Graphite Component Assessment for TMSR

Samantha Yong, Derek Tsang, Maoyuan Cai

Contents

1. Introduction of ASME and KTA-3232

2. The numerical result from ASME and KTA-3232

3. Effect of maximum grain size on probability of

failure finally

TMSR graphite core

16 graphite components Top and bottom reflector Side reflector Dowel Key

To show the designs are safe There are two standards

ASME USA KTA-3232 German

1. Introduction of ASME and KTA-3232

Determi ni st i c

ASME HHA

Graphi te reactor

assessment

KTA-3232

Probabi l i ty theory

Probabi l i ty theory

Determi ni st i c

Assess wi th stress l i mi ts

Assess wi th POF l i mi ts

Stress l i mi ts i s to be cal cul ated usi ng Two-parameter Wei bul l di stri buti on

POF l i mi ts i s to be cal cul ated usi ng three-parameter Wei bul l di stri buti on

Same

Di ff erent

Stress l i mi ts i s to be cal cul ated usi ng two-parameter Wei bul l di stri buti on

POF l i mi ts i s to be cal cul ated usi ng two-parameter Wei bul l di stri buti on

Probability of Failure flow chart in ASME

Convert compressi ve stress to equi val ent

tensi l e stress

Rank the i ntegrati on poi nts i n decreasi ngorder of equi val ent stress

Cal cul ate S0

El i mi nate i ntegrati on poi nts bel ow i ntegrati on

poi nts

Cal cul ate Xi

Start fi rst group

Sel ect fi rst hi ghtest stress

Add i ntegrati on

poi nt

I s the vol ume of group l arger than (10× mgs)3

Does di ff erence between max(Xi )and mi n(Xi )

exceed 7%Any i ntegrati on

poi nt l ef t

End current group and cal cul ate probabi l i ty

of survi val

Start new group

End l ast group

Cal cul ate probabi l i ty of survi val

For enti re component Cal cul ate POF

YES

NO

YES

YES

NO

NO

Sel ect next i ntegrati on

poi nt

stress limit

In process , equivalent stress is calculated as

Xi is the index of Weibull distribution calculated as

Convert compressi ve stress to equi val ent

tensi l e stress

Rank the i ntegrati on poi nts i n decreasi ngorder of equi val ent stress

Cal cul ate S0

El i mi nate i ntegrati on poi nts bel ow i ntegrati on

poi nts

Cal cul ate Xi

Start fi rst group

Sel ect fi rst hi ghtest stress

Add i ntegrati on

poi nt

I s the vol ume of group l arger than (10× mgs)3

Does di ff erence between max(Xi )and mi n(Xi )

exceed 7%Any i ntegrati on

poi nt l ef t

End current group and cal cul ate probabi l i ty

of survi val

Start new group

End l ast group

Cal cul ate probabi l i ty of survi val

For enti re component Cal cul ate POF

YES

NO

YES

YES

NO

NO

Sel ect next i ntegrati on

poi nt

probability of failure procedure in KTA-3232

main difference between ASME HHA and KTA-3232 is as follows:

components are grouped in ASME, do not need to be grouped in KTA-3232

The difference between ASME and KTA-3232

Probability models

ASME ： Weibull three parameter model

KTA-3232 ： Weibull two parameter model

Calculate method

ASME ： group the integration points, Group Conditions ：

The group volume is bigger than (10×mgs)3

In the group , max(Xi) is greater than min(Xi) 7%

KTA-3232 ： do not group the components

m

SS

Sx

cF

0

0

exp1

m

S

x

cF

exp1

ASME HHA POF Limits

The POF limits of ASME HHA and KTA-3232 are same .

KTA-3232 POF Limits

Boundary conditions: a. The model is symmetry by the XY, XZ

plane, ¼ model is to be calculated.b. Calculation software :ABAQUS,

element type C3D20, element number 11786.

600 700 800 900 1000 1100 1200 1300 1400 15000

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

(mm)堆芯径向距离

(10

辐照

剂量

20 n

/cm

2E

DN

D )

原 始 数 据拟 合 数 据

the irradiation distribution under normal operation as shown in Figure 1.

2. The calculate result of ASME and KTA-3232

Finite element model

Table 1. POF of 2 different modelThe POF of ASME is more conservative

The stress of component after 20 years

　 POF(ASME HHA)

POF (KTA-3232)

model 1 2.8E-3 1.8E-8

model 2 5.4E-5 1.6E-8

Model 1 keyway root radius=2mmModel 2 keyway root radius=5mm

Maximum grain size: the maximum filler particle grain size that is used in the

graphite formulation.

Each graphite has different MGS, however MGS is one of the most important

factors to affect POF, so we have analyzed the effect of MGS on POF.

NG-CT-10EGCR-TYPE

AGOT[1]NBG-18[2] H451[1]

MGS/mm 0.025 0.78 1.6 1.6

[1]A modified weibull theory for the strength of granular brittle material[2] A numerical stress based approach for predicting failure in NBG-18 nuclear graphite components with verification problems

Table 1. different MGS for different graphite

3. Effect of maximum grain size(MGS) on probability of failure

The POF of Graphite component of NBG-18

Table 2. POF of same model for different MGS

Table 1. Parameter of three parameters Weibull distribution

• MGS is one of grouping criterion in ASME.

• The grouping criterion is based on

experiment of NBG-18.

• The grouping criterion is suitable for the

graphite has the same or similar MGS.

• The method to calculate POF maybe

conservative (or too conservative) if the

MGS is small when assess the fine grade

graphite.

• The group criterion should be remark for the

fine coarse graphite.

MGS/mm POF

0.025 1.5E-2

0.17 2.8E-3

0.48 1.1E-4

0.78 2.3E-5

1 1.1E-5

1.6 2.8E-6

In order to analysis the effect of MGS,

NBG-18 is chosen to calculate POF.

14

Conclusions

Described the differences between ASME and KTA-3232, compared the POF of the two standards, The POF of ASME is more conservative.

The effect of MGS on POF has been analyzed, ASME standard is based on coarse grain graphite, for fine grain graphite the grouping criterion should be modified for the fine grain graphite.

Thank you