ML20205M172
| ML20205M172 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 04/11/1986 |
| From: | Koester G KANSAS GAS & ELECTRIC CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| KMLNRC-86-063, KMLNRC-86-63, NUDOCS 8604150115 | |
| Download: ML20205M172 (11) | |
Text
KANSAS GAS AND ELECTRIC COMPANY THE ELECTRC COMPANY GLENN L KOESTER WICE PRE 5tDENT hvCLE AR April 11, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory h innion Washington, D.C.
20555 EMINRC 86-063 Re:
Docket No. SIN 50-482 Ref:
1)EMENRC 85-264 dated 12/6/85 from GLKoester, EG&E, to HRDenton,1EC 2)EMENRC 86-038 dated 3/6/86 from GIKoester, EG&E, to Rmartin, IEC Subj:
Supplemental Information Regarding Revision to Technical Specification 3/4.6.1.6
Dear Mr. Denton:
'Ihe purpose of this letter is to provide supplemental informati a regarding the References.
Additional information concerning the methodology and assumptions used to establish a maximum allowable filler material pumping pressure for tendon duct regreasing and corrosion protection features of Wolf Creek Generating Station's post-tensioning system was requested during dino mnions with your Staff.
Reference 1 transmitted an application for l
amendIront to Facility Operating License No. NPF-42 for Wolf Creek Generating Station,. Unit No.
1.
'Ihis application requested that Section 3/4.6.1.6, Containment Vessel Structural Integrity, of the Wolf Creek Generating Station (WOGS) Technical Specifications be revised.
'Ihe first year tendon surveillance of Wolf Creek Generating Station's containment post-tensioning system began on January 27, 1986.
The surveillance inspection procedures required in part, inspection of tendon wire and anchorage cmponents for evidence of corrosion arrl/or cracking, inspectic.,of concrete adjacent to the bearing plates for cracks, inspection of the tendon system for signs of water intrusion, chr>mi mJ analysis of the filler material, verification of tendon lift-off force and elongation, and the measurement of sheathing filler grease voids expressed as a percentage of the not duct volume.
'Ihere was no evidence of water intrusion into any of the surveyed tendon ducts or grease cans, nor was there any sign of unacceptable corrosion 8604150115 60411 8001 PDR ADOCK 05000482 P
O PDR 201 N. Market -Wichita, Kansas - Mail Address: RO. Box 208 I Wichita, Kansas 67201 - Telephone: Area Code (316) 261-6451 lll l
l Mr. H. R. Denten IM NRC 86-063 Page 2 April 11, 1986 en any of the tendon wires, buttonheads or anchorage components that were examined. The post-tensioning system at WOGS is designed to prohibit tendon wire corrosien and prelMa the intrusion of water into the tendon ducts.
The reactor building consists of a pre = L h,
reinforced concrete, cylindrical structure with a ham 4=pherical dme and a conventionally reinforced h =Le base slab.
A continuous peripheral tendon access gallery below the ham slab is provided for the installation and inspection of the vertical post-tensioning system.
The tenian system enployed to post-tension the cyclindrical shell and dome uses unbonded tendans each consisting of approximately 170 one-quarter-inch-diameter high sk=gth steel wires and anchorage cupents (See Figure 1).
The prestressing load is transferred by cold formed button heads on the ends of the individual wires, through the anchor baMa and shims, to the steel bearing plates emhaMM in the structure.
h ultimate sk ereth of each tendm is approximately 1,000 tons.
The vertical tendons consist of 86 inverted U-shaped tendons, which extend through the full height of the cylindrical wall over the dme and are ardu.ui at the botte of the haw slab.
h horizontal circumferential (hoop) tendcos consist of 165 tendons anchored at three buttresses equally spaced around the outside of the reactor building.
Each tendan is anchored at buttresses located 240 degrees apart.
Three adjacent tendons, anchored at alternate buttresses, result in two cmplete hoop tendons.
h unbonded tendons are installed in tenden ducts (sheathing) and tensioned in a -predetermined sequence, h ducts, which form voids through the concrete between the anchorage points, consist of galvanized, spiral
- wrapped, semirigid corrugated steel tubing.
They are designed to retain their shape and resist c.u b kuction loads. The inside diameter of the ducts is sufficiently large to permit the installation of the tendons with minimum difficulty.
Trumpets, which are enlarged ducts attached to the bearing
- plates, allow the wires to spread out at the anchorage to suit anchor head hole spacing and facilitate field cold formed button heading of the ends of the wires.
h tendon duct provides an enclosed space surrounding each tendon.
After stressing, a petroleum-based corrosion inhibitor is pH into the duct.
All tendon duct vents and drains used to facilitate punping operations were then closed and grouted to preclude the intrusion of contaminants.
2 6
Mr. H. R. Denton 10ENRC 86-063 Page 3 April 11, 1986 i
l Preventim of corrosion of the tendons and dra-iso. age w-is is assured by adequately coating the tardon wires and anchorage w-tw with anti-i corrosive mnids.
'Ihe filler material used in the WOGS post-tensioning
- systen, Vim.us sust 2090P-4, ensures corrosion protection by a variety of functions including the material's affinity to adhere to steel surfaces, its ability to andaify any moisture in the system, its self healing ability and by its resistance to moisture, mild acids, alkalis and bacterial and microbiological C-g.dation.
As long as sufficient grease has been intrrh into the system to coat the wires and anchorages ocmpletely, corrosion protection is assured.
Additimal protection is afforded by each tenden wire being individually pre-coated with Viswierast 1601 Amber prior j
to installation.
h degree of filling the interstitial spaces which
]
ocaprise the not duct volume, is not directly related to the C=p. e of coating which occurs and u.sequently, is not of significant importance as i
an indicator of operability of the sheathing filler material.
'Ihe manufacturer of Vim.ucrast 2090P-4, Viscosity Oil Otmpany, has tested various diaracteristics of Viscciarast 2090P-4 to show its suitability for the bulk fill corrosicn protection application in ocntainment post-l tensioning systems.
Among these tests were sme standard accelerated corrosicm tests.
A 0.5 mil coating of Viswa Kast 2090P-g performed satisfactorily running foroverg000hoursinasaltfogat95 fahrenheit 1
and a h =idi_ty cabinet at 110 fahrenheit and 100 p=u.c=:nt, relative 1
h =idity. Additionally during axidation resistance testing, metallic strips of aluminum, brass and copper were tested for weight loss after being placed 0
in a bath of Viswicrost 2090P-4 at 275 fahrenheit for 14 days.
'Ihe results of these tests showed no weight loss on the metalic strips.
Resistance to weight loss of the metals at these cF=.id.ing conditions indicates excellent stability.
1 During a meeting between 1(ansas Gas and Electric Ocupany (IC&E) and the NRC Staff en nar,amhar 10, 1985, IC&E acknowledged that an analysis should be performed to determine the opHun pressure at which filler material could be addad to the tenden ducts.
'Ihis preamwe was to be establidied at a I
level that would assure no damage occured to the concrete, reinforcing, or l
liner plate during regreasing operations performed as part of the in-service surveillance of the containment post-tensioning system.
A ocncise summary of this calculation is provided as an Attachment to this letter.
As a result of this calculation punping pressure was limited to less than or equal to 60 psi above static pressure.
During the first year tendon surveillance, voids in excess of 5 p=u.wat.
of net duct volume were identified.
'Ihese occurences are fully described in Special Report 86-01 (Refererx:e 2).
1 4
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I Mr. H. R. Denton j
ICENRC 86-063 Page 4 April 11, 1986 i
Results of the first year t h surveillance at WOGS confirmed that the containment post-tensionirs system is % mtely perfoming its design function and that no abnormal degredation has occurred since the initial containment structural integrity test.
'Ihese results fully support the analyses provided in Reference 1.
'Ihe conclusions of the Safety Analysis and Significant Hazards Consideration provided by Reference 1 are still wholly valid and correct.
Based on the technical analyses provided by Reference 1 ard the supplemental information provided herein, IEEE requests that the subject Technical Specification revision be granted by the Nuclear Regulatory Nimion.
If you have any questions w m Tiing this matter, please contact me or Mr.
O.L.
Ibynard of my staff.
Very truly yours, i
Glenn L. Koester Vice President - Nuclear l
GLK:see Attachment cc: PO'Connor (2)
JCummins GAllen EIchnson
8 9
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Mr.
H.,R. Denton Attachtnent to KMLNRC 86-063 Page 1 April 11, 1986 Simenary of Calculation for Begreasing Pressure OBJECTIVE:
The subject calculation was performed to determine a structurally acceptable tendon duct internal pressure that would not damage the concrete, reinforcing, or liner plat.9 during regreasing operations performed as part of in-service surveillance cf the contaiment post tensioning system.
Sheathing integrity is not a c.nneern since the sheathing does not perform a structural function.
CAICULATION DESCRIPTI^.,N:
Tne following areas of concern were investigated in the calculation:
A.
Crack initiation in the concrete forming the tendon duct.
Effect of sheathing filler material pressure on liner plate.
B.
A.
Crack Initiation At some limiting value of internal pressure the tensile strength of the duct wall concrete will be exceeded, permitting cracks to form. Once cracks have formed, migration of the sheathing filler material to other parts of the shell is feasible.
To investigate this case, an eccentric bore (Timoshenko, Weory of Elasticity) subject to internal pressure was used to simulate the tendon duct and surrounding concrete.
Refer to FIGURE 1.
The resulting tangential stresses caused by the internal pressure were conservatively added to existing transverse tension stresses. The I
existing transverse tension stresses are caused by radially inward-acting forces from the stressed tendons. The combination of these stresses is limited by the allowable shear strength of the reinforced concrete wall.
Refer to FIGURE 2.
B.
Liner Plate me existence of cracks in the concrete under normal operating loads which extend fra the tendon ducts to the liner plate is highly unlikely. Under normal operation the containment is subjected to dead load + prestress load + thermal load.
mese loads produce ccupression on the inside face of the concrete shell walls and consequently exclude tension cracks on this face. However, at shell discontinuities such as at the base slab and buttresses, it is possible for cracks to exist resulting fra shear forces occurring at these discontinuities. These cracks could extend to the liner plate.
If grease were able to migrate to the liner plate through such cracks or through localized concrete imperfections, liner plate damage could occ~r.
u
Mr. H. R. Denton Attach' ment to KMLNRC 86-063' Page 2 April 11, 1986 I
i 4
me liner plate is anchored. to the containment wall by vertical angle
{
stiffeners. spaced 15 inches apart.
We plate was analyzed as a merrbrane supported at the location of the stiffeners. At some limiting pressure, j
deformations in the liner plate bec m e unacceptable and the possibility of liner cracking and the resulting loss of pressure retaining integrity.
.is greatly increased.
Refer to FIGURE 3 which shows a segment of the I
containment wall along with the liner plate, reinforcement, and tendon ducts.
CAICULATION RESULTS A.
Crack Initiation Tangential tension stresses resulting from an internal duct pressure of 1
190 psi, when conservatively combined with radial shear stresses, are.
l theoretically sufficient to initiate cracks in the concrete surrounding the ducts.
I B.
Liner Plate L
If the liner is asstuned to act as a membrane, it will carry i
approximately 60 psi at which time membrane yieldina will occur.
%e resulting unrestrained plastic flow which would occur is unacceptable both frcm the standpoint of possible liner cracking and movement of I
items which may be attached to the liner plate.
CAICULATION COtCLUSIONS:
4 The calculations describe two areas of ' concern regardirg allowable internal i
pressure of tendon ducts:
J!
A.
Crack initiation (190 psi)
B.
Potential damage to liner plate (60 psi) l
@e calculations reveal that a pressure as high as 190 psi could be sustained by the concrete prior to the initiation of cracking in the walls of the ducts. During initial installation of the post-tensioning' system, injection point pressures of up to 84 psi were required to overecme the j
static head of.the liquid grease column in the ducts for the vertical tendons. No evidence existed of grease penetration into or.through'the concrete at or near the base of this column under the action of this pressure, nor was there any evidence of liner plate damage.
It was decided, however, to conservatively limit the pressure to 60 psi i
above installation pressure to preclude any possibility of damage to the liner plate.
DOCUMENTATION OF PRESSURE LIMITATIONS:-
i specification CAA997206 and INRYCO Procedure SQ 12.1 were revised to incorporate the above pressure limitations.
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.Ar. Hs R. Danton Attachment to KMLNRC 86-063 Page 3 April 11, 1986 N
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,Mr. H. R. Danton Attachment to KMLNRC 86-063 Page 5 April 11, 1986 4
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Mr.
H.* R. Denton KMLARC 86-463 Paga 5 April 11, 1986 i
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FIGURE 1
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