ML19290D252
| ML19290D252 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon, Crane  |
| Issue date: | 12/05/1979 |
| From: | Kuo P Office of Nuclear Reactor Regulation |
| To: | Shao L Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8002200972 | |
| Download: ML19290D252 (5) | |
Text
.
f(pn nec,fo UNITED STATES u
y e,(/' gg NUCLEAR REGULATORY COMMISSION j
wAsHiNoTON, D. C. 20555
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DEC 5 1973
/
. MEMORANDUM FOR:
L. Shao, Acting Assistant Director for Engineering Division of Systems Safety FROM:
P. T. Kuo, Group tcader Seismic Review Group Division of Operating Reactors SRG RESPONSE TO ACRS QUESTIONS REGARDING TMI-ACCIDENT
SUBJECT:
IMPLICATIONS-SEISMIC CONSIDER'\\TIONS Enclosed is tbc collective response of the SRG staff to the questions raised by the ACRS on October 3, 1979. Our responses are to the question'; raised about Diablo Canyon. The questions are broad in scope and we have tried to respond to them in as great a detail as postible based on our interpretation.
'? "/. l{c. a c-P. T. Ku'o,.Grdup Leader Seismic Review Group
, Division of Operating Reactors cc:
D. Eise+ut SRG Members
(
8002 200 77p a
Question 1.
What, if anything, does the NRC staff think may warrant a special look because of seismic considerations?
Response
The intent of this question is not clear.
It has to be clarified before a specific answer can be provided. Generally speakir 3, emphasis on seismic adequacy should be given to those systems and components which are essential to plant sMe shutdown such as primary pressure boundary and ECCS.
Question 2.
Has the staff and applicant looked at procedures for a severe earthquage? How is a decision reached regarding its adquacy?
Response
The SRG staff is formulating post earthquake inspection procedures which include an initial " Quick-look" and a follow-up detailed inspection. The task action plan includes identifying structures and systems essential to maintain the pit.nt in a safe shutdown condition and developing acceptance criteria based on design data for the plant and system function. Adequacy of post-earthquake inspection procedure to be submitted by any applicant will be determined by staff evaluation based on the acceptance criteria being developed.
Question 3.
What anomalies in system behavior during an earthquake should operators be trained to handle? An example would be the failure of non-seismically qualified equipment.
Response
By definition, the failure of non-seismically qualified equipment should not impair the plant operation. Should there be any such equipment that is essential to safe shutdown of the plant, it would have to be re-classified.
Question 4.
What are the assumptions concerning failure of non-seismic Category I piping? To what extent can the failure of such piping be tolerated?
Is the Design based on a single criterion?
Response
Section C.2 of R.fi.l.29 states that "those portions of structures, systems, or components whose continued function is not required,
_2 but whose failure could reduce the functioning of any plant feature included in items 1.a through 1.q above (Ref. 10CFR 100 Appendix A) to an unacceptable safety level or could results in incapacitating injury to occupants of the control room should be designed and constructured so that the SSE would not cause such failure". The assumptions,then,concerning failure of non-seismic Category I piping is that failure can be tolerated provided that plant safety features are not impaired. Design is based on single failure criteria.
Question 5.
Has the applicant examined the reliability of connections to the refueling water storage tank for the earthquake situation? What criteria do the connections meet?
Response
The applicant is currently looking at these connections. The connections are seismic Category I.
Question 6.
What significance is attached (if any) to recent cases of pipe cracking in stagnant borated water line as it applies to earthquake?
Response
The cracks are significant if the crack length is close to the critical crack length.
It could then become a significant problem under earthquake conditions.
Question 7.
What consideration does the staff believe appropriate for system degradation, such as the recent feedwater nozzle cracking experience, as it applies to inservice inspection programs for plants in areas of high seismic activity?
Response
This question is not in the scope of the Seismic Review Group.
4 Question 8.
What are the seismic cle.sses of:
a.
PORV b.
Block valve Equipment related to the operability of these devices.
c.
Response
Those valves and equipment important to meeting the safety requirements of 10CFR 100 Appendix A namely:
1.
Maintaining the reactor coolant pressure boundary, 2.
Maintaining the capability to shutdown the reactor and maintain safe shutdown condition and, 3.
To prevent or mitigate the consequences of accidents, which would reuslt in significant offsite exposure, are classified as Category 1, others are non-seismic Category I.
Question 9.
What are the specific reconmendations for the Auxiliary Feedwater system at Diablo Canyon?
Response
For the answer to this question, refer to the "Less:ns Learned" task force.
Question 10. Are there seismic effects in the control room which require attention? Has special consideration been given to structures, equipment, and instrumentation in the control room for an earthquake situation? For example: Has the ceiling been analyzed? Will lighting be adequate? Will lighting fixtures remain in place?
Response
There are four lighting systems in the control rocm of the Diablo Canyon plant, i.e., a primary systen and three back-up systems.
Lighting will be adequate provided the electric current failure of the primary system activates the back up system.
Question 11. What is the status of control room instrumentation displays, how rapid is the plant process computer (delay between printing and real time), what effect would an earthquake have?
Response
Control room instrumentation displays are seismically qualified, but the computer printout equipment may not be.
Question 12. How comprehensive are tests for electrical transients during an earthquake and effect on equipment? Reliability of both off-site and on-site power.
Response
This question is not within the scope of the Seismic Review Group.
Question 13. Staff conclusion regarding technical support capabilities for Diablo Canyon.
Response
This questions it not within the scope of the Seismic Review Group.