RADIATION ANALYSIS OF A SPENT-FUEL STORAGE CASK

Transcription

1 RADIATION ANALYSIS OF A SPENT-FUEL STORAGE CASK by J.K. Shultis Department of Mehanial and Nulear Engineering Kansas State University Manhatta, Kansas published as Report 290 ENGINEERING EXPERIMENT STATION College of Engineering Kansas State University Manhattan, Kansas January 2000

2 Radiation Analysis of a Spet-Fuel Storage Cask by J.K.Shultis Dept. Mehanial and Nulear Engineering Summary This report desribes MCNP alulations of the neutron and gamma-ray doses rates arising from a single Transnulear spent-fuel storage ask holding 68 design-basis fuel assemblies (a TN-68 ask). Calulations of radiation fields both near the ask and at distanes up to 1000 m from the ask are reported. These external dose rates are reported for both primary gamma rays (arising from fission and ativation produts in the spend fuel and from ativation produts in the assembly end fittings and plenum) and from neutrons emitted by the transurani isotopes and (α, n) reations in the spent fuel. Dose rates 4.5 inhes from the ask surfae and doses 1-m above grade out to 1000 m are reported. For the far-field dose rates, the skyshine dose rate omponents are separated from the total dose rates. In addition, seondary-photon dose rates are also reported both at the ask surfae and at large distanes from the ask. Results, both with and without an earthen berm at 30 m from the ask, are presented. 1 MCNP Modeling of the TN-68 Cask 1.1 Geometry Models The MCNP [Br97] models of the TN-68 ask developed in this study are based on the SAS4 model (Figs and 5.3-2) provided by Transnulear [Ma98a]. The basi ask struture in shown in Fig. 1. An analog model of the TN-68 ask for the neutron dose alulations was used (i.e., eah ask omponent was modeled by a single MCNP ell). However, for the gamma-ray doses this analog geometry model proved insuffiient, and it was neessary to subdivide the iron ask body into multiple ell sublayers with inreasing photon importanes for the outer layers in order to bias photon transport to the outside of the ask. In partiular, 10 sublayers for the ask body were used, as shown in Fig. 2. An important simplifiation in the MCNP model was to homogenize the fuel and holding basket within the ask. This represents an enormous simplifiation sine the detailed modeling of eah fuel pin and the basket struture would have produed an MCNP model with great geometri omplexity and one whih would have run prohibitively slowly. 1.2 Material Compositions The elemental and/or isotopi ompositions of the various materials used in the TN-68 ask are given in Table 1. The data for this table were provided by Transnulear [MA98a], in part, by Table 1

3 void polypropylene shield ask lid top fitting plenum & basket ative fuel and basket resin/aluminum shield ask body ask body bottom fitting ask body Figure 1. The TN-68 ask showing the prinipal material omponents. 2

4 air void polypropylene shield top fitting plenum & basket fuel zone 10 fuel zone 9 fuel zone 8 resin/aluminum shield Figure 2. The MCNP geometry model for the TN-68 ask in whih the iron wall, top and bottom of the ask are split into 10 sublayers for the SAS4 model. Material ompositions for the air, soil, berm and onrete were taken from the referenes indiated in Table Cask Soure Terms Gamma Photons The gamma-ray soure strengths were provided by Transnulear [Ma98b]. To aount for the varying burnup along the length of the fuel assemblies, the ative fuel zone in the MCNP was divided into 10 separate axial zones. In addition to gamma radiation from the fuel, ativation gamma photons were emitted from the end fittings and the plenum. The gamma-ray soure spetra and soure strengths for the TN-68 ask are tabulated in Tables 2 and 3. Although, the gamma soure ativity for the fittings/plenum is onsiderably less than that for the fuel, the top fitting/plenum being loser to the ask top might be expeted to ontribute more to the leakage dose than gammas from the fuel. To assess the relative importane of the fitting/plenum and the fuel gamma rays, separate soure models were used for these two gammaray soures and near- and far-field dose alulations were run for eah soure region. 3

5 Table 1. Composition of materials used in the MCNP models of the TN-68 ask. Shown are the elemental (or nulide) or atomi fration (positive) or mass fration (negative), w i of eah omponent. Values for TN-68 ask materials are derived from Table Materials Input for SAS4 and SAS1 Model. Element & w i Element & w i Element & w i Element & w i Element & w i Dry Air: ρ = g/m 3 [ANSI/ANS 6.4.3] 14 N O C Ar Conrete: ρ =2.32 g/m 3 [ANSI/ANS 6.4.3] 1 H O Na Mg Al Si S K Ca Fe Soil: ρ =1.625 g/m 3 [Jaob, Prot. Dos., 14, 299, 1986] 1 H C K Fe Ca Al Si O Fuel-Basket Homogenized TN-68 Cask: ρ =3.231 g/m U U Zr Ni Fe Mn Cr Al O Plenum/Basket TN-68 Cask: ρ =1.158 g/m 3 Fe Ni Mn Cr Zr Al Top Fitting TN-68 Cask: ρ =0.491 g/m 3 Fe Ni Zr Mn Cr Bottom Fitting/Basket TN-68 Cask: ρ =1.918 g/m 3 Fe Ni Mn Cr Zr Al Basket Periphery (stainless steel): ρ =7.92 g/m 3 Fe Cr Ni Mn Periphery Shim/Rails TN-68 Cask (aluminum): ρ =2.702 g/m 3 27 Al Cask Body TN-68 Cask (arbon steel): ρ = g/m 3 Fe C Polypropylene Disk TN-68 Cask: ρ =0.90 g/m 3 12 C H Resin/Aluminum TN-68 Cask: ρ =1.687 g/m 3 27 Al C O B H B Berm (Silia + water): ρ =1.400 g/m 3 Si O H

6 Table 2. Energy spetrum of gamma photons emitted by the spent fuel and by the fittings/plenum. Soure strengths are the number of photons emitted per seond per assembly. Energy Energy range Number of Photons Group (MeV) (s 1 assembly 1 ) Fration Spent Fuel: to to to to to to to to to Total Top Fitting: to to Total Plenum: to to Total Bottom Fitting: to to Total Table 3. Axial distribution of the gamma-ray soure strength in the 10 fuel zones. Axial ranges are with respet to the enter of the fuel. Fuel Axial Range Fration of Total Zone (m) Fuel Photons to to to to to to to to to to Total

7 1.3.2 Neutrons Transnulear In. provided neutron soure strengths and energy spetrum for a 7 7 assembly with 40,000 MWd/Mt average burnup with a 10-year ooling time [Ma99]. The energy spetrum of the neutrons emitted from the spent fuel are given in Table 4. The variation in burnup along the axis of the fuel assembly is modeled by dividing the assembly into 12 axial zones. The fration of neutrons emitted by eah axial zone is listed in Table 5. Table 4. Energy spetrum of neutrons emitted by the spent fuel and by the fittings/plenum. Soure strengths are the number of neutrons emitted per seond per assembly. Energy range Number of Neutrons (MeV) (s 1 assembly 1 ) Fration 6.34 to to to to to to to Total Table 5. Axial distribution of the neutron soure strength in the 12 fuel zones. Axial ranges are with respet to the enter of the fuel. Fuel Axial Range Fration of Total Zone (m) Fuel Neutrons to to to to to to to to to to to to Total

8 1.4 Dose Conversion Fators The fluene-to-dose onversion fators inorporated into the MCNP TN-68 ask models were those for the ambient dose equivalent (the dose equivalent at 10-m depth in the ICRP spherial phantom illuminated by a plane-parallel beam of radiation inident on the sphere) [IC87, Sh96]. These dose onversion fators are listed in Table 6. Table 6. Response funtions (fluene-to-dose onversion fators) used in the MCNP analyses. These fators yield the ambient dose equivalent at 10-m depth inside the ICRU sphere (human-phantom approximation) for the ase of a plane parallel beam inident on the sphere. Photon energy Response Funtion Neutron energy Response Funtion (MeV) (10 12 Sv m 2 ) (MeV) (10 12 Sv m 2 ) Soure: ICRP [1987]. Sine MCNP yields results normalized to one soure partile, it is neessary to onvert the MCNP alulated dose D(Sv/partile) to an appropriate dose rate, here taken as D(mrem/h). This is aomplished with D(mrem/h) = D(Sv/partile) S i (partiles/s) 10 5 (mrem/sv) 3600(s/h), (1) where S i (partiles/s) is the total partile emission rate from the ith soure region when the ask is fully loaded with 68 assemblies. 7

9 1.4.1 Dose-Rate Conversion Fators for Primary Gamma Rays From Table 2 the total number of gamma photons emitted by the fuel zones, per assembly, is s 1. Thus, S γf = = photons/s. Finally, from Eq. (1) one has D γf (mrem/h) = D γf (Sv/photon). (2) Similarly, the total gamma soure strength for the top and bottom end fittings and the plenum region is S γx = = photons/s, and the dose-rate onversion fator beomes D γx (mrem/h) = D γx (Sv/photon). (3) These dose-rate onversion fators an be inorporated into the MCNP model by using a tally multiplier FM ard Dose-Rate Conversion Fators for Neutrons and Seondary Photons From Table 4 the total number of neutrons emitted by the fuel zones, per assembly, is s 1. Thus, S n = = neutrons/s. Finally, from Eq. (1) one has D n (mrem/h) = D n (Sv/neutron). (4) This result is also used to onvert the MCNP-alulated doses for seondary photons. 2 Near-Field Gamma Dose Rates The 10-sublayer TN-68 ask model of Fig. 2 was plaed on a onrete pad and surround by a void. A horizontal detetor surfae was plaed 4.5 inhes above the top protetive over and a ylindrial detetor surfae was plaed 4.5 inhes outside the radial ask shield. 1 These detetor surfaes were further subdivided into segments, and the F2 surfae tally was used to obtain the dose averaged over eah surfae segment. The resulting dose rates are given in Tables 7 and 8 and shown shematially in Fig. 3. These results were obtained with the MCNP input files GNFB2X.I and GNFB2F.I for the fuel photons and for the fittings/plenum photons, respetively. It is interesting to note that most of the gamma dose-rate esaping through the upper orner of the ask and through the ask top is due to photons emitted by the plenum/top-fitting region. By ontrast, along the radial shield, photons emitted by the fuel are the dominant omponent of the leakage dose rate. 3 Far-Field Gamma Dose Rates The 10-sublayer ask model of Fig. 2 was plaed on a flat onrete pad whih extended 10 m from the ask axis. Beyond the onrete pad, standard soil was used for a ontinuation of the flat ground surfae. Dry air, of density g/m 3, was used above the ground interfae. To sweep photons outwards, the air was subdivided into many radial ells with ell importanes inreasing with inreasing distane from the ask. Annular detetor volumes of air, 2-m high and 0.5 or 1-m thik, were plaed on the ground interfae at multiple distane ranging from 2 to 1000 m from the ask axis. The MCNP F4 volume tally was used to obtain the dose in these air-phantom representation of a human. 1 The 4.5-inh distane represents the enter of a 9-inh remball, whih is often used for neutron surveys at ontat. 8

10 Figure 3. The primary gamma dose rate at various positions around the TN-68 ask at 4.5 inhes from the ask surfae. 9

11 Table 7. Primary gamma-ray dose-equivalent rates as a funtion of elevation at a distane of 4.5 inhes from the TN-68 ask radial surfae. Elevation Fittings/Plenum Fuel Total Dose from fuel enter (m) (mrem/h) error (mrem/h) error (mrem/h) Table 8. Primary gamma-ray dose-equivalent rates along the TN-68 ask top (4.5 inhes from the top surfae). Radial dist. Fittings/Plenum Fuel Total Dose from fuel enter (m) (mrem/h) error (mrem/h) error (mrem/h) To obtain the skyshine omponent of the far-field dose rate, two MCNP alulations were performed: one using the above model to obtain the total (diret+groundshine+skyshine) dose rate, D t, as a funtion of distane from the ask, and a seond using the same MCNP model, but with the air above the elevation of the ask top replaed by a void. The doses obtained with this seond alulation eliminated the skyshine omponent, leaving only the diret plus groundshine, D d. Thus the differenes between these two alulations yields an estimate of the skyshine dose. The skyshine dose rate, D s is then alulated as D s =(D t D d ) ± r s. (5) 10

12 The relative error or unertainty r s is obtained by the standard propagation of errors as rt 2 r s = D2 t + r2 d D2 d (D t D d ) 2, (6) with r t and r d the (1-sigma) relative error in the total and diret dose rates, respetively. Near the ask, the diret omponent dominates and the two alulated values will be nearly equal, yielding a skyshine estimate with relatively large unertainties. At large distanes from the ask, however, the diret omponent is severely attenuated, and the total dose is dominated by the skyshine omponent so that the differene between the two alulated values yields a very aurate estimate of the skyshine field. 3.1 Cask without a Berm Far-field alulations of the primary gamma-ray dose rates for the fuel and fittings/plenum gamma soure terms were performed separately. MCNP input files GFFAF.I and GFFAX.I were used to determine the total dose rate (diret+groundshine+skyshine) for the fuel photons and for the plenum/fittings photons, respetively. The orresponding diret plus groundshine doses were obtained with the MCNP input files GFFAFO.I and GFFAX0.I. These fuel and plenum/fitting omponents were then added to yield total gamma-ray dose rates using formulas analogous to Eqs. (5) and (6). The resulting far-field dose rates and the derived skyshine dose rates are presented in Table 9 and shown graphially in Figs. 4 and 5. Table 9. Primary gamma-ray dose-equivalent rates as a funtion of the distane from the TN-68 ask. Cask is on an infinite plane surfae without any intervening berm to blok the diret omponent. Distane Total Dose Diret Dose Skyshine Dose from ask axis (m) (mrem/h) error (mrem/h) error (mrem/h) error E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E In Fig. 4 the total dose rate (diret+groundshine+skyshine) is shown together with its two omponents, namely, the total dose produed by the fuel gamma-rays and by the fittings/plenum 11

13 Figure 4. The total primary gamma-ray dose at 1-m above the ground and the ontribution made by the two soure omponents. Figure 5. The total, diret, and skyshine dose rates from primary gammarays at 1-m above grade. 12

14 gamma rays. It is observed that for a human phantom standing on the ground near the ask, the gamma-rays emitted by the fuel are the major ontributor to the total dose rate sine the leaking plenum/top-fitting, whih have a greater intensity, are emitted primarily from the top orner of the ask above the human. However, beyond about 10 m, the gamma-rays emitted by the plenum/fittings beome slightly more dominant. In Fig. 5 total dose rate from primary gamma rays is shown along with the diret (inluding groundshine) and derived skyshine dose rates. As expeted, the skyshine omponent beomes dominant at large distanes from the ask and, beyond several hundred meters, omprises almost all the dose rate. 3.2 Berm Around Cask Calulations were performed with an 8-foot thik and 20-foot high berm plaed around the TN-68 ask. The berm was entered 30 m from the ask axis. This berm was slightly taller than the ask and thus ollimated any skyshine radiation from the ask into an upward one with a half angle of between 88.8 degrees (for radiation emitted from the top of ask) to 78.5 degrees (from radiation emitted by the bottom of the ask). The total and diret dose rates were performed with the MCNP input files GFFBF.I and GFFBF0.I, respetively, for the fuel emitted photons and with GFFBX.I and GFFBX0.I, respetively, for the fittings/plenum emitted photons. Results are presented in Table 10 and Fig. 6. No photon sores were observed beyond the berm, an indiation of the effetiveness of the berm in stopping all diret gamma radiation. Beyond the berm only skyshine ontributes to the dose rate. In Fig. 6 the total and skyshine dose rates for a ask without a berm are also shown by the dashed lines. It is seen that, beyond the berm, the total dose rate for a berm is slightly below but parallel to the no-berm skyshine dose-rate profile. This slight depression is a result of the berm ollimating the esaping radiation from the ask into an upward onial beam with a full-angle slightly less than the 2π geometry of the no-berm ase. Also in front of the berm, the berm is seen to at as a refletor, slightly enhaning the total dose rate over that for the no-berm ase. 13

15 Figure 6. The total primary gamma-ray dose rate (solid line and irles) at 1-m above the ground with a 20-foot berm present. Also shown by dashed lines are the total and skyshine dose rates without a berm. 14

16 Table 10. Primary gamma-ray dose-equivalent rates as a funtion of the distane from the TN-68 ask. Cask is on an infinite plane surfae with an 8-foot thik intervening berm at 30 m from the ask axis. Distane Total Dose Diret Dose Skyshine Dose from ask axis (m) (mrem/h) error (mrem/h) error (mrem/h) error E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E

17 4 Near-Field Neutron Dose Rates The analog model of Fig. 1 was used to estimate the neutron dose rates and the seondary-photon dose rates 4.5-inhes from the ask side and 4.5 inhes above the ask top. These alulations were performed with the MCNP input file NGNF2.I. Results are shown shematially in Fig. 7 and tabulated in Tables 11 and 12. Table 11. Neutron and seondary-photon doseequivalent rates as a funtion of elevation at a distane of 4.5 inhes from the TN-68 ask radial surfae. Photon dose rates arise only from neutron interations in the ask; no prodution of photons in the surrounding air is inluded. Elevation Neutrons Seondary Photons from fuel enter (m) (mrem/h) error (mrem/h) error Table 12. Neutron and seondary-photon doseequivalent rates along the TN-68 ask top (4.5 inhes from the top surfae). Photon dose rates arise only from neutron interations in the ask; no prodution of photons in the surrounding air is inluded. Radial dist. Neutrons Seondary Photons from fuel enter (m) (mrem/h) error (mrem/h) error

18 Figure 7. The neutron and seondary-photon dose rate at various positions around the TN-68 ask at 4.5 inhes from the ask surfae. 17

19 5 Far-Field Neutron Dose Rates The same MCNP model used for the far-field gamma-ray analysis was also used for the far-field neutron alulations, exept that the ten-layer ask model was replaed by the analog model of Fig. 1. Sine the iron is not nearly as effetive at stopping neutrons, a simpler and more omputationally effiient model was justified. The MCNP importanes of the radial air ells were adjusted to optimize the neutron population as it migrated away from the ask. No attempt was made to develop separate importanes for the seondary photons; rather, the same ell importanes were used for both neutrons and photons. Two far-field geometries were onsidered: a ask on a flat infinite plane without any surround berm, and a ask with an 8-foot thik berm plaed 30 m from the ask axis. 5.1 Cask Without a Berm The simulation of the TN-68 ask without a berm was performed with the MCNP input file NGFFA1.I to produe both the total neutron dose (diret + groundshine + skyshine) as well as the dose from seondary photons. No attempt was made to distinguish between seondary photons produed in the ask materials and photons produed in the air and soil. To extrat the skyshine omponent of the neutron dose, alulations were made using the MCNP file NFFA0.I in whih the air above the ask was replaed by a void. The neutron doses obtained from this simulation onsist of only the diret plus groundshine omponents. Thus the differene between this two sets of neutron doses yields the skyshine omponent. Errors for the skyshine omponent were obtained in the same manner previously desribed for the gamma-ray skyshine alulation. The neutron and seondary photon dose rates obtained with MCNP are listed in Table 13 and shown in Fig. 8. As expeted, at large distanes (greater than a few hundred meters), the total neutron dose is dominated by the skyshine omponent. Finally, in Fig. 9 the dose rates are shown for the primary gamma photons, the neutrons, and the seondary photons. The primary gamma dose is seen to be about ten times larger than the neutron dose. 5.2 Cask Surrounded by a Berm The MCNP file NGFFB1.I was used to determine the neutron and seondary-photon dose rates out to 1000 m. Results are presented in Table 14 and show in Figs. 10 and 11. From Fig. 10 it is seen that the berm is very effetive at stopping the diret plus groundshine omponents. Outside the berm, the total neutron dose rate is entirely omposed of skyshine neutrons. The seondary-photon dose rate, shown in Fig. 11, arises from neutron interations both in the ask and in the surrounding air. However, both inside and outside the berm, the seondary-photon dose shown in this figure is dominated by the seondary photons reated in the ask material. The solid line before the berm is primarily due to the diret ontribution of the seondary photons produed in in the ask, while the solid line beyond the berm is a result of the skyshine of these seondary photons. The ontribution from the seondary photons produed in the air is minor, representing, for example, only about 10% of the total seondary-photon skyshine dose at 50 m. 18

20 Figure 8. The total, diret and skyshine omponents of the neutron ambient dose equivalent rate 1-m above the ground. Figure 9. The three omponents of the total dose rate for the TN-68 ask at 1-m above grade without a berm present. 19

21 Figure 10. The total neutron ambient dose equivalent rate (solid line and irles) 1-m above the ground when the ask is surrounded by a berm at 30 m. Shown by the dashed lines are the total and skyshine dose rates without the berm. Figure 11. The seondary-photon dose rate at 1-m above grade with a berm present (solid line and irles) and without a berm (dashed line). 20

22 Table 13. Neutron and seondary-photon dose-equivalent rates as a funtion of the distane from the TN-68 ask. Cask is on an infinite plane surfae without any intervening berm to blok the diret omponent. Neutron Seondary photon Distane from ask Total Dose Diret Dose Skyshine Dose Total axis (m) (mrem/h) error (mrem/h) error (mrem/h) error (mrem/h) error E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E Table 14. Neutron and seondary-photon dose-equivalent rates as a funtion of the distane from the TN-68 ask. Cask is on an infinite plane surfae with a berm 30 m from the ask to blok any diret omponent. Distane Total Neutron Seondary Photon from ask axis (m) (Sv/neutron) (mrem/h) error (Sv/neutron) (mrem/h) error E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E

23 REFERENCES Briesmeister, J.F., Ed., MCNP A General Monte Carlo N-Partile Transport Code, Version 4b, LA M, Los Alamos National Laboratory, ICRP, Data For Use in Protetion Against External Radiation, Report 51, International Commission on Radiologial Protetion, Pergamon Press, Oxford, ICRP, Conversion Coeffiients for Use in Radiologial Protetion against External Radiation, Report 74, Annals of the ICRP, Vol 26, No. 3/4 (1996). Mason, M., FAX to J.K. Shultis, 12/17/98, 1998a. Mason, M., FAX to J.K. Shultis, 12/23/98, 1998b. Mason, M., to J.K. Shultis, 1/13/98, NCRP, Protetion Against Neutron Radiation, Report 38, National Counil on Radiation Protetion and Measurements, Washington, D.C., Shultis, J.K., and R.E. Faw, Radiation Shielding, Prentie-Hall, Upper Saddle River, New Jersey,

24 Apprendix: Listing of Sample MCNP Inpout Files For the MCNP alulations reported here, many input files and models were developed. In partiular the following input files were used. GNFB2X.I* near-field analysis for gamma rays from the end fittings GNFB2F.I near-field analysis for gamma rays from the fuel NGNF2.I near-field analysis for neutrons from the fuel GFFAF0.I far-field diret omponent for gamma rays from the fuel (no berm) GFFAF.I* far-field diret plus skyshine for gamma rays from the fuel (no berm) GFFAX0.I far-field diret omponent for gamma rays from end fittings (no berm) GFFAX.I far-field diret plus skyshine for gamma rays from end fittings (no berm) NGFFA0.I far-field diret omponent for fuel neutrons (no berm) NGFFA1.I far-field diret plus skyshine for fuel neutrons (no berm) GFFBF0.I far-field diret omponent for gamma rays from the fuel (with a berm) GFFBF.I far-field diret plus skyshine for gamma rays from the fuel (with a berm) GFFBX0.I far-field diret omponent for gamma rays from end fittings (with a berm) GFFBX.I far-field diret plus skyshine for gamma rays from end fittings (with a berm) NGFFB.I far-field diret omponent for fuel neutrons (with a berm) NGFFB1.I* far-field diret plus skyshine for fuel neutrons (with a berm) On the following pages, the three MCNP input files marked by an * are listed. The other input files are redily onstruted from the omponents listed in the three example files. 23

25 File GNFB2X.I TransNulear TN-68 ask: Near-field gamma doses. Soure: fittings & plenum. Air replaed by void. Surfae F2 detetors used for doses outside ask. Cask s iron shell is deomposed into 10 sublayers and importanes are used to sweep photons through ask sublayers. *********************** BLOCK 1: CELL CARDS ************************ GEOMETRY (r-z) ^ z-axis. tally surfaes BASKETS +... VOID.. FUEL O > y-axis (10 sub. regions)..... BASKET = CONCRETE J.K. Shultis (12/26/98) ****** Cask ells deomposed ase bottom into 10 sublayers imp:n,p=1024 $ Fe ask bot-sublayer imp:n,p=512 $ Fe ask bot-sublayer imp:n,p=256 $ Fe ask bot-sublayer imp:n,p=128 $ Fe ask bot-sublayer imp:n,p=64 $ Fe ask bot-sublayer imp:n,p=32 $ Fe ask bot-sublayer imp:n,p=16 $ Fe ask bot-sublayer imp:n,p=8 $ Fe ask bot-sublayer imp:n,p=4 $ Fe ask bot-sublayer imp:n,p=2 $ Fe ask bot-sublayer 10 deompose ask side into 10 sublayers imp:n,p=2 $ Fe ask side-sublayer imp:n,p=4 $ Fe ask side-sublayer 2 24

26 imp:n,p=8 $ Fe ask side-sublayer imp:n,p=16 $ Fe ask side-sublayer imp:n,p=32 $ Fe ask side-sublayer imp:n,p=64 $ Fe ask side-sublayer imp:n,p=128 $ Fe ask side-sublayer imp:n,p=256 $ Fe ask side-sublayer imp:n,p=512 $ Fe ask side-sublayer imp:n,p=1024 $ Fe ask side-sublayer 10 deompose ask lid into 9 sublayers imp:n,p=4 $ Fe ask lid-sublayer imp:n,p=8 $ Fe ask lid-sublayer imp:n,p=16 $ Fe ask lid-sublayer imp:n,p=32 $ Fe ask lid-sublayer imp:n,p=64 $ Fe ask lid-sublayer imp:n,p=128 $ Fe ask lid-sublayer imp:n,p=256 $ Fe ask lid-sublayer imp:n,p=512 $ Fe ask lid-sublayer imp:n,p=1024 $ Fe ask lid-sublayer 9 other ask ells imp:n,p=1 $ bottom basket imp:n,p=2 $ top plenum basket imp:n,p=2 $ top fitting imp:n,p=2 $ ss side basket imp:n,p=2 $ Al side basket/rails imp:n,p=2 $ top void - part #10 imp:n,p=2 $ top void - part imp:n,p=2 $ hold down ring imp:n,p=1024 $ polyprop top shield imp:n,p=1024 $ void under top over -pt imp:n,p=1024 $ void under top over -pt imp:n,p=1024 $ top Fe over - top imp:n,p=1024 $ top Fe over - side imp:n,p=1024 $ top side-shld Fe shell imp:n,p=1024 $ side side-shld Fe shell imp:n,p=1024 $ bot side-shld Fe shell imp:n,p=1024 $ side resin/al shield imp:n,p=1024 $ void under side shld imp:n,p=1024 $ void above side shld - pt imp:n,p=1024 $ void above side shld - pt2 **** fuel regions imp:n,p=1 $ FUEL region 1 (bottom) imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region 10 (top) ***** outside ells above/below ask 25

27 imp:n,p=1024 $ onrete beneath ask imp:n,p=1024 $ air above ask-pt imp:n,p=1024 $ air above ask-pt2 ***** Cells outside radial ask surfae imp:n,p=1024 $ onrete inner air imp:n,p=1024 $ inner air (void) imp:n,p=1024 $ inner air (void) imp:n,p=1024 $ inner air (void) imp:n,p=1024 $ onrete outer air imp:n,p=1024 $ outer air (void) imp:n,p=1024 $ outer air (void) imp:n,p=1024 $ outer air (void) :151:152 imp:n,p=0 $ problem boundary *********************** BLOCK 2: SURFACE CARDS ************************ **** Horizontal ask planes 1 pz $ ask bottom - ground surfae 110 pz $ ask bottom - top of sublayer pz $ ask bottom - top of sublayer pz $ ask bottom - top of sublayer pz $ ask bottom - top of sublayer pz $ ask bottom - top of sublayer pz $ ask bottom - top of sublayer pz $ ask bottom - top of sublayer pz $ ask bottom - top of sublayer pz $ ask bottom - top of sublayer 2 2 pz $ ask bottom - top of bot Fe plate 3 pz $ side Fe jaket - outside lower bottom 4 pz $ side Fe jaket - inside lower bottom 5 pz $ top bottom basket/bottom of fuel 7 pz $ bottom of plenum basket/top of fuel 8 pz $ top of plenum basket 9 pz $ side Fe jaket - inside top 10 pz $ side Fe jaket - outside top 11 pz $ top of top fitting 12 pz $ ask top - bot of lid 122 pz $ ask top - top of sublayer pz $ ask top - top of sublayer pz $ ask top - top of sublayer pz $ ask top - top of sublayer pz $ ask top - top of sublayer pz $ ask top - top of sublayer 9 14 pz $ ask top - top of lid 13 pz $ ask side - top of Fe side 15 pz $ top of polyprop on top of ask 16 pz $ top Fe over - bot surfae 17 pz $ top Fe over - top surfae 18 pz $ top over flange 19 pz $ top hold down ring 28 pz $ bottom hold down ring ***** ylindrial ask surfaes 26

28 201 z $ ask wall - inner surfae 202 z $ ask wall - inner surfae of sublayer z $ ask wall - inner surfae of sublayer z $ ask wall - inner surfae of sublayer z $ ask wall - inner surfae of sublayer z $ ask wall - inner surfae of sublayer z $ ask wall - inner surfae of sublayer z $ ask wall - inner surfae of sublayer z $ ask wall - inner surfae of sublayer 8 21 z $ ask outer surfae 22 z $ side Fe jaket -- inside 23 z $ side Fe jaket -- outside 24 z $ inside radius of hold down ring 25 z $ top polyprop disk radius 26 z $ inside radius ss basket 27 z $ inside radius Al baket/rails 29 z $ inside radius top over 30 z $ outside radius top over ***** surfaes for fuel regions 40 pz $ top of fuel region pz $ top of fuel region pz $ top of fuel region pz $ top of fuel region pz -0.0 $ top of fuel region pz $ top of fuel region pz $ top of fuel region pz $ top of fuel region pz $ top of fuel region 48 ***** problem boundaries 150 pz -300.E2 $ bottom of soil (problem boundary) 151 pz 500.E2 $ top of air (problem boundary) 152 z 500.E2 $ radial air limit (problem boundary) ****** surfaes for detetor segmentation 60 z $ radial tally surfae 61 pz $ top tally surfae 71 pz $ segmentation plane 72 pz $ segmentation plane 73 pz $ segmentation plane 74 pz 30.0 $ segmentation plane 75 pz 90.0 $ segmentation plane 76 pz $ segmentation plane 80 z $ segmentation ylinder *********************** BLOCK 3: DATA CARDS *************************** volumetri ylindrial soures in ells 3,4,5 for bottom fitting, plenum basket and top fitting SDEF CEL=d1 POS=FCEL d2 AXS=0 0 1 RAD=d9 EXT=FCEL d10 ERG=d14 -- define ells for eah soure SI1 L $ ell: top fit. / plenum / bot. fitting SP $ relative soure strengths 27

29 -- set POS for eah soure DS2 S $ based on ell hoosen, set distribution for POS SI3 L $ enter for spatially sampling of soure 1 (top fit.) SP3 1 $ prob. distn for sr 1 enter SI4 L $ enter for spatially sampling of soure 2 (plenum) SP4 1 $ prob. distn for sr 2 enter SI5 L $ enter for spatially sampling of soure 3 (bot.fit.) SP5 1 $ prob. distn for sr 3 enter -- set RAD for eah soure (must ompletely inlude ells 5, 4 or 3) SI $ radial sampling limits for all 3 soures SP $ radial sampling weight for all 3 soures -- set EXT for eah soure (must ompletely inlude ells 5, 4, or 3) DS10 S $ distns for sampling axially for eah sr SI $ axial sampling limits for sr1 SP $ axial sampling weight for sr1 SI $ axial sampling limits for sr2 SP $ axial sampling weight for sr2 SI $ axial sampling limits for sr3 SP $ axial sampling weight for sr3 -- gamma energy spetrum: same for all three soures SI14 H $ energy bins - same for the 3 soure regions SP $ bin probs. - same for the 3 soure regions ---- Detetor types and loations (F2 segmented surfae detetors) -- doses on ask s radial surfae FC2 Doses 4.5" from ask radial surfae averaged over subsurfaes F2:p 60 $ surfae tally FS SD E E7 TF2 3j 6 -- doses along ask s top FC12 Doses 4.5" from ask top surfae averaged over subsurfaes f12:p 61 $ surfae tally fs sd E9 mode p PHYS:p $ -- no bremsstrahlung, no oherent sattering nps void ambient photon dose equiv. H*(10mm) Sv (from T-D1 of S&F) de E E E E E E-02 28

30 df E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E-11 ***** MATERIAL CARDS ************************************************************ AIR: ANSI/ANS-6.4.3, Dry air; density = g/m^3 Composition by mass fration ************************************************************* m ************************************************************ CONCRETE: ANSI/ANS-6.4.3; density = 2.32 g/m^3 Composition by mass fration ************************************************************ m ************************************************************** SOIL: [Jaob, Radn. Prot. Dos. 14, 299, 1986] density = g/m^3; Composition by mass fration ************************************************************** m ************************************************************** Fuel-Basket TN-68 Cask (Table 5.3-1) 29

31 Density = g/m^3; Composition by atom fration ************************************************************** m ************************************************************* Top Fitting TN-68 Cask (Table 5.3-1) Density = g/m^3; Composition by atom fration ************************************************************* m ************************************************************* Plenum/Basket TN-68 (Table 5.3-1) Density = g/m^3; Composition by atom fration ************************************************************* m ************************************************************* Bottom/Basket TN-68 (Table 5.3-1) Density = g/m^3; Composition by atom fration ************************************************************* m ************************************************************** Basket Periphery (SS304) TN-68 (Table 5.3-1) Density = 7.92 g/m^3; Composition by atom fration ************************************************************** m

32 ************************************************************** Carbon Steel TN-68 (Table 5.3-1) Density = g/m^3; Composition by atom fration ************************************************************** m ************************************************************** Outer Basket/Rails TN-68 (Table 5.3-1) Density = g/m^3; Composition by atom fration ************************************************************** m ************************************************************* Polypropylene Disk TN-68 (Table 5.3-1) Density = 0.90 g/m^3; Composition by atom fration ************************************************************* m ************************************************************* Resin/Aluminum Composite for TN-68 (Table 5.3-1) Density = g/m^3; Composition by atom fration ************************************************************* m ************************************************************* Berm (Silia + water) for ISFSI Site (SAR Page 7a-5); density = g/m^3; Composition by atom fration ************************************************************* m

33 File GFFAF.I TransNulear TN-68 ask: Far-Field model; gammas from fuel zones only. Volumetri F4 detetors used. Geometry splitting/routlette added. NOTE: Dose are from "diret" + "skyshine" radiation. No berm. *********************** BLOCK 1: CELL CARDS ************************ GEOMETRY (r-z) (J.K.Shultis 12/30/98) ^z-axis AIR ask FUEL o > r-axis \. \ det vols (16 in all). CONCRETE SOIL 10m ****** Cask ells deomposed ase bottom into 10 sublayers imp:n,p=1024 $ Fe ask bot-sublayer imp:n,p=512 $ Fe ask bot-sublayer imp:n,p=256 $ Fe ask bot-sublayer imp:n,p=128 $ Fe ask bot-sublayer imp:n,p=64 $ Fe ask bot-sublayer imp:n,p=32 $ Fe ask bot-sublayer imp:n,p=16 $ Fe ask bot-sublayer imp:n,p=8 $ Fe ask bot-sublayer imp:n,p=4 $ Fe ask bot-sublayer imp:n,p=2 $ Fe ask bot-sublayer 10 deompose ask side into 10 sublayers imp:n,p=2 $ Fe ask side-sublayer imp:n,p=4 $ Fe ask side-sublayer imp:n,p=8 $ Fe ask side-sublayer imp:n,p=16 $ Fe ask side-sublayer imp:n,p=32 $ Fe ask side-sublayer imp:n,p=64 $ Fe ask side-sublayer imp:n,p=128 $ Fe ask side-sublayer imp:n,p=256 $ Fe ask side-sublayer imp:n,p=512 $ Fe ask side-sublayer 9 32

34 imp:n,p=1024 $ Fe ask side-sublayer 10 deompose ask lid into 9 sublayers imp:n,p=4 $ Fe ask lid-sublayer imp:n,p=8 $ Fe ask lid-sublayer imp:n,p=16 $ Fe ask lid-sublayer imp:n,p=32 $ Fe ask lid-sublayer imp:n,p=64 $ Fe ask lid-sublayer imp:n,p=128 $ Fe ask lid-sublayer imp:n,p=256 $ Fe ask lid-sublayer imp:n,p=512 $ Fe ask lid-sublayer imp:n,p=1024 $ Fe ask lid-sublayer 9 other ask ells imp:n,p=1 $ bottom basket imp:n,p=2 $ top plenum basket imp:n,p=2 $ top fitting imp:n,p=2 $ ss side basket imp:n,p=2 $ Al side basket/rails imp:n,p=2 $ top void - part1 (air) #10 imp:n,p=2 $ top void - part2 (air) imp:n,p=2 $ hold down ring imp:n,p=1024 $ polyprop top shield imp:n,p=1024 $ air under top over -pt imp:n,p=1024 $ air under top over -pt imp:n,p=1024 $ top Fe over - top imp:n,p=1024 $ top Fe over - side imp:n,p=1024 $ top side-shld Fe shell imp:n,p=1024 $ side side-shld Fe shell imp:n,p=1024 $ bot side-shld Fe shell imp:n,p=1024 $ side resin/al shield imp:n,p=1024 $ air under side shld imp:n,p=1024 $ air above side shld - pt imp:n,p=1024 $ air above side shld - pt2 **** fuel regions imp:n,p=1 $ FUEL region 1 (bottom) imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region imp:n,p=1 $ FUEL region 10 (top) ***** outside ells above/below ask imp:n,p=1024 $ onrete beneath ask imp:n,p=1024 $ air above ask-pt imp:n,p=1024 $ top-top air above ask-pt2 ***** ells for detetor volumes and air/soil layers beyond ask -- ells before and at 2m detetor imp:n,p=1024 $ onrete before detetor imp:n,p=1024 $ air before detetor 33