ML17017A437
| ML17017A437 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/17/2017 |
| From: | Jeremy Groom NRC/RGN-IV/DRP/RPB-A |
| To: | Halpin E Pacific Gas & Electric Co |
| Groom J | |
| References | |
| ML16363A429, ML17010A093 IR 2016010 | |
| Download: ML17017A437 (4) | |
See also: IR 05000275/2016010
Text
January 17, 2017
Mr. Edward D. Halpin
Senior Vice President
and Chief Nuclear Officer
Pacific Gas and Electric Company
Diablo Canyon Power Plant
P.O. Box 56, Mail Code 104/6
Avila Beach, CA 93424
SUBJECT:
NRC RESPONSE TO QUESTIONS INVOLVING DIABLO CANYON POWER
PLANT - FINAL SIGNIFICANCE DETERMINATION OF A WHITE FINDING;
NRC INSPECTION REPORT 05000275/2016010 AND 05000323/2016010
Dear Mr. Halpin:
This letter provides you the NRCs response to eight questions, submitted in writing by Pacific
Gas and Electric (PG&E) Company on January 4, 2017, (Agency wide Documents Access and
Management System (ADAMS) Accession No. ML17010A093). The question and answers are
related to the NRCs assumptions used in the final significance determination documented in
NRC inspection report 05000275/2016010 and 05000323/2016010, Diablo Canyon Power
Plant - Final Significance Determination of a White Finding, Notice of Violation and Follow-up
Assessment Letter, dated December 28, 2016 (ADAMS Accession No. ML16363A429). The
NRC provided verbal answers to these questions to Messrs. Hossein Hamzehee and Nathan
Barber of your staff, during a teleconference on January 9, 2017.
In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter and its
enclosure will be made available electronically for public inspection in the NRC Public
Document Room and in ADAMS, accessible from the NRC Web site at
http://www.nrc.gov/reading-rm/adams.html.
Sincerely,
/RA Ryan Alexander Acting for/
Jeremy R. Groom, Chief
Project Branch A
Division of Reactor Projects
Docket Nos. 50-275 and 50-323
License Nos. DPR-80 and DPR-82
Enclosure: NRC Response to PG&E Questions
UNITED STATES
NUCLEAR REGULATORY COMMISSION
REGION IV
1600 E. LAMAR BLVD.
ARLINGTON, TX 76011-4511
SUNSI Review
By: JRG/dll
Yes No
Non-Sensitive
Sensitive
Publicly Available
Non-Publicly Available
Keyword:
OFFICE
BC:DRP/A
DRS:SRA
D:DRS
D:DRP
BC:DRP/A
NAME
JGroom
RDeese
AVegel
TPruett
JGroom
SIGNATURE
/RA/
/RA/
/RA Jeff Clark
Acting for/
/RA/
/RA Ryan Alexander
Acting for/
DATE
1/11/2017
1/13/17
1/11/17
1/13/17
1/17/17
1
Enclosure
NRC RESPONSE TO PG&E QUESTIONS DATED JANUARY 4, 2017
The following eight questions were submitted in writing by PG&E on January 4, 2017, regarding
NRC inspection report 05000275/2016010 and 05000323/2016010, Diablo Canyon Power
Plant- Final Significance Determination of a White Finding, Notice of Violation and Follow-up
Assessment Letter, dated December 28, 2016 (ADAMS Accession No. ML16363A429).
The NRC provided the following verbal answers to these questions during a teleconference
with the licensee on January 9, 2017.
Question 1. Element #2 (Page A-1): The estimate of increase in core damage frequency
from large break LOCAs was 1.4E-7 per year. Is the 1.4E-7 value a delta-CDF or does it
represent the total contribution from large break loss-of-coolant accidents?
NRC Response to Question 1: The 1.4E-7 per year used for large break loss-of-coolant
accidents is a delta-CDF (core damage frequency) value.
Question 2. Element #5 (Page A-3): Following the termination of emergency core cooling
system flow which occurs at refueling water storage tank (RWST) Level=4%, did you
consider normal makeup to the reactor coolant system (RCS) from normal charging as
discussed within our response to request for information (RFI)-011?
NRC Response to Question 2: Yes. As discussed in the final significance determination,
Element 9, Page A-7, the NRC did consider normal makeup to the RCS from normal charging
when evaluating additional technical support center and emergency response organization
(TSC/ERO) directed recoveries.
Question 3. Element #7 (Page A-4): We note that the NRC has used emergency operating
procedure (EOP) E-1.3, Revision 15, in the response to Element #8. The response to RFI-
010 attached Revision 15 with its change documentation to illustrate when and why the
caution statement, discussed in the RFI, was added to the EOP. At DCPP, the current
revisions of EOP E-1.3 are Revision 31 (Unit 1) and Revision 22 (Unit 2), both effective
1/5/16. Did you use EOP E-1.3, Rev. 15 in your analysis for Element #7?
NRC Response to Question 3: Yes. However, the NRC reviewed both EOP E-1.3, Transfer to
Cold Leg Recirculation, Revision 15 and Revision 22 to inform our understanding of what
valves are manipulated prior to reaching the point at which operators enter emergency
contingency action procedure ECA 1.1, Loss of Emergency Coolant Recirculation. We also
compared this information with the most recent version of the Diablo Canyon Final Safety
Analysis Report to understand the sequence of valve manipulations performed in the first few
minutes of the transition to emergency core cooling system cold leg recirculation.
Question 4. Element #7 (Page A-4): What is the time duration used in your analysis to
perform local manual operation of 8982B?
NRC Response to Question 4: The NRC assumed 30 minutes for diagnosis, followed by
approximately 103 minutes of manual action to access and open valve SI-2-8982B through use
of the manual hand wheel.
2
Enclosure
Question 5. Element #8 (Page A-6): What EPRI study is referred to on page A-6?
NRC Response to Question 5: The Electric Power Research Institute (EPRI) study referenced
on page A-6 is EPRI TR-106563, Volume 1, Application Guide for Motor-Operated Valves in
Nuclear Power Plants, Revision 1. This report includes a summary of motor operated valve
incidents based on nuclear power plant experience documented in EPRI NP-6660D,
Application Guide for Motor-Operated Valves in Nuclear Power Plants, Appendix F.
Question 6. Element #8 (Page A-5): What is the time delay from RWST level at 33% to
initiate the electrical recovery?
NRC Response to Question 6: The NRC assumed the licensee would initiate the electrical
recovery option approximately 46 minutes after RWST level reached 33 percent. The NRC
assumed that the electrical recovery option would be completed approximately 209 minutes
after RWST level reached 33 percent.
Question 7. Element #9 (Pages A-6 and A-7): Please clarify whether the electrical and
mechanical recovery actions are performed in parallel or in series.
NRC Response to Question 7: The NRC assumed that the TSC/ERO could pursue both the
electrical and mechanical recovery actions in parallel but that because of the format of some
station procedures including those used to manually operate motor operated valves, certain
portions of the recovery actions were sequential.
Question 8. Element #9 (Page A-7): What actions are included in the effective failure
probability of 5.0E-1? Does this include actions to prolong the time to core damage or
actions to open 8982B?
NRC Response to Question 8: As discussed in the final significance determination, Element 9,
Page A-7, the actions included in the effective failure probability of 5.0E-1 include additional
TSC/ERO directed recoveries involving the electrical jumper method, additional electrical
contactor attempts, and/or additional mechanical operations.
As discussed in the final significance determination, Element 9, Page A-7, the NRC did account
for the added time to core damage through additional RCS/RWST makeup strategies when
evaluating the human error probability.