ML19209A430

Forwards Response to IE Bulletin 79-17, Pipe Cracks in Stagnant Borated Water Sys at PWR Plants. Describes Test Results,Water Chemistry Controls & Preservice NDT

ML19209A430
Person / Time
Site:	Millstone
Issue date:	08/24/1979
From:	Counsil W NORTHEAST UTILITIES
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
NUDOCS 7910030850
Download: ML19209A430 (8)

Text

.

Tw NORTHI!AST IFFII.frit!S

] 2][.7.$ U $ SY Y ARTFORo CONNECTICUT 06101 g

5:lCO.D',,r

,,,,,o,

.sg ,

~~

(203) 666-6911 August 24, 1979 Docket No. 50-336 Mr. Boyce H. Grier, Director Region I Gffica of Inspection and Enforcement U. S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406

References:

(1) B. H. Grier letter to W. G. Counsil dated July 26, 1979 forwarding I&E Bulletin #79-17.

(2) U. G. Counsil letter to B. H. Grier dated February 26, 1979.

(3) D. C. Switzer letter to B. H. Grier dated February 28, 1978.

(4) D. C. Switzer letter to J. P. O'Rei'ly dated February 28, 1977.

(5) D. C. Switzer letter to J. P. O'Reilly dated December 28, 1976.

Gentlemen:

Millstone Nuclear Power Station , Unit No. 2 Pipe Cracks in Stagnant Borated Water Systems at PWR Plants I&E Bulletin Fo. 79-17, Reference (1), requested that Northeast Nuclear Energy Company (NNECO) conduct a review of safety-related stainless steel piping systems to identify systems and portions of systems which contain stagnant oxygenated borated water. In addition, the NRC Staff requested that NNECO provide specific intormation regarding these systems within 30 days of the date of the Bulletin. Accordingly, NNECO hereby provides the responses (Attachment 1), to Items 1(a) - 1(d) of Reference (1).

NNECO has performed a review of safety-related stainless steel piping to determine which systems contain stagnant oxygenated borated water. NNECO has defined any piping not flushed at least once per month as stagnant.

This definition is based on the following.

(1) no cracks were found in the high pressure injection lines at Three Mile Island, Unit No.1 (IMI-1) which were occasionally flushed; (2) this definition allows a large enough sample of weld to produce a statistically meaningful test; (3) che piping to be tested should contain the worst case welds as the fluid is motionless for the longest period of time.

1086 i30 7910o309s0 p

In addition, examinations will be limited to Type 304 stainless steel piping based upon the f act that cracks detected at TMI-1 were in Type 304 piping systems and testing performed under Contract by the Electric Power Research Institutc (EPRI) (CE Report NED0-21000) has shown Type 304 stainless steel te be far more atsceptible to intergranular stress corrosion cracking (IGSCC) than other typas such as Types 316, 316L, and 304L.

Based on the above, the following systems and portions of systems are considered to contain stagnant oxygenated borated water:

(1) Spent Fuel Paol Cooling -- dead legs only.

(2) Chemical and Volume Control System (CVCS) -- emergency boration lines and dead legs.

(3) Low Pressure Safety Injection (LPSI) anc Containment Spray -- lines downstream of the mini-flow recirculation connections.

NNECO wishes to note that the examination to verify system integrity outlined in Item 2(a) of the Bulletin has been defined as a visual examination at service pressure of normally accessible welds. Guidance for this visual examination of welds will be drawn from TWA-5240 which states that insulation will be removed only if evidence of leakage is found at a low point or under a pipe. This defini-tion was chosen as it more appropriately addresses the intent of the inspection.

The testing required by Item 2(b) of Reference (1) has already commenced with 100% of the liquid penetrant exams and 90% of the ultrasonic exams complete.

To date, no crack indications have been detected by either method. NNECO has concluded that these findings support interpretations of Items 1 and 2(a).

NNECO trusts that this information is responsive to NRC Staff requests and Concerns.

Very truly yours, NOR' HEAST NUCLEAR ENERGY COMPANY

'I / <n

l. :

pb?, b 6 '.

'i,a

<- is W. G. Counsil

, , Vice President Attachments 1086 131

DOCKET No. 50-336 ATTACHMENT 1 MILLSIONE NUCLEAR POWER STATION, UNIT NO. 2 I&E BULLETIN No. 79-17 RESPONSES TO ITEMS 1(a) - 1(d) 1086 102 AUGUST, 1979 T&bOOBOW *e ,

Question 1(a)

Provide the extent and dates of the hydrotests, visual and volumetric examina-tions performed per 10CFR50.55a(g) (Re: IE Circular 76-06 enclosed) of identified systems. Include a description of the non-destructive examination procedures, procedure qualifications and acceptance criteria, the sampling plan, results of the examinations, and any related corrective actions taken.

Response

NNECO has determined that no inservice inspection hydrostatic tests, visual surface, or volumetric examinations have been performed on the piping covered by Reference (1); however, limited sections of system piping have been subjected to load hydrostatic tests following repair work. Because of the limited scope of these tests, no attempt has been made to retrieve this information.

Question 1(b)

Provide a description of water chemistry controls, summary of chemistry data, any design changes and/or actions taken, such as periodic flushing of recircu-lation procedures to maintain required water chemistry with respect to pH, B, CL , F , 02

Response

NNECO has maintained a chemistry sampling monitoring program to assure the integrity of the safety-related piping containing boric acid, since August 30, 1975. Under this program, the piping in the safety injection system, containment spray system, which are not flushed at lease once per month, and two lines from the boric acid storage tanks in the CVCS were monitored. The maximum allowable chloride concentration in these systems is .15 ppm. The monitoring program and chemistry data through 1978 have been previously reported in References (2), (3),

(4), and (5) . This monitoring program was concluded in February,1979. An augmented Inservice Inspection Program, which includes the piping systems in the above-mentioned chemistry monitoring program, was implemented on April 26, 1979.

In addition to References (2), (3), (4), and (5), chemistry information pertaining to safety-related piping containing stagnant boric acid, with the exception of the shutdown cooling system (LPSI), was reported to the NRC Staf f in response to I&E Circular No. 79-06. The shutdown cooling system is operated during refueling outages. At this time, samples are taken to monitor reactor coolant chemistry. Chemistry data for the 1979 refueling outage is included in Attachment 2.

1086 i83

Question 1(c)

Describe the preservice NDE performed on the weld joints of identified systems. The description is to include the applicable ASME Code sections and supplements (addenda) that were followed, and the acceptance criterion.

Response

In response to Item 1(c), NNECO provides the following information on preservice non-destructive tests performed at Millstone Unit No. 2. 100% Radiographic testing was performed on all girth and longitudinal butt welds in piping with diameters greater than or equal to 2-1/2 inches on the following systems:

(1) Containment Spray Pump Discharge piping (2) LPSI Pump Discharge piping (3) Containment Sump Recirculation piping (4) High Pressure Safety Injection (HPSI) Pump Discharge piping a) Class 1 portion b) Class 2 portion (5) Cross ties between LPSI and containment spray and cross ties between the shutdown Cooling and HPSI systems (6) Connections from any of the identified systems to auxiliary systems (i.e. , radwaste system, purification system, etc. ) .

In addition to the radiographic testing, all butt welds in piping with a diameter greater than or equal to 2-1/2 inches in the Class 1 portion of the HPSI pump discharge piping were 100% liquid penetrant tested.

Shop fabrication acceptance criteria were based on ANSI B 31.7 - 1969.

Field fabriaction and erection acceptance criteria were based on ASME Section III

- 1971.

1086 184

Quastion 1(d)

Facilities having previously experienced cracking in identified systems, Item 1, are requested to identify (list) the new materials utilized in repair or replacement on a system-by-system basis. If a report of this information anci that requested above has been previously submitted to the NRC, please reference i.he specific report (s) in response to this Bulletin.

Response

To dat.e, NNECO has found no cracking in safety-related piping defined as containing stagnant oxygenated borated water.

1086 185

DOCKET No. 50-336 ATTACIDfENT 2 MILLSTONE NUCLEAR POWER STATION, UNIT NO. 2 1979 REFUELING OUTAGE CHDiISTRY DATA 1086 186 AUGUST, 1979

SHUTDOWN COOLING (REACTOR COOLANT) CHEMISTRY DATA Date pH Boron (opm) CL- (ppb) F- (ppb) 3/19/79 5.83 1516 30 100 3/26/79 5.52 2191 50 100 4/2/79 5.29 2128 50 100 4/9/79 4.78 2069 50 100 4/16/79 5.24 1961 50 100 4/23/79 4.82 1970 50 100 4/30/79 5.35 1986 50 100 5/7/79 4.80 2120 50 100 1086 187