix A contains a summary of special nuclear material (SNM) and source material inventories at the PBRF and a history of handling and storage of these materials in the various PBRF buildings. Appendix B provides information on uranium characteristics to aid in interpreting measurement results. Appendix C provides details of the revised DCGL calculations.

The corrective action program is directed by the PBRF Procedure, QA-03, Audits and Corrective Actions, Rev. 2, February 22, 2006.

TBD-1 1-002 Page 3 of 18, Rev. 0

2.0 Background

The methods used in TBD-07-001 to calculate DCGLs for the FSS and to establish radionuclide activity fractions are summarized in this section. Background information is provided to lay the ground work for re-calculation of DCGLs as may be necessary in view of the ORISE finding regarding the gross beta activity DCGL for the Reactor Building Area 20. Many of the concrete core characterization samples used to establish radionuclide mixtures and activity fractions contained low activity concentrations of uranium. This raises the question of whether the core sample uranium activity is due to natural background and not of PBRF origin.

2.1 DCGL Development Gross activity DCGLs used in survey designs for the FSS of PBRF structures were developed in TBD-07-001. The DCGLs were developed from radionuclide mixtures established for specified PBRF areas. A default DCGL was established for areas where insufficient sample results were available to determine radionuclide mixtures and activity fractions. Table 1 shows the single radionuclide structure DCGLs for the eight principal radionuclides established in the FSS Plan [NASA 2007].

Table 1, Single Radionuclide Structure DCGLs from the FSS Plan Structure DCGLs (dpm/l100-cm 2)

H-3 Co-60 Sr-90 1-129 Cs-137 Eu-154 U-234 U-235 9.10E+06 11,000 33,100 14,900 40,500 4,500 31,500 27,100 In TBD-07-00 1, these DCGLs and the radionuclide mixtures were used to calculate gross beta activity DCGLs for 19 areas in PBRF structures. The radionuclide activity ratios and the DCGLs are shown in Table 2. The method described in TBD-07-001 for calculating the DCGLs is obtained from the FSS Plan. The description of the method which follows is excerpted from Section 3.6 of the Plan.

"For structural surfaces, the final DCGL for FSS design and implementation will be a gross beta DCGL that represents the 25 mrem/yr unrestricted use criterion.

There are two steps required to determine the gross beta DCGL:

1. perform a surrogate calculation to account for radionuclides that cannot readily be measured by a beta-sensitive detector (e.g., plastic scintillation, gas proportional) with typical efficiency and
2. perform a gross activity DCGL calculation on the surrogate DCGL values and other beta-emitting radionuclides determined to be present in significant fractions.

TBD- 11-002 Page 4 of 18, Rev. 0 The surrogate DCGL is computed based on the distribution ratio between the hard-to-detect radionuclides and the easy-to-detect radionuclides. The surrogate DCGL is calculated using the following equation: 2 DCGLsur - [ (Equation 1)

DCGL, +DC-GL2 +DC-GL3 +..+D-CGL,,

Where: DCGLsur = Surrogate radionuclide DCGL, DCGLI = DCGL for the radionuclide to be used as the surrogate for the other radionuclides, DCGL 2, DCGL 3,... DCGL, = DCGL for each radionuclide to be represented by the surrogate and R2 .... R, = Ratio of concentration (or nuclide mixture fraction) of radionuclides 2 through n to surrogate radionuclide.

Where multiple radionuclides are present, a gross beta DCGL can be developed.

This approach enables field measurements of gross activity (in the present application, gross beta activity) rather than a determination of individual radionuclide activities for comparison to the radionuclide-specific DCGLs. The gross beta DCGL is calculated using the following equation: 3 DCGL"B=[( f] )+(Df2LE +(DIGA3)+ ..... + f, (Equation 2)

DC.GLl, tDCGL,,J Where: DCGLGB = gross beta DCGL fl, f2 , f 3, fn = activity fraction of each radionuclide DCGL., = DCGL of each radionuclide to be represented by the surrogate.

Note 1: The gross beta equation may also be used to calculate a gross alpha DCGL for application in areas where DCGL values are established for alpha emitters.

Note 2: If a surrogate radionuclide is used, the "fn" is equal to the surrogate radionuclide fraction (and the surrogate DCGL is inserted in the denominator of the term). 4 Note 3: The value of 1 in the numerator is replaced by the actual fraction of beta (or alpha) emitters if less than 100% of the mixture."

2 Surrogate DCGL equation from Section 3.6.1 of the FSS Plan.

3 Gross beta activity DCGL equation from Section 3.6.2 of the FSS Plan.

4 Parenthetical comment inserted by author.

TBD- 11-002 Page 5 of 18, Rev. 0 Table 2, Radionuclide Activity Fractions and DCGLs from TBD-07-001 Table 5-3 Bldg. (1) Location Activity Fractions DCGLGB H-3 Co-60 Sr-90 1-129 Cs-137 Eu-154 U-234 U-235 (dpm/100-cm 2)

Rx Bldg Area 2 & Lily Pad 0.9757 0.021 0.0013 0 0.002 0 0 0 11563 Rx Bldg Area 17, -25 ft. 0.882 0 0 0 0.053 0 0.065 0 37235 Rx Bldg QuadA 0 0.7499 0 0 0.2501 0 0 0 13450 Rx Bldg Quads B, C, & D 0 0.3305 0 0 0.6695 0 0 0 21566 Rx Bldg Canals E, F, G & H 0.0116 0.1169 0 0 0.8699 0 0.0016 0 31711 Rx Bldg 0 ft, & 12 ft el. 0.5405 0.053 0.1145 0.0009 0.2872 0.0039 0 0 29060 Rx Bldg -15 ft. el. (Area 20) 0 0 0 0 0.484 0 0.516 0 35296 (2)

Rx Bldg -25 ft. el. 0.0729 0.5389 0.2222 0 0.1205 0.0171 0.0242 0.0042 14600 Hot Lab All Other Areas 0 0.0058 0.1577 0 0.8347 0 0.0017 0.0001 38647 Hot Lab Hot Cells 0.1045 0.0255 0.3302 0.0003 0.53787 0.0012 0.0004 0.00003 34404 Hot Lab Hot Pipe Tunnel 0.006 0.0203 0.3444 0 0.624 0 0.0048 0.0005 35781 SEB Areas O/S CPT 0.2707 0.0965 0.0788 0.0142 0.4671 0.0012 0.0698 0.0017 27166 (3)

SEB CPT 0 1 0 0 0 0 0 0 11000 FH All Areas 0.7769 0 0 0 0.0563 0 0.1668 0 36857 WHB All Areas 0.0052 0.0016 0.026 0 0.9634 0 0.0036 0.0002 40051 PPH Room 4 0.4291 0.0956 0.0256 0.2255 0.1892 0 0.0334 0.0016 11186 PPH All other Rooms 0.5422 0.0866 0.0939 0 0.1881 0 0.0805 0.0087 26348 ROLB New Fuel Vault 0.3902 0.0076 0.0421 0.0287 0.1755 0 0.3438 0.0121 30831 ROLB All other Rooms 0.2707 0.0965 0.0788 0.0142 0.4671 0.0012 0.0698 0.0017 27166 ()

HRA Vault & pipe 0.1362 0.0522 0.0601 0 0.7346 0 0.0148 0.0021 34213 tunnel WEMS All Areas 0 0.0756 0 0 0.9244 0 0 0 33834 Table 2 Note:

1. See Table 3 Notes for identification of building abbreviations.
2. DCGL questioned by ORISE.
3. Default DCGL.

TBD- 11-002 Page 6 of 18, Rev. 0 2.2 Radionuclide Mixtures and Activity Fractions Sample analysis results and supporting documentation from characterization samples collected from PBRF structures by decommissioning contractors from 2003 through 2006 were assembled and reviewed in TBD-07-00 1. These samples were screened and a set of samples was obtained that were determined to best represent the radionuclide composition of residual contamination in the PBRF structures. Samples were eliminated which:

  • did not have sufficient activity,
  • were subjected to limited analysis (gamma spectroscopy only), or

" did not have sufficient supporting documentation.

Table 3 summarizes the sample information used to obtain radionuclide mixtures and activity fractions for calculation of the DCGLs presented in TBD-07-001 Table 5-3. As seen in Table 3, the sample set included 67 samples comprised of 32 concrete cores, 30 smears and five of other media (concrete chips, pipe debris and sludge). Most of these samples were subjected to comprehensive radionuclide analysis comprising gamma spectroscopy and radiochemical analysis for specified non-gamma emitting radionuclides including uranium (and transuranics). Areas where uranium was identified in the radionuclide mixture are noted.

Table 3, Sample Basis for Activity Fractions in TBD-07-001 Table 5-3 Type of Number Analysis Building Location of Performed Comments/Information Source (2)

Samples Samples (1)

)Area 2 & Summary in TBD-07-001, Table 5-5.

Rx Bldg (3)LAead Smears 2 10CFR61 Sample results and DCGL calculations in Lily Pad App. F. No U identified in the mix.

-Concrete Summary in TBD-07-001, Table 5-6.

Rx Bldg (3) Area 17, - I1OCFR61 Sample results and DCGL calculations in 25 ft. Cores App. D. U-234 only identified in the mix.

Concrete Summary in TBD-07-001, Table 5-7.

Rx Bldg (3) Quad A Cores 1 IOCFR61 Sample results and DCGL calculations in App. D. No U identified in the mix.

Summary in TBD-07-001, Table 5-8.

Rx Bldg (3) Quads B, Concrete 2 OCFR61 Sample results and DCGL calculations in App. D. No U identified in the mix.

E, Concrete Summary in TBD-07-001, Table 5-9.

Rx Bldg g(3) Canals F,)G & H Cores 4 IOCFR61 Sample results and DCGL calculations in

, &App. D. U-234 only identified in the mix.

(30ft&12 Summary in TBD-07-001, Table 5-10.

Rx Bldg (3) ft e&. Smears 2 IOCFR61 Sample results and DCGL calculations in App. F. No U identified in the mix.

)Concrete Summary in TBD-07-001, Table 5-11.

Rx Bldg (3) -15 ft. el. Coret 1 10CFR61 Sample results and DCGL calculations in Cores App. D. U-234 only identified.

Rx Bldg (3) -25 ft. el. Concrete 2 10CFR61 Summary in TBD-07-001, Table 5-12.

TBD- 11-002 Page 7 of 18, Rev. 0 Table 3, Sample Basis for Activity Fractions in TBD-07-001 Table 5-3 Type of Bn Number Analysis Building Location of Performed Comments/Information Source (2)

Samples Samples (1)

Cores Sample results and DCGL calculations in App. D. Both U-234 & U-235 identified.

All Other Concrete Summary in TBD-07-001, Table 5-13.

Hot Lab Areas Cores 4 IOCFR61 Sample results and DCGL calculations in App. D. Both U-234 & U-235 identified.

Summary in TBD-07-001, Table 5-14.

Hot Lab Hot Cells Smears 14 IOCFR61 Sample results and DCGL calculations in App. F. Both U-234 & U-235 identified.

Summary in TBD-07-00l, Table 5-15.

Hot Lab Hot Pipe Concrete 10CFR61 Sample results and DCGL calculations in App. D. Both U-234 & U-235 identified.

SEB (4) Areas O/S Smears 6 N/A Samples not believed to be representative.

CPT Default DCGL was assigned.

Concrete Sample results not believed to be SEB (4) CPT Coret I N/A representative. The Co-60 DCGL was Cores__assigned for conservatism. No U identified.

Concrete Summary in TBD-07-001, Table 5-18.

FH (5) All Areas 1 OCFR61 Sample results and DCGL calculations in App. D. Both U-234 & U-235 identified.

)Concrete Summary in TBD-07-001, Table 5-19.

WUB (6) All Areas Conre 3 10CFR61 Sample results and DCGL calculations in App. D. Only U-234 identified.

ppH (7) Room 4 Concrete 2 OCFR6 Summary in TBD-07-001, Table 5-20. Both Cores U-234 & U-235 identified.

PPH (7) All other Concrete 5 IOCFR61 Summary in TBD-07-001, Table 5-21. Both Rooms Cores U-234 & U-235 identified.

Summary in TBD-07-001, Table 5-23.

ROLB (8) New Fuel Smears 4 10CFR61 Sample results and DCGL calculations in Vault App. F. Both U-234 & U-235 identified.

Summary in TBD-07-001, Table 5-22.

ROLB (8) All other Smears 2 N/A Insufficient sample supporting information Rooms to determine representative mixture and DCGL. Default DCGL assigned.

Vault & Concrete chips & pipe debris. Summary in HRA (9) pipe Other 2 10CFR61 TBD-07-001, Table 5-24. Sample results in tunnel App I. Both U-234 & U-235 identified.

WEMS ('0) All Areas Other 3 Gamma Sludge samples. Summary in TBD-07-Oo, spec. Table 5-25. No U identified.

Table 3 Notes:

I. Analysis for a broad suite of radionuclides is typically referred to as "10CFR61 Analysis". The commonly used term "10CFR61 analysis" derives from the IOCFR61 regulations of the NRC, specifically 10CFR61.55, Waste Classification. This regulation lists specific radionuclides whose concentration in waste streams must be determined for waste classification purposes. These include specified activation and fission products, alpha emitting uranium and transuranic radionuclides with half-lives greater than 5 years, Pu-241 and Cm-242.

TBD- 11-002 Page 8 of 18, Rev. 0

2. When it is stated that a U isotope was identified, it means that it was included in the mixture and the activity fraction was calculated.
3. Rx Bldg - Reactor Building (Building 1111), also denoted as RB.
4. SEB - Service Equipment Building (Building 1131).
5. FH - Fan House (Building 1132).
6. WHB - Waste Handling Building (Building 1133).
7. PPH - Primary Pump House (Building 1134).
8. ROLB - Reactor Office and Laboratory Building (Building 1141).
9. HRA - Hot Retention Area (Building 1155).
10. WEMS - Water Effluent Monitoring Station/System (Building 1192).

3.0 References Abel 1997 Eric W. Abelquist and Timothy J. Vitkus, Considerationsfor DecommissioningSurvey Design and Implementation at Uranium and Thorium Sites, Radiation Protection Management, July/August 1997.

ANL 2005 Argonne National Laboratory, Human Health Fact Sheet, Uranium, www.ead.anl.gov/pub/doc/Uranium.pdf, August 2005.

NASA 1970 National Aeronautics and Space Administration, OperationsTrainingManual for the Plum Brook Reactor, Revision 5, May 1970.

NASA 2007 NASA Safety and Mission Assurance Directorate, FinalStatus Survey Planfor the Plum Brook Reactor Facility,Rev. 1, February 2007.

NCRP 1987 National Council on Radiation Protection and Measurements, Exposure of the Population in the United States and Canada from Background Radiation, NCRP Report No. 94, December 30, 1987.

ORISE 2011 Oak Ridge Institute for Science and Education, Independent Environmental Assessment and Verification Program, Final- Independent Confirmatory Survey Reportfor the Reactor Building, Hot Laboratory,PrimaryPump House, and Land Areas at the Plum Brook Reactor Facility,Sandusky, Ohio, October 2011.

Pigford 1981 T. H. Pigford, M. Benedict and H. W. Levi, Nuclear Chemical Engineering, Second Edition, McGraw-Hill, New York, 1981.

PBRF 2007 Plum Brook Reactor Facility Technical Basis Document, Adjusted Gross DCGLsfor StructuralSurfaces, PBRF-TBD-07-001, Rev. 0, June 5, 2007.

PBRF 2009 Plum Brook Reactor Facility, Memorandum to Project File, J. L. Crooks, Don Young, FinalFSS Report Background- Hot Laboratory (1112), December 10, 2009.

TBD-1 1-002 Page 9 of 18, Rev. 0 PBRF 2009a Plum Brook Reactor Facility, Memorandum to Project File, J. L. Crooks, Don Young, FSS FinalReport BackgroundInformation - ROLB, Reactor Office and LaboratoryBuilding (1141), December 2, 2009.

PBRF 2009b Plum Brook Reactor Facility, Memorandum to Project File, J. L. Crooks, Don Young, FinalFSS Report Background - Reactor Building (1111), December 10, 2009.

PBRF 2009c Plum Brook Reactor Facility, Memorandum to Project File, J. L. Crooks, Don Young, FinalFSS Report Background - Reactor Containment Vessel (1112),

December 10, 2009.

PBRF 2009d Plum Brook Reactor Facility, Memorandum to Project File, J. L. Crooks, Don Young, FinalFSS Report Background - NASA Plum brook FacilityPrimary Pump House (1134), December 8, 2009.

PBRF 2011 NASA PBRF D&D, Problem Detail Report, PotentialError in Gross Beta DCGL usedfor FSS in Reactor Building -15' elevation (Area 20), CA-5 Problem # 0421, Nov. 2, 2011.

PBRF 2011 a Plum Brook Reactor Facility, Memorandum to Project File, J. L. Crooks, Don Young, Source and SNM Inventory at PBRF,November 11, 2011.

Schleien 1987 B. Schleien, L A. Slaback Jr. and B. K. Birky, Handbook of Health Physics and Radiological Health, Third Edition, Lippincott Williams and Wilkins, Baltimore, 1998.

Tele 2011 Teledyne Brown Engineering, Inc. Reportfor Work Order # L48463, PBOSG -

Plum Brook Soils and APs, November 18, 2011.

4.0 Analysis In this section, the method for calculating gross beta activity DCGLs is reviewed in light of the error noted in the ORISE report and the method is corrected. Next, the activity fractions assigned to uranium in Table 5-3 of TBD-07-001 are re-evaluated considering uranium use at the PBRF, uranium radioactivity properties and measured background concentrations in concrete. Then the gross beta activity DCGLs for the areas listed in Table 5-3 of TBD-07-001 are re-calculated taking into account revised activity fractions and the corrected DCGL calculation method.

4.1 Calculation of DCGLs As discussed in Section 2.0, the ORISE report identified a problem with the gross beta activity DCGL for the Reactor Building -15 ft. elevation, Area 20. In this area of the

TBD- 11-002 Page 10 of 18, Rev. 0 Reactor Building, the assigned radionuclide mixture comprised only Cs-137 and U-234 with 48.4% and 51.6% of the total activity, respectively. In TBD-07-001, the calculated DCGLs did not consistently incorporate the surrogate DCGL into the gross beta activity DCGL calculation.

The calculation is corrected here. Using Equation 1 (in Section 2.1) and the activity fractions assigned in Table 5-3 of TBD-07-001, the surrogate DCGL is calculated as:

DCGLsur 1 = 17,083 dpm/100-cm 2 ,

1 0"1/0.484 40,500 31,500 Where: 0.484 = Cs- 137 activity fraction; 40,500 = Cs- 137 DCGL and 0.516 = U-234 activity fraction; 31,500 = U-234 DCGL.

The gross beta DCGL is calculated per note 3 following Equation 2, by replacing the value "1" in the numerator of Equation 2 with the activity fraction of the detectable radionuclides (in this case only Cs-137) and inserting the surrogate DCGL calculated above into the denominator as follows:

DCLBGB -0.484 0.484 0 0 17,083 dpm/100-cm 2 .

17,083 DCGLco DCGLsr In the present case, the calculation shown above is not necessary as there is only one non-zero term in the denominator; thus DCGLGB = DCGLsur. The second and third terms in the denominator are shown to note that in the general case, the quotients of activity fraction and DCGL for other detectable radionuclides are included in the calculation.

All the DCGLs listed in Table 5-3 of TBD-07-001 were re-calculated using an EXCEL template which incorporates the method described above. Significant differences were found between the re-calculated gross beta activity DCGL values and those listed in Table 5-3 of TBD-07-001 for several of the areas. The differences are due to two causes:

a. Failure to properly incorporate the surrogate DCGL into the gross beta activity DCGL calculation.
b. The DCGLs in TBD-07-001 were obtained as the average of DCGLs calculated for each characterization sample radionuclide mixture in areas where multiple sample results were available. In this approach, an accumulation of round-off and truncation errors in the many ratios of small numbers appears to have contributed to the differences noted.

TBD- 11-002 Page 11 of 18, Rev. 0 The largest differences are seen in those areas where significant uranium activity fractions were assigned in TBD-07-001. The revised DCGLs are shown in Section 4.3 below. They include the incorporation of revised activity fractions developed in the next section.

4.2 Review of Uranium Activity Fractions A review was conducted of the information used to obtain radionuclide activity fractions for calculation of DCGLs in TBD-07-001. This review was essentially a revisit of the evaluation in Section 5.3.2 of the TBD and the supporting sample information in the TBD appendices. The sample analysis results were reviewed to determine if inclusion of uranium in each of the mixtures is reasonable considering that the activity in the characterization core samples was very low. Also considered are the process history, uranium activity characteristics and uranium background concentrations in concrete.

Table 4 identifies those areas in the PBRF buildings where uranium was included in the radionuclide mixtures for calculation of DCGLs reported in TBD-07-001. This table is derived from Table 3 in this report.

Table 4, Areas with Uranium in the Nuclide Mixtures Established in TBD-07-001 Number U Activity Fractions Location of Type of Uranium (%) (1)(2)

Building amples S amples in Mixture U-234 U-235 Rx Bldg Area 17, -25 ft. 1 Cores Yes 6.5 0 Rx Bldg Canals E, F, G & H 4 Cores Yes 0.16 0 Rx Bldg -15 ft. el. 1 Cores Yes 51.6 0 Rx Bldg -25 ft. el. 2 Cores Yes 2.42 0.42 Hot Lab All Other Areas 4 Cores Yes 0.17 0.01 Hot Lab Hot Cells 14 Smears Yes 0.040 0.003 Hot Lab Hot Pipe Tunnel 5 Cores Yes 0.48 0.05 FH All Areas I Cores Yes 16.68 0 WHB All Areas 3 Cores Yes 0.36 0.02 PPH Room 4 2 Cores Yes 3.34 0.16 PPH All other Rooms 5 Cores Yes 8.05 0.87 ROLB New Fuel Vault 4 Smears Yes 34.38 1.21 HRA Vault & pipe Tunnel 2 Other Yes 1.48 0.21 Table 4 Notes:

1. These are the uranium activity fractions assigned in TBD-07-001, Table 5-3.
2. The SEB Areas O/S the CPT and ROLB, All Other Rooms, are not included in the table.

These areas were assigned the default mixture. The activity fraction of each radionuclide in the default mixture is a global average of the activity fractions of each radionuclide in the characterization samples from the 19 areas identified in Table 5-3 of TBD-07-001.

TBD- 11-002 Page 12 of 18, Rev. 0 In view of the history of uranium storage, use and process waste handling in the PBRF buildings described in Appendix A, uranium could have been present (before remediation) in the areas listed in Table 4. During PBRF operations, uranium materials were present in significant quantities in the Reactor Building Quads and Canals, the PPH, the Hot Lab and the ROLB New Fuel Vault and Radiochemistry Laboratories. Waste streams containing uranium were present in the RB -15 ft. and -25 ft., the Fan House, WHB and HRA. Considering that most of the uranium in the PBRF was enriched, residual uranium contamination in PBRF structures would be expected to be characteristic of enriched uranium. As shown in Appendix B, the activity of enriched uranium activity is mostly due to U-234. The U-234 activity ranges from 85% to over 95% of total uranium activity, depending on the enrichment. The U-238 activity fraction is about 12% (in 4% enriched U) and less than 1% (in 93% enriched U). Thus, the activity composition of enriched uranium is distinctly different from natural uranium where the U-234 and U-238 activity fractions are equal.

In 10 of the 13 areas listed in Table 4, the uranium activity fractions in TBD-07-001, Table 5-3 were established using concrete core sample results. In one area, the HRA, the samples consisted of concrete chips and sludge. The uranium activity characteristics of individual samples used to obtain activity fractions in each of the areas (exclusive of the areas where smear samples were collected) are shown in Table 5. The information in Table 5 is obtained from vendor laboratory reports; only samples are included for which uranium activity was reported.

Table 5 includes U-238 and U-234 results (pCi/g) for 26 samples representing the 12 areas (a duplicate analysis result is included for the PPH Rm 8 sample). The table also lists the two-sigma analytical uncertainties for each result, the U-234/U-238 activity ratio and the ratio uncertainty. The activity ratios all are strongly indicative of natural uranium,

i. e., a U-234/U238 ratio of one.

TBD-1 1-002 Page 13 of 18, Rev. 0 Table 5, Sample Uranium Analysis Results 3U-238 U-234 Location Sample ID Data Source U-238 Uncert. U-234 Uncert. 234/238 234/238 (pCi/ (pCi/g) (2) (pCi/g) (pCi/g) (21 Act. Ratio Uncert. (3)

CV, -25 ft. Area 17 Core Loc # 9 STL 5/14/04A 7.OOE-01 2.40E-01 7.OOE-01 2.40E-01 1.00 0.48 Rx Bldg Canal E Loc # 6 STL 5/14/04A 8.80E-01 2.50E-01 7.50E-01 2.30E-01 0.85 0.36 Rx Bldg -15 Area 20 Loc # 7 STL 5/14/04 7.80E-01 2.60E-01 7.20E-01 2.40E-01 0.92 0.44 Rx Bldg -25 Area 22 Loc # 5 STL 5/14/04 6.20E-01 2.20E-01 6.40E-01 2.20E-01 1.03 0.51 Hot Lab 0 ft. Loc # 11 STL 5/14/04A 4.40E-01 1.70E-01 3.60E-01 1.50E-01 0.82 0.46 Hot Lab 0 ft. Loc # 12 STL 5/14/04A 8.50E-01 2.60E-01 1.04E+00 3.OOE-01 1.22 0.51 Hot Lab 0 ft. Loc # 13 STL 5/14/04A 8.20E-01 2.70E-01 9.60E-01 3.OOE-01 1.17 0.53 Hot Lab 0 ft. Loc # 14 STL 5/14/04A 6.40E-01 2.20E-01 8.1OE-01 2.60E-01 1.27 0.60 Hot Lab HPT Loc # 15 STL 5/14/04A 9.10E-01 2.80E-01 1.28E+00 3.60E-01 1.41 0.59 Hot Lab HPT Loc # 16 STL 5/14/04A 9.1OE-01 2.70E-01 9.1OE-01 2.80E-01 1.00 0.43 Hot Lab HPT Loc # SR 24-8 STL 9/7/06 5.80E-01 1.70E-01 6.30E-01 1.80E-01 1.09 0.44 Hot Lab HPT Loc # SR 24-18 STL 9/7/06 7.OOE-01 1.90E-01 8.OOE-01 2.1OE-01 1.14 0.43 Fan House -12 ft. Loc # 17 STL 5/14/04A 1.02E+00 3.1OE-01 1.14E+00 3.40E-01 1.12 0.48 WHB -13 ft. Loc # 10 STL 5/14/04A 5.OOE-01 1.90E-01 5.50E-01 2.1OE-01 1.10 0.59 WHB -14.5 Evap. Pit Loc SR 24-2 STL 9/7/06 6.30E-01 1.83E-01 7.00E-01 1.97E-01 1.11 0.45 PPH 0 ft. Rm 4 Loc SR 24-12 STL 9/7/06 7.70E-01 2.1OE-01 7.OOE-01 2.OOE-01 0.91 0.36 PPH 0 ft. Rm 4 Loc # SR 24-16 STL 9/7/06 9.10E-01 1.80E-01 9.40E-01 1.80E-01 1.03 0.28 ROLB Fuel Vault Loc # 21 STL 5/14/04 6.70E-01 2.30E-01 6.OOE-01 2.1OE-01 0.90 0.44 PPH 0 ft. Rm 4 SR-24-16 STL 9/7/06 9.1OE-01 1.80E-01 9.40E-01 1.80E-01 1.03 0.28 PPH 0 ft. Rm 4 SR-24-15 R4 SPI-SLI STL 5/4/07 9.70E-01 2.50E-07 9.80E-01 2.50E-01 1.01 0.26 PPH 0 ft. Rm 6 SR-24-12 R6-SP1-SL1 STL 5/4/07 9.70E-01 2.40E-01 .OOE+00 2.50E-01 1.03 0.36 PPH 0 ft. Rm 8 SR-24-11 R8-SPI-SL4 STL 5/4/07 1.06E+00 2.80E-01 8.30E-01 2.30E-01 0.78 0.30 PPH 0 ft. Rm 8 SR-24-11 R8-SP1-SL4 STL 5/4/07 DUP 6.60E-01 1.90E-01 8.50E-01 2.30E-01 1.29 0.51 PPH 0 ft. Rm 5 SR-24-13 R5-SP1-SL1 STL 5/4/07 8.50E-01 2.50E-01 7.30E-01 2.30E-01 0.86 0.37 PPH 0 ft. Rm 3 SR-24-14 R3-SP1-SLl STL 5/4/07 1.OOE+00 2.50E-01 8.OOE-01 2.20E-01 0.80 0.30 HRA Vault & Pipe Tunnel Concrete Chips Eberline 9/13/05 5.33E-01 2.70E-01 8.26E-01 2.71E-01 1.55 0.94 HRA Vault & Pipe Tunnel Drain Pipe Debris Eberline 9/13/05 2.14E-01 1.20E-01 3.23E-01 1.50E-01 1.51 1.10 Table 5 Notes:

1. The vendor laboratory reports are identified by the vendor name (STL is Sevem Trent Laboratories) and report date.
2. Reported as the total analytical 2-sigma uncertainty.
3. The U-234/U-238 ratio uncertainties are calculated by propagation of the sample analytical uncertainties. This underestimates the total, but unknown uncertainty, as sampling and other process errors are not accounted for.

TBD- 11-002 Page 14 of 18, Rev. 0 The question is raised whether the subject concrete core uranium concentrations are different from background. Clearly the measured uranium activities (and that of other radionuclides) in smear samples were indicative of contamination of PBRF origin; this is not questioned here. The TBD-07-001 report indicates that concrete core samples are the preferred source of information for determining composition of residual contamination in the PBRF concrete structures under the assumption that surface contamination is removed during remediation. To enable comparison of the subject PBRF core sample results to concrete background uranium concentrations, Table 6 presents results from analysis of three core samples collected from Plum Brook Station reinforced concrete structures located well away from the PBRF and constructed in the early 1960s (see Appendix B for a description of the background samples).

Table 6, Uranium Background Core Sample Results Sample Sample_

ID ID Sample Location Concentration (pCi/g) (4)

_SampleLocatio U-234 (') U-235 U-238 SR-363-1 Bldg. B-1 0.723 f--0.186 <MDA (5) 0.725 +/- 0.187 SR-363-2 Bldg B-3 0.965 +/- 0.241 <MDAD 5) 0.863 +/- 0.232 SR-363-3 C-site (Bldg 2211) 0.895 +/- 0.290 <MDA 0.928 +/- 0.296 Table 6 Notes:

1. Sample analysis results from Teledyne Brown Engineering, Inc. Nov. 18, 2011 Report for Work Order # L48463.
2. Results +/- 2-sigma analytical uncertainty.
3. U-234 MDAs ranged from 2.08 to 6.40 E-02 pCi/g.
4. U-238 MDAs ranged from 3.06 to 6.40 E-02 pCi/g.
5. U-235 MDAs ranged from 1.38 to 3.34 E-02 pCi/g.

Comparison of the results in Tables 5 and 6 leads to the conclusion that the Table 5 concrete core sample uranium concentrations are not distinguishable from background, taking the uncertainties into account. Ninety-fifth % confidence intervals for the Table 5 results clearly encompass the Table 6 background sample U-234 and U-238 concentrations.

From the information presented here, it is apparent that the uranium in the Table 5 samples is natural uranium and the concentrations are indistinguishable from uranium background levels in Plum Brook Station structure concrete. It is thus concluded that uranium in the subject samples is highly unlikely to be of PBRF origin and uranium is to be removed from the radionuclide mixtures used to develop DCGLs for all areas except the ROLB New Fuel Vault.

It is noted that in the PBRF FSS Plan, U-238 was not included in the determination of activity fractions for residual contamination in structures. It was eliminated from consideration because the activity concentrations measured were generally at levels equivalent to background and it was among a group of radionuclides eliminated from further consideration because their combined dose contribution was less than 10% of the

TBD-1 1-002 Page 15 of 18, Rev. 0 25 mrem/y dose criterion. 5 Also, U-234 and U-235 were eliminated for the same reason from the mixtures for all areas except the ROLB; thus they are removed in the present re-evaluation from the Hot Lab, Hot Cells (see Tables A-4 and A-5, in Appendix A of the FSS Plan).

4.3 Revised Gross Activity DCGLs As a result of the forgoing re-evaluation of radionuclide mixtures in the PBRF structure areas, revised mixtures and activity fractions have been developed. They are shown in Table 7.

Table 7, Revised Radionuclide Activity Fractions Bldg Location Activity Fractions H-3 Co-60 Sr-90 1-129 Cs-137 Eu-154 U-234 U-235 Rx Bldg Area 2 & Lily Pad 0.9757 0.021 0.0013 0 0.002 0 Rx Bldg Area 17, -25 ft. Revised 0.943 0 0 0 0.057 0 RxBldg Quad A 0 0.7499 0 0 0.2501 0 Rx Bldg Quads B, C, & D 0 0.3305 0 0 0.6695 0 Rx Bldg Canals E, F, G & H 0.012 0.117 0 0 0.871 0 Revised Rx Bldg 0 ft, & 12 ft el. 0.5405 0.053 0.1145 0.0009 0.2872 0.0039 Rx Bldg -15 ft. el. Revised 0 0 0 0 1.0 0 Rx Bldg -25 ft. el. Revised 0.075 0.555 0.229 0 0.124 0.018 Hot Lab All Other Areas Revised 0.000 0.006 0.158 0 0.836 0.000 Hot Lab Hot Cells Revised 0.105 0.026 0.330 0.0003 0.538 0.001 Hot Lab Hot Pipe Tunnel Revised 0.006 0.020 0.346 0 0.627 0.000 SEB Areas 0/S CPT Revised 0.265 0.178 0.078 0.013 0.465 0.0013 (default mixture)

SEB CPT 0 1 0 0 0 0 FH All Areas Revised 0.932 0 0 0 0.068 0 WHB All Areas Revised 0.005 0.002 0.026 0 0.967 0 PPH Room 4 Revised 0.445 0.099 0.027 0.234 0.196 0 PPH All other Rooms Revised 0.595 0.095 0.103 0.000 0.207 0 ROLB New Fuel Vault 0.3902 0.0076 0.0421 0.0287 0.1755 0 0.3438 0.0121 ROLB All other Rooms Revised 0.265 0.178 0.078 0.013 0.465 0.0013 (default mixture)

HRA Vault & Pipe Tunnel 0.139 0.053 0.061 0 0.747 0 Revised WEMS All Areas 0 0.0756 0 0 0.9244 0 5 In the FSS Plan, U-234 was also "deselected" from radionuclide mixtures in all areas except the ROLB.

The radionuclide distribution for the ROLB was based on characterization smear samples. See FSS Plan Section 3.0 [NASA 2007].

TBD- 11-002 Page 16 of 18, Rev. 0 The location column identifies those areas for which the activity fractions are revised.

The revised activity fractions are calculated by removing the uranium activity fractions from all areas except the New Fuel Vault and "renormalizing" the remaining nuclide activity fractions by calculating the ratio of the "old" activity fraction to the sum of the activity fractions of the remaining radionuclides. Then the sum of the "new" activity fractions for each location then totals to one. The two locations in Table 7 identified as having default radionuclide mixtures are the SEB, Areas Outside of the Cold Pipe Tunnel and the ROLB, All Other Rooms. The activity fraction for each radionuclide in the default mixture is calculated as the average of the radionuclide fractions in the other areas, exclusive of the New Fuel Vault. The default mixture (and DCGL) are also assigned in TBD-07-001, Appendix L, to PBRF building exteriors, outbuildings and other miscellaneous structures and pads.

Determination of the revised radionuclide mixtures and activity fractions allows revision of the gross beta activity DCGLs using the corrected method of calculation as outlined in Section 4.1. The results are presented in Table 8.

Table 8, Revised PBRF Structure Gross Beta Activity DCGLs Detectable TBD-07-01 Revised Location Act. Table 5-3 DCGLGB  % change Fraction DCGLGB (dpm/100-cm 2)

Rx Bldg Area 2 & Lily Pad 0.0243 11563 11544 -0.2%

Rx Bldg Area 17, -25 ft. Revised 0.0567 37235 37707 1.3%

Rx Bldg Quad A 1.0000 13450 13450 0.0%

Rx Bldg Quads B, C, & D 1.0000 21566 21470 -0.4%

Rx Bldg Canals E, F, G & H Revised 0.9884 31711 30734 -3.1%

Rx Bldg 0 ft, & 12 ft el. 0.4586 29060 28040 -3.5%

Rx Bldg -15 ft. el. Revised 1.0000 35296 40500 14.7%

Rx Bldg -25 ft. el. Revised 0.9250 14600 14382 -1.5%

Hot Lab All Other Areas Revised 1.0000 38647 38538 -0.3%

Hot Lab Hot Cells Revised 0.8952 34404 34583 0.5%

Hot Lab Hot Pipe Tunnel Revised 0.9940 35781 35747 -0.1%

SEB Areas 0/S CPT Revised SEB (deau (default mxu mixture R& DCGL)

CvLe 0.7054 27166 23146 -14.8%

SEB CPT 1.0000 11000 11000 0.0%

FH All Areas Revised 0.0676 36857 38157 3.5%

WHB All Areas Revised 0.9948 40051 40090 0.1%

PPH Room 4 Revised 0.3217 11186 10588 -5.3%

PPH All other Rooms Revised 0.4047 26348 23914 -9.2%

ROLB New Fuel Vault 0.2252 30831 11475 -62.8%

All other Rooms Revised ROLB Aul (eatmixture mtur &RevLe

& DCGL) 0.7054 27166 23146 -14.8%

TBD- 11-002 Page 17 of 18, Rev. 0 Table 8, Revised PBRF Structure Gross Beta Activity DCGLs TBD-07-001 Detectable Table 5-3 Revised Bldg Location Act. DCGLCB DCGLGB  % change Fraction Fraction___ DGG CLB %cag (dpm/100-cm 2)

HRA Vault & pipe Tunnel Revised 0.8615 34213 34267 0.2%

WEMS All Areas 1.0000 33834 33673 -0.5%

It is seen in Table 8 that the major changes in gross beta activity DCGL values from the TBD-07-001 values occur in the Reactor Building -15 ft. (14.7%) and the New Fuel Vault (-62.8%). The effect of the corrected DCGL calculation is not seen in the new value for the Reactor Building -15 ft. because the removal of uranium from the mixture leaves only Cs-137 in the mixture and the DCGL reverts to the single nuclide Cs-137 DCGL, 40,500 dpm/100-cm 2. The new DCGL value for the New Fuel Vault is entirely due to the corrected method of calculating the gross beta activity DCGL, as the mixture and activity fractions are not changed.

5.0 Conclusions The method for calculating the DCGLs presented in TBD-07-001 Table 5-3 was re-evaluated in response to an ORISE finding following their July 2011 confirmatory survey and review of PBRF FSS records. The ORISE finding was that the gross beta activity DCGL calculated for the Reactor Building -15 ft. elevation did not properly incorporate the surrogate DCGL where Cs-137 is used as the surrogate for U-234. The recalculated DCGLs are presented in Table 8. The revised DCGLs also incorporated changes in the radionuclide mixtures and activity fractions which resulted from a re-evaluation of the concrete core sample uranium analysis results used in TBD-07-001 to establish the activity fractions.

From this re-evaluation, it is concluded that:

1. Considering that most of the uranium in the PBRF was enriched uranium, the isotopic composition of characterization samples collected from "uranium areas" should be consistent with that of enriched uranium. There is no evidence of enriched uranium in concrete core samples used to establish radionuclide mixtures for determination of structure DCGLs. The core sample results all are indicative of natural uranium at levels consistent with concrete uranium background concentrations.
2. The exception to this is the smear samples collected from the ROLB New Fuel Storage Vault. The U-235 to U-234 activity ratio calculated from these sample results is 0.0349 (3.49%); this is consistent with enriched uranium: a U-235/U-234 activity ratio of 3.5%.

TBD- 11-002 Page 18 of 18, Rev. 0 6.0 Appendices Appendix A - Source Material and SNM at PBRF Appendix B - Uranium Primer Appendix C - Revised DCGL Calculations

TBD- 11-002, Appendix A Page 1 of 3, Rev. 0 Appendix A -Source Material and SNM at PBRF Summary During the operational history of the PBRF, from 1961 through 1973, a wide variety of source and special nuclear materials (SNM) were handled and stored at the site. Areas of the PBRF where these materials were stored and handled could be expected to have radionuclide contamination profiles different from those in the balance of plant (BOP).

These materials included uranium in several forms and other alpha-emitting radionuclides. A review was conducted of PBRF radioactive material inventory and transfer records to identify quantities of source and special nuclear materials on the site at the time of permanent shutdown of the facility in January 1973 [PBRF 201 la]. The principal source material and SNM are identified and quantities summarized:

  • New fuel elements (93% enriched in U-235) stored in New Fuel Vault in ROLB.
  • Spent fuel elements - in Canal G storage racks, 60 MW Test Reactor and MUR cores (328 elements).

0 Neutron monitoring fission chambers (encapsulated U-235) - 16 items including three different fission chamber models.

0 Uranium metal foils - 1 mil thick sheets (enriched in U-235).

  • 100 milligrams of U-233 in uranyl nitrate solution.

0 Ten U0 2 source material experimental pellets.

  • Several Pu-239 sources (in encapsulated Pu-Be startup sources).
  • Uranium fuel pellets, foils and pins; numerous items of various enrichments (from 5 to 98% - most were highly enriched) for experimental or analytical use.
  • Thorium-232 foils (15 g).

These materials were routinely stored and handled in the Hot Laboratory and the ROLB.

Irradiated fuel elements were stored in Canal G in the Reactor Building. Sources were also temporarily handled (and stored) in the Reactor Building and Containment Vessel (CV) experimental areas. New fuel elements were stored in the ROLB New Fuel Vault and new fuel elements were tested in a test loop located in the Primary Pump House, Room 7. Summaries of materials handled and stored in these areas follow. In addition to the discrete sources identified above, uranium and transuranics isotopes were released from leaking fuel elements to the primary cooling water.

Hot Laboratory Irradiated and non-irradiated source and special nuclear materials were processed in the Hot Laboratory. Two irradiated PBRF Reactor fuel elements (each containing 168 grams of U-235) were placed in the hot cells and the Hot Dry Storage Area to verify the integrity of the shielding walls in 1964. The results showed that a fuel element source, producing a dose rate of 106 R/hr at one foot, could be handled in any of the hot cells and the Hot Dry Storage Area without exceeding dose rate limits in the operating areas. The Hot Laboratory was then utilized for its intended purposes. In 1968, several 240 gram (U-235) irradiated fuel elements were disassembled in Hot Cell No. 1 to identify leaking fuel plates.

TBD- 11-002, Appendix A Page 2 of 3, Rev. 0 During the operating period from 1963-1973, an estimated 384 grams of U-235 were included in the large quantity of radioactive material processed through the Hot Laboratory. Source and special nuclear materials were associated with various PBRF experiment programs; the majority of the material was experimental fuel specimens.

About half was consumed in examination and about 10 per cent was lost in cutting and drilling. Of the cuttings and drillings (approximately 19 grams), at least half was vacuumed up, filtered out or processed as waste. Less than 10 grams of U-235 were calculated as lost down the drains. As the Hot Laboratory sump was cleaned several times over the operating period, only a small amount of U-235 remained at shutdown

[PBRF 2009].

Reactor Office and Laboratory Building A wide variety of source and special nuclear materials in the form of liquids, gases and solids were stored, handled in the ROLB and analyzed in the ROLB laboratories during the operations period. Typically, radioactive materials were transported from the Reactor Building, Containment Vessel, Hot Laboratory, Primary Pump House and other PBRF locations to the radiochemistry and metallurgy laboratories in the ROLB. Items such as primary reactor coolant samples, flux wires from the Plum Brook Test Reactor and the Mock-up Reactor (MUR), PBRF reactor vessel material specimens, small experiment specimens (such as irradiated space-related experiment samples, moon rocks, corn, coal, petroleum samples, etc.) were routinely carried in lead casks or other shielded containers for counting and analysis in the ROLB labs.

Radionuclides recorded on ROLB inventory sheets included Po-2 10, mixed fission products, Radium, Uranium (natural, depleted and enriched), Am-Be neutron sources and Np-237. Most of the source inventory was disposed as radioactive waste during operations (1961-73) and during the transition to "mothball" status in 1973. The remainder was transferred to other licensees, returned to the AEC, or stored on-site for potential future use [PBRF 2009a].

Reactor Building Radioactive materials in the Reactor Building were those associated with PBRF operations, tests and experiments, including irradiated highly enriched uranium fuel elements stored in Canal G. Handling of radioactive materials in the Reactor Building usually involved the use of shielding casks and underwater manipulations. Long handling tools were used to move spent nuclear fuel elements and to load and unload fuel elements and experiments in both the 60 MW Test Reactor and the MUR. These tasks included cleaning hot sumps, decontamination work and maintenance on both reactors. Many tasks required safe work permits due to the potential for contamination and radiation exposure, e.g., refueling and loading spent fuel for shipment (most of these required the use of personnel protective clothing and respiratory protection equipment). Frequent shielded transfers of primary cooling water samples were made from the PPH to the ROLB through the Reactor Building. Shielded transfers of irradiated rabbits or specimens such as flux wires were made to the ROLB laboratories through the RB from the MUR, CV or HL. Such activities did occasionally result in unintended spills of radioactively contaminated materials in RB areas [PBRF 2009b].

TBD- 11-002, Appendix A Page 3 of 3, Rev. 0 Reactor Containment Vessel Radioactive contamination in the CV was of two primary origins: 1) irradiated test specimens and associated hardware and 2) releases of airborne radioactive materials and contaminated liquids from the Reactor Tank and process systems. Most of the irradiated test specimens did not remain in the CV; they were transferred to other buildings in the PBRF, primarily the Hot Laboratory. Experiment transfers were occasionally conducted overland significantly increasing general radiation levels in the CV.

Leaking valves or contaminated water dripping from handling tools led to occasional surface contamination incidents. Experimental work led to gaseous and particulate releases into the CV which included activation products, fission products including Sr-90 and Cs-137 and U-235 [PBRF 2009c].

Primary Pump House Radioactive materials (primary cooling water, resins and other samples) were routinely transported from the PPH to the radiochemistry and metallurgy laboratories in the ROLB.

For example, primary reactor coolant samples were routinely carried from Room 8 in lead casks or other shielded containers for counting and analysis in the ROLB radiochemistry labs. This process occasionally led to minor spills. In addition, contamination occurred in various locations from primary cooling water (PCW) valve leakage, PCW main and auxiliary pump seal leakage or failure, and maintenance activities such as PCW strainer cleanout and pump replacement. The PPH was designed and operated to confine and control leaks and spills from potential sources (PCW water leakage, ventilating air, spent resins, etc.). Wastes from leaks and spills were contained and directed to hot storage facilities and systems where they were sampled, monitored and treated to ensure compliance with AEC/NRC regulations prior to release [PBRF 2009d].

New fuel elements were handled and tested in Room 7 of the PPH. The Fuel Element Test Loop (FETL) was designed to test the mechanical integrity of new fuel elements and shim rod fuel sections. This was accomplished by placing individual elements in a test section of the loop and subjecting them to the simulated thermal and hydraulic environment of the 60 MW Test Reactor. During the period of PBRF operations, hundreds of fuel elements were transported to the PPH and tested in the FETL. 6 Two pathways are identified for contamination from new fuel element handling and testing in PPH Room 7. Initially, liquid wastes generated in fuel handling and testing were collected in 55 gallon drums which were then emptied into the PPH Room 8 floor drain.

This drain was converted into a hot drain which fed to the -15 ft. Reactor Building sump.

Liquid wastes also entered the Room 7 floor drain which was also routed to the -15 ft. RB sump.

6 Approximately 10 to 11 fuel elements were replaced at each operating cycle and 152 cycles were completed during the period of PBRF operations. This does not include MIUR fuel elements which were changed infrequently.

TBD- 11-002, Appendix B Page 1 of 4, Rev. 0 Appendix B - Uranium Primer This Appendix provides information to aid in interpreting radiological survey measurements and sample analysis results from areas in the PBRF where isotopes of uranium are potentially present in residual contamination. As shown in Appendix A, a wide variety of radioactive materials containing uranium and other long-lived high-atomic number radionuclides were stored and handled at the PBRF. Information is presented on:

  • Radionuclides in irradiated fuel and
  • Uranium background concentration in concrete construction materials.

Uranium Isotopes and Decay Chain Uranium in nature consists mostly of U-238 and its decay series members and a small fraction of U-235. The principal uranium isotopes are shown in Figure B-1. The U-238 decay series is shown in Figure B-2. When uranium ore is processed for preparation of reactor fuel, weapons or other uses, the decay series daughters are removed and only the principal uranium isotopes remain. However, after processing, in-growth of the U-238 decay series members begins anew and after about 9 months, the first two members, 24 day Th-234 and 1.2 minute Pa-234m, both beta emitters, are in secular equilibrium with U-238 [Abel 1997].

Figure B-I, Principal Uranium Isotopes Summary of Uranium Isotopes (1)

[Percent in natural No. of No. of Half-Life Specific Activity Isotope uranium (wt%) Protons Neutrons (years) (Ci/g) (3)

IUranium-238 (2) [ 99.284 [ 92 r 146 14.46 billion I 3.35E-07 Uranium-235 (2) 0.711 1 92 [ 143 1704 million I 2.16E-06 Uranium-234 (2) 0.0055 1 92 1 142 1245,000 I 6.24E-03 Figure B-1 Notes:

1. Adapted from IEER FactsheetlUranium, http://www.ieer.org.
2. The percent (by weight) of the isotopes in natural uranium reported in various references varies slightly.
3. Specific activities from Handbook of Health Physics and Radiological Health [Schleien 1997].

TBD-1 1-002, Appendix B Page 2 of 4, Rev. 0 Figure B-2, Uranium Series Decay Chain URANIUM DECAY CHAIN -- Main Branch (1)

Read from left to right. Arrows indicate decay Uranium-238 ==> Thorium-234 ==> Protactinium-234m -- >

(half-life: 4.46 billion years) (half-life: 24.1 days) (half-life: 1.17 minutes) alpha decay (2) beta decay beta decay (3)

Uranium-234 ==> Thorium-230 ==> Radium-226 ==>

(half-life: 245,000 years) (half-life: 75,400 years) (half-life: 1,600 years) alpha decay (2) alpha decay (2) alpha decay Radon-222 ==> Polonium-218 ==> Lead-214 ==>

(half-life: 3.82 days) (half-life: 3.11 minutes) (half-life: 26.8 minutes) alpha decay alpha decay beta decay Bismuth-214 ==> Polonium-214 ==> [Lead-210 ==>

(half-life: 19.9 minutes) (half-life: 163 microseconds) (half-life: 22.3 years) beta decay alpha decay beta decay Bismuth-210 ==> Polonium-2 10 ==> Lead-206 (half-life: 5.01 days) a(half-life: 138 days) (stable) beta decay Ialpha decay Figure B-2 Notes:

1. From IEER FactsheetlUranium, http://www.ieer.org.
2. The half-lives of the long-lived members vary slightly as reported in other references.
3. Not shown is the 0.13% decay branch via 6.7 h Pa-234 (also a beta emitter).

Uranium Activity Fractions As shown in Figure B-i, natural uranium is comprised of over 99% U-238, with less than 1% U-235 and about 0.5% U-234. However, when considering radioactivity fractions instead of mass fractions, a distinctly different picture emerges. This is because the specific activity of U-234 is 18,600 times that of U-238 and 2,890 times that of U-235. Thus, even though the wt% of U-234 in natural uranium is only about 0.005%, the activity fraction is 48.9%. And while U-238 comprises over 99 wt% of natural uranium, it comprises only 48.9% of the activity.

Table B-1 compares mass and activity fractions for natural uranium, enriched uranium and depleted uranium. The table includes mass and activity fractions for enrichment percentages: 4%,

5% and 93%. It is noted that while the uranium inventory at the PBRF included natural, low enriched, highly enriched and depleted uranium, most was highly enriched uranium. It is seen from the table, given that the majority of uranium in the PBRF was highly enriched, the activity is mostly U-234. Only when natural or depleted uranium are the principal contaminants, would U-238 activity be equal or greater than that of U-234. In all cases, U-235 constitutes 3.4% or less of the total uranium activity.

TBD-1 1-002, Appendix B Page 3 of 4, Rev. 0 Table B-i, Uranium Mass and Activity Fractions Uranium U-234 ") U-235 (" U-238 (')

Description Weight % Activity % Weight % Activity % Weight % Activity %

Natural U '2) 0.0053 48.9 0.72 2.20 99.28 48.9 4% Enriched (3) 0.036 84.6 4.009 3.26 95.96 12.13 5% Enriched (3) 0.047 87.3 5.01 3.21 94.94 9.49 93% Enriched (3) 0.924 96.6 93.24 3.37 5.83 0.003 Depleted U 4" 0.0017 23.7 0.3 1.45 99.7 74.8 Table B-1 Notes:

1. Weight and activity fractions are calculated using the WISE Uranium Project calculators (http://www.wise-uranium.org).
2. The isotopic composition of natural uranium varies slightly depending on the origin of the uranium ore.
3. Isotopic weight (and activity) fractions in enriched uranium vary slightly depending on the uranium feedstock (natural ore or recycled uranium), the method of enrichment and other variables. See the WISE Project web site for additional details.
4. Isotopic composition and weight fractions of depleted uranium can vary significantly (within a range) depending on the original feedstock (multiple feed stocks are possible) and enrichment process parameters. See Note 3.

It is useful to show the data in Table B-1 as ratios of U-234 and U-235 to U-238 activity and U-235 to U-234 activity. This is done in Table B-2; these activity ratios are sometimes referred to as the "uranium signature" of a uranium sample or material. The origin of the uranium in a sample can usually be readily determined by examination of these activity ratios. In natural uranium the U-234 and U-238 activities are equal. Whereas in enriched uranium, the U-234 activity predominates; 7 to 9 times the U-238 activity in low-enriched uranium and over 32,000 times in highly enriched uranium. Only in depleted uranium is the U-234 activity significantly less than the U-238 activity.

Table B-2, Uranium Signatures Uranium U-Isotopic Activity Ratios Description 234/238 235/238 235/234 Natural U 1.00 0.04 0.045 4% Enriched 6.97 0.27 0.039 5% Enriched 9.20 0.34 0.037 93% Enriched 32200 1123 0.035 Depleted U 0.32 0.02 0.061

TBD- 11-002, Appendix B Page 4 of 4, Rev. 0 Radionuclides in Irradiated Fuel Alpha emitting radionuclides in irradiated fuel at the PBRF are produced by neutron capture reactions in U-238 and to a lesser extent in U-235 contained in the fuel. Even though irradiation times for a typical operating cycle were relatively short, typically about two weeks, transuranic radionuclides were produced. While information on assay of transuranics in irradiated PBRF 60MW Test Reactor fuel is not available, information in the open literature indicates that in addition to the original uranium isotopes in the fuel, transuranic activity 30 years after shutdown includes Np-237, Pu-238, Pu-239, Pu-240 and Pu-242 with lesser amounts of Am-241 and Cm-242. Uranium-236 is also present, with activity comparable to U-238 [Pigford 1981].

Natural Uranium in Concrete It is well known that natural uranium is a constituent of concrete, where the U-238 daughters, and K-40, contribute most of the background counts to beta detectors commonly used for FSS surface activity measurements. To provide information for comparison of uranium analysis results from concrete cores collected in the PBRF, concrete core samples were recently collected from three Plum Brook Station facilities. The facilities selected were located on the Plum Brook Station, but well away from the PBRF and were constructed in approximately the same time frame as the PBRF (late 1950's through the 1960's). The core samples were sent to a qualified vendor laboratory for analysis. The analysis request was for gamma spectroscopy and uranium isotopic: U-234, 235 and 238. The results are presented in Table B-3 [Tele 2011]. From the table it is seen that the measured Plum Brook Station concrete uranium background activity is constituted of U-234 with average concentration of 0.86 +/- 0.26 pCi/g and U-238 with average concentration of 0.84 +/- 0.20 pCi/g (two standard deviations) and U-235 with concentration <

0.03 pCi/g. As shown in Tables B-1 and B-2, the U-234 and U-238 activity concentrations in natural uranium are equal; this is confirmed by the sample results shown in Table B-3. The U-235 concentration in natural uranium is 2.2 % of the total uranium activity or 4.5 % of the U-234 or U-238 activity concentration. This is equivalent to about 0.038 pCi/g in the concrete background samples. This is approximately equal to the laboratory analysis method detection limit reported for these samples.

Table B-3, Background Uranium Sample Results Concentration (pCi/g) (1) (2)

Sample ID Sample Location U-234 U-235 U-238 SR-363-1 Bldg. B-1 0.723 +/- 0.186 <MDA (5) 0.725 +/- 0.187 SR-363-2 Bldg B-3 0.965 +/- 0.241 <MDA 5 ) 0.863 +/- 0.232 SR-363-3 C-site (Bldg 2211) 0.895 +/- 0.290 <MDA 0.928 +/- 0.296 Table B-3 Notes:

1. Sample analysis results from Teledyne Brown Engineering, Inc. Nov. 18, 2011 Report for Work Order # L48463.
2. Results +/- 2-sigma analytical uncertainty.
3. U-234 MDAs ranged from 2.08 to 6.40 E-02 pCi/g.
4. U-238 MDAs ranged from 3.06 to 6.40 E-02 pCi/g.
5. U-235 MDAs ranged from 1.38 to 3.34 E-02 pCi/g.

TBD-1 1-002, Appendix C Page 1 of 2, Rev. 0 Appendix C - DCGL Calculation Template This appendix contains an image of the EXCEL template used to calculate gross beta activity DCGLs. It uses the method described in Section 2.0 of the body of this report. The data shown in the template range C8:J28 are the revised radionuclide activity fractions shown in Table 7 of this report. The "new" default activity fractions are shown in Row 19 (C19:H19) and Row 26 (C26:H26). They are calculated in this template as the average of the individual activity fractions assigned to all the other areas, excluding the ROLB New Fuel Vault (see the example cell formula in C 19). The original gross beta activity DCGLs from TBD-07-001, Table 5-3 are shown in Column M (M8:M28). The Column N cells N8:N28 contain the EXCEL formula for calculating the surrogate DCGL, wherein Cs-137 is used as the surrogate for H-3, 1-19, U-234 and U-235. This is the EXCEL formula for Equation 1 in Section 2.0. An example formula is shown for cell N8. The Column 0 cells 08:028 contain the EXCEL formula for calculating the gross beta activity DCGL. This is the EXCEL formula for Equation 2 in Section 2.0. An example formula is shown for cell 08. The cell formulas in Column P (P8:P28) calculate the difference

(% change) between the revised gross beta DCGLs and the original TBD-07-00 1, Table 5-3 values. An example cell formula is shown for cell P8.

TBD- 11-002, Appendix C Page 2 of 2, Rev. 0 A B C D E F 3 H I J K L M N P Smn Detectable

'table 5-3 ReLised IRevised i

Actvitv Fractions 6 Bldg Location Check Act. Fractioc DMlLG3 DCGL , DCGLm  % chmage 7 H-3 Co-60 Sr-90 2 1-129 Cs-137 Eu-154 U-234 U-235 (dtm/100-cm )

8 lRxBldg Area2&LlyPad 0.9757 0.021 0.0313 0 0.002 0 1.0)0 0.0243 11563 12771 11544 -42Y 9 IRx Bldg Area 17, -25 ft. 3.eiised 0-943 0 0 0 0.057 0 1.30 0.0567 37235 37707 37707 1.3%

10 IRx Bldg QuadA 0 3.7499 0 0 0-2501 0 1.30 1.0000 13450 43500 13450 0-0%

11jRx BKlg Qads B,C, & D 0 03.3305 0 0 0.6695 0 1.30 1.0000 21566 43500 21470 -0.4o 12jRx Blg CanahkEF, G & H Revsed 0.012 0.117 0 0 0-871 0 1.30 0.9884 31711 40498 30734 -3.13r 13 IRxBldg 0Of& 12 ft el. 0.5405 0.053 0.1145 0.0009 02872 0.1039 1.30 0-45E6 29060 39827 28040 -3.5%

14 RI Bldg -15 ft. el Revised 0 0 0 0 1.000 0 1.00 1.0000 35296 43500 40500 14.7%/o

.15I[RxBkg -25 ft. el Revised 0-075 0.555 0.229 0 0.124 0.018 1.,30 0.9250 14600 40391 14382 -1.5l 1e6Hot Lab A COwrAreasRevised 0 0.006 0.158 0 0.836 0 1.,30 1.0000 38647 43500 38538 33/o lIHot Lab Hot CellsRevised 0.135 0.026 0.330 0.0003 0.538 0.301 M1.30 0.8952 34404 4,3404 34583 0.5%

18lHotLab HotlfpeTumnelRevised 0.036 0.020 0.346 0 0.627 0 1.30 09940 35781 4,3498 35747 -0.11/0 19 SEB Ares OIS CPT Revised, Default 0.265 0.178 0-079 0.013 0.465 0.0013 1.30 0.7218 27166 37542 23146 -144%

2OISEB CPT 0 1 0 0 0D1.00 0 1.0LO 11000 11000 11000 0.0%

21 FH At Areas Revised 0.932 0 0 0 0.068 0 M1.0 0.0676 36857 38157 38157 3.5%

22 WHB Al Areas Revised 0.035 0.002 0.026 0 0.967 0 1.00 0.9948 40051 40499 40090 0.1%

21 P1-I Roam 4 Revised 0.445 0.099 0.027 0234 0.196 0 1.00 03217 11186 9530 10588 -5.3%

24 IPI-I Al other Roams Revised 0.595 0.095 0.103 0 01207 0 1.00 0.4047 26348 39987 23914 2'/9 25 ROLB New Fud Vault 0.3902 3.0076 0.0421 0.0287 0.175! 0 0.3438 0.0121 1.0 0.22!2 30831 9936 11475 -621%

26 ROLB Al other Rooms Revised, Default 0-2.55 0.178 0.078 0.013 0.465 0.1013 1.30 0.7218 27166 37542 23146 -4.A%

271HRA Vault & pipe tum Revised 0.139 0.053 0.061 0 0.747 0 -1.30 0.8615 34213 4-3467 34267 0.2%

28 1W*a Al Areas 0 3.0756 0 0 0.9244 0 1.,30 1.0000 33834 43500 33673 -0.51/.

29 30 Cell Formuhs 31 ICeft Formlad Comment 32 IC19 =AVERAGE(CI,C9,C10,C1 1,C12,C13,C14,C15,C16,CI7,C18C20,C21,C22,C23,C24,C2 CaL-uates activity fractions for default radionuchlde mixture.

33 IL8 =(DS-E8+G8-HS)SUM(CMS) Detectable activity faction; sum of Co-60, Sr-90, Cs-137 & Eu-154 - sim of all activity factions 34 INS =U((/$G$4)+((CS/G8)$C4)+((FS/GS)I$-'4)-t((IS/G)ti$I$4fr((J8/G8)4J$4)) Surrogate DCGL calculaticn; Equation 1 i, Section 2-1 of ths report 35108 =LS/((G8IN)*If8/$DS4)-(ES/$E$4r-(H!8/$H$4)) Gross activity DCGL calculation Equatio 2 ia Section 2.1 of this report 36a In =(D8-M ".MI CaLulates % iffference between revised gross activity DCGL mad T3D`07-001 vahle.

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