ML12107A471
| ML12107A471 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 12/13/2011 |
| From: | Twomey J Energy Northwest |
| To: | Cunanan A Division of License Renewal |
| References | |
| Download: ML12107A471 (6) | |
Text
1 NRR-PMDAPEm Resource From:
Twomey, John D. [JDTWOMEY@energy-northwest.com]
Sent:
Tuesday, December 13, 2011 1:33 PM To:
Cunanan, Arthur Cc:
Gregoire, Donald W.; Mostala, Abbas A.; Worthington, Janet H.; Person, Jefferson T.
Subject:
Responses to ACRS Subcommittee Attachments:
image001.png Arthur Following are Energy Northwests responses to questions from the ACRS subcommittee members that required additional information for closure. Note that Energy Northwest is only responding to the first six (6) of the eight (8) questions as provided by you via e-mail on 11/08/11. The last two questions appeared to be directed to the NRR/NRC staff. Therefore, Energy Northwest did not provide a response to those questions.
However, if you need information from Energy Northwest to close out those questions or need any additional information or actions from Energy Northwest regarding the questions below please feel free to contact me.
Thank you.
- 1. Pages 41-42: Siebert request whether applicant has had any evidence of MIC in their systems. Applicant promised to answer.
Energy Northwest response:
Energy Northwest recognizes that microbiologically influenced corrosion (MIC) is present to some degree in all water systems. Columbia manages the impact of MIC to protect the integrity of plant piping systems. The monitoring program at Columbia consists of three separate components: bulk water, biofilm, and deposits. The program used is in agreement with the EPRI guidelines on MIC monitoring and monitoring of open and closed cooling systems. Monitoring of differing types is conducted based on the history and quality of the water chemistry in each system. Sampling and analysis of deposits and bulk water provides results that produce a MIC index number. This number is a numeric value corresponding one of three categories: MIC highly likely, MIC concern moderate, MIC not likely. The index provides a method of assessing water-based systems for the potential for MIC development by utilizing data obtained from standard monitoring/inspection procedures.
For determining the MIC index the Environmental service group monitors for the following:
SRB SR (SULFATE REDUCING )
SLIME PRODUCERS (CENTRIMIDE-CA)
ACID PRODUCERS (CLOSTRIDIUM-RCM)
METAL OXIDIZING BACTERIA (GALLIONELLA-MOB)
TOTAL ANAEROBIC BACTERIA (THIOGYCOLLATE-TGM)
TOTAL AEROBIC BACTERIA ATP (Adenosine Triphosphate)
System Experience TSW-Plant Turbine Service Water - MIC has been identified in this system; however, predominant cause of pipe leakage is from under deposit pitting. SRB is active in this system and has contributed to corrosion. Treatment of this system is more difficult in that it has a larger percentage of untreated river water as a source.
CW-Circulating Water - MIC is not likely in this system. This system is treated and maintained to minimize corrosion. No corrosion failures to date have been attributed to MIC.
SW-Plant Essential Service Water - The use of a peroxide treatment has controlled the biological activity in the SW system. ATP is monitored as indication of any microbes present in the bulk water.
One piping leak on a socket weld in 1995 was attributed to a MIC/ crevice corrosion. This system has experienced very few leaks and no other piping leaks have been attributed to MIC.
2 FP-Fire protection - MIC is present in some of the isolated portions of the system; however, no MIC related failures have occurred. Sections of the system that have no flow are managed through periodic flushing with treated water
- 2. Page 43, et al: any metal-enclosed busses, are any in scope (a2-a1) as a result of the MEB catastrophic failure of 2009? (Stetkar) The 2009 event caused external effects, from the molten bus metal/plasma that showered nearby components. Where is this bus (these busses) located relative to surrounding components, whether electrical or cables, or sensors or instrumentation? Atkinson promised to get back to the subcomm. (page 45).
Page 92, 93, what does fail safe wrt cables mean, in regards to faulted MEB buswork. Page 99. Page 100 after the break, 101,
- a. Back on the bus duct failure. Stetkar, page 146. Dont understand the word Fail-safe so he dismisses that term. Can you have failures of those cables, sensors, etc., from an MEB catastrophic failure, such that a (safety) signal does not go into the protection logic? This is not fail-safe, not cut the cable and have an open circuit, not design basis of the transmitter. It is can you have a failure of that cable that gives you a false high [non-fail-safe level, jd] thereby disabling part of the MSIV [or other safety-related function] closure signal [safety function]? Stetkar also referred to RAI 2.1-1a and the response.
- b. Applicant (Atkinson) promised to get back to Subcomm. Arthur acknowledged this takeaway also. (page 148). Also applicant acknowledged again on page 152.
Energy Northwest response:
Please refer to GO2-10-095 response to RAI 2.1-1(A) for detailed explanation.
The "fail-safe" design features of turbine throttle and governor valve closure signals to the Reactor Protection System (RPS) are discussed below.
- a. Shorts to ground: Each trip function input circuit to the RPS is individually fused to prevent degradation of other channels if a short to ground occurs on one channel. This protection also applies to the turbine throttle and governor valve closure trip inputs to the RPS. Therefore, a short to ground would be interrupted by the protective fuses eliminating any interaction or degradation of other channels, as well as resulting in a channel trip due to "fail-safe" logic.
- b. Opens: The normal operating state of the RPS trip inputs is a closed contact condition. Therefore, an open in an RPS input channel circuit would result in failure in the safe direction causing a trip of that channel with no degradation or interaction with other channels.
- c. Hot shorts: Reactor protection system cabling that is routed from trip instrumentation through the Turbine Generator Building is enclosed in conduit. Each trip channel has a separate and dedicated conduit. Therefore, hot shorts would be confined to one channel of trip instrumentation and would not degrade or interact with other protective channels.
- d. Short between signal conductors (mimic closed contact): Other diverse variables (reactor pressure and neutron flux trips) may be relied on for reactor scram if components in the Turbine Generator Building fail.
The cables and instruments for turbine throttle and governor valve closure signals to the Reactor Protection System (RPS) are not routed near the non-segregated metal enclosed buses and have a structural wall located between the buses and the cables.
All other components identified as safety related in the plant database, whether electrical cables, or sensors or instrumentation, located in the Turbine building are classified as safety related because of an NRC commitment but they do not perform a 10 CFR 54.4(a)(1) function.
Therefore, there are no failures of non-safety related structures or components in the Turbine building that could prevent a 10 CFR 54.4(a)(1) function.
- 3. Pages 47-48: Committee asked what are the applicants plans to replace Copper from their systems, long-term.
Applicant promised to get back to ACRS on this.
Energy Northwest response:
This question came as the result of a discussion between Columbia and the ACRS subcommittee regarding replacement of the main condenser to eliminate copper in the reactor water. The subcommittee asked if there were other sources of copper in the reactor water system (presumably seeking out potential sources that would inhibit hydrogen water chemistry mitigation). Since the replacement of the main condenser, reactor water copper
3 levels have decreased to within the EPRI guidelines. There are currently no challenges to maintaining these copper levels and thus no long range plans for copper replacement actions.
Figure 1 Columbia's reactor feedwater copper levels since start-up from R20. The trend shows a decrease in levels as copper is removed from the system by the reactor water clean-up system. The levels are well below the EPRI Action Level of 0.2 parts per billion (ppb).
- 4. Page 102, why isnt the TSW supply piping to the RCC system considered in scope? (Stetkar). RCC cools the SFP system, also the containment cooling and recirc pump seal cooling Energy Northwest response:
The piping and components from the plant service water (TSW) pumps TSW-P-1A/1B to where it enters the reactor building are not in scope of license renewal. The TSW system does not perform any safety-related system intended functions that satisfy the scoping criteria of 10 CFR 54.4(a)(1). The TSW system does not contain any non-safety related components that perform a 10 CFR 54.4(a)(1) function. The TSW system does, however, contain non-safety related components that are attached to or located near safety-related structures, systems, or components (SSCs) whose failure creates a potential for spatial interaction that could prevent the satisfactory accomplishment of one or more of the functions identified in 10 CFR 54.4(a)(1). Therefore, the TSW system meets the scoping criterion of 10 CFR 54.4(a)(2) to maintain structural integrity. The TSW system is not relied upon to demonstrate compliance with the 10 CFR 54.4(a)(3) scoping criteria for any regulated events. The TSW piping and components are in the scope of license renewal from where the piping enters the reactor building to the reactor closed cooling water (RCC) system for structural integrity.
RCC provides cooling to the following equipment:
Reactor recirculation pumps, Drywell fan unit cooling coils, Drywell equipment drain condenser, Reactor water cleanup (RWCU) non-regenerative heat exchangers, Reactor building equipment drain heat exchanger, Control rod drive pumps, Fuel pool heat exchangers, RWCU recirculating pumps, and Offgas glycol refrigeration machines.
The safety related functions of the RCC System are:
Provides Primary Containment isolation and integrity Provides secondary containment isolation and integrity Fuel Pool Cooling (FPC) heat exchangers and piping for backup cooling from the Standby Service Water (SW) System Boundary valve RCC-V-129 based on an NRC commitment
4 Therefore other than the FPC heat exchangers, none of the components cooled by the RCC perform a safety related cooling function. The credited safety related cooling water source to the FPC heat exchangers is SW.
- 5. Page 19, the water lines from the screenhouse to the plant site, are they in scope or not? (Sieber)
Energy Northwest response:
The pipe lines from the screenhouse (pumphouse) from the river to the plant are in scope of license renewal.
This piping is designated as Tower Makeup (TMU) system and is addressed under the Buried Piping and Tanks Inspection Program. See LRA sections 2.3.3.46 and 3.3.2.1.43 and LRA table 3.3.2-43, line item 18 which calls out steel piping exposed to an environment of soil with the credited aging management program of Buried Piping and Tanks Inspection.
- 6. Page 120, Gavula-Stetkar, staff lookup on whether applicant does internal inspections on standby service water or on FP system, buried portions. To include all the raw water systems, the buried portions. Stetkar mentions SER 3.0.3.2.3. Kichline says FP allows for internal inspections. Question was, however, do they DO them?
Cunanan states we have it marked to get back to you on that. (p. 123)
Energy Northwest response:
The following information explains the internal inspections in our raw water piping systems:
Columbia has not committed to doing any internal inspections of the buried portions of in-scope systems.
However, as there is nothing unique about the internal environments of the buried portions of systems, compared to the aboveground portions of these same systems, the results of internal inspections of the aboveground portions are representative of the buried portions.
The following systems include raw water buried piping and piping components:
Fire Protection System (FP)
Standby Service Water System (SW)
Tower Makeup Water System (TMU)
The following aging management programs manage aging effects for these systems, and include nondestructive examination techniques, including visual inspections to detect loss of material on internal piping surfaces (i.e.,
wall thinning):
Fire Water Program [FP] - includes UT thickness measurements and opportunistic visual inspections of water-filled suppression piping that does not normally experience flow (stagnant or low-flow).
Open Cycle Cooling Water Program [SW, TMU] - includes UT and visual inspections (examination methods are chosen for any particular inspection activity based in part on the results of previous inspections). In addition, uniform corrosion is monitored by coupons in the SW System, and all heat exchangers served by SW are UTd on a two-year frequency and trended to give a measure of the corrosion rate.
John D. Twomey Project Manager License Renewal Project Energy Northwest 509-377-4678 jdtwomey@energy-northwest.com Please consider the environment before printing this email
Hearing Identifier:
NRR_PMDA Email Number:
333 Mail Envelope Properties (6B3A36947BB37F4CB09BF384F5E8BA4D3ECBCB06)
Subject:
Responses to ACRS Subcommittee Sent Date:
12/13/2011 1:32:35 PM Received Date:
12/13/2011 1:32:42 PM From:
Twomey, John D.
Created By:
JDTWOMEY@energy-northwest.com Recipients:
"Gregoire, Donald W." <dwgregoire@energy-northwest.com>
Tracking Status: None "Mostala, Abbas A." <AAMOSTALA@energy-northwest.com>
Tracking Status: None "Worthington, Janet H." <JHWORTHINGTON@energy-northwest.com>
Tracking Status: None "Person, Jefferson T." <JTPERSON@energy-northwest.com>
Tracking Status: None "Cunanan, Arthur" <Arthur.Cunanan@nrc.gov>
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