MONITORING OF TENDON FORCES IN SWEDISH CONTAINMENTS Energiforsk seminar – 15/3 Peter Lundqvist Vattenfall AB / Energiforsk AB
MONITORING OF TENDON FORCES IN SWEDISH CONTAINMENTS
Energiforsk seminar – 15/3
Peter Lundqvist Vattenfall AB / Energiforsk AB
SWEDISH CONTAINMENTS WITH UNBONDED TENDONS Forsmark 1‐3, Boiling water reactors (BWR) Ringhals 2‐4, Pressurized water reactors (PWR)
SWEDISH CONTAINMENTS WITH UNBONDED TENDONS
VSL BBRV
MEASUREMENTS OF TENDON FORCES
Tendon forces are measured at regular intervals, every 5th yearMeasurements by connecting a hydraulic jack to the anchor head
IN‐SERVICE INSPECTIONS ‐ RINGHALS
Inspections according to American guidelines, Regulatory Guide 1.35 4 % of the tendons in each group are tested ( minimum 4) No abnormal degradation only 2 % may be tested (minimum 3) Performed every 5th year Detensioning of tendons Inspection of grease
IN‐SERVICE INSPECTIONS (ISI) ‐ FORSMARK
Modified version of Regulatory Guide: Variation in tendon forces increase with time Tendon forces are normally distributed Number of tested tendons based on statistical evaluation of measured forces
INSTRUMENTATION OF TENDONS
Load cells Strain gauges on strands or on the anchor head
Advantages compared to ISI Original post‐tensioning forces are known Continuous monitoring of prestress losses Degradations or failures of tendons can be detected early
INSTRUMENTATION OF TENDONS – FORSMARK 1
Load cells on horizontal and vertical tendons Monitoring of tendon forces Similar results as the ISIs
0 5 10 15 20 25 30 350.88
0.9
0.92
0.94
0.96
0.98
1
Time / Year
Rel
ativ
e te
ndon
forc
e / -
Hydraulic jackLoad cells
0 5 10 15 20 25 30 350.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1
Time / Year
Rel
ativ
e te
ndon
forc
e / -
Hydraulic jackLoad cells
INSTRUMENTATION OF TENDONS – FORSMARK 2
Energiforsk project during 2014 During ISI 2014 3 tendons were de‐tensioned and replaced Vertical and horizontal tendons (cylinder wall), horizontal tendon (pool wall) The new tendons were instrumented with load cells and strain gauges
FORSMARK 2
MEASUREMENTS DURING TENSIONING
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000
500
1000
1500
2000
2500p g pp p g
retake in jack
anchor set losses
compensation
shims
lift‐off
Time / s
Tend
onfo
rce
/ kN
MEASUREMENTS DURING TENSIONING
0 1000 2000 3000 4000 5000 6000 7000 8000 90000
500
1000
1500
2000
2500
Time / s
Tend
on fo
rce
/ kN
Load cellStrain gauge
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000
500
1000
1500
2000
2500
Time / sTe
ndon
forc
e / k
N
Load cellStrain gauge
ANCHOR SET LOSSES
Tendon Loss / kN Loss / %
Vertical, cylinder wall 165 7.1
Horizontal, cylinder wall 1 396 20.4
Horizontal, cylinder wall 2 396 19.0
Horizontal, pool wall 1 330 13.7
Horizontal, pool wall 2 351 15.3
COMPENSATION FOR ANCHOR SET LOSSES
Tendon Increase / kN Increase / % Effect / kN Effect / %
Vertical, cylinder wall 232 10.8 54 2.5
Horizontal, cylinder wall 1 477 30.5 88 5.7
Horizontal, cylinder wall 2 436 25.8 80 4.7
Horizontal, pool wall 1 429 18.1 67 3.5
Horizontal, pool wall 2 402 19.3 32 1.5
ACCURACY OF HYDRAULIC JACK MEASUREMENTS
Tendon Hydraulic jack / kN Load cell / % Difference / %
Vertical, cylinder wall 2357 2374 ‐0,7
Horizontal, cylinder wall 1 2078 1968 5,6
Horizontal, cylinder wall 2 2086 1991 4,8
Horizontal, pool wall 1 2347 2267 3,5
Horizontal, pool wall 2 2327 2202 5,7
FRICTION LOSSES
0 50 100 150 200 250 300 3500
200
400
600
800
1000
1200
1400
Tend
on fo
rce
activ
e en
d / k
N
Tendon force passive end / kN
Post‐tensioning was initially performed from one end
FRICTION LOSSES – TENDON FORCE VARIATIONSHorizontal tendon in pool wall
0 5 10 15 20 25 30 35 40750
800
850
900
950
1000
1050
1100
1150
Length / m
Tend
on fo
rce
/ kN
0 10 20 30 40 50 60 70 80 90200
400
600
800
1000
1200
1400
Length / m
Tend
on fo
rce
/ kN
Horizontal tendon in cylinder wall
Tendon k / % μ / ‐
Horizontal, cylinder wall 0.15 0.35
Horizonmtal, pool wall 0.15 0.15
LONG‐TERM MEASUREMENTS
0 50 100 150 200 250 300 350 4001930
1940
1950
1960
1970
Time after tensioning / d
Tend
on fo
rce
/ kN
0 50 100 150 200 250 300 350 40022
24
26
28
30
32
Tem
pera
ture
/ C
Tendon forceTemperature
Load cell Strain gauge
0 50 100 150 200 250 300 350 4001460
1480
1500
1520
1540
1560
1580
Time after tensioning / d
Tend
on fo
rce
/ kN
Horizontal tendon, pool wall
LONG‐TERM MEASUREMENTSHorizontal tendon, cylinder wall
0 50 100 150 200 250 300 350 4002150
2200
2250
2300
2350
Time after tensioning / d
Tend
on fo
rce
/ kN
PRESTRESS LOSSES
Tendon Time / d Prestress loss / kN Prestress loss / % Relaxation (EC2) / %
Vertical, cylinder wall 398 52 2.2 1.4
Horizontal, cylinder wall 1 368 26 1.3 0.6
Horizontal, cylinder wall 2 368 25 1.2 0.6
Horizontal, pool wall 1 357 47 2.1 0.9
Horizontal, pool wall 2 357 24 1.0 1.2
0 5000 10000 150002280
2300
2320
2340
2360
2380
Time after tensioning / d
Tend
on fo
rce
/ kN
Relaxation (EC2)Regression
THANK YOU FOR YOUR ATTENTION!