ML20239A704
| ML20239A704 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/21/1987 |
| From: | Gucwa L GEORGIA POWER CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| SL-3649, TAC-66940, NUDOCS 8712300011 | |
| Download: ML20239A704 (2) | |
Text
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Georgia Power Cornpany 333 Piedrnont Avenue
- A Atlanta, Georgia 30308 Telephone 404 526-6526 Maihng Address:
Post Office Box 4545 Atlanta, Georgta 30302 -
L Georgia Power L T. Gucwa ihe m/mm ekctic system Manager Nuclear Safety and Licensing SL-3649 0623m X7GJ17-V000 December 21, 1987 U. S. Nuclear Regulatory Commission ATTN:
Document Control Desk Hashington, D.C.
20555 PLANT V0GTLE - UNIT 1 NRC DOCKET 50-424 OPERATING LICENSE NPF-68 DERATED EMBED PLATES Gentlemen:
During construction of Georgia Power Company's (GPC) Plant Vogtle Unit 1, the questionable installation of certain embed plates caused a number of the embed plates to be abandoned or derated.
This problem was reported to NRC Region II in Deficiency Evaluation Report DER-020 which served as the basis for the enclosure to GPC letter GN-239 dated July 1, 1983.
A copy of the aforementioned letter, which specifically identifies the derated embeds, is enclosed for your convenience.
Georgia Power Company committed to control the use of the derated embed plates for the life of the plant.
During the construction. phase, monthly walkdowns of the derated embeds were conducted due to extensive field routing of pipes and placement of supports.
These walkdowns were conducted to ensure that only support members specifically designed for the smaller allowable loads of the derated embeds were attached.
A control system, which. was discussed in GPC letter GN-239, was implemented by GPC to control the use of the derated embeds and consisted of notes on embed. drawings (individual embed plates are specifically identified), a control stamp on related attachment design drawings using the embed plates, and a control -log.
The monthly walkdowns of the derated embeds are a part of the control system in that they are identified on several plant drawings.
Now that Plant Vogtle Unit 1 is in operation, the monthly walkdowns of the derated embeds are no longer necessary.
Accordingly, GPC has discontinued performing the monthly walkdowns.
The walkdowns were deemed to be no longer necessary since permanent physical modifications are controlled by Design -
Change Packages (DCPs) and are approved prior to implementation.
The DCP checklist used by the design engineer has' been revised to include a step for the reviewer to determine if a derated embed is affected by a plant modi fication.
Further, it - should be noted that several of the derated embeds are located inside containment.
Monthly walkdowns inside containment would have resulted in undue radiation exposure to personnel performing the 8712300011 871221 PDR ADOCK 05000424
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GeorgiaPower d U. S. Nuclear Regulatory Commission December 21, 1987 Page Two walkdowns, which we believe would be contrary to the principle of "As Low As Reasonably Achievable (ALARA)".
NRC's concurrence with GPC's position on discontinuing the monthly walkdowns of the derated embeds at Plant Vogtle Unit 1 is requested.
It is requested that this submittal be forwarded to the Office of Nuclear Reactor Pegulation for review and concurrence.
A copy of this submittal has been forwarded to NRC Region II for their review.
Should you have any questions in this regard or require any additional information, please contact this office at any time.
Sincerely,
- f &
L. T. Gucwa JAE/Im
Enclosure:
1.
GPC letter GN-239 dated 7/1/83 to the NRC c: Georqig Power Company Mr.
P. D. Rice Mr. J. P. O'Reilly Mr. G. Bockhold, Jr.
Mr. C. H. Hayes Mr. J. E. Swartzwelder GO-NORMS Southern Company Services Mr. R. A. Thomas Mr. J. A. Bailey Shaw. Pittman. Potts & Trowbridge Mr. B. H. Churchill, Attorney-at-Law IEngfman. Sanders._Lockerman & Ashmore Mr. A. H. Domby, Attorney-at-Law U. S. Nuclear Regul31ory Commission Dr. J. N. Grace, Regional Administrator Mr. J. B. Hopkins, Licensing Project Manager, NRR (2 copies)
Mr. J. F. Rogge, Senior Resident Inspector-0perations, Vogtle 0623m
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g ENCLOSURE TO GEORGIA POWER COMPANY LETTER SL-3649 pNb'I.T. [Os As 4ata Geoeg a 1c102
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Wqtme Pro,ect July 1. 1983 United States' Nuclear Regulatory Coninission File: X78G03-M25 Office of Inspection and Enforcement Log:
GN-239 Region !! - Suite 3100 101 Marietta Street Atlanta, Georgia 30303 i
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 enbeds.
Georgia Power Company has conducted an evaluation and concluded that tnis 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.
Yours truly, D.'O. Foster 00F/CWH/skr xc:
U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C.
20555 i
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, !!!
J. L. Vota W. F. Sanders R. E. Folker (0r.
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EVALUATION FOR A SUBSTANTIAL SAFETY HAZAR0 EVALUATION FOR A SIGNIFICANT DEFICIENCY l
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Etteds 1982 - Anchor Bolt Thread Engagement Initial Report:
On April 26, 1982 Mr. C. W. Hayes of Georgia Power Company notified Mr. Virgil Brownlee of the USNRC of a potential deficiency concerntng the lack of anchor bolt thread engagement in certain types of erted assemblies.
Interim reports were also filed with the NRC.
1 Backt,round Information:
l During an inspection of previously accepted threaded anchor 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 eeed assemblies. This was reported to the NRC as a potential deficiency (see above).
Eeed asseelies are placed in concrete to provide a surface for attaching structural steel used for various purposes, including such items as piping. HVAC ducts, platfonus, or electrical tray supports. The capability of the threaded anchor eded assembly to support its attachments under the applicable load coeinations 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 the 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
)
Pouer Campaq's Vogtle Electric Generating Plant indicated that two-hundred and taenty-two (222) assemblies had the potential of anchor bolt thread espegement problems.
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Enatneering Evaluation:
The threaded anchor emed asseelies issued on the Vogtle Project are based on a standard design. This design assumes that a threaded anchor bolt is screwed into a plate nut on the back of an eded 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 esbed design assumes full tensile capacity of the bolt is achievable. The bolts do not have to be threaded fully within the plate not 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 l
incorporated into the embed design and an allowable reduction in full thread engagement was shown on the design drawing.
All eebed assemblies using the threaded nut attachment details were investigated resulting in 222 eded plates with potentially deficient thread engagement problems. Of these plates, 87 have been eliminated as containing no thread engagement deficiencies. These are listed in Attachment I as use-as-is (75), or void (7).
The remainirg 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 c.an be restored to their full design capacity. The remaining sixty-five (65) oded assemblies cannot be restored to their full design capacity and have been dorated. Engineering analyses on these 65 embed plates shoiv that twenty (20) seeds are not capelle of fulfilling their design function and forty-five (45) eeheds are capable of fulfilling their design function after repair work. These 45 ededs will be # rated. The remaining to ad eds will be modified to ensure that the load ultimately applied to the seed assselles is within the actual capacity of the plate.
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Evaluation of Deportability:
The potential failure of the embed assemblies to fulf til their design functions could have affected adversely the safety of operations of the Vogtle Electric Generating Plant. The potenttal failure of these embeds could have affected safety-related systems supported by the emeds. 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) eeed plates were dispositioned use-as-is and seven (7) eded plates were classified void. There are no problems associated with these eighty-two (82) embed assemblies.
Of the remining 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 belt diameter through the embed plate and nut to the end of the bolt. The bolt is then welded 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) emed asseelies containing at least one non-repairable or inaccessible bolt has been performed.
These embed asseelies may also contain repatrable bolts. These bolts are repaired to regain 100 percent of their design capacity. The bolts with less then 40 percent of specified thread engagement are assumed to have no capacity and no repairs are perfonned on thee. Caleviations have been completed that E-4
indicate that forty-five (45) of these emed assemblies are adequate for present but not necessarily design loads af ter repair work on bolts is completed. The remaining twenty (20) embed asseelies are inadequate for present loads. Design modifications are in progress on these twenty (20) asseelies to modify the embed asseelies or the support attachments to ensure that the load ultimately applied to the eeed asseelies are within the actual capacity of the assembly. The 65 embed plates will remain 1erated throughout the plant life. A control system.is being implemented to control the tse of these embed plates for the life of the plant. This system will prevent sny change in load or attachment from being made without prior evaluation and concurrence from the responsible engineering group.
The system consists of notes on eeed drawings (individual eeed plates are specifically identified), a control stasp on all related attachment design drawings using the embed plates and a control log.
Additionally, Georgia Power Company has conducted the following programs:
eCompleted training program for all GPC engineering and in-specting personnel in the fall of 1982.
eTraining sessions held for all craft supervision and foremen in the summer of 1982.
eEsphasized 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 eeed inspection has been developed i
for all inspectors involved with embed installation.
eFollowup audits by QA, QC, Civil groups are being performed.
i 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 eeeds to the field installation crews.
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i Cr EN' 1 D 15 PUS ! T ! 0'4 '.' E uS E D ;, 3, :
Embed Sequential Number Djj;,, <,(t c,r 1
Derste 2
Cerate 3
.se 45 15 4
'Jse as is 5
use as is 6
Use is is 7
Use ss is 8
Use as is 9
Repatrable 10 Repa'rable 11 Use as is 12 Use as is 13 use as is la 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 af is 25 Derate 26 Use as is l
27 Use as is 28 Derate 29 Use as is 30 Derate 31 Derate 32 Use as is 33 Use as is 34 Dera te 35 Dera te 36 Derate 37 Dera te 38 Wepairacle 39 Use as is 40 use as is 41 Repatrable 42 Derate 43 Derate 44 Repairable 45 Repairable 46 Use as is j
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 e
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Embed Sequential Number Disposi'.icn 56 57 58 59 60 Reoairable 61 Use as is 62 63 64 65 66 67 68 Use as is 69 Use as is 70 Derate 71 Use as is 12 Use as is 1
73 Use as is 74 Derate 75 Derate 76 Use as is 77 Derate 78 Derate i
79 Repairable i
80 Yoid 81 Use as is 82 Use as is 83 Void 84 Void 85 Void 86 Repairable 87 Repatrable 88 Use as is 89 Use as is 90 Use as is j
91 Use as is l
92 Repat rable i
93 Derate Repairable
')4 95 Repatrable 96 Repat rable 97 Use as is 98 Use as is 99 Use as is 100 Use as is 101 Use as is 102 Use as is 103 Repairable 104 Use as is 105 Repatrable 106 Use as is 107 Derete 108 Repatrable
{
Derate i
109 Derste 110 i
111 Aapafrable 112 Seeste esente E-7
~
Embed Sequential Number Disposition 168 Derate 16!
Repatrable 170 Reptirable 171 Repairable 172 Derate 173 Repa t rable 174 Repairable 175 Derate 176 Use as is 177 Use as is 178 Use as is 179 1
180 181 182 183 184 j
185 186 187 Derate 188 Cerate 189 Derate 190 Repa t rable 191 Repairable 192 Repatrable 193 Repairable 194 Derate 195 Repairable 196 Repairable 197 Use as is 198 Repat rable 199 P.epairable j
200 Use as is i
201 Use as is
]
202 Repairable 203 Repatrable 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 i
218 Repairable 219 Use as is 220 Use as is E-8
Embed Sequential Number Ciscositun 113 Derate 114 Derate 115 Derate 116 Derate 117 Derate 118 Derate 119 Derate 120 Derate l
121 Use as is 122 Repatrable 123 Repa i rable 124 Repairab e 125 use as is 126 Use as is 127 Use as is i
128 Repairable j
129 Repa t rable 130 Repa t rable 131 Repatrable 132 Use as is 133 Repairable 1 34 Derate 135 Repairable 136 Repatrable 137 Repatrable 138 Repairable 139 Repairable i
140 Repatrable 141 Repairable 142 Repairable 143 Use as is 1
144 Repairable i
145 Repatrable 146 Repairable 147 Repairable 148 Repat rable 149 Repairable 150 Use as is 1
151 Repairable 152 Use as is 153 Repa1.able 154 Use as is 155 Repairable i
156 Repairable i
157 Repairable 158 Repairable 159 Repairable 160 Void 161 Void 162 Repatrable 163 Repairable 164 Repatrable 165 Repatrable 155 Rapatrabla 167 Aspairsble E-9
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9 Er.1 bed 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 Srooks.
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