ML20093A223
| ML20093A223 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/25/1984 |
| From: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| To: | John Miller Office of Nuclear Reactor Regulation |
| References | |
| A03985, A3985, TAC-52339, NUDOCS 8407100228 | |
| Download: ML20093A223 (8) | |
Text
_
gg General Offices
- Selden Street, Berlin, Connecticut 3
P.O. BOX 270
- st a rs cow =v x,o....rra wn cow.,
HARTFORD. CONNECTICUT 06141-0270 as vrvr.
cow.=
(203) 666-6911 L
g June 25,1984 Docket No. 50-336 A03935 Director of Nuclear Reactor Regulation Attn:
Mr. James R. Miller Operating Reactors Branch #3 U. S. Nuclear Regulatory Commission Washington, D. C. 20555
References:
(1)
W. G. Counsil letter to R. A. Clark, dated September 2,1983.
(2)
- 3. R. Miller letter to W. G. Counsil, dated April 20,1984.
Gentlemen:
Millstone Nuclear Power Station, Unit No. 2 Additional Information Regarding Steam Generator Tube Inspections By Reference (1), Northeast Nuclear Energy Company (NNECO) requested an amendment to the Millstone Unit No. 2 Technical Specifications concerning steam generator tube inservice inspections.
The attached information is provided in response to the comments and questions forwarded to us in Reference (2). Attachment I responds to the information requested in items 1 and 2 of Reference (2). provides alternate language for the Technical Specifications proposed in Reference (1) and replaces Attachment I to Reference (1) in its entirety.
We trust you find the attached information satisfactory. My staf f remains available to assist you in this matter.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY
/
l.
1%MLk W. G. Counsil Senior Vice President 8407100228 840625 0
DR ADOCK 05000336 g\\
PDR L
4 A
\\
Docket No. 50-336 i
Millstone Nuclear Power Station, Unit No. 2 Additional Information
, Steam Generator Tube Inspection s
June,1984
}
- Northeast Nuclear Energy Company recognizes that tubes blocked to the automatic test equipment can typically be inspected manually. All tubes can be inspected manually, however equipment was developed to automatically and remotely perform the inspections of steam generator tubes to avoid the personnel radiation exposure involved with the inspections. The radiation levels present in the steam generators at Millstone Unit No. 2 typically result in an exposure of 0.3 - 0.5 person-rem for each steam generator tube end which is manually inspected. NNECO considers such exposures unjustified for those tubes for which a high level of confidence exists regarding their integrity.
The only tubes to be exempted from inspection shall be those tubes that are located more than five (5) lines and eight (8) rows from any flawed tube. This criterion assures that as many as 92 tubes free of flaws will surround a tube proposed to be deleted from the insoection pattern. Experience at Millstone Unit No. 2 has demonstrated that steam generator tube defects tend to be localized and readily grouped into patterns. As such, the criterion outlined above provides an appropriate basis on which to draw conclusions regarding the integrity of an uninspected steam generator tube.
Steam generator tubes ^which are scheduled for inspection but are deleted from the inspection pattern are listed. The record of these tubes is then introduced into the plant inspection and work control system. This system has been utilized in the past to ensure a followup inspection of steam generator tubes.
Specifically, during the Cycle 5 refueling outage, steam generator tube degradation was identified which required a 100% inspection in accordance with Category C-3 of Technical Specification 4.4.5.1.2.c.
During the inspection, 54
. tubes in an area of the tube bundle scheduled for inspection were inaccessible to the automatic testing equipment without extensive modifications to the equipment which would have necessitated additional personnel radiation exposure.(l) It was mutually agreed to by(2)our staffs that NNECO would inspect 22 of these tubes during the next outage.
These tubes were entered into the plant inspection and work control system which ensured that appropriate personnel responsible for inspection remained cognizant of the need to inspect these specific tubes during the subsequent outage.
Steam generator tube inspections are planned in advance in accordance with the requirements of the technical specifications. The specific tubes to be inspected are chosen from areas of the tube bundle where defects have historically been identified and include the tubes which had detectable wall penetration and were not plugged. This is required by Technical Specification 4.4.5.1.2.b.
As part of the inspection process, a full size, numbered template is fabricated.
The templates are installed on the tube sheet face prior to beginning the
~ inspection. The template defines the tubes to be inspected. It is secured in place with plugs which are installed into certain steam generator tubes. Prcper positioning of the template is verified by identification of specific ' landmarks' on the tubesheet. -
- The examiner or equipment technician who positions the inspection probe carrier
- views the position on closed circuit television. The line and row numbers on the template identify the tube end being entered. This individual initials the data sheet indicating he has verified the location of the tube inspected.
Each location of a defect is independently verified by a second examination of
' the suspect tube. This verification identifies that the flaw " signature" seen on the original examination is, in fact, present at the line/ row originally identified.
Discrepancies, if any, are resolved by identifying the extent of the inspection
. which is suspect and reexamining all tubes suspected of improper identification.
. All inspection work is performed in accordance with station procedures for
. Quality Assurance (QA) work and is subject to audit, surveillance and monitoring by QA personnel.
Future advances in automated tooling hold the promise of eliminating the need for the tubesheet templates.
Micro-processor controlicd positioners should
' result in reduced personnel radiation exposure and increased assurance of accurate inspection location.
(1)
W. G. Counsil letter to R. A. Clark, dated February 12,1982.
(2)
E. L. Conner letter to W. G. Counsil, dated March 5,1982.
L
Docket No. 50-336 l'
Millstone Nuclear Power Station, Unit No. 2 Proposed Rewording of Technical Specification Change Request 1
4 June,1984
s.'
t s
TABLE 4.4-5 i
25 MINIMUM NUMBER OF STEAM GENERATORS TO BE
((
INSPECTED DURING INSERVICE INSPECTION c$
g;
[
Tieservice Inspection Yes 5
-4 No. of Steam Generators per Unit Two ro f
First Inservice Inspection One l
Second & Subsequent Inservice Inspections One I
I Table Notation:
((
1.
The inservice inspection may be Ifmited to one steam generator on a rotating sc..edule 2,
encompassing 3 N % of the tubes (where N is the number of steam generators in the plant) if the results of the first or previous inspections indicate that all steam generators n
are performing in a like manner. Note that under some circumstances, the operating con-ditions in one or more steam generators may be found to be more severe than those in other steam generators.
Under such circumstances the sample sequence shall be mcdified to inspect the most severe conditions.
6 4
~
-3, ls.s e r
w;.
N
,F TAtill? 4.4 G tn
.N STE AM GENrnAT0ft TUI1E INSPECTION o
e IST S AMI't.E INSP[CilON 2ND SAMPt.E INSPECTION 3:10 SAMPLE INSI'ECTION c
i3 Sampfe Sete Result Actino notuireil Iteusi Action Itcriuirevi lictutt Action Ilettuired
-4 to A minimum of C.1 None N/A N/A N/A N/A S luhes per S. G.
C -7 sepete defeettve C-1 None N/A N/A-RePale defective C-I None d ons e
l2';i:1'".;;1.
c-2
d'~'i-
'" n i - --
1r this S.C Perform action foe R
C-3 C-3 reusit of first b
sample f
Perlotm aClion for w
C-3 C-3 ren,!: of first N/A N/A sample C-3 anspect alt -
Att ottier tubes in this 5. G..
S. G s are None N/A N/A repair defective tubes C-1 and inspect 25 tubes 0"*' S U 5 Perform action for N/A N/A in each other 5.G.*
See Note 1.
C-2 liut no C-2 result of secontf ml<litional sample Prompt notifi afiort S G. are to NnC purusant C-3 to specification Aetilitional Inspect all -
G.9.I
- 1. G. is C-3 tubes in each 5.G and repair defective tubes *. Prompt N/A N/A notification to NRC pursuant to Specification 6.9.1.
See Note !.
~
S = 3 % WIiese N is efie emmt cr ni steam generators in the unit. and n is the numlier of steam generators Inspected
'I"'i"g an inspection n
- Repair of defective tubes shall be lir ll.ed.to plugging with the exception of those tohes which may be sleeved. Tubes with dc! ctive sleeves shall be plugged
se:
, '_ ( _
h-Table 4.4-6 Table Notation o:
.lb Tubes required ta be inspected pursuant to Action C-3 which are blocked by the remote inspection equipment may be excluded from the inspection pattern performed pursuant to Action C-3 provided that no tube within 5 lines or 8 rows is degraded. No more than 0.5 percent of all tubes in the K
steam generator shall f all into this category.
L
-MILLSTONE - UNIT 2 3/4 4 7e 4