ML18106A365

Forwards Summary of Util Evaluation of part-length Control Rod Drive Mechanism Housing Weld Crack of Prairie Island, Unit 2,which Is Relevant to Sgs.Util Intends to Take No Further Action Beyond Those Stated in Encl

ML18106A365
Person / Time
Site:	Salem
Issue date:	03/06/1998
From:	Bakken A Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LR-N980118, NUDOCS 9803170298
Download: ML18106A365 (5)

Text

e OPS~G Public Sr;'lrvice Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038-0236 Nuclear Business Unit LR --N980118 6

United States Nuclear Regulatory ComEcPn 1998 Document Control Desk Washington, DC 20555 Gentlemen:

PUBLIC SERVICE ELECTRIC AND GAS EVALUATION OF THE PART-LENGTH CONTROL ROD DRIVE MECHANISM HOUSING WELD CRACK OF THE PRAIRIE ISLAND UNIT 2 RELATIVE TO SALEM GENERATING STATION UNIT NOS. 1AND2 DOCKET NOS. 50-272 AND 50-311 As a result of the part length Control Rod Drive Mechanism (CROM) housing weld crack discovered at Northern States Power Company Prairie Island Unit 2, the Westinghouse Owners Group (WOG) activated the Regulatory Review Group (RRG) to address the generic implications and the Commission's (NRC) concerns relative to this issue. Public Service Electric and Gas Company's (PSE&G) is a member of the WOG and plans to actively participate and support the recommendations of the WOG RRG.

However, since both Salem Units are in the process of being restarted from I maintenance outages, PSE&G has performed an impact review of this issue relative to Salem Unit 1 and 2. This letter is being submitted to the NRC to document the result of this review, and PSE&G's conclusion that operating Salem Units 1 and 2 does not impose an undue risk to the health and safety of the public.

The result of our assessment is documented in Attachment 1 to this letter. Attachment 1 contains the actions taken and proposed by PSE&G relative to this issue. PSE&G intends to actively participate and support the long term recommendations of the WOG RRG; however, PSE&G intends to take no further action beyond those stated in Attachment 1 prior to the restart of the Salem Units.

Should you have any questions with regard to this transmittal, please do not hesitate to I contact us.  !

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/~::.. V\~11 J a Sincerely, A. C. Bakken, Ill 9803170298 980306 General Manager - Salem Operations PDR ADOCK 05000272 p PDR

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The power is in your hands.

95-2168 REV. 6/94

.. MARO 6 1998 Document Control Desk LR-NS80118' Attachment (1)

C Mr. Hubert J. Miller, Administrator - Region I U. S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Mr. P. Milano, Licensing Project Manager - Salem U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 14E21 Rockville, MD 20852 Ms. M. Evans - Salem (S09)

USNRC Senior Resident Inspector Mr. K. Tosch, Manager, IV NJ Department of Environmental Protection Division of Environmental Quality Bureau of Nuclear Engineering CN 415 Trenton, NJ 08625

Document Control Desk LR~N980~ 18 ATTACHMENT 1 PUBLIC SERVICE ELECTRIC AND GAS EVALUATION OF THE PART-LENGTH CONTROL ROD DRIVE MECHANISM HOUSING WELD CRACK OF THE PRAIRIE ISLAND UNIT 2 2 RELATIVE TO SALEM GENERATING STATION During the recent shutdown of the Northern States Power Company Prairie Island Unit 2, an active through wall leak in one of the part-length Control Rod Drive Mechanism (CROM) housing weld was identified. Subsequent destructive examination of the failure showed it to be caused by a weld flaw that existed since original construction. The flaw was driven through wall by a recent loading condition causing the active leak to occur. The Salem units have CROM housings and welds of similar design which are abandoned in place but remain part of the RCS pressure boundary.

The following paragraphs provide the actions taken by PSE&G to address the concerns of the part length CROM housing weld crack (CROM crack) identified at Prairie Island Unit 2 relative to the Salem Units and PSE&G's ability to safely operate the units. PSE&G is actively participating and will follow the guidance developed by the Westinghouse Owners Groups (WOG) in addressing this issue. However, it is PSE&G's conclusion that restarting Salem Units 1 and 2 from the current outage does not impose an undue risk to the health and safety of the public.

To provide the assurance needed to restart both Salem Units, PSE&G provides the following information relative to the actions taken to-date.

PSE&G's has a detailed Containment Inspection Procedure, which includes inspection of the reactor vessel head area. This procedure provides guidance to ensure a thorough containment inspection is performed. Utilizing this procedure, PSE&G performed a visual inspection of the Salem Unit 2 reactor vessel head penetrations. This inspection was performed through the CROM shroud doors, which had been previously installed on the CROM ventilation shroud to allow the reactor head penetration to be visually inspected. This inspection is normally performed while the unit is in Mode 3.

The inspection, which was performed with the reactor in Mode 5 did not reveal any indication of a previously active leak within the inspected area. Indication of leakage would have been detected by the presence of boron build-up, standing water or heaUhumidity within the CROM enclosure.

Document Control Desk LR.. N980i18 ATTACHMENT 1 PUBLIC SERVICE ELECTRIC AND GAS EVALUATION OF THE PART-LENGTH CONTROL ROD DRIVE MECHANISM HOUSING WELD CRACK OF THE PRAIRIE ISLAND UNIT 2 2 RELATIVE TO SALEM GENERATING STATION A similar inspection will be performed for Salem Units 1 and 2 at normal operating pressure and temperature (Mode 3) prior to restart.

PSE&G has a well establish program to detect leakage inside containment, including Pressure Boundary Leakage. Some of the applicable RCS leak detection systems employed at both Salem units are as follows:

• The containment atmospheric particulate radioactivity monitor, R 11 A -

continuous indication in the control room.

• The containment atmospheric gaseous radioactivity monitor, R12A -.

continuous indication in the control room

• The containment sump level monitoring system - monitored at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

• The RCS water inventory balance, monitored once every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> if plant conditions allow it, but never less often than once every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

In addition, Salem Units 1 and 2 also have a reactor head area leakage detection system. This system was installed in 1988 for Salem Units 1 and 2 as a result of the CROM canopy seal leaks. The system monitors the CROM ventilation shroud. The system, Main Coolant System Leakage Air Particulate Monitor (MCSLAPM) provides continuous indication (in CPM) in the control room and the Radiation Protection department trends the indication every four hours.

The MCSLAPM system is reliable and has a higher sensitivity than the R11A, thus is capable of detecting very small leakage. Although MCSLAPM is not safety related and at times it may be unavailable, MCSLAPM provides an additional and unique source of information to assess potential leakage within the reactor vessel head area. Presently, MCSLAPM is being returned to service in both Salem Units, and will be functional prior to entering Mode 1.

Document Control Desk LR'-N980*118 ATTACHMENT 1 PUBLIC SERVICE ELECTRIC AND GAS EVALUATION OF THE PART-LENGTH CONTROL ROD DRIVE MECHANISM HOUSING WELD CRACK OF THE PRAIRIE ISLAND UNIT 2 2 RELATIVE TO SALEM GENERATING STATION These systems, as stated above, are capable of detecting RCS leakage well below the allowed Technical Specification limits. In addition, licensed operators have been made aware of the Prairie Island CROM crack event, and increase attention is being given to trending of the containment particulate activity monitor (R11A) to once every four hours by Radiation Protection personnel. The Radiation Protection Department utilizes an approved procedure which governs the trending and evaluation of the radiation monitors noted above. The actions stipulated by this procedure guide plant personnel to evaluate the potential for RCS leakage based on the presence of an upward trend in either monitor.

Specifically, these actions include:

1. Increasing the frequency at which monitor readings are taken and evaluated (readings are taken every 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> versus every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />).

2. Verifying proper operation of the monitor(s) in question.

3. Recommending that the Operations Department initiate a containment building walkdown to identify the source of the leak.

Finally, as demonstrated by the analyses of the Prairie Island Unit 2 CROM crack, the crack does not show evidence of service growth and it was detected by leakage monitoring. However, in the unlikely event that a part length CROM were to suddenly rupture, this event is within the Design and Licensing Bases of the Salem Units, and is bounded by the Small Break LOCA Analysis. Licensed operators are trained and procedures are in placed to guide the operators through the necessary steps to mitigate the consequences of this event. Note that a part length CROM housing rupture imposes no reactivity transient (i.e.;

there is no control rod ejected from the reactor core), thus its effect is limited to the loss of reactor coolant inventory through the housing break.