Crud and Core Operating Limits Report

Crud and Additional Cost of Proposed Rulemaking 10 CFR 50.46c,

In its regulatory analysis, Regulatory Analysis for Proposed Rulemaking 10 CFR 50.46c,  (ML12283A188), the NRC asserts, “Because licensees are required to account for various thermal parameters under the current regulation, the NRC’s position is that the proposed requirement to evaluate crud is a clarification of the current requirement. As such, there would be no additional cost incurred as a result of the rule.” The NRC has thus chosen to remain uninvolved in the matter of the cost of reporting the impact of crud on emergency core cooling performance. 

Licensees have not been evaluating the thermal impact that crud would have in a LOCA. The NRC should issue an order REGARDING INFORMATION RELEVANT TO REGULATORY ACTIVITIES requiring licensees to evaluate how crud would impact a LOCA.  The NRC should also require that the impact of crud be included in the reporting of core operating limits: “[Core] operating limits shall be established and documented in the [CORE] OPERATING LIMITS REPORT before each reload cycle or any remaining part of a reload cycle.”

There is a substantial reservoir of facts that are relevant in addressing the impact of crud on the cost of reporting emergency core cooling performance.  Briefly discussed below are five of many sources; U. S. Patents, Vendor Advertising Brochures, Nuclear Power Plant Licensee evaluations under 10 CFR 50.59, the Consortium for Advanced Simulation of Light Water Reactors  (CASL), and EPRI.
 

There are at least six U. S. Patents in the arena of ultrasonic fuel cleaning that are pertinent to Proposed Rulemaking 10 CFR 50.46c: “Emergency Core Cooling System Performance during Loss-of-Coolant Accidents”.  The patents are pertinent to 50.46c because they include descriptions of crud that are otherwise not readily accessible by the public.

          U. S. Patents, Ultrasonic Fuel Cleaning     

Number	Inventor	Filed	Issued	Owner
5,467,791	Kato	Feb-94	Nov-95	Toshiba
6,396,892	Frattini	Apr-00	May-02	EPRI
7,542,539	Frattini	Dec-01	Jun-09	EPRI
7,134,441	Gross	Jul-03	Nov-06	Dominion
8,165,261	Hussey	Jan-09	Apr-12	EPRI
8,372,206	Gross	Jan-09	Feb-13	Dominion

Although other patents are likely pending, the most recent patent is Dominion Engineering, Inc., 8,372,206 that issued during February 2013.  Dominion therein references deficiencies in an EPRI ultrasonic crud removal process as follows:
“A number of ultrasonic cleaning systems have been developed for cleaning irradiated nuclear fuel assemblies including systems utilizing radial omni-directional ultrasonic cleaning technology as described, for example, in U.S. Pat. No. 6,396,892, the contents of which are incorporated herein by reference, in their entirety. FIG. 1 illustrates representative before and after photographs of fuel rods 100 in a fuel bundle cleaned using conventional radial omni-directional ultrasonic cleaning technology. Although, as reflected in FIG. 1, there is clear visual evidence of deposits being removed from the fuel assemblies, the cleaning is neither uniform nor complete, particularly with respect to the peripheral rods.”

 Dominion further references deficiencies of the EPRI omni-directional process as follows: “The inventors have determined that the tenacious layer currently associated with PWR fuel deposits has a threshold ultrasonic power density of approximately 200 watts/gallon (52.8 watts/liter) (as calculated using the methodology outlined below in Table 1). The invention consists of an ultrasonic cleaning device configured to achieve an ultrasonic power density on the order of 200 watts/gallon (52.8 watts/liter) or more. The invention utilizes arrays of planar transducers to achieve these high power densities rather than the conventional radial omni-directional transducers currently used for ultrasonic fuel cleaning.”

In its service bulletin of November 2012, NS-FS-0085, Westinghouse advertises that, “The High Efficiency Ultrasonic Fuel Cleaning (HEUFC) system, developed by Dominion Engineering, Inc., departs from the original ultrasonic fuel cleaner design to provide improvements in both cleaning effectiveness and efficiency. HEUFC has been used successfully at multiple plants.”

Ultrasonic fuel cleaning systems have been accepted for use at nuclear power plants under 10 CFR 50.59.  Those analyses are not publicly released; however, they should include the impact of crud on emergency core cooling.

The Consortium for Advanced Simulation of Light Water Reactors (CASL), is acknowledging the need to include crud in its quest for accurate simulations.  CASL has access to facts about crud including proprietary data from operating nuclear power plants. 

EPRI has a substantial inventory of facts about crud including proprietary data from operating nuclear power plants.