ML021400606
| ML021400606 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 05/24/2002 |
| From: | Zwolinski J NRC/NRR/DLPM |
| To: | Bastin C - No Known Affiliation |
| Sands, S, NRR/DLPM/PD3-2, 415-3154 | |
| References | |
| TAC MB4984, Y020020129 | |
| Download: ML021400606 (3) | |
Text
May 24, 2002 Mr. Clinton Bastin 987 Viscount Court Avondale Estates, Georgia 30002
Dear Mr. Bastin:
Thank you for your letter to Chairman Meserve dated April 15, 2002, and sharing your experience and the Department of Energy safety record achieved by DuPont related to the Savannah River plant.
In your letter you informed the Nuclear Regulatory Commission (NRC) about DuPonts experience regarding the use of minimum thickness holes to monitor corrosion and erosion on the inside of pipes or vessels at the Savannah River Plant. The use of minimum thickness holes is based on the principle that the pipe or vessel will leak first before it breaks when the metal is thinned because of corrosion and erosion from the inside, therefore, an observable leak will develop through the hole and the plant can be shut down for repairs. As I am sure you recognize, the corrosion at Davis-Besse did not start from the inside of the vessel head and that the inside of the vessel head was clad with stainless steel which is not vulnerable to boric acid corrosion under plant operating conditions. Given this, the use of "minimum thickness holes" would not have been effective in detecting the degradation.
Nuclear power plants in United States are designed and erected in accordance with the requirements of American Society for Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section III, Rules for Construction of Nuclear Power Plant Components. The ASME Code does not employ minimum thickness holes to monitor corrosion and erosion of piping and vessels. Instead, the Code requires that after nuclear plant components are manufactured, the components must be examined for defects using various nondestructive examination methods depending on the components safety classification, Class 1 being the highest classification while Class III being the lowest. Class 1 safety-related piping and components are ultrasonically examined in accordance with the pre-service requirements of the ASME Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, before being placed into service. Once the nuclear power components are placed into service, they are inspected and examined in accordance with the requirements of ASME Code, using various nondestructive examination methods so that any new defects are properly identified and corrected.
Nuclear power plants also employ different leak detection strategies. Fluids leaking from plant components are collected in sumps and the fluid inventory is closely monitored in accordance with the facilitys applicable technical specifications (TS). If the plant instrumentation indicates a higher fluid inventory than the one allowed by the plants TS, plant operators are required to take appropriate action, which may include the initiation of plant shutdown.
Mr. Bastin The NRC also issues generic communications such as Information Notices and Bulletins to alert nuclear power plants of potential problems that may apply to their facilities. In doing so, the industry is provided with advanced information so that potential problems are promptly identified and corrected.
In conclusion, I would like to assure you that NRC is closely monitoring the investigation of the Davis-Besse issue and the rules and regulations that provide for safe operation of nuclear power plants are followed, and thus, public health and safety is ensured.
Sincerely,
/RA/
John A. Zwolinski, Director Division of Licensing Project Management Office of Nuclear Reactor Regulation
Response: ML021400606 Incoming: ML021210443 Package: ML021400624 OFFICE PM:LPD3-2 LA:LPD3-2 BC:EMCB SC:LPD3-2 PD:LPD3 D:DLPM NAME SSands CRosenberg for THarris WBateman AMendiola SBajwa JZwolinski DATE 05/22/02 05/22/02 05/23/02 05/23/02 05/23/02 05/24/02