i s. ; 17Rk

EPRI

I- .. I SOURCE TERMIN THE EPRI

PERFORMANCE ASSESSMENT

Presented byRobert A. Shaw

-EPRI

To TheNuclear Waste Technical

Review BoardLas Vegas, NV.

October 15, 1992

Stt 4N ° i 4m m

k (F (i (fi (4) (!) (X (E) A) t) ) )IVI r7 . &.

®©®G®®0®R 44:~

Figure 15-13. Master logic tree.

EF

lk�',

'RI/NPD ENw2RMEM02=C�_

WASTE PACKAGE DEGRADATION

* Weibull distributions for container &cladding failures- Threshold failure times- Mean lifetimes- Failure rate at mean lifetimes

* Degradation modes & failure mechanisms- Environmental, materials, closure,

thermo-mechanical history- Deterministic models for Weibull

parameters- Cladding: creep rupture & hydride

reorientation I'

HLW/SFS 1W92

200.00

_ 1 50.00Li

0I"I-

I-2:W

100.00 -

50.00 -

y

.O _ - _

- _

P

0.00 . . . . . .r"T "TtTI T I 11119 iT MT Vn1 FT u 1 T "V Ir I I I mrlI[ T* i

1 10 100 1000 10000TIME (YEARS)

I I 1"01

100000

Figure 8-2. Three alternative curves showing temperatures at the outersurface of a waste emplacement hole as functions of time.

Table 8-2

SUMMARY OF TEMPERATURE SCENARIOS AND FRACliONS OF REPO-,TORY

AREA FOLLOWING EACH TEMPERATURE CURVE

Scenario Probability Curve cc Curve 1 Curve y1 0.6 0.9 0 0.12 0.3 0.1 0 0.93 0.1 0 1.0 0

I N

© ENGINEERED BARRIER SYSTEM

1 (Type 304L SS)/ ~~pO.Ze

HOT REPOSITORY _/e 2 WA~oy 25)> pO.7 - - :~.

P=O~

(Type 304L S)

1 (Type 304L SS)

p=O.9 0

Figure 15-8. Logic tree node for engineered barrier system.

SENSITIVITY TO SELECTION OF ERS.B

IE-1

pxl0babiIitU

IE-2

IE-3

IE-4

lE-5 _IE-3 iE-4 S 1E-3 LE-2 iE-L LE IE IE 2

Hormalizej Releases

Figue 16-8. Sensitivity of CCDF for 1Np to selection of EBS.

I

SENSITIVITY TO REPOSITORY TEMPERATURE1.0

1E-1

pro IE-2

labiI

t IE-3

IE-4

LE-5 t-IE-5 IE-4 ** IE-3 LE-2 1E-1 LE B

ormalized Releases

Figure 16-6. Sensitivity of CCDF for WNp to repository temperature.

[E IE 2

EPRI/NPD

DISSOLUTION & TRANSPORT OF WASTES

* Release modes- Dry: no release pathway- Wet drip: container fills to penetration- Moist: diffusive & advective pathways

* Chemical constraints on release- Dissolution (alteration, reaction) rates- Radioelement solubility limits

HLW/SFSI 0/2

I

Crud Gap Grain Boundary UOv Matrix Cladding

Fuel Rod C-14 C.14 C-14 Actinidas1.129 1-129 -98% FissionCs-135 Cs*135 ProductsCs.137 Cs-137Se-79 Se-79Tc-99 Tc-99Sr-90 Sr-90

Figure 11-5. Schematic diagram of spent fuel showingdifferent source regions with characteristicradionuclides (3).

C.14

TABLE 1 1-2

ESTIMATED PERCENT OF TOTAL RADIONUCLIDE.INVENTORIESWITHIN THE SEPARATE REGIONS OF SPENT FUEL W

-

Nlucides

C-14

Se 79

Tc-99

SO 126

1-129

Cs.135

U-234

U.238

Np-237

Pu.239

Pu.240

Pu-242

Am-241

Aia243

Cm 14S

U02 MaIX

3S

98

98

t00

98

98

100

100

100

100

t 100

100

100

100

100

Gap (+ GrainBoundary

1

2

2

...

2

2

...

...

...

...

...

...

Claddin

63

...

.. .

.. .

.. .

.. .

.. .

.. .

Surface ayer

I.

...

.. .

.. .

...

.. .

. ..

r

Table 11-4-

SOLUBILITIES OF RADIOELEMENTS, IN gm/M3

Element

CSeTcSnICsRaUNpPUAmCm

Low

1.07.9x102

3.5x10r21.3x104

1.01.21.0x1050.54.0x104

6.0xl0rf1.5x10f72.4xr104

Moderate

1.47.9x1031.Ox1o2

3.2x1033.9x10 2

3.9x1024.0x1042.43.6x102

9.6x1049.6x1o 2

9.6xl02

:P-

High

1.4x102

5.SxIO'9.9x105

2.2xl02

1.OxlO'2.lx1030.15.OxIO'7.2x10'4.3xl0'9.6xl 1'9.6xlr'

®.) SOLUBILITY AND DISSOLUTION RATE

LOWp=0.05

MOPERATEp=0.9

HIGHP=0.05

-

,

Figure 15-9. Logic tree node for solubility and dissolutionrate.

SENSITIVITY TO SOLUBILITY IND DISSOUTION RATE

p0

abi1

t

L. 0 - _

1E-1 -

IE-2

IE-3 -

IE-4

lE-5 -

1E-3 IE-4 ' I E-3 IE-2 IE-1 LE IE I LE 2

Morial izea Releases

Figure 16-9. Sensitivity of CCDF for 'Np to solubility and dissolution rate.

EPRI/NPD

RECENT REFINEMENTS

* Meetings with LBL, UCB, LLNL & SNL

* 3 Alternative Thermal Loadings (Design Parameter)

* 3 Alternative Waste Containers (Design Parameter)

* 3 Heat-Transfer MechanismsConduction, Convection & Heat-Pipe

* 4 Time-Temperature Curves

HLW/SFS10/2

300-

250-

0-200

~150

E C

100- -b

50- i ~===

0 1000 2000 3000 4000 5000 6000 7000 800.0 9000 0000ime (y)

Fractions of Repository in Different Environmentsfor APD=57 kW/acm

Conduction-dominatedp=0.5

I a I 1 -Y 68 TotalDry .7 .09 .06 0 .850

Moist.-Contin. .01 .002 .03 0 .042

Wet-Drip .02 .004 .02 0 .044

Episodic .02 .004 .04 0 .064

Total . I| *75 10 .15 O 1.0

High Permeabilityp=0.2

a 11'8 |Total

Dry .32 .36 .07 0 .750

Moist- Contin. .01 .01 .04 0 .060

Wet-Drip .01 .015 .03 0 .055

Episodic .06 .015 .06 0 .135

Total .400 | .400 .200 j 0 || 1.0

Water Mobile in Fracturesp=0.3

____I a y I| otal |

Dry .25 .04 .1 0 .390

Moist- 0 .025 .15 0 .175Contin.

Wet-Drip .005 .03 .15 0 .185

Episodic .045 .005 .2 0 .250

|Total | .300 .100 |.600 | 1.0 ||

EPRI/NPD

SOME KEY ISSUES,

* EPA HLW Criteria- Regulatory & Licensing Implication

* EBS Design- Borehole or Drift Emplacement- Thermal Load- Waste Container (UCS?)- Backfill Materials

10/9- HLW/SFS

EPRI/NPD

SOME KEY SOUI

i_~~~~~~~~~~~

i

RCE TERM ISSUES

* Solubility Data

* Spent Fuel Inventories

(ESP. C-14)

* Alteration Rates

* Retardation.. r-

,,9' _F

epository Water Chemistry

)10Ij�9

HLW/SFS

II

.

( EPRI/NF'D

PERFORMANCE ASSESSMENTMODELING ISSUES k

(continued)

* Detailed model to overview PA model- transfer function

* Levels of detail in overview models* Incorporating probabilistic and deterministic aspects* Cost and schedule implications

HLW/SFS10/92

EPRI/N1P1)

PERFORMANCE ASSESSMENTMODELING ISSUES

a How can PA models be validated?- subsections with submodels- integrated system

* Bounding or conservative calculations vs. realistic orbest measure calculations

* Self-consistency: heat, water, mass transport, andcoupling

* Cell vs. homogeneous modeling of EBS

* Use of expert judgment

HLW/SFS/10192

EPRI/NPD

SITE UNCERTAINTIES

* Infiltration- What is it at repository elevation?

* Degree of fracturing- Spacing, sizes,

* Coupling between fracture & matrix flow* Permeability of fractures (connectedness)

Lateral flow distribution- Impermeable layers

HLW/SFS10/92

:

CCDFS FOR 12 HUCL IDES RELEASED BY AND AQUEOUS PTHWABYS1.0 -

IE- -

pr0 1E-2-_b aabI

iI 1E-3-

1E-4 -

1E-5-JLE-5

_ yIE-4 IE-3 LE-2 1E-l iE

Normalized Releases

Figure 16-1. CCDFs for 12 nuclides released by gaseous and aqueous pathways.

1E I 1E 2

EPRI/NPD

SOURCE TERM

* Release of radionuclides from near-field- Waste package degradation

- Dissolution of waste- Transport of released radionuclides

0/92> HLW/SFS