ML20024B821
| ML20024B821 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/01/1983 |
| From: | Foster D GEORGIA POWER CO., SOUTHERN COMPANY SERVICES, INC. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, GN-239, SL-3649, NUDOCS 8307110453 | |
| Download: ML20024B821 (10) | |
Text
l Georgi Pow:rCompany
- Post Office Box 4545 Atlanta. Georgia 30302 Telephone 404 526-6526 Miol,cS70?*262 A
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83 JUL 7 All;4I D. O. Foster Vice President and General Manager Vogtle Project July 1, 1983 United States Nuclear Regulatory Commission File:
X7BG03-M25 Office of Inspection and Enforcement Log:
GN-239 Region II - Suite 3100 101 Marietta Street Atlanta, Georgia 30303
Reference:
Vogtle Electric Generating Plant - Units 1 and 2 50-424, 50-425; Embeds - 1982 Attention: Mr. James P. O'Reilly Gentlemen:
On April 26, 1982, Mr. C. W. Hayes of Georgia Power Company notified Mr.
Virgil Brownlee of the USNRC of a potential deficiency concerning the lack of anchor bolt thread engagement for embeds.
Georgia Power Company has conducted an evaluation and concluded that this condition represents a significant deficiency and substantial safety hazard.
Based upon guidance in NUREG-0302, Rev.1, Georgia Power Company is reporting this condition under 10CFR50.55(e).
Enclosed is a copy of our evaluation.
This document does not contain any proprietary information and may be placed in the NRC Public Document Room upon receipt.
YourstruP /
l D. O. Foster D0F/CWH/skr xc:
U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C.
20555 R. J. Kelly R. H. Pinson E. D. Groover R. E. Conway B. M. Guthrie L. T. Gucwa G. F. Head R. A. Thomas M. Malcom J. T. Beckham, Jr.
J. A. Bailey G. Bockhold D. N. MacLemore
- 0. Batum P. D. Rice D. E. Dutton H. H. Gregory, III J. L. Vota W. F. Sanders R. E. Folker FFICIAL col'Y fE 4 8307110453 830701 PDR ADOCK 05000424 S
//
7 3
EVALUATION FOR A SUBSTANTIAL SAFETY HAZARD EVALUATION FOR A SIGNIFICANT DEFICIENCY Embeds 1982 - Anchor Bolt Thread Engagement Initial Report:
On April 26, 1982, Mr. C. W. Hayes of Georgia P'ower Company notified Mr. Virgil Brownlee of the USNRC of a potential deficiency concerning the lack of anchor bolt thread engagement in certain types of embed assemblies.
Interim reports were also filed with the NRC.
Background Information:
During an inspection of previously accepted threadedsanchor embed assemblies in safety-related Class I structures, it was noted that thread engagements less than that required on the design drawings existed on some of the embed assemblies. This was reported to the NRC as a potential deficiency (see above).
Embed assemblies are placed in concrete to provide a surface for attaching structural steel used for various purposes, including such items as piping, HVAC ducts, platforms, or electrical tray supports. The capability of the threaded anchor embed assembly to support its attachments under the applicable load combinations is partially dependent upon the engagement of the anchor bolt threads into the plate nut welded to the back of the embed plate.
Measurement of the thread engagement of the bolt into t'he nut after placement into concrete is possible through an inspection hole in the embed plate. The inspection hole is provided at each bolt location.
Inspections at Georgia Power Company's Vogtle Electric Generating Plant indicated that two-hundred and twenty-two (222) assemblies had the potential of anchor _ bolt thread engagement problems.
Engineering Evaluation:
The threaded anchor embed assemblies issued on the Vogtie Project are based on a standard design. This design assumes that a threaded anchor bolt is screwed into a plate nut on the Sack of an embed plate so that full development of the bolt capacity is obtained.
(Full development means that if tested to destruction the bolt will fail in tension before the threads are stripped from either the nut or the bolt.) The embed design assumes full tensile capacity of the bolt is achievable. The bolts do not have to be threaded fully within the plate nut to achieve the full tensile strength of the bolt. The amount of reduction in " full" thread engagement that is allowable depends on the bolt diameter. The acceptable reductions were incorporated into the embed design and an allcwable reduction in full thread engagement was shown on the design drawing.
All embed assemblies using the threaded nut attachment details were investigated resulting in 222 embed plates with potentially deficient thread engagement problems. Of these plates, 82 have been eliminated as containing no thread engagement deficiencies. These are listed in Attachment I as use-as-is (75), or void (7).
The remaining 140 embed assemblies in their as-built condition are not capable of withstanding the full load rating of the standard design. Although these embed plates contain deficient bolts, seventy-five (75) are repairable, and can be restored to their full design capacity. The remaining sixty-five (65) embed assemblies cannot be restored to their full design capacity and have been derated. Engineering analyses on these 65 embed plates show that twenty (20) embeds are not capable of fulfilling their design function and forty-five (45) embeds are capable of fulfilling their design function after repair work. These 45 embeds will be derated. The remaining 20 embeds will be modified to ensure that the _ load ultimately applied to the embed assemblies is within the actual capacity of the plate.
Evaluation of Reportability:
The potential failure of the embed assemblies to' fulfill their design functions could have affected adversely the safety of operations of j
the Vogtle Electric Generating Plant. The potential failure of these embeds could have affected safety-related systems supported by the embeds. This represents a significant deficiency in the construction of_ safety-related systems. Since safety-related systems may not have been able to perform their intended safety function, this concern also represents a potential ~
safety hazard.
Corrective Action:
Briefly, seventy-five (75) embed plates were dispositioned use-as-is and seven (7) embed plates were classified void. There are no problems associated with these eighty-two (82). embed assemblies.
Of the remaining one-hundred and forty (140) embed plates, seventy-five (75) embed assemblies with bolts that are repairable will be restored to 100 percent of their design capacity. This repair is accomplished by drilling a hole equal to the bolt diameter through the embed plate and nut to the end of the bolt. The bolt is then w ided to the nut and embed plate by plug welding.
For the bolts to be repairable, the bolts should 'have at least 40 percent of specified thread engagement. The 40 percent cutoff was determined by applying conservative judgement to the effectiveness of the type of welding.
An engineering evaluation of the sixty-five (65) embed assemblies containing at least one non-repairable'or inaccessible bolt has been performed.
These embed assemblies may also contain repairable bolts. These bolts are repaired to regain 100 percent of their~ design _ capacity. The bolts with less than 40 percent of'specified thread engagement are assumed to have no capacity and no repairs are performed on them.
Calculations have been completed that
indicate that forty-five (45) of these embed assemblies are adequate for present but not necessarily design loads after repair work on bolts is completed. The remaining twenty (20) embed assemblies are inadequate for present loads. Design modifications are in progress on these twenty (20) assemblies to modify the embed assemblies or the support attachments to ensure that the load ultimately applied to the embed assemblies are within the actual capacity of the assembly. The 65 embed plates will remain derated throughout the plant life. A control system is being implemented to control the use of these embed plates for the life of the plant. Tnis system will prevent any change in load or attachaent from being made without prior evaluation and concurrence from the responsible engineering group.
The system consists of notes on embed drawings (individual ~ embed plates are specifically identified), a control stamp on all related attachment design drawings using the embed plates and a control log.
Additionally, Georgia Power Company has donducted the following programs:
eCompleted training program for all GPC engineering and in-spection personnel in the fall of 1982.
eTraining sessions held for all craft supervision and foremen in the summer of 1982.
eEmphasized in training sessions past history and implications if problems are not avoided for further installations.
eFollowups in craft " gang box meetings" and inspector group meet-ings are being carried out and documented.
eSpecific certification for embed inspection has been developed for all inspectors involved with embed installation.
eFollowup audits by QA, QC, Civil groups are being performed.
l l
eNew practice of assuring removal of all blast sand from inspection hole and verification that full thread engagement can be obtained is being carried out prior to issuance of embeds to the field installation crews.
l.
ATTACHMENT 1
(.
DISPOSITION OF EMBED PLATES o
Embed Sequential Number Disposition 1
Derate 2
Derate 3
Use as is 4
Use as is 5
Use as is 6
Use as is 7
Use as is 8
Use as is 9
Repairable 10 Repairable 11 Use as is 12 Use as is 13 Use as is 14 Derate 15 Use as is 16 Use as is 17 Void 18 Use as is 19 Derate 20 Derate 21 Use as is 22 Use as is 23 Use as is 24 Use as is 25 Derate 26 Use as is 27 Use as is 28 Derate 29 Use as is 30 Derate 31 Derate 32 Use as is 33 Use as is 34 Derate 35 Derate 36 Derate 37 Derate 38 Repairable 39 Use as is 40 Use as is 41 Repairable 42 Derate 43 Derate 44 Repairable 45 Repairable 46 Use as is 47 Use as is 48 Use as is 49 Use as is 50 Use as is 51 Use as is 52 Use as is 53 54 55
Embed Sequential Number Disposition 56 57 58 59 Repairable 60 Use as is 61 62 63 64 65 66 67 Use as is 68 Use as is 69 Derate 70 Use as is 71 Use as is 72 Use as is 73 Derate 74 Derate 75 Use as is 76 Derate 77 D.erate 78 Repairable 79 Void 80 Use as is 81 Use as is 82 Void 83 Void 84 Void 85 Repairable 86 Repai rable 87 Use as is 88 Use as is 89 Use as is 90 Use as is 91 Repairable 92 Derate 93 Repai rabl e 94 Repairable 95 Repairable 96 Use as is 97 Use as is 98 Use as is 99 Use as is 100 Use as is 101 Use as is 102 Repairable 103 Use as is 104 Repairable 105 Use as is 106 Derate 107 Repairable 108 Derate 109 Derate 110 Repai rable 111 Derate 112 Derate
. Embed Sequential Number Dispositibn 113 Derate 114 Derate 115 Derate 116 Derate 117 Derate 118 Derate 119 Derate 120 Derate 121 Use as is 122 Repairable 123 Repairable 124
' Repairabl e 125 Use as is 126 Use as is 127 Use as is 128 Repairable 129 Repairable 130 Repai rable 131 Repairable 132 Use as is 133 Repairable 134 Derate 135 Repai rable 136 Repairable 137 Repairable 138 Repairable 139 Repairable 140 Repairable 141 Repairable 142 Repairable 143 Use as is 144 Repairable 145 Repairable 146 Repairable 147 Repairable 148 Repairable 149 Repairable 150 Use as is 151 Repairable
'152 Use as is~
153 Repai rable 154 Use as is
'155 Repairable 156 Repairable 157 Repairable.
158 Repairable 159 Repai rable 160 Void 161 Void 162 Repairable 163 Repairable 164 Repairable 165 Repairable
'166 Repairable
-167.
Repairable
a e
Embed Sequential Number Disposition 168 Derate 169 Repairable 170 Repairable 171 Repairable 172 Derate 173 Repairable 174 Repairable 175 Derate 176 Use as is 177 Use as is 178 Use as is 179 180 181 182 183 184 185 186 187 Derate 188 Derate 189 Derate 190 Repairable 191 Repairable 192 Repairable 193 Repai rable 194 Derate 195 Repairable 196 Repairable 197 Use as is 198 Repairable 199 Repai rable 200 Use as is 201 Use as is 202 Repairable 203 Repairable 204 Use as is 205 Use as is 206 Use as is 207 Repairable 208 Repairable 209 Derate 210 Use as is 211 212 Derate 213 Repairable 214 Repairable 215 Repairable 216 Use as is 217 Repairable 218 Repairabl e 219 Use as is 220 Use as is
- r v..
Embed Sequential Number Disposition 221 Use as is 222 Use as is Note:
Void. indicates no problems associated with an embed.
- - Indicates that embed plates will be derated to an acceptable capacity by either modifying supports or by adding plate stiffeners.
A listing of embeds by sequential number is maintained at the construction site by Mr. John Stanley or Mr. Nelson Brooks.
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