ML16215A129

Attachment Response to NRC Request for Additional Information Regarding TSTF-553, Revision 0, Add Action for Two Inoperable Creatcs Trains.

ML16215A129
Person / Time
Site:	Technical Specifications Task Force
Issue date:	08/02/2016
From:	Honcharik M C Licensing Processes Branch (DPR)
To:
Honcharik M C
References
TSTF-553
Download: ML16215A129 (7)

Text

By letter dated October 31, 2015 (Agencywid e Documents Access and Management System (ADAMS) Accession No. ML15304A002), the Technical Specifications Task Force (TSTF) submitted to the U.S. Nuclear Regulatory Commission (NRC) for review Traveler TSTF-553, Revision 0, "Add Action for Two Inoperable CREATCS [Control Room Emergency Air Temperature Control System] Trains." TSTF-553 proposes to revise the current Technical Specification (TS) 3.7.11, to modify the TS Actions for two inoperable CREATCS trains.

The revised Action provides 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore a CREATCS train to operable status , provided the control room ar ea temperature is maintained below a plant-specific limit. TSTF-553 is applicable to all Babco ck & Wilcox and Westinghouse plants (NUREG-1430 and NUREG-1431).

Question #1 is from the Probabilistic Risk A ssessment Operations and Human Factors Branch (APHB). Questions #2 through #5 are from the Containment and Ventilation Branch (SCVB).

Appendix A, "General Design Criteria for Nuclear Power Plants," to Title 10 of the Code of Federal Regulations (10 CFR), Part 50, "Domestic Licensing of Production and Utilization Facilities," Criterion 19 -

Control room, states, in part: "A c ontrol room shall be provided from which actions can be taken to operate the nuclear power unit safely under normal conditions and to maintain it in a safe shutdown condition und er accident conditions, including loss-of-coolant accidents." NUREG-0700, "Human-System Interface Design R eview Guidelines," Revision 2, Section 12, "Workplace Design," Subsection 12.1.2.1, "Temperature and Humidity," Guideline 12.1.2.1-1, "Comfort Zone," states: "The climate control system should maintain te mperatures of 68-75°F in winter and 73-79°F in summer and relative humi dity levels between 30% and 60%." Further, the additional information accompanying this guid eline, states, in part: "The temperature ranges given are based on the ASHRAE [Ameri can Society of Heating, Refrigerating and Air-Conditioning Engineers] 55-1992." While the above guidance addresses the temperature comfort zone in the control room, it does consider maximum allowable temperatures and associated stay times (action times), to ensure control room habitability. Related guidance fo r heat stress exposure is found in NUREG-0700, Revision 2, Section 12, Subsection 12.2.5.1, "Heat," Guideline 12.2.5.1-1, "Heat Stress," which states: "The level of physical activity and required pr otective clothing, as well as temperature and humidity, should be considered when assess ing the danger of heat exposure. Further, the additional information accompanying this guidel ine, states: "Important considerations are the amount of metabolic heat be ing generated by the worker and the restriction of evaporative heat loss associated with protecti ve clothing. Workers' abilities to withstand heat wi ll also differ based on their physical conditioning and degree of acclimatization." While this guidance is provided for Local Control Stations and not Cont rol Rooms, it addresses the effects of heat stress for workers with low metabolism (which is c haracterized as light work, such as actively monitoring spatially distributed equipment, walking, retrieving procedures or manuals, etc.) and work clothes. Table 12.7, "Stay times for different WBGTs [Wet-bulb globe temperatures]," illustrates that, for example, the stay time for WBGT of 93°F for an individual in work clothes with low metabolism is limited to 3 to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, whereas the stay time for WBGT of 97°F for the same individual would be limited to 2 to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

With both CREATCS trains bei ng inoperable, the effects of he at stress due to the rising temperature, under some circumstances, may impe de the operators' ability to take actions required to safely operate the nuclear power unit.

TSTF-553, Revision 0, Section 2.4, "Des cription of the Proposed Change," states, in part: "The proposed Required Actions require verification that control r oom temperature is less than a plant-specific limit every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and restoration of one CREATCS train to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />." Further, Section 3, "Technica l Evaluation," states, in part: "The four-hour monitoring frequency of control room area te mperature is adequate given the indications available in the control room, the time required for a significant increase in control room air temperature, and NRC acceptance of this interval in similar Technical Specifications for other plant designs." Provide additional information to clarify why the proposed temper ature monitoring frequency is set at 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, and does not vary with the plant-specific maximum temperature limit. In the response, identify what industry standard(s) or guidance (such as, for example, EPRI TR-109445, "Heat Stress Management Program for Power Plants"), or other data were used in determining the acceptable stay times, based on varying temperature and humidity levels.

Page 2 of TSTF-553, Revision 0, second paragraph states:

Depending on the plant design, the C REATCS and the CREVS [Control Room Emergency Ventilation System] or CREFS [Control Room Emergency Filtration System] may share components, such as ductwork, dampers, or doors. Inoperability of the CREATCS or of the CREVS or CREFS would not affect the operability of the other sy stem unless a shared component, such as ductwork, is affected.

The last sentence, although not incorrect, is li mited to passive components only. Depending on the system configuration, many plants are de signed to have flow in series through active components such as fans in CREVS and CREATCS.

In such cases, there is a potential for an inoperable CREATCS fan to render the CREVS also inoperable. On the other hand, an

inoperable chiller or a chilled water pump in CREATCS may not have an impact on CREVS operability. In this regard, the NRC staff requests additional discussion in the Traveler as to

how these situations regarding CREVS operabi lity would be implemented/handled in the TS, including possible entry into limiting condition for operation (LCO) 3.7.10.F.

Page 3 of TSTF-553, Revision 0, and first bulle t under the paragraph starting "The requirements are not consistent . . ." states:

NUREG-1432, the ISTS [improved standar d technical specifications] for Combustion Engineering plants, TS 3.7.11, provides 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore one of two inoperable control room cooling trains provided mitigating actions are implemented and the Reactor Coolant System (RCS) Specific Activity TS Limiting Condition for Operation (LCO) is met.

This allowance was approved by the NRC on May 30, 2013 as TSTF-426, Revision 5, "Revi se or Add Actions to Preclude Entry into LCO 3.0.3 - RITSTF Initiatives 6b & 6c" [. . .]. To date, this traveler has been adopted by four of the eight Combustion E ngineering plants.

The referenced TS 3.7.11 is incorrect for contro l room cooling trains. The information in TS 3.7.12 applies to control room cooling trains.

The reference to RCS Specific Activity TS LCO is also incorrect. It applies to Control Room Emergency Air Cleanup System (TS 3.7.11), not the control room cooling trains. Revise the references and the discussion to convey its intended purpose and use in TSTF-553.

• Section 3, Technical Evaluation, sec ond paragraph, last sentences states:

This evaluation may credit compensatory actions, such as use of normal ventilation systems, opening of cabinet doors, use of fans or ice vests, and opening control room doors or ventilation paths. If the control room envelope boundary is breached in order to provide cooling, the Actions of TS 3.7.10 (CREVS/CREFS) would also apply. This evaluation is performed for normal operating conditions including the availability of norma l electrical power based on the small likelihood of an event requiring the CREATCS during the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />

Completion Time.

In addition to what was stated in RAI #2, this is one area of the interdependency between CREATCS and CREVS. It brings out a conflict between the proposed compensatory actions under the TS for CREATCS and the existing mitigating actions under TS 3.7.10 for

CREVS/CREFS. Opening the control room doo rs would compromise th e control room boundary thus placing the plant in TS 3.7.10 Action Statement B.1, requiring immediate initiation of action to implement mitigating actions. Opening control room doors intentionally, in effect, could also render both trains of CREVS/CREFS to be inope rable due to inoperabl e control room boundary in MODE 1, 2, 3, or 4 during the 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, along with both trains of CREATCS. Why is this acceptable? What would then be the immediate mitigating actions that can be initiated under TS 3.7.10 Action Statement B.1? The Traveler should address this issue in mo re detail, and also provide guidance to licensees to address this condition in their plant-specific submittals.

The last paragraph in "Attachment 2 - Justification of the Control Room Area Temperature Limit" states:

This evaluation is performed for nor mal operating conditions including the availability of normal electrical power based on the small likelihood of an event requiring the CREATCS during the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time.

This statement made here and other places in the Traveler, also needs to consider control room habitability, not only from temper ature view point but also from other aspects applicable to the plant such as hazardous chemicals, smoke, etc. The CREFS plays a larger role in protecting the control room operators under such conditions. How does temperature mitigating actions such as opening control room doors impact the readi ness of CREFS to protect control room habitability from othe r aspects applicable?