IR 05000338/1976028
| ML25196A161 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 01/03/1977 |
| From: | Gall W Advisory Committee on Reactor Safeguards |
| To: | Okrent D Univ of California - Los Angeles |
| References | |
| IR 1976028, IR 1976016 | |
| Download: ML25196A161 (1) | |
Text
ATTACHMENT TO CTE. LTR. DTD. 1/17/77 on NORTH ANNA POWER STATION,. UNITS 1 & 2 Oak Ridge National Laboratory P.O. Box X Oak Ridge, Tennessee 37830 January 3, 1977 Dr. David Okrent Energy and Kinetics Department 5532 Beetler Hall School of Engineering and Applied Science University of California Los Angeles, CA 90024
Dear Dr. Okrent:
Subject:
Review of Allegations and Inspectors Findings as Reported in NRC Investigation Report #50-338/76-28, 50-339/76-16 North Anna, Units 1 and 2 The purpose of this memo is to transmit my conclusions and recommendations regarding the reported allegations and the inspectors' findings as reported in the NRC Investigation Report on North Anna Units 1 and 2.
It is my opinion that the investigation of specific allegations as covered in the report has been sufficiently thorough to provide an evaluation of probable validity of the allegations and their possible effect on the integrity of the system.
My comments are based on the study of their report supplemented by two visits to the plant site, discussions with Stone & Webster, and Vepco staff members and with NRC Inspection and Enforcement staff in Bethesda, Maryland.
The report presents the inspectors' findings and explains the method of investi-gation upon which their conclusions are based. It does not in all cases cover corrective actions that have been taken or that may be proposed as a result of the findings.
In some cases, an evaluation of the integrity of the affected systems will depend upon the corrective action that is proposed or taken.
I have the.. following specific items of concern:
1.
Cutting of Rebar Apparently the cutting of rebar became so prevalent that Stone & Webster themselves became concerned about it and initiated actions to curtail or control such cutting.
But prior to initiation of those actions, various methods of cutting rebar were used, some of which may be detrimental to the properties of the concrete and particularly the use of carbon-arc, oxygen-flame cutting and welding rod processes which could provide high levels of heat input to the concrete.
The proposed analysis described in the licensee's response may be sufficient to establish the adequacy of the rebar but further evaluation may be necessary to deteroine if the concrete was damaged.
1121
Dr. David Okrent
January 3, 1977 2.
Allegations Concerning Fake Anchor Bolts The interference between anchor bolts and rebar may be responsible for the faking of two anchor bolts which were reported in allegations B-7 and P-1. It is also possible that some anchor bolts were cut to avoid cutting rebar which would result in the length of bolts being shorter than specified, thus affecting the strength of the anchor. It is my under-standing that ultrasonic measurements will be made to detect those bolts which were shortened.
I recommend that an evaluation be made by the licensee to determine the adequacy of any bolts which are found to be short.
3.
Welders Performing Welds Outside the Range of Their Qualifications It was established by the inspector that 30 Class 1 type welds in Units 1 and 2 were performed by welders qualified for thinner sections.
I believe all of these welds are identified in QC records and that all of the welds have been examined by radiography and found to be acceptable.
The welders were qualified on thinner sections than those cited.
The acceptance of radiographed production welds as qualification welds may be a valid pro-cedure provided the initial weld performed outside the previously qualified thickness range meets the requirements of QW-301.4, QW-302.2, and QW-305.2 of Section IX of the ASME Code,is acceptable without weld repairs, and also provided the complete weld was performed by the same welder.
One instance was observed during a visit to North Anna site in which.a single welded joint in a primary coolant loop had the weld identification numbers of twelve different welders.
I believe this would not be a satisfactory way to qualify any of the welders.
4.
32-Inch Main Steam Riser in Safety Valve Station The circumferential joints performed in the modification to the 32-inch main steam riser have been evaluated and seem to be satisfactory except in the matter of mismatch.
Permissible mismatch allowed by the Code is 3/32 of an inch.
The inspector determined in at least one case a maximum of 5/16 inch mismatch.
This is a factor of 3 over that permitted by the Code and assuming that the stress in the longitudinal direction was judged satisfactory with the permissible misalignment, the affect of mismatch would increase that stress by a factor of 3 in the case of 5/16 inch mismatch.
This pipe is probably subject to extreme axial compressive loads when the safety valves operate.
I have not found evidence that a failure of this pipe could not cause a pipe whip in the main steam valve house which would react on the penetration of the containment wall sufficiently to breach.the containment.
5. Welding Electrodes There were two items concerning improper storage of welding electrodes and one concerning use of welding electrodes prior to receipt of material certifications for them. It would be difficult if not impossible to determine 1122
Dr. David Okrent
January 3, 1977 whether welding electrodes which had been stored overnight or over a shift outside of the required drying ovens have been used in welds or in which welds they may have been used.
Furthennore, detection of the effect of excessive moisture or other contaminates principally hydrogen embrittle-ment, would be difficult to detect by means of radiography.
It would be desirable to establish that all electrodes held over were being kept for personal use.
The use of welding materials prior to receipt of proper documentation requires verification after the weld material has been used and could result in a detennination that incorrect materials were used.
This verification should be made in all cases where this was done and corrective action taken where necessary.
6.
Defective Shop Welds Two instances are reported in the inspector's findings - Items 2-C and 2-K in which noncorming shop welds in pipes performed by others were discovered by Stone & Webster quality control.
Corrective action is not indicated.
Of particular interest is the disposition of those Southwest Fabricating and Welding Company's pipe welds which were not included in the 1.5% sample examined by Stone & Webster QC and the applications in which they were used.
Approximately half of the 1.5% sample were found to be nonconfonning and presumably were repaired.
Corrective action should be applied to all other welds represented by those samples to assure con-formance with quality requirements in the Class 2 system.
7.
Improper Identification of Materials and Parts In the four reported incidents of improper identification of materials, it was possible to establish acceptability for the materials affected.
Can it be established with a reasonable degree of confidence that these reported instances are the only ones in which materials were improperly identified, or that all materials installed are in compliance with require-ments?
8.
Conclusions A.
I agree in general with the Evaluation of Findings enclosed with the transmittal of the report of the investigation.
Corrective action to correct the deficiencies in the quality assurance program must be augmented by actions to verify quality of construction already completed.
Phases 2, 3 and 4 of the investigation, I believe, were conceived for this purpose.
Phase 2 has been completed with some deficiencies yet to be resolved.
Phases 3 and 4 should form a basis for establishing the integrity of the system.
An effort should be made to establish that weLaing electrodes which were improperly stored were not used in welding of safety related systems, or that if used the effects will not compromise safety.
1123
Dr. David Okrent
January 3, 1977 B.
It is my opinion that all of the identified "quality of work" non-conformities can be corrected by corrective action.
Some of the quality control non-conformities affecting work that is already com-pleted cannot be corrected now, but the quality of the work affected may be verified by preoperational testing~ and examination, and if deficient it can be corrected.
c.
The "unresolved items" listed in Part E of the report can also be resolved by appropriate corrective actions.
D.
The licensee's quality assurance program has not functioned in accordance with established procedures and requirements in some cases.
This leads to concern about possible undetected non-conformances.
Phases 1 and 2 of the investigation constitute a thorough study of these possible deficiencies in the important safety related systems and it resulted in disclosure of some additional deficiencies which should be corrected.
E.
In my study of the report and my discussions with persons involved at the site, I have developed a number of detailed questions related to the allegations and the findings which are given in Attachment I.
F.
The allegations which were concluded to be unsubstantiated are reviewed in Attachment II to this letter and the substantiated allegations are reviewed in Attachment III.
Very truly yours, W.R. Gall WRG:mb cc: s. H. Bush J. C. Ebersole H. Etherington M. s. Plesset File -
RC 1124
Attachment I Questions 1. What degree of conservatism is used in design of the supports which depend on anchor bolts?
2.
What action will be taken to establish that the length of anchor bolts is adequate?
3.
What action will be taken to establish the integrity of concrete affected by arc, or flame cutting of rebar?
4.
What action is proposed to verify adequacy of cadwelding performed in non-conformance with requirements?
5. What corrective action will be taken on welds performed by welders out-side of their qualified thickness range?
6. If the main steam pipe fails outside of the containment, between the penetration and the stop valve, will containment be breached?
7.
What action will be taken to correct misalignment at welded joint in main steam riser?
8.
In determining acceptable thinning of pipe walls during grinding, is 0.875 x t (t = nominal thickness) used as an acceptable thickness?
n n
9.
What defects could be incurred as a result of lack of QC in-process surveillance?
10. Will the welds in the reactor coolant loops be examined by the ultrasonic method during pre-service testing?
11.
What action will be taken to ascertain whether improperly stored weld rods were used in production and may have affected quality of welds -
especially welds in the reactor coolant system?
12. What action will be taken on the Southwest Fabricating Company's welds which were not examined by S&W during their audits.
1125
Attachment II Unsubstantiated Allegations A total of 58 allegations were made by the allegors A, B, and C including the additional allegations.
Of this total, 45 were found not to be substan~
tiated for various reasons.
In the following list allegations are grouped according to the reasons for which they were not substantiated.
Reason for Not Substantiating 1. Allegations that were not substantiated because the investiga-tors examined the affected part or the records and found them to be in conformance *with the requirements.
A-3, 8, 9, 11, 12, 17, 21, B-1, 12, 13, 14, 16, 18, 20, 21, 22, 24, 25, 27, 31, and No. of Allegations P-6
In the report on Allegations A-8 and B-24, the inspector reported that quality control Nonconformance and Disposition reports showed that quality control had identified and documented instances of welders welding beyond limit qualifications.
The report does not indicate what disposition was made of these occurrences.
Inspector-identified Item 2b (Appendix 3) cites as an infraction the welding of more than 30 welds in Class 1 piping in Unit 2 by welders who were not qualified for the thickness of the pipe which they were welding.
2. Allegations which are shown by quality control records to have been identified and corrected in accordance with procedures.
A-6, 7, 13, 15, 18, B-6, 26, P-2, 4, and 5
3. Allegations that were true but either were not related to quality or were in accordance with procedures and requireme:nts.
A-14, 16, 19, B-4, 17, 30, and P-3
4. Allegations that were found to be a mistake on the part of the allegor.
A-20
5. Allegations which were not related to quality whether true or not.
B-9, C-1
6. Allegations that could not be verified by interviews with personnel, review of records, or other means and were concluded to be not substantiated. A-2, 10, B-10 and 15
These allegations having to do with falsification of records are the type which would be difficult to verify or disprove.
The investi-gators' conclusions on these items were based on review of available records and interviews with persons on the job and, though not considered substantiated, some of these violations could have occurred either without the knowledge of those interviewed or without being recorded in the documents.
1126
(continuation of Attachment II)
Allegations A-2, A-10, and B-15 were that a welding inspector and a QC inspector signed off papers without fully reviewing the work, that no one cares about quality or checks the work being done by welders, and QC inspectors had craftsmen perform fit-up inspections for them.
Allegation B-10 was that a particular field weld was performed by a different welder than the one whose number was recorded as having performed the weld. It is my opinion that the conclusions drawn by the inspector are correct, but I believe it is possible for violations of this type to occur in such a way that substantiation is almost impossible.
However, examination of the completed work by nondestructive methods can be performed to show that the work is satisfactory.
1127
Attachment III Substantiated Allegations Of the 13 substantiated allegations, four allegations (B-3, B-8, B-9, and n-11) dealt with incorrect identification numbers on materials for Class 3 systems.
However, traceability was established through the heat numbers and the materials were found to be acceptable.
Allegation A-1, cutting of concrete reinforcement steel ("rebar"), was substantiated and it was established that rebar was cut during the drilling of about 25% of the anchor bolt holes for anchor bolts for supports.
The Licensee's response to this finding indicates that an engineering analysis will be made to establish the adequacy of the concrete structures. It is my opinion that corrective action can be taken to assure the adequacy of these structures.
Allegations A-4 and B-2 dealt with the 32-inch main steam risers to the safety valve headers.
A serious problem with this incident is the verification that the joint, in one case at least, had a mis-match of 5/16 inch as compared to the Code maximum of 3/32 inch.
Bending stresses in the pipe wall as a result of such misalignment would be increased by a factor of approximately three due to this effect.
Corrective action should be taken in regard to this misalignment.
Allegation A-5 concerns lacf of in-process surveillance of piping work.
The Licensee's response indica~es that the procedures called for this sur-veillance and that it was carried out in part. It is likely that an increase in quality control personnel would be required if this is implemented as it is supposed to be, which would tend to substantiate allegations A-12 and B-31 that there are too few QC personnel.
Allegations B-7 and P-1 concerning fake anchor bolts in pipe supports are related to the cutting of rebar.
The difficulty in installing anchor bolts without interfering with rebar apparently has caused some people to subvert the requirements by faking the anchor bolt installation. It is my opinion that action should be taken to check the length of all the anchor bolts used for supports of this type to establish that the lengths are in accordance with the requirements or that deviations are permissible as established by engin-eering verification.
Allegation B-5 refers to unrecorded welds which were made in 2-inch pipe in a Class 3 system for which corrective action has not been reported. It is my opinion that if the procedures described in the response from.the Licensee are followed, any additional unrecorded welds of this type will be discovered and they should be examineq to establish thei:i:: acceptability.
Allegation B-23, holding over welding rod.
This problem seems to be very difficult to control but it is important that uncontrolled electrodes not be used in pipe welds.
The Licensee's response to this allegation does not indicate that they plan to take any corrective action on this item.
1128
(continuation of Attachment III)
Allegation B-32, improper storage of stainless steel and carbon steel pipe and valves.
It was evident during my visit to the site that many items are stored throughout the plant awaiting installation. Although this is probably only temporary storage it appears that damage could occur and dirt could be accumulated in some of the valve operators and controls which could effect their performance.
I believe corrective action i.s required on. this item.
1129