TMI-15-076, Submittal of TMI White Paper-TMI Bwst Cleanup Path Issue

Submittal of TMI White Paper-TMI Bwst Cleanup Path Issue

ML15177A098
Person / Time
Site:	Three Mile Island
Issue date:	06/22/2015
From:	Libra R Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TMI-15-076
Download: ML15177A098 (5)

Text

Exelon Generation,.

June 22, 2015 TMI-15-076 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Three Mile Island Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-50 NRC Docket No. 50-289

Subject:

Submittal of TMI White Paper-TMI BWST Cleanup Path Issue This letter transmits the attached enclosure titled "TMI BWST Cleanup Path Issue" that was written as a white paper and provided to the TMI NRC Resident Inspectors. The intent of the white paper was to explain our logic for concluding the BWST cleanup operation is part of the Three Mile Island, Unit 1 (TMI-1) licensing basis. This submittal is provided at the request of the NRC to place the white paper on the formal TMI-1 docket.

There are no regulatory commitments contained in this letter.

If you have any questions with this correspondence, please contact Mr. David Atherholt, TMI Regulatory Assurance Manager (717) 948-8364.

Respectfully, R. W. Libra Site Vice President, Three Mile Island Unit 1 Exelon Generation Co., LLC Enclosure cc: USNRC, Regional Administrator, Region I USNRC, Senior Resident Inspector, TMI Unit 1 DD~

TMI BWST Cleanup Path Issue Historical Summary:

TMI had recirculated and cleaned up the BWST since original licensing. IN2012-011 was issued titled "Seismic Considerations-Principally Involving Tanks." The INtalked about Shearon Harris2 recirculating a seismically qualified RWST (refueling water storage tank) through non-seismic fuel pool piping purification system piping causing the RWST to be made inoperable. TMI stopped the practice of recirculation on 10/03/12 to conduct a further review. A 50.59 screening 3 was written and the practice recommenced on 06/01/13. TMI was subsequently cited and given a traditional violation 4. The inspectors reviewed the 50.59 screening and the BWST licensing basis and determined that aligning the BWST to non-seismically qualified pipe is contrary to the licensing basis function as described in the FSAR 5.1.1-. The NRC concern with the BWST cleanup process at TMI is based on their conclusion that the process was in conflict with TMI licensing basis requirements for an earthquake.

Original Licensing Criteria for BWST:

The TMI design presented in the FSAR was approved by NRC via SER issued in July 1973. FSAR section 1.4.26 presents the AEC draft General Design Criterion 2 which set the design standard for external events including earthquakes. The standard addresses the severity of the hazard and the performance standard for reactor safety in such events.

Those systems and components of Reactor Buildingfacilities which are essential to the prevention of accidents, which could affect the public health and safety or to mitigation

'of their consequences shall be designed,fabricated,and erected to performance standards that will enable the facility to withstand, without loss of the capability to protect the public, the additionalforces that might be imposed by naturalphenomena such as earthquakes,tornados,flooding conditions, winds, ice, and other local site effects. The design bases so establishedshall reflect: (a) appropriateconsiderationof the most severe of these naturalphenomena that have been recordedfor the site and the surroundingarea, and (b) an appropriatemargin for withstandforces greaterthan those recorded to reflect uncertaintiesabout the historicaldata and their suitabilityas a basis for design.

The question about the design adequacy of the BWST cleanup process piping was initiated by review of IN2012-01. In that IN,a plant licensed to the General Design Criteria in 10CFR50 Appendix Awas cited for a procedure change which authorized cleanup of the RWST through non-seismic piping when the RWST was required to be operable lAW Tech Specs. The cleanup process through non-seismic piping and operator action to isolate leakage from BWST are the same as used at TMI.

1

TMI BWST Cleanup Path Issue The difference between the IN case and TMI is the licensing basis. 10CFR50 Appendix A GDC 2 (not TMI-1 licensing basis) sets a more conservative standard by requiring that all safety related SSC be protected from external events such that the safety function of the SSC can be achieved after an external event.

Criterion2-Design bases for protection against naturalphenomena. Structures, systems, and components importantto safety shall be designed to withstand the effects of naturalphenomena such as earthquakes,tornadoes, hurricanes,floods, tsunami, and seiches without loss of capability to perform theirsafety functions. The design basesfor these structures,systems, and components shall reflect: (1) Appropriate considerationof the most severe of the naturalphenomena that have been historicallyreportedfor the site and surroundingarea, with sufficient marginfor the limited accuracy, quantity, and periodof time in which the historicaldata have been accumulated, (2) appropriate combinationsof the effects of normal and accident conditions with the effects of the naturalphenomena and (3) the importanceof the safety functions to be performed.

In the case of a non-Appendix A plant (TMI-1 licensing basis), the requirements for evaluating the performance of a safety function also apply.

The TMI license was approved with a design which relied upon non-seismic piping for BWST cleanup. This is completely consistent with the AEC draft GDC 2. Operator action was credited to satisfy this requirement (see additional material provided below).

To understand how "without loss of the capability to protect the public" was interpreted, it is helpful to review the design capability approved for some of these external events. Several design considerations which are clearly described in the FSAR are as follows:

" The BWST could not be relied upon after a tornado or aircraft impact.

" The Diesel Generator building could not withstand an aircraft impact, but the design met this standard and was approved.

" The diesel fuel supply (FO-T-1) was flood protected however it was not designed for an 14 earthquake TMI Original FSAR specific material for BWST cleanup licensing basis The BWST is cleaned up and recirculated through BWST piping, spent fuel system piping and the waste disposal liquid piping. Each of the respective FSAR sections must be understood to obtain a complete understanding of the cleanup licensing basis.

TMI was licensed as a pre-GDC 2 design criteria plant with the BWST and spent fuel pools characterized as Class 1 systems. FSAR pages 5-2 through 5-47 2

TMI BWST Cleanup Path Issue The liquid waste disposal system (providing precoat filters and cation demineralizers for BWST cleanup) is described in the original FSAR as having been housed in Class I structures and characterized as providing operating service functions to the primary system and spent fuel pools. FSAR 22-39 These operating service functions are described on FSAR pages 11-3 and 11-49. They include clean-up of spent fuel water, processing spent fuel water for re-use or disposal, and processing primary coolant and refueling water for re-use and disposal. The operating service system flow diagrams are referenced in this section and provided in the FSAR. FSAR Figure 11-210 contains the precoat filters and cation demineralizers used in the cleanup process for the BWST and spent fuel pools.

Since portions of the spent fuel pool system are integral to cleanup and reuse for the spent fuel pool system and cleanup and reuse of BWST water as an operating service function, the FSAR section on the fuel pool is important. Section 9.4 on page 9-168 states cleanup of the spent fuel pool as being accomplished by diverting part of the flow through filters and/or demineralizers of the liquid waste disposal system. This section of the FSAR also states that the system function is to circulate refueling water through clean up equipment and references during storage in the BWST. FSAR page 9-178.

The FSAR then defines how this process is controlled. Under Section 9.4.58 Method of Operation, the spent fuel pool cooling functions are monitored and controlled from the main control room. All other functions of the spent fuel cooling system are accomplished by local manipulation and control of equipment.

TMI has used the operating service functions since original operation to cleanup the spent fuel pools and the BWST as described in the FSAR using the precoat filters and/or the cation demineralizers.

After original licensing as a pre-GDC plant, the seismic capability for pre-GDC 2 plants was questioned.

The USI A-46 process was established to. resolve the issue.

In the process of USI A-46 TMI considered the original FSAR application of the BWST recirculation process path and further considered the spent fuel pools (although not required by the USI A-46 process). Three Mile Island USI A-46 Report Seismic Verification Data Sheets Page 28 contains components for the BWST recirculation path"..

An NRC SER (Page 11)12 was provided to GPU Nuclear for the SQUG process. The staff verified that the licensee had considered its operator training programs and verified that training was sufficient to ensure those actions specified in the procedures could be accomplished by the operating crews. The procedure in use was the earthquake emergency procedure"3 that contained an action to isolate the BWST if on cleanup as a defense in depth action. These are the same valves used to locally align the cleanup path part of the original licensing basis. This is a prudent defense in depth action.

Safety Considerations: For a Safe Shutdown Earthquake (SSE), TMI-1 plant licensing basis does not include a concurrent seismic event and LOCA that would require the BWST contents. Only a small fraction of the contents are required for some RCS leakage and inventory shrinkage to hot shutdown (TM I-i SSEL Report for Resolution of USI A-46, dated 09/29/1994). The BWST cleanup recirculation 3

TMI BWST Cleanup Path Issue piping and filters were designed incorporating Operating Basis Earthquake (OBE) loads as were the majority of Liquid Radwaste Systems. Furthermore, this cleanup recirculation piping and filters were walked down and successfully evaluated as a seismic safe shutdown path, documented in the response to the NRC, and accepted per the associated SER.

Recently, several large piping sections of the BWST Cleanup path were successfully evaluated against SSE loads (2X OBE loads) for pipe stress to prove margin in the existing design. Existing procedural alarm response for earthquake uses a manual valve closure for the cleanup path, which was addressed in the original licensing, and remains a prudent defense-in-depth action.

As a result, it is clear the original license consideration of a local controlled cleanup process does not pose an unacceptable risk to nuclear safety.

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Conclusion:==

The original FSAR recognized the need to clean-up the BWST and the spent fuel pools and described the operating service functions necessary to maintain the water quality function through the precoat filters and/or the demineralizers. The piping for the cleanup path was housed in seismic Class 1 structures and the clean- up function was recognized to be accomplished through local manipulations and control of equipment. This cleanup path is recognized and acceptable within the original (and current) TMI licensing basis and does not pose an unacceptable risk to nuclear safety.

References cited:

1. IN 2012-01

2. NRC Inspection Report - Shearon Harris

3. 50.59 screening to procedure OP-TM-212-501

4. NRC Inspection Report-TMI

5. UFSAR Section 5.1.1

6. FSAR (Red Book) Section 1.4.2

7. FSAR (Red Book) pgs 5-2 thru 5-4

8. FSAR (Red Book) pgs 9-16 thru 9-17

9. FSAR (Red Book) pgs 11-3 thru 11-4

10. FSAR (Red Book) Figure 11-2

11. TMI USI A-46 Report Screening Verification Data Sheets

12. NRC SER TMI SQUG Process 12Aug98

13. Earthquake procedure revision 26

14. FSAR (Red Book) pgs 2-28a thru 2-29a 4