1CAN089801, Application for Amend to License DPR-51,revising TS 3.3.4.B Requirements for Sodium Hydroxide Tank Concentration

Application for Amend to License DPR-51,revising TS 3.3.4.B Requirements for Sodium Hydroxide Tank Concentration

ML20236Y506
Person / Time
Site:	Arkansas Nuclear
Issue date:	08/06/1998
From:	Hutchinson C ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20236Y507	List: 1CAN089801, Application for Amend to License DPR-51,revising TS 3.3.4.B Requirements for Sodium Hydroxide Tank Concentration ML20236Y508
References
1CAN089801, 1CAN89801, NUDOCS 9808120266
Download: ML20236Y506 (11)

Text

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. ML_ ..s' Entergy oper tions,inc.

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C. Randy Hutchinson vu Presost August 6,1998 ICAN089801 l

t U. S. Nuclear Regulatory Commission Document Control Desk Mail Station OPI-17 l Washington, DC 20555

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Subject:

Arkansas Nuclear One - Unit 1 Docket No. 50-313 License No. DPR-51 Technical Specification Change Revising The Arkansas Nuclear One - Unit 1 Sodium Hydroxide Tank Limits Gentlemen:

Attached for your review and approval is a proposed change to the Arkansas Nuclear One -

- Unit 1 (ANO-1) Technical Specification (TS) 3.3.4.B requirements for Sodium Hydroxide (NaOH) Tank concentration. The proposed change revises the minimum concentration limit from the current value of 15 wt% to a value of 5.0 wt%. The maximum concentration limit is revised from the current value of 20.8 wt% to a value of 16.5 wt%. The proposed change also revises the minimum specified tank volume to refer to the parameter used in the analysis with no allowance for instrument uncertainty and deletes the maximum specified tank volume.

Therefore, the associated bases have also been revised.-

The proposed change is required to preclude a potential for post Loss-of-Coolant-Accident (LOCA) Reactor Building sump / spray solutions to have pH values higher than those evaluated for EQ considerations and hydrogen generation rates. This potential existed due to the method used for quoting post-LOCA sump / spray pH values at elevated Reactor Building temperatures being inconsistent with the methods used to evaluate the effects of sump / spray pH on equipment and Reactor Building atmosphere.

The proposed change has been evaluated in accordance with 10CFR50.91(a)(1) using criteria in 10CFR50.92(c) and it has been determined that this change involves no significant hazards considerations. The bases for these determinations are included in the attached submittal.

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i Entergy Operations requests that the effective date for this change be within 30 days of  !

approval. Although this request is neither exigent nor emergency, your prompt review is <

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U. S. NRC

, August 6,1998

.. . ICAN089801 Page 2 Very truly you ,

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, // i I/ WS Attachments i To the best of my knowledge and belief, the statements contained in this submittal are true.

SUBSCRIBED AND SWORN TO beror a Notary E blic in and for [44&#u County and the State of Arkansas, this day of ,1998. /

f LL JLa Motary fublif f My Commission Expires 9//e // M00 sg / .

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' U. S. NRC

, August 6,1998 ICAN089801 Page 3 cc: Mr. Ellis W. Merschoff Regional Administrator U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 Mr. William D. Reckley NRR Project Manager Region IV/ANO-1 & 2 U. S. Nuclear Regulatory Commission NRR Mail Stop 13-H-3 One White Flint Nonh 11555 Rockville Pike Rockville, MD 20852 Mr. David D. Snellings Director, Division ofRadiation Control and Emergency Management

. Arkansas Department ofHealth 4815 West Markham Street Little Rock, AR 72205 l

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.p 0 g ATTACHMENT

_TD ICAN089801 PROPOSED TECHNICAL SPECIFICATION AND RESPECTIVE SAFETY ANALYSES IN THE MATTER OF AMENDING LICENSE NO. DPR-51 ENTERGY OPERATIONS. INC.

ARKANSAS NUCLEAR ONE. UNIT ONE POCKET NO. 50-313 I

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.- . Page1 of7 DESCRIPTION OF PROPOSED CHANGES The Sodium Hydroxide (NaOH) tank concentration limits specified by Arkansas Nuclear One

- Unit 1 (ANO-1) Technical Specification (TS) 3.3.4.B have been revised from a minimum value of 15 wt% to a value of 5 wt% and from a maximum value of 20.8 wt% to a value of 16.5 wt%. The limit associated with the NaOH tank minimum level has been revised to specify the volume of NaOH required by the safety analysis instead of the level that is j currently specified. The proposed volume does not contain allowances for instrument uncertainty. Therefore, the associated Bases have also been revised to properly characterize the values specified. The limit associated with the NaOH tank maximum level has been  !

deleted. j l

HACKGROITND In the event of a major Loss-of-Coolant-Accident (LOCA), the reactor building spray system sprays a chemical solution into the reactor building atmosphere to reduce the post-accident energy and to reduce fission product inventorv in the reactor building atmosphere. The system consists of two pumps, two reactor be.ilding spray headers, and the necessary piping, valves, instrumentation and controls. In addition, a tank (TIO) supplies NaOH for iodine removal and for pH adjustment of the borated water.

A high reactor building pressure signal from the Engineered Safeguards Actuation System (ESAS) initiates reactor building spray operation. The two pumps start and take suction initially from the Borated Water Storage Tank (BWST). The spray solution is injected in the reactor building through the spray headers and nozzles. Upon receipt of the safeguards signal, the valves at the outlet of the NaOH tank also open, permitting gravity draining and mixing with water from the BWST. The NaOH system is designed to permit gravity draining of T10 at a rate commensurate with the draining rate of the BWST. The tank concentration and level are such that the proper quantity of NaOH is injected for pH control. The NaOH tank is described in ANO-1 Safety Analysis Report (SAR) Sections 6.2.2.1 and 6.2.2.4.6.

The post-LOCA reactor building conditions reported in the ANO-1 SAR included the expected values of pH of the reactor building sump and spray water solutions. The pH of a solution is a function ofits temperature and the reported values were given for the elevated temperatures expected for these conditions. The reported pH values are conservatively calculated using the maximum and minimum boron or sodium hydroxide concentrations of the various water sources that can contribute to the post-LOCA sump and spray solutions.

The spray and sump pH values are considered in the evaluation of effects of the post-LOCA environment on equipment r.nd reactor building atmosphere. Values of pH are used in establishing test requirements for environmental qualification (EQ), for determining post-l LOCA hydrogen generation rates, for evaluating the potential for stress corrosion cracking, and for evaluating iodine retention. The pH values used for these evaluations were based on solutions at room temperature,77 F. For example, the solutions used in the EQ testing of components are typically prepared and the pH measured at room temperature. At

Attachment to ICAN089801

. ' Page 2 of 7 temperatures greater than 77 F (25 C), the actual pH will be slightly lower fc. pH values significantly higher than 7.0 (i.e., highly caustic solutions will not appear to be as caustic).

Calculated sump / spray pH values of 10.5, reported in the SAR at containment temperature of 200 F, could be as high as 11.5 when adjusted to 77 F. The pH values reported in the SAR may thus be non-conservatively low with respect to these evaluations.

Elevated temperature pH values have been reported in the SAR because they were conservatively low for the purposes ofiodine retention evaluation. Higher pH values result in better iodine retention and thus lower offsite dose consequences. However, more recent studies have demonstrated, and regulatory guidance changes have acknowledged, that iodine retention is much less dependent on pH than previously assumed and remains quite effective in spray solutions having low pH values. NUREG-0800, Standard Review Plan (SRP), Section 6.5.2, " Containment Spray as a Fission Product Cleanup System Review Responsibilities,"

Revision 2, dated December 1988, supports this position even at a pH as low as 5.0 and references several publications for supporting documentation.

Stress corrosion cracking can be accelerated by lower pH conditions if not controlled.

However, the ANO evaluations of stress corrosion cracking are unaffected because sump and spray pH values are well above the minimum pH values, below which this process is expected to occur. Other forms of component corrosion, however, are accelerated at higher pH values.

The higher pH values, resulting from the adjustment to room temperature, may also adversely affect EQ test results and hydrogen generation rates.

As a result of this condition, administrative controls have been implemented on the ANO-1 BWST, Core Flood Tank (CFT), and Reactor Coolant System (RCS) boron concentrations and NaOH tank concentration to ensure sufficiently low sump / spray solution pH even when adjusted to room temperature.

DISCUSSION OF CH ANGE ANO-1 has calculated a new set of sodium hydroxide concentration limits for the NaOH tank.

Although ANO-1 is not specifically committed to NUREG-0800, Standard Review Plan, guidance contained in SRP Section 6.1.1, " Engineered Safety Features Materials Review Responsibilities," Revision 2, dated July 1981, and Section 6.5.2, " Containment Spray as a Fission Product Cleanup System Review Responsibilities," Revision 2, dated December 1988, was used in developing the new limits. The minimum concentration is based on the NUREG-0800 value for acceptable post-sump recirculation operation (pH >7.0). SRP 6.5.2 permits spraying of an unbuffered boric acid solution during the initial injection phase of a LOCA when the spray solution is drawn from the BWST, and concludes that the iodine removal rate of plain boric acid is high enough to make a spray additive unnecessary. However, the SRP does state that the pH of the spray solution should be adjusted to greater than 7.0 by the onset l of the recirculation mode to prevent the re-evolution ofiodine during operation of the reactor l building spray in the recirculation mode. Since the sump pH is expected to be greater than 7.0 l by the onset of recirculation, the proposed change in concentration is not expected to affect t

Attachment to 1CAN089801 Page 3 of 7 either the iodine removal from the reactor building atmosphere or its retention in the sump fluid.

The maximum concentration is based on a sump pH <10.5, which is unchanged by this calculation, to minimize the potential for equipment degradation from caustic attack.

Earlier NRC guidance, and the current ANO-1 licensing basis, specify a lower limit for sump pH of 8.5, so the change in the reactor building sump pH range represents a change in the ANO-1 licensing basis. This change in the sump lower pH limit from 8.5 to 7.0 is expected to have no negative effects with respect to stress corrosion cracking since SRP Section 6.1.1, Rev 2 states, " Experience has shown that maintaining the pH of borated water solutions at this level will help to inhibit initiation of stress corrosion cracking of austenitic stainless steel components. The values for sodium hydroxide concentration have also been evaluated for reactor building spray (prior to sump recirculation) short term pH concerns and small-break l LOCA concerns when the reactor building pressure does not automatically initiate reactor {

I building spray and manual operator actions are needed to drain the NaOH tank into the sump to control recirculation pH.

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With respect to hydrogen generation, SRP Section 6.1.1, Rev 2, Branch Technical Position MTEB 6-1 states, "lf a pH greater than 7.5 is used, consideration should be given to the ,

hydrogen generation problem from corrosion of aluminum in the containment." Since the 1 minimum sump pH has been reduced from 8.5 to 7.0 and the maximum limit is unchanged, the effects of hydrogen generation are conservatively bounded by existing evaluations. ,

The calculated pH values were determined at 77 F (25 C) to reflect the standard temperature )

quoted for environmental testing purposes. If the operating temperature is higher than 77 F, I then the actual pH will be slightly lower for those pH values significantly higher (i.e., more caustic) than 7.0. All pH values were computed by the MULTEQ code, Version 2.2 for the personal computer.

The concentration limits were developed on the basis of the most significant and limiting requirements for the various phases of reactor building spray operation and long term sump pH limitations. A summary of the tank volumes and chemical concentrations used in the calculation are as follows:

Source / Maximum Minimum Maximum Minimum.

Chemical Volume (gal.) Volume (gal.) Concentration Concentration BWST/ Boron 425200 320300 2670 ppm 2270 ppm CFT/ Boron 17700 13000 3500 ppm 2270 ppm RCS/ Boron 63500 63500 2270 ppm 0 ppm j NaOH Tank / 13600 5000 Determined by Determined by NaOH calculation calculation l

i (5 wt%) (16.5 wt%)

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ICAN089801

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Page 4 of 7 l Equilibrium sump pH can be determined by considering a singie point. The most important time for sump pH calculations is at the beginning of the recirculation phase after all the borated water and sodium hydroxide is added. Both an upper and lower limit are projected based on worst case combinations in both extremes of quantity and concentration of the borated water sources and sodium hydroxide tank.

l The concentration limits for worst case spray pH are based on the maximum amount of sodium hydroxide versus borated water to result in a caustic spray. The target pH for this worst case spray was a MULTEQ calculated pH of 10.5, which ensures the upper limit used in environmental qualification of components is not exceeded. Extreme high and low flow combinations for both the BWST and NaOH tank were picked. These flow values are transient in that the flow rates vary with time, so the results are conservative if used to project the overall concentration over the total spray time interval.

In order to maintain the sump recirculation pH between 7.0 and 10.5, the NaOH tank l concentration will be maintained between 5.0 wt% and 16.5 wt%. These concentrations will j ensure that the maximum reactor building spray pH will not exceed a pH of 10.5, except for a short period of time during spray initiation. The short duration maximum spray pH is calculated to remain below 12.5, a value which has been shown to be acceptable in the EQ evaluations.

ANO proposes to revise the limits specified for the NaOH tank level to reflect the volumes used in the safety analysis. The NaOH tank minimum and maximum volumes are used as inputs to determine reactor building flooding levels and minimum sump levels for pump Net Positive Suction Head (NPSH) and reactor building sump vortex concerns. The NaOH tank range of concentration values and fluid levels are used to determine the sump / spray pH values to ensure that adequate iodine removal occurs to limit offsite doses and to ensure that equipment coming into contact with the fluid will continue to operate for the duration of the accident (equipment qualification). These analyses are discussed in more detail below. l Post-LOCA Reactor Building Water Levej The post-LOCA reactor building sump calculation considers the contribution of water volume from the reactor coolant system, BWST, core flood tanks, and NaOH tank.

Recent calculations show that the required NaOH tank contribution to the post-LOCA minimum sump level is bounded by a volume of 4,000 gallons, based on an initial tank volume of 9,000 gallons. The proposed TS minimum volume of 9,000 gallons preserves this l contribution.

l The maximum post-LOCA reactor building sump level calculation assumes 13,054 gallons for l

sump flooding concerns. This value exceeds the physical capacity of the NaOH tank, which is approximately 12,500 gallons. Since the physical dimension of the NaOH tank bounds the maximum volume input assumptions no maximum limit is proposed for the ANO-1 TS NaOH volume.

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l Low Pressure Iniection and Reactor Buildina Sorav Pumo Performance Durino Post-LOCA

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Symp Recirculation The NPSH calculations for the low pressure injection and reactor building spray pumps i reference the minimum post-LOCA reactor building sump level. The minimum contribution from the NaOH tank assumed for the purposes of the level calculation is bounded by a volume l of 4,000 gallons, based on an initial NaOH tank volume of 9,000 gallons. The low pressure l

injection and reactor building spray pump NPSH values will not be adversely affected by the

proposed change in the TS minimum volume for the NaOH tank.

Reactor Building Sump Vortexing The ANO post-LOCA reactor building water level calculation is based on assumed minimum j levels in the reactor coolant system, BWST, core flood tanks, and NaOH tank. The minimum 1 contribution from the NaOH tank assumed for the purposes of the level calculation is bounded by a volume of 4,000 gallons, based on an initial NaOH tank volume of 9,000 gallons. Sump vortexing will therefore not be adversely affected by the proposed change in the TS minimum volume for the NaOH tank.

Post-LOCA Reactor Building Pressure and Temperature Profiles The ANO-1 reactor building pressure and temperature analysis conservatively neglects the NaOH tank volume and therefore places no limiting assumptions on NaOH tank volume.

Rost-LOCA Offsite Dose The minimum NaOH tank volume of 9,000 gallons ensures a sump pH of 7.0 or higher, as previously discussed. Using NUREG-2900, a value for the partition coefficient of greater 4

than 10 and less than 10' was derived using the assumed iodine concentration ranges, a pH of 4

7.0, and a recirculation time of 0.55 hours6.365741e-4 days <br />0.0153 hours <br />9.093915e-5 weeks <br />2.09275e-5 months <br /> (1980 seconds). For conservatism, the value of 10 was used. This value is consistent with the previous analysis.

j Additionally, a Decontamination Factor (DF) was also derived using the 10' partition factor and a minimum sump volume. These inputs resulted in a DF of 300, but the conservative  ;

value of 200 was used as suggested by the standard review plan. This value is consistent with j the previous analysis. I t

i In summary, the proposed TS minimum volume requirement will ensure a post-LOCA reactor ]

l building sump pH of 7.0 or higher and will therefore maintain the same basis for the iodine l partition coefficient and DF as previously analyzed, and will not adversely impact these values. !

Since the maximum sump pH was unchanged by the proposed changes in NaOH tank concentration and level, the basis for the iodine partition coefficient and DF are maintained as previously analyzed, and will not be adversely impacted. )

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. .' Page 6 of 7 l Summary of Accident Analysis Inputs For NaOII Tank l

Accident Analyses Input Assumptions Associated With Current Values Revised Values NaOliTank NaOli Tank Maximum Volume for 13,054 gallons 13,054 gallons Flooding Calculations NaOH Maximum Volume for sump 13,600 gallons 13,600 gallons pH Calculations NaOH Tank Minimum Volume for 10,600 gallons resulting in 9,000 gallons resulting in NPSH Calculations flow of 5,000 gallons flow of 24,000 gallons NaOH Minimum Volume for sump 10,600 gallons resulting in 9,000 gallons resulting in pH Calculations flow of 10,048 gallons flow of 24,000 gallons Long Term Sump pH range 8.5 to 10.5 7.0 to 10.5 Iodine Partition Factor 10' 10' l~

DF 200 200 This proposed minimum volume corresponds to an actuallevel of 26 feet at 77 F and a NaOH concentration of 5.0 wt%. Instrument uncenainties associated with the level instmmentation, as determined in ANO Calculation 91-E-0019-01, will be controlled administratively and will be applied to the procedures associated with NaOH tank level. The Bases associated with TS

3.3.4.B have been revised to equate levels to the analytical volumes, and to state that additional instrument uncertainty must be applied to these values when implemented in the plant.

This change should reduce the administrative burden of the Technical Specification change process for both the NRC and ANO in the event the current level instrumentation is replaced in the future. This type of change could be performed under the ANO 50.59 process as a l plant modification without prior NRL approval. The instrument uncertainty calculation, and I other associated analyses, are available on site for your review.

DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATION An evaluation of the proposed change has been performed in accordance with 10CFR50.91(a)(1) regarding no significant hazards considerations using the standards in l 10CFR50.92(c). A discussion of these standards as they relate to this amendment request I i follows:

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Attachment te ICAN089801 Page 7 of 7 Criterion 1 - Does Not involve a Significant Increase in the Probability or Consequences of an Accident Previously Evaluated.

Sodium hydroxide is not an accident initiator. It is, however, a contributor to the mitigation of the effects of a Loss-of-Coolant-Accident (LOCA). The proposed change in NaOH tank concentration results in changing the expected post-LOCA reactor building sump pH. The l

reduction in the lower value of sump pH, from 8.5 to 7.0, is acceptable based on guidance j contained in NUREG-0800, Standard Review Plan, Section 6.5.2, " Containment Spray as a )

Fission Product Cleanup System Review Responsibilities," Revision 2, December 1988. This guidance allows the assumption oflong-term iodine retention when the equilibrium sump pH, after mixing and dilution with the primary coolant and ECCS injection, is above 7.0.

Although the change allows the volume of the NaOH tank to be maintained at a lower volume, the proposed minimum volume bounds the analyses of concern.

Therefore, this change does nat involve a significant increase in the probability or consequences of any accident previously evaluated.

Criterion 2 - Does Not Create the Possibility of a New or Different Kind of Accident from any Previously Evaluated.

Sodium hydroxide is added for iodine removal and for pH adjustment of the borated water in the reactor building sump following a LOCA. The proposed changes in NaOH tank concentration and volume introduce no new mode of plant operation.

Therefore, this change does agi create the possibility of a new or different kind of accident from any previously evaluated.

Criterion 3 - Does Not Involve a Significant Reduction in the Margin of Safety.

The proposed change in NaOH tank concentration results in changing the expected post-LOCA reactor building sump pH. This proposed change does involve an incremental reduction in the margin to safety since iodine retention is dependent on the pH of the sump / spray solution. However. this reduction is not considered significant in that the effect of the change in sump pH, from 8.5 to 7.0 has a relatively minor effect on iodine retention, as supponed by Standard Review Plan (NUREG-0800), Section 6.5.2, Revision 2, dated December 1988. Although the change allows the volume of the NaOH tank to be maintained at a lower volume, the proposed minimum volume bounds the analyses of concern.

Therefore, this change does nat involve a significant reduction in the margin of safety.

Therefore, based upon the reasoning presented above and the previous discussion of the amendment request, Entergy Operations has determined that the requested change does not

{ involve a significant hazards consideration.

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