RBG-26365, Forwards Rept on ATWS Mods,Per Paragraph (c)(6) of 10CFR50.62,demonstrating Adequacy of Facility Sys Required to Meet ATWS Rule,Per Util .All Mods Planned to Be Completed During Refueling Outage Scheduled for 870915

Forwards Rept on ATWS Mods,Per Paragraph (c)(6) of 10CFR50.62,demonstrating Adequacy of Facility Sys Required to Meet ATWS Rule,Per Util .All Mods Planned to Be Completed During Refueling Outage Scheduled for 870915

ML20236H066
Person / Time
Site:	River Bend
Issue date:	07/31/1987
From:	Booker J GULF STATES UTILITIES CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
RBG-26365, NUDOCS 8708050051
Download: ML20236H066 (13)

Text

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l GULF STATES UTELIT1ES COMPANY ]77 Ok HIVER DEND $1 ATiON POST OTHCl 00X 220 ^ ST HtANCISVILLE LOUISLANA 7J776 ARE A CODE 604 635 609M 34ti 18051 l

July 31, 1987 RBG - 26365 File Nos. 09.5, 9.23 i

l U.S. ' A ear Regulatory Commission Docutaent Control Desk Washington, D.C. 20555 1

Gentlemen::

River Bend Station - Unit 1 Docket No. 50-458

Gulf States Utilities Company (GSU) hereby submits the enclosed i report on Anticipated Transients Without Scram (ATWS) modifications as required by paragraph (c)(6) of the ATWS rule (10CFR50.62). This report demonstrates the adequacy of River Bend Station Unit 1 systems required to meet the ATWS rule as committed in GSU's June 26, 1985 letter (RBG-21392). All ATWS required modifications are planned to be completed during the first refueling outage scheduled to begin on September 15, 1987.

Applicable Technical Specification changes associated with these modifications will be requested under a separate cover letter.

Sincerely, 870B050051By70 458 DR ADOCK O PDR hJ.E. Booker Manager-River Bend Oversight i River Bend Nuclear Group JEB/ ERG / /ch  !

Attachments cc: Mr. Robert D. Martin, Regional Administrator U.S Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 NRC Resident Inspector P.O. Box 1051 St. Francisv111e, LA 70775 h

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ATTACHMENT 1 River Bend Station (RBS) - Unit 1 Gulf States Utilities Company Response to ATWS Rule, 10CFR50.62 1.0 Introduction Paragraph (c)(6) of 10CFR50.62, the NRC rule on Anticipated Transients Without Scram (ATWS), requires submittal of information to demonstrate the adequacy of systems installed to meet paragraphs (c)(1) through (c)(5) of the rule. Paragraphs (c)(3), (4) and (5) are applicable to RBS and will be addressed in this report. These paragraphs describe requirements for Alternate Rod Insertion (ARI),

Standby Liquid Control (SLC), and Reactor Recirculation Pump Trip (RPT). In this report, each system is addressed as to RBS design implementation and compliance with the rule. In December 1985, General Electric Company (GE) submitted to the NRC a Licensing l Topical Report titled, " Anticipated Transients Without Scram, Response to NRC ATWS Rule, 10CFR50.62" (NEDE-31096-Ft. This report was prepared by CE for the Boiling Water Reactor Owner's Group (BWROC) to generically address compliance of GF-BWRs with the ATWS Rule. This report will be referenced herein as applicable to RBS.

On October 21, 1986, the NRC staff issued a Safety Evaluation Report (SER) on the report giving additional guidance on compliance with the ATWS Rule. The following information contains RBS specific design criteria as required by 10CFR50.62(c)(6) and which address NRC SER comments.

l 2.0 Alternate Rod Insertion (ARI) 2.1 ATWS Rule 10CFR50.62 (c)(3)

"Each Boiling Water Reactor must have an Alternate Rod Injection (ARI) system that is diverse (from the reactor trip system) from sensor output to the final actuation device. The ARI system must have redundant scram air header exhaust valves. The ARI must be designed to perform its function in a reliable manner and be ,

independent (from the existing reactor trip system) from sensor output to the final actuation device."

2.2 RBS Design Implementation The RBS ARI system design provides a diverse and independent means of inserting control rods. This is accomplished by a redundant two-out-of-two (Iow-low water level, high reactor pressure or manual initiation) logic which automatically isolates and vents the scram air header, causing the existing scram inlet and outlet valves to open allowing the control rod drive mechanisms to insert rods (see Figure 3).

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The ARI system is independent from' the existing Reactor  !

Protection System (RPS) up to the scram aJr header. It is common l to the RPS scram function in the hydraulic control units, control i rod drive mechanisms and control rods. The initiation signals

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and logic along with the power supplies and ARI valves are independent from RPS. The power for ARI logic and valves is ,

provided from a non-class IE 125 VDC power supply which is independent from RPS power supplies. ARI will function following any loss of offsite power.

The ARI system is redundant to the existing back up scram valves, but is not redundant within itself. That is, redundant vent paths are not provided within ARI. All ARI valves must actuate to meet the syetem performance requirements. The system design is diverse from the existing RPS in that it requires ,

energize-to-function logic end valves instead of de-energize-to-trip. In addition, DC power is used for ARI instead of AC power for both logic and valve actuation.

The ARI system is designed to reduce the possibility of inadvertent actuation. This is accomplished through the use of two-out-of-two logic . The logic requires two level, pressure or manual initiation signals to initiate ARI. In addition, each cent path has two isolation valves, both of which must open to exhaust the scram air header. ARI valve arrangement is shown in Figure 4.

The ARI design includes indication and control of system functions in the Main Control Room. This includes manual initiation pushbuttons along with indication of ARI " initiated",

"in test," " manually armed," "out of service" and " ready to reset."

2.3 RBS Compliance The NRC's SER includes a checklist in Appendix A which defines system design requirements for ARI. Attachment 2 to this report ,

addresses each of the items found in the SER Appendix A. l The RBS ARI system design was based on the design described in the GE Licensing Topical Report on ATWS. As demonstrated by the 1 information in Section 2.2 and Attachment 2 of this report, the RBS design meets the requirements of 10CFR50.62 (c)(3) and the '

guidance found in the SER. The ARI system will be installed during the first refueling outage scheduled to begin on September 15, 1987.

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3.0 Standby Liquid Control (SLC) 3.1 ATWS Rule - 10CFR50.62(c)(4)

"Each Boiling Water Reactor must have a Standby Liquid Control System (SLCS) with a minimum flow capacity and boron content equivalent in control capacity to 86 gallons per minute of 13 weight percent sodium pentaborate solution. The SLCS and its injection location must be designed to perform its function in a reliable manner ..."

3.2 RBS Design Implementation The existing SLC system at RBS is described in Section 9.3 of the FSAR. It will be modified by increasing the enrichment of Boron-10 in the sodium pentaborate solution. By increasing enrichment, the design and operation of the system will be unchanged except that less solution volume will be required. In addition, solution concentration will be reduced to less than or equal to 9.5% by weight. The reduced volume and concentration are offset by the enrichment required to meet the equivalent reactivity control requirements of the ATWS rule and the original design requirements of the SLC system. The initial enrichment is designed to be 65% Boron-10. With an enrichment of 65% Boron-10, a minimum concentration of 6.5% by weight will be required. This is based on a pump flow rate af 41.2 GPM and an equivalent required flow rate of 66 GPM (for 218 inch diameter vessel). The minimum required volume in the tank will be based on tha actual enrichment, the concentration of Boron-10 in the solution and the minimum quantity of Boron-10 required to meet design requirements.

The change in enrichment will be accomplished as described in Section 2.2.3 of NEDE-31096-P and accepted by the NRC in the SER dated October 21, 1986. The only exception is that mixing of the 4 solution will not be accomplished as described in Section 2.2.3.2 of NEDE-31096-P. At RBS, the solution will be prepared by mixing enrfched granular sodium pentaborate in water.

Concentration will be limited to a maximum of 9.5% such that opertble heat tracing is not required. With concentration at or below 9.5%, the saturation temperature of sodium pentaborate is less than 39 degrees F. This is less than the minimum ambient temperature of the SLC tank room and thus heat tracing is not i required to be maintained operable.

3.3 RBS Compliance The RBS SLC system will meet the requirements of 10CFR50.62 (c)(4) and the NRCs SER dated October 21, 1986, with system modifications as described in Section 3.2 above. Equivalent control capacity, as described in Section 4.2.2 of the SER, will be accomplished by use of an enriched sodium pentaborate solution 1

as accepted in Section 5.2.3 of the SER. This section of the SER requires that periodic testing be conducted to verify isotopic ,

I concentration. Because enrichment of Boron-10 can only change when boron or a compound containing boron is added to the solution, testing for enrichment will be conducted only when boron is added to the solution.

Implementation of the enriched sodium pentaborate solution in the SLC system is scheduled to be completed during the first refueling outage which is scheduled to begin on September 15, 1987.

4.0 Reactor Recirculation Pump Trip (ATWS-RPT) j 4.1 ATWS Rule - 10CFR50.62 (c)(5)

"Each Boiling Water Reactor must have equipment to trip the reactor coolant recirculation pumps automatically under l

conditions indicative of an ATWS. This equipment must be designed to perform its function in a reliable manner."

4.2 RBS Design Implementation  :

1 l ATWS-RPT is currently implemented in the design of the plant as 1 l described in FSAR section 7.7.1.2 with the exception that the l initiation logic has been revised to prevent inadvertent  !

actuation of ATWS-RPT. The original logic consisted of two trip i systems each with one-out-of-four logic (low water level or high reactor pressure) which would trip both recirculation pumps (Figure 1). This logic has been revised to a two-out-of-two l logic as shown in Figure 2. This modification was made due to l inadvertent pump trips which occurred during initial plant j start-up. Upon receipt of an initiation signal, two circuit I breakers in the normal power supply and one circuit breaker in j the low frequency motor generator (LEMG) power supply to the pump 1 I

motor are opened.

ATWS-RPT is independent from and physically separated for RPS I generated RPTs in sensor initiation logic, power supplies, and j breakers. ATWS-RPT will function with a loss of offsite power.

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ATWS-RPT is ?iverse from RPS in that ATWS-RPT uses DC power instead of AC -a is used in RPS. ATWS-RPT is testable at power except for breaker operation.  !

4.3 RBS Compliance The RBS ATWS-RPT system is currently in compliance with the I requirements of the ATWS rule as discussed in Section 4.2 of this j report. However, the RBS design differs in part with the 1 requirements of the staff SER dated October 21, 1986. The SER states that the " modified Hatch" and the "Monticello" designs are acceptable to the staff and that other designs should be shown

equivalent. The difference in the RBS design and the Monticello design is that redundant breaker trip coils are not used in the RBS design. The RBS design does include two breakers in the primary power supply and one in the LFMG power supply. The use of redundant actuation devices is not required by the ATWS rule.

In addition, the SER is inconsistent with the ATWS Statement of Considerations titled " Considerations Regarding System and Equipment Specifications", published in the Federal Register on July 31, 1984, which states that redundancy is "not reqrired".

Based on this, the RBS ATWS-RPT design is in compliance with the rule and the Statement of Considerations with the currently installed system.

5.0 Technical Specifications RBS Technical Specifications currently define limiting conditions for operation and surveillance requirements for ATWS-RPT and for the SLC System. (Tech Spec 3/4.3.4 and 3/4.3.4). The SLC technical specification sill be revised to reflect new requirements due to enrichment of Boron-10. These changes will be requested under separate cover letter.

6.0 Conclusions The information supplied in the preceding sections demonstrates that RBS will meet the requirements of 10CFR50.62. Upon completion of modifications to SLC and ARI, RBS will be in compliance with the-rule prior to startup following the first refueling outage. This submittal completes the requirements of 10CFR50.62 (c)(6).

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ATIACHMENT 2 RBS Response to Staff SER, Appendix A Checklist For Plant Specific Review of Alternate Rod Injection System (AR1)

Confermance  !

with.ARI SER

1. ARI system function time Rod injection motion will begin within 15 seconds and be completed with 25 seconds from AR1 initiation. yes

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2. Safety-related requirements (a) Class IE isolators are used to interface with l safety-related systems n/a **

(b) Class IE isolators are powered from a Class IE source n/a **

(c) Isolator qualification documents are available for staff audit n/a **

3. Redundancy The ARI system performs a function redundant to the backup scram system yes

4. Diversity from existing RTS (a) ARI system is energize-to-function yes (b) ARI system uses DC powered valves yes (c) Instrument channel components (excluding sensors but including all signal conditioning and isolation devices) are diverse from the existing RTS components yes

5. Electrical independence from the existing RTS (a) ARI actuation logic separate from RTS logic yes (b) ARI circuits are isolated from safety-related circuits n/a **

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6. Physical separation from the existing RTS (a) ARI system is physically separated from RTS yes

7. Environmental Qualification ARI equipments are qualified to conditions during an ATWS event up to the time the ARI function is completed yes

8. Quality Assurance (a) Comply with Generic Letter 85-06 yes

9. Safety-related power supply (a) ARI system power independent from RTS yes (b) ARI system can perform its function during any loss-of-offsite power event yes

10. Testability at Power (a) ARI testable at power yes (b) Bypass features conform to bypass criteria used in RTS n/a ***

11. Inadvertent Actuation (a) ARI Actuation setpoints will not challenge scram yes (b) Coincident logic is utilized in ARI design yes

12. Manual Initiation (a) Manual initiation capability is provided yes

13. Information Readout (a) Information readout is provided in main control room yes

14. Completion of protective action once it is initiated yes

• NOTE: This criteria will be proven by-post-installation test.

• • NOTE: The ARI design is independent from RPS; thus the use of electrical isolators is not applicable to this design.

• • • NOTE: The ARI design does not allow for bypassing any safety 1 functions, thus this item is not applicable. >

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