ML19326B670

Provides Status Rept on Investigation of Leaks Noted in 741118 & 750205 Transmittal of AOs 50-313/74-11 & 50-313/74-11A,respectively.Results of Examinations to Be Available 60 Days After Final Sample Is Taken

ML19326B670
Person / Time
Site:	Arkansas Nuclear
Issue date:	04/11/1975
From:	Cavanaugh W ARKANSAS POWER & LIGHT CO.
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19326B653	List: ML19326B651 ML19326B658 ML19326B662 ML19326B664 ML19326B670 ML19326B676 ML19326B683 ML19326B687 ML19326B691 ML19326B694
References
4603, NUDOCS 8004170515
Download: ML19326B670 (3)

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rN . g H GL PIN G B UILO ARI<ANSAS

.ca ARK ANS AS POWER & LIGHT COMPANY STM & LOUISIANA STAEETS . LITTLE AOCK. A AK ANSAS 7 ~-

3 e k80 72 4311 j,

April 11, 1975 a D

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4 Mr. Norman C. Moseley, Director V Office of Inspection and Enforcement Region II.

230 Peachtree Street, N.W., Suite 818 --

Atlanta, Georgia 30303

Subject:

Arkansas Power 6 Light Company Arkansas Nuclear One-Unit 1 Docket No. 50-313 License No. DPR-51 Abnormal Occurrence No. 50-313/74-11

Dear Mr. Moseley:

U In letters dated November 18,.1974, and Februa y 5,1975, from Mr. J. D. -

Phillips to -Mr. E. G. Case, we submitted Abnormal Occurrence Reports Number 50-313/74-11 and 50-313/74-11A, respectively, involving leaks in the reactor building spray pump P35B suction line. The following is a status report of our continuing investigation of these leaks:

1. We are conducting a program of field investigation consisting 2 of the following:

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a. Examinat. ion of pipe surfaces in safety related systems for evidence of heavy surface etching. This will be accom-plished by visual observation (or replica method if neces-sary) and will ensure good statistical representation of ._

all effected piping.

b. A trepan sampling program consisting of 15 samples to cover ranges of carbon content, pipe diameter, wall thickness, '

and degree of surface etching. In pipe of 4" diameter or less a spool will be removed and replaced with T-304 pipe while in larger pipe the trepan plugs will be replaced with -

T-304L plugs. In order to demonstrate that the trepan pro-cedure will not in and of itself cause detrimental effects, a practice mn using this technique has been tried first on the crossconnect piping (before it was removed as noted in n

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TAX PAYING. INVESTOR OWNED MEMBER MIDOLE SOUTH UTILITIES SYSTEM COPY :EVf IEG10N

Mr. Norman C. Jeley

• April 11, 1975 U

my letter to Mr. A. Giambusso of March 25, 1975) and on a section of pipe which was not installed as a control check sample.

2. Laboratory metallographic analysis of the samples collected in

1. above will be conducted to determine the degree of pipe sensitization, n ese tests will be conducted in accordance with ASDI-A262-70 as recommended by Regulatory Guide 1.44.

3. Laboratory metallographic analysis will be conducted on selected field welds, shop welds, and all existing cracks in the cross-connect piping after it is removed as noted in my letter to Mr. A. Giambusso of March 25, 1975.

4. We intend to establish a program of periodic inservice inspec- _.

tion of Schedule 10S piping based on Regulatory Guide 1.51 and the Winter 1972 Addenda to the ASME Code,Section XI. This inspection program will involve radiographic examination and will be based on the results of the field investigations in item 1. above. In the interim, we will continue our visual surveillance each shift.

5. As sensitized stainless steel piping must have a corrodent pre-p '

sent to establish the conditions necessary for the cracks we have experienced, we have investigated possible sources of these '

g s corrodents. The , sodium thiosulfate storage tank is a source of -;

chlorides to the spray system piping and is separated from the piping by two normally closed motor operated valves. These i valves must be exercised quarterly pursuant to the Technical Specification requirements and during that exercising have probably introduced chlorides into the spray system piping.

We have checked these valves for leak tightness and have found no leakage.

The sodium chloride content in the tank.is limited to 40.3 wt'6 by administrative control on the purity of the sodium thiosulfate which is purchased. Bis limit was established by Babcock 6 Wilcox, who has indicated that this chloride content will not affect the stainless steel sodium thiosulfate storage tank at  :

the temperature and pressure conditions involved in storage. We believe the same to be true for the line from the tank to the motor operated valves as we believe this line was solution annealed and are including this line in the trepan sampling pro- -

gram to verify this.

In order to eliminate this source of corrodent, we intend to pro-

. pose a Technical Specification change to isolate the tank with the stop valve in the cocmon discharge line and flush the line I near the motor operated valves when these valves are exercised.

Stop check valves presently installed would be used to isolate i s

v) the line being flushed from the spray system piping during this surveillance operation.

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Mr. Norman C. 3eley April 11, 1975

6. To determ.i.ne the chloride content of the spray system piping and the sodium thiosulfate storage tank, we are evaluating a procedure, which we have in house, from Allied Chemical (our supplier of sodium thiosulfate). Kormal chemistry procedures cannot determine the chloride content in the presence of high concentrations of sodium thiosulfate and boric acid. hhen the procedure or a similar one is proven as to its accuracy, we intend to impicment a weekly sampling program and to flush the effected piping when high chloride concentrations are found.

, 7. Due to the low pressure and temperature conditions in the effect-ed piping system, we feel that no catastrophic failure of the system can occur as a result of the type of cracking we have experienced. h'e believe this to be true because cracks such as these are scif-relieving in nature and therefore will not cause ~

catastrophic failure of the piping system.

The results of the examination programs, in items 1 through 3 above will be available in about sixty days after the final sample is taken. We will provide a followup report at that time.

Vsry truly yours, y/. .

d h William Cavanaugh III Manager, Nuclear Serv es 1

l WC:lt 1 cc: Mr. E. Morris Howard, Director Office of Inspection and Enforcement .

P.egion IV U. S. Nuclear Regulatory Commission P. O. Box 5039 .

. 5 White Settlement, Texas 76108 2

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