Neighbors Growing Together | Oct 27, 2021

Cracks Found in SCE&G Nuclear Reactor in Fairfield County, SC

By Thomas Clements | Nov 15, 2012
Photo by: Tom Clements of the Alliance for Nuclear Accountability SCE&G sign marks the entrance to the construction site for two new AP1000 units, adjacent to the existing aging unit which was licensed by the Nuclear Regulatory Commission to operate in 1982.  V.C. Summer unit 1 is a pressurized water reactor (PWR) designed by Westinghouse.  All the spent fuel created since the reactor began operation, which holds a large amount of radioactive material, is stored in the spent fuel pool.  SCE&G plans to construct a dry cask storage facility in the coming years but in order to reduce risks of a spent fuel pool accident that facility should begin use immediately and spent fuel should be removed from the pool and placed in the casks, according to the Alliance for Nuclear Accountability.

Columbia, SC – The SCANA Corporation has revealed that its V.C. Summer nuclear reactor is suffering from cracks (“flaws”) in welds on the top of the reactor vessel.  Such cracks, if of significant depth and if uncorrected, could lead to a serious reactor accident involving loss of reactor coolant water.

On a call with investors on November 6, Steve Byrne , Chief Operating Officer, stated that a robotic inspection of the reactor vessel head (RVH) had identified four of 66 “penetrations” into the reactor vessel in need of repair.  The Vessel Head Penetrations (VHP) are mostly associated with control rod drive mechanism which penetrate into the reactor to control the nuclear reaction.

The South Carolina Electric and Gas (SCE&G) reactor provides electricity to the SCE&G service area, which includes Aiken, South Carolina.

Control rods are essential to the safe operation of the reactor and, in a worst case scenario, according to the Nuclear Regulatory Commission (NRC) , an “undetected circumferential cracking of VHP nozzles and degradation of the RPV head can pose a safety risk if permitted to progress to the point that the integrity of the reactor coolant pressure boundary is in question and the risk of a LOCA or probability of a VHP nozzle ejection increases.”

“The cracks found in the VC Summer reactor pose a clear safety risk and must be immediately addressed,” said Tom Clements of the Alliance for Nuclear Accountability. “While SCE&G will want to rush to get the reactor back on line and do a quick repair, the NRC must be deliberate in reviewing the causes of the cracking and how it is addressed.  Operation of the reactor with a vessel head subject to cracking poses a safety hazard that both SCE&G and the NRC are responsible for.”

In the investor’s call of November 6, SCANA’s Byrne went on to say that the Nuclear Regulatory Commission had been notified about the problem and that “a strategy to repair the welds” had been developed and that a repair plan would now be executed during the current refueling outage.

The reactor went down for refueling on October 12 and it appears that V.C. Summer and Westinghouse personnel had planned for an inspection which may have detected such cracking.   The “repairs” proposed by Westinghouse, the reactor vendor, are to isolate the cracks into the subsurface of the head, thus reducing their exposure to primary water stress corrosion cracking (PWSCC).  The proposed  “repairs,” which must be reviewed and approved by the NRC,  evidently have only been carried out at one other reactor – Byron in Illinois.

It is believed that investors were alerted to the problem as the reactor could be out of operation for longer than anticipated, which costs money, and to inform them that a costly new vessel head could be required.  A new head for the South Texas reactor in 2010 was reported to cost $34.6 million (http://www.matagordaadvocate.com/news/2010/feb/18/replacement-reactor-vessel-head-arrives-site/)

Given that the reactor received an operating license from the NRC in 1982, the reactor, a Westinghouse “pressurized water reactor” (PWR), is aging and it is very likely that more such stress and aged-related cracks could eventually be discovered.  SCANA claims none of the damaged welds are leaking from inside the reactor vessel, which holds the highly radioactive nuclear fuel, but proof of this claim and information on the depth, severity and type of cracking must be released publicly, according to the Alliance for Nuclear Accountability.

While SCANA has stated that the “focus is on completing the repair safely during the outage before returning the reactor to service,” it is unclear if the novel repairs can be quickly and adequately done or if greater problems lurk.  “Replacement of the entire vessel head, an expensive and lengthy process, will likely be necessitated now or in the future,” according to Clements.

NRC requirements for “control rod drive mechanisms (CRDMs)” inspection was determined to be essential after discovery in 2002 of severe corrosion in the reactor vessel at the Davis-Besse reactor in Ohio.  Leakage of boron via several through-wall cracks had resulted in corrosion of the reactor vessel down to a thickness of only 3/8 inch.  If the crack had gone undetected a Loss-of-Coolant Accident (LOCA) could have resulted, with severe consequences.  As a result of the Davis-Besse situation, the NRC instigated tighter regulation son nuclear utilities for inspection of reactor penetrations.

“As it poses safety risks to the environment and public, we believe that SCE&G must not dally concerning this serious safety issue and immediately order a new reactor vessel head to replace the flawed head,” said Clements.

The Vogtle reactors south of Augusta, Georgia, operated by Georgia Power, obtained operating licenses in1987 and 1989 and thus the reactors are also subject to the stress of aging.  The vessels should be thoroughly inspected for cracking, according to Clements.

Notes:

SCE&G letter to the NRC, on vessel head issue, October 22, 2012:

http://www.ananuclear.org/Portals/0/vesssel%20head%20SCE&G%20letter%20to%20NRC%2010.22.2012.pdf

 

SCE&G letter to the NRC, with Westinghouse repair document attached, October 30, 2012:

http://www.ananuclear.org/Portals/0/vessel%20head%20SCE&G%20letter%20to%20NRC%2010.30.2012.pdf

 

Nuclear Regulatory Commission “event report” of October 24, 2012 on “DEGRADED CONDITION DUE TO REACTOR HEAD VESSEL PENETRATION INDICATIONS”

http://www.nrc.gov/reading-rm/doc-collections/event-status/event/2012/20121024en.html

 

SCANA Corporation (SCG) Q3 2012 Earnings Conference Call November 6, 2012 11:00 AM ET, in which the vessel head problems was discussed, page 5/6:

http://seekingalpha.com/article/984281-scana-s-management-discusses-q3-2012-results-earnings-call-transcript?page=5

NRC site on RPV Upper Head Issues

 

http://www.nrc.gov/reactors/operating/ops-experience/pressure-boundary-integrity/upper-head-issues/upper-head-issues.html

 

SCE&G communication to NRC: “VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) DOCKET NO. 50/395 OPERATING LICENSE NO. NPF-12 RESPONSE TO NRC BULLETIN 2002-02 REACTOR PRESSURE VESSEL HEAD AND VESSEL HEAD PENETRATION NOZZLE INSPECTION” PROGRAMS

http://pbadupws.nrc.gov/docs/ML0336/ML033630741.pd

December 23, 2003

In 2002 after the video inspection, QC inspected the top surface of the reactor vessel head. This inspection was performed from the crane looking down on the vessel head assembly. No signs of boric acid residue were found on the top surface of the head insulation or at the top of the CRDM and conoseal housings. Since all on the samples of boric acid residue was dated to greater than two years, it is likely that the leakage occurred sometime earlier in plant life.

The reactor vessel was adequately cleaned to the extent practical considering the high dose rates in the general area to assure that there was no adverse impact from the Boric Acid residue. The areas cleaned were videoed to show the as left conditions. The cleaning video was reviewed by VCSNS engineering. Great consideration was given to the dose rates in the vicinity of the head. In the cleaning plan, CRDMs 27, 47, 50, 51, 55 and 59 were treated with the highest concern because they had the most dried residue and/or were in areas where the dried film went onto the vessel head.

Also, as a result of the cleaning efforts, CRDMs 44, 62, 63, 42, 46, and 58 were cleaned. All of the additional CRDMs that were cleaned are in the vicinity of the CRDMs that were treated with the highest concern. Cleaning was terminated because of high dose concerns. Attachment II contains comments about the as left conditions of the penetrations after the cleaning.

The vessel head is SA 533, Grade B, Class 1 alloy steel and the CRDM housings are Inconel. The primary concern for the leakage onto the vessel head material is boric acid induced corrosion of the metals from the boric acid in the primary coolant that leaked from the RCS. This type of process fluid has the capability, under the right conditions, to be highly corrosive to carbon and certain low alloy steels. The corrosion mechanism of greatest concern due to leakage of borated water is uniform corrosion, or wastage.

 

NRC on “Davis-Besse Reactor Vessel Head Degradation

http://www.nrc.gov/reading-rm/doc-collections/nuregs/brochures/br0353/

Background

“The reactor pressure vessel (RPV) heads of pressurized water reactors (PWRs) have penetrations for control rod drive mechanisms (CRDMs) and instrumentation systems made from nickel-based alloys (e.g., Alloy 600) and related weld metals (Figure 1). Primary coolant and the operating conditions of PWR plants can cause cracking of these nickel-based alloys and weldments through a process called primary water stress corrosion cracking (PWSCC). In response to the detection of PWSCC at several plants, the NRC issued NRC Bulletin 2001-01, “Circumferential Cracking of Reactor Pressure Vessel Head Penetration Nozzles,” which requested information related to licensees’ programs for inspection of vessel head penetration (VHP) nozzles.”

“On February 16, 2002, in response to Bulletin 2001-01, the Davis-Besse Nuclear Power Station (DBNPS), located in Oak Harbor, Ohio, began a refueling outage with the intent to perform work that included remotely inspecting the VHP nozzles from underneath the head focusing on the CRDMs. The licensee found that three CRDM nozzles had indications of through-wall axial cracking. Specifically, the licensee found these indications in CRDM nozzles 1, 2, and 3, which are located near the top of the RPV head.”

 

Nuclear Energy Institute briefing on “nozzle cracking and boric acid leakage”:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&ved=0CD4QFjAB&url=http%3A%2F%2Fwww.nei.org%2Ffilefolder%2Fstatus_report_corrosion.pdf&ei=t6yiUIS0Ee3G0AHnnoEI&usg=AFQjCNH2z4vGeqqZ4PiqX76DqSvBHP1kHg

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