ML18012A724
| ML18012A724 | |
| Person / Time | |
|---|---|
| Issue date: | 01/12/2018 |
| From: | Jay Collins, Stephen Cumblidge, Ali Rezai NRC/NRR/DMLR/MPHB |
| To: | |
| Rezai A, NRR-DMLR 415-1328 | |
| Shared Package | |
| ML18002A510 | List: |
| References | |
| Download: ML18012A724 (9) | |
Text
Upper Head Inspections Stephen Cumblidge and Jay Collins NRC / Industry NDE Technical Information Exchange Meeting January 1618, 2018
Motivation In a licensee, which had replaced their head with a resistant head, claimed that significant boric acid deposits were all leakage from above, powerwashed the head without performing any supplemental examinations. Other discussions with other licensees have since followed.
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NRC Goals Maintain rigor on upperhead inspections Prevent situation where the NRC staff and a licensee have a lengthy debate the requirements for upper head inspections during an outage 3
Leaks Happen Boric acid on the upper head can come from two main sources
- Leakage from seals or weld leaks in the CRDM housings
- Leakage through the annulus form PWSCC of the nozzle
- Both Determining the source of the boric acid can be challenging Photographs from EPRI Report 1007842 4
Determining the Source of Boric Acid Chemical or isotopic analysis my be used, depending on the source of he leak EPRI provides guidelines in the publicallyavailable Visual Examination for Leakage of PWR Reactor Head Penetrations Revision 2 EPRI Report 1007842 If one washes the relevant conditions away without any Compressed air, in the range of 40-60 analysis, it is essentially psi (276-414 kPa), or a vacuum directed at deposits has been used to distinguish impossible to rule out the whether a deposit is loose buildup of possibility that some of the material simply resting against a leakage may have come from a penetration that is easily removed or is leak a tightly adhering deposit, originating from the annulus of a leaking penetration.
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VE Relevant Conditions Current rules require that areas with boric From N7294 acid or signs of corrosion be evaluated to determine the source of leakage If leakage cannot be ruled out, volumetric inspections of the nozzle or repair are required 6
Recent OE Palo Verde Relief Palo Verde Unit 1 leaked reactor coolant from a vent valve 14 nozzles had boric acid indications at the nozzle annuli Additionally, fibrous insulation particles were blown around by ventilation Palo Verde initially left the areas with suspected fibrous insulation out of the relief and did not initially perform any additional evaluations 7
Palo Verde Relief cont.
After discussions with the NRC staff, the licensee performed sufficient evaluations (air blasting and additional photographs) of the additional nozzles to satisfy the headquarters and regional staff Relief was granted to perform a VE examination on the 14 original nozzles during the next refueling outage 8
Future To help get the NRC staff and licensees in agreement and understand what is expected, a draft RIS Clarification of the Requirements for Reactor Pressure Vessel Upper Head Bare Metal Visual Examinations is currently going through concurrence The RIS will be out for public comments in early 2018 and is projected to be in effect by the Fall of 2018 9