ML092880019
| ML092880019 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 10/19/2009 |
| From: | Raghavan L Watts Bar Special Projects Branch |
| To: | Callen J Univ of Wisconsin - Madison |
| Milano P, NRR/DORL , 415-1457 | |
| Shared Package | |
| ML092870762 | List: |
| References | |
| EDATS: OEDO-2009-0570, G20090540, OEDO-2009-0570, TAC ME2273 | |
| Download: ML092880019 (5) | |
Text
October 19, 2009 Professor James D. Callen University of Wisconsin 1500 Engineering Drive, 517ERB Madison, WI 53706-1609
Dear Professor Callen:
I am responding to the questions you raised during a public meeting on July 28, 2009, that was held at the Watts Bar Nuclear Plant (WBN) in Rhea County, Tennessee. The purpose of the U.S. Nuclear Regulatory Commissions (NRCs) Advisory Committee on Reactor Safeguards (ACRS) meeting of the Subcommittee (S/C) on Plant Operations and Fire Protection was to provide an opportunity for the S/C to receive an information briefing from the Tennessee Valley Authority (TVA) on the design, licensing, and construction activities associated with TVAs application for an operating license for WBN Unit 2. During the public comment period at the close of the ACRS S/C meeting, you asked questions about (a) the use of analog systems for the control of the reactor, (b) the delineation of responsibilities between TVA and Bechtel Corporation, and (c) the applicability of the NRC regulation for aircraft impact assessment (Aircraft Rule) to WBN Unit 2.
As you are aware, the mission of the NRC is to regulate commercial and institutional uses of nuclear materials, including nuclear power plants, and NRC has the overall responsibility to protect public health and safety. This mission is accomplished through the establishment of standards, regulations and requirements governing licensed activities, licensing of facilities, and inspections to ensure compliance with these requirements. In support of this mission, the ACRS reviews and advises the Commission with regard to the licensing and operation of production and utilization facilities and related safety issues, the adequacy of proposed reactor safety standards, technical and policy issues related to the licensing of evolutionary and passive plant designs, and other matters referred to it by the Commission.
Regarding the use of analog controls on the basic controls of the reactor, you questioned this approach considering that it may be getting difficult to acquire these components, especially for the duration of future licensed operation. Further, you asked if there was a plan to move from a basically analog control system to a digital control system that might be more available over some extended period of time.
In the United States, the type of instrumentation and control (I&C) system technology used for protection, controls, alarms, and display and monitoring of reactors has been mixed. Generally, new nuclear power plants are being designed with integrated digital I&C systems, and current operating reactors use the analog I&C systems. However, at a number of the operating reactors, the analog control systems are being replaced with more modern digital systems in applications such as steam generator feedwater control, recirculation control, demineralizer control, main turbine controls, and other nonsafety systems. Licensees determine the type of
I&C systems that is used, or will be used, based on business and other considerations. The NRC does not prescribe any specific I&C technology.
At WBN Unit 2, TVA plans to use analog I&C in the majority of safety systems and digital I&C in a few other safety and nonsafety systems, such as the inadequate core cooling monitor, incore flux probes, high-range radiation monitor, and loose parts monitoring systems. The NRC will review the I&C systems proposed for WBN Unit 2 to confirm that: (1) the system design includes the functions necessary to operate the plant safely under normal conditions and to maintain it in a safe condition under accident conditions, (2) these functions, along with the implementing systems and equipment, are properly classified to identify their importance to safety, and (3) quality standards for the design, fabrication, construction, and testing of I&C systems and equipment are commensurate with the importance of the safety functions performed. The necessary functions are those needed to monitor system variables over their anticipated operating ranges, to maintain these variables and systems within their prescribed operating ranges, to automatically initiate the operation of systems and components to assure that fuel design limits are not exceeded as a result of anticipated operational occurrences, and to sense accident conditions and initiate the operation of systems and components important to safety. Should TVA decide to later retrofit analog I&C systems with digital systems, the action may be subject to prior NRC review and approval.
You may visit our web site at http://www.nrc.gov/about-nrc/regulatory/research/digital.html for details about our activities under digital I&C design issues.
You inquired about delineation of responsibilities between TVA and its contactor, Bechtel Corporation, regarding necessary nuclear certifications. Based on the discussions during the meeting, you said that you found it was ambiguous and asked if TVA did not have sufficient nuclear capability and professional engineers who could provide necessary nuclear certifications.
Article NCA-3000, Responsibilities and Duties, of Section III of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) details the various parties involved in the construction of a nuclear power plant that have specific responsibilities for complying with the ASME Code requirements. In particular, TVA, as the owner of the plant, after being notified by the NRC that its application for a construction permit has been docketed, must obtain an Owners Certificate from ASME prior to beginning field installation. As part of its other responsibilities, the owner must designate the Designer, Constructor, and Fabricators for construction and must verify through a review of the required documentation that the Designer has fulfilled his responsibilities for construction and certify Design Specifications and review Design Reports.
It is common in nuclear construction for the owner to subcontract the design and construction to a major architect/engineering firm such as Bechtel Corporation. The ASME Code recognizes that services, both within and beyond the scope of the Code, may be subcontracted.
However, subcontracts for activities for which ASME Code certificates are required can only be made to authorized Certificate Holders. The activities necessary to provide compliance with responsibilities assigned to the owner may be performed on the owners behalf by a designee; however, the responsibility for compliance remains with the owner, TVA.
Lastly, you requested clarification about the Aircraft Rule and whether WBN Unit 2 is exempted from this Rule.
In response to events of September 11, 2001, the NRC undertook a series of regulatory actions to enhance the security of nuclear power plants. Some of these actions were directed at addressing the possible occurrence of an event leading to large fires or explosions occurring over a substantial part of a nuclear plant. In addition, the NRC conducted detailed, site-specific engineering studies of several nuclear power plants to assess potential vulnerabilities of deliberate attacks involving large, commercial aircraft.
On June 12, 2009, the NRC amended Title 10 of the Code of Federal Regulations (10 CFR) to add a new rule (10 CFR 50.150, Aircraft Impact Assessment) to require applicants for new power reactors to assess the effects of the impact of a large, commercial aircraft on the nuclear power plant. The applicant is required to use realistic analyses to identify and incorporate design features and functional capabilities to show, with reduced use of operator actions, that either the reactor core remains cooled or the containment remains intact, and either spent fuel cooling or spent fuel pool integrity is maintained.
As stated in the Aircraft Impact Assessment rule, it is applicable for applicants whose construction permits (CPs) were issued under Part 50 after July 13, 2009. However, the WBN Unit 2 CP was issued on January 23, 1973. Thus, the Aircraft Impact Assessment rule is not applicable to WBN Unit 2.
At the July 28, 2009, meeting, TVA used the word exempt to its description of applicability of the Aircraft Impact Assessment rule at WBN Unit 2. Exemption has a special meaning under NRCs regulations, and it refers to situations where the NRC could grant licensees relief from regulatory requirements under special circumstances. TVA has not sought an exemption from the Aircraft Impact Assessment rule; rather, the rule is not applicable to a plant for which construction permits were issued before July 13, 2009.
We appreciate your interest in the safety and security of commercial nuclear plants, including WBN Unit 2. I hope that you find this information helpful in addressing your questions.
Sincerely,
/RA JLamb for/
L. Raghavan, Chief Watts Bar Special Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
Incoming: ML092320387 Letter: ML092880019 Package: ML092870762 OFFICE NRR\\LPWB\\PM NRR\\LPWB\\LA NRR\\EICB\\BC NRR\\EQVB\\BC NRO\\DDIP\\BC NAME PMilano BClayton WKemper DThatcher WBurton DATE 10/19/09 10/19/09 10/14/09 10/14/09 10/14/09 OFFICE OGC NRR\\LPWB\\BC NAME DRoth JLamb for LRaghavan DATE 10/16/09 10/19/09
Letter to J. Callen from L. Raghavan dated October 19, 2009 Distribution: (G2000540/OEDO-2009-0570)
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