05000272/LER-2015-005

LER-2015-005, Low Containment Spray Additive Tank Sodium Hydroxide Concentration

Salem Generating Station - Unit 1
Event date:	06-22-2015
Report date:	08-19-2015
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function
2722015005R00 - NRC Website

PLANT AND SYSTEM IDENTIFICATION

Westinghouse - Pressurized Water Reactor {PWR/4} Containment Spray System, Tank {BE!TK} Energy Industry Identification System (EllS) codes and component function identifier codes appear as {SS/CCC}.

IDENTIFICATION OF OCCURRENCE

Event Date: June 22, 2015 Discovery Date: June 22, 2015

CONDITIONS PRIOR TO OCCURRENCE

Salem Unit 1 was in operational Mode 1, operating at approximately 100 percent power. No additional structures, systems or components were inoperable at the time that contributed to this event.

DESCRIPTION OF OCCURRENCE

On June 22, 2015, at 1406, Salem Operations was notified by chemistry personnel that the Salem Unit 1 Containment Spray Additive Tank {BE!TK} Sodium Hydroxide (NaOH) concentration was 29.6 percent by weight. Unit 1 entered TS Action Statement 3.6.2.2.a for the Containment Spray Additive Tank being less than the required value of between 30 and 32 percent by weight of NaOH solution.

At 1521, additional sampling confirmed the Salem Unit 1 Containment Spray Additive Tank NaOH concentration to be 29.6 percent by weight.

At 2055 an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> NRC Emergency Notification System (ENS) report was made under the requirements of 10 CFR 50. 72(b)(3)(v)(C) and (D) for " Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to: ...

(C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident.

On June 23, 2015, at 1908, Salem Unit 1 exited TS 3.6.2.2.a when chemical addition and subsequent testing verified the Containment Spray Additive Tank contents to be 31.4 percent by weight of NaOH.

Subsequent analysis of past Containment Spray Additive Tank level versus estimated NaOH concentration 2. DOCKET 6. LERNUMBER

1. FACILITYNAME

0001, or by internet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

• ...

CONTINUATION SHEET

by weight indicated that the NaOH concentration in the tank had decreased below the TS required range of between 30 and 32 percent by weight value in January of 2015, exceeding the TS 3.6.2.2.a allowed outage time for inoperability of the Containment Spray Additive Tank of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

This report is made in accordance with 10 CFR 50. 73(a)(2)(i)(B) for "Any operation or condition which was prohibited by the plant's Technical Specifications ... " and 1 O CFR 50. 73(a)(2)(v) for "Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to: ... (C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident.

CAUSE OF EVENT

A review of control room logs indicates that a slow rise in Containment Spray Additive Tank level occurred over the course of several months. The last surveillance performed on November 11 , 2014 indicated a tank level of 79.4 percent with an NaOH concentration of 30.9 percent by weight. Subsequent surveillance testing performed on June 22, 2015 indicated a level increase to 81.5 percent and a corresponding NaOH concentration decrease to 29.6 percent by weight. Trending capability was not sufficient to identify this long-term trend.

SAFETY CONSEQUENCES AND IMPLICATIONS

This event did not result in any offsite release of radioactivity or increase of offsite dose rates, and there were no personnel injuries or damage to any other safety-related equipment.

The purpose of the Containment Spray System is to operate following a primary coolant system failure to reduce containment pressure in conjunction with the Containment Fan Cooler Units and to remove iodine from the containment atmosphere. The purpose of the Containment Spray Additive Tank is to provide a source of NaOH to the Containment Spray stream to enhance iodine removal capability during the initial phase of a primary coolant system failure and to minimize chloride induced stress corrosion cracking of stainless steel inside containment. If a large break loss of coolant accident were to occur, the concentration of NaOH in solution must be sufficient to raise the injection spray to a pH of at least 8.5, as specified in the Salem Updated Final Safety Analysis Report. Calculations assuming a 29.6% NaOH concentration by weight solution in the Containment Spray Additive Tank indicate that the resultant spray solution would have a pH of greater than 8.5 and thus would be capable of driving absorption of elemental iodine sufficiently to ensure the Containment Spray system was capable of performing its intended safety function.

SAFETY SYSTEM FUNCTIONAL FAILURE

Although the Containment Spray system was determined to be inoperable, it was capable of performing its intended safety function, thus this event does not constitute a Safety System Functional Failure (SSFF) as defined in Nuclear Energy Institute (NEI) 99-02, Regulatory Assessment Performance Indicator Guideline.

PREVIOUS OCCURRENCES

A review of Salem Unit 1 and 2 LERs for the previous three years identified no other similar events.

CORRECTIVE ACTIONS

1. Salem Chemistry department will develop and implement a method for long term trending of Containment Spray Additive Tank parameters.

2. Salem Operations department will develop and implement a method for long term trending of Containment Spray Additive Tank parameters.

3. Troubleshooting will be performed to identify the source of in-leakage to the Containment Spray Additive Tank.

COMMITMENTS

This LER contains no regulatory commitments.