ML19011A152
| ML19011A152 | |
| Person / Time | |
|---|---|
| Issue date: | 01/11/2019 |
| From: | Stephen Cumblidge NRC/NRR/DMLR/MPHB |
| To: | |
| Rezai A, NRR-DMLR 415-1328 | |
| References | |
| RIS-18-006 | |
| Download: ML19011A152 (9) | |
See also: RIS 2018-06
Text
NRC REGULATORY ISSUE SUMMARY 201806
CLARIFICATION OF THE REQUIREMENTS FOR REACTOR
PRESSURE VESSEL UPPER
HEAD BARE METAL VISUAL EXAMINATIONS
NRC / Industry NDE Technical
Information Exchange Meeting
January 1517, 2019
RIS on Upper Head Inspections
As discussed in the 2017 meeting, the NRC has
published a RIS clarifying upperhead inspection
requirements
The goal of the RIS is to reiterate that the VE
examination acceptance criteria are not dependent
on the material used for the upper head
The NRC has been enforcing N7294 as described
in the RIS and the RIS does not describe new
requirements
2
BMV Relevant Conditions
From N7294
Relevant conditions for the purposes of the VE
shall include areas of corrosion, boric acid deposits,
discoloration, and other evidence of nozzle
leakage
Components with relevant conditions require
further evaluation. This evaluation shall include
determination of the source of the leakage and
correction of the source of leakage in accordance
with 3142.3.
Indications of Possible Nozzle Leakage
A nozzle with relevant conditions indicative of
possible nozzle leakage shall be acceptable for
continued service if the results of supplemental
examinations [3200(b)] meet the requirements of
3130.
A component with relevant conditions indicative of
possible nozzle leakage shall be acceptable for
continued service if a repair/replacement activity
corrects the defect in accordance with IWA4000.
Comments and Comment Resolution
The NRC received 10 Comments on the RIS
Several were clarifications The NRC agreed or
partially agreed with five comments
The NRC disagreed with five comments
The comments and recent proposed alternatives
to N7291 point to possible useful code actions
5
Leaks From Above are not Relevant
Boric acid deposits from other sources are not
considered relevant indications under the scope
of N7294.
NRC Paragraph 3141(c) states Relevant
conditions for the purposes of the VE shall
include evidence of reactor coolant leakage,
such as corrosion, boric acid deposits, and
discoloration. Leakage from any source can
produce relevant indications.
6
N7294 is too Strict
If it is very clear that the leakage has come from sources other
than the nozzle the requirements of the Code Case N7294 to
perform a subsequent VE of previously obscured surfaces after
cleaning prior to return to service and again in the subsequent
refueling outage should be adequate
While the NRC may agree that this approach may be adequate in
some cases, it is not currently in compliance with N7294, and
would require a proposed alternative to be used
7
More Guidance
In lieu of this RIS, the ASME Code Committee
should be engaged to revise Code Case N7294 to
include additional details and to clarify the type of
reactor head (i.e., replacement and material such as
Alloy 690).
NRC Response While clear definitions of cleaning
methods in a future revision of ASME Code Case N
729 would provide improved guidance for licensees,
future revisions of ASME Code Case N729 are
beyond the scope of the RIS
8
Path Forward
The NRC would review ASME Code Actions taken
to add more detail to N7294
Different criteria for PWSCCresistant and
PWSCCvulnerable heads may be useful
9