ML17305B701

Corrected Response to NRC Concerns Noted in Insp Repts 50-528/91-20,50-529/91-20 & 50-530/91-20.Corrective Actions: New Calculation Method for Single Separation Technique Being Investigated

ML17305B701
Person / Time
Site:	Palo Verde
Issue date:	07/29/1991
From:	James M. Levine ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
NUDOCS 9108300136
Download: ML17305B701 (11)

Text

"!, ACCELERATED DISTRIBUTION DEMONSTPWTION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

CCESSION NBR-9108300136 DOC.DATE: 91/07/29 NOTARIZED: NO DOCKET FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona Publi 05000530 AUTH.NAME AUTHOR AFFILIATION LEVINE,J.M.

Arizona Public Service Co. (formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION MARTIN,J.B.

Region 5 (Post 820201)

I

SUBJECT:

Corrected response to NRC concerns noted in Insp Repts 50-528/91-20,50-529/91-20

& 50-530/91-20.Corrective actions:

new calculation method for single separation technique being investigated.

DISTRIBUTION CODE: IEOID COPIES RECEIVED:LTR j'NCL r

SIZE:

TITLE: General (50 Dkt)-Insp Rept/Notice of Violation Response D

NOTES:STANDARDIZED PLANT Standardized plant.

Standardized plant.

RECIPIENT ID CODE/NAME PD5 PD THOMPSON,M ERNAL: ACRS AEOD/DEIIB DEDRO NRR MORISSEAU,D NRR/DLPQ/LPEB10 NRR/DREP/PEPB9H NRR/OTSB 11E22 NUDOCS-ABSTRACT OGC/HDS1 RGN5 FILE 01 EXTERNAL: EGGG/BRYCE, J.H.

NSIC NOTES:

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1'ECIPIENT ID CODE/NAME TRAMMELL,C AEOD AEOD/TPAB NRR HARBUCK,C.

NRR SHANKMAN,S NRR/DOEA/OEAB NRR/DST/DIR 8E2 NRR/PMAS/ILRB12 OE DIR EG--FILI" NRC PDR COPIES LTTR ENCL 1

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D NOTE TO ALL"RIDS" RECIPIENTS:

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PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, t

ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAMEFROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED:

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Arizona Public Service Company PALO VERDE NUCLEAR GENERATING STATION P.O. BOX 52034

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PHOENIX. ARIZONA85D72-2D34 JAMES M. LEVINE VICE PRESIDENT NUCLEAR PRODUCTION "CORRECTED COPY" TO CORRECT LETTER NO.

102-02056-JML/TRB/DAJ July 29, 1991 Mr. John B. Martin, Regional Administrator U. S. Nuclear Regulatory Commission, Region.V 1450 Maria Lane, Sui.te 210 Walnut Creek, CA 94596-5368

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 1, 2,

and 3

Docket No.

STN 50-528 (License No. NPF-41)

Docket No, STN 50-529 (License No. NPF-51)

Docket No.

STN 50-530 (License No. NPF-74)

Response

to NRC Concern Regarding Reactor Coolant Strontium Measurements Inspection Report Nos.

50-528,

529, and 530/91-20 File'1-070-026 APS has evaluated the strontium measurement inconsistencies which arose during a confirmatory measurement inspection conducted December 3 through77, 1990, by Messrs W. Tenbrook and L. Coblentz.

These inconsistencies.

and attendant NRC concerns are discussed in Inspection Report 50-528, 529, 530/91-20ddated May 30, 1991.

APS has been evaluating the methods used for measuring.reactor coolant strontium levels and has been implementing improvements intlaboratory techniques which.have resulted in more consistent and accurate sanqHe.results.

APS has also evaluated the method used at PVNGS to analyze strontimn levels and determined that since strontium levels contribute very little to'.the overall levels of radioactive material permitted in the reactor coolant system and since improved performance in our analytical interlaboratory bEind comparison results has been noted, current PVNGS analytical practices provide acceptable results.

APS is, however, continuing to evaluate analytiical methods to determine if further practical improvements can be made.

Information concerning the results of our evaluation and a summaryoof the actions APS intends to take are provided as an attachment to this llutter.

9108300l36 9l5724 PDR ADOCK 0500052S 9

PDR p~l

Letter to Mr. Martin Page 2

102-02056-JML/TRB/DAJ July 29, 1991 If you have any quests.ons regarding this response, please contact Mr. J.

A.

Scott't (602) 393-3965.

Very truly yours, JML/TRB/DAJ/dmn Attachments CC:

V. F.

Conway D. H.

Coe A. H. Gutterman A. C. Gehr NRC Document Control Desk

Attachment, Page 1 of 3 102-02056-JML/TRB/DAJ July 29, 1991 ATTACHMENT EVA UATION Each unit's reactor coolant is analyzed twice a year for determination of the average disintegration energy (E-bar) of radioactive materials in the coolant in accordance with Technical Specification 3.4.7.

The levels of Strontium-89 and Strontium-90 are analyzed and used as an input to the determination of the value of E-bar.

The value of E-bar establishes the maximum permissible activity of the reactor coolant.

A recent, representative example of the contribution of Strontium-89 and Strontium-90 (Unit 2, February, 1991) to the value of E-bar shows that Strontium-89 contributed 0.003% and Strontium-90 contributed 0.0001% to the total E-bar value.

Therefore, the levels of Strontium do not appreciably contribute to the value of E-bar and thus the levels of activity permitted in the reactor coolant.

In early 1990, APS recognized the need to improve strontium analysis techniques and has been implementing improved laboratory controls to assure more consistent sample results.

In June

1991, APS conducted a set of internal splits and spikes using a June 1991 Unit 2 reactor coolant sample to evaluate improvement in the analytical methods.

The evaluation resulted in a 12%

variance about the mean for Strontium-89 measurements oyer nine separate analyses.

A mean value for Strontium-89 of 1.3 E-4 uCi/ml was obtained.

Since Unit 2 operated at essentially full power fro'm December 1990 to June

1991, the strontium levels would not be expected to changers APS compared the June 1991 results to the value obtained by the HRC in December 1990 (9.9 E-5

Attachment, Page 2 of 3 102-P2P56-JML/TRB/DAJ July 29, 1991 uCi/ml) and determined that they were consistent.

Also, the APS results are consistently conservative (biased high for their intended use in determining E-Bar) as demonstrated by periodic confirmatory

/

measurement blind samples.

APS analyzed the results of comparisons of interlaboratory blind samples for the previous six (6) quarters.

The results indicate that PVNGS is within the acceptance range for the blind samples approximately 918 of the time.

Concerning the validity of using the single separation technique versus the two separation method of determining the levels of Strontium, APS reviewed the article referenced in Inspection Report 50-528, 529, 530/91-20 (Bowman et-al Health Ph sics, V. 31, pp 495-500).

This article states that the single separation technique (method used at PVNGS), "yields acceptable relative error levels only when the Strontium-89 activity is close to twice the Strontium-90 activity."

Bowman further indicates that at a 5 to 1 ratio, the Strontium-89 uncertainty for the single separation technique approximates that of the two separation method.

PUNGS is currently operating with Strontium-89 activity levels of approximately 5 times higher than Strontium-90 (5 to 1 ratio)

~I therefore, the current Strontium-89 uncertainty is comparable to that achieved by the two separation method and is acceptable.

Greater uncertainty is experienced in the PVNGS method for current levels of Strontium-90 however APS considers that the uncertainty is acceptable consider consi ering its intended use.

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Attachment, Page 3 of 3 102 02056. -JML/TRB/DAJ July 29, 1991

decrease, reducing the uncertainty of Strontium-90 and increasing the uncertainty of Strontium-89.

PVNGS acknowledges that the uncertainty of determining the levels of Strontium-89 and Strontium-90 is dependent on the 1

ratio of the two nuclides and the analytical method used.

However, APS considers the level of uncertainty associated with. the single separation technique acceptable considering the inherent simplicity and advantages of the single separation technique (e.g.,

lower cost, transport of radioactive material) and the minimal contribution of Strontium to obtaining an accurate value for E-Bar.

CORRECTIVE ACTIONS While continuing to use the single separation technique, PVNGS will take the following actions to improve the consistency of results and attempt to resolve the high biased Strontium measurements.

A new calculation method for the single separation technique is being investigated by PVNGS to determine whether greater accuracy can be obtained.

The instruments used at PVNGS for chemical yield determination will be evaluated and, if feasible, improvements made to minimize chemical interferences present.

Dedicated Chemistry Department personnel specializing in performing strontium measurements wi,ll be responsible for performing strontium analysis.

These corrective. actions are expected to be completed by December 31,

1991, Following the completion of these corrective actions a split sample between APS and an independent laboratory will be performed to evaluate the effectiveness oE these, actions.

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B. Martin Page 2

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