ML20235W701

Safety Evaluation Re HPI Makeup Nozzle Cracking.Util Agreement to Record HPI Flowrate & Duration of Flow During HPI Actuation When SPDS Available Acceptable

ML20235W701
Person / Time
Site:	Arkansas Nuclear
Issue date:	07/15/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20235W675	List: ML20235W673 ML20235W701
References
NUDOCS 8707230665
Download: ML20235W701 (5)

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[# h UNITED STATES NUCLEAR REGULATORY COMMISSION y

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WASHINGTON, D. C. 20555 e

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION HIGH PRESSURE INJECTION MAKEUP N0ZZLE CRACKING FACILITY OPERATING LICENSE NO. DPR-51 ARKANSAS POWER AND LIGHT COMPANY ARKANSAS NUCLEAR ONE, UNIT NO. 1 DOCKET NO. 50-313 INTRODUCTION By letter dated March 10, 1986 (Reference 1), Arkansas Power and Light Company (AP&L; the licensee) submitted information to the Office of Nuclear Regulation (NRR) regarding implementation of recommendations contained in the B&W Owners Group Safe-End Task Force final report. The recommendations concerned operation of the makeup system, in particular the need for continuous makeup flow and the recommendation regarding logging of information about high pressure injection (HPI) initiations. Additional information was transmitted by licensee letter dated October 30, 1986 (Reference 2).

BACKGROUND Inspection Report 50-313/85-23 included a Notice of Deviation from previous commitments relative to implementation of the B&W Owners Group Safe-End Task Force Recommendations. The deviations concerned logging of HPI flow rate and duration for HPI actuations, and measurement of continuous makeup flow through the nozzles via bypass of Pressurizer Level Control Valve. The licensee's response to the Notice of Deviation (Reference 3) was in part:

"A continuous flow of makeup to the makeup nozzle is desirable to prevent severe thermal transients to the safe-end nozzle by maintaining it at the makeup temperature. In Inspection Report 50-313/85-23 the Inspector stated that the recommendation regarding a miminum bypass flow had not been met due to a flowmeter being pegged high. As stated in our letter of April 22, 1985, ANO-1 has a required minimum bypass flow of 1.0 gpm.

However, the flowmeter referenced by the Inspector cannot ensure this minimum flow. Due to the physical configuration of the makeup system the minimum makeup flow is approximately 15 gpm whenever the makeup system is operating. Normal makeup flow is from 30 to 60 gpm with a maximum of 160 gpm. Thus, the recommendation is satisfied by normal systems operations.

AP&L has re-reviewed our letter of April 22, 1985 regarding the logging of HPI initiations. This review has shown that the statement regardingThe logging of HPI initiations is not clear and could be misinterpreted.

intent of this statement was that AP&L had implemented the recommendation l to record HPI initiations. However, it was not intended to implyFour that of l

j all the parameters listed in the recommendations were recorded.

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the recommended six parameters are logged as noted by the inspector in the inspection report. The two remaining parameters, HPI flowrate and duration of HPI flow, are indicated but not recorded. The intent of the recommendations was to obtain information that might be used in analyses of future problems. Therefore, the additional parameters, while useful information, are not necessary for the safe operation of the HPI nozzles.

Additionally, the time and attention required to log these indications.

would distract the operators during unit trip recovery."

Region IV concluded that the licensee's reply constituted a revision of the commitments made in the April 22, 1985 letter (Reference 4) and recommended that it be brought to NRR's attention for review (Reference 5).

EVALUATION The basic consideration of the review is whether the ections taken by AP&L at ANO Unit 1, are consistent with the owners group recommendations (Reference 6);

and, if so, have they been implemented properly? The following recommendations were made by the owners group:

1. In terms of future repairs, it is recommended that:

Nozzles with Original Design Thertaal Sleeves

a. Reroll the upstream end of the thermal sleeve when inspections indicate that a gap exists. A 5.0% wall reduction is suggested to achieve an adequate interfacial residual stress and avoid stress corrosion cracking of the thermal sleeve.

Nozzles with Modified Design Thermal Sleeve

b. Repair and/or replace the damaged components if inspections reveal that abnormal conditions are present.

c. In either case, the affected utility should also verify that the components attached to the safe end meet the design constraints used in the stress analysis.

2. In order to ensure proper HPI/MU system operation, it is recommended that:

a. A continuous makeup flow via bypass of the Pressurizer Level Control l Valve should be maintained.

b. A known amount of bypass flow wh'.ch is greater than 1.5 gpm should be maintained and checked frequently (increased flows of up to about 10-15 gpm may be preferable depending upon plant configuration and operating practices).

c. There should be a consistent set of procedures to initiate continuous bypass flow RCS temperature RCS pressure Bypass flow rate Frequency of adjustment and calibration

d. The makeup tank temperature should be maintained within the proper control band as determined by other plant parameters.

e. In the event that future anomalies are discovered, proper logging of HPI initiations will be invaluable. This procedure should include:

Nozzles used Teinperature of BWST Temperature of cold leg before and after HPI initiation Pressure Flow rate Duration of HPI flow

3. An augmented inservice inspection plan as stated in Section 12.0 should be implemented.

4. A detailed stress analysis of a nozzle with a modified therual sleeve design should be performed to justify long term operation.

Section II of Reference 6 makes clear the intent of recommendation 2a. The closing paragraph of this section states:

In light of these findings, a minimum continuous makeup flow of 1-3 gpm (as originally specified) should adequately maintain all design parameters within analyzed limits and prevent thermal stratification.

However, it must also be pointed out that increasing continuous makeup flow may decrease the nozzle thermal stresses.

In the case of ANO Unit 1, the staff finds acceptable a 1.0 gpm continuous makeup flow via bypass of the Pressurizer Level Control Valve. Recommendation 2b requires the amount of bypass flow be known, be maintained and be checked frequently. The licensee has not made clear how this part of the recommendation  :

is satisfied at ANO Unit 1. The information regarding the minimum makeup tiow of 15 gpm whenever the makeup system is operating is not an issue in relation to Recommendation 2b. It is the capability to readily ascertain the minimum bypass makeup flow of 1.0 gpm that is the deviation from the licensee's commit-ment to comply with Recommendation 2b.

1 Regarding recommendation 2e, AP&L has agreed to record HPI flowrate and du'.'ation of HPI flow when SPDS is available (Reference 4). If SPDS is highly available (for more than 50% of HPI actuations), then along with previous  ;

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y ' r l commitments AP&L has satisfied this recommendation. However, at the time of the inspection the licensee was deviating from the recommendation of the B&W Owners Group Safe-End Task Force.

CONCLUSION The licensee committed to implement at ANO Unit 1, the recommendations of the B&W Owners Group Safe-End Task Force. A NRC inspector noted two instances of recommendations that were not wholly implemented. First, the continuous s4akeup flow via a bypass could not, on demand, be known or checked to assure that it is being maintained. The licensee should implement this part of the recommendation or provide a justification for not doing so.

Second, at the time of inspection the HPI flowrate and HPI duration of flow were not recorded. The licensee did not make it clear in early correspondence that the intent was not to record these two parameters. Subsequently, the licensee agreed to record these parameters during a HPI actuation when SPDS is available. The staff's understanding that the availability of SPDS is high; therefore the licensee's proposal is acceptable.

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Principal Contributor: R. Wright Date:

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REFERENCES

1. Letter from J. T. Enos, Arkansas Power and Light Company, to J. F. Stolz, USNRC, dated March 10, 1986, Accession Number 8603180144 860310.

2. Letter from J. T. Enos, Arkansas Power and Light Company, to J. F. Stolz, USNRC, dated October 30, 1986, Accession Number 8611120354 861030.

< 3. Letter from J. T. Enos, Arkansas Power and Light Company, to R. P. Denise, USNRC, dated November 29, 1985.

4. Letter from J. T. Enos, Arkansas Power and Light Company, to J. F. Stolz, USNRC, dated April 22, 1985, Accession Number 8505090334 850422.

5. Letter from J. E. Gagliardo, USNRC, to J. M. Griffin, Arkansas Power and Light Company, dated January 27, 1986.

6. Babcock and Wilcox, 177 Fuel Assembly Owners Group, Safe-End Task Force Report on Generic Investigation of HPI/MU Nozzle Component Cracking, B&W Document Number: 77-1140611-00, Accession Number 8302230370 830216.

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