Title: Professor V.I. Makhnenko, scientist A.S. Milenin
1Remaining Time Assessment of the Steam Generator
Welding Joint ?111-1 of NPP VVER-1000 with
Respect to Detected Cracks.
- Professor V.I. Makhnenko, scientist A.S. Milenin
- E.O. Paton Electric Welding Institute
- of National Academy of Sciences of Ukraine
1
2- Fig. 1. Scheme of location of the welded joint ?
111 - body of steam generator
- collector
- nipple ? 1200
- pipe conduit DU-850
- pocket
- A discontinuity (defect).
2
3- Fig. 2. Defectogram of the welded joint ?111-1 of
hot collector 1PG-1 of Uzhno-Ukrainskaya
nuclear power-plant in 1 year after first repair.
3
4- Fig. 3. Defectogram of ultrasonic inspection of
the steam generator ? 3, power unit ? 4 of
Zaporozhskaya nuclear power-plant.
4
5- Fig. 4. Cartogram of discontinuity ?3 of the
welded joint ?111-1 (hot collector) PG-3 of
power unit ?4 Zaporozhskaya nuclear power-plant
according to the data of the Expert's report
UkrTsNIITMASh of 13.01.2006.
5
6- Main Problem permissibility of exploitation of
the steam generator 4PG-3 of Zaporozhskaya
nuclear power-plant with a detected defect in
the region of the welded joint ?111-1 until at
least the next planned repair (about 1 year).
Questions are to be answered 1. What is the
degree of risk of the generation of the
through-wall crack within the mentioned
period of the exploitation, i.e. the leakage
in the region of the growing defect, that will
lead to the emergency stop of the power
unit? 2. What is the degree of risk of
the spontaneous destruction with the
unpredictable consequences?
6
7Chemical composition, weight percent. Chemical composition, weight percent. Chemical composition, weight percent. Chemical composition, weight percent. Chemical composition, weight percent. Chemical composition, weight percent. Chemical composition, weight percent. Mechanical properties. Mechanical properties. Mechanical properties. Mechanical properties.
? Si Mn Cr Ni Mo V s?, MPa (200?) s?, MPa (3500?) s0.2, MPa (200?) s0.2, MPa (3800?)
0.134 0.245 0.79 0.25 2.09 0.51 0.02 608 539 500-490 422
- Table 1. Chemical composition and mechanical
properties of steel 10GN2MFA.
7
8- Fig. 5. Calculation data about the distribution
of working stresses szz in the region of the
pocket depending on pressure in the steam
generator P6.4 MPa and in the collector PC16
MPa.
8
9- Table 2. Stresses szz in the region of the defect
depending on working pressure 6.4 MPa.
9
10597 607 617 627 637 647 657 667 r, mm
z, mm
5 86.85 86.16 79.91 69.22 56.83 45.29 36.04 29.33
15 78.68 73.50 67.96 61.79 55.16 48.58 42.70 38.36
25 68.66 64.57 62.28 60.81 58.88 55.92 52.38 49.80
35 60.43 59.21 60.62 62.98 64.64 64.71 63.52 62.49
45 54.47 56.44 61.17 66.49 70.96 73.82 75.29 76.35
55 50.49 55.20 62.84 70.49 77.27 82.77 87.32 91.32
65 48.13 54.79 65.22 74.84 83.40 91.44 99.35 107.16
75 47.85 55.10 68.98 79.36 89.29 99.98 111.13 123.36
85 49.83 65.62 74.51 84.07 95.50 108.96 122.86 138.84
95 130.20 99.19 86.20 91.58 103.41 119.35 135.39 151.88
105 149.72 130.69 126.18 123.01 125.53 134.43 149.64 165.11
115 186.77 180.50 171.04 165.63 160.97 161.55 170.41 183.02
125 220.56 218.10 212.87 209.39 202.83 197.88 197.18 194.71 Seam ?111
135 225.94 224.91 222.37 314.19 210.05 204.41 200.93 196.45
145 168.58 156.43 149.18 153.81 160.58 171.71 182.66 194.74
155 157.85 145.07 145.82 154.03 164.00 175.81 191.44 202.23
165 149.36 139.96 139.98 145.89 158.92 178.75 197.08 212.97
175 140.76 132.79 132.63 141.22 157.36 179.27 203.90 220.17
185 129.27 121.76 123.57 132.08 148.67 173.68 206.78 229.28
195 115.26 108.45 107.98 113.02 126.15 151.31 198.05 249.03
205 100.57 93.09 87.86 85.61 86.63 69.35 86.97 47.65
215 86.60 77.67 69.64 61.95 53.59 40.48 14.86 -48.71
225 73.60 63.97 53.93 42.38 28.19 8.36 -24.61 -63.10
235 62.82 52.91 41.57 28.06 11.29 -10.67 -37.26 -68.46
245 55.26 45.35 33.47 19.13 1.78 -18.47 -41.81 -69.35
255 51.84 41.86 29.84 15.47 -1.39 -20.33 -41.67 -66.95
265 52.50 42.84 30.93 16.66 0.27 -17.83 -38.00 -61.50
275 57.95 48.35 36.39 22.10 5.83 -12.13 -31.81 -54.00
285 68.16 58.42 46.21 31.63 14.85 -3.83 -23.83 -45.07
295 83.11 73.00 60.38 45.24 27.06 6.80 -14.46 -35.42
305 102.56 92.08 79.19 62.15 42.36 20.35 -2.92 -25.70
315 126.93 116.79 103.69 87.15 67.68 46.29 24.70 3.41
- Table 3. Residual stresses sbb (MPa) in the
region of the welded joint ?111.
10
11597 607 617 627 637 647 657 667 r, mm
z, mm
5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
15 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
25 -1.95 -2.22 -1.82 -1.44 -1.13 -0.94 -0.74 1.08
35 -4.00 -4.55 -3.61 -2.82 -2.36 -2.13 -1.65 0.45
45 -5.28 -5.54 -4.11 -3.38 -3.36 -3.60 -3.51 -2.53
55 -4.79 -4.29 -2.67 -2.92 -4.16 -5.59 -6.68 -8.01
65 -0.98 0.10 0.79 -1.75 -5.09 -8.22 -11.22 -15.72
75 9.25 8.48 5.54 -0.74 -6.46 -11.37 -17.05 -25.03
85 32.00 20.30 9.06 -0.62 -8.14 -14.73 -23.57 -35.33
95 77.13 25.73 10.57 -0.15 -9.62 -17.85 -29.56 -46.46
105 77.15 38.92 1674 2.45 -10.52 -21.20 -35.35 -56.82
115 72.34 55.81 24.91 6.80 -14.09 -30.21 -42.14 -60.70
125 75.02 58.64 31.26 7.83 -12.88 -30.98 -44.28 -70.82 Seam ?111
135 71.89 59.03 39.01 12.81 -8.29 -30.50 -50.93 -78.54
145 71.18 62.12 34.91 18.29 -4.80 -29.46 -57.14 -80.27
155 73.07 55.38 37.69 19.15 -3.37 -30.38 -56.17 -80.64
165 70.90 51.62 37.78 20.00 -2.80 -28.33 -56.96 -77.92
175 70.13 47.18 31.88 17.42 0.28 -24.37 -53.05 -75.94
185 64.36 41.92 28.38 15.90 2.36 -18.57 -48.92 -73.00
195 54.66 37.11 24.34 13.21 3.03 -10.10 -36.41 -74.85
205 45.79 31.68 19.44 8.44 -0.92 -7.59 -7.82 -79.78
215 38.92 26.40 16.02 7.04 -0.66 -10.18 -32.65 -37.64
225 31.55 20.91 11.88 3.72 -4.71 -15.71 -28.52 -9.33
235 23.90 14.94 7.02 -0.47 -8.05 -15.34 -14.46 2.01
245 16.37 9.09 2.42 -3.70 -8.89 -10.27 -4.54 7.53
255 9.65 4.00 -1.18 -5.41 -7.62 -5.51 1.66 10.68
265 4.36 0.13 -3.49 -5.86 -5.90 -2.12 5.18 12.71
275 0.80 -2.26 -4.58 -5.58 -4.41 -0.18 6.75 13.79
285 -0.86 -3.35 -4.65 -4.79 -3.33 0.42 6.62 13.80
295 -0.97 -3.38 -3.77 -3.57 -2.58 0.04 4.96 12.38
305 -0.25 -2.56 -2.11 -2.30 -1.91 -0.55 2.49 8.50
315 0.30 -0.76 -1.01 -1.10 -1.00 -0.35 1.30 -0.28
- Table 4. Residual stresses szz (MPa) in the
region of the welded joint ?111.
11
12- Fig. 6. Total stresses szz at the plane of crack
zconst.
12
13- Fig. 7. Scheme of the diagram of the static
corrosive crack growth resistance of
constructional material - diagram lg v KI according to experimental data
- idealized diagram.
13
14Three main stages of the diagram of the static
corrosive crack growth resistance
- first stage (KIltKISCC), when the mechanism of
the electrochemical corrosion in the growth of
crack prevails, here the values of the crack
growth rates are rather small and with reference
to the case under consideration don't exceed 1-2
mm/year - second stage (KISCCltKIltKIC), when the mechanism
of the hydrogen embrittlement in the growth of
the corrosion crack prevails, here the values of
crack growth rates are sufficient enough and for
constructional steels in the environment of the
feedwater they can mount to the values 50
mm/year - third stage (KIgtKIC) corresponds to the state
of high risk of the spontaneous growth of crack.
14
15Steam generator Number of defect Size of defect, mm Size of defect, mm Equivalent crack Equivalent crack Equivalent crack Equivalent crack Scheme of semi-elliptical crack
Steam generator Number of defect Depth, H, mm Width, 2L, mm ?, mm ?, mm KI(G), MPa?m1/2 KI(D), MPa?m1/2 Scheme of semi-elliptical crack
1PG-1 UUNPP 1 63 65 51.2 51.2 59.24 41.18
1PG-1 UUNPP 2 64 85 59.0 59.0 70.18 45.20
1PG-1 UUNPP 3 50 50 40.0 40.0 45.11 35.50
1PG-1 UUNPP 4 40 15 19.6 19.6 26.75 24.34
1PG-1 UUNPP 5 53 70 48.7 48.7 55.75 39.90
1PG-1 UUNPP 6 3 10 3 5 10.60 12.15
1PG-2 UUNPP 1 8 15 8.8 8.8 17.82 16.34 a H, c L, if H ? L if H gt L
1PG-2 UUNPP 2 50 25 28.3 28.3 33.90 29.40 a H, c L, if H ? L if H gt L
1PG-2 UUNPP 3 40 15 19.6 19.6 26.75 24.34 a H, c L, if H ? L if H gt L
1PG-2 UUNPP 4 35 30 25.9 25.9 31.86 28.07 a H, c L, if H ? L if H gt L
1PG-2 UUNPP 5 10 25 10.0 12.5 19.29 19.63 a H, c L, if H ? L if H gt L
1PG-2 UUNPP 6 48 72 47 47 53.45 39.04 a H, c L, if H ? L if H gt L
- Table 6. Sizes of defects and equivalent crack,
values of KI(G) and KI(D).
15
16597 607 617 627 637 647 657 667 r, mm
z, mm
5 86.85 86.16 79.91 69.22 56.83 45.29 36.04 29.33
15 75.50 75.63 69.26 64.49 58.55 52.14 46.05 41.63
25 68.20 68.45 64.91 64.39 63.14 60.68 57.95 56.80
35 62.37 63.09 64.14 67.36 69.84 70.84 71.40 72.87
45 58.23 60.14 64.93 71.25 76.84 81.11 85.30 89.65
55 55.09 58.14 65.85 74.87 83.20 90.84 99.05 107.00
65 52.18 56.35 66.10 77.29 88.64 99.82 112.32 124.65
75 51.57 49.30 62.62 78.52 93.53 108.63 124.87 142.11
85 47.39 40.48 66.29 82.29 98.54 116.13 134.80 165.01
95 117.31 88.58 92.87 98.57 112.42 131.06 151.54 168.18
105 143.70 126.20 126.75 129.24 134.88 146.46 165.17 185.42
115 185.38 180.93 175.51 172.17 169.85 172.52 185.24 198.97
125 221.57 220.81 215.14 214.53 210.43 207.71 208.86 205.93 Seam ?111
135 230.44 231.20 227.04 221.01 218.29 213.95 211.89 207.90
145 180.09 170.07 162.40 166.02 172.31 182.80 193.83 205.06
155 172.73 161.81 160.05 167.57 176.30 186.95 200.50 211.66
165 168.01 160.38 159.08 162.07 172.25 189.31 205.42 220.18
175 163.60 157.20 154.44 158.99 171.14 189.31 209.12 227.37
185 157.07 151.07 147.72 151.54 162.86 182.24 208.85 234.07
195 148.68 143.40 136.40 135.45 141.49 158.23 190.94 230.10
205 139.62 133.69 122.10 112.59 105.75 100.36 77.02 54.73
215 131.11 123.77 108.87 93.33 76.20 50.96 10.51 -82.48
225 123.25 115.25 98.03 79.44 57.88 31.75 -23.90 -62.06
235 116.81 108.54 90.09 70.27 47.48 18.45 -21.33 -49.95
245 112.88 104.61 85.88 66.14 43.55 18.15 -13.73 -38.77
255 112.31 104.20 85.90 67.09 46.21 23.71 -3.74 -26.53
265 115.78 107.87 90.44 72.87 53.64 33.22 8.37 -12.58
275 123.55 115.78 99.32 82.86 64.86 45.62 22.24 2.69
285 135.82 128.05 112.48 96.84 79.41 60.43 37.64 19.12
295 152.65 144.70 129.83 114.78 97.09 77.49 54.52 36.55
305 173.98 165.89 151.46 136.02 117.87 97.38 73.43 53.25
315 196.29 186.76 173.96 159.30 141.90 122.15 100.24 87.43
- Table 5. Total stresses sbb (MPa) in case of
T3000C and working pressure in the region of the
welded joint ?111-1
16
17Calculation of the coefficient of stress
intensity KI(D), KI(G) and sref for the
semi-elliptical crack a2c.
If (a/c)lt1.0 and (a/d)lt0.7
where
Sj is an equivalent stress
Here szz(i) is total stress szz according to the
diagram in Fig. 6 at the depth (a/20)i
(i0,1,2,,20) Ci, Di, Ei, Fi are tabulated
weighting functions,
17
18If (a/c)gt1.0 and 0.2lt(a/d)lt1.0
where
18
19Mathematical formulation of R6 approach.
, if Lr lt Lrmax
Kr0, if Lr Lrmax
where
sref is the stress that is determined with
external power load without taking into account
the residual stresses and that is able at some
level of the loading to cause the plastic
collapse in the region of the defect under
consideration.
19
20To calculate sref it was used
where
20
21(a)
(b)
- Fig. 8. Time dependences of a, c (a) and KI(D),
KI(G) (b).
21
22- Fig. 9. Kinetics of reducing of the safety factor
against spontaneous growth of crack a040 mm,
c045 mm in time KISCC10 MPam1/2, vm44
mm/year.
22
23- Conclusions 1. Numerical analysis of state of
the steam generator 4PG-3 of
Zaporozhskaya nuclear power-plant showed that the
risk of leakage (through
defect) in the course of year of its exploitation
(with double time reserve) is
obviously absent. -
- 2. The kinetics of the changing of
safety factor against the
spontaneous propagation of crack showed that
during a year of the exploitation
the risk of such a spontaneous growth is
minimal.
23