ML20102A413
| ML20102A413 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/04/1985 |
| From: | Lundvall A BALTIMORE GAS & ELECTRIC CO. |
| To: | John Miller Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8502080354 | |
| Download: ML20102A413 (4) | |
Text
[J B ALTIMORE G AS AND ELECTRIC COMPANY t
P.O. box 147 5 B ALTIMORE. M ARYLAND 21203 ARTHun E. I.UNDVALL,Jn.
v" February 4,1985 U. S. Nuclear Regulatory Commission Division of Licensing
' Washington, D.C. 20555 ATTENTION: Mr. James R. Miller, Chief Operating Reactors Branch #3
SUBJECT:
Calvert Cliffs Nuclear Power Plant.
Units Nos.1 & 2; Docket Nos. 50-317 & 50-318 Inservice Inspection Program Request For Relief from ASME Code Section XI Requirements Determined to be Impractical Gentlemen:
In accordance with 10 CFR 50.55 a(g)(6)(i), we are requesting an exemption from ASME Code Section XI requirements that have been determined to be impractical.
In accordance with NRC Staff Guidance letter dated November 24, 1976, the information concerning the exemption request is presented herein.
It has been determined that certain examination requirements for reactor coolant pump casings are impractical to perform.
ASME. Code Section XI requires volumetric
' examination of. casing welds and visual examination of internal pressure boundary surfaces of ' one pump casing be performed during each inspection interval.
The impracticality of performing these exams is not unique to Calvert Cliffs. This has initiated generic studies to evaluate the need for inspection and to develop ~ specific inspection techniques. To date, no technique has been proven practical for performing volumetric Inservice Inspection of the Type E pump design installed at Calvert Cliffs.
Visual examination of the internal pressure boundary surfaces would be limited due to the -
{j 2 internal configuration and radiation fields. Pump disassembly for the sole purpose of conducting a very limited visual examination is impractical in light of the manhours and radiation exposure that would be' expended.
A tabulation of the information required for this request is presented below.
I.
COMPONENT FCR WHICH RELIEF IS REQUESTED:
.~: en
[l A. ~ Name and Number
- e s:
[
Calvert Cliffs Unit I reactor coolant pumps #11A, #11B, #12A, and #12B
~'
ed Calvert Cliffs Unit 2 reactor coolant pumps #21A, #21B, #22A, and
- 221 ' All pumps are identical in design and function and are Byron-
. SE.
Jackson Type DFSS Reactor Coolant Pumps, Serial Numbers 681-N-0437
- through 44, Size 35 X 35 X 43.
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4 Mr. James M. Miller i
- February 4,1985
-Page 2 -
B.
Function
-.Each Calvert Cliffs unit has four reactor coolant pumps which are
- welded to the 30" recirculation loop.
These pumps function during normal reactor operation to provide forced recirculation through the Core.
C.
Code Class Current ISI Class:
Class 1 Original Design:
ASME Code Section Ill,1965 Edition with Addenda through Winter 1967, Class 1
. II. CODE REQUIREMENT FROM WHICH RELIEF IS REQUESTED:
- ASME Code Section 'XI 1974 Edition with Addenda through Summer 1975 examination categories B-L-1 and B-L-2 require volumetric examination of Lcasing; welds and visual examination of internal pressure boundary surfaces of one pump casing in each of the pump. groups performing similar; system V
- functions each inspection interval. These examinations are impractical for
- the reactor coo! ant pumps at Calvert Cliffs-Units-I and 2 and relief is,-
e therefore, requested as provided by 10 CFR 50.55a(g)(6)(i).
III.'. : SUPPORTING INFORMATION -
A.1 The.' design configuration; of the pump Lcorresponds.to a Type E pump illustrated in Figure NB-3442.5-1 (1977. Edition, ASME Code Section III).-
No practical technique currently exists' to perform Inservice Inspection;
. Radiographic. Examination (RT) or-Ultrasonic Examination (UT) of this
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pump type.~
LB. The presence of thel diffuser vanes precludes conventional RT. The vanes prevent placement of the RT film cassettes inside-the pump'(as does the radiation field in terms' of ; radiographic-film and. personnel radiation exposure). Placement of the film on the outside of the pump is feasible,'
V3.,
E but..there his no. radiographic source' suitable for. placement inside.the
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+ pump. ' Standard isotopic radiation sources are too weak to penetrate _the thick casting and background radiation from the inside surface of the i pump' would diminish' sensitivity. - Special' strong isotopic sources.would -
- be~ lm' practical to' handle and position inside the pump due to personnel
,; n >
radiological exposure from the radiographic source'itself. The recently
= developed Miniature Linear Accelerator (MINAC) was considered, but the c- ?
L. Type E. pump design precludes positioning of the accelerator:inside.the :
- pump.. Double ^ wall radiography; utilizing the_ MINAC has alto been
- considered with some hope ;of attaining meaningful radiographs -of a"
- portion lof the casing welds. ?This technique has not been qualified to-j date and appears to be some time off, if, at all possible.
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. Mr. James R. Miller -
g, February 4; 1985-
- Page 3.
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- C. The
- coarse grain structure inherent in thick stainless steel castings
_ precludes the..use of conventional UT. Future developments in ultrasonic
- techniques may provide a method to examine thick stainless steel casting and if developed, this would be preferred over the difficulties and dangers
'of f thick wall radiography. We are hopeful that the Ultrasonic Data 1 Recording and Processing System (UDRPS) technology may provide some
=
- breakthrough to stainless steel casting UT.
- D.
The pump casing is fabricated from cast stainless steel (ASTM A351, s
Grade : CF8M).' ~ The material is essentially a cast-type 316 stainless
' steel.,This material is widely_ used in the nuclear industry and no l industry; failures. of this type material in reactor coolant pumps have
' been noted.
The-presence of delta ferrite (typically 15% or more)
Limparts. increased resistance to intergranular stress corrosion cracking c
- (IGSCC). The delta ferrite also improves resistance to pitting corrosion.
- E.f Report 1 Number ERP-06-102, Revision 0,' August 1983, prepared for the
~ Electric Power Research Institute by NUTECH Engineers, incorporated,-
- concludes that::
l.:Bdsed - on the, generic. pump casing analysis, there is
~,'
justification for y the : extension of the pump-casing
. examination up to 15 years.
' ? 2. ; Plant-unique analysis'will show greater margins of safety.1
- 3 7The : tearing modulus analysis shows that large,' final flaw sizes.can' be tolerated in.the. pump casing before fracture is
- predicted.-
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4.
The-recent_10-year.; Inservice -Inspection of several pump-casingsE(Type F) indicates no detectable flaw growth from m
' base line inspections ~, which corroborates the above analytical -
- conclusion.,
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Pump disasse'mbly(for#.the ' sole ' purpose oficonducting -a.very limited ~
1 visual examinationiof 1the ~ interior ' pressuret boundary (surfaces iof. a -
' '; reactor coolant' pump which,"for"the'most part,'has'an as-cast surface '
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rtexture is fruitless, particularly;in light of; the manho'urs and radiation sexposure that would be expendeda ",
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.w LMr. James R. Miller 1
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, February 4,1985
- Page 4
. G.
Over.1,000 manhours. and over 50 person / rem is estimated to disassemble, visually-inspect, and reassemble one reactor coolant pump.
The manhour ostimate is based only on on-site outage work performed by Maintenanc' Operations, and Nondestructive Testing personnel. The
. estimate.c,s not-include engineering time or pre-outage job planning.
Additionahy,-manhours and person / rem will be expended by Radiation Protection personnel providing direct coverage. The time required to
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' perform. the disassembly.and inspection would be approximately two
- weeks of critical path time. Most of the work would be performed under
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- full face mask conditions.
IV.. IN IJEU OF TESTING
- A. [The. pump interior will be inspected to _ the extent practical (in
- recognition of the vanes therein) should the pump be disassembled for any other ' reason.
B. lThe reactor coolant ' pumps shall be hydros.atically tested per the requirements of ASME Code Secion XI.
/
!The, need -for,this. exemption _ was recognized during our initial Inservice Inspection
- program development.- 'At that! time our NRC" Resident-Inspector requested that we -
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, L forego ; exemption request - submittal in' hope. that techniques.might: be developed.and '
. qualified by the; end.of-our firsti 10-year interval. : It is now apparent that no such
- technique applicable to our pumps will be available before our first interval concludes.
l We' have determined' that this request constitutes an amendment for Calvert Cliffs Unit 1Nos.:1'and 2, pursuant tojl0 CFR 170.21. fAccordingly, Baltimore Gas & Electric Check-
' No. B396518 in the. amount of $150.00 is remitted herewith.
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kShould[youlhave[furthek questions regarding(this Lmatter, please do not hesitate.to
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- Very truly.yo'urs,
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AEL/BCR/gla--
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- cc -'D.;A2 Brune, Esquire L G. F. Trowbridge, Esquire c
D.' H. 3af fe, NRCj T. Foley, NRC -
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