ML19309G130
| ML19309G130 | |
| Person / Time | |
|---|---|
| Site: | Black Fox |
| Issue date: | 04/07/1980 |
| From: | Bishop C NRC ATOMIC SAFETY & LICENSING APPEAL PANEL (ASLAP) |
| To: | NRC ATOMIC SAFETY & LICENSING APPEAL PANEL (ASLAP) |
| Shared Package | |
| ML19309G127 | List: |
| References | |
| ALAB-589, NUDOCS 8005050013 | |
| Download: ML19309G130 (5) | |
Text
8005050g1).
. /~N
\\-]
y UNITED STATES OF AMERICA
~
NUCLEAR REGULATORY COMMISSION
'l ATOMIC SAFETY AND LICENSING APPEAL BOARD 7
Alan S.
Rosenthal, Chairman Dr. John H. Buck Michael C. Farrar
)
In the Matter of
)
)
VIRGINIA ELECTRIC AND POWER COMPANY)
Docket Nos. 50-338 OL
)
50-339 OL (North Anna Nuclear Power Station
)
Units 1 and 2)
)
)
MEMORANDUM AND ORDER April 7, 1980 (ALAB-589)
During the course of our review of the Licensing Board's 1/
decision in this operating license proceeding, we raised two safety issues on our own initiative.
See ALAB-491, 8 NRC 245 (1978).
Last June, we conducted an evidentiary hearing on both issues.
We disposed of one of them earlier this year by deciding that the continuing settlement of the ground be-neath the service water pumphouse did not pose an unmanageable problem.
ALAB-578, 11 NRC __ (February 11, 1980).
~~1/
That Board had found no barrier to the award of operating licenses for both units.
The Unit 1 full-power license was issued on April 1, 1978 and commercial operation of that unit began on June 6, 1978.
Nc license for Unit 2 has yet been issued.
. At that time, we reserved decision on the other plant safety issue, that relating to turbine missiles (i.e.,
to the likelihood that pieces of the turbine would break off and cause unacceptable damage -- in terms of safety conse-quences -- to other plant systems).
We held up our decision because new developments bearing on the resolution c. the turbine missile question had been brought to our attention.
Specifically, cracking of turbine disks had been uncovered at a number of facilities employing equipment made by the same 2/
manufacturer that supplied the North Anna turbines.~~
We tentatively scheduled a supplemental hearing to con-sider that new information.
See our unpublished memorandum of February 12, 1980.
The applicant requested, however, that before we went ahead with the hearing we first consider whether our concerns might be satisfied by certain information it 3/
would furnish us in writing.-~ Upon reviewing that material together with the NRC staff's appraisal of the matter, a majority of this Board made three determinations which were embodied in an unpublished order issued on March 3, 1980.
First, the submissions went "a long way toward establishing that operation of North Anna 1 need not be halted now in order to conduct a lengthy inspection of its turbine".
- Second, 2/
Additionally, we were advised that the manufacturer was
~~
re-analyzing the potential amount of energy associated with the missiles created by turbine disk disintegration.
3/
Otherwise, that information would have formed the foundation
~~
for testimony at the hearing.
. there consequently was no need to proceed witn the hearing (at least as it was then scheduled).
Third, the applicant and the st'aff should be called upon to explain further (again in writing) the underpinnings of certain analyses
~4/
employed by them in arriving at their conclusions. ~
We now have that further explanation before us.
It furnishes necessary support for the conclusions previously advanced.
On the basis of it, we are able to determine that the turbine disk cracking being experienced elsewhere is not likely to occur to any hazardous extent at North Anna Unit 1 prior to the next refueling shutdown, now scheduled for December of this year.
That is because the development of the cracking phenomenon is time-related; in light of the number of hours the Unit 1 turbine will have been in opera-tion, we can say with reasonable assurance on the basis of the record now before us (reflecting experience elsewhere) that any cracks that might develop would not have had time 5/
to approach critical size by then.-~~ The applicant has made a commitment to have the turbine inspected during the December 4/
Dr. Buck dissented from ao much of the March 3 order as
~~
sought this additional information.
In his view, not shared by the majority, the information already supplied was suf ficient to permit continued operation of Unit 1 until the next scheduled shutdown (see pp. 3-4, infra).
~~5/
As noted above, Un'it 2 has not yet begun oparation.
Our final decision on the turbine missile question should thus be rendered long before disk cracking might become a problem for that unit.
- 6/
shutdown;-
that inspection will be capable of detacting
~
any substantial cracking that may actually have occurred.
And the results of the inspection will furnish a foundation for new judgments about the safety of any operations beyond that point.
For now, the recent developments relating to the turbine missile problem do not require either that opera-tion of Unit 1 be halted or that Unit 2 be kept out of opera-tion.
This is not to say, however, that we now have the final word on the long-term significance of the disk cracking pheno-menon.
For example, we do not know the extent of its impact on the continuing validity of certain portions of the evidence that was adduced before us at the hearing last year, which dealt with the turbine missile question in terms of the plant's full lifetime.
Indeed, it will be some time before the extent 7/
of that impact will be known.-
of at least equal importance,
~
there is nothing now before uc which might explain the basic reasons for the surprisingly early crack formation in turbine blades of the same type and manufacture as those used in the North Anna units.
We will expect the papers supplied to us 6/
See "VEPCO's Responses to Site Specific General Questions on * *
- Unit 1",
Nos.
I.B, II and IV.
Needless to say, any proposed deviation from that commitment must be immediately reported to us.
i
~7/
The applicant's present estimate is that it will be this October before it will be able to advise us finally either on that score or with regard to the results of the reanal-ysis which is being done on the subject of missile energy
-(see fn.
2, supra).
. later this year to address in some detail what has been ascer-tained regarding the causes of the early cracking, as well as the steps being taken to correct the problem.
In the circumstances, we will continue to defer our de-8/
cision on the turbine missile question.-
Implicit, of course, in our taking such a step is our tentative conclusion, based on our study of the record thus far, that the safety concerns that motivated us to call the hearing in the first place were otherwise adequately addressed in the testimony.
Final decision deferred.
It is so ORDERED.
FOR THE APPEAL BOARD Q LMnrM C. Je Bishop
\\
Secre ry to the Appeal Board
-8/
It remains to be seen whether a supplemental hearing will be needed before we reach that decision.
'