NRC Advisory Committee on Reactor Safeguards (ACRS)
Entergy Nuclear VY license Renewal
Status of Review: ENVY still hasn’t resolved issue of metal fatigue.
NRC staff: NRC has worked over last few months to clarify problem. ENVY used software with unconventional methodology to predict metal fatigue. Used simplified calculations, combined six components into one component. It’s a mathematical manipulation but is not an industry standard. It was used before, but it was unknown to the NRC staff.
Method used has never been published in any professional literature.
NRC Conclusion: methodology MAY be used in some situations, but only if component not subject to sheer stress.
NRC asked ENVY to look at six locations with conventional mathematical modeling. Nozzle and pipe to pipe applications.
“WE got the last submission yesterday, so we haven’t evaluated it yet. But we think the applicant is now on the right path.”
Entergy: We made all kinds of improvements to get the 20% power boost.
Steam Dryer– cracks have been a problem, but I won’t say the word CRACK until later. No fatigue cracking found, only intergranular cracking.
NRC- what do you do when you find cracks?
Entergy- we don’t repair them, we just enter them into our records and look at them again in 18 months.
NRC-No samples taken to determine what kind of cracking it is? Only visual inspection?
ENVY- that’s right.
Corrosion
Entergy- We did 63 inspections, and found no additional corrosion due to power boost.
NRC- Are you still monitoring the steam line?
Entergy- No
NRC You’re only monitoring the water levels?
Entergy- Yes.
NRC- does the noble metals coating cover the stream dryer?
Entergy- probably not. We’ll let you know.
Underground tanks for emergency diesel generators:
Entergy-
I’m not aware that we’ve seen any significant corrosion.
Classic non-denial denial!
Cooling Towers
ENVY- collapse was a significant event for us, that did not meet our expectations.
NRC- explain why
ENVY- Inspection was insufficient. We didn’t predict it, so we didn’t look for it. The safety related cell has a different design.
Environmentally assisted fatigue–
gotta love it!
ENVY- Took our history and mixed it with history from younger, more robust reactor designs to show we’ll be good for another 20 years.
NRC-
Is this a reality?
ENVY consultant- It’s very conservative, used extensively over the life of the industry.
NRC-
I won’t go there! (laughter)
Corrosion and stress, cont.
ENVY- The nozzles we’ve done calculations for all look great, even though the calculations don’t match up.
NRC- Did you expect the calculations to show different results?
ENVY- We’re so conservative, we expected the confirmatory calculations to be even better than the first analysis.
NRC staff- We’ll be looking into that further for the March meeting.
Dry Well and torus
ENVY- we haven’t seen any of the problems that other similar designs have found.
Sand cushion- corrosion of dry well shell has been seen elsewhere. ENVY is different-no insulating foam, it was a construction material that was removed. We’ve seen dust blowing that confirms that air is flowing, keeping air cushion dry. The sand drains are inspected daily to see if there’s any moisture.
Unasked question: Is there moisture found?
1999- found the moisture barrier degraded. Replaced (repainted?)
NRC- you have no measurements of the shell, because you didn’t think you had to check it?
ENVY-yes
NRC- you didn’t remove the sand to examine the metal?
ENVY-no
1998- de-sludged the torus and recoated it. No generalised corrosion, only localized. Blistering and paint failure.
NRC-why?
ENVY- poorly applied paint the last time.
NRC- not because of oxidation from underneath?
ENVY- Oh, no.
Emergency Back-up Power from the Vernon Dam
ENVY- If the dam generator is out, it takes about 30 minutes to restart it. Someone has to come to restart it. But we can go 2 hours before we get in trouble.
NRC- The dam generates 32 mW. How do you know it wouldn’t overload your incoming power system?
ENVY-Dam operator would only restart one unit at a time.
Safety Evaluation Report
NRC- 2 week on site inspection
19 inspector weeks for aging management systems
We were skeptical of the glowing reports we were getting
re dry wall corrosion. But it’s in good shape.
Some corrosion monitoring was not being done, as ENVY didn’t think it applied to them.
NRC- ENVY re-did the analysis they had submitted in December, this time using commonly accepted practices. There was no change in the assumptions for water chemistry.
Now we’re happy with the philosophy of their analysis, although we’ve haven’t had time to check the calculations, because we only got them yesterday.
Sarah Hoffman VT DPS- buttering up the staff and ACRS, asks that there be no rush to judgement.
We want to make sure all the tires are kicked properly.
Joe Hoppenfeld (?) NEC consultant- ENVY assumptions need to be examined:
1. heat transfer co-efficients used are not applicable
2. used 10 year old data, not current
3. no evidence that the past history of transients will continue going forward
4. design geometry is not the same as installed geometry
5. corrosion is not a linear process.
(and more I didn’t get...)
ACRS-Is staff aware of new data?
NRC-yes. License renewal data requirements were developed quite a while back. It was decided it wouldn’t be fair to keep updating them.