ML16293A181
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{{#Wiki_filter:Reference 10 (Part 2 of 3) - WNYNSC Off-Site Radiation Investigation, Volume D- Draft Technical Report (D&M, 1995)
Reference 10 - WNYNSC Off-Site Radiation Investigation, Volume II New :York State Energy Research and Deveiopment Authority We.sler~ -~e\y_Jor:k.Nµcl~ar Ser.vi~~ *eeQie_r Off.;Site :I{adtatfon Investigation Vo1um,e n: -ilr~i- Technical ~~port One Blue l!ill Plaza, Suite 530, _Pe&rl Rive~. NY 10965
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- Ii WES'tERN . NEw**yo~. NUC*LEAR.~Sl~RWC.E:Q$N'rn~;
.:OFF~SITE RAD!&TION INV~ESTIGATION
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n~~~ ffe: )..forjre. One Blue Hill Plaz~ *Sfilte.530
~yarl Rive~, NY JQ965 L.ru:ry W; I,,µc~¢tt. ¢Ill>
Pr6j¢ct.'Manager NYSERDA
- P,.o}e~l Uanagef:. Marthi.t Willett 200~'"wY-f{WM~92 TaskOrder D&M~92~3 Nqte: The 'WN'YNsc:off'~.Sjte Radiatioo Inyestigatiort -
*cfoicu5sed *iTJ this *report:is fully.described iri ciuee seP,arate voiumes
.! Volume I: -Draft SumT11(1.ry Repott;Apnl 1995
- VoI11.me n,: .[)raft Techiucal R,eport, _Apfil J~5
- Voluipe ID: 'fe,d111.ical Data i\nn~ April 1995
TABLE OF CONTENTS
1.0 INTRODUCTION
, . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . . . . . 1-J, 1.1 OVERVIEW ANP OE.GANIZATION .OF THE REPORT . . . . . . . . . . 1-1 1.2 RADIOACTIVITY AND RADIATION . . . . . . , . . . . . . . . ~* .. , , . 1-2 1.2.1 Radiation Dose . . . . . . . . . , . . . . . . . . . . . . . . . . , ..... 1-2 1.2.2 Units Of Measurement . . . . . . . . . . * . . . . . ; . . . . . . . . . . L-~
i.2.3 Sources of Radiation . . . . . : . . . . . . *. . . . . . . . . . . . . . . . 1-4 1.2.4 Health Effects of .Low-Level Radiation . . . . . . . . . . . . . . . . . 1--5 1.3 APPLICABLE REGULAUONS AND REGULATORY GUIDANCE ... 1-6 1.3.l National Council*on Radiation Protection and Measurements . *... 1-7 1.3.2 U.S. Nuclear Regulatory Commission . . . . . . . . . . .* . . . . . . . 1-7 1.3.3 U.S. Environmental Protection Agency . . . * . . . . . . . . . . . . . 1-8 1.3.4 U.S. Department ofEnergy . . . . . . . . . . . . . . . . * . . . . . . . . 1-8 1.3.5 New York State Department of Environmental Conservation . . . . 1-8 1.3.6 Initial Dose Rate vs. Accumulated Dqse . ; . . . . . . . . . . , . *. . 1-9 2;0 DESCRIPTiON OF THE STUPY AREA * * . * . . . * . . * . . . * . . , . . . . . . 2-1 2.1 LOCATION AND DESCRIPTION * . . . . . . . . . . . . . . . * , . , . . . . 2-1 2.. 1.. l Regional Overview . , . . . . . . . . . , . . . . . , . . . . . . . . . . , 2-'1 2.1.2 wNYNSC Off.,Site Radiation Investigation - Study Area . . . . . . . . . . . . . . . ~ . . . . . . . . . . . . . . . . . . 2-3 2.2 NUCLEAR OPERATIONS IMPACTING THE OFF-SITE INVESTJ:GATION STUDY AREA * . . . . . * * . .._. . . * . . 2-~ 2.3 PREVIOUS RADIOLOGICAL EVALUATIONS AND STUDIES . . . . . :iA 2.3. l Early Studies ... , . . . . . . . . . . . . . . . . . . . . * . . . . . . . . 2-4 2.3.2 WVDP Environmental Characterization Report . . . . * . . , , ... 2-7 2.3.3 Aerial Survey of 1984 . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10 2.3 .4 Summary . . . . . . . . . . . . * . . . . , . . . . , . . . .. -. . . . . . . 2:-13 3,0 PHASE I PROGRAM: COA.RSE GRID RADIOLOGICAL CHARCTERIZATION3-l J.1 OVERVIEW OF THE COARSE GRID SURVEY . . . . . . . . . . . . . . . 3.-1 3.1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . _. .- -. .. 3-1 3.1.2 Survey Components . . . . . . . . . . . . . . . . . . . . . * . . . . . . . 3-1 3.1.3 Gdd Layout . . . . . . . . , . : . . . . . . . . . . , . . . . . . . . . . . 3-2 3.1.4 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . : .. 3-9
TABLE OF CONTENTS (Continued} 3.2 METHODS AND RESULTS .. , ...... ; . . . . . . . . . . . . . . . . . . . . . 3-12 3.2.1 Gamma Radhi_tion Exposure Rate (HPJC) Survey . . . . . . . . . . 3:-12 3.2.2 Tissue Equivalent Dose Rate * (microRem/hour) SurV'ey ........*.*.*.........* *.
- 3.::16 3.2.3 Radioactivity in Soil Survey *..*..... " * . . . . . . . * . . * . 3-19 3.2.4 Suivey Data Correlations . . . . . . . . . . . . . . . . . . . . . . . . 3-23
3.3 CONCLUSION
S* , . . . . . . . . . . . . 1. * * , * * * * * * * * * * * * * * * *
- 3-27 4.0 PHASE II PROGRAM: FINE GRID RADIOLOGICAL CHARACTERIZATION 4-1 4.1 OVERVIEW * * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
*4.1. l Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . 4. . *1 4.1.2 Survey Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 4.1.'3 Description of the Study Area .. , . . . . . . . . . . . . . . . . . . . 4-2 4.1.4 Instrumentation . . . . * * . . . . . . . . . . . . . . . . . . .. . . . . .
- 4-9
- 4. L5 Data Validation Requirements . . . . . . . . . , . . . . . . . . * , . . 4-ll 4.2 EVALUATION OF RADIOACTIViTY VARiATION IN SOIL ..... 4-11 4.2.1 Purpose ........ ~ .. ! ~ * :* * * * ~ * ~ * * . * * * * ** * * . * . . . . . . 4... 11 4.2.2 Locations . . . . . . . . . . . . . . . . , ......*.......... 4:-li
- 4.2~3 Methods .... *. . . . . . . . . * . . . . . * . . . . . * . . . . . . . . . . 4-,13 4.2.4 Data' Quality Assurance . . . . . . . . * . , . . . . . . . . . . . . . . 4-13 4.2.5 R,esults and Discussiori . . . . . . . . . . . . . . . . . : .. , . , . . . 4'-14 4.3 CORRELATION OF INSTRUMENT RESPONSE TO.SOIL RADIOACTiVITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19 4.3.1 Purpose ...* . . . . . . :* .... , .. ~ .. , . * . . . . . . . . . . . . 4-19 4.3.2 Methods . . . . . * . . . . .......... . . . . . . . . . . . . . . . 4.. 19 4.3.3 Results and Di5cussio11 ~ .*...* , . : . . . . . . . . . . . . . . . . 4-21 4.3.4 Correlation Verification . .. .*.. .. . . . . . . . . . . . . . . . . 4-25 4.4 SYSTEMA11C SURFACE SURVEY FOR CS-137 ACTIVITY . , ... 4-26 4.4.1 Pqrpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-:26 4.4.2 Methods . . . . . . . . . . . . . ~ *. , . ~ * , * . . *. . . . . . . . . . 4-26 4.4.3 Data Quality . . . . . . . . . . . . . . . . . . . . : . . . . . . . . . . . 4-27 4.4.4 Results and Diseussion . *. . . . . . . . . . . . . . . . . . . . . . . . . 4-28
TABLE OF CONTENTS (Continued) 4.5 WALKOVER SURF ACJ; SCANNING 4-32 4.5.l Purpose .... _. . . . . . . . . . . . . . . . . . . . . -. . . . . . . . . . 4-32 4.5 .2 Method~ . * . . . . . . . . * * ~ . . . . . . , . . . . . . . . . . . . . . . 4-32 4.5.3 bata Quality ........................ ; . . . . . . . . . 4-33 4.5.4 Results anc;l Discu~sion . . . . . . . . . . . . . . . . . . . . . . . . . . 4-33 4.6 SYSTEMATIC DOSE RATE Si.JR.VEY . . . . . . . . . . . . . . . . . . . . 4*36 4.6.1 Purpose . . . . . . . . . . , . * . . . . . . . . . . . . . . . '. ... , . . 4-36 4.6.2 Methods . . . . . . . . , . * . * . . . . . . . . . . . . * . . . . . . . . . 4-36 4.6.3 Data Quality . . . . . * * . * * . . . . . . . . . . . . . . . . . . . * . . 4.;37 4.6.4 Result_s and Discussion ... , . . . . . . . . . . . . . . . , . . . . . . 4-37 4.7
SUMMARY
AND CONCLUSIONS . . . . . . . . . . . . . . . . . * . . . . 4-38 5.0 DOSE ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 5-1 5.1 OVERVIEW . . . . . . . . . . . , . . . . . . , . . . * . . . . . . . . . . . . . . 5-1
._5._1. l Purpose ................. .- .- ............... ~ .... 5-1 S.1.2 Organization of the Dose Assessment . . . . . . . . . . . . . . . . . . 5-1 5.2 ENYIRONMEITTAL:TRANsPORT MODELING . . . . . . . . . . . . . . 5-2 5.2.1 Environmental E.Xposure Pathways . . . . . . . . . . . . . . . , .... 5~2 5 .2.2 Modeling Environmental Transport . . . . . . . . . . . . . . . . . . . 5.::4 5.3 REFERENCE CASE EXPOSURE SCENARIOS . . . . . . . . . . . . . . . 5-5 5A EXISTING LAND USE SCENARIOS . . . . . , . . . . . . . . . . . . . . . . 7 5.4.1 Realistic Current Use - Standard Scenario: Resident-Farmer .... 5-8 5.4.2 Realistic Current Use - Modified Scenario: Hunter-Camper ; .. ~ 5"'.8 5.4.3 Conservative Current Use - Modified Scenario:
Resident-Homeworker . . . . . . . . . . . . . . . . . . . * . . . . . . . 5-8 5.5 FUTURE LAND USE EXPOSURE SCENARIOS . . . . . . . . . . . . . . 5.:9 5.5.1 Realistic Future Use - Modified Scenario: Hunter-Camper ..... 5-9 5.5.2 Conservative Future U~e - Modified Scenario: Residence-Trailer 5-10 5.5.3 Other Potential Use:s . . . . . . . , . . . . . . . . . . . . . . . . . . . 5-10 5.6 ESTIMATES OF POTENTIAL SCENARIO DOSES . . . . . . . . . . . . 5-11
- 5. 6.1 Resident-Farmer Scenario . . . . . . . . . . . . . . . * . . . . . . . . 5-11 I 5.6.2 Hunter-Camp~r Scenario . . * . . . . . . . . . . . . . . . . . . . . . . 5-14
TABLE OF CONTENTS (Continued) 5.6:3 Resident-Homeworker Scenario . . . . . . . . . . . . . . . . . . . . . 5-15 5.6.4 Future Use, Conservative Scenario: 'Residence-T~et Scenario . 5,.16 5.7 SENSITIVITY ANALYSIS . . . . . , . . . . . . , . . . . ._. , . , .. ; .. 5-20
5.8 CONCLUSION
S . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . 5-24
6.0 CONCLUSION
S . . . . . . . . . . . . . . , . . . , .. . . . . . . . . . . . . . . . . , . . 6-1 6.l RA,DIOLOOICAL CHARACTERIZA1JON ON A COA.:Q.S,E GRID .... 6-1 6.2 RADIOLOGICAL CHARACTERIZATION ON A FINE GRID . . . . , . 6c.1 6.3 DOSE ASSESSMEN1' . . . . . . . . . . . . . . . . * . . . . . . . . . . . . * . . . 6-4
- 7. 0 EEFEREN"CES -. . . . . . . . . . . . . .. . . . . . . ' . . . . . . . . * . . *. . . . * . . .. 7-1 LIST OF *TA~L:ES Table Title. Page No.
1..:1 Annual Background Radiation Dose . . . . . . . . . . . . . . . . , . . . . . . 1~5 2*1 Soil Radioactivity (pCi/g) in 1982 Samples ..... , ....... , .... , . 2.;7 2-2 Radioactivity Corresponding to Contour Codes in the 1984 Aerial Survey ........*..... , . , . ~ .*.. , . . . . . * * . . 2-12 J-1 Actual .Sample Locations . ~ ....... ~ . , .*... ! , -. .* **. , ** ,.**** 3-5 3-2 Radiological Instrumentation Cesium Prong Investigation . . . . . . . . . , .*...........*.* , ..... , . . . . '3-10 3-3 Study Area :Reported Survey Results . . . . . . . . . . . . . . . . . . . . . . 3-13 4-1 Radiologicai Instnmientation wNYNSC Off,.Site Radiation Investigation, Phase It ..................... ,.. 4-10 4-2 Detailed Grids Used to Evaluate Horizontal and Vertical Depqsition Variation and Sarripling Sites in Disturbed Areas 4-12 4-3 Soil Activity in Detailed Grids . . . . . . . . , . . . . . . . . . . . . . . . .- . 4-15 4-4 Averages arid Ratios for Cs-:137 Activity in 0*2" Surface Soil Layer . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 4-18 4-5 Cs-137 Activity ip Disturbed Soils . , . , . . . . . . . . . . , , , .. , . . .. 4-'.20 4-6 ~orrelation *Factors for Secondary Instruments Dliring Fine Grid Survey . . . . . . . . . . . . . . . . . . . . . . . .....*. , . . . 4-'.24
LIST dF TABLES (Continued) Pate No. 4-7 Comparison of Soil Activity (pciig Of Cs-137 in 0-'2" Layer) by Correlated Instrument and Laboratory Analysis * , **.***...* ...*.....******.**.. , . * . . * * . 4-25 5-la Summary of Critical :Si;:enario Parameters Used in fyfodeling :Potential Doses . . . , . . , .., . . . . . , . . . . . . . *. . . . . . 5- 13 5-lb Potential Doses ........... * ....... , . . . . . . . . , . . . . . . . . 5-13 5-2a Summary of Critical Scenario Parameters Used in Modeling Poterilial D¢ses . . . . . . . .*. , ....*.*. , ~ , * . * .* * . . 5-15 5-2b Potential Doses . . . . . . * . . . . . . . , . . . . . . . , * * . . . . . . . . * . 5-15 5-3a Summary of Critical Scenario Parameters Used in Modeling Potential Doses . . . . * . . . . . . . . * . . . . . . * . . . . . . .* . .5-17 5-3b Potential Doses . . . . . . . . . * * . . : . . . . * . . . . . . . . . . . . . . . . 5-l 7 5-4a Summary .of Critical Scen.ario P~meters Used in Modeling Potential Doses . . . . . . . . . . . . . . . . ; * . . . . . * * .* . . . 5-19 5-4b Potenti.al Doses * . . . . . . . . , . . . , . . , . . * . . . . .* , *. , ~ *. ,. 5.,1~ 5:-5a Summary 9f Parameters Used Jn Sc~nario Mod~lirig . . * . . . . . * * . . 5-20 5.,5b Summary of Doses by Pathway for Reference Exposure s~en:ari.os . * . . . . . . . , . .. . . . . . * . . . . . .. . * . . . . . , * . . .* *
- 21 LIST OF lilGURES Page No.
2-1 Loc*ation of the Western New York Nuclear Service Center ........... , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2~2 2-2 Off-Site 1979 Aerial Survey . . . * . . . . . . . . . . . . . . . . . . . . . . . . 2-'6 2-3 1982 Gamma Radiation Survey Ar~ .................... , . . 2-S 2-4 Cs-Prong as Defined by 1984 Flyover Survey * . * . . . . . . . . . . . . . 2-11 3-1 Proposed Sample Locations and Coarse Grid Study Area . . . . . . . . . " 3,..4
LIST OF FIGUREs
* (Confum~d) . **
3,:4 Actual Sample Locations . . . . . . . . * . .. . . * * . . : . . . . * . . . , . . . 3-8 3.a Exposure ;Rate- (HPIC) Readings . . . . .. . . . . . . . . . . . . . . . . * . . 3-15 3.=4 Dose Rate (BICRON) Readin:gs , , ...*.. , ..*.... ; ... , .... j...:tg 3-5 Cs-lp7 Activity CQncentration in O" - 4" Surface Soil Layer ** * . . . . ** . . *... . -. .. .* ." .* * . . . .. . . . . . . . * . . . . . . * . J.;22 Cs-137 Soil Activ~ty Vs. Expo$ure Rate for Locations L~:..:uo ., . . . . . . . . . . . . . . . . . . . . . . ,. . *. . . . . . . . t * * .. ,... * "
- 3-25 3~7 Cs.:; 137 Soil Activity V~. Dose Rate for Locations Ll .:;L40 . . . . . . . . . . . . . . .. . . . . . * . .* . . * . . . . . . * . * . * .. . . 3-26 3-8 :b&M Cs-137 Soil Activity Vs. Teleqyne Cs-1:17 S.01'l. Activ1ty
. . * * * * ..* .* .. . . * * . * .. . . * . * . . * . * *. * . .* * * * * , * * * .
- 3--28 4,.,i 1984 Contours or Cesium Prong an.cl ,LQcation of Proposed Fine *Grid. . .. . II * , * * * .. * * .. * , '!' * ~ '." .. * * * * .. * * * * * .. .. _. * * .* * *
- 4~3 4-2 Initial Boundary of Fine Grid Area . . , * . .. . . . . . . . . . . . . * . . . . . 4-4 4-3 Grid Location Designation for Soil Sampling . . ~ . . . .. , . . . * . * .. ~ * . 4'"6 4-4 Fine Grid Area with Sample Locations .... .. ., ... ... -~ .*. . ~ . 4-8 4..5 Instrument Correlation ................*. , . . . . . . . . . . . 4-22 4-6 Fine Grid A.rea wit~ Average Grid Activity Concentration {PCi/g) . . * . . . , ..*...*.... , , . .. * * . * . . , .. . . 4~30 Contours of Average Cs-.137 Cort~entriltions 4.,31 4-8 Finy Grid Area with Walkover Exct;:ption EXplanation *Notes . . . . . ; . .. . . . . . ..* . . . * . . , . . ~ . . ~ . . . . . 4-35 4-'Sl Fine Grid Area with D6§e Rate at 1 .Meter frqm Groun.d (microRem/hour) . . . . . . , , , . , , .*....... ~ . . ..* . . . . , . . . 4-39 4-;10 Contours of 95th Perct:ntile Total Dose Rates (microRem/hour) . . . * . . . . . . . . . . . . , . . . . . . . . . . . . * . ; , . 40 5-1 Pathways Bl_ock Diagram ..... :... ~ ....* ~ .*.....*...... ~ . 5*3
Section 1 INTRODUCTION 1.1 OVERVIEW .Am> ORc;.ANIZA TION OF ~ REPO;RT In November 1993, the New York State Energy Research and Developm~nt Authority (NYSERDA) contracted with Dames & Moore to perform an evaluation outside the boundaries of the We8tern New York Nuclear Ser\lice Center (WNYNSC). The WNYNSC Off-Site Radiation Investigation was designed to confirm the radionuclide distribution reported by previous aerial and gtound surveys, tQ define the loc~tion of
.elevated regions of :radioactivity with better precision than the aerial surveys, and to estimate the dose aSs¢ciated with the radioactive materials and* the radiation distribution observed ..
The objectives in cQnducting the evaluation. of radi9active material. distriJ:?ution in ()ff-site properties are to obtain better data for use in the joint environmental impact statement under way for completion of t~e West Valley :Oemonstration Project an.d .clo?ure of existing.facilities at the WNYNSC and to determine whether and what measures might be necessary to limit indiVidual exposure to that radioactivity.
- TM investigation was*perfonned in several ph~ses of field sampling,. measurement. and analysis. Section 2 discusses the history of operations at the WNYNSCimpacting on the off-site region. Seption ~reports on th!! radia1:ion characterization perforro~d on a coarse
.grid of 100 meters or more in the approximately 1000 acres northwest of the WNYNSC extending to Cattaraugus Creek. The radiological characteriiation performed on a fine grid, lOm x lOm, is discussed in Section 4. Potential doses to individuals in the fine grid stutjy area from current and future land uses are estimated fo Section S. The conclusions of the investigation are provided in Section 6 and refere[lces for this report are listed in Section 7. Extensive data from the numerous s~mpling and instrument survey protocols are compiled in a Technical Data Annex, published as a sep?.Tate volume.
WNYNSC Off-Site Radiation Investigation 1-1 April 20, 1995
The remainder of this Section of the report provides an explanation of radiation terms and a discussion of applicable regulations and regulatory guidance on the level of residual radioactivity that may be considered a level for concei:n. Radioaccivizy refers to physical matter that is unstable and will decay by spontaneous emission of alpha particles, beta particles or gamma rays *trom the nucleus of the atom. Radiati<:n is the energy released as the decay occurs. Atoms that eniit radiation are called radionuclide~! Isotopes are atoms of chemical that have the same number of protons and electrons as other forms of the chemical element but different numbers of rieuttons, resulting in different atomic; masses. For ~Xa.mple, the element hydrogen has two stable isotopes, H-1 and H-2 (deuterium), and one radioactive isotope, H-3 (tritium). The _numbers following the element's symbol identify the atomic mass, which is the number of _protons pfos neutrons in the nucleus. Radionuclides or radioisotopes are unstable iSotopes that will decay. Once a radioactive atom decays h1to_ another atom by emitting .radiation, the resµlting daughter atom also may be either radioactive or stable. F.ach radioactive isotope has a unique half-life that represents the ~me ~t takes for 50% of the atoms to decay. Cesium-137 has a half-life of about thirty years~ while plutonium- _239 has a half-life of 24 ,000 years. Radiation may consist of electromagnetic rays such as x-.rays and gamma rays or alpha or beta particles. F.ach radionuclide may emit one or more of these.radiations at charaGteristic energies that-cart be used to jdentify them. In the decay of Cs-137, each decay results in the emission of one gamma ray with 661 kiloelectr.on volts (keV) of energy .arid one beta .particle with up to 1176 keV of energy. 1.2.1 Radiation-Do~ The energy released from a radionucUde is eventually deposited in matter encounte_red along the path of radiation, resulting in a radiation dose to the absorb_j_ng material. The WNYNSC Off~Site Radiation Investigation 1-2 April 20, 1995
~bsorbing material c~ be either inanimate matter or living pssue. Compared to other types of radiation, *alpha particles have the largest mass and leave a dense track of ionization a,s they travel through tissue aitd tlms deliver the most dose per unit mass. However, alpha particles are not penetrating and must be taken into the body by inhalation or ingestion to cause harin. Beta and gamma radiation tan penetrate the protective skirt layer of th.e body from th~ outside to deliver a whole b.ody 9ose _or expose internal organs. However) beta and gamma radiation deposit much less energy in tissue per unit mass. relative to alpha radiation. 1.2.2 tliiit:S :or Measurement The U.S. unit of measurement for amount of radioactive _material or the. a~tivity is the curie. The activity is proportional to the quantity of radioactive material which decays in a unit of ti.me, 1 curie = 3.7 x 10i0 disintegrations per second (dps). Because the. curie is a reiatively lar~e amount of material, equivalent . to the decay rate of 1 gram of taqiu:rn, activity is usually expressed with a prefix; a microcurie (µ.Ci) is 1/1,000,000 {one-milliQnth) .or 1 x 10-6 of a curie, and a picoCurie (pCi) is l/l,000,000,00Q,OOO (one. trillionth) or i x 10"12 of a curie. The international unit of activity is the bel;qilerel (bq) which is very small.compared to the curie: 1 c~rie = 37 billion becquereis or 3.7 x 10 10 bq. Thus one becquerel is one disintegration per second. Radiation exp9sure is the amount of radiation energy measured in air by collecting the charged ions produced by the radiation interaction. Exposure is an indica,tiolil of the int¢nsity or magnitude of radiation in air that may or may not be *absorbed by tissue if a person were there. The unit of exposure is the roentgen (R) ;md submultiples such as miiliroentgen (mR) or microroentgen (µR). The speed at which radiation interacts in the air is expressed as an exposure +ate, such as microroentgens per hour {µWhr). Tue U.S. unit .of measurement for the amount of radiation energy absorbed in tissue, Dose Equivalent, is the rem and represents the amount of radiation energy absorbed in VINYNSC Off*Site Radiation Investigation 1-3 April 20. 1995
tissue. The international µnit of mea.Surement pf dose equivalent is the .Sievert (Sv), which is equal to 100 rem. The milfirem (mrem) and millisievert (mSv), used more frequently to report low dose equivalents encountered i~ environmental exposures, are the equivalent of one-thousandth of a rem or sievert. The dose equivalent concept was developed by the radiation community to compare doses from different types of radiation. The Effective Dose Equivalent (EDE) was developed to account for the relative risk of radiation exp9sure to a particular organ or tissue. The EDE is calculatt;d by multiplying the dose equivaient to a particular organ by the organ-weighting factors developed by the International Commission on Radiological Protection (ICRP). The. weighting factor is a ratio of the risk from a specific organ or tissue dose to the total risk resulting from whole body irradiation. All organ-weighted dose equivalents are then summed to obtain the EDE. The dose from internally deposited radionuclides usually is cal~ulated for a fifty-,year period following one year of intake and is called the fifty-year Committed Effective Dose Eqµivalent (CEDE). The total EDE is caiculated by adding the dose equivalent from external, penetrating radiation to the CEDE. Unless otherwise specified, all doses diScussed here are EDE values; which include the CEDE for internal emitters. 1..2.3 Sources of Radiation Members of the public are routinely exposed to different sources of ionizing radiation from both natural and manmade sources. Table 1-1 shows the relative importance of the annual dose in millirem (mrem) from these sources. The National Council oh Radi~tion Protection and Measurements (NCRP) Report 93 estimates that the average annual effective dose equivalent (EDE) received by an individual living in the U.S. is about 360 mrern (3,6 mSv) from both natural and manmade sources of radiation (NCRP, 1987b). WNYNSC Off-Site Radiation Investigation April 20, 1995
Tfible 1-1 Annual Background Radmtfon Dose
. . Natural 29:S rnteffi, .
.Cosmic : 28 Terrestrial ! 28 I:D.ternsl i 39. -~ ' : .
*Radon '200
. . . . . . . . . -::39...
*Nuclear .Medicine *:J4.
Coo.sumer ProductS. _., __ . . __l_Q____. , _ _ __ .....
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Other*(ajr trayel, .~_i9'.) . 2. TOTAL. . '~ 360 ., mrem AS Gan be ~.e'en ii1 Table 1-1, natural sources of radiation contribute 295 _mreiri of the total annual dose of 360 mrem. W1lile most of the radiation dose affecting the general public iS background radiation, nianmade sources of radiation also contribute to the average radiation dose to individual member$ of the public. Such sources indude diagnostic and therapeutic x-rays, nu~le.ai" medicine, fallout horn atmospheric weapons tests, *effluent from nuclear fuel cycle facilities, and consumer products such as smoke detectors and cigarettes. The primary effect of chronic exposure to low-levels of radiation in an individual is generally assumed to be an incr~ed risk _of c'!llcer. Radionuclid~ entering the body through air, water, or food are usually distributed in different organs of the body. Fo:t example, some radiqnuclides such as tritium, carbon-14, or cesium,-137 are distributed uniformly throughout the body. Isotopes of iodine concentrate in the thyroid. Strontium, WNYNSC Off-Site Radiation InvestigatiOh 1-5 April 20, 1995
plutonium, and americium isotopes concentrate in the skeleton. When inhaled, uranium and plutonium isotopes remain in the lungs for a long period of time. Therefore, depending on the radionuclide, different organs may receive quite different doses as a result of exposure to radioactive material. Moreover, at the same dos.e levels, certain orgaJIS (such as the breast) are more prone to developing a fatal cancer than other .organs (such as the thyroid). Because of the uncertainty and difficulty in measuring increased cancer resulting from exposure to ionizing radiation, a linear model is used to predict health effects from low-levels of radiation. This tnodel assumes that there is an effect on the exposed person at all dose levels even though the body may effeetively repair damage incurred from low-levels of beta and ~amma radiations. The c~inogenic effects of radiation on humans have been observed only at relatively high doses and dose rates, such as in the case of the atomic bomb survivors. "Studies of populations chronically exposed to low-level radiation, such as tho~e residing in regions of elevated natural backgro.und radiation, have not shown consistent or conclusive evidence of an associated increase in the risk of cance:r (NAS, 1990)." 1.3 APPLICABLE REGULATIONS A,ND REGULA TORY GUIDANCE The most direct reg11latory limit would be one in which a concentr.i.tion of radioiSotope* is identified beyond which management response or cleanup is required. Currently, such a numerical regulatory limits are not available for radionuclides iii the environment. Most radiological clean-ups in the U.S. have involved site-specific criteria due to recognition of site specific characteristics that impact on the hazards associated with different amounts of radionuclides. Federal and State agencies recently have ma.de strides to provide generic evaluation guidance and criteria to enable more consistent application of regulatory compliance. These guidance criteria are in the form of limits on the dose that may be experienced by the public from residual radioactivity on properties released from further controls. WNYNSC Off-Site Radiation :Investigation 1-6 April 20, 1995
In addition to specific and generic clean-up crl.teria ali regulatory systems -invoke the concept of As Low As Reasonably Achievable (ALARA). ALARA m~~*making every reasonable effort tO maintain e~posures to .radiation :as. far hclow the limits as is practicai consistent wlth the ptitpose Of the activity; the economics of lowering exposu(es in rel_atiori ~ the benefits to the publ~c health. and safety, and other sociew and socioeconomic considerations (NRC, 1992b). The use of the ALARA concept applies
- a. "reason:ibility" criterion to the decision making process w~en weighing risk, benefit, money and effort- for .dean-up and compliance activities.
the Nationai Council on Radiation Protection and Measurements (NCRP) is chartered by the U,S. Ccmgr~s tp c;ollect, analyze, develop and disseminate in the public interest information and recommendations about protection against radiation. For members of the general pubiic, the NCRP-recomme.rids an annual limit of 100 mrern fQr contjnuous exposure tQ radiation sources and an annuru limit of 500 mrem for infrequent exposures due to all anthtopo*genic (mw-tnade) sources and that ALARA be practiced b_elow that. They further recommend that wh.ere there are multip1e sources of exposure, no single souree or set of sources should result in an individual being exposed to more than 25 mrem annually (NC~, 1987a). 1.3.2 U.S. Nuclear Retrulatory Commission The U.S. Nuclear Regulatory Commission (NRC) does not cuqently have generic cleanup -criteria for radiologically contaminated sites. In the past, the NRC has decommi5Sioned sites by e~tablishing site-specific criteria for each Jicensee. NRC decommissioning policy allows higher concentrations of radioactive materials to remain in the soil with_ deed restrictions and/or continuing control of the propei:ty fpr restricted li$¢S- ,.(NRC, 1992a). WNYNSC Qff-Site Radi_ation Investigation 1-7 Aprii .20, 1995
At the present time the NRC is conducting a rqlemaking to establish generic decommissioning criteria for sites contaminated with .radioactive materials. The draft rule published in .August 1994 proposed an .annual dose-Ilmit of 15 mrem to a member of the Critical Group for residu.al radioactivity distinguishabl¢ from background, The final rule has not yet been published (NRC, 1994b). 1.3.3 U.S. Environmental Protection Agency The U.S. Environmental Protection Agency (EPA) has not established definitive generic cleanup criteria for radiologically contaminated sites. Pre5ently the EPA 1s working w.ith the NRC to ensure that the NRC decommissioning criteria are consistent with EPA requirements. Proposed EPA regulations for radioiogical cleanup standards indicate an annual dose limit in excess of natural background radiation levels cif 15 mrem/yr over the first -30. years, a value consistent with the NRC limit. Within this standard, the dose to the exposed individual through the groundwater pathway has a separate limit of 4 mrem/yr (EPA, 1994). 1.3.4 u.S. Department of. Energy The U.S. Department of Energy (DOE), intends to establish guidelines for personnel exposure during decommissioning activities to. co,rnply with the requirements of DOE Order 5400.5, Radiation Protection of the Public and the Environment, 1990. The actual cleanup criteria for DOE facilities will be governed by the EPA regulations discusSed above. 1.3 ..S New_York State Department of Environmental Conservation <i\TYSDEC) NYSDEC has not promulgated a regulatory limit for clean-up of radioactively contaminated sites. In an internal administrative guide, the NYSDEC has described a dose guidance for sites contaminat!=!d with radioactive materials (NYSDEC, 1993a): WNYNSC Off-Site Radiation Investigation 1-8 April 20, 1995
The total effective dose equivalem to the maximally exposed indiVidual of the general public, from radioaciive material remaining at a site after cleanup, shall be as low as is reciSonably achievable and 'e~s than 10 mrem above tliat received from background levels of radiation in any one year. In .describing the basis. (or this guidance, the NYSDEC Com_missioner discussed the Agency reasonin~ Ifwe design a standard/or a maiimum exposed individual in the general public who might be exposed to several soi+rces (e.g., at work, at home.~.) the accumulated dose should still be small relative to total exposure from natural sources. SQmething behveen 10 and 25 mre~/yt aci:omplisnesthi~. We chose 10 mrem/yr, which serves this purpose as well as automat.ic.aily assuring Ai.ARA considerations *... (NYSDEC. 1993b}. Since dose~ this lbw cannot be rhea.Sured directly, to demonstrate expected doses, the* NYSDEG requires that the modelin,g a.Qd analysis be referenced to "rea.Sonable scenarios for current and plausible future ,usieS of the land.;, The 10 mrem/yr guidance dose refers to land released for unrestricted use. If the unrestricted use scenario analysis results fo -dose estimates ~eater than 10 mrem/yr', the guidance indicates that institutionai controls may be necessary to ensure that the guidance dose of 10 mrem/yr is not likely to b~ ex~ed. 1.3.6 Iriitiai :pose Rate ~vs. Accumulatecl nose. Expressing .the release criterion as a dose rate, *rather than as a dose, introduces a misperception in the risk associated with exposure to the residual radioactivity. The basis foi; estaplishirtg soil radioactivity guidelines is to limit individual h~th risks by controllin~ the accumulated radiation dose to theindivid,ual (NCRP, 1987a; EPA, 1994). WNYNSC Off-Site Radiation Investigation 1-9 A?rii 2Q, 1995
The basic assumption of stating the limit as an annual dose .(mrem in a year) rather than a total dose (mrem) is that the limiting annual dose on which the soil guideline is based is acceptable for the entire duration of the exposure. In tJi,e case of a resid¢ntial exposure scenario, the assumption is that the residents of the site will be exposed for thirty. (30) years. For sites contamin;ited by racl.ionuclides with long haif~lives, such as uranium or thorium residues, tJi,e initial dose rate wm be maintained for an ext~nded time, over hundreds and .even thousands of years. Under some circumstances, the dose rate may even increase with time due .to in-growth of daughter radionuclides. In the area adjoining the. WNYNSC, Ute only significant radionuclide is Cs-137, which has a half*4ife of only 30.2 years. This means tha.t a dose rate from the .affected area today will inevitably be reduced to only one-half as much at the end of 30 years. Applying a uniform dose rate criterion to the dose in the first year will result in the accumulated do~e to individuals residing in an area of declining dose rate to be much less than the acceptable (guideline) dose. For example; consider a control criterion of 15 mrem/yr at a site with a fong-lived radionuclide. For a thirty-year exposure evaluation period, the accumulated dose at the limiting criterion would be 450 mrem (15 mrem/yr
- 30 yr). 'For the WNYNSC Off-Site area. containing only Cs-137, an initial dose rate at the control limit (15 mrem/yr) would decline to 7.5 mrein/yr after 30 years; the accumulated dose would be only 3i2 mreni (450 mrem times 69.3%, a coefficient accounting for the radioactive decay during the exposure perioq). Thus the application of a dose rate limit results in an estimated dose delivered to a .resident 30% below the accumulated dose basis for the guideline. One consequence of this misperception is that propercy with residual radioactivity of short half-life may be identified as requiring management or clean-up when it actually was already below the level that would produce the equiv<ilent accumulated dose.
WNYNSC Off-Site Radiation Investigation 1-10 April 20, 1995
One* method to avoid unnecessary land use restrictions or ~leantip is to adju~t ~e initial annual dose control limit to achieve an equivalent accumulated dose fo the individual throughout the expo$t.ire perioo. That is, art initial dose rate of 21: 6 rriremlyr from Cs-137, falling to 10.8 mrem/yr after 30 years, wc;>uld result in the *s~nie accumulated dose as a uniform dose rate exposure of 15 :tnrem/yr: 21.6 mrem/yr** 30 yr"' 69.3% == 450 mrelll = is mrerhlyr
- 3o yt Thus a regulation of equiva.Ienf accumulated dose rather than dose rate in the first year indicates that *the initial dose tate criterion in an at~ *with short half~life radioactive material should be adjusted up. In the case of Cs-137 tne adjustment would be 44 %
(e.g. Jrpffi, 15 rnremlyr .tq 2L.6 IT}reni/yr) of the corresponding un~form dose rate. Raclioactive decay will occur durin~ the.period of exposure evaluation to reduce the dose rate to only 72 % of the t.1niform dose ra.t~ at th~ encl of the period. The result is an accumulated dose to the residents lnat is eqt,1ivalent.to the up.iform dose rate that is the basi!i .for ijle regulatory criterion. WNYNSC Off-Site Radiation Investigation 1-li April 20~ 1995
Section*2 DESCRPrfIQN OF UIE*sruny .AREA .2.1 LOCATION
" - . AND*I:>EscRIPTiON
" . - - .- ~ " *- ' . -' -
The WNYNSC site is. located approximately SO kilometers (30 miles) south of Buffalo, N~w Yor:k. Th~ \VNYNSC occupies J ,354 nectaies (3,340 acres) almQst entirely within the town of Ashford in Cattaraugus County. A drawing of the general location of the WNYNSC is provided .as F'.igure 2-l. NYSEJWA hOlds titlet9 the WNYNSC art b~ha!f of the people of the State of New York. Facilities at the WNYNSC include a former commercial nuclear fuel reprocessing plant. The fud reproc~sing plant wa~ operat~d by Nuclear fuel Ser'ii.ees, Inc. (NFS) .from 1966 to 1972. A State-licensed commercial low-level radiOa.cti've waste disposai area (SDA) was also operated by NFS at th~ WNYNSC .until 1975. In 1983 responsibility. for roairitainirig the ~DA was officially traIJsfeqed to NYSERDA. Pursuant to the West Valley Demonstration Project (WVDl?) Act, in 1982 the U.s.* Department of Energy took possession of an SO-hectare (175~a,cre) piot n~ the center pf the WNYNSC encompassing the nuclear fuel reprocessing facilities. Current activities of' the WVDP are directed toward treatment and solidification of the high-level radioactive was~ an.d. deconta.m.ination of the facilities used in the project. The nearby population, approximately 9 1200 residents within 10 kin (6,2 mi) of the. WNYNSC, relies primarily on an agriculturcil economy. No major industries are located within thi.s #e'.a; The Ian<;! immediately adjacent to the WNYNSC is used primarily for agriculture and arboriculture. WNYNSC Off~Site Radiation Investigation 2-1 April 20, l.995
I 79 00'00" 1a30* oo* BUFFALO SITE LOCATION New York
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!!!p~2~.5~iiiii5~~~1~0Miies AFF!!OXl!u.Te SCALE Figure 2-1 Location of the Western New York Nuclear Service Center
~ PAMES & .MOORE.. March 2s, 1995
2.1.2 *WNYNSC Off.Site.. **-*Radiation Investigation
. -** - . .. ~ - .
.St-tidy.
Area The Off-Site Ra:diatior+ Investigation study area lies in the town of Ashford o.n the west side of the WNYNSC, northwest of the former reprocessing plant. It extends from the .western property line, approximately 1;5 km from t.he plant stack, npithwest to .Cattaraugus Creek, approximately 4 km from the plant. Several prior studies have demonstrated .'patterns of slightly elevated. radioactivity in this area. NUCLEAR OPERATJONS IMPA~CTJNG.T.ffE OFF-SITE INVESTIGATION STUDY AR.EA." ' . .*. .. . . . In 1966 the U.S. Atomic Energy Commission (AEC) issued an operating license to.NFS for the nuclear fuel reprocessing plant and related radioactive waste management facilities. The reprocessing operations were designed to recover uranium and plutonium from sp~nt nu~lear reactc;>i:' fuel through the '.'PUREX" chetniCa..l *extraction process. Iµ 1972, NFS sh,ut the plant down for expansion, modifications and additions, but for varioµs re::\~ons it never resume<l reprocessing operations. In 1.976, NFS informed New York State .that it intended to leave the reprocessing business and not to renew the lease when its Initial term expirep. During the six years of operation, the pl~t proGCssed approximately 640 metric tons of spent nuclear fuel, about. thr~-quaners of which was provided by th¢ A:ec~ artd generated abpJ.lt *~o,QOO gallons pf ,high-lev~l liquid w'J,Ste.S; which were stored in underground tanks at the site. During the opera,ti_ng period, NFS reported routine and non-routine releases of airborne radioactive materials to the AEC. A review of the AEG Compliance Inspection Reports from May 1968 to August 1972, documented problems with the process building ventilation system from the startup in 1966 until the system was modified. in the fall of 19.68. The most notable discharges occurred in 1968. The only month when diseharges ex.ceeded the licensing standards was in Match, 1968 when an estimated 0.25 curies of radioactive material (12~% bf the monthly ~imit) was released from the Process.Building WNYNSC Off-Site R.adiation .Investigation 2-3 April 20, 1995
main stack as a result of a filter blowout. Analyses of the fiiters tndicate that most of the particulate activity was from Cs-137, Cs-134, Ce-144 and Zr_.95/Nb-95; while Sr-90/Y-90 and alpha emitters are assumed to have provided < 14% and < 1% of the activity, respe~tively (SAIC, 1994). In an event repor:t for the March 8-10 release filed with the AEC; NFS atrributed .the release to a filter failure in the dissolver off-gas system. Weather data included with the NFS rep-ort indicated that the wind was blowing at 10-16 mph to the west and northwest on .March 8th at the time of the greatest release. NFS reported that " .*. a thorough. survey of the perimeter monitors for radioactivity showed tha:t contamination levels were un.changed from prior readings. The radioactivity levels we:re not higher than pre-operational data collected before the beginning 'Of plant operations." (NFS, 1968). 2~3 PREYIOUS RADIOLOGICAL EVALUATIONS AND. STuDIES 2.3.1 '.Eadv studies The. initial aerial surveys of the NFS reprocessing plant site were in 1968 and 1969 while the plant w:as operating. The Sl.Jrveys were performed by fixed wing airctaft at an altitude and flight pattern that developed a minimum detectfon limit of 15 micro"' Roentgen per flour (µ.Rlhr), measuring exposure rate from ill gamma radiation. These survey~ did not mes_sµre any radioactivity outside the WNYNSC boundary above the re~oried minimum detection level. (EG&G, 1971) A surfac~ soil sample takeri by the NYSDEC northwest of the Pf9Gess Building main stack and close to the Center boundary in 1971 reported radioactivity concentration in the soil of 58 picocuries per giarn (pCi/g) of Cs-137 (dry). Other soil samples taken at comparable distances in the north, .east and southeast directions from the stack exhibited Cs-137 concencratfons of less than 2 pCi/g (NYSDEC, 1972). 'NNYNSC ()ff-Si~ Radiation Inve~igation 2-4 April 20, 1995
The next aerial sur\iey was performed ~n 1979 after the plant had .ceased reprocessing operations. Using more sensitive instrumentation and a tighter flight pattern this survey develope:d an analysis With a minimum detection limit of 9.5 µWhr from *a.JJ gamma radiation sources. Compare:d to the 1969 aerial surveys this suniey showed a genera! decrease in exposure rates close to the plant, consistent with operations at the plant having beeri suspended sif).ce 1972. ~ecause of the greater sensitivity artd .altered flight paths relative to .the 1969 overflight, the 1979 survey also showed .an .area of gamma radiation slightly abo\le lhe detection 1¢vel (exposure rate 9.5 - li µR/ht) to the northwest of the plant extending beyond the WNYNSC boundary. The appearan~ of this northw~st extension of radioactivity was not from a rele.ase: occurring between th~ two surveys, but arose from the difference in the radiation deteetion and analysis capabilities that occurred betw~n the two surveys. .Computer assisted separation of the gamma energy level identified the contributing radionuclide as Cs:..137, a ~h.aracteristic fission product radioactj.vity. The .elevated level of Cs-137 radioactivity outside of the boundary was reported to contribute 1.4 - 2.4 µRlhr to the total gamma exposure of 9.5 - 11 µRfhr observed from all gamma sources (EG&G, 1981). The are.a of eievated off-site radiation is shown in Figure 2-2~ Due to its shape and content, the site deseription was commonly referred to as the "Cesl.uni ?rong."
- The ~leva,ted gamma .radia~on exposure rates within the off-site area were ~mparabie to natural. background in other parts of Western N~w York. The Cs-137 distribution pattern could only be di$criminated from prevailing gamma radiation in the :a!'ea by using instrumentation that could distinguish the specific gamma radiation energy for Cs-137.
WNYNSC Qff,Site Radiation Investigation 2.,5 April io, 1~95
N (j
- t SCWARTZ AO.AD I
LEGEND: DETECTABLE Cs-137 Q 0.4 -1 .4 uA!llr DETECTABLE cs-137 0 1.4 - 2.4 uR/!ir Figure 2-2 Source: WVDP:014, 1982 Cesium Prong Contours from Environmental Characterization Report 1979 Aerial Survey 9 D AMES & MOORE Marcll 29, 1995
2.3.2 WVDP Environmental Characterization Report CWVDP:Ol4, 1982) When the WVDP was initiated in 1982 , one of the fust activities was to verify the nature and distribution of the source of radiation shown by the 1979 aerial survey. This evaluation included a walk-over survey with hand-held instruments and soil sampling at four locations in the off-site area. Results of the soil radioactivity analysis are summarized below in Table 2-1. The area of the walkover and the sampling locations are shown in Figure 2-3. Table 2-1 Soil Radioactivity (pCiJg) in 1982 Samples 1982 Re-analysis in 1993 Location Sample Analysis (activity corrected for decay back to 1982) (see Depth Fig 2-3) inches Cs*l37 Cs-137 Am-241 U-235 Pu-239 Sr-90 I-129 A 0-4 30 44 0.081 <0.001 <0.05 0.81 <0.004 A 4-10 14 18 0.040 <0.005 <0.05 0.42 <0.004 A 10-16 0.45 0.69 <0.001 <0.004 <0.05 0.17 <0.004 B 0-4 0.31 0.42 0.003 <0.001 <0.001 0.10 <0.03 B 10-16 26 0.04 NA NA NA NA NA c 0-4 7.6 7.1 <0.01 <0.001 <0.003 0.31 <0.03 c 4-10 0.30 0.54 <0.001 <0.001 <0.002 0.21 <0.03 c 10-16 0.04 <0.02 NA NA NA NA NA D 0-4 2.5 4.3 <0.03 <0.004 <0.02 0.27 <0.06 D 4-10 0.06 0.04 NA NA NA NA NA D 10-16 0.04 <0.01 NA NA NA NA NA NOTE: Location codes shown on Figure 2-3 and 1982 data from WVDP 1982. NA = not analyzed WNYNSC Off-Site Radiation Investigation 2-7 April 20, 1995
r3 ** N SCWAl'lTZ ROAD
\
SOil.. SAMPLE* *A AREA OF SURVEY r', 6ACKGROUND Q 10*13 uAlhr DETECTABLY ELEVATED READINGS~ 14*16 uR/hr MEASURABLY ELEVATED R!:ADINGS~16-20 uRlhr Figure 2-3 Source: WVDP:014, 1982 Environmental Characterization Report 1982 Gamma Radiation Survey Area 9 DAMES & MOORE MartM9, 1995
Two samples from close to the centerline of the elevated area (Locations A and C, shown in Figure 2-3) were found to average 30 and 7.6 pCi/g (dry) in the top 10 cm (0-4") of soil, respectively. Two samples obtained away from the central radial (Locations B and D, shown in Figure 2-3) displayed Cs-137 radioactivity concentrations of 2.2 and 0 .7 pCi/ g (dry) in the 0-4 inch surface soil layer. Samples below the surface depth did not contain significant Cs-137, with one exception (location code B, 10-16"). This activity at depth was explained as: One sample from a previously tilled field now used for hay cropping indicated background levels in the upper layer of soil. From JO to 16 inches depth, a sharp increase in Cs-137 concentration was found .... Shonly after deposition, the ground -.wis probably cultivated preventing water or air dispersion and retaining the deposit in a relatively thin layer at plow depth. (WVDP, 1982). The ground measurements of external gamma radiation made in 1982 were consistent with the pattern of the 1979 aerial measurements. Differences in magnitudes were most likely due to the extrapolation of aerial measurements to ground level values reported by the aerial survey. The majority of the area surveyed on the ground and noted as "detectably elevated" in Figure 2-3, agreed with the aerial survey and showed gamma radiation from 1-3 µRlhr above measured background of. 10-13 µR/hr. Two smaller areas identified as "measurably elevated" in Figure 2-3 were within 3-7 µR/hr of the measured background radiation level.
- WNYNSC Off-Site Radiation Investigation 2-9 April 20, 1995
In evaluating the impact of this gamma radiation deposition, the conclusion at the time was that The detected off-site contamination nonhwest of the plant is at a level below NRG guidelines for corre.ctive action requiring decomaminanon .... No hazard exists in relationship in this deposition through any established pathway to man. ry/VDP, 1982). In November 1993 the original 1982 soii samples were obtained from WVDP archived storage and submitted again for radioactivity analysis. These results, corrected for radiological decay back to the 1982 sampling date, are also shown in Table 2-1. These 1993 measurements confirmed the 1982 data results in magnitudeofCs-137 concentration and also confirmed that the Cs-137 was largely confined to the upper 10 inch layer of ~oil. The observation of elevated activity p.~ depth for sample B, depth 10 to 16 inches was not confirmed. When the 1993 gamma spectroscopy analysis indicated greater than 0.1 pCi/g of Cs-137, the analysis of ~he archived samples was expanded to include alpha spectroscopy for americium-241, uranium radioisotopes, plutonium radioisotopes, as well as chemical separation to analyze for strontium-90. The analysis revealed that radionuclides other than Cs-137, when present in the samples from 1982, were at levels typical of ambient environmental occurrence. 2.3.3 Aerial Survey of 1984 CEG&G. 1991) The shape of ihe cesium prong region was re.:confirmed by a further aerial survey in 1984 which used even more sophisticated and sensitive instrumentation. Contours of Cs-l'.37 radioactivity reported by the 1984 survey are shown on Figute 2-4. WNYNSC Off-Site Radiation Investigation April 20. 1995
76.2 Explanation
\>---
'l*~ G_.---
1/ Contour* from 1984 flyover survoy 15:4 by EG.!cG *. MQp source 1$ th~ T0wn of* ,\5hford 15:1. . Ta~ Mop.. ,propart)' llr>o"' ond other feoturos wore dlglllz&f by means ol 27.1 computer aided drolling. Figure 2-4 Cs-Prong as Defined by 1984 Flyover Survey
This flyover refined the contours of the ar~ of elevated Cs-137 radioactivity in terrris of counts per second in .a multichannel gamma radiation analyzer set for the Cesium gamma radiation energy regiOn.
- Due to the flight speed, height (46 m) and field of view (120 m) of the aerial detectors, the soil concentration in pCi/g corresponding to the contours can only be assigned proad categories of values, as indicated in Table 2-'2.
Thus 11).e highest contourreporteci in the off-site area; the "C" level, could range from less than 8 pCi/g to 25 pCi/gt or more, depending on the.actual size of the affected area on the ground. Table ~-2 Radioactivity *corresponding to Contour Codes in the 19~ Aerial Survey Contour Net Cs-137 Distribution in Distribution in Cade counts per 300. m diameter 50 m diameter pe5ignator second (pCi/g) ( p~i/g) A <66 .< 0.9 < 4_-.5 B 66 .- 140 0.9 - 2.0 4 - 10 c 140 - 310 2.0 - 4.3 8 -25 NOTE: "Uniform volume" indicates homogeneous mixture of soil to a depth of7-10 cm throughout the indicated diameter (Source: EG&G. 1991). The 1984 aerial survey again demonstrated that; even though a pattern of slightly elevated Cs-137 gamma radiation was observed, the total gamma radiation exposure rate (which include5 terrestrial and cosmic components) did no~ exhibit the same distribution pattern. Thus the magnitude of the radiation exposure due to the Cs-137 deposition was within the normal variation in ambient gamma radiation. due to mi.turally'-occurring radionuclides in the soil and fluctuations in the cosmic radiation background. (EG&G, 1991). The contours presented iri the report of the 1984 aerial stirvey were used as the planning basis for this evaluation of the Qff.;.Site Radiation Investigation area. The re-analysis of the samples archived since 1982 indicated that Cs-137 was the only isotope of concern WNYNSC Off-Site Radiation Investigation 2-12 April 20, 1995
in the ar~_aM that it appeared .to be residing in the Sl.!rface. layer of soil, ciown to four inches depth . .Z.3.4 Summary Aeri~l surveys performed in the vicinity of the WNUtSC bave dem~:m~tiated:
- The total gamma, radiation exposure rates in off-site ar~~r around the WN)"NSC were 1101 elevated in any distinctive pattern and were comparable to natural background in other parts of Wes(ern New York.
- Measurements focused on only Cs-1$7_gamma radiation indicated an a.tea running northwest from the process building rriain stack ci{lpi:oximately 4 krri with Cs-137 gamma radiation exposure rates slightly above the ambient levels in Western New
. Yqrk. The presence .of Cs-13_7 was observed by using instrµm~rits-set to detect the gamma radiation energy of only this isotope.
- The Cs-137 ~arnma radiation from man-made origins was detectable, but the radiatiqn *exposure levels meas1,1reci are less than the fluctuation in natural background radiation from place to place in Western New York.
WNYNSC Off-S.ite Radiation Investigation 2-13 April 20, 1995
- Plia$~ *I; Program:
Q,Q,<tifS;~ (jri}J, iiiili<1.i~liici!i th~t~lt:t:lW!lJ<<!ll.
"~ ' ,*;~ . ' '" ' . f" ', ', ' " " .'-' ' .' " 't."' " <' *' ' ' .' ': " ' '... , "* ' " ' * "
1 "
Section 3 Pl.IASE I :PRQGRAlVt COARsE :GRID ' . ..
' ~.
RADIOLOGICAL
. . ' - . CHARACTERIZATION 3.1 OVERVIEW .OF *nm COARSE;GroD SURVEY 3.1.1 '.Pin:Qo..i\e A coarse grid was established to define the ~ea of interest, The coarse grid survey would combine mea,sure111.e11ts pf ambient ~diatipn level.s and soil radioactivity to determine ~round level radiation for comparison with contours of radiation from pjevious aerial surveys. The survey wa.~ strµctured to broa~Uy locate aff~cted ar~
identified by the aerial surveys and to evaluate them on a fine grid to accuratety define c*urrent concentrations and spatial distributions over 100 % of the* affected area. 3.1.2 Survev Components In order to sample and evaluate the radioactivhy and radioactive materials deposited. ~n and arou.rtd the WNYNSC Off-Sit~ study ¥ea, Dames & Moore initially perfonned a Coarse Grid Survey. The Coarse Grid Su~ey consisted of the following components:
- Identify background .sample locations in areas which were *unaffected by the release causing the cesium prong outlined by the aerial surveys;
- Identify coarse grid sample locations which. enable an adequate number of measurements in the affected area identified in previous surveys in order to define a focus area to localize the edge of significant Cs.-137 levels;
- Locate the . propose9 .ba~kground
. and coarse gtid sample
. locatic;)lis in the field; WNYNSC Off~Site Radiation Investigatim1 3-1 April 20, 1995
- Measure external radiation levels at the background and coarse ~rid locations with a high pressure ionization chamber {HPIC);
- Mea.sur~ external radiation lev.els at the backgrqund and coarse grid locations with tissue-equivalent microtem meters;
- Sample surface and near surface soils at the background and coarse grid locations for field screening of Cs-137 content and subsequent laboratory analysis; and
- Establish correlations between soil radioactivity concentration, HPIC readings,
.and tissu~-equivalent microrem meter readings.
These major components are discussed further in subsequent paragraphs of this section. Details of technical procednres and analysis criteria are provided in the Technical Work Plan for the <;:esium Prong Investigation (D&M, 1994a). 3.i.3 Grid Layout The coarse grid sampling locations were established to allow detailed meastirements in th.e affected areas showin,g the largest deviatioq from background (as identified in the 1979 and 1984 aerial surveys), and to provide sufficient samples in the surrounding
- locations to localize the edge of the affected area.
a, Proposed Sampling Locations. The coarse grid initially established 40 proposed sample locations in the study area, as illustrated in Figure 3-1. The proposed sample locations along the offset central radial are at 100 meter intervals beginning at 1.5 Ian from the Process Building main stack (approximately the WNYNSC property line) artd extending out to the 2 km point. Sample locations are at 200 meter intervals from the 2 km point out to the 3.8 km point or the bluff at Cattarau,gus Creek. (NOTE: at the 2.2,km point the "offset central radial" takes a 10° counter-clockwise WNYNS<:; .Off-Site Radiation Cnvestigation 3-2 April 20, 1995
shift to follow the centroid of the 1984 aerial survey illustrated in Figure 3-1. The "straight certttal radial" continues unctianged). Four sample locations are located along each outsjde radial (15° either std(:! of the straight certttal radial) and four location_s are qn each cif four intermediate radiaI (10° and 5°.either side of the straight central radial) at the 1.5, 2.0, 2.5 and 3.0 km radial distanc~. 1
- b. Actual Sampling Locations. Proposeci sample loc;ation_s were pr'i¥Jefine4 on a large scale map as described above. How_ever, final placement of the ac;tu;U .sample locations were dependent upon factors .such as the -si_te' s conditiOn and terrain, snow cover, weather conditions? ancJ the landowner's permission to access properties.
Actu Iha' Town of A'hford lox_ Map. Proporty lines and olh*r SQO)fe: fo feel f~aturos 'ware dlglllzod by n1oons ol L'.! lO.~ 2000 compuler->>oldod drortlng. ~ a 100 Mo
- 400 Mlaoa Scnhi In >>nelets Figure 3-1 Proposed Sample Locations April 19, 1995
Table 3-1 Actual Sample Locati-0ns Location Terrain CQtnm.!!DtslNotes cm L_ocation SPRVL *yard approx 9 km North of Process Building main stack;
. .. _. __WYDP air srunple'r k)cf!ti()!c\j_.l,il?.ckg~ou~9 . __
- WEVAL yard approx 7 km Southeast of Process Building main stack; WVDP *air*~mpl¢r \oe1JiiC~n~' backgmwul RT240 field approx 2 km Northeast of Process Buiiding main stack;
.. wvDP air,~ampl~r *I¢1tlon; :bec~;grourid.
'-~***-- ~ **~-*"
- W** ~- **
Ll 15;1 woods L2 15.1 woods L3 ,, 15,1 woods woods L4
.. 15.1 lS IS.3 : woods Sa.mpling position "C", ground survey;
... ).~~2 \YVDP Cbaracteri7.ati9n SurVey L6. lS.3 thick woods.
L7 61 apple orehard,
' 'very thick
_. lregetal lO!f 57 side yard This location WaS in the side .yard area of a re5idence, bclllnd a "memorial" area containing shrubbery iµid a small r~ljirio4§ t~ statue. L9 29.4 front yard
- Located ..-.3 m N.NE of existing property survey marker.
_______ * .M_C>v~ from 29.7 p~r..propert)' owner requ¢st. LIO 29.8 front yaro Located ro m from telephone pole on property line; {15-20m. from r~,a((h Lll 29.2 tree farm , Sample point located midpoint between center field access road and* western field access road along northern
. \\'.?O~!ine .
Ll2 6 woods .. M:easured from NW comer survey marker on property 1129.2 '(:1$0, m N I 50 m \V): Ll3 4.1 woods. Point located. at NE comer of clearing, - 30 m east into
.. woods. * .L14 2 woods ---
L15 ' 23.I field L-Ocated halfway, front to back, in field. 99 m to the N from the road along the.E edge of field. Moved from 17
;per pr9pen.y own~r req)J~SL .
WNYNSC Off-Site Radiation Investigation 3-5 April 20, 1995
Table 3-i Actual Sample Locations {Continued) Location :
- Propefey II Terrain Comments/Notes 1jn Location Ll6 16 woods From Ll7; S 101 m I W 41 m. Generally 130 m SSW of Ll7. -20 m from stream bed along S (E-W) property lin(f, Near l~g~ beaver dam.
Li?" f3.2 woods Starting frrii;n western 90° 6on.1)~;t' of wV prqperty line; i 77 m W. :flroin N (E"W) property Jin~; 67 .9 m to the S. Generally SW 130 m from LL sampling position "D ", ground survey; 1982_\VVDP CharacterizB:t_ion ~U:~~y. __ Ll8 14 (y/V) ; *grassy area 38.~ m due W from Rock Springs Road.
' *between road and wo9ds Ll9 14 rNv)
- open field;
._grass1.
L20 14 fYVV) open field; Located 100 m NE from roadside fence at. a point
,grass)rc perpendi\;ul~_ to_ (feer ;,~r~~-~l:!lg _sigJ?. _
15.1 , sid~ yard, sampling positjon "B", ground .surv.ey;
;_ali:ini fence , 1982 \VVDP Ch~cterization Sii&~y*
L22 15.1 backyard Opposite sfoe of house from 121. Located between house near" ~g~* of field~
._,_~*
L23 i5.3 com fieild t
.. L24 64 L25 66 side, vati:f.
~-
J..26 77,1 woods Across .the street from Li5. Point located to the W of a
. ~jtp~Wr~a~ fi1~~ipg.th.0ugb t~e wooi:ls. .
127 27.l : field 128 27.1 . field Approximately 10 m (from N edge) of property. Located just outside. Of \VOOded_ ar~. 129 I* com field Moved to property N of Thont5()!l Corner Road per
. ~YSDEC and NYSER].)A -~~~t;-
L30 56 , yarc!
~ - - . --- .
131 75 yard Point located 57 m S of Rock Springs Road, 49 ril E of
**driveway~
L32 10 front ylµ'd by Sampled twice (L32 & L42). Locations possibly separated driveway, near by driveway. road WNYNSC Off-Site Radiation .Investigation 3-6 April 20, 1995
Table 3-1 Actual Sampie Locations (Continued)
- Location ' ... ~op~rty ti_ .* . . Te~in Comn:ients/Notes on i.;oe,ation i,ocated 50 .feet from creek crossmg, 140° from N. Mov.ed from 10 pi;r NYSEIDA ~ije;~~.
I.34 29.6n.9.3 "y;oods
""' /, *-* ***** **W" - *<>* **"'" .-: ""'-
µs 29;3/29.12 , woods Point located along eastern N.;S boundary line between
~9;r2 and 29.3 ..* -6.Qm S_bfpo\vet_lines.
13.6 29.9
- grassy area 6 m E o_f W property line 13 m S from road; between road *
, ilei,i.r .mad and tree!iile. ' .
L37 29.2 '*tree* farm EW plane: everi with ea.stem edge of pond. NSJilil.Qe! ~oll'~ tree:line between the 2 sets of fi~lds. 6 located just off dirt road running b.!~een rows, at the .:ind ' L38
. _ti! }!ne of small tree,i; . snwinJ{ ~ th\! fieJd area. ..... 1 L39 6 L40 . 14(WV) woods - l 70 m along tram frackS east of bridge*. Moved due *to :sfo *
,conditions and terrain. 18.Sm ~and 26.5 m ndrth of
- {n~~#ng barbed. wire fences.
- L41 field ..,.so mW ofbouse,On hill overlpokiilg WvDP; approx 2 k P,.
.~:_of J:>r.aJe$S*.l1u!14ing; tn;ain stack L42 10 , front yard by see L32 driveway by road MWl woods EP-L 23.2 woods . 70 m N and 10 mW of concrete marker at comer of
. WNYNSC and property 16; sampling position "A", grou11d.
~fyey; .1982 wynR auuacterization .$l:(ryey RSPRD '14 (wv) clearing in ;ipproit LS km Northwest of Pr9cess 'l3i4~di!Jg main stack;
*woods ,WVDP air s;impler locatiqn i.n the C~ium -:flrqng.~ a~
WNYNSC Off-Site. Radiation Investigation 3-7 April 20, i995
_j. [-~ Explanation Actu.ol Sample Locollono* II
]1,1
+ - .. Mop ISOU(Co ls" ltio rQWll ot A*hlord Tole Mop. Properly lines* and alhor features wero dlgll!2ed by. rnoan* of compulor aidod' drafting.
Scale in (eel D* son 1600 *2ooa
~=-CM}
o ioo eoo 400 eoo Fi.gure 3-2 Scale in meters- Acfuol Sompre* Localions i.:: -!lL ___________......______________ g'DAMF.S 13£ *MOORE _ January __,!;~~====::.::::::::::::::J. __:__12, 1995
For *,ease Of comparison with lqng.;term environmental monitoring efforts in 'the region, bac}.::ground locations for this survey were chosen at-locations that are part of the routine sarppljng network fo_r the WVJ)P, The location codes for the background measurement sites and. a brief
' . *ctescriptioh are:
SPRVL WVDP air sarnp1er location 1n Springville, NY; approximately 9 km north of the _Process :eu.ilding main s_tack, WEY AL WVDP air sampler location in West Valley, NY; approximately 7 kin southeast of the Process Building main si:ack RT240 WVDP air sampler location on Route 240; approximately 2 km east of the froces~ Building main stack. The locations are fully described in the WVDP Site EnVironm~nrai Report (WVDP, 1992). ~.1.4 Instrumentation Radiation data were gathered at each of the 40 sampling locations using tttre~ .different types of instrument. Data from these three field instruments were recorded on field data logs arid are Qn file. Instrumentation information is Sl!mmarized in Table. 3..:2.
- a. Dose Rate Survey. Dose rates were measured using a radiation rate meter :Sensitive to. gamma radiation (Bl.cron microrem meter). The Bicton microrem meter uses a tissµe-equivaleht organic scintillation detector that provides the operator With ~al time measurements of dose rates down to 2 microrem per hour (µrem/hr). The instrument 1,1ses a meter. ~d ru~edle analog display that limits the precision of .the reading.
WNYNSC Off.-Site Radiation Investigation 3-9 April 20, 1995
Table 3*2 Radiological lnstmmcntation Cesium Prong: lnvestigation
- Instrumentation Detection Type of Measurement Background 1 Sensitivity i Deteetor Meter A. FlelC! lnstrumeriis
_Exposure Rates High Pressure Ion Chamber {same us detector) 7-911-Rfhr lµR/hr 2 Reuter Stokes, Inc., Model RSS-112-100 mR Dose Rates 3
';fissue-et1uivalc:n\-,- organic scintillator (same as d.ateclor) 3'-5 µRein/hr I µRem/br Bicron 'Corporation, Model MforoRem Sufface scans - Pancake GM Count rate metet 30 cpni 30 cpm 4 J
beta-gamma "Ludlum Measuremenls, Inc., Model Ludlum Measuremenls, Inc., Model 44-9 3 ' - " ' - '- Gammu activity - soil Nal scinlillution, 4" x 5° ut!ltctor Multichannel AMlyzer NIA 0.56 pCi/g 2
\' .(fi~ld scr~riing)
- BiCron <<Corporation Canberra Ind., Inc., Model Series- ro l Plus
- n. Laboratory lnstrumenls ""
Gross cr:/fi - soil _Gas _pr_opor_Ll-Onal counter -(saroe*ns <l¢iec_for) lcpm "' *-
~pCi'lg Isotopic Identification - soil Germanium detector; >55-cc Multichannel Analyzer NIA. 0.-05 pCi/g Gamrna*.:S[>e:tlroscopy ""
Nuclear Data; Mooe! 6620 or 6700 _, "
'Isotopic Identification - soil Silicon diode surface barrier Multichannel Analyzer NIA 0.02 pCi/g
, Alphu Specfro~opy . *-*-. Canberra Ind., Inc. Model 7404 . Canberra SlOO Data Amilysis.Sys(em Notes l nominal values 2 30 minute count 3 viewing analog scald anil need)~ 4 moniloring. audible sigonl WNYNSC Off-Site Radiation Investigation . 3-10 April 20, 1995
-/
- b. Exposure Rate Survey. .Exposure rate data were obtained using a portable high pressure ionization chamber {HPIC) with a detection sensitivity of one microroentgen per hour (µR/hr) or less. The HPIC was set up *r0 measm:e 220 .ten-second average exposure *rates. The* HPJ.t: has a digital readout of memory and reports the average, the standard deviation of the reaclings, and the ll)aJCimum and the minimum ob5¢rved readings during the programmed period of analysis.
- c. .Soil Radioactivity Screening'. Soil samples collected during the survey were field screened for gam!'la activity using a 4 x 5 inch. sodium "iodide (Nal) detector coupled
~o a rimlti-Chru:mel analyzer. Tfle gamma scan (!Jlalysis is capable of detecting and Identifying many radioactive materiar:s at a single analysis. The technique measures the num)Jer ;rnd el),ergy of pho.tons emitted by i;adioactive materials contained in the soils; The energies of the emitted photons are used to determine the identity of the radfonucJide ~mitting the radiation (e.g. Cs.:.137) and the number ,of photc;ms is used to determine the activity (picocuries) of the radionuclldes present. The multi-ch;rnnel
*analyzer ahd. Nal .sc:intiUation device used f9r the field screen were capable of detecting 0.56 picocuries per gram (pCifg) of Cs~137 in soil.
- d. Outside la}1oratpry analysis. Selected soil samples were sent to laboratoriesfor fur:ther analysis.* These analyses included measur~m~nts of gross alpha and gross beta activity md isotopic identification via gamma and alpha spectroscopy. A :gas proportional .counter with a deteetiori sensitivi~y Qf 1 pCi/g was used to. measure gross alpha and beta activity. Gamma and alpha spectroscopies were performed using a germanium detector an.d a silicon diode surface barrier (respectively), each coupled to a*multi-channel analyzer. Detection sensitivities for tfie gamma and alpha spectroscopy instruments were reported as 0.05 pCi/g and 0.02 pCi/g, respectively.
WNYNSC Off-Site Radiation Investigation 3-11 April 20, 1995
-~-
3.2 l\1EJJIQ:PS AND RESVLTS 3.2.1 Gamma radiation Exposure Rate <HPIC) Survey
- a. Methods. Once coarse gnd iocations were established in the field, an evaluation of radiation exposure rate was performed by collecting high pressµre ionization chamber (HPIC) measurements at background locations and each of the actual sample location~ illustrated in Figure 3-2.
1'he HPIC d~t~ctor was mounted on a tripod one meter abo_v(! the gro1,1nd at each of the actual sample points. The HPIC measured the ambient gamma radiation from naturally occurring radioactive materials in the ground (terrestrial), cosmic radiation penetrating the earth's atmosphere from space (extra-terrestrial), and radiation from man-made materials deposited on the* ground (fallout). HPIC reading~ were collected for approximately 36 minutes, which resulted in 220 individual 10 second measurements at each location.
- b. Results. The gamma radiation exposure rate measured with the HPIC at the background loqitions ranged from 7.8 + 0.6 µR/hr to 9.0 +/- 0.6 µR/hr. Average HPIC readings in the Off-Site study area ranged from 7:4 +/- 0.6 µR/hr (at locatfon L14) to 11.2 +/- 0.8 µRlhr (at location L38). Average exposure rates above 10 µR/hr were measured along the straight central radial petween 1.6 and 2.4 km fi:om the Process Building main stack (locations L2 to LS and L8). Results of the HPIC readings are listed in Table 3-? and illustrated on Figure 3-3.
WNYNSC Off~Site lladiatioll Investigation 3-12 April 20, 1995
Table 3-3 Study Area Reported Survey Results Fixed J,ab Fb:ed Lab Field Screen Field Screen Average Average Depth 0-4" Depth 4-10" Depth 0-4" Depth 4--10" 1 Meter 1 Meter Cs-137 Cs-137 Cs-137 Cs-137 . ~lkro Rem ,1w1t Locatiog. *,(pCy)~ (p¢ijg),~' :<"cil'>*
.P .. _,g *;fpCifgf" .(pr~m/h~) >~R,1h';)
SPRVi.. 0.32 +/- 0.04 0.070 +/- 0.035 <0.59 <0.5~ 3.*7 +/- LO ~-8 +/- 0.8_ WEVAL Q.40 +/-.0.04 0.23 +/-,0.04 <0.56 <0.56 3.7 ;t 1.3 9.0 +/-; 0.6
., .. -** '"' _,~, --- ,., ~*
RT240 i.o_ ;1: o.~ 0.35 .+/- 0.04 <0.82~ <0.65 3.4 +/- 0.8 " 7,8 +/-: 0.6 ' . Ll 6.7 +/-. 0.7 1.1 +/-9:1 .4.08 +/- OA*!:i <0.65 . --* 4.7 +/- I.~ 9.6 +/- p.8 Li 5.0+/- 0.5 O.i9 +/-o_.64 ~.59 +/- 0.4:0. 50A5 4 . 9 +/- I.5 10._1 +/- 0.8
' ~.
L3 5.4 +/- o._5 0,21 +/- 0.04 3.4 +/- 0.401 <0.56 5.1 +/- 1.4 ' 10.0 £0.8 ' L4 4.7 :+/- o.5 0.23 +/-_0.05 - -~,09 +/-' 0,36 <0.5~ 5.2 +/-.LB 10.2 +/- 0;8 L5 4,5 +/- o._4 (),64 +/- ~,06 2.74 +/- 0.3§) ,i <0.5_6 5_'.2__ :J:. ?:~O 10_.2.+/-.0.8
******- ~*- *-**
L6 2.s .+/- o.3 NIR 1.94 +/- o.~7 <0.56 ----~:9~:E}:~ !I.. ?_ :I: o.8____ L7 3.0 +/-0.3 N/R_* o.9 +/- o_.35 <0.59. 2.2 +/-_ 2.4~ 9.6 +/- 2.2 LS 3.2 £9.J " Nl_!l " "
'l.J~ +/-:0_.34 3
<:0.:56. 3.7+/- p 10) .+/-. 6.4 '
i..9 ().97_*+/- 0,1 NIR, <0,56 <0.55 4.6 +/- 1.4 _!1.15 +/- l.4 LlO oA~+/- 0.04 NiR. <0.56 <0.55 4_) :+/- 1.3 9.2_;t: L2 Lil 0.12 +/- ().03 NIR <,0.55 <0.55 ' 4.4 +/- LS 9.4.+/- 0.8 Ll:.! I.6 +/- Q.2 N/R 0.5 +/- 0.:34' <0.55 3.9 +/- _i.4 8.5 :;i: 0.6 L13 1.4 +/- O.I N/R <0.55 <0.55 3.8 +/- 1.7 8.1 +/- O.S L14 2.1 +/-: 9.:! ]11/R <Ci.SS <0.5_5 3.4_ ':!: L1 7.4 .+/- 0.6 L15 0.28 +/- o.o4 NI~ <0.61 <0.61 4.5 +/-:.1.5 9.3 +/-:0.8 L16 --*' 0._33 +/-0.06 " N/R ~0.6~_ <().61 4_.~ ;t 1.9 9.1 +/- 0.8 i.11 p +/- 0.1 N/R <0.61 <0.61 4A +/- 1.7 8.8 +/- 0.8 Ll8 q+/-o.2 NIR
<0.61 <0.61 4.5 +/- 1.6 9.4 +/- 0'.8 Ll9 1.6'+/- 0.2 N/R <0.61 <0.61 4.3 +/-'.!.O 8.5 +/- 1.4 L20 0.9 +/- 0.09 N/R <0.59 <0.59 4.4 +/- 1.4 9.8, +/- 6.6 L21 0.4! .+/- 0.0_5- NiR <0.54 <0.54 3.0 +/- 1.3 . ! ..
9.3 +/- 17.4 " L'.!2 ().37 +/- 0.06 N/R <0.54 <0.54 6.8 +/- 2.4 9.6 +/- 0.8. LP o.34_+/-. o._q4 N/R <0.56 <0.56 2.6 +/-. 1.2 9.7 +/- O.B L24 2.0 +/- o._2 NIR 0.64 +/-0.34 -- .. < 1.14'
*--*-*****-*r***-*-*
4.5 +/- 1.6 S.4 +/- 0_.8 L25 0.9'.l +/- 0.09 ~/R <0.56 <0.56 4.5 +/- 1.8 : 9.l .+/- 0.14
=Dry Weighi: 5 = Clo.ssified as an outlier 2 = Wet Weight N/R = Analysis not requested, surface activity < 3.5 pCi/g 3 = Average of Primary {A) and Duplicate \B) sample result!!. NIM = Not monitored, instrument not e.vailab!e 4 = Insufficient. volume for lower LLD * +/- = UnceIUint,ie. expressed at :? standard' deviations (95% Confidence Interval).
WNYNSC Off-Site Radiation Investigation 3-13 April 20, 1995
Table 3-3 Study Area Reported Survey Results Fixed Lab FiXed'Lab Field Screen Field Screen _Average Av~i:"age Depth (}..4 11 t)epth 4-rn" Depth 0-4 11 Depth ~10" 1 Meter 1 Meter. cs~131 Cs-lYf I, Cs-137 D*l37 Micro Rem HP£C I.Ocatio11 I (pCiJ)i ., (p9i/g)l . _;(i:>C!fi~t .... _ ...~pc'i!ii,f! (µremlffr)
~-
- ~~th.~)
L26 I 1.0.+/-_0'.1 .. ,_ NIR <0.56 <0.56 3.5.£. 1.6 SA*+/- *o.8.
--*- ., -~ *----* -*"' **-*- -* . -~ .
L27 I _0~4T ~ o.os . N/R <0.56 - .. <::0.56 __ ,,_ .... *U .+/-..1.:1.. _ 9.4 +/- q.8 L28 *- J 9-~ +/- ..9,~ .. . _!'l{R <0._5~ ......... -.; .. - <0.5,6 4.6 # -1.6 ' ~M +/-.o.~ 1.29 .I 0.52 .+/- ;0.05 . N/R <0.55 <0.55 ..... . 4_'.8 .1:: ) . 6 .. 9~8 .~ ~:O L3Q I 1.1 +/- O;l f-!/R <0.56 <0.57' 3.S,..+/-}-0. . ' .?..:O+/-.<p_._.,. L31 I 1.2 .:f:.*0,1. NIR 0.65 +/- 0.34 <0.5() 4;0 +/- 1.'.~ .* 8;3 +/- 1.2
.. ~~f ... I .o.s9 -;t .0.06 N/R '---* ... -~0-~-~ -- *--' <0.54 4.3. +/- l.~ 8.6 +/- Q.8 L33 r 0.93 .i+/-:. 0.0!? N/R <0.56 <0.56 4.5 +/--2.2 8.7 +/- 0.6_
.L34. 1. o.s6 +/- o.09 , ,N/R <:0:56 <:0.56 4.2 +/-'l.7 8.3 +/- 1.6 LJS l 0.9~ +/- 0.09 N./R .. 0.7:0 _+/- 9-~~ <0,56 3.8.+/-1.7 7.9 :+/- 2.4__
L36 I j},96 ;+/- 0.1 N/R <O.S~ <O.SS 4.5 +/- J.6 9.3 ~+/-. 0.8__ L37 I o.~ :+/-:_0,03 NIR <_O.SS <0.5~ 4.6 +/-. 1.6 9:9 +/- o.~ L38 I Q.~5 +/- _0,03 NIR <0.59 <0,59 .5.5:+/-. L5 11.2 +/- 0.8 L39 I o.39 +/- o,o4 . NIR <0.54 <0.54 3.9 +/-.LS 9.5 -+/- i.s L40 I Ll +/- 0.1 N/R 0.56 +/- 0.33 <0.55 4.8 +/- L6 8.9*:+/- .0.6 I.:41 I o.41 +/- o.o5 !'UR <0.55-NfM 4_.I.+/-. r.5 N/M L42 l 0.28 +/- 0.04 N/R. \ . <o.ss NIM 4.9+/-:1.5 NIM ____ -!>'.f'W:l *- ' 7,3 +/- 0.7 1.5 :+/- 0.1 NIM NIM - -- .. _____3_:2._ +/-)_:3* J NIM EP-1 12 .+/- l.O 4.0 +/- 0.4 NIM NIM 3.? ..+/- 1.7 I' NIM RS:P~ N/R N/R <::0.824 <0.824 3.5 +/- 0;9 .I s,s +/--o.s -~ 1 = Ory Weight S = Classified as an outlier 2 = Wet Weight N/R = Analysi~ not requested, surface activity < 3.5 pCilg 3 = Average of Primary (A) and Duplicate (B) sample results. N/M = Notrriooitored. instrument not available 4 = Insufficient volume for lower LLD +/- = Uncertaintie.'! e~prcssed .at :2 stanqard pevfations (95% Confidence Interval). WNYNSC Off-Site Radiation Investigation 3-14 April 20, 1995
;..""'-""'~.....,,,,.,;
+ ...
. .6 Exp la notion
-iji-9*0
*:it?*9 :iji!*f!..10..:;::=::::::::::::~
10.2
-lj(:r. ~.4
-i*3 Actual *sample locollons with HPIC sampling rosu!ls '(mlcroR/hr)
+ Map source Is ii.to Town- of Ashford TaN: Map ... Proporfy Ii nus -and olhor*
- lealun*s* wero dlgllizod .by* moans *of.
compufor aidod dralllng .
.Scale 'in .feet L* 7 iooo 2000
~ ~-.400 ~
0 JOO 200 1100 Figure 3-3 Sea.le in meters Exposure Rate (HPIC) Readings
- c. Data Quality. *upon completion of the data accumulation interval, field personnel reviewed the I:IPIC display and recorded observed values on the field data sheets. When the standard deviation and/or the maximum exposure rate readings were unexpectedly elevated (compared to the average reading)~ an additional l8-minute HPIC analysis was performed. These confirmatory data were recorded on the .app:t"opriate data sheet and were used to either
'i support -the original readings or replace the ori~inal readings if it appeared that an anomalous i nspike" ha.d caused the initial data to be unusually high. At two locations (L08 and L21) anomalous initial data were replaced by the additional HPIC analysis. ,,J
- d. Discussion. Points along the central radl.al (L1 through L8) exhibited average exposure rates greater than 9.5 µ.R/hr, as rec.orded by the HPIC. Exposure rates just as high (2: 9.5
µR/hr) were observed at eight other locations (L20, L22, L23, L28, L29, L37, L38 and
~39). Eleven locations had exposure rates less than or equal to the exp_osures at the. three
(_ background locations. These observations are in agreement with results of the 1984 aerial surveys discussed in Section 2, above.. That survey indicated the ambient level of radiation exposure around the WNYNSC ranged from 7 to 11 µR/hr, and that external gamma radiatjon levels along the central. radial were not significantly different from levels in other areas-. 3.2.2 Tissue-equivalent Dose Rate {microRe~/hour) Survev
- a. Methods. At .each background and coarse grid_ lm;ation, an evaluation of radiation dose rate was performed using a tissue-equivalent Bicroil n-iicrorem meter. Measurements were taken at the three background locations. and at each of the actual sample locations i11ustrated in Figure 3-2.
Bicron microrem meters were used to detect low-levels of radiation dose rate ( < 20 µrem/hr) at each of the actual sample locations. Microrem meters are affeeted by th~ same sources of radiation which affect the HPIC, that is terrestrial, cosmic and fallout. The microrem meters IL were used to measure dose rates at five positions around, .each of the actual sample points. The
. WNYNSC Off*Site Radiation Investigation 3-16 April 20, 1995
first position was .at the HPIC; and the remaining four readings were taken at the cardinal points of the compass (i meters Nortb, South, East, and West of tl:le HPIC). Ten measurements w~re taken at each of these positions; .five at 1 meter and five at 1 centimeter above the groun(l. The readings at 1 meter allowed field crews to view a large a.tea of interest by effectively reducing the shielding effeets of the soil at the perimeter of .the area. The readings at 1 .meter are also more representative of the whole bod.Y dose rates at each .of the actual sample locations. The readings at 1 eentj.m*eter were .used to monitor for the presence of nmt-uniform. dep~sition which could cause higher ioca1ized dose rates, none of which were detected.
- b. Results. the average tissue-equivalent radiation dose rate measured at the background locations range~ from 3.4 +/- 0.8 µRem/hr to 3. 7 +/- *1.3 µRem/hr. Average Bicron. rea9ings
- in the study area ranged from 2.6 +/- 1.2 µrem/hr (location L23) to 6.8 +/- 2.4 wem/hr (location L22). Higher average dose rates ( > 4.6 µRem/hr) wete typic~ly .found in the vicinity ofLl through L9, although radiation leydsjust as high were observed in eight other locations (L22, L28, L29, L37.' L38, L40 and L42). The results of the average microrem r~dings at 1 met~r a.re listed in. Table 3*-3 and. ~e illu.strated by location on Figure 3-4.
- c. Data Quality. Review of the data in Table 3-3 prompted the classific(:ltion of one of the data points as an outlier. The low Bicron microrem reading at location L7 was not inCluded in data interpretation due to a low battery condition inferred by a review of field logs. The high Bicron microrem meter reading at location L22 also appears outlying, but no evidence was found to substantiate this conclusion; therefore L22 values are included in data interpretation.
J Ll WNYNSC Off-Site Radiation Investigation 3-17 April 20. 1995
+
.6 Explanatioh
¥.s.
¥*7~==:::;.,r 4.9
. .2.2 Ai:luol somplo, locollons* with: BJCRON
..i,4.9 sampling. results (mlcrorom/hr)
.J.6y
! 5.2
-ip:.m..5;2
'l .5.2
.4.
+ Mop source Is. lho Town of Ashford Tax *Map. Propoi'ly lines and .olllor rooturos wero digillz<id by mean* of computer- aided drafting. Scale .in feet LZ .1000
~
2000 o 1oa 200 *oo ooo Figure 3-4 Scale .in m.eters bo*se Rafe (BIG.RON) Readings March 8, 1995
- d. Discussion. ._p_ornts along the central radial {Ll through L6 and L9)exhibited average dose equivalent rates greater than 4.6 ,uRem/hr; which is greater than that observed in the background positions', less than 3.7 µrein/hr. Dos~ n,itesjustas high(;::: 4,6 µrem/hr) were observed at seven other locations (L22, L28,*. L29, L37, L38, L40 and L42);
*::foven loeations, ineludillg L8 on* the central radial; had dose eqt1ivalerit rat¢s l~ss* tha.n or e_qual to the rate~ at the three back:gro.und locati,ons.. Thes~ observations are in agreement with results
.pf the 1984 aerial surveys .dis.cussed in Section* 2, above, and the HPIC sunrey. In measm:ements Of total gamma radiation exposure 9r dose, a pattern of contours qf total gamma radiation 'is not evident in the area northwest .of the WNY*Nsc.. Observed values of dose equivalent appear to be. fluctuations in. the ~mbieiit *radiation level due to variations in the cosmic and .ground radioactivity levels.
3~2.3 Radioactivity in Soil Survey Soil samples were ,collected at the .background focatlons and at each of the actual. sample locations illustrated in Figure 3-2. Soil samples w~re.collecte<J for field s~reening ofradioactiVe Cs-'131 conte,nt and for further analysis at a fi~.ed laboratory fac~1it;y 2
- Field screening eonsisted of analyzing soil $amples for Cs-1'37 content using a po$ble multichannel analyzer with .a 4x5-inch N:aI crystal. Fixed laboratory analy~is consisted of mPnitoring spil samples 'by ~ither a full-range anall'sis or an abbrevfa.ted analysis.
- Fµll-range analysis. When the field .screen anaiysis of a Q-4 inch depth (surface) sqmple
*indicated a concentration of Cs-1~7 greater than *2 pCi/g above background? the ~urface I sample and .th.e corresponding 4-10 inch. depth sample wei:e sent for the full t~ge of analyses (percent moisture, gamma scan, -gross alpha, gross beta, Pu isotopes, U isotopes, 2 Soil sample al)~lysis at a fixed lf!boratory f~cility was performed by Teledyne Brown Engineering Environmental Services, Westwood, NJ.
j i WNYNSC Qff.;.Site Radiation Investigatfon 3-19 April 20, 1995
Am-241, Sr-90 and total U). The surface and 4-10 inch depth soil samples from background locations were also sent for full range analyses.
- Abbreviated analysis. Surface samples which indicated less than 2 pCi/g but greater than the field screen analysis detection limit for Cs-.137 (0.56 pCi/g) were analyzed for percent moisture, gamma sc<Ui, .gross alpha and gross beta analyses. Sl}rface samples from remaining locations were sent for % moisture and gamma scan analyses, only.
F'ield personnel collected duplicate and split soil samples for analysis by the NYSDOH. Twelve soil samples were split in the field tµld were submitted to NYSDOH for analysis as a quality control measure of the reliability of the field screen analysis and the fixed laboratory analysis.. Samples collected and not further analyzed are archived with the NYSERDA.
- a. Methods. Samples were collected using an AMS brand Soil Core Sampler with removable alu.minum liner. At each of the actual sample lcx:ations, soil plugs .2 inches (5 cm) in diameter were collected at depths of0-4 inches (0-10 cm), 4:..10 inches (10-25 cm) and 10-16 inches (25-40 cm). In addition, field duplicates and splits were collected at several locations, in accordance with the Project Quality Assurance Plan (D&M, 1994a).
In order to collect a representative sample and obtain the 1000 grams necessary for the field screen analysis, five soil plugs from each depth were colleded and composited into a single sample bag. Sample plugs were collected at a central point (the HPIC position) and at the four cardinal compass points (north, south, ,ea.st and west) on the perimeter of a ¢ir9le with a i meter radius centered on the HPIC. Field duplicate samples were collected adjacent to each of these five positions and composited in a separate sample bag. Soil samples were identified by sample location, sample depth an-d sample type (primary or duplieate). For example, a primary sample collected at sample location 14i from a depth of 4-10 inches (depth 2) was identified as "Ll4D2A, 11 while a duplicate sample collected at sample location 3, from a depth of 0-4 inches (depth 1) was identified as "L3DlB." Each sample bag was WNYNSC Off-Site Radiation Inve5tigation 3-20 April 20, 1995
labeled (using a .permanent marker) with the sample identification and the date of sample coilectlon. b.. Results. In t)1e ba,~kground loca:tjon s~mples, the Cs-137 activity conc¢ntration in U1e 0-4
~heh surface la,yer ranged from 0.~2 + Q.04 pCi/g to l,0 +/- 0.1 pCi/g. In the 0ff.;Bite study area, the Cs-t37 content of the 0-4 inch depth soil samples ranged from 0.12 +/- 0.03 pCi/g Oocation Ll l) to 12 +/-. 1.0 pCi/g (location EP-1). Highe~t activities were pbserved along the central radial .(locations Ll through L5, EP-1 and MW-1). The results of .soil sampling are listed in Table 3-3 anq illustrated on Figur~ 3-5.
- c. Data Oliali~. In six instances, low or no recovery at a particular sample depth *resulted in a sample less than .the optimal 1000 grams desired for the neld screening analysis. This was caused by a variety of conditions including surface water intrusion, h1gh grav~l content of soil, .and the presence of tree roots. Th~ i:iet effect of low rec:;:overy was to elevate the minimum concentration of C$-137 whiGh coµld be*<;le~ct~d by the fje,ld screen analysis, All i
'~
samples sent to the foced laboratory were of .sufficient quantity to be adequately monjtpred
- J for Cs-137 contertL Analytical results reported by the fixed laboratory were validated prior to hiclusion in the r~port. The Validation procedure ensured that the laborat9ty data results were chec~ed for proper exponents and units., .adherence to requested turnaround times ~d for completeness.
Ill cas~s Where requested analysis resµlts W,ere not supplied, Dam~ & Moore contacted the laboratory to obtain the resµlts. In addition, analysis results were. subject to. the fixed laboratory's internal quality ~ssl.i!f11ce procedu~es. WNYNSC Off-Site Radlati9n Investigation 3-21 April 20, 1995
--+-
Explanation
~1:5.2.::;==;;:,'
-$-3.0 -r1*0 Actual sarripla locatlons wllh Cs sampling (osulls (pCl/li)
~ :ijl~.37 J ~.47
+ Mop source Is. tho Town* of Ashford Tax Map. Property lines and other* leoluros. were ,dlglllzod by means of.
*computer. aided drafting.
- Scali?* in feet 1 500
.'0 100~.200 IOOO
*DO
.:r600 Fi.gure 3-5 Scale in meters Cs- f37 Activity Concenfrotlon in' Q" -4 Surface Soil 'Loyer Morch"8, 1995
TwelVe soil sampl~s were spli~ in tlje field with half the volum.e .sent to the contract , I laboratory and the other.half sent to the NYSDOH laboratory~ Four of five samples with J a.ctivity greater than 2.0 pCi/g had a relative percent difference greater than 20%. For each matcbed sample pair, the NYSPOH laboratory analysis result was compared to the .contract laboratory ariaiysis tesult using linear regression analysis~ A graph of the :correlation is provided in the Technical Data Annex. This comparison indicated a strong linear correlation (RA:2 = 0.-97) bet'Ween the two laboratory results. T.tie slope coefficient for the regression was 0.82, indicating that the NYSDOH reported results were s.ystertlaticaj.ly biased at 18% less tflart the result reported by the contract laboratory. the comparison of contract laboratory r~sults to the field screen analysis results is discussed below.
- d. Discussion. Cs-137 levels in soil samples ranged from below 1 pCi/g to approximately 12 pCi/g. Soils with Cs-137 levels equal to or in excess of 4 pCi/g lie within a 520 meter by
'230 meter area beginning at a point L3 km from the Process Building main stack and continuing along the central radial for 520 meters. This area is comparable to that shown in the 1984.ci.erial survey to have the highest local Cs-137radiation1eyels {EG&G; 1991).
3.2A Survev t)ata Correlations Attempts were rriade ld establish correlations between field instrument data (HPIC aAd Bicron), the soil screening measurement and the fixed laboratory soil analysis data. Such a correlation would have allowed extrapolation of fieid instrument readings to soil Cs-137 levels without the time and expense of laboratory analysis. Pearson's* product moment method is the s~tistical method used to test for th~ existence of a correlation. A statistically significant correlation (fa!se positive probability, Cl! = 0.01) exists l when the correlation coefficient, R, is near +/-1 (or R2 is near + 1). l J WNYNSC Off-Site Radiation Investigation 3-23 April 20, 1995
- I a. Field Instrument to Soil Activity Correlations. Using the Pearson product method of linear .
regression, analyses of the.field measurements and laboratory soil analysis do not show any clear correlation between the data sets. The relationship between the exposure rate readings of the HPIC meter and the soil activity of Cs-137 measµred in the fixed laboratory is illustrated ll:t Figure 3-6. The ex~remely low value of the c9rrelation coefficient, :R2 = 0.06, indicate.s a lack of a linear relationship between the two data sets. The HPIC reading cannot be used to infer the concentration of Cs-137 activity in the soil under the HPIC detector. The relationship betwe~n the tissue-equivalent dose rate readings of the BICRON m~ter_ and the soil activity of Cs-137 measured in the fixed laboratory is illustrated in Figure 3-7. The extrem~ly low value of the ~orrelation coefficient, R2 = 0.03, indicates a lack of a linear relationship between the two data sets. The BICRON meter reading cannot be used to infer the concentration of Cs-137 *activity in the surface soil under the BICRON fueter. This lack of correlation may be due in part to the fact that the technique used to measure Cs'-137 levels in soil samples permits tbe exclusion of c6smic radiation and/or *variations in terrestrial radiations (including Radon progeny) from measured results. Afao, the det~ction equipment used to measure Cs-137 soil activity was operated in a controlled environment and was therefore Jess susc~ptible to variations in outside conditions such as temperature, pressur~ and humidity. In contrast, the HPIC and Bicron meters do not have the capability to cornpensate for variations in cosmk radiation and/or variations in terrestrial radiations (including Radon pr.ogeny). This characteristic of the field instruments would be most apparent when, a~ in this stµdy, they are used in an attempt to measure radiation. levels only slightly eleva.ted above background.
- ! WNYNSC Off-Site
- Radiation Investigation 3-24 April 20? 1995
-**1
- ~*
Cs-*137 Soil AcHvity (p.Ci/g). vs. Exposure Rate* (uR/hr)
*For Locations L 1 - L40
- Average err.or associated with a *Single nieasuremerit Of I the activity of a soil sample,
,...-.., 6.0 - (+/-.0.16 pCi/g) en*
""u 0...
*1 Standard error of the mean of the standard deviations
!'"-.. 4.0 of 40 HPIC :points (0.17 uR/hr) n l
(/) u 2.0 7.0 B;O 9.. 0 10.0 1 Lo l2.0 HPIC (uR/hr) Figure. 3-6
*cs-'- 137 Soil Activity vs. Exposure Rate For locations L1 - L40
.DAMES & iiOORE January 12; 1995
.:-~~~
!,,,,,.. ,._..,.,,=
Soil Activity (pCi/ g) vs*. Dose Rate (urem/hr) Locations Lt - 'L40 Average* error associated wit::h
- a single measuremen*t of the adivity of *a soil sample.
,.,........_ 6.0 (+/-0.16 pCi/g)
Q1 u Q_
..____,, ** Standard error of the mean of the standard deviations
("-. 4.0 of BICRON rnodings al 40 n locations (0; 1 urem/hr)
'""I
- I {})
- 0 2;0
*** * (linear regression R = 0.03)'
" - - Besl fit line
*
- 2 o~o
-+-...--.-~~~--~~-.-,.....,.._~-..,-~~-.-*+-..--.-* *
* * *~-.-~....--.--..,-..-.-
.........~~-.-.~~_,.......~~-1 2.0 4.0* 5.0 6.0 7.0 BICRON ( ure*m/hr) Figure 3-7 Cs-137 Soil Activity vs .. Dose Rote For Locations L1 - L4:0 Note: One outlying dalapoint (L22) nol .shown
@DAMES & 'MOORE January 12, 1.995.
-I
- ___ I
' *1
- b. Field Screen Activity to Laboratory Activity Correlation. Regression analysis of the fixed
~J laboratory and field screening measured 0-4 inch depth (Depth 1) soil activity data presentecl in Table 3-3 indicates that a statistically significant correlation exists between the two sets 'I of data. Figure ~.:.8 is a graph of Os-137 soil activity as measured by fi~ed laboratory vs ..
Cs-l37 soil activity as measured by the field screening procedure in the field. A least square -method was used to obtain a best fit line for the graph; The R2 value of 0.93 is a measur~ of me ~tatistical validity of the line (+/- 1.0 indicate_s a perfect correlation), afid indicates that 93 % of the fluctuation between the two analyses is accounted *for in the correlation. The Cs-137 activity .as reported by the field scr~en is consistently lpwer than that reported by the fixed laboratory and reflects the fact that the fixed .lab dried th~ soils before countin~ them while the field screen soil samples were analyze(j wet. Whef1 the field screen Cs-137 activity is corrected for the percent moisture that was present in the samples, values for
. activity more closely approach those reported by th~ fixed laboratory. This correlatl9n serves as a verification of the field screening technique.
3.3 CONCLUSION
S The 1984 aerial survey indicated th.at radiation exposure levels {gamma radiation measured in
~)in~- on all sides of the WNYNSC were in the range of7-11 µR/hr, with no difference in the p~ttem or contours evident in the northwest region. The .gamma radiation exposilre rate measured with the HPIC at the background locations ranged from 7.8 +/- 0.6 µR/hr to 9.0 +/- 0.6
µR/hr. Average HPIC readings in the Off~$ite study area ranged from 7.4 +/- 0.6 µRlhr (at location L14) to 11.2 +/- 0.8 µR/hr (at location L38). This surVey has demonstrated that gamma radiation levels in the northwest region are consistent and comparable to the levels reporteci in the aerial sul"Vey, The levels in the Off-Site Radiation Investigation study area are not unusually eleva,ted from exposur~ rates in the region.
WNYNSC Off-Site Radiation Investigation 3-27 April 20, l995
D&M Cs-137 (wet) vs. Teledyne Cs-137 (dri*ed) For Teledyne Cs-137 Levels > 1.9 pCi/~ 5.0 ~ en u0.. 3.0 "'-.../ I' t'l I ({) 2.0 u 2 6?j 0 1.0 o:o I I I I* 1 I I i I I I I rTTl:-r-1 I I ri 0.0 2:0 4.0 8'.0 Figure 3-8 Teledyne Cs-137 (pCi/g) (dried) . O&M Cs-137 Soil Aclivily vs. Teledyne C~-1,37 Soil Activity
*9...ilAMF.:S. & Mt'lORR .January 1'2; 1995
l The average s()ft tissue dose equivalent. rate iQ the Uni~ States and Canada from cosmic and terrestrial radiation sources is given as 6 µrem/hr (NCRP 1987). The average tissue-equivalent dose .rate measured at the Off-Site background locations ranged from ~. 4 +/- 0. 8 µRem/hr to 3. 7
.+ 1.3 µRem/hr .. Average Bicron readings 1n the study area ranged from 2.6 +/- 1.2 µrem/hr *Qocatiori L23) to 6,8 + 2.4 µrem/hr (location L22). It appears that the average tissue-,equivalent dose rates in the study area are slightly higher than the average tisime-equivalent dose rates at the background lqcations. B:owever; dose to an individual in the Off-Site investigation study area is Jess th~ .o_r comparable lo the national av¢ra~e Jevel.
n LI The sµrvey did identify and confitm regions of local Cs-137 deposition, whose magnitude is small and easily masked by fluctuations in the ambient radiation levels, unless specifically ana1yied for. Cs.:137 levels in soil samples ranged from below 1 pCi/g to approximately 12 pCi/g. Soils with Cs-.137 levels equal to or in *excess of 4 pCi/g lie within a 520 meter by 230 meter area beginning at a. point 1.3 km from the Process Building main stack and continuing along the central, radial for 520 meters. The location of elevated Cs-137 deposits agreed with the contours identified by the 1984 aeri~ survey. However, the level of radiation from the deposited Cs-137 is .$uch that the HPlG apd m!croRem meters are *insensitive to the slight fluctuations in the ambient level of radiation Gaused by the deposited <:s-137, Further cl1aracterization of the area of elevated *cs-137 requires a field. instrument cap~ble of responding to only the radiation .of the Cs-137 m.aterial. The subsequent evaluation of the ar~ of elevat~ Cs-137 is discussed in .the next secilon of this report. WNYNSC Off-Site Radiation Investigation 3~29 April 20, 1995
*. ~*~se.ctfon.*
i '" '" '~~ ;., , ' JI
- ["
1**1 ~Li
Se~tion 4 PHASE II PROGRAM FINE GRID RADIOLOGICAL CHARACTERIZATION 4.1 OVERVIEW .4.1.1
- Purnose Following discussions and review of the data from the. Coarse Grid Survey (Section 3, above), NYSEJ{DA implemented the next phase of the Qff..,Site Radiation Investigatipf1.
A. Fine Grid Inv,esti~ation (FGI) was defined to evaluati= the m~~nitude, deposition patterns and extent of ,radioactive material in the study area on a smiller scale.. Field survey efforts would be fo¢used over a. smaller study area of el~vat~ Cs-137 radk>activity .deposit identified in the coarse grid survey. 4.1.2 Survey Components The FGi 1s discussed in detail in the Technical Work Plan, (D&M, 1994b). the componen~s l>f the FGI and the use of the data/tes4lts 1nelude:
- a. An ~valuati9n of soil samples from grid .blocks with a variety pf terrairi and ground cover to provide an indication of horizontal deposition of the Cs-137, to, provide confidence on the magnitude of variability.
- b. An evaluatfon of soil sample~ fr{}m grid blocks with a variety of teiraln an<l ground cover to provide an indication of the vertical profile of the Cs-137 below the surf~ce, t:O provide confidence on the magnitude of penetration beiow the surface.
WNYNSC Off-Site Radiation Investigation April 20, 1995
.c. A systematic measurement of Cs-137 gamma radiation at fixed points in the study area to provide a statistically valid detennination of soil activity averaged over 10 mx iO m areas. Such a survey requires the use .of an instrument with sensitivity only to* the gamma *radiation from Cs-1 ~7 and with its response correlated to activity concentration in the surface soil layer.
- d. A systematic measurement of gamma radiation at fixed points in the study area; to provide a statistically valid determination .of ~diatlon do~e rate averaged qver 10 m x IO m areas.
- e. A measuremen.t of Cs-137 gamma radiation d:uring a serpentine_ walkover ofareas between the point_s of tbe systematic measur~111ents, to provide confidence that no anomal_ous point sources of radioactive material concentration would be overlooked.
4.1.3 Description of the Study Area
*The location ofthe FGI study area with respect to the WNYNSC is shown on Figure 4-1.
The area, of ~pproximately 4.6 acres corresponds to the location of th~ highest concentration contours of Cs-137 measured off-site in the 1984 aerial survey, as verified by the Phase I Coarse Grid Survey. Figure 4"".2 provides a closeup of the FGI study area~ Represented on th_is fi,gure are property lines from the Town of Ashford Tax Map, radioactivity contours from the 1~84 . aerial survey, and the proposed study _area for the Phase II FGL WNYNSC Off-Site Radiation Investigation April 20, 1995 j
+
ll
'u E?<planation
... .... ..u
** a 3U Contours *from '1.984' flyovor *survey" I IU by E.G&~. .
+ .. Q
~fop ~ource 15 the Town of A2hlord Tal< Mop. Properly linn *coil olhor*
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*o 500 lbOO BOBERG ROAD 17 c
0 mo* Scaie in meters I 200 I 300 I Figure 4-2 Initial Boundary of fine Grid Area
@DAMES & MOORE Aprll 3, 199S
The eastern boundary oft.he FGI study area ori t:aX map properties 16, 23.2 and 15.1 coincides with the. western property line of the WNYNSC. The remaining eastern and western boundaries are set far enough from the ae:ri,al survey contours to provide
*ad~uate coverage to identify the uncertain locations of the contours. The northern and southern boundaries coincide with property lines from the Town of Ashford ~* map~
The initial boundaries of the FGI study area were drawn to coincide with property lines for convenience in establi.shing location in the field. If measuremen~s in the fo~ld incHcate that radioa,ctivity contours extend beyond the initial boundaries, Uie survey area boundaries w<;>uld be t~xtende4 to allow adequate t;:haracterization of the radio~ctivity deposition contours. The FGI study area was chos~n to coincide i,vjth the ar~ of highest radiation readings re:Ported by the 1984 aerial survey. It includes the ,;measurably elevated area" identified in the 1982 walkover performed as part *of the WVDP Environmental C::haractedzati()n Rep.Ort (see Section 2, above). Also, measurements in the Phase I Coarse Grid Survey study demonstrated that the highest soil concentrations of Cs..,137 were opserved in this area. Thus .this ':Phase of the investigation is addressing those areas containing the highest reported radioactivity in the previous surveys. The spa¢ing of the fine grjd .and the measurements positions were c!eveloped from recommendations in the U.S. me* document, '1Manu.al for Conducting Radiological Sur\reys in Support of License Termination, PRAFT (NUREG/CR-5849)" (NRC, 1992b). The grid origin was plac:d at a concrete benchmark located at a comer of the WN:YNSC bound~ ac;ljacent to Tax Map Prop_erty 16 (TM16). A sqqare 10-meter by 10-meter grid pattern was esrablisheo on the ground with compass and tape or transit, measured from baselines established by a licensed surveyor. Walkover surveys were conducted in eacb grid between lines that were 2.5 meters apart, and systematic location readings were obtained at eight positions per 10 m x 10 rii grid, as illustrateQ in Figure 4.;3, WNYNSC Off-Site Radiation Investigation 4-5 April 20, i995 I l
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'.J ADD!TIONAL SYSTEMATIC MEASUREMENT LOCATIONS 0 TO PROVIDE CLOSE-SPACED PATTERNS PA TH fQR SERPENTINE W;\LKOVE:R AT 2.~ METER INTERVAL Figure 4-3 Source: NUREG/CR-5849 Wcilkover Patterns and Systematic (NRC, 1992) Location.s in the Fine Grid
- DAMES & MOORE April 4, 1995
At each of the 8 positions, ~dings of dose rate (in microtem/hr) an4 gamma co:Unt .rate (correlated to pCi/g of Cs-137) were recorded. Also .fill!sfrated on Figure 4-3 is the labeling convention of _number (row) and letter (column) used in identifying the loeation of soil samples within a grid~ D~tails of .each component of the survey are discussed
.below.
The initial FGI study area consisted of a total of 1864 iOm x iOm grids (approximately 46.5 acres). Of this total, 210 grids (5.2 acres) were classified as 4isrurbed by human activity or use. On property TMl5 ..3 in the Nortbwest r~giQn, the study area encomp~$Sed 94 d°isturbed grids (2.3 ~cres) of active farmland with tilled field.s. Oi:i prop¢rty TM16 in me .South~t region, the study area included 34 disturbed .grids (0.8 acres) around~ residence area ofone house and two trailersimobile homes. .Also located
*on property TM16 were three are.as "totaling 82 disniroed grids (2.0 a,cre.s) µsed for the
-storage of derelict vehides,and bulk items. The disturbed areas are shown on Figure 4-4.
The other 1654 g;rips (4l.3 acres) Jn the initial sfudy ~ea were classifi.ed as undistµfbed by human use and consisted of native woodlands. A review ofhiStoricai maps and aerial photographs indicated that these areas had been undi~turbed since 1968. Most .of the central area contained thick .cover from deciduous leaf trees that left the area under the frees open With little undergrowth*. On property TM19 1n th.e SoJJthern region of the study area, there were 52 grids (1.3 acres) of evergreen trees with thick intetlockin~ br~ches. On propeny TM15.3 in the Northwesterri region, there were apprbx~mately 90 grids (2.2 acres) of thick undergrowth among. sparse trees. fj WNYNSC Off-S°ite Radiation Iµvestigation 4-7 April 20, 1995 I i L___
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4.1.4 Instrumentation Instruments used in the Phase II FGI are identified in Table 4-1. These are the same iri.struim~nts used in th~ Phase I Coarse Grid $urvey with ,one substitution. In the Phase II study, the HPIC was not used, because of its inability to distinguish between Cs-137 and other Jiatural radiation Contri,butions, as -piscussed in Section 3.. The Phase I Coarse Grid Survey indicated that concentrations of radioactivity were such that the e~tetnal radia.tions from Cs-1,37 woµld ~e m~ked by normal variations in ambient background radiation, unless instruments capable of re$pondin*g only to Cs-137 were used. An instniment capable of responding to just the Cs-137 gan1ma radiati9n ,is a single channel analyzer, the Eberline ESP-2 meter with the SPA..,3 &amma radiation detector. The SPA-3 contains a 2"x2" sodium iodide (N:aI) deteCto~ that provides a good sensitivity to Cs-137 gamma radiation, yet is rugged enough for fieid use. The SPA.:.3 detector produces an *electric pulse, proportional to the gamma radiation energy absorbed by the detecto_r. The ESP.-2 meter can be a(.ijusted (windowed) to respond only to the pulses correspondin15 to a specified energy range Qf gamma radiation. Smee, the energy of the Cs-137 gamma is w~ll establi~ed~ the :ESP~2 can be $1!t .~o respond to the pulse c;om~spondipg to the energy of Cs-137 while excluding other pulses of dissimilar energy. L
- I i J
- l WNYNSC Off-Site Radiation investigation 4-9 April 20, 1995
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Table 4-1 Radiological Instrumentation WNYNSC Off-Site Radiation.Investigation, Phase II Instrumentation Type of Measurement .Background 1 Detection Detector Meter Sensitivitv A. Field lnstrumenls Cs-137 gamma count rates Sodium iodide, 2" x 2
- scintillation crystal Field portable~ single channel analyzer 20-40 cpm 10 cpm Eberline Instruments,_ Model SPA-3 'Eberiine Instruments; Mooe! ESP-.2 Dose Rates Tissue-equivalent, organic scintillator * (same as detector) 3-5 ,tRem/hr l µRem/hr Bicron Corporation, Model MicroRem Surface scans* - Pancake GM Countrate meter 30 cpm 2 30 cprn 2 beta-gamma Ludlum *Measurements, Inc*., Model 44.:9 Ludlum Measurements, Inc., Model.3
.B. Lubarafory Instruments Gross c:i: /6 - soil Gas. proportional counter (same as detector) tcpm 5 pCi/g Isotopic Identification - soil Germanium detector; >> 55 cc Multichannel Analyzer NIA 0.05 pCi/g Gamma Spectroscopy Nuclear Data,. Model 6620 or 6700 Isotopic Identification - soil Silicon diode surface barrier Multichannel Analyzer NIA 0:02 pCi/g Alpha Spectroscopy Canberra Ind~. Inc. Model 7404 Canberra S l 00 Data Analysis System Notes Nominal val\Jes 2 Monitoring the audible signal WNYNSC Off-Site Radiation Investigation 4-10 April 20, 1995*
4.1..5 Data Validation Re-qufrements Data reported by supporting laboratories and fi,eld data were validated prior to indu{;ion into the Project files. Validation is accomplished through a review of the data collection procedures and by monitoring of QC sample results. Details of the validation process ate addressed in the Technical Work Plan and the Project Quality Assurance Pro~ram Plan, (D~M, 1994b).. 4.2 EVA.LUA,TION OF RAD.IOACTIVl'.l'Y YAIUATIQN IN SOIL 4.2.1 Purpose The FGI included ari ~valuation of r~dioactivity within a representative number of locations to . rJ
- L__,
better characterize how radioactive material was deposited over the study area. Soil samples were obtained from five undisturbed grid blocks to determine variation in uniformity in soil concentration across a 10 m x 10 m area. -Soil samples were obtained from five loGations in the"
.study ar~ in which the surface soii had beeT1 tjisturbed by hmn~ activities in the time since the depqsition had occurred. Background _locations for ~valuating the ~xtent and magnitude of radioactivity in the affected area were the same three locations used in the Phase I coarse grid survey.
1 J} 4.2.2 Locations Aerial pboto&raphs, maps and other h\storical records were reviewed to identify regions in the study area that had not been disturbed by human use since the deposition event in 1968. Five-areas were identified that spanii.ed the study area and pr~ented a variety Qf ground cover and terrain. The locations of these five Detailed Grids and other sampling locations in the FGI study area are shown 9ri Figure 4-4. Descriptions of the location~ are provid_ed iti Table 4-2. WNYNsc Off-Site R,adiatlon Investigation 4-11 April 2.0, 1995
Table ~2 Detailed Grids Used to .Evaluate H;orizontal and Vertical Deposition Variation and Sampling Sites in Disturbed Areas I Designation I Location I Description I DGill SON 60W undisturbed forest, modera.te canopy, slight slope, good drainage. little. ground coyer DG/12 150N lOOW undisturbed forest, moderate canopy, little slope, pqor drainage~ p.u.tnerous fems DGt/3 lOS lOE undisturbed forest adjacent .to driveway, moderate c~opy, little slope, good drainage, l)Urface leaves and twigs cleared by ailnual raking DG#4 220N 170W undisturbed forest, moderate canopy, moderate slope, good drainage,. little grotind cover DGl/5 490N 2}0W undisturbed open ar~, little canopy, adjacent to cleared powerline right-of-way; little slope, wet .. *1
- j. ground with gras~ .atii:I low bushes
- 1 ..
RH-1 40S 5CiE disturbed area Ill cli;:ated yard adjacent ~o permanent reSidence house and mechanics shop. Sampled near tree on south side of house
- RH-2 20S SOE disturbed area in cl~red yard adjacent to permanent residence h9use and mechanii:s shop; sa~pled near dtiveV{aY, in north side of hou~
RT-1 10N20W disrurbed area, in cleared and leveled yard adjacent to house trailer; sampled near trailer on ea.st side yard BS-1 ON40W disturbed are.a. in cleared and leveled site for future building; sampled approximately 20 m west of trailer OF-1 350N 400W disturbed area in tilled farmland; sampled in open field approximately 25 m from treelihe. J J WNYNSC Off-Site Radiation Investigation 4-12 April 20, 1995
4.2.3 Methods Soll samples were collected at the locations in the study .area *using the sampling procedure in Field Procedure FP-8, Surface Soil Sampling, incluc;led in th¢ Technical Work Plan, (D&!,M, 1994). At each location, soil plu.gs, 2 inch (5 cm) in diameter, were collected at layers of 0-6 .inclles (Q,.15 Pm), :2-lld 6-12 inch~ (l5.,-3Q cm), using an _AMS brand Soil Core Sampler witt1 removable aluminum finer. 'The initial soil plug was divided into samplr;s representing depths of0-2 inches (0-.5 cni), 2-4 inches (5-10 CIT1) ~d 4-6 in:ches (iQ-15 cm), and these* samples were subniitted to the .contract laboratory f()r analysis of moisture content and cohcentr~tion of Cs-137. In undiSturbed areas the 6* 12 foches sample plug was retained in the aluminum liner* to main.tain layer -integrity, to be sU,bdivided into two~inch layers and ana.1,yzed for Cs-137 ortly if the 4-6 inch sample from the surface piug showed Cs-137*activity ~reater than 50% of the
.surf~ce coptentration~ Fl)r samples ~n di~furbed areas th,e. 6:-12 inc~es plug wa.s divi.ded iritQ samples representing the two-inch thick layers and submitted to the laboratory for analysis.
4.2.4 Data Quality Assurance Fifty-eight additional samples, r;omposed of 30 field duplicates ?Jld 28 labor~tory split$ repres~ntjng 30 % of the 193 primary samples, were submitted to the contr~ct l~boratory and to the NYSDOH, which is an EPA. c.ertifie4 analytiG?l laboratory,, Samples w~re provided to the NYSDEC on. request. The NYSDEC W3$ .present on the ~ite dl,lril)g th.e sampling ajid measurements at DGtll, and :field split samples. were *e~cjhanged. A corriparisori of *the ;re$ults from quality B;ssurance analyses of spiit s~mplf(S are compiled tµid provided as a table in the Technical Data Ann~x.
- a. Intra-Laboratory Evaluation. The contract l;,iboratory received 42 QA saQ'lples, composed of 14 duplicate samples split by field personnel an<l 28 double volume samples for the laboratory to split. Each matched sample result was compared to +he initial analysis to determine tjle Relative Percent Difference (Ri>D) of the replicate result to the initial result.
WNYNSC Off-Site Radiation Investigation 4-13 April 20, 1995
- For the 14 field duplicates, fol}r sa~ples were r~porled with. RPD ~ 20 %. Each of these samples .contained less than 0.5 pCi/g, which is typical of the ambient level in soil observed in background samples.
- For the 28 laboratory duplicates, seven samples were reported with RPD > 20%. Four of the seven samples contained less than 0.9 pCi/g, which is typical of the ambient level in soil observed in background samples. Three sampleS reported with RP:b ~ 20 %
r~mained unexplained.
- b. Inter-Laboratory Evaluation. Sixteen samples were spiit in the field with h~f of the volume sent to the contract laboratory and the other half sent to the NYSDOH laboratory. Six of ten samples with activity greater than 2 pCi/g had a reiative percent difference greater than 20%.
For each matched sampie pair, the NYSDOH laboratory analysis result w43 c9mpared to the cont.f?-ct laboratory analysis test.jlt using linear regression -analysis. A graph of the correlation is provided in the Technical Data Annex.. This comparison indicated a strong linear correlation (R"2 = 0.97) between the two laboratory results. The slope coefficient fo.r the regression was .0.76, indicating that the NYSDOH reported results were systematically bias~d at 24% less than the* result reported by the contract laboratory. 4.2.5 Results and Discussion A comprehensive listing of soil analysis results is provided in the. Technical Data Annex included with this Report. An extract of the relevant Cs-137 concentraticm values by layer is* provided 1.n Table 4~3. A discussion of the results as they relate to the interpretation of horizontal and vertical distribution is provided in th~ following paragraphs; The contract laboratory an.alysis method .assured that results were *reported with an uncertainty (95 % confidence interval) of +/- 10% of the Cs-137 activity in the soil. Thus variations between samples of greater than 10 % are interpreted as a v~atidri in the distribution of the Cs-137 in
- the* soil.
WNYNSC Off-Site Radiation Investigation 4-14 April 20, 1995
"l l I Table ~3 Soil Activi~y in Detailed Grids 'l Cs-131 Activity. (pCilg) Activity ratio of layer A~tivity Ratio or Location layer depth % qf sµrface 111yer J DGlf *~grid 0-2* 2-4" 4-6" ~-4" 4-6"
% of total fu o~i" 1-4" o-6
- 0-2"' 4-6"
- .r Bkg . ~ YfEVAL 0.54 0.47 0.?8 l.00 87 52 42 36 22 Bkg SPRVL 0.50 o:s1 0.28 roo 102 56 39 39 22 Bicg RT246 1..0 ().92 .0.78 ioo 92 78 37 34 29 1 3E 1.5 0.22 0.06 100 14 4 .85 12 3
.1 3F 44 8:5 0.96 100 19 2 82 16 2 1 ~G 38 13 2.2 100 33 6 72 24 4 J 5]3 15 0.94. 0.15 1.00 6 ~ 93 6 1
'l .Sb 2-5 4.i 0.36 100 16 l 85 14 1 i SF 14 s.o 2.5 100 $7 18 S7 33 10
.,I 1 sa 38 12 LS 100 .31 s 74 2.3 3 1 51 25 3.6 0.60 100 14 2 .86 i2 2 J 1 7F 28. 20 3 ..8 109 j'I 14 54 3~ 7 lF 7.0 .S.4 100 7.8 ts Si 40 9
- i 2 2
3F 6.8 4.9 1.3 0.58' 100 72 8 55 40 5 .. J 2 SB 8.2 4.6 . 0.20 100 s7 2 63 3.6 1 2 50 7.7 5.3 0.39 100 .69 5 57 40 3 2 SF l? 8.7 2.0 100 73 16 53 38 9 2 SH 16 7.1 0.46 100 44 3 68 30 2 2 51 11 3.8 0.:?.8 100 35 2 '73 25 2 2 7F 14 4.8 i.6 100 35 12 68 24 8
- 1 2 9F 5.7 3.9 ().58 I.00 6~. 10. .56 38 6
\
'" 3 IF 1.2 1.9 0.21 ioo 26 ~ 78 20 2 3 3F 11 s.o 1.0 100 46 10 64 30 6
- 1 3 SB 20 9.0 l.3 100 . 45 6 66 30 4 J 3 SD 16 12 3.4 100 72 21 52 37 11 3 .SF 16 5.5 0.68 100 35 4 72 25 3 3 SH 8.6 3.9
. 1.1 ioo 46 13 63 29 8 3 5J 7.9 4.3 2.2 1()0 55 .28 SS 30 15 3 7F 16 9.2 1.7 100 58 10 59 3S 6 3 9F 14 5.6 1. l lQO 41 8 67 28 5 l.
- I
\ WNYNSC Off-Site Radiation Investigation 4-15 April 20, 1995 j
I
1 I ~- j Table 43 Soil Activity in Detailed Grids
*-i (continued) l
' ..I Cs-137 Activity (pCi/g) Activity ratio of layer Activity Ratio of Location layer depth % of surface layer DG# in grid % of to~! in 0-6
- 0-2" 2-4* 4-6" 0-2" 2-4" 4-6" 0-2" 2-4" 4~*
.i ] 4 3F 12 8.0 0.58 100 67 5 58 39 3 4 SB 10 2.0 0.13 100 20 1 82 17 l 4 SD lS 6.6 0.95 100 44 6 67 29 4
*1 4 $f ~9 2.6 0.47 100 14 2 86 12 2 4 5H 22 3.1 Q.84 100 14 *4 85 12 3 1
u r* 4 SJ 25' 6.8 0.38 100 27 2 78 21 1 4 7F 21 7.2 i.o 100 34 5 72 25 3 4 81 18 1.6 0.14 100 9 1 91 8. 1 4 9F 17 2.8 .0.6~ 100 16 4 83 14 3 s 3F 1.2 1.6 Lo 100 133 83 32 42 26 ( 5 SD 2.5 0.29 0.060 100 12 2 88 10 2 5 SF 4.1 0.70 0.08S 100 17 2 84 14 2 5 . SH 2.1 0.54 0.097 100 26 5 77 20 3 s 7F 3.6 0.16 0.038 100 4 1 95 4 l l j WNYNSC Off-Site Radiation Investigation 4-16 April 20, 1995
- a. Vertical Profile Distribution. For comparison of profiles* with widely varying magnitudes, the ~ctivity in each two-inch layer has bee,n nortna,J.ized in two ways~ The midc!le columns of Table 4-3 express theactivity in each layer as a percentage of the activity in the 0-2" layer. The right hand columns present the activity in each layer as a percentage of the total activity observ.ed in the 0"6" colurtm of soil.
The analysis of soil activity by two-inch la,yers indicated that.90% of tile activity in the 0-6 inch soil layer was confined within the top four inches of soil for 38 of 4i samples with activity greater than 2 pCl/g. For ail five grid~, the average percent activity in the 0-2'1 layer was 70.3% + 27.8% 1 ~d for the 2-4" layer was 24.8% +/- 41.'6%. The activity in D0#2 snowed .I , ~ a sUgh~ shift.in the ratio with 605% +/-* t5.3 % in the Q,.2" lay¢r and 34.5 %+ 12. 7% in the 2-
- J 4" layer, The activity appeared to be associated with the organi,c*~umu
- ; layer *on the ground sµrface~ At DG#2 where this layer was four to six inches or more thick, there was a .higher percentage of activity ii1 the deeper layers. At most locations the hun;ms-clay iptei:face was obser\ied in Jhe*
2-4" layer sample; In one instan'Ce, at location 3E in DG#l, the humus layer was less than 0.5" thi.ck, resulting .in a 0-2 sc;mple with very little activity.
- b. Horizontal Variation on a smail scale. Statistics ,summarizing the horizontal variation within each Detailed Grid are provided in. Table 4"'.4. Jn all cases the peak concentration of Cs-137 :in the grid was less than twi~e the average value. T,his variation appeared to be a. pert~bation due to focal surface *effects, e.g.. driplines from trees and. limited variations 'in thickness of the humus, rather than isolated particl~~ Of higher ~tivify.
No hot spots of anqmalous high activity Were obSerV'ed in the sam:ple positions; one posjtion that was unusually low was observed at position E3 in DG#l. This sample position was in a location where th~ underlying clay was vety close to the surfac~, the humus fayer was less than 0,5" thick. 1 Uncertaintie8 .are reported as +/- 1.96 times the standard deviation of the measured average value, which defin~ the 95% confidence interval on the acfual. mean of the observed populatio1_1 of m_eas,ured values. WNYNSC Off-Site Radiation Investigation 4-17 April 20, .1995
** 1 . I.
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Table 4-4 Averages and Rati()s for Cs-137 Activity in 0-2 11 Surface Soil Layer Di.i:;tance Number G.rid Avera,ge Activity Activity Designation from of soil Cs-137 Activity Ratio Ratfo main .stack samples (pCi/g)2 .Pea1davc;:rage peakllow Backgrounq 3 0.68 +/- 0.55 1.5 2.0 DG#l i.s km 9 25.4 +/- 26.5 1.7 3.1 1 Cl DG#2 1.6 'km 9 9.8 +/- 7.1 1.6 2.8
- j DG#3 1.4 km 9 12.8 +/- 8.6 1.6 2.8 DG/14 1.7 *1qn 9 17.7 +/- 9A 1.4
.' 2,5 DG#5 2.0km 5 2.7 +/- 2.4 1.5 3.4 Average i.6 2.9 Note 1 Disregarding anomalous low value at position 3E.
n u 2 Uncertainties reported as 1.96 times the standard devi!ltion (95 % confid.ence interval). The peak/low activity ratio in each grid inditates that horizontill variation is great enough that a single sampling of a grid might not produce ~ value that is representative of the actual
.concentration .
.: l
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- c. Horizontal variation on a large scale. The results in Table 4-4 indicate there 1s no discernable trend of average activity with distance from the ;E>roc~ss Building main stack.
Activity at DG#2 in the center of the study area is a relative low *Concentration on the central raciial of the deposition at 1.6 km from the.stack. Both the 1982 grpund survey (WVDP, 1982) and the 1984 aerial survey (EG&G, 1991) showed si*mnar relativeiy lower rad!ation areas in the same region of the central radial. Activity app~s to fall off rapidly at distan_ce away from the central radial, as shown by the decreased activity at PG#5, approximately 90 m off the centerline. This again is comparable to the-'1984 aerial survey Cs-137 contours that showed the elevated region (C contour) was l~s than 200 m wide, perpendicular to the central radial . .1 I
\;
WNYNSC Off-Site Radiation Inv~stigation 4-18 April 20, 1995
- d. Radioactivity in disturbed areas. Th~ concentrations of Cs-J37 observed in the soil samples from disturbed areas are summarized in Table 4'."5. The analysis indicates that the use of the land and disruption of the surface" redistributes .the radioactivity so that it oo longer resides just on the surface as in the undisturbed woods .. As .a result of.disturbance of the surface layer, the Cs-137 is either rempved .(as cit BS-1), covered t>y clean soil (as at RT-l) or blended throligh the disturbed layer (as (!.t RH-2).
4.3 COAA:ELATION OF INSTRUMENT .RESPONSE TO SOIL RAI)IOACTMT.Y 4.3~1 Purpose Tlle ESP-2 single channel ajlalyzer provides a response proportional to the energy and *nunibet of gamma. radiations detected, The interprc;:tation of the instrument response relies on a knowledge of the geometrical distribution of the radjation so'1rte being m~stued. Calibration laboratories in the U.S. provide instrument calibration with a point sourc~ of radiation and do not have an extendeq geometry soµrce availabie.. For the ;phase lI study! in order to infer ground concentratio_n from measur~ments near the ground surface, the instrument respqnse w.as correlated in the neki lo known ground concentrations of Cs-137. 4.3.2 Methods Instrument correl~tion was a,ccomplished through a proi:edure of establishi~g the response of an instrument (the primary instrument) to known concentrations of soil activity, then comparing the other instrument's response (the secondary instrument) to that of the primary instrument. The 0 J?roc~ure i~ detaile4 i_n the TechniCat Work Plan, (D&M, 1994b). Brjefly~ the correlation procedure involves: WNYNSC Off~Sit~ R;!tdiation In~e5tigation 4-19 April 20, 1995
Table 4-5 Cs-137 Activity in Disturbed Soils Grid Location Location Sample Depth Activity Cs-:137 Description (in) (pCi/g) 40S SOE Residence Yard 0-2, 6.3 +/- q.6 adjacent to tree In cleared yard 2-4 6.5 +/- 0.7 Code RH-1 area 4-6 2.0 +/- o.2. 6-8 2.2 +/- 0.2 8-10 0.47 +/- 0.05 10-12 0.50 +/- 0.05_
'.Zos SOE Residence* Yard 0-2 1.8 +/- 0.2 adjacent to hquse 2-4 1.1 +/- 0.1 in cleared and Code RH,-2 leveled yard area 4-6 1.4 +/- 0.1 6-8 1.8 +/- 0.2 8-10 2.1 +/- 0..2 10-12 2.3 +/- 0.2 ION 1.0W Trailer Yard 0-2 0.24 +/- o.04 cleared and 2-4 0.041 +/- 0.027 leveled area Code RT-1 with residence 4-6 0.034 +/- 0.()20 trailer in place 6-8 0.077 +/- 0.031 8-:10 1.1 +/- 0.1 10-12 2.1 +/- 0.2 ON4QW Building Site 0-2 0.087 +/- O.Q29 leveled op.en a~ 2-4 '0.006 +/- 0.024 for future building r1 Code BS-1 4-6 -0.009 +/- Q.027 i l
"*-~' . .6-8 0.004 +/- 0.021 s~10 0.006 +/- 0.022 10:12 -{).012 +/- 0.-.018 3.SON 400W Open Field 0-6 1.6 +/- 0.2 ,: 1 tilled farmland . I
- l
- .: l Code OF-1
. 6-12 12-14 0.89 .+/- 0.09 0.38 +/- 0.<;34 14-16 0.007 +/- .0~022 16-18 0.59 +/- 0.06
,, *1
.l
\VNYNSC Off-Site Radiation Investigation 4-20 April 20, 1995
STEP 1 A recently recalibrated ESP-2 m¢ter with SPA-~ detector (the primary instnunent) was l,lsed to obtain measurements over soil positions prior to sampling. Linear regression ancilysis was then used to establish a correlation between instrument response . ancl the acti.v.ity concentration in the 0-2 soil layer reported by the laboratory. STEP 2 A reference range for instrument response comparison was set up at DG#l .and the primary 1nstru:rnent was used to infer th~ ground activity concentration at U
*positions .in the grio.
STEP 3 When another meter (termed a s~conpary instnirnent) was readied for use in the survey, it was ~ert to ~he reference response rilni?;e CU1d measurements of gamP"ia
.tad,iation were obt41I1.ed at the 11 positions.
STEP 4 Linear iegressioJ1 analysis was theri used to e~tablish a correlation between the response of the *secondary .instrument and the activity concentration in the Q.,.2" soil layer inferred from the response of the primary instrument at th~ r¢spective location. 4.3.3 Results and Discussion The correlation of the primary instrument was performed by measurements <,1.t DG#3 on itily 14, 1994 and at DG#4 qn August 15, 1994. The data for the primary instrument correlation and stib$equent secondary correlatipns is in the Te<:hnical Dab). Ann~x. A graph illustrating the corr¢lation relationship for th~ priplacy instnJment is proyided in Figure 4-5. n ! i Li WNYNSC 0ff-Site Radiation Investigation 4-21 April 20, 1995
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O* I O 1-1-i-rrrrrr*r1-rrrr1:-r-1-,-,:-rr-r-t-r1..,-, . *I I I _____! 1*r 11 ~,~,~,---*,- 1 50 75 100 125 150 175 200 225 250 275 300 Esr.:2 reading [counls/30 sec] SN 070 I ,.detector at 5 cm,.OG113 and DGfM Figure 4-5, lnslrumanl Correlation 11 !l_~~~~~~~~~~~~~~~~~~~~~~---~~~~~~~~~~~~_J~~~~-=l>=A~=tE=*S==&=*=M=O=n=~R=~*LF_o_br_ua_r~y-1_s.~19_9~5
Using ")?eatson's .produc~ moment method, analysis indicates that a statistically significant correlation (false positive probability, ci = 0.01) exists between the counts measured by the primary instrument and the Cs-137 activity in* the 0-2'! soil layer. Linear regression analysis determined th.at the correlation equation was: ActiVicy = Counts
- 0.090 - 0.39 [R"'2 = 0.74]
(pCi/g) (in 30 s~) where 0.990 is the slQpe coeffici<mt in units of (pCi/g) per (counts in 30 seeonds) (iJ'lq - Q.~9 is :the intercept coejji<;ient in units of (pCi/g). Using this cortelatic:>n equation, one can predict the Cs-137 activity in the 0--2" soil fayer with a value of counts observed in a *30'."'second measurement at the.ground surface . The correlation coefficiem [R~2J is a measure of the prediction strength of the correlation. A value Of R-"2 = 1.0 describes a pert'eGt correlation while a value of R"2 == 0 indicates that there is no correlation between the paired data of observed counts and soil activity. The primary instrument.correlation in DG#3 and DG#4 resuited in a correlation coefficient of R'~2 = 0. 74. This .is interpreted to mean that 74 % of the diff¢rence between the observe9 and predicted Cs-137 concentration in the 0-2" soil layer is explained by tne regression equaµon. The unexplained differeri<;e could be due to such factors- as depth .Of the humu:s-clay interface and activ1ty in the. layer(s) below the 0-2'.' lay~r. The 95 % confidence interval indicated on the graph in Fig;ure 4.:.5 shows the range of the unc~rtainty in the correlation due tcf the unexplained difference, due ~o ranoo}TI decay of tbe Cs-137, and due to random electronic signals in the detector. The uncertainty in the activity interpreted from the counts ranges from + 1. 7 pCi/g near the center of the range, {at 15 pCi/g) I'} to +/- 4.1 pCi/g near the extremes (at 5 and 25 pCi/g). For inferreo activities above 15 pCi/g, _j the 95% confidence inte!Val is approximately+/- 11-163 of the activity. As the total counts and the iriferred activity get smaller, the uncertainty as a perc*ent of the activity grows larger. For smW,l activity con~ntratlons, (e.g. 5 +/- 4 pCi/g), the uncertainty tan grow to+/-. 80%, or more. WNYNSC Off-Site Radiation Investigation 4-23 April 20, 1995
'l I
I
' j Thus, the regression/correlation equation iS more precise at evaluating activities above 12-15 pCi/g~ At lower activities, the correlation ~ verify tha.t the activity is low, but _the preqicted value could have a large confidence interval or uncertainty.
Five ESP-2 instruments were used on the project during the fieid s.urvey. The instruments were correlated before the initial use in the field, and the correiatlon remained assigned to the instrument so. long as operational and stability checks performed before use Were acceptable. When an instrument failed in the field, upon receipt from repair and calibration support, the instrument was correla~ again prior to use in the field survey-. Table 4-6 summarizes. the correlation factors for secondary instruments used during the survey. Table 4-6 Correlation Factors for Se~ondary Instruments During Fine Grid Survey Instrument Slope Intercept Regression Oat~ Serial Number Coefficie~t 1 Coefficient 1 Coefficient 2 02~Sep-94 0701 3 0.0931 +1.335 0.98 14-Sep-~4 0701 :3 0.0907 -0.388 LOO 14-Sep-94 0773 0.178 -4.89 0.94 28-Sep-94 0911 0.0762 +3.19 0.80 03-0ct-94 0701 0.0,836 +2A4 0.97 04-0ct-94 0764 0.0755 +3.05 0.94 04-0.ct~94 1674 0.0649 +2.'71 0.94 11-0ct-94 0701 O.QQ28 +4.27 0.94 u 12-0ct-94 0911 0.0367 +2.54 o.95 26-0ct-94 0764 0.0782 +2.29 ().95 26-0ct-94 0773 0.142 -0.55 o.~4
- 26-0ct-94 0911 0.150 +0.63 0.93 14-Mar-95 0701 0.173 +2.03 0.93 NOTE l Linear Regression Equation: Activity (pCi/g) = slope
- couf!ts in 30 sec + Intercept 2 Significant linear correlation at a=0.01 level. R"2 near LO indicates a strong correlation while
_R"2 near 0.0 indicates littie or no correl;ltion.
-3 Primary instrument cor,related to itself.
. I WNYNSC Off-Site Radiation Investigation 4-24 April 20, 1995
.~ i 4.3.4 .Correlation Verification
.l The validity of the instrument correlation of counts to soil activicy was verified by comparing the activity inferred. from surface surveys to soil sampl~s taken at intervals during the survey.
- Ta.ble 4:-7 presents a comparison of (he activi!)' in seven grids, de~ermined by the two methods.
As expected from the derivation *of the correlation and the discussion above, the correspondertce l between the two methods is better for high¢r activity levels; the irtsthime_nt correlation i~ much ,} less precise at lower activity levels where the counts are low with respect -to random electronic noise signals in the det~tor. At lower levels the instrument is overestimating the actual activity present. Table 4-.7 Comparison of Soil Activity (pCi/g of Cs-131 in 0-2" Layer) by Correl~ted Instrument Measur.ernent *and Laboratory Analys_is Average Grid AetiVity Average *Grid Activity Sample Loc_ation Inferred .by Me3$Ured PY Designation in Grid Correlated Iristrument 1 LabOratory Analysis 2
,DG#l 80~_60W 25.2 +/- lL4 25.4 +/- 26.5
'DG#2 .ISON lOOW 9.8 +/--2.5 9.8 +/- 7.1 DG#3 lOS io:g 19.1.+/-. ~.o i2.8 +/- 8.6 DG/14 220& i1ow 21.7 +/- 7.8 17.7 ~ 9.4 DG#S 490N 270W 8.8 +/- 1.6 .2.7 +/- 2.4~
OFifl 350N 400W 6.0. +/- 3.3 1.6 +/-_ 0.2 4 SEDi 370N 1.70W 7.1 +/- 1.6 2.7 +/-_ 0.,3. 4 Notes 1 Average and 95 % confidence interval of the gnd average based on measurements of counts in ~b seco.nds from.eight positions in the grid. 2 Average lll1d 95% confidence interval of the grid average, based .oh iabotatl)ry analysis of soil samples from nine positions in the grid, except as noted. 3 Based .on _soil samples from 5 positions in the grid. 4 Based on soil samples from a single position in the grid .
.1 l
J WNYNSC Off-Site Radia,tfon Investigation 4-25 April 20, 1995
4.4 SYSTEMATIC SURFACE SURVEY FOR CS-137 ACTIVITY l 4.4.1 Purpose
- I The systematic surv~y of Cs-137 count rate is used to provide a statistically valid detern'lination of average soil radioactivity concentration. Using tpe correlation procedure discussed above, ft this measurement of gamma radiation determines the activity concentration of Cs-137 (pCi/g)
L ) I in the ()..,2" surlac_e layer of soil. This measurement is analogous to the measurement in the 1984 aerial survey contours shown in Figures 4-1 and 4-2, except 'that the aerial sur¥ey measured the Cs-137 gamma rays at an altitude of 46 m and reported the results riot as soil concentration but
?S cou_nts per second (proportional to cs-137 gammas per s~ond). 2 In this survey, a cortela.ted instrum~nt was used ~o obtain gamma measurements a:t the ground surface to better quantify and
_more narrowly locate the Cs-137 material when present. 4.4.2 Methods Using the field portable single channel analyzer arid NaI detector (ESP-2 witl:l SPA-3 detector), windowed to the Cs;..137 response region, the field surveyor measured the gamma radiation emitted from the ground surface at eight positions of e.ach 10 m x 10 m grid, as shown in Figure r 4-3. In the timed accumul_ation mode, the ESP-2 allows logging of ~he hJstrument reading to
\
a data memory. Upqn completion of grid $urveys, the Slirveyor down-loaded the data from the instrurnent memory to a computer-readable data file. The details on use of the instrument and data logging is provided in th~ Technjcal Work Plan. In addition to the electronic file, the surveyor mzjntained a written log in which the grid locati,on and the first instrurrtent reading in each grid were recorded . '._J The timed-accumulation measurements (in counts per 30 seconds) were correlated to Cs-137 activity concentration in pCi/g using the correlation equation specific to the instrument used in the survey. The average soil concentration in each 10 m x 10 m grid was determined by 2
- The aerial su_rvey report did provide several multi-step conversions from counts per second to Cs"13_7 soil concentrations based on several assumptions of the ground distribution (EG&G, 1991).
-l WNYNSC Off-Site Radiation Investigation 4-26 April 20, 1995
-l
'j
averaging the ~ight correlated values from readings in the grid. The 95 % confidence level statistical tests contained in Chapter 8, NUREG/CR-5849 (NRC, 1992b) were also performed. The initial boundaries of the FGI study area were drawn from the 1984 Cs-137 activity contours from the aerial survey (EG&G, 199i) and e"isting property ijn~. The actual boundary of ground surveyed was determined by the response pf the correlated instrumen:ts. The survey was performed along the central radial of the deposition and continued outward in blocks of 25 10 m x 10 ni ,gri~s. The survey was contirtu~ beyond tl}.e area of significant Cs-137 detection until the instrument co.unts entered the level of minimum response, Le. tbe total counts observed were 11 L. .,l'
- so low that the u.ncertai~ty in .the inferred '!,Ctiyity was as large ~s the inferred a.ctjvity.
Contours for rep:r:~sentjng th~ concentration levels ii) figures were generated by importing data fl fil~s with ~rid coordinates <;ind activity concentration into the surface mapping program, U SURFER3
- In SQRFER, the minimum curvature method; a method widely osed in .earth sciencf!S applications, *was used to develop srrioothed contours that were representative of the fluctuating grid average data.
4.4.3 Data Quality Instruments were calibrated and windows peaked to the gamma radiation from a Cs-137 source by .external ¢alibration laboratories, 4 Instrµrrient operation and stability were verified with measurements of a reference source of Cs'-137 and the ambient background in Sprin~;ville, NY. Stability checkS were performed before *and after leaving the field, when brea.king for lune)) and at the end of the day. These readings were recorded* in field log sheets. Control chart plots of these readfngs ar~ filed .in the Tec.hnic,al Data Annex. To verify measurement reproducibi11ty arid instrument stability in .the field, upon completion of a blqck .of 2:5 10 m x 10 m.grids, the surveyor re5urveyed. the i~iti~ grid of the block. This 3 SURFER for Windows, Ver 5.02, 1994. Golden Software, Inc., Goiden, CO. 4 Dames & Moore instruments were calibrated by GTS Instrument .Services, Pittsburgh, PA. Instruments supplied by the wVnP were calibra~ l;ly WVNS Co., Inc:.
]
iJ WNYNSC Off-Site Radiation Investigation
- 4-27 April 20, 1995
- . I result~ in a qualfty resur\Tey of 62 grids (4.. l% of the 1:503 grids with accepted survey data).
- I
- ' The downloaded data file was reviewed to compare the initial and resurvey data by calculating the teia,tive percent *difference. Data from six stability resurveys resulted in rejecJion of the data, necessitating. a resurvey of the block of 25 grids. A listing of the initi~ and resurveyed data for the grids is listed in the Technical Data Annex.
After the field portion of the investigation was completed, all field data files were validated before their inClusion into the a~cepted data set. Validation procedures are in the Technical Work Plan. The ess~ntial part of the validation procedure was a review of the .electronic file with the field log of the initial readin~ in each grid, to ensure that data were assigned to the
'. 1 appropriate grid in the FGI study area.
J 4.4.4 Results .and Discussion The systematic Cs*:.l,37 soil. survey included 1564 10 Iil x 1Qm grids 09 acres) of the 1864 grids (46.5 acres) in the initial survey area based on the aerial survey <Utd prqperty boundaries. Areas t~*~ I I i __.l containing 378 grids (9.4 aces) on the fringe of the initial boundary were not surveyed When the instrument response was so low that the Cs-137 .counts were below the minimum response level of the instrqme.rit, These ar~s included: 54 grids on the southern edge
- 71 grids along the southwest.em edge in the south
- 253 grids iii the northeast ri;:gion of the study area Along the southwestern edge, 78 grids. (1.9 acres) were added to the survey area to ensure that the edge of the significant Cs-137 was d~fined.
Among the 1564 grids comprising the final su.rvey area, 204 grids (5. I acres) were classified as disturbed by human use. The disturbed grids included tilled fields; driveways, crushed stone parking area.s, buildings, ponds and several cleared anq leveled areas for storage of derelict vehicles and other bulk items. Of the disturbed areas, 62 grids (1.5 acres) could not be WNYNSC Off-Site Radiation Investigation 4-28 April 20, 1995
surveyed because the ground surface was not accessible, i._e. building foundations, derelict vehicles covered the gro1.md. All 1360 undisturbed _grids and the 142 accessible disturbed grids in the. study area were evatuated, providing a to_tal of .1502 grids (96 % of 15Q4 grids) with eigbt surface readings of Cs-137 gamma radiation each. The average Cs-137 concentrations, based on the instrilment survey, are summarized in Figur:e 4~6, where the grid averages are portrayed on a map of the study area. _On this figure, the values have be¢n rounded to irit~ger values to facilitate_ display. Tables of ,the average Cs-137 concentration in the soil and the standard deviation for e_ach of the 10 m x 10 m grids are provided in the Te~hnical Data An~ex. Contours of the average Cs-137 concentration in thee 0:-2 inch surfa~e layer b~sed ,on the instrument teadin~s ate. shown irt Figure 4-7. Va1ues of indicated Cs-137 c9nc;entratiort below approxirnately 10 pCi/g ar~ below the level of minimum instrument response and the 95 % confidence interval is a large percentage of' the indicated value. For the:se values, the actual concentration is as low or fower than the indicated value, but its precise value is uncertain. The average Cs-137 concentrations in soil inferred fro.m the correlateci fostnirnent ranged from 3.3 + 1..4 pCVg {in a disturl?ed i;rea grid) to 34;7 +/- 8.2 pCi/g (in a grid fo the undistilrbeq woods). The Cs-137 d~tec~ble _above the minimum instrument resp0nse was loca,lized al9n& the central radial, out to appr9ximaJely 600 m from the concrete monument ~d SO meters to *either side. This area encompassed apprQximately 15 acz:es on the four properties sµrveyed (TM16, TM23.2 TM15.1 and TM15.~). In the disturbed areas, the ihstrument*respcfase was uniformly at the minimµm response level, indigiting the absence of significant surface-deposited Cs-137. Only wben disturb~ areas included landscaping around existing trees was the Cs-137 detectable above backgrotjnd response. In the undisturbed areas, the instrument response easily l<>Gated areas of significant Cs-137 activity. In accordance with the instrument correlation objective, the measurements in WNYNSC Off-Site Radiation Investigation 4-29 April 20, 1995 '-1
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Not e: Values below opp1 r oximotely 10 pCi/g are at the minimum response level of the survey instrument, and the 95% confidence interval is o large percentage of the indicated value. Figure 4-6 fine Grid Area With Average Grid Activity Concentration ( pCI/ g) SCALE: Grid cells are 1 Om X lOm
l 500 J 450 350 *c 0.. lfl
;:J.
() 0 1* 0 (/') 0
~
250 z z
@ 3:
200 0 150 EXPLANATION 35 pCl/g 0 20 pCl/9 15 pCI/; 10 pCI/; 0 pCl/9 line of surveyed area Figure 4- 7 Contours of Average Cs-137 Concentrations (pCi/ g) SCALE: Grid cells are 50m X 50m fllDAMES & MOORE Aprll 4, 1995
'\
areas of less significant deposition, the instrument response verified the lower levels of activity i I
! with less precision on the final value.
4.5 WALKOVER SURFACE SCANNJNG
- l
- I
( .1 4..5.1 .Purpose r1 Li The walkover survey .in a serpentine pathway provides an assurance that anomalous point sources of ~dioactive material i::oncentration will not be overloolce<;I between Jhe discrete measurement positions of the systematic 5µrface measurements. The w~kover survey is an evaluation of the n ~miforinity of radiation .emissions in a local region and whether ariy "hotspots" are present. As L.I such, the absolute magnitude of counts is not as important as the relative fluctuation of counts with position. 4.5.2 Methods The walkover survey was performed with the field portable single channel analyzer (ESP-2) and NaI gamma detector, windowed to the Cs-137 . response region. .For each 10 m x* 10 m grid, the field surveyor traversed pathways situated at 2.5 m intervals, so that each grid is divided into 2.5 m x lO .m qu~ers. The surveyor walks at a deliberate/slow pace; moving the gamma
--j detector back-and-forth in the 2.5 n:i wide sector within 5 cm of tile ground surface.
In the count rate mode, the ESP-2 performs "peak count trappfog," logging of the maximum instrument reading during an interval to a data memory for subsequent recall and downloading.
'.J The ESP-2 reading is calculated every. 0.5 seconds in the rate rnode, so that 120 readings per minute are generated by the instrument. At the end of each 25 m1 quarter-grid survey in this mode, the surveyor enters the maximum observed reading -into the ESP-2 stored memory. In addition to the electronic file, the surveyor maintained a written log in which the grid location and first peak reading in each grid were recorded. Upon completion of 25 grids, the surveyor re-surveyed an initial grid as a measure of instrument stability and survey reproducibility. At the i i'
,. l WNYNSC Off-S~te Radiation Investigation 4-32 . April 20, 1995
end of a 15urvey, the surveyor downlqaded the* stored peak t~dings (usually 26 grids with 1 reading per each quarter grid) from the instrument memory foto. a computer-readable data file. 4.5~3 Data Quality !] Instruments were calibrated to the gamma radiation from a Cs-137 source by an external calibration laboratory .-s Instrument operation and stability were verified with a measurement of ambient background radiation and a reference source of Cs-l37 gammp. radiation. These readings were recorded in field log sheets. Control chart plots of these response check readings are filed in the Technieal Data Annex. Af~r the fielfi portion of the investigation was completed, all field data files were validated lu! before their inclusion into the accepted data set. Validation procedures are in the Technical Work Plan. The essential part of the validation procedure was a review of the electronic file r-1
!i with the field iog of the initial reading in each grid, to ensure that data were assigned to the L.J appropriate grid in the FGI study ar~.
4~S.4 Results and Discussitm Of .the 1502 10 .m x 10 tn grids covered in the surface characterization survey, the walkover survey evaluated a total of 13 i4 grids. There were. 141 grids with brush and growth thick enough to preclude mov.ing the detector across the ground surface. Field personnel pu*sped ipto n u these areas to accomplish the timed readings with the stationary probe but could not move the probe sufficiently to search for anomalous elevated areas. Another 47 of the grids in the surface characterization survey were grids added to verify the edge of the deposition contour and were not evaluated by walkover. Walkover data from 95 grids were rejected and not used because of concerns of data quality, leaving 1219 grids with accepted walkovet data. Reasons for rejection of the data included d~ta 5Contraetor instruments were calibrated by GTS Instrument Ser\iices, Pittsburgh, PA. Instruments supplied by the WVDP were calibrated by WVNS Co., Inc. WNYNSC Off-Site ;Radiation Investigation 4-33 April 20, 1995
files co):l'upted o:r lost in the download process, an indication that survey data were recorded in the timed inode rather than the "peak trapping" mode, and erratic instrument performance evidenced by large relative percerit difference between initial arid re-surveyed peak values for a grid. Figure 4-8 provides an indication of the locations of ~rids that had unacceptable walkover data or anomalpu_s results. The walkover was performed to evaluate the unifQrmity of radiation emissions in a local region and whether anY "hotspqts" were present. The relative *fluctuation of cou*nts with position was evaluated by comparing the largest of the four peak count rates in each .grid, the grid peak count ra!e, ~o the average of the dght sµr:fa~e counts from the timed accumulation survey of that same grid, the grid average count rate. Since the eight surface counts were determined by 30-'second counts, the grid peak count rati;s which \vere logged in counts/minute were divided l;y two to enable direct comparison to the grid average count rates. Tables of the four peak trapped values and the ratjo of grid peak to grid average count rates for each grid are provided in the Technical Data Annex~ The definition of a hotspot .is somewhat subjective. The horizontal variability study, discussed above, indicate4 that variation in a single grid could be e~peeted to b~ within a factor of 2 or iess for the peak to average ratio. Thus a peak to average ratio of 3 or greater was used t,lS t:lil indica.tor of anomalous walkover res"!lltS. Twenty two grids were found to have anomalous results where the peak to average count rate was greater than three. This represents approximately 1.8% of the 1219 grids with acceptable data. The~e grids are designated by an
*~x" code on Figure 4-8.
'.fhe presence or absence of "hotspots" .on the 95 grids with walkover data rejected due to quality
- concerns could not be evaluated. Their location is indicated by a q" code on Figure 4-8.
WNYNSC Off-Site Radiatio~ Investigation 4-34 April 20, 1995
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b b I q quall!y concerns on instrument I x, I caused rejection of walkover data STRE,l.ll y wqlkovel'." ond timed surveys ~ were performed with diHerent instru*ments x one or more of the walkover vaiues exceeds 3X the overage Figure 4-8 Fine Grid Area With Walkover Exception Explanation Notes SCALE: Grid cells are lOm X lOrn
$DAMES & MOORE January 14, 1995
4.6 SYSTEMATIC DOSE RATE (MICROREM) SURVEY 4.6.1 Purpose . I
. l The systematic dose rate survey provides a deten:nination of average raciiation dose equivalent
~ ~ rate in the FGI study area. This measu"remel1t places an upper bound on the tissue dose due to gamma radiation from all radioactive sources, both iq the ground and iii cosmic radiation
*background.
4.6.2 Methods Using the tissl!e-equivalent dose rate meter (Bicron microRem meter), the field surveyor obtained a dos~ rate reacilng at 1 meter from the ground surface by yisuaily observing the live-time meter response. Eight measurements per 10 m x 10 m grid were recorded by hand onto the appropriate field data log. Following data validation and revj~w of the field logs, the eight readings in µr~m/hour W~e submitted to the averagiqg and corifitjence limit statistic~! tests contained in Chapter 8, NUREG/CR..:5849 (NRC, 1992b). Results are reported as the average dose rate for each 10 m x 10 m grid, based on 8 mey.surements. per ~rid, and the 95 % confidence limit of the grid average dose rate .. Contours for representing the dose equivalent rate levels in figures were generated by importing data files with grid coordinates.and block 95% confidence levels of activity concentration into the surface mapping program, SURFER6* In SURFER, the minimum curvature method, a method widely used in earth scienc.es applications, was used to develop smoothed contours that were representative of the fluctuating grid average data. ll 6 SURFER for Windows, Ver .5.02, 1994. Golden Software, Ilic., Golden, Co. WNYNSC Off-$ite Radiation Investigation 4-36 April 10, 1995
4.6.3 Data Quality Instruments were calibrated to tlie gamma radiation from a Cs-137 ,source by an iexternal calibration laboratory. 7 Instrument operation and stability were verified with a measurement of ambient background radiation ani;l _a reference source of *gamma radiation. These readings were recorded ln field log sheets. Control chart plots or these response *check readings are filed in the Technical Pata Annex. To verify measurement reprodticibiiity, 55 .grids (4%) of the total 1-352 ~rids wl.th vaiid data
\Vere resµrVeyed either on a different day or with a different instrument, using the same 8 point measurement method discussed above. Each grid average dose rate was compared to the
.original.grid average by calculatjng ~he Relative Percent Difference (RPD). For each of the 55 repeat surveys, the RPD of the grid average *was less thart 50 %. For 10 of the 55 repeat surveys, the RPD was greater fll.ap 25 %, i(ldicating the differences in foterpreta,tion of the bouncing meter dial by individual surveyors random fluctuations at these rem background radiation ievels. A listing of the initial and resurvey~d dose rates for the 55 grids is provided r.~~* ~
in the Technical Data Annex.
- 4.(j.4 Results and Discussion The systematic dos~ rate survey data. was obtained on 1352 grids (90% of the 1502 grids with surfa~e characterization data). Twenty-one grids wer~ Classed a:s inac~essible dµe to the
' !] presence. or buildings,
*CJ.
.. pond or auto storage, and data was not .recorded for 2 grids. There were 163 grids that had been incltidect' in the systematic soil activity si,Irveys that were not surv~yed for dose rate: 85 grids of inaccessible brush and 78 grids on the northern and western ed~es of the FGI study area.
! 7 i GTS Instrument Services, Pittsburgh, PA.
;I WNYNSC Off-Site Radfation Inv~tigation 4-37 April 20, 1995
": l j
l
Tabl~ of the average dose rate and the standard deviation for each grid are provided in the Technical Data Annex. The data is summarized fo Figure 4-:-9, where the grid averages are portrayed on a map of the survey p.rea. Contours _of the 95 % confidence levels are shown in Figure 4-10. Grid avera~e dose rates ranged from a low of 3.0 +/- 1.0 inicrorem/hr to 6.1 + 1.2 tnicrorem/hr in the FGI study .area, and the. 95 % cpnfidence level on ~he grid average ranged from 3.6 to 5.3 microrem/hr. The dose rate observed in the ba¢kgroun.d Jocations l;'ailged from 3.4 +/- 0~8 microrem/hr to 3.7 +/- L3 rnictorem/hr. The contours 9f the 95th percent confidence levels of 50 m -~ 50 m blocks indicated small regions of slightly elevateQ. radiation dose, but the higher do_se rat~s do not. consistently coiridde with the Cs-137 concentration distribution contours shown in Figure 4-7. This indicates that the Cs-137 external gamma is -a relatively sm.all component of the total gamma dos_e rate that occurs in the FGI study area. 4.7 SUM:MARY AND CONCLUSIONS The observations and survey results discussed above indicate that the area of deposited Cs-137 was adequately bounded and quantifi~d by the survey procedures used. The correlated t "~i I _j instrument readings proviqed a statistically valid reJ>resentation of the distr:i,bution that m,ade the extensive sampling and laboratory analysis unnecessary. Eight readings fo each grid provided an adequate indication of the average Cs-137 activity in the grid to meet the characterization requirements identified in the NRC mimuru NUREG-5849 (NRC, 1992b). Walkover surface scans in the. FGI indicated that 1197 lOm x 10m grids did not haye artamolous point sources *of Cs.,.i37 or "hotspots". The walkover survey identified 22 grids where the peak count rate *was greater than .three times the average count rate, and there were 95 grids whieh could not be evaluated due to data quality rejection. These grids neied further evaluation in order to verify and quantify the absence of any hotspots of radioactivity. WNYNS~ Off-Site Radiation fu.vestigation 4-38 April 20, 1995
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.Contours of 95th Percentile Total Oose Rate;;* (mic:rcrem/hr)
SCALE: Grid cells are 50m X 50m
~DAMES & MOORE
Tl1e ,gamma radiation dose rate survey res].llts indicated that there w~re: two localized region$ in the study ar~ jn which the dose rate was 1.2 to 1.5 microrem/hour greater than the ambient oackground of 3.7 microrem/hour. This level of external garpma radiation dose rate i's within the variation of dose rate reported around the WNYNSC hy previous aerial surveys (EG&G, 1991). Soil sampling at locations .in this area indicated that Cs-137 activity a,ppears to b.e associated with t the orgii:riic humus layer on the ground ~uijace. In the stu9y region, this s.urface layer* is approximately 2 11 -4 11 (5-10 cm) thick, lying on mor~ impermeable clay l:>~low. n Soil radioactivity *analysis indit~ted a variable local distributipn of the observed activity; the Cs-Ll 137 *concentration might vary by a factor of 2 to 3 within a meter or two horizontal tiispla,cement. This *variation .a,ppeared to be a pen;utbatidri tlue to local surface effects, e.g. driplines from trees and limited variatjons in thickness of the humus_, rather than isolated p¥ticles of higher activity. The.local variat:fons in soil radioaptivity appeared within the broad gaussian pattern ofdeposltjon from an airborne piume; on a large scale, tbe *c~-137 concentration decreased with di.stance from the peak value alo;ng the c~iltral radial, and it. decreased with pistance away from the cenµ-al radial of the deposit LOcal terrain and surface characteri$tiCS had minor influence 1;m the gaussia,n pattern. nie cqntouts of the 'Cs.,137 .soil concentration from this sgrvey are co~pared tp the contours of the previous aerial survey irt Figure 4-11. the deposition area is consjstently located, within rl L the uncertainties assodated with each ?f the s_urteys. WNYNSC Off-Site Radiation Inve$tigation 4-4i April 20, 1995
II l 'l.\ I 1. ') l ,, I L EXPLANATION
.35 pCl/g ij ..., . I 20 pCl/9 i!
Plume c. onto.ur:s from 1s pCl/bl 1984 aerial survey
~ I (EG&G, 1991)
L J 1.0 pCl/g 0 pCl/g line of surv*ayad area Figure 4-1.1 Comparison of Ground Surveyed end Aerial Surveyed CS-137 Concentrations SCALE: Grid cells are 50m X 50m
@DAMES & MOORE Aprl! .4, 1995
Section 5 DOSE ASSESSMENT
- 5.1 O.VEJlVIEW
- .s. 1.1 Purnose The dose a5s~sment for the WNYNSC Off-Sit~ R:;diation Investigation has b~n performed to detennine a: poterttia:.I radiation dose to an individual .in 'the. FGI stµdy area due to the ccmcentration of radioactive Cs-137 in ..the soil. The potential dose can then be coII1pared to regulatory guidelines; if available, to identify situations in which further management actions may b~ warranted.
While the concentration of raclio~ctivity fo soil can be precisely determined in th~ laboqitQcy, regulatory guidelines for x:esldual radioactivity are expressed in levels of annual radiation dose, as discussed in Section 1 of tbis report~ '.Regul;:,.tory guideline levels of 10-l5 mrem in one year cannot be distinguished *by direct measur~111ent frpm the normal fluctuations of the ambient radiation levels in Western New York: The pose assessment proces$ uses th~ measured activity in ~e spil and conseiyative a5sumptions on individual exposure and land uses to develop an estimate ofthe expected dose to the individual. Through the 1,lse of prudent, i;onservative a;ssumptions that tend t(J overestimate the potential dose, the methOd will qµantify art upper bound dose, .greater than th~ potenti~ dose to* furore residents. 5.L2 Organization of.the .Dose Assessment In the evaluation Of potential doses from residt:1al radioactivity at a site, the magnitude of the dose Is assessed by a stepwise process of analysis. The steps .of the process are: WNYNSC Off,-Site Radiation Investigation 5-1 Apri.I 20, 1995
- Characterizing a source distribution pf raafonuclides .on tjle site;
'1 ( j u
- Establishing a computer model (or amilytjcal solution) that simulat~s the n
'l environmental t:ransport of radionuc.licies and exposure to radiation in the u environment;
- I>etining ~ppropriate scenarios of exposure for :per$om;iel occl.lpying the affected area, and
- Calculatin~ the dose to th*e exposed individual.
The first step, characterizing the source distribution was addressed in Section 4, above. Thetemaining steps of the process are discussed in subsequent paragraphs of this section. S.2 ENVJRONI\IIENTAL TRANSPORT MODELING 5.2.1 Environmental ExpoS1Jre Pathwavs The analysis of ~nvironmental tra,nspo:i:t i$ based on the pathways qf the .routes by whi~h radionucliQes can migx:ate from ih~ source to _a location of human exposure.
... , The exposure pathwa:y and th¢ rat¢ of migration of the rad.ionm::.Ude in th~ pathway influence L the m~gn.itude of the exposure to .the members of th~ population.
A block diagram of expos11re pathways is illustrated in figure 5~ 1. Individual p'1tbways can be deleted for site-specific evaluations based on tl)e source term and land use assumptions. For this analysis, two gen~ral characteristics relevant to the exposure pathways can b¢ defined. WNYNSC Off-Site Radiation Investigation 5-2 April 20, 1995
1 j I f i 1 II 'l ~ i l Source Environmentf]/ Pathway Exposure Pathway Dose I Ground I
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~DAMES & MOORE I April4, 1995
- Radionuclide Migration - Radionuclides can be removed from the soil by surface erosion (w'ip.d and resuspension),* by plant uptake, and by inftltration and leaching by precipiUttion.
- Radiation Exposure
- Exposure can occur following inhalation or ingestion of contaminated soil, ingestion of water, foods meat and milk from contaminated areas, ot by direct external gan:una irradia~on from radionuclides at :or .heen the ground surface.
5.2.2 Modelin2 Environmental Transport The RESRAD code is an analytical tool for modeling environmental transport ofr~sidual radioactivity in the spil (DO~, 1993). The code is recognized and used in analysis and comparative studies by both the NR,C and the EPA. Additionally, the code enables* ilie c~culation of potential dose~ to individuals when appropriate exposure parameters are .provided. The followirig discussion of the RESRAD cod.e is extracted from the RESRAD implementation manual: The derivation of individual doses from radionuclide concentrations in soil is based on a pathway analysis method known as the concentration factor method (NR.t! 1977; NCRP, 1984). With this method, the relation between radionuclide con(:entrafions Jn soil and the dose to a member df a' critical fiopulaiion group is expressed as a sum of the products of "pathway factors. " Pathway factors correspond to pathway segmei!ts connecting compartments in models of *the environment berween which radionuclides can be transponed or radiation transmitted.. ,. A pathway product or pathway factor may be {ld.ded; deleted, or replaced, fn most cases, without affecting the other pathways or pathway factors. This structuring facilitates the use of alternative models for different con4itions
- or transpon processes an.d the incorporation of additional pathways. Thus in most. cases, RESRAD can be easily modified or tdilored to model any given WNYNSC Off-Site Radiation Investigation 5-4 April 20, 1995
r1 .
.I
.' situation by merely adding or replacing fadors or terms in the pathway sum . (DOE, 1993). The RESRAP code performs an analysis based on the use of approximately 150 parameters describing the source distribution, site characteristics, exposure scenario and environmental pathways. A sensitivity analysis module built into the RESRAD code was used to study the sensitivity of input parameters on the uncertainty of the results, .and is
~:liscussed below. In this dose assessment, the code was used to calculat~ annual doses fro.m valµes of soil radioactivity concentration and individual e~posure scenario parameters.
5.3 REFERENCE CASE EXPOSURE SCENARIOS An exposure sc.enario is a pattern of human activity or potential land use that causes the individual to be in a location where the radioactive material is, thus resulting. in an exposure. The scenario includes the parameters of the rate of release of material into the environment, as well as the individual's duration of occupancy of the area containing th~ radioactive materials. Exposure scenarios are combinations of activities and assumptions used to evaluate site risks under various land uses. The *choice of a scenario of an individu:ril' s exposure to residual radiation has direct influence on the calculated dose. Regulatory guidance provides insight into alternative scenarios to be considered when projectipg future exposure. The NRC recently developed three stallllard scenarios as reference cases
- to foster cot1sistency and sufficient protection in analyzing potential doses associated with residual raqioactivity (NRC, 1994a). These cases are:
I
. j J
WNYNSC Off-Site Radiation Investigation April 20, 1995 l
r '1 J . a. Commercial-Worker Scenario. The site is not used for residential purposes. Individuals are subjectetj to diree.t exposure to external radiation and inhalation of airborne radioactive material. from contaminated soil only while working on the site cmd not wb.ile at hoil1¢. Exposure occurs for 2000 hours pet year with approximately 40 % or 400 hours of that time spent outdoors in the qont;aminated area.
- b. Resident-Worker Scenario. The site is J.ISed for residential purposes, but individ!lals leave the site for occupational pursuits. On-site residents are subjected to direct exposure to external radiation, and inhalation and ingestion of airborne radioactive material while at home (40% of the time indoors and i0% of the time outdoors) but not while away from the site (50% of the day). The scenario assumes a small house garden provides 25% .of the resident's annual :vegetable, grain and fruit diet ..
J)rinking water com¢s from an on-site well-, while m~t and milk products origin;ite from off-site sources.
- c. Resident-Farmer Scenario. The site is used for resictential and subsistence farmin~.
The resident-farmer spends 76% of the year on the site (21 % outi:loors and 55% indoor~) with 24% of the time iiWay from the site. Exposure pathways include external radiation, inhalation and ingestion of radioactive material. One. . half of the
- vegetables, fruit, grains and mea~ in the diet is produced on the farm, ~s well as
,l.00% of the milk arid drinkin_g wa~er.
The use of th~e standard scenarios provides the NRC a common benchmark method for the evaluation of population expqsure. The evaluation results may _or may not be representative of actual expos\lreS only to the extent that actual personal lifestyles mimic the scenarios assumed for evaluation. In this manner, the NRC has stated that the Resident-Fanner.
. . . is intended to represent the maximum reasonably exposed individual. Because the scenario ~s based on 'ptudentlJ conservative' assump{ions that tend to
*WN'YNsc Off-Site Radiation Investigation April 20, 1995
overestimate po.relitial ¢oses, ~e of this scenario should re~ult in f!Stimated doses that will be greater than the exposure to future residenis m,ost of the time (NRC 1994a). This dose assessment w!ll use the Resident-Farmer for evalua:tin~ potential radiation doses from the Cs--137 observed in the FGI Study Area. This scenar:lo is conservative and uses parameters that result in more exposure to the contaminant than other scenarlos. It will be modified by adapting parameter values to fi.t observed or projected land 11ses and population lifestyles discussed below. In the Western New York regio~, the growing season is short, and the winters are cold. La.ke*effect snows provide a thick cushion of snow and ice that provides an extra dose reduction between individuals in the woods and the material at the ground surface. The cold also decreases the time spent at out-of-doors activities. Thus the time spent outdoors used in the standard and modified scenarios would be conservative for estimating the time spent outdoors in the Western New York region. Recall that the area of highest Cs-137 concentration is in the undisturbed woods. Prudent existing use scenariqs of popul~tion. exposure should evaluate the impact of ex~sting woodlands. Estimates of future exposures due to residual* radioactivity must take into account uses of the land in its current state, ~ well as how postulated future uses might
*change the existing distribution.
5.4 EXIST.ING LAND USE S,CENARIOS The FGI study area has a limited scope of land uses and exposed individuals. The study area enco'mpassed appro:Ximately 46 ~cres on properue~ belonging to three landow11ers.
,Evt).lµations of the existing and future land uses and individual exposure are discussed
- below.
i . I WNYNSC Off-Site Radiation Investigation 5-7 April 20, 1995 I.. i
- 1
~ I
' l'
5.* 4.1 Realistic Current Use - Standard Scenario: Resident-Fanner In the .northern region of the FGt, Tax Map Property 15.3 (TM 15.3), the study* area -included undisturbed woods adjacent to tilled farm fields. Tt"!e result.s of t)le soil act;ivity surveys discussed ill previous sections indicated tl:lat e:xistlvg farmland showed low Cs-137 concentration due to continual b1ending of the soil in the tilling and fertilizing process. Open yards near houses in the disturbed area also shmved reduced activity, due to clearing* and leveling the property for a hornesite. Tbus th~re is littl~ evidence that disturbed .lands remain a significant source of rai:iioactive _material or popuiation ~~~~~~~~~~~~~~~~~~ re,sident-farmer. Un(listurbed wobds *ar~ eyaluated under tlie n~xt scenario. 5~4.-2 Realistic Current Use - Modified Scenario: Hunter.,Camper In the central region on TM 15.1 the oniy use of the land in the study area was tindi_sturbe'd woodlands. The use of this land is for recreation purposes, primarily hunting in season, and the cutting and colleetion or firewood. This use of the land will be evaluated using the outside diiect expos!lre pathway, to obtain the QOS$ f()r each 100 hours .spent in the woods; 5.4.3 Con*servative Current Use - Modifleo Scenario: Resident ~Homeworker In the. southern portion of the FGI survey area, one parcel (TM 16 and TM 23.2) includ.ed one permanent :residence, and two occupied house trailers. In additjon to undisturbed woods, there were several acres of land cleared and used for the storage of derelict vehicles. The *owner/resident operates a h_ome auto mechanic shop on the site in the permanent building with residence quarters over the repair shop. This use of the land will be. evaluated using the resident-farmer st;andard scenario rather than the resident:--worker standard scenario, to account for extra time on site since the occupational location is on the site, as in the resident-Janner standard scenario. WNYNSC Off-Site Radiation Investigation 5-8 April 20, 1995
j J ,.* l 1 5.5 FUTURE LAND USE EXPOSURE SCENARIOS The NRC guidance indicates that alternative e~posure. scenarios may be appropriate based on sfte.;specific factors or condltions that affect ~he likelihood and extent of potential future exposure. The NYSDEC does not define or quantify parameters f9r alternative exposure scenarios (NYSDEC, 1993); The analyst must define the exposure scenarios, with the guidance to use "te<lSonable scenario$ for current arid plausible future uses of the land." The definition of a plausible future exposure scenario for the wNYNSC Off-Site Radiation Investigation study area is complicated by the prediction of future land uses c:::
*~ j that would not diminish the existing. radioactive soil concentration of Cs-137. The I l LJ highest soil activity was observed in undisturbed woodlands, w*here Cs-137 is found in the surface humus layer. Any of the NRC "s~dard" analysis scenarios discussed above suppose a land use* that would disturb the surface layer pf soil, resulting in lower direct exposure to individuals on the site. For instance, in establishing a new hoinesite, the lani;i in the woods would :be clear~d of trees and stumps, which would result in the surface soil bein~ di~tl!rQe:d. When leveling tbe area, the ;;urface soil woQlQ b~ mixed and blended to a depth of 12-18" or more; so that the average concentration would be*
tnuch reduGed. Suen reductions jn surface activity concentrations and blending through depth were obser\!ed in the survey of disturbed areas, whose results are listed in Table 4-5. 5.5.1 Realistk Future Use - Modified Scenario: Hunter-Camper A realistic expectation is that the woods will remain in their undisturbed condition and continue to be used for recreation. Thus this future use scenario mimics the. existing use discussed iibove.
'i
- i WNYNSC Off-Site Radiation Investigation 5-9 April 20, 1995
, I
5.5.2 Conservadve Future Use - Modified Scenario: Residence-Traner A plausible future use of the woodlands is that a residence coyld be built 'in an undisturbed area, leaving some of the radioactivity among the undisturbed trees in the vicinity of the yard. The residential use least disruptive to the surface deposit of Cs-137 would involve a trailer h9me i:ather than a conventional fixed stnicture. In this case, the trailer home is placed on cleared land; but the resident can spend some time outdoors in the undisturbed woods where the radioactivity remains on the surface.
*for the Residtmi:e-Trailet scenario, the time outdoors is partitioned with *80% .in disturbed areas and 20% in the undisturbed area. The resident would more likely spend ~t most Of his time in the disturbed area,; near the trailer, yet .still spend some time in the j
adjacent woods hunting, cutting fitewoQd, ~tc. The maximally ex:posed individual in the.
.residence trailer scenario wo.uld be* a fat:nily member who spends a number of hours per week in the undisturbed woods.
S.5.3 Other Potential Uses The evaluation of the Residence-Tr9iler Scenario places an µpper hound on the e.xposure of future residents. Other possible uses of the woods require more disruptive intrusion into the surface l~yer and would result in lower concentrations of radioactive material than the residence trailer scenario. In this *section alternative land uses.for the undisturbed woodlands have been described, as well as diSruptions in the existing source dis:t;ribution caused by t.h~ propo~ed land use scenarios. Potential annual doses resulting from each of the scenarios are discussed in the ne~t paragraphs. WNYNSC Off-Site Radiation Investigation s:.io April 2d, 1~95
5.6 :ESTIMATES OF POTENTIAL SCENARIO DOSES The RESRAD code W~$ used to ca!culate potential doses under the scenarios of existing and future land use. The limitations of the code and the modelling method were discussed in the RESRAD Implementation Manual: Mode.ls for d(!riving .. . dose .limits are simplified representations of complex processes. It is not feasible to obtain sufficient data to fully or accurately chan;zct~rize trqnspon.t:mrf. ~po~ure proe.esses. Simila,rly, it is not possible to pr.edict Jutr/re cont1Jr.t9ns with cenainry. . Consequently thete will l:Je uncertainties in the derived values.... The models and input parameters incorporated into RESRAD have r1 LJ been chosen so as to be realistic, but reasonably conservative, and the calcuJate.d doses corresponding to guideline values of the radionuclide toncentrations ate
~pected to be reasonably conservative es.ti.mares (ovetestim:ar.es) of the acrual doses.
(DOE, 1993) Thus it is important to rememb~r that just as the scenario is designed to over.;estima:te the time and exposure to the radioactivity, so does the RESRAD code .over-estimate at each step in calculation. Thus the final dose calculated for each of the following
- scenarios may greatly over-estimate the actual dose it is attempting .to repr~ent.
5.6.l Resident-Fanner Scenario On property 15.3 on the northwes~ side of the FGI study area 1s a tilled field. The Cs-137 activity .concentration observecl on this .site is used to evaluate the residem-farmer scenario, a property u.sed for residential and subsistence farming. [i WNYNSC Off-Site Radiation Investigation 5-11 April 20, 1995
- a. Critical Parameters influencing the calculation (1) Soil Cs-137 Activity Con'Centration .in pCi/g and thickness .of the contaminated layer* in. meters LI
- Values used in the calculation:
Soil Activity J. 0 pCilg Typical activity observed in disturbed areas r1 l-,.,.._;.! Thickness 12" (0.30 m) Typical thickness of .di~rurbec{ surface soil layer in tilled field; activity at depth below 12" has little impact on :surface exposure [J due to absorption/shielding. by the* soil. (2) Time spent on site; apportioned :into indoors and outdoors, in percent of year. Fo! calculation purposes, ).ise times suggested ill the NRC Residenr:-fanner, defined for i*max,imum exposed in4ividua1 \l.nde.r prudently conserva.tive assumptj<;>ns"
- Va1ues used in the calculation:
Time Indoors $5% NRG-defined vruue 1 residem:Jtirmer
.Time Outdoors 21% NRC-defined value, resident-Janner Time Away 24% NRC-defiried value~ resident-fanner
('.3) Indoor shielding factor; as per .cent of .radiation that is transmitted tq inside
- Values used in the calcuhi.tlon:
Tr.ansmissipn to NRC-defined value to account for ~hielding indoors .. provided by building wails and foundations
- b. Results. Th~ RESRAD calculation indicate$ that for this realistic. land use, usin~
prudently conservative a.Ssumptlons, the annual dose in the current year is 3.1 mrein; Due to physical decay of the Cs-137, the annual dose to the individ in subsequent years is le$S -than in the current year. The annual dose in the current year by WNYNSC Off-Site Radiation. Investigation 5-12 April 20, 1995
*, l . j
pathway components and sensitivity factors for each assumed value are summarized I I in Table 5-1. J Table 5-1 Resident-Fanner S~enario r1 Table 5-la Summary of Critical Scenario Parameters Used in Modeling Potential Doses RESRAD RES RAD
¥enu Varial)Ie Parameter Value used Comments Screen Name Thickness of Soil Layer 03 Di Typical Thickn~s RQll tm:o::o Cs-137 Activity in Soil .LO pCi/g Typical observed R012 Sl(l)
J:ransmissicm tp Indoors 67% NRC-defined value R0.17 SHF1 rµne Indoors 55% NRC-defined valu~ ROi7 FIND Time Outdoors 21% *NRC-defined value R017 FOlD Table 5-lb Potential Dpses Pose in Current year I Pathway I (mrem) I Comments I Ground .Direct Inside 1.9 Based on 55% (4829 hours per year) dose changes by +/- 0.038 mrem per 100 hours Based on tran.smissio.il of 67% of outside radiation dose decrease5 0.31 mrein per each 10% less in transmission 1
,.J Ground Direct 1.1 Based on 21 % (1840 hours per year) dut!iide dose changes by.+/- o.os~ mrem Per 100 hours Diet from home garden 0.-1 . Based on 50 % vegetables, fruit, *grain, meats (100% drinking w~ter = 0 mrem/yr)
I i 1l Total Dose in 3.1 Based on 1.0 pCi/g in 12 inches; L ..1 Cu~nt Year dose is proportional with concentration WNYNSC Off-Site Radiation Investigation 5-13 April 20, 1995
5~6.2 Hunter-Camper Scenario An individµal spends time in the undls'rurbed woods for rec~¢ation p*urposes. All exposures are qutdoors with no bl,lildings or disturbances to the surface layer of contaminated material.
- a. Critical Parameters influendn~ the calculation (1) Cs-137 concentration of soil in pGi/g .and thickness of the contaminated layer.
- Yalµes 11~ed in the calculation:
n u Soll Activity 21 pCi/g 95 % confidence level of average activity in most coritam!nated 0.6 acre (50 m x 50 m) u ThiCkn~ss of Cs-137 3'; (0.07 ~) parcel Typical thickrjess observed 1n survey Soil Layer undisturbe<,i (2) Time spent on site, only outdoors, in per cent of year. For calculation purposes, use blocks of 100 hours .. (100 hrs = Ll4% of year)
- b. Results The RESRAD calculation indicates that under the assumption that hunting and camping occurs fu the most h~vily contaminate4 0.6 a<;re {50 m x ~O m) area, the annu~ do~e in the current year is 0.73 mrem per 100 hours spent in the undisturbed woods. The*
~cen;ttio p~eters and re~ults ar~ summarized in Table 5-2.
WNYNSC Off-Site Radiation Investigation 5-14 April '.20, 1995
Table 5-2 Hunter-Camper ScenariO Table 5-2a Summary of Critical Scenario Parameters Used in Modeling Potential :Pos?S RES RAD RESRAD Value used Comments Menu Variable Parameter Screen Name Thickness of Soil Layer 0.075 m Typical thickness observed in the ROll TIITCKO study area Cs-137 Activity in Soil 21 pCi/g Most elevated 0.6 acre parcel R012 Sl(l) Tiµie Outdoors 1.14% 1.14% of year= iOO hours ROJ7 FOTD Table S. .2b Potential Doses Dose in Pathway current year Comments (mrem) Ground Direct 0.73 Based on *1.14% (100 hours per year) Outside dose changes by +/- 0. 73 mrem per 100 hom:s Total Dose in 0.73 :Based on 21 pCi/g; Current Year dose is proportional with concentration 5.6~3 Resident-Homeworker Scenario A residence is in the WNYNSC Off-Site Investigation area, ~d the occupant spends a majority of each day on the site, working in the shop with the re.sidence overhead.
- a. Critical Parameters influencing the calculation (1) Cs-137 concentration of soil in pCi/g and thickness of the contaminated layer.
- Values used in the calculation:
J
- l. .l Soil Activity 3 pCi/g 0.6 acre parcel with residence; upper bound overestimate (See Table 4-5)
Thickness 611 (0.15 rn) Typical thickness observed in survey p l l \ I
- r l I l j L'
WNYNSC Off-Site Radiation Investigation 5-15 April 20, 1995 .I .I
(2) Time spent <;m site, apportioned into .indoors and outdoors, in per~ent of ye$. For
.calculation purpos~s, use times suggest~d .in the N:RC Resldent.,Fa.rmer, defined
. for ;'maximum exposed 1ndividual i.lf1c!er prudently con$ervative *assJJmptions"
- Values used in the calc:;µla:ti9n:
l Time Indoors* 55% NRC-defirted value, resident-Jannet
.1 Time Outdoors 21% NR,C-defi.ned value, residem--jatmer Time Away 24% NRC-defined value, resident-farmer (3) Indoor shielding factor, as percent of radiation that fa transmitted to inside
- Value tised 1n the c~culation:
Transmission 10% Underneath building is uncontaminated with tO Indoors living ~ea elevated over work area.
- b. Resµlts. RESRAD calculation inpicCl.te5 that under these cop.servative, over-estimating assumptions the annual dose in the current year is equal .to or less than 4.8 inrem. The annual dose in the current year a.pd sensitivity fa.~tors for each assumed value are r1, summarized in Table 5-3. D.ue to radioactive .decay, annual dose in later years is le~s J '
than in the current year. 5.6A Future Use, Conserva~ive Scenario: Residence-Trailer Scenario A t,rfiller home is placed on a site Cleared and leveled iI~ the c9ntaminated woods. The \l trailer is less s!.ibsta.ntfal than ~ permanent residence and permits more radiation to u peri~trate intq the inside.
- a. Critical Parameters influeni::ing" Ure c~cul~tion Estimates* of future exposures due to residential radioactivity must take :Into account how postulated future uses might chang~ the existing distribution of Cs-137. For the Residence-Trailer scenario, assume a 50m x 50m area in the most contaminated area of the woods is cleared for the placing of a trailer.
WNYNSC Off-Site Radiation Investigation 5-16 April 20, 1995
Table 5-3 Resident-Homeworker Scenario Table 5-3a Summary of Critical Scenario Parameters Used in Modeling PotenWd Doses RES RAD RESRAD Value Comments Menu Variable Parameter Screen Name used Thickl1es.s of Soil !.,ayer 0.15 m Tyt~ical thickness observed in the ROll THICKO stiirly area Cs-137 Activity in Soil 3 pCi/g Most elevafed parcel that contained a Ro12 Sl(l) fixed .resi9ence Transmission to Indoors 10% Less transmission (more shielding); R017 SHF1 elevated living area over uncontaminated ground Time .Indoor8 55% NRC-defined value R017 FIND Time Outdoors 21% NRC*~efined valu_e R017 FOTD Table 5-3b Potential Doses Dose in Pathway current year Comments I I (mrem) I I Ground Direct Inside 1.0 Based .on 55 % (4820 hours per year) dose changes by +/- 0.020 mrem per 100 hours Based on transmission of 10% of outside radiation
- dose increases 1.0 mrem per each Id% adelit1onal transmission Ground Direct 3.8 Based on 21 % (1840 hours per year)
Outside dose changes l?y +/- 0.2.0 mre.m per 100 hours 0 Less that 0.1 % of total
- I
) ;
Inhalation Total Dose in 4.8 Based on 3 pCi/g; Current Year dose is proportional with concentration (1) Cs-137 Concentration of the soil (in pCi/g) and thickness of the soil layer (in meters): Cle.aring and leveling the land in the woods blends the existing (s-137 ~ctivity throughout the top 18" {0.45 ni) layer. A fraction (50%) of the Cs-137 activity is removed from the ~xposure pathway by being covered/buried below
'*1 ' 'I 12" ~ where it has little influence on the exposure of people on the surface. . *1 . j ~ j WNYNSC Off-Site Radiation Investigation 5..:17 April 20, 1995
- " ~
.: I
- Vall1es u~ed in the calculation:
Average activity of. th,e most elevated 0.6 ~u~r~ (50 m x 50 ni) undisturbed block was 21 pCi/g [observed values ,ranged from 11 pCi/g to 35 pCi!gj. Then future disturbed concentration would be 1.8 pCi/g [21 pCi/g
- 50% **
(~ /18)]. 11 This value of activity and the uniform activity with depth are similar to that seen near an existing residence (Location code RH-2 7 Table 4*5} and much greati;r than n~ the existing residence tr?ller *(Loca~on code RT-1, Table 4*5). (2) Time spent .on she, apportioned into ind9ors and outdoors, in per cent of year For caJ,culi:i.tion purposes~ use times suggested in the NRC R,esident-Fatmer;. de:tinaj for "maximum e;x;posed inoividual under prudently conservative assumptions"
- Values used in tile calc(lla:tion:
Time Indoors 55% NRC-defined value, resident-farm¢r Time Outdoors 21 % NRC-tjefirt~d v~ue, resident-farmer apportioned with 4 % time ~eilt in the undisturbed woods a,djace~t, to the clearing and 17% time.in the cleared yard area {3) Indoor shielding factor; as percent Of radiation that is transmitted to insl.de
- Value used in the calculation:
Transmissi011 to Jnqoors 80% Residence is a ttailer, situated 011 cleared land, more transmission of radiation than in a fixc:q s~cture
.-.! b. ~esult$. RESRAD indicatE;:s that annual dose in the current year could be 8.0 mrem under the conservative over-estimates in this scen~o. Results are
- ' l summarized in Table 5-4.
(J WNYNSC Off.*Site Radiation Investigation 5-:i8 April 20, 1995
q Table 5-4 '.Residence-Trailer Scenario
' i
~ . ..t Table 5-4a Summary of Critical Scenario Parameters Used in Modeling Potential Doses Value RES RAD .~RAD Parameter u5ed Comments* Menu Variable Ij Screen Name Thickness of Soil Layer 0.3 m Activity below 12" has little impact ROll THICKO on surface djrect exposure Cs-131 Acfr,1ity in Soil 1.8 Most elevated 0.6 ac_re parcel R012 Sl(l) pCi/g 2lpCi/g in 3" surfl!:ce layer mixed into 18" layer with 50% remoyed/buried below 12n Transmission to Indoors 80% More transmission than NRC defined R017 SHFl value; trailer has .less shielding Ti~e Indoors 55% NR<Z-deflned val4e R017 ~IND Time Outdoors 21% NRC-defined value R.011 FOTD apportioned 17% 1n clearing 4% in woods Table 5.:.4b Potential Doses Dose in Pathway current year Comments (mrem) Groun_d Dir~t Inside 3.9 Based on 55 % (4820 hours per year) dose changes by +/- 0.08 mrem per 100 hours Based on transmission* of 80% of outside radiation dose decreases 1.1 in.rem per each 10% less in transmission Ground Direct Based on 17 % (1500 hours per year) Outside (clearing) 1.5 dose changes by +/- 0,10 mrem per 100 hours Ground Direct Oui$ide (woods) 2.6 .dose Based on 4%(350 hours per year) changei_; by +/-_ 0.73 mretn per 100 hours
- l Total Dose in First 8.0 Based on 1.8 pCi/g in 18 inches;
'J Year dose is proportional v.ith concentration Table 5-5 provides a summary of the annual doses that could occur in the current year under the assumptions of the alternative land use scenarios for the properties in the FGI.
The calculation indicates by _pathway the annual dose in the first year under the scenario assumptions described. The majority of the individual dose in all scenarios (standard and
, I ,' 1 WNYNSC Off-Site Radiation Inve.sHgation 5-19 April )20, 1995
alteriiati:ve) is thro~gh the ditect exposure pathway. Under the given conditions, the Cs-137 contaminant does not reach the groundwa_ter before radioactive deca.y r~uces it to inconsequential levels.
- 5. 7 SENSITIVITY ANALYSIS The calculations performed by the RESRAD code depeno directly on values chosen to describe the source distribution, the characteristics of the site aJ).d the exposure scenario.
u f"l S~veral Pa!4ri1ete~s were analyzed to determine the sensitivity of the *calculation results to their assigned values.
- a. Source Distribution Parameters. The RESRAD code uses the term "contaminated zone 11 as the volume of soil in which radionuclides _are pres_ent at above background concentrations and are uniformly distributed. The dimensions and concentration determine the total activity inventory invofved in the analysis.
Table 5-5 Table 5w5a
- Summary of Parameters Used in Scenario Modeling Resident- I;Iunter- Resident- Residence-Parameter Fa~er 1 Camper 2 ~omewprker 3 Trailer 4 0~137 soil layer thickness (m) 0.3 0.07_5 0.15 0.'3 Cs-137 Actjvity (pCi/g) 1.0 21 3 LS Transmission to Indoors 67% - 10% 80%
Time Indoors 55% 0% 55% 55% Time Oµtdoors
- 21% l.14% 5 2J% 21% 7 Diet from on site Vegetables, fruit, grain 50% 0% 0% 0%
Mille 100% 0% 0% 0% Meat and Aquatic foods 50% 0% 0% 0% Drinking Water 100% 0% 0% 0% Groundw;iter fraction 100% 0% 0% 0% WNYNSC Off-Site Radiation Investigation 5-20 April 20, 1995
Table :5*5b Surnm~ry of Doses by Pathway for Reference Exposure Scenarios Doses by Pathway Resident- Hunti;r- *Resident- Residence-(mrem per year) Farmer 1 Camper 2 Homeworker 3 Trailer. 4 Ground Direct Inside 1.87 - LO 3.9 8 Ground* Direc.t Qutside 1.06 0.73 3.8 4.1 Inhalati.o~ 0 0 0 0 Plant foods 0.06 - -. - M.eat Foo.ds 0.07 - - - Mill< from site 0.04 - - - Drinltjng Water 0 - -* - Soil Ingestion 0 0 0 0 Total Dose in Curtent Year 3.10 0.73 6 4.8 8.0 Notes: "-* the pathway is not part of the scenario 5 1.14% of year= 100.hours
*o* calculated dose ::::: 0.01 mrem/yr 6 Total .Dose for each 100 hours spent in 1 US NRC standard evaluation scenario the undisturbed woods 2 Realistic scenario, current and future 7 'fime c:iutdoors apportioned to 17 % in use of undisturbed woods cleared land arid 4 % in undisturbed woods 3 Conservative scenario, current use 8 *sum of (.5 mrem while in cleared land 4 Conservative scenario, future use and 2.6 mrem while in undisturbed woods (1) Area of Contaminated Zone. The defa'3lt value used in the analysis was 110,000 ft2 (10,000 m2). The dose to the individual is relatively insensitive to the*area of the contaminated zone above this value. Almost all of the individual dose is from the direct exposure pathway, and the source is "infinite" when the actual area approaches 10,000 m2* Smaller areas reduce the individual exposure from the direct pathway, and also influence the dose from on.,.site crops and cattle; since the area soon becomes too small to sustain livestock (2) Thickness of Contaminated Zone. The value used in the analysis was 3 inches (7.5 cm). rncreasing the thickness of the contaminated zone slightly decreases the individual dose when total deposited activity is held constant. Since the major pathway is direct exposure, increasing the thickness of the contaminated zone dilutes the soil concentration, moves the material farther from the individual, and introduces more shielding by the soil itself.
VINYNSC Off-Site Radiation Investigation 5-21 April 20, l995
- b. Hydrogeological Parameters. In the* FGI *study area, Cs-137 was retained in the surface layer of humus, with little penetration ii::i.to :underlying clay. Because of the short half-life of Cs-137, with r¢spect to environmental i:ransport times into and through the groundwater (typically hundreds of years), the Cs-137 levels observed in this study will decay to insignificance long before the radioactive material is transported into the subsurface groundwater. Thus the numerous parameters of the
- ! model associated with site hydrogeology and transport have little impact on the
~ J analysis and its results. (1) Thiclmess of Unsaturated Zone. The*unsatm:at~ zone is the sQil layer thl3.t exists between the contaminated zone and th~ *top of the zone s(lturated with groundwater. Tllis is the soil layer thrpugh which th~ radioa~tive material must travel to reach the groundwater underneath*, The RESRAD default value for the unsaturated zone thickness is 13 ft (4 m) (DOE, 1993). Decreasi,ng the unsaturated zone thickness has the effect of raising the ~roundwater sat~ration level closer to the surface and the radioactive material. Varying thi$ thickness from 16.5 ft (5 m) to 8 inches (0.2 m) had no impact on the results. The radioactive material decayed prior to reaching the groundwater table within this range. (2) Distribution Coefficient (K~. .The distribution coefficient (KJ} represents the partition 9f the radioactive material betw~en the soil matrix and the soil water. The Ka value is the ratio of the mass of Cs-137 adsorbed or precipitated on the solids per unit of dry mass of the soil to the Cs-137 concentration in the Uquids. In the usual analysis, a conservative (overestimate) assumption is a small value i of Ka, whi~h m~s that more material fs in the liquid phas~ and the material J moves more rapidly through the soil. The Ka value for cesium used in this analysis was 1000 c~ 3/g, representing a sandy-clay soil (DOE, 1993). In the contaminated zone. Decreasing the K4 value for cesium causes the radioactive material to mobilize out of the contaminated zone quicker, without
\vN:YNSC Off-Site Radiation Jnyestigation 5-22 April 20, 1995
1ncreasing the uptake through other pathways. Since the major pathway is direct exposure, this ~ends to Jessen the dose to the individual. Increasing tne Kd value for cesium has little impact on the calculated dose., since the material has a short half-life relative to geological transport times.
- In the unsaturated zone. Varying the Kd vaJ,ue for cesium from that representing 2~0)
- 1 I organic material and sand (Kd = to clay (Kd = 1900) to loam (Kd = 5000)
J had little impact for two reasons. When the radioactive material remained in the c::ont.aminated zone, it was unaffected by changes in the unsaturated zone characteristics. Conversely, mobilizing the material out of the contaminated zone into th~ unsaturated zone decreased the direct exposure pathway more than it increased the other pathways so that varying the Kd value *had iittle impact.
- c. Scenario Parameters. In the REsRAD analysis of the FGI study area, the majority exposure pathway is due to direct exposure to radioactive material on the gro-µnd surface. In any scenarios, the time spent on-site each day, bath indoors and outdoors, has a direct affect on the potential dose rate to the site resident. In the reference scenarios evaluated here, the hours $!Jent on site agree with the standard values identified by the NRC for the benchmark analysis. Alternative scenarios with plausible and realistic time partitions have also been described to realistically bound exposures under alternative land uses.
J d. Other parameters. Numerous other parameters are available in the RESRAD code to reflei;;t site-specific hydrogeologica1 and s~enario characteristics. Most parameter values impact on use of -surfa~ waters, groundwater, irrigation modes, and fruit, meat and milk consumption pathw~ys; pa~hways whii;;h were not critical in this analysis. The short half-life of Cs-137 relative to geological transport times negates the influence of these parameters in the current stuc;ly. WNYNSC Off-Site Radiation Investigation 5-23 April 20, 1995
l J '*1 The sensitivity analysis indicates that the doses detetmiiled from the l.{ESRAD code under I the scenario and parameter values de5~ribed above are a conservative overestimate of the doses to he anticipated . '.[ .S.8 CONCLUSIONS The dose assessment for the WNYNSC Off-Site E.adiatioi:i. Jnvestigation stuc!y area. has been performed to determine a potential radiation dose to an individual in the FGI study ar~ due to the concentration of radioactive Cs-1~7 in tl)e soil. Plausible scenarios of future land use identified .cha:nges to levels of Cs-137 soil concentration due to l~d use disrurb~ces. Corresponding doses, cajculated with the RESRAD environmental transport and dosimetry code, indicated the following:
* .In current land uses under botl:i realistic *and conservative scenario assumptions, potential annual *doses for the maxi_mally exposed individual are below S rnrem in the curreni year.
- In future land uses a conservative scenario assumption { the residence .trailer scenario) a potential annual dose to the maximally exposed individual wouid be
.below 8 mrem in the current year.
Due to the decay of Cs-137 ~ith a half-life of ~0.2 years, doses in subsequent years will naturally decrease by 2.2 percent each year, without any action. These potential doses are upper bol}nds on the actual doses expected in the study area for two reasons: o The potential doses calcuJat_ed by the RESRAD code "... are expected to be reasonably conservative estimates (overestimates) of the actual doses" (DOE, 1993). wNYNSC Off-Site Radiation Investigation 5-24 April 20, 1995
- The NRC standard resident-farmer scenrujo (whose parameters were use9 in this analysis for the residence.,trailer scenario future land use dose evaluation) ".. ;is q based on prudently conservative assumptions that tend to overestim£1te potential
- . r
- , J doses" (NRC I994a).
Thus, the actual doses to future t.esidents will be ~onsiderably less thari the calculated values. The caiculated *l)pper bound doses are in the range of doses suggested by proposed fedetal decommissioning criteria (15 mrem per year) and state*guidance (10 mretn per year) as discussed in Section 2 (EPA, 1994; NRC, 1994; NYSDEC, 1993). The doses are considerably below the 100 inrem pet year dose limit recommended by the NCRP (NCRP, 1987a) and.are only a smaU fraction of 290 mrem per year, the average annual background radiation in the U.S. (NCRP, 1987). 1 l J "l
., )1
. WNYNSC Off-Site Radiation Investigation 5-25 April 20, 1995
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.Section ,6.o:
. . ' . ~" .* - - ' - .
Section 6 CONCLUSIONS The WNYNSC Off-Site Radiation Investigation was performed in phases of field sampling, measurement and analysis. The observations and survey results discussed above. indicate that the area of deposited Cs,..137 was adequately bounded and quantified by the survey procedures used. For area$ in the FGI with elevated Cs-137, the correlated instrument readings provided a statistically valid representation of the d~stribution that made more extensive sampling an,d laboratory a!lalysis unnecessary. Eight readings in each grid proviqed an indication of the average Cs-137 activity in the grid statistically *sufficient to meet the characterization requirements identified in the NRC manual NUREG-5849 (NRC, 1992b). J 6.1 RADIOLOGICAL CHARACTERIZATION ON A COARSE GRID During the p*eribd November 1993 to J~mary 1994, Dames & Moore performf.!d measurements of gamma radiation anq sampled the surfa,ce and near surfac~ soils at 44 locations in the 1000 acre area between the west.em boundary of the WNYNSC and CattaraugQs Creek as shown on Figure 3-2. the survey confirmed the location qf the elevated areas of C~-137 shown on aerial survey reports and identified a smaller area of approximately 46 acres near toe WNYNSC boundary for more extensiv~ evaluation. 6.2 RADlOLOGICAL CHARACTERIZATION ON A FINE GRID A FOI was defined to evaluate the magnitude, deposition patterns and extent of radioactive material in the study area on a smalfor scale. Field survey efforts were focused on the area of elevated Cs-137 radioactivity deposit identified in the coarse gr.id survey. *The components of the survey included WNYNSC Off-Site Radiation Investigation 6-1 April 20, 1995 .. lI i
1
- An evalua~cm of soil sampl~ tO provide an indicatiqn of porizontal deposition and vertical penetration of the Cs-137, to provide confidence .on the magnitude
.of variability.
- A system~tic measurement of Cs- ~37 gamma radiation *at eight fixed points in
~c}l. grid to provide a determination of soil activity averaged over 10 m x 10 ni areas.
- A systematic measurement of total gamma radiation at eight fixed points in .each grid, to provide a determination. of radiation (lose rate averaged over 10 irJ x 10 m areas.
n u
- A measurement of Cs-137 gamma radiation during a serpentine walkover of areas be.tween .the points of the systematic measurements, to provide confidence th~t
.anomalous point sources of radioactive material concentration would not be
*overlooked.
During the petiod J1.1ly 1994 to March 1995, Parnes & Mopre performed the FGI. The survey d~ta set consists of ,over )5 ,000 instrument readings in three modes and analysis of ov~ 200 soil *samples. The surface tµ'ea surveyed contained over 1500 10 rn x lO m grids in the 46-ac.re focus at¢a. Leyels of Cs-'137 conc~ntrati9n in the surface layer of soil based ort the average ac;tj.yity in each iO m x 10 rn grid are shown in Figure 4-6. Observed 11evels ranged from 3.3 +/- 1.4 pCi/g to 34.7 + 8.2 pCi/g. Where *the surface area had been disturbed by cultural impacts, the Cs-137 was only slightly distingi,tlsnabl~ from ambient gamma radiation background. Within the woodlands undisturbed since 1968, thiS survey delineated an area with statistically elevated Cs"-137, similar to the area identified in the aerial survey of 1984, as displayed in Figure 4-11. WNYNSC Off-Site Radiation Investigation 6-2 April 20, 199~
- Soil. sampling at locations in the study area ind!cated that Cs-137 activity is associa~ed With the organic humus. layer on the ground surface. ln the study region, this surface layer is approximately 2"-4" (5-10 ctn) thick, ly!ng on more impermeal:>le clay below.
- Soil radioactivity analysis indicated a variable local distribution of the observed activity~ the Cs-137 concentration might vary by a factor of 2 to 3 within a meter or two horizontal displacement. This variation appeared to be due to local surface effe¢ts, e.g. driplines from ~ees and limited variations in thickness of the humus, rather than isolated particles of higher activity.
Walkover surface scans in the FGI indicated that 1197 lOm x lOm grids did not h.ave anamolous point sources of Cs-137 or "hotspots". The walkover s:urvey identified 22 grids where the peak count rate was greater than three times the average cm,tnt rate, and there were 95 grids which could not be evaluated due to data quality rejection. These grids need further evaluation in order to verify and quantify the absence of any hotspots of radioactivity~
- The gamma radiation dose rate survey results indicated that there were two
- *i
'I ',_ j localized regions in the study area in whiCh the dose r~te w45 1.2 to 1.5 microrem/hour greater than the ambient background of 3. 7 microrem/hour. This level of e~temal gamma radiation dose rate is within the variation of dose rate reported around the WNYNSC by previous aerial surveys (EG&G,. 1991).
- The local variations in soil radioactivity appeared within the broad gaus~ian q
- .! pattern of deposition from .an airborne plume~ on a lar~e seal~, the Cs-137 concentration decreased with distance from the* peak value along the central radial; and it decreased with distance away from the central radial of the deposit.
Local terrain and surface characteristics had minor influence on the gaussian pattern. WNY'NSC Off-Site Radiation Investigation 6-3 April 20, 1995 .I 1.
- 1
....I The contours of the Cs-137 soil coneentra.tion from this survey are compared to the contours of the previous aerial survey in Figure 4-11. The deposition area is consistently located, within the uncertainties associated with each of the surveys.
6~3 DOSE ASSESSMENT ~] The dose asse5sment for the WNYNSC Off-Sit~ Radiatioh Investigation was performed f-1. i! .* to detennine a potential radiation dose to an individual in the FGI study area due to the concentration of radioactive Cs-137 in the soil.. The. dose assessment process uses the measured activity in the $Oil anq conservative assumptions on individual exposure and land uses to develop an estimate of-the expected dose to the individual. PlauS!ble scenarios of current and future land use we~identi.fied. the critiqal scenario parameter v~ues and. corresponding dos~ *we~e summarized in Table ~,..s. Doses, calculc:tted with the REsRAD environmental tran~port and dosimetry computer code, indicated *that
- Th current land uses tinder both realistic and .conservative scenario assumptions, potential annual doses f<;>r the maximi:Uly exposed individual are below 5 mrem in the current _year.
n
'L J
- Iil future lam!. uses., .only the triQst conservative scenario assumption (the scenatib acre area of tl1e in which a re5idertce house trailer is logi.ted in the highest 0.6 contamination contours) reswts in a potential annual dose to the maximally exposed individual b_elow 8 mrem in the current year.
Du~ to the decay of Cs-137 with a half-.life of 30.2 years, annual doses in subsequent years will naturally decrease by 2.2 percent each year,
- l
!~
.;_J j WNYNSC Off-'Site Radiation 'investigation
*. l 6-4 Aprjl 20, 1995
"'- j i
l _J
The calculated upper bound doses are in the range of doses suggeste4 by proposed federal decommissioning criteria (15 mrem per year) and state guidance (10 mrem per year) as discussed in S_ection 2 (EPA, 1994; NRC, 1994; NYSDEC, 1993). The doses are considerably below the 100 mrem per year dose limit recommended by the NCRP (NCRP, 1987a) IDJ.<:l are only a small fraction of 290 mrem per year, the average annual background radiati.Qn in the U.S. (NCRP, 1987). WNYNSC Off-'Site Radiation Iri.vestigation 6-5 April 20, 1995
lJ ll
"~.
I i
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;1 I
I
Section 7 REFERENCES D&M 1994a Dames & Moore, "Technical Work Plan for the Cesium Prong Investigation, January, 1994. 11 D&M 1994 Dames & Mor;:>re, "Technical Work .Plan: wNYNSC Off-Site Radiation Investigation," September, 1994. DOE 1993 U.S. Depruiment of Energy, "Manual For Implementing Residual
~dioacti.ve Material Guidelines Using RESRAD," Version 5,0S.
*September 1993.
EG&G 1981 U.S. DOE Remote Sensing Laboratory, "A Comparison of Aerial Ra<;liofogical Survey Results of the Nuclear Fuel Services (NFS) and Surrounding Area." Report EG&G # EP-FOOl. June, 1981 EG&G 1991 U.S. DOE Remote Sensing Laboratory, "An Ae.rial Radiolog~cal Survey of the West Valley Demonstration Projeet ano Surrounding Area." Report EGG-10617-:-1080, September 1991. [This 1991 report presents tile results of the aerial survey conducted in Aug-Sep 1984]. EPA 1994 U.S. Environmental Protection Agency; "Technical Summary Report Supporting the Development of Standards for the Cleanup of Radioactively Contaminated Sites (DRAFT)," Washington, DC,. April 1994. NAS 1990 National Academy of Sciences - Nc;tiQilal Research Council, "Bealth Effects of Exposure to Low Levels .of Ionizing Radiation (BEIR V)," Washington, DC, 1990. NCRP 1987a National Council on Radiation Proteetiqn and Measurements, "Recommendations on Limits for Exposure to Ionizing Radiation,,; NCRP Report No. 91, Washington, DC, 1987 . NCRP 1987b National Council on Radiation Protection and Measurements, Ionizing Radi~tion Exposure of the Population of the United States," NCRP Report No. 93, Washington, DC, 1987 *. ~s 1968 Nuclear Fuel Services, Inc., "A Study of Particulate Release Rate During the Period March 8-IO, 1968," West Valley, NY, March 24, 1968. WNYNSC Off-"Site Radiation Investigation 7-1 April 20, 1995
NRC 1992a U.S. Nuclear.Regulatory Commission, "Action Plan to Ensure Timely CI~armp of Sfte D~commis~ioning Manag~ment Plan Site5," NUREG/BR-0117, No. 92~2, June 1992. NRC 1992b U,S. Nuclear Regulatory Commission; "Manual for Conducting Radiological Surveys in Support of License Termination (DRAFT)," Report NUREQ/CR-5849, 1992. - NRC 1994a U.S. Nuciear Regulatory Commission, *~scenarios for Assessing Potenti~ Doses Associated witjl Residual Radioa.ctivity," Policy and Guidance Directive PG-808, Washington, DC, May f 994. NRC 1994b U~S. Nucleat Regulatory Commis~ion, 1'Radiologi_cal Cri~etia for Decommissioning .,. Proposed Rule,"_ Federal Register, August 22, 1994, Part m: p~ges 43200-43232. NYSDEC 1972 Letter, William Bentley to Commissioner Diamond, Jtily 7, 1972,
,; 1_9_71 Aruitial ~eport of Env,i+onm~pthl Radi~tion in New Yorlc State. 11 NYSD'.EC 1993a NYS Department of Envfronmental Conservation, ;'Technical Ad(niilistrative Gt1id~ce Memorandum No 4003, Subje~t: Cleanup Guidelines for Soils Contaminated with -Radioactive Mater.l,µ.s. ,;
September 14, i993. NYSDEC 19931:) NYS Department of Environmental Conservation, Letter Thomas c. f; l Joi:ling to U.S. Nuclear Regulatory Commission, Albany, NY, u October 1, 1993. SAIC 1994 SAIC, Inc~, Letter, .Ken Toney(SAIC) to Patti Swain (WVDP), 0 Particulafo Releases_ fr()m the Process Building Stack, 1966-1972." WVD'.P 1982 West Valley Demonstration Project, "Environmental Characterization of the Nuclear Fuel Reprocessing Pla,nt ~t West Valley, NY (Pre-solidification Baseline)," Report WVDP:014, October, 1982. WVDP 1992 W~t Valley Demonst#tion Projec~, "Site Environmental Report - 1992j , 1993. 1 1.l WNYNSC Off-Site Radiation Investigation 7-2 April 20, 1995}}