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# | {{Adams | ||
| number = ML091760204 | |||
| issue date = 06/18/2009 | |||
| title = License Amendment Request, Technical Specification Changes to Relocate Pressurizer Heater Requirements to Technical Requirements Manual | |||
| author name = Walsh K | |||
| author affiliation = Entergy Operations, Inc | |||
| addressee name = | |||
| addressee affiliation = NRC/Document Control Desk, NRC/NRR | |||
| docket = 05000368 | |||
| license number = NPF-006 | |||
| contact person = | |||
| case reference number = 2CAN060903 | |||
| document type = Letter, Technical Specification, Bases Change | |||
| page count = 13 | |||
| project = | |||
| stage = Other | |||
}} | |||
=Text= | |||
{{#Wiki_filter:2CAN060903 | |||
June 18, 2009 | |||
U.S. Nuclear Regulatory Commission | |||
Attn: Document Control Desk | |||
Washington, DC 20555 | |||
==SUBJECT:== | |||
License Amendment Request Technical Specification Changes To Relocate Pressurizer Heater | |||
Requirements to TRM | |||
Arkansas Nuclear One, Unit 2 | |||
Docket No. 50-368 | |||
License No. NPF-6 | |||
==Dear Sir or Madam:== | |||
Pursuant to 10 CFR 50.90, Entergy Operations, Inc. (Entergy) hereby requests the following | |||
amendment for Arkansas Nuclear One, Unit 2 (ANO-2). The proposed change will relocate | |||
portions of Technical Specification (TS) 3.4.4, Pressurizer , to the Technical Requirements Manual (TRM). TS 3.4.4 specifies operability requirements for both the water volume in the | |||
Pressurizer and the electric heater capacity of the Pressurizer. The proposed change will | |||
relocate the heater requirements to the TRM. | |||
The heater bank and capacity requirements for the Pressurizer are not credited in the accident | |||
analyses and, therefore, are proposed for relocation to the station TRM. This is consistent | |||
with the intent of 10 CFR 50.36 in that the heaters do not meet the requirements for inclusion | |||
in the TSs. Changes to the TRM are controlled in accordance with the requirements of 10 | |||
CFR 50.59. The associated TS Bases, controlled in accordance with the TS Bases Control | |||
Program of TS 6.5.14, will also be relocated to the TRM. The relocation of the TS Bases is | |||
part of the ANO TS change implementation process; therefore, a markup of the TS Bases is | |||
not provided in this submittal. | |||
In addition to the above, the percent-level described in TS 3.4.4 is relocated to the TS Bases. | |||
This "equivalent" to the 910 ft 3 limit contained in the TS can change over time due to changes in instrument uncertainty calculations or due to instrument replacement. Because the accident | |||
analysis is based on the volume limit, relocating the "percent" indication to the TS Bases does | |||
not result in a change to license basis or the actual TS limit. | |||
The proposed change has been evaluated in accordance with 10 CFR 50.91(a)(1) using | |||
criteria in 10 CFR 50.92(c) and it has been determined that the changes involve no significant | |||
hazards consideration. The bases for these determinations are included in the attached | |||
submittal. Entergy Operations, Inc. | |||
1448 S.R. 333 Russellville, AR 72802 | |||
Tel 479-858-3110 Kevin T. Walsh Vice President, Operations A rkansas Nuclear One | |||
2CAN060903 Page 2 of 2 | |||
The proposed change does not include any new commitments. | |||
Although this request is neither exigent nor emergency, your prompt review is requested. | |||
Once approved, the amendment sha ll be implemented within 90 days. | |||
If you have any questions or require additional information, please contact David Bice at | |||
479-858-5338. | |||
I declare under penalty of perjury that the foregoing is true and correct. Executed on | |||
June 18, 2009. | |||
Sincerely, Brad Berryman for Kevin Walsh KTW/dbb | |||
Attachments: | |||
: 1. Analysis of Proposed Technical Specification Change | |||
: 2. Proposed Technical Specification Changes (mark-up) | |||
cc: Mr. Elmo E. Collins Regional Administrator U. S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 | |||
NRC Senior Resident Inspector Arkansas Nuclear One P. O. Box 310 | |||
London, AR 72847 U. S. Nuclear Regulatory Commission | |||
Attn: Mr. Kaly Kalyanam | |||
MS O-8 B1 | |||
One White Flint North | |||
11555 Rockville Pike | |||
Rockville, MD 20852 Mr. Bernard R. Bevill | |||
Arkansas Department of Health | |||
Radiation Control Section | |||
4815 West Markham Street Slot #30 Little Rock, AR 72205 Attachment 1 2CAN060903 Analysis of Proposed Technical Specification Change Attachment to 2CAN060903 | |||
Page 1 of 8 | |||
==1.0 DESCRIPTION== | |||
This letter is a request to amend Operating License NPF-6 for Arkansas Nuclear One, Unit 2 (ANO-2). | |||
The proposed change will relocate portions of Technical Specification (TS) 3.4.4, Pressurizer , to the ANO-2 Technical Requirements Manual (TRM). This TS specifies operability | |||
requirements for both the water volume in the Pressurizer and the electric heater capacity of | |||
the Pressurizer. The proposed change will relocate the heater requirements to the TRM. | |||
Changes to the TRM are controlled in accordance with 10 CFR 50.59. | |||
In addition to the above, the percent-level described in TS 3.4.4 is relocated to the TS Bases. | |||
Because the safety analysis is based on the volume limit, relocating the "percent" indication to | |||
the TS Bases does not result in a change to license basis or the actual TS limit. | |||
==2.0 PROPOSED CHANGE== | |||
The electric heater portion of ANO-2 TS 3.4.4, Pressurizer , is proposed for relocation to the ANO-2 TRM. During relocation, the current TS Actions may be modified. Such modification, if performed, will be in accordance with the requirements of 10 CFR 50.59. A markup of the | |||
affected TS page is included in Attachment 2 of this submittal. | |||
In addition to the above, the percent-level described in TS 3.4.4 is relocated to the TS Bases. | |||
This "equivalent" to the 910 ft 3 limit contained in the TS can change over time due to changes in instrument uncertainty calculations or due to instrument replacement. Because the | |||
accident analysis is based on the volume limit, relocating the "percent" indication to the | |||
TS Bases does not result in a change to license basis or the actual TS limit. | |||
==3.0 BACKGROUND== | |||
TS 3.4.4 requires two proportional heater banks to be operable in Modes 1, 2, and 3 with a | |||
capacity of 150 Kilowatts (kW) each. These heater banks are powered from vital AC buses backed by a respective TS-required Emergency Diesel Generator (EDG). In addition to the | |||
two proportional heater banks, non-vital back-up heater banks are also installed to help | |||
accommodate significant transients during normal power operation. | |||
The pressure in the Reactor Coolant System (RCS) is controlled by regulating the | |||
temperature of the coolant in the Pressurizer, where steam and water are held in thermal | |||
equilibrium. Steam is formed by the Pressu rizer heaters or condensed by the Pressurizer spray to reduce variations caused by expansion and contraction of the reactor coolant due to | |||
system temperature changes. | |||
The Pressurizer heaters are single unit, direct immersion heaters which protrude vertically | |||
into the Pressurizer through sleeves welded in the lower head. Approximately one-third of the | |||
heaters are connected to proportional controllers which adjust the heat input as required to | |||
compensate for steady state losses and to maintain the desired steam pressure in the | |||
Pressurizer. The remaining backup heaters are connected to on-off controllers. These | |||
heaters are normally de-energized, but will automatically energize on a low Pressurizer Attachment to 2CAN060903 | |||
Page 2 of 8 | |||
pressure signal or high level error signal. This latter feature is provided since load increases result in an in-surge of relatively cold coolant into the Pressurizer, thereby decreasing the bulk | |||
water temperature. The Chemical and Volume Cont rol System (CVCS) acts to restore level, resulting in a transient pressure below normal operating pressure. To minimize the extent of | |||
this transient, the backup heaters are energized, contributing more heat to the water. A low- | |||
low Pressurizer level signal de-energizes all heaters to protect the heaters should they | |||
uncover. | |||
The Pressurizer proportional heater feeders are furnished with power (watt) transducers | |||
providing an analog value of the circuit power to the Safety Parameter Display System (SPDS). The magnitude of the power indicates the operational status and integrity of the | |||
heater bank. | |||
The 150 kW of Pressurizer heater capacity powered from an assured power source will | |||
ensure that RCS subcooling margin will be maintained 20 °F for a period of 45 hours following loss of off-site power. This time period includes a period of one-half hour at the | |||
beginning of the transient in which the heaters are unavailable. | |||
This calculation is conservative in that the actual heat losses would decrease during the | |||
transient as RCS pressure and temperature decreases, thereby prolonging the time to reach | |||
20 °F margin-to-saturation. | |||
The TS limit on Pressurizer volume exists to ensure the system is not operated under water- | |||
solid conditions. Such operation would preclude appropriate pressure control and could | |||
challenge the RCS pressure boundary. The percent-level indication provided in the TS was | |||
intended only as an operator aid and is not used in the accident analysis. This operator aid | |||
can change over time due to instrument replacem ent or calculation adjustment of instrument uncertainty. Therefore, it is proposed that this operator aid be relocated to the TS Bases. | |||
The Pressurizer is discussed throughout the ANO-2 Safety Analysis Report (SAR), including | |||
Sections 5.5.10 and 7.7.1.1.2 (Reference 1). Note that the Pressurizer heaters are not | |||
discussed in SAR Chapter 15, Accident Analysis , nor credited in the accident analysis, except to state their loss on low Pressurizer level in Table 15.1.18-2. | |||
Natural Circulation | |||
Accident analyses presented in the SAR do not take credit for Pressurizer heater operation; | |||
however, an implicit initial condition assumption of the safety analyses is that the RCS is | |||
operating at normal pressure. | |||
Although the heaters are not specifically used in accident analysis, the desire to maintain | |||
subcooled margin over the long term during a loss of offsite power, as indicated in | |||
NUREG 0737, Clarification of TMI Action Plan Requirements (Reference 2), is the reason for their original inclusion in the TSs. The requirement for emergency power supplies is also | |||
based on NUREG 0737. The intent is to keep the reactor coolant in a subcooled condition | |||
with natural circulation cooling at hot, high pressure conditions for an undefined, but extended | |||
time period after a loss of offsite power. While loss of offsite power is a coincident occurrence | |||
assumed in the accident analyses, maintaining hot, high pressure conditions over an | |||
extended time period is not evaluated in the accident analyses. | |||
Attachment to 2CAN060903 | |||
Page 3 of 8 | |||
Following the accident at Three Mile Island in 1979, NUREG 0737 was developed by the NRC to address a wide array of needed safety enhancements at commercial nuclear power | |||
plants. As mentioned above, the Pressurizer heaters were included in NUREG 0737 to | |||
support natural circulation (i.e., loss of forced flow) conditions following a loss of off-site | |||
power. Reactor coolant pumps are lost when off-site power is lost and the RCS begins to | |||
transition to natural circulation as the hot water from the reactor core rises through the RCS | |||
hot leg piping to the Steam Generators (SGs) where it is cooled as it passes through the SG | |||
tubes and descends back through the RCS cold leg piping to the bottom of the core where it | |||
again absorbs heat from the core as it rises through the fuel region. This natural convection | |||
flow continues as long as a minimum water level is maintained in the SGs and | |||
thermohydraulic communication is maintained throughout the RCS hot and cold leg piping. | |||
Following the TMI accident, it was believed that a plant cooldown via natural circulation could | |||
result in a steam bubble being formed in the reactor vessel head region. This is because the | |||
head region is a low or stagnant flow area of the vessel and would not be readily cooled by | |||
natural circulation flow. A slow cooldown would permit time for ambient heat losses from the | |||
reactor vessel head to afford necessary head-area cooling to inhibit steam bubble formation. | |||
However, a more rapid cooldown may not permit sufficient time for adequate vessel head | |||
cooldown and subsequently, formation of a steam bubble in the head region may occur. If | |||
this postulated condition were to continue uninhibited, it was thought the bubble could | |||
increase in size until it entered the hot leg piping, creating an adverse impact on the | |||
thermohydraulic communication needed to maintain natural circulation flow. Therefore, Pressurizer heaters were adopted as a means of increasing the RCS pressure to either | |||
maintain adequate subcooled margin with respect to vessel head conditions during natural | |||
circulation cooldown or to collapse any steam bubble in the vessel head should one develop. | |||
Benefit of Proposed Change | |||
On several occasions since initial startup, ANO-2 has experienced conditions where a | |||
proportional heater bank was found to narrowly meet the 150 kW TS requirement or found to | |||
have a capacity slightly below the TS requiremen | |||
: t. Such conditions could prevent unit startup if discovered during a plant outage or could result in an unnecessary plant shutdown if | |||
discovered in Mode 1, 2, or 3. In addition, since the TS requirement for the proportional | |||
heaters is based on natural circulation cooldown support and therefore, a loss of offsite power | |||
event, the heater bank must be declared inoperable anytime its respective emergency power | |||
supply is removed for maintenance (i.e., the respective EDG or necessary | |||
switchgear/breakers). These conditions place an undue hardship on the plant and plant | |||
personnel in requiring significant prompt action or plant shutdown for an inoperable | |||
component that is not credited in the safety analysis and is not the only means of ensuring | |||
safe plant cooldown using the natural circulation method. Therefore, Entergy requests these | |||
non-credited heater bank requirements be relocated from the TSs to the TRM. | |||
Because heaters provide necessary pressure control during power operation and can be an | |||
effective tool in supporting natural circulation cooldown, Entergy will continue to maintain | |||
appropriate functionality of the heater banks. Any future changes to the TRM heater | |||
requirements will be controlled in accordance with 10 CFR 50.59. | |||
Attachment to 2CAN060903 | |||
Page 4 of 8 | |||
==4.0 TECHNICAL ANALYSIS== | |||
TS 3.4.4 requires two groups of Pressurizer heaters, each with a capacity 150 kW and capable of being powered from an emergency power supply. The minimum heater capacity | |||
required is sufficient to maintain the RCS near normal operating pressure when accounting | |||
for heat losses through the Pressurizer insulation. By maintaining the pressure near normal | |||
operating conditions, a substantial subcooling margin can be maintained in the RCS loops | |||
during a natural circulation cooldown. The amount of heater capacity needed to maintain | |||
pressure is dependent on the ambient heat losses (see background information in preceding | |||
section). | |||
As discussed in the Background section above, the post-TMI concern was the formation of a | |||
steam bubble in the reactor vessel head region during natural circulation cooldown of the | |||
plant. However, experience gained since the 1979 TMI accident indicates that there are other | |||
means of controlling head bubble formation and growth. | |||
Note that the following discussions assume a natural circulation cooldown is required without | |||
a loss of RCS inventory that would result in loss of thermohydraulic communication in the RCS. Natural circulation cooldown is not relevant to such scenarios since the injection of | |||
borated water via high and/or low pressure safety injection pumps will be required to maintain | |||
inventory and support the necessary cooldown of the reactor core. | |||
The most significant bubble prevention method is to control the rate of natural circulation | |||
cooldown while monitoring reactor vessel head temperatures. Besides Pressurizer heaters, NUREG 0737 also required a means of monitoring reactor vessel head temperature and | |||
reactor vessel reactor coolant level. ANO-2 has multiple Core Exit Thermocouples (CETs) for | |||
use in monitoring temperature in the upper regions of the reactor vessel. At least 2 CETs are | |||
required per core quadrant in accordance with TS 3.3.3.6, Post-Accident Instrumentation , in Modes 1, 2, and 3. ANO-2 also has a Reacto r Vessel Level Monitoring System (RVLMS) that will indicate when steam bubble formation begins and monitor bubble growth during natural | |||
circulation conditions. Two channels of RVLMS are required to be operable in accordance | |||
with TS 3.3.3.6. The Plant Monitoring System (PMS) and SPDS computer also provide real-time display of RCS pressure-temperature relationships to plant operators for monitoring | |||
subcooled margin, the rate of cooldown, and the driving force effectiveness (core delta- | |||
temperature), among other things. Operations procedures contain in-depth discussion and | |||
guidance with regard to head bubble formation, prevention, and mitigation during natural | |||
circulation cooldown conditions. In the years since the TMI accident, operators have | |||
continuously practiced plant cooldowns under natural circulation conditions using plant simulators. Based on current plant capabilities and extensive operator knowledge and | |||
experience, the uncontrolled formation and growth of a steam bubble in the reactor vessel | |||
head is extremely unlikely. | |||
In addition to the above, RCS pressure can be increased by normal inventory makeup | |||
sources. RCS level slowly decreases as the RCS temperature is lowered during the | |||
cooldown. A charging pump or high pressure injection pump is used at ANO-2 to makeup for | |||
this "shrink" in RCS level due to density changes. However, level can be raised in the | |||
Pressurizer beyond that needed to account for the density changes which will result in an | |||
additional increase in RCS pressure. This method of pressure control is proceduralized and | |||
well understood by plant operators. | |||
Attachment to 2CAN060903 | |||
Page 5 of 8 | |||
Notwithstanding the above, if a bubble were to form and grow to the point of reaching the top of the vessel flow region, the cooler temperature of the water in the flow region would | |||
immediately collapse the steam attempting to enter the hot leg. This is enhanced by the fact | |||
that natural circulation flow is relatively low and the transport time from the reactor vessel to | |||
the SG does not permit rapid entrainment of steam that could reach the top of the SG tubes | |||
and inhibit natural circulation flow. Therefore, even in the event the natural circulation | |||
cooldown is not as controlled as desired, the steam bubble should not be capable of | |||
preventing natural circulation flow. To project the improbable and assume that steam is | |||
transported from the upper region of the vessel to the top of the steam generator tubes and | |||
interrupt thermohydraulic communication, the coolant would then enter a state of reflux boiling | |||
where the hot water travels through the hot leg and up one side of the SG tubes, cools, and | |||
returns through the lower portion of the hot leg back into the reactor vessel. This is a well | |||
defined phenomenon that is discussed in Combustion Engineering (CE) topical CEN-114-P, Amendment 1-P (Reference 3). In summary, the ov erriding safety function of core cooling is maintained regardless of the methods used, or not used, to control a natural circulation | |||
cooldown. | |||
If core cooling could be lost due to bubble formation in the reactor vessel head, procedures | |||
provide for re-establishment of core cooling by either collapsing the bubble or depressurize | |||
the RCS to permit high pressure safety injection. With regard to the former and as discussed | |||
above, Pressurizer heaters are not required for bubble collapse, but can be used to support | |||
bubble collapse if available. | |||
During development of this proposed TS change, a natural circulation cooldown was | |||
performed on the simulator. The ANO-2 simulator remains updated with respect to physical | |||
changes to the plant, including heat production and heat losses. During the entire event, all | |||
Pressurizer heaters (both the proportional banks and backup banks) were maintained in OFF. | |||
An attempt was also made to place the plant in a condition of greatest challenge in that | |||
following a simulated reactor trip caused by a loss of offsite power, the plant was permitted to | |||
operate automatically until a head bubble was formed (saturated RCS conditions). Operator | |||
intervention following head bubble formation required a very slight cooldown over time using | |||
the upstream atmospheric steam dump valves and minimal feedwater supplied to the SGs. | |||
The cooldown was not required to be commenced until approximately 10 hours after event | |||
initiation. The cooldown was required to be adjusted slightly approximately once every | |||
===1.5 hours=== | |||
due to decay heat load decreasing over time. Twenty-four hours following event | |||
initiation, RCS temperature had only been reduced to 500 °F (normal cold-leg temperature is | |||
545 °F) indicating that the plant can be maintained in Hot Standby (RCS temperature 300 °F) conditions for a significant period of time without excessive bubble formation and without the use of Pressurizer heaters. The simulated natural circulation cooldown was | |||
uneventful and presented no challenge to operators. | |||
With regard to the simulated cooldown above, if a more rapid cooldown were desired, pressure reduction may be delayed due to the need to makeup to the Pressurizer water | |||
volume (volume shrinks as temperature decreases). In addition, normal post-trip Pressurizer | |||
level (41%) may be raised to approximately 80% level to assist in maintaining RCS pressure | |||
above saturated conditions. Nevertheless, the above simulated scenario provides evidence | |||
that permitting the RCS to enter a saturated state under controlled conditions does not | |||
present a challenge to operators nor does it present a challenge to safe reactor operation. | |||
Attachment to 2CAN060903 | |||
Page 6 of 8 | |||
Although it is preferable to maintain the Pressurizer heaters to enhance operation during natural circulation cooldown, the associated limits and surveillance requirements do not meet the intent of 10 CFR 50.36 for inclusion in the TSs in that they are not installed | |||
instrumentation that is used to detect, and indicate in the control room, a significant abnormal | |||
degradation of the reactor coolant pressure boundary, they are not a process variable, design | |||
feature, or operating restriction that is an initial condition of a Design Basis Accident (DBA) or | |||
transient analysis that either assumes the failure of or presents a challenge to the integrity of | |||
a fission product barrier, and they are not a structure, system or component that is part of the | |||
primary success path and which functions or actuates to mitigate a DBA or transient that | |||
either assumes the failure of or presents a challenge to the integrity of a fission product | |||
barrier. In addition, the Pressurizer heaters are not a structure, system, or component which | |||
operating experience or probabilistic risk assessment has shown to be significant to public | |||
health and safety. As discussed above, the Pressurizer heaters are not required to prevent or | |||
mitigate any DBA, nor are they required to successfully complete a natural circulation | |||
cooldown through Mode 3. In Mode 4 (RCS temperature < 300 °F), Shutdown Cooling (SDC) | |||
may be placed in service as desired to exit natural circulation cooldown conditions. | |||
The Pressurizer heaters are not critical to nuclear or public safety for any scenarios modeled | |||
in the ANO-2 safety analyses. Therefore, consistent with the intent of 10 CFR 50.36, the | |||
Pressurizer heater operability requirements, applicability, actions, and surveillance | |||
requirements may be relocated from the TSs to the TRM. Changes to the TRM will continue | |||
to be controlled under the provisions of 10 CFR 50.59. | |||
In addition to the above, the percent-level described in TS 3.4.4 is relocated to the TS Bases. | |||
This "equivalent" to the 910 ft 3 limit contained in the TS can change over time due to changes in instrument uncertainty calculations or due to instrument replacement. Because the | |||
accident analysis is based on the volume limit, relocating the "percent" indication to the TS | |||
Bases does not result in a change to the license basis or the actual TS limit. The percent- | |||
level was originally intended as an operator aid. As such, this information is more | |||
appropriately controlled within the TS Bases. The TS Bases are controlled in accordance | |||
with TS 6.5.14, Technical Specification (TS) Bases Control Program. | |||
==5.0 REGULATORY ANALYSIS== | |||
===5.1 Applicable=== | |||
Regulatory Requirements/Criteria The proposed change has been evaluated to determine whether applicable regulations and | |||
requirements continue to be met. | |||
There are no specific General Design Criteria (GDC) associated with Pressurizer heaters or | |||
the use of operator aids within the TSs (i.e., the current percent-level denoted in Technical | |||
Specification (TS) 3.4.4, Pressurizer | |||
). Pressurizer heaters are discussed in various documents, such as NUREG 0737. However, the proposed change does not eliminate | |||
maintaining Pressurizer heaters, but only acts to relocate the requirements from the TSs to | |||
the TRM. Additionally, the relocation of the percent-level denoted in the TS to the TS Bases | |||
does not change any TS limit or operating requirement. Based on the considerations | |||
discussed above, (1) there is reasonable assurance that the health and safety of the public | |||
will not be endangered by operation in the proposed manner, (2) such activities will continue | |||
to be conducted in accordance with the site licensing basis, and (3) the approval of the | |||
proposed change will not be inimical to the common defense and security or to the health and | |||
safety of the public. | |||
Attachment to 2CAN060903 | |||
Page 7 of 8 | |||
In conclusion, Entergy has determined that the proposed change does not require any exemptions or relief from regulatory requirements, other than the TS, and does not affect | |||
conformance with any GDC differently than descr ibed in the Safety Analysis Report (SAR). | |||
5.2 No Significant Hazards Consideration | |||
A change is proposed to the Arkansas Nuclear One, Unit 2 (ANO-2) Technical Specifications (TSs) to relocate portions of TS 3.4.4, Pressurizer , relating to the Pressurizer heater banks to the Technical Requirements Manual (TRM) and to relocate the percent-level information denoted in the TS to the TS Bases. | |||
Entergy Operations, Inc. (Entergy) has evaluated whether or not a significant hazards | |||
consideration is involved with the proposed amendment by focusing on the three standards | |||
set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below: | |||
: 1. Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated? | |||
Response: No. | |||
The proposed change acts to relocate current Pressurizer heater requirements from | |||
the TSs to the TRM and percent-level information to the TS Bases. The heaters serve | |||
only a support role in maintaining normal operating pressure in the Reactor Coolant | |||
System (RCS) and in can be used to support maintenance of subcooled conditions | |||
during a natural circulation (loss of forced flow) cooldown of the plant. The heaters | |||
are not credited in any accident analysis for accident prevention or mitigation. The | |||
percent-level information is an operator aid and is not associated with any accident or | |||
safety analysis limit. Neither of these items are related to accident initiators. | |||
Therefore, the proposed change does not involve a significant increase in the | |||
probability or consequences of an accident previously evaluated. | |||
: 2. Does the proposed change create the possibility of a new or different kind of accident from any accident previously evaluated? | |||
Response: No. | |||
The proposed change does not result in any plant modifications or changes in the way | |||
the plant is operated. The proposed change only acts to relocate current Pressurizer | |||
heater requirements from the TSs to the TRM and to relocate the percent-level | |||
information denoted in the TS to the TS Bases. The proposed change is unrelated to | |||
any accident initiator. | |||
Therefore, the proposed change does not create the possibility of a new or different | |||
kind of accident from any previously evaluated. | |||
Attachment to 2CAN060903 | |||
Page 8 of 8 | |||
: 3. Does the proposed change involve a significant reduction in a margin of safety? | |||
Response: No. | |||
The proposed change relocates current Pressurizer heater requirements from the TSs | |||
to the TRM and relocates the percent-level information denoted in the TS to the TS | |||
Bases. The heaters serve only a support role in maintaining normal operating | |||
pressure in the Reactor Coolant System (RCS) and can be used to support | |||
maintenance of subcooled conditions during a natural circulation (loss of forced flow) | |||
cooldown of the plant. The current TS-required capacity of each heater bank is well | |||
beyond that required to maintain RCS pressure during normal operations. Non-TS | |||
back-up heaters are also installed to support pressure control during anticipated | |||
transients. The heaters are not credited in any accident analysis for accident | |||
prevention or mitigation. Because the Pressurizer heaters will continue to be | |||
monitored and controlled, relocating the current TS requirements to the TRM will not | |||
present an adverse impact to plant operation. In addition, the Pressurizer heaters are | |||
not a structure, system, or component wh ich operating experience or probabilistic risk assessment has shown to be significant to public health and safety. The percent-level | |||
information currently contained in the TS is an operator aid and is not associated with | |||
any accident or safety analysis limit. | |||
Therefore, the proposed change does not involve a significant reduction in a margin of | |||
safety. | |||
Based on the above, Entergy concludes that the proposed amendment presents no significant | |||
hazards consideration under the standards set forth in 10 CFR 50.92(c), and, accordingly, a | |||
finding of "no significant hazards consideration" is justified. | |||
===5.3 Environmental=== | |||
Considerations | |||
The proposed amendment does not involve (i) a significant hazards consideration, (ii) a | |||
significant change in the types or significant increase in the amounts of any effluent that may | |||
be released offsite, or (iii) a significant increase in individual or cumulative occupational | |||
radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for | |||
categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to | |||
10 CFR 51.22(b), no environmental impact stat ement or environmental assessment need be prepared in connection with the proposed amendment. | |||
==6.0 REFERENCES== | |||
: 1. ANO-2 SAR | |||
: 2. NUREG 0737, November 1980 | |||
: 3. CEN-114-P, Amendment 1-P, "Review of Small Break Transients in CE's Nuclear Steam Supply System," July 1979 Attachment 2 2CAN060903 Proposed Technical Specification Changes (mark-up) | |||
ARKANSAS - UNIT 2 3/4 4-5 Amendment No. 20 | |||
,234 , REACTOR COOLANT SYSTEM | |||
PRESSURIZER | |||
LIMITING CONDITION FOR OPERATION 3.4.4 The pressurizer shall be OPERABLE with a water volume of 910 cubic feet (equivalent to 82% of wide range indicated level) and both pressurizer proportional heater groups shall be OPERABLE. APPLICABILITY: MODES 1, 2 and 3. | |||
ACTION: (a) With the pressurizer inoperable due to water volume 910 cubic feet, be in at least HOT SHUTDOWN with the reactor trip breakers open within 12 hours. | |||
(b) With the pressurizer inoperable due to an inoperable emergency power supply to the pressurizer heaters, either restore the inoperable emergency power supply as required by TS 3.8.1.1 action b.3 or be in at least HOT SHUTDOWN within 12 hours. | |||
SURVEILLANCE REQUIREMENTS | |||
4.4.4.1 The pressurizer water volume shall be determined to be within its limits at least once per 12 hours. | |||
4.4.4.2 The pressurizer proportional heater groups shall be determined to be OPERABLE. | |||
(a) At least once per 12 hours by verifying emergency power is available to the heater groups, and (b) At least once per 18 months by verifying that the summed power consumption of the two proportional heater groups is 150 KW.}} |
Revision as of 05:10, 19 March 2019
ML091760204 | |
Person / Time | |
---|---|
Site: | Arkansas Nuclear |
Issue date: | 06/18/2009 |
From: | Walsh K Entergy Operations |
To: | Document Control Desk, Office of Nuclear Reactor Regulation |
References | |
2CAN060903 | |
Download: ML091760204 (13) | |
Text
June 18, 2009
U.S. Nuclear Regulatory Commission
Attn: Document Control Desk
Washington, DC 20555
SUBJECT:
License Amendment Request Technical Specification Changes To Relocate Pressurizer Heater
Requirements to TRM
Arkansas Nuclear One, Unit 2
Docket No. 50-368
License No. NPF-6
Dear Sir or Madam:
Pursuant to 10 CFR 50.90, Entergy Operations, Inc. (Entergy) hereby requests the following
amendment for Arkansas Nuclear One, Unit 2 (ANO-2). The proposed change will relocate
portions of Technical Specification (TS) 3.4.4, Pressurizer , to the Technical Requirements Manual (TRM). TS 3.4.4 specifies operability requirements for both the water volume in the
Pressurizer and the electric heater capacity of the Pressurizer. The proposed change will
relocate the heater requirements to the TRM.
The heater bank and capacity requirements for the Pressurizer are not credited in the accident
analyses and, therefore, are proposed for relocation to the station TRM. This is consistent
with the intent of 10 CFR 50.36 in that the heaters do not meet the requirements for inclusion
in the TSs. Changes to the TRM are controlled in accordance with the requirements of 10
CFR 50.59. The associated TS Bases, controlled in accordance with the TS Bases Control
Program of TS 6.5.14, will also be relocated to the TRM. The relocation of the TS Bases is
part of the ANO TS change implementation process; therefore, a markup of the TS Bases is
not provided in this submittal.
In addition to the above, the percent-level described in TS 3.4.4 is relocated to the TS Bases.
This "equivalent" to the 910 ft 3 limit contained in the TS can change over time due to changes in instrument uncertainty calculations or due to instrument replacement. Because the accident
analysis is based on the volume limit, relocating the "percent" indication to the TS Bases does
not result in a change to license basis or the actual TS limit.
The proposed change has been evaluated in accordance with 10 CFR 50.91(a)(1) using
criteria in 10 CFR 50.92(c) and it has been determined that the changes involve no significant
hazards consideration. The bases for these determinations are included in the attached
submittal. Entergy Operations, Inc.
1448 S.R. 333 Russellville, AR 72802
Tel 479-858-3110 Kevin T. Walsh Vice President, Operations A rkansas Nuclear One
2CAN060903 Page 2 of 2
The proposed change does not include any new commitments.
Although this request is neither exigent nor emergency, your prompt review is requested.
Once approved, the amendment sha ll be implemented within 90 days.
If you have any questions or require additional information, please contact David Bice at
479-858-5338.
I declare under penalty of perjury that the foregoing is true and correct. Executed on
June 18, 2009.
Sincerely, Brad Berryman for Kevin Walsh KTW/dbb
Attachments:
- 1. Analysis of Proposed Technical Specification Change
- 2. Proposed Technical Specification Changes (mark-up)
cc: Mr. Elmo E. Collins Regional Administrator U. S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125
NRC Senior Resident Inspector Arkansas Nuclear One P. O. Box 310
London, AR 72847 U. S. Nuclear Regulatory Commission
Attn: Mr. Kaly Kalyanam
MS O-8 B1
One White Flint North
11555 Rockville Pike
Rockville, MD 20852 Mr. Bernard R. Bevill
Radiation Control Section
4815 West Markham Street Slot #30 Little Rock, AR 72205 Attachment 1 2CAN060903 Analysis of Proposed Technical Specification Change Attachment to 2CAN060903
Page 1 of 8
1.0 DESCRIPTION
This letter is a request to amend Operating License NPF-6 for Arkansas Nuclear One, Unit 2 (ANO-2).
The proposed change will relocate portions of Technical Specification (TS) 3.4.4, Pressurizer , to the ANO-2 Technical Requirements Manual (TRM). This TS specifies operability
requirements for both the water volume in the Pressurizer and the electric heater capacity of
the Pressurizer. The proposed change will relocate the heater requirements to the TRM.
Changes to the TRM are controlled in accordance with 10 CFR 50.59.
In addition to the above, the percent-level described in TS 3.4.4 is relocated to the TS Bases.
Because the safety analysis is based on the volume limit, relocating the "percent" indication to
the TS Bases does not result in a change to license basis or the actual TS limit.
2.0 PROPOSED CHANGE
The electric heater portion of ANO-2 TS 3.4.4, Pressurizer , is proposed for relocation to the ANO-2 TRM. During relocation, the current TS Actions may be modified. Such modification, if performed, will be in accordance with the requirements of 10 CFR 50.59. A markup of the
affected TS page is included in Attachment 2 of this submittal.
In addition to the above, the percent-level described in TS 3.4.4 is relocated to the TS Bases.
This "equivalent" to the 910 ft 3 limit contained in the TS can change over time due to changes in instrument uncertainty calculations or due to instrument replacement. Because the
accident analysis is based on the volume limit, relocating the "percent" indication to the
TS Bases does not result in a change to license basis or the actual TS limit.
3.0 BACKGROUND
TS 3.4.4 requires two proportional heater banks to be operable in Modes 1, 2, and 3 with a
capacity of 150 Kilowatts (kW) each. These heater banks are powered from vital AC buses backed by a respective TS-required Emergency Diesel Generator (EDG). In addition to the
two proportional heater banks, non-vital back-up heater banks are also installed to help
accommodate significant transients during normal power operation.
The pressure in the Reactor Coolant System (RCS) is controlled by regulating the
temperature of the coolant in the Pressurizer, where steam and water are held in thermal
equilibrium. Steam is formed by the Pressu rizer heaters or condensed by the Pressurizer spray to reduce variations caused by expansion and contraction of the reactor coolant due to
system temperature changes.
The Pressurizer heaters are single unit, direct immersion heaters which protrude vertically
into the Pressurizer through sleeves welded in the lower head. Approximately one-third of the
heaters are connected to proportional controllers which adjust the heat input as required to
compensate for steady state losses and to maintain the desired steam pressure in the
Pressurizer. The remaining backup heaters are connected to on-off controllers. These
heaters are normally de-energized, but will automatically energize on a low Pressurizer Attachment to 2CAN060903
Page 2 of 8
pressure signal or high level error signal. This latter feature is provided since load increases result in an in-surge of relatively cold coolant into the Pressurizer, thereby decreasing the bulk
water temperature. The Chemical and Volume Cont rol System (CVCS) acts to restore level, resulting in a transient pressure below normal operating pressure. To minimize the extent of
this transient, the backup heaters are energized, contributing more heat to the water. A low-
low Pressurizer level signal de-energizes all heaters to protect the heaters should they
uncover.
The Pressurizer proportional heater feeders are furnished with power (watt) transducers
providing an analog value of the circuit power to the Safety Parameter Display System (SPDS). The magnitude of the power indicates the operational status and integrity of the
heater bank.
The 150 kW of Pressurizer heater capacity powered from an assured power source will
ensure that RCS subcooling margin will be maintained 20 °F for a period of 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br /> following loss of off-site power. This time period includes a period of one-half hour at the
beginning of the transient in which the heaters are unavailable.
This calculation is conservative in that the actual heat losses would decrease during the
transient as RCS pressure and temperature decreases, thereby prolonging the time to reach
20 °F margin-to-saturation.
The TS limit on Pressurizer volume exists to ensure the system is not operated under water-
solid conditions. Such operation would preclude appropriate pressure control and could
challenge the RCS pressure boundary. The percent-level indication provided in the TS was
intended only as an operator aid and is not used in the accident analysis. This operator aid
can change over time due to instrument replacem ent or calculation adjustment of instrument uncertainty. Therefore, it is proposed that this operator aid be relocated to the TS Bases.
The Pressurizer is discussed throughout the ANO-2 Safety Analysis Report (SAR), including
Sections 5.5.10 and 7.7.1.1.2 (Reference 1). Note that the Pressurizer heaters are not
discussed in SAR Chapter 15, Accident Analysis , nor credited in the accident analysis, except to state their loss on low Pressurizer level in Table 15.1.18-2.
Natural Circulation
Accident analyses presented in the SAR do not take credit for Pressurizer heater operation;
however, an implicit initial condition assumption of the safety analyses is that the RCS is
operating at normal pressure.
Although the heaters are not specifically used in accident analysis, the desire to maintain
subcooled margin over the long term during a loss of offsite power, as indicated in
NUREG 0737, Clarification of TMI Action Plan Requirements (Reference 2), is the reason for their original inclusion in the TSs. The requirement for emergency power supplies is also
based on NUREG 0737. The intent is to keep the reactor coolant in a subcooled condition
with natural circulation cooling at hot, high pressure conditions for an undefined, but extended
time period after a loss of offsite power. While loss of offsite power is a coincident occurrence
assumed in the accident analyses, maintaining hot, high pressure conditions over an
extended time period is not evaluated in the accident analyses.
Attachment to 2CAN060903
Page 3 of 8
Following the accident at Three Mile Island in 1979, NUREG 0737 was developed by the NRC to address a wide array of needed safety enhancements at commercial nuclear power
plants. As mentioned above, the Pressurizer heaters were included in NUREG 0737 to
support natural circulation (i.e., loss of forced flow) conditions following a loss of off-site
power. Reactor coolant pumps are lost when off-site power is lost and the RCS begins to
transition to natural circulation as the hot water from the reactor core rises through the RCS
hot leg piping to the Steam Generators (SGs) where it is cooled as it passes through the SG
tubes and descends back through the RCS cold leg piping to the bottom of the core where it
again absorbs heat from the core as it rises through the fuel region. This natural convection
flow continues as long as a minimum water level is maintained in the SGs and
thermohydraulic communication is maintained throughout the RCS hot and cold leg piping.
Following the TMI accident, it was believed that a plant cooldown via natural circulation could
result in a steam bubble being formed in the reactor vessel head region. This is because the
head region is a low or stagnant flow area of the vessel and would not be readily cooled by
natural circulation flow. A slow cooldown would permit time for ambient heat losses from the
reactor vessel head to afford necessary head-area cooling to inhibit steam bubble formation.
However, a more rapid cooldown may not permit sufficient time for adequate vessel head
cooldown and subsequently, formation of a steam bubble in the head region may occur. If
this postulated condition were to continue uninhibited, it was thought the bubble could
increase in size until it entered the hot leg piping, creating an adverse impact on the
thermohydraulic communication needed to maintain natural circulation flow. Therefore, Pressurizer heaters were adopted as a means of increasing the RCS pressure to either
maintain adequate subcooled margin with respect to vessel head conditions during natural
circulation cooldown or to collapse any steam bubble in the vessel head should one develop.
Benefit of Proposed Change
On several occasions since initial startup, ANO-2 has experienced conditions where a
proportional heater bank was found to narrowly meet the 150 kW TS requirement or found to
have a capacity slightly below the TS requiremen
- t. Such conditions could prevent unit startup if discovered during a plant outage or could result in an unnecessary plant shutdown if
discovered in Mode 1, 2, or 3. In addition, since the TS requirement for the proportional
heaters is based on natural circulation cooldown support and therefore, a loss of offsite power
event, the heater bank must be declared inoperable anytime its respective emergency power
supply is removed for maintenance (i.e., the respective EDG or necessary
switchgear/breakers). These conditions place an undue hardship on the plant and plant
personnel in requiring significant prompt action or plant shutdown for an inoperable
component that is not credited in the safety analysis and is not the only means of ensuring
safe plant cooldown using the natural circulation method. Therefore, Entergy requests these
non-credited heater bank requirements be relocated from the TSs to the TRM.
Because heaters provide necessary pressure control during power operation and can be an
effective tool in supporting natural circulation cooldown, Entergy will continue to maintain
appropriate functionality of the heater banks. Any future changes to the TRM heater
requirements will be controlled in accordance with 10 CFR 50.59.
Attachment to 2CAN060903
Page 4 of 8
4.0 TECHNICAL ANALYSIS
TS 3.4.4 requires two groups of Pressurizer heaters, each with a capacity 150 kW and capable of being powered from an emergency power supply. The minimum heater capacity
required is sufficient to maintain the RCS near normal operating pressure when accounting
for heat losses through the Pressurizer insulation. By maintaining the pressure near normal
operating conditions, a substantial subcooling margin can be maintained in the RCS loops
during a natural circulation cooldown. The amount of heater capacity needed to maintain
pressure is dependent on the ambient heat losses (see background information in preceding
section).
As discussed in the Background section above, the post-TMI concern was the formation of a
steam bubble in the reactor vessel head region during natural circulation cooldown of the
plant. However, experience gained since the 1979 TMI accident indicates that there are other
means of controlling head bubble formation and growth.
Note that the following discussions assume a natural circulation cooldown is required without
a loss of RCS inventory that would result in loss of thermohydraulic communication in the RCS. Natural circulation cooldown is not relevant to such scenarios since the injection of
borated water via high and/or low pressure safety injection pumps will be required to maintain
inventory and support the necessary cooldown of the reactor core.
The most significant bubble prevention method is to control the rate of natural circulation
cooldown while monitoring reactor vessel head temperatures. Besides Pressurizer heaters, NUREG 0737 also required a means of monitoring reactor vessel head temperature and
reactor vessel reactor coolant level. ANO-2 has multiple Core Exit Thermocouples (CETs) for
use in monitoring temperature in the upper regions of the reactor vessel. At least 2 CETs are
required per core quadrant in accordance with TS 3.3.3.6, Post-Accident Instrumentation , in Modes 1, 2, and 3. ANO-2 also has a Reacto r Vessel Level Monitoring System (RVLMS) that will indicate when steam bubble formation begins and monitor bubble growth during natural
circulation conditions. Two channels of RVLMS are required to be operable in accordance
with TS 3.3.3.6. The Plant Monitoring System (PMS) and SPDS computer also provide real-time display of RCS pressure-temperature relationships to plant operators for monitoring
subcooled margin, the rate of cooldown, and the driving force effectiveness (core delta-
temperature), among other things. Operations procedures contain in-depth discussion and
guidance with regard to head bubble formation, prevention, and mitigation during natural
circulation cooldown conditions. In the years since the TMI accident, operators have
continuously practiced plant cooldowns under natural circulation conditions using plant simulators. Based on current plant capabilities and extensive operator knowledge and
experience, the uncontrolled formation and growth of a steam bubble in the reactor vessel
head is extremely unlikely.
In addition to the above, RCS pressure can be increased by normal inventory makeup
sources. RCS level slowly decreases as the RCS temperature is lowered during the
cooldown. A charging pump or high pressure injection pump is used at ANO-2 to makeup for
this "shrink" in RCS level due to density changes. However, level can be raised in the
Pressurizer beyond that needed to account for the density changes which will result in an
additional increase in RCS pressure. This method of pressure control is proceduralized and
well understood by plant operators.
Attachment to 2CAN060903
Page 5 of 8
Notwithstanding the above, if a bubble were to form and grow to the point of reaching the top of the vessel flow region, the cooler temperature of the water in the flow region would
immediately collapse the steam attempting to enter the hot leg. This is enhanced by the fact
that natural circulation flow is relatively low and the transport time from the reactor vessel to
the SG does not permit rapid entrainment of steam that could reach the top of the SG tubes
and inhibit natural circulation flow. Therefore, even in the event the natural circulation
cooldown is not as controlled as desired, the steam bubble should not be capable of
preventing natural circulation flow. To project the improbable and assume that steam is
transported from the upper region of the vessel to the top of the steam generator tubes and
interrupt thermohydraulic communication, the coolant would then enter a state of reflux boiling
where the hot water travels through the hot leg and up one side of the SG tubes, cools, and
returns through the lower portion of the hot leg back into the reactor vessel. This is a well
defined phenomenon that is discussed in Combustion Engineering (CE) topical CEN-114-P, Amendment 1-P (Reference 3). In summary, the ov erriding safety function of core cooling is maintained regardless of the methods used, or not used, to control a natural circulation
cooldown.
If core cooling could be lost due to bubble formation in the reactor vessel head, procedures
provide for re-establishment of core cooling by either collapsing the bubble or depressurize
the RCS to permit high pressure safety injection. With regard to the former and as discussed
above, Pressurizer heaters are not required for bubble collapse, but can be used to support
bubble collapse if available.
During development of this proposed TS change, a natural circulation cooldown was
performed on the simulator. The ANO-2 simulator remains updated with respect to physical
changes to the plant, including heat production and heat losses. During the entire event, all
Pressurizer heaters (both the proportional banks and backup banks) were maintained in OFF.
An attempt was also made to place the plant in a condition of greatest challenge in that
following a simulated reactor trip caused by a loss of offsite power, the plant was permitted to
operate automatically until a head bubble was formed (saturated RCS conditions). Operator
intervention following head bubble formation required a very slight cooldown over time using
the upstream atmospheric steam dump valves and minimal feedwater supplied to the SGs.
The cooldown was not required to be commenced until approximately 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> after event
initiation. The cooldown was required to be adjusted slightly approximately once every
1.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />s
due to decay heat load decreasing over time. Twenty-four hours following event
initiation, RCS temperature had only been reduced to 500 °F (normal cold-leg temperature is
545 °F) indicating that the plant can be maintained in Hot Standby (RCS temperature 300 °F) conditions for a significant period of time without excessive bubble formation and without the use of Pressurizer heaters. The simulated natural circulation cooldown was
uneventful and presented no challenge to operators.
With regard to the simulated cooldown above, if a more rapid cooldown were desired, pressure reduction may be delayed due to the need to makeup to the Pressurizer water
volume (volume shrinks as temperature decreases). In addition, normal post-trip Pressurizer
level (41%) may be raised to approximately 80% level to assist in maintaining RCS pressure
above saturated conditions. Nevertheless, the above simulated scenario provides evidence
that permitting the RCS to enter a saturated state under controlled conditions does not
present a challenge to operators nor does it present a challenge to safe reactor operation.
Attachment to 2CAN060903
Page 6 of 8
Although it is preferable to maintain the Pressurizer heaters to enhance operation during natural circulation cooldown, the associated limits and surveillance requirements do not meet the intent of 10 CFR 50.36 for inclusion in the TSs in that they are not installed
instrumentation that is used to detect, and indicate in the control room, a significant abnormal
degradation of the reactor coolant pressure boundary, they are not a process variable, design
feature, or operating restriction that is an initial condition of a Design Basis Accident (DBA) or
transient analysis that either assumes the failure of or presents a challenge to the integrity of
a fission product barrier, and they are not a structure, system or component that is part of the
primary success path and which functions or actuates to mitigate a DBA or transient that
either assumes the failure of or presents a challenge to the integrity of a fission product
barrier. In addition, the Pressurizer heaters are not a structure, system, or component which
operating experience or probabilistic risk assessment has shown to be significant to public
health and safety. As discussed above, the Pressurizer heaters are not required to prevent or
mitigate any DBA, nor are they required to successfully complete a natural circulation
cooldown through Mode 3. In Mode 4 (RCS temperature < 300 °F), Shutdown Cooling (SDC)
may be placed in service as desired to exit natural circulation cooldown conditions.
The Pressurizer heaters are not critical to nuclear or public safety for any scenarios modeled
in the ANO-2 safety analyses. Therefore, consistent with the intent of 10 CFR 50.36, the
Pressurizer heater operability requirements, applicability, actions, and surveillance
requirements may be relocated from the TSs to the TRM. Changes to the TRM will continue
to be controlled under the provisions of 10 CFR 50.59.
In addition to the above, the percent-level described in TS 3.4.4 is relocated to the TS Bases.
This "equivalent" to the 910 ft 3 limit contained in the TS can change over time due to changes in instrument uncertainty calculations or due to instrument replacement. Because the
accident analysis is based on the volume limit, relocating the "percent" indication to the TS
Bases does not result in a change to the license basis or the actual TS limit. The percent-
level was originally intended as an operator aid. As such, this information is more
appropriately controlled within the TS Bases. The TS Bases are controlled in accordance
with TS 6.5.14, Technical Specification (TS) Bases Control Program.
5.0 REGULATORY ANALYSIS
5.1 Applicable
Regulatory Requirements/Criteria The proposed change has been evaluated to determine whether applicable regulations and
requirements continue to be met.
There are no specific General Design Criteria (GDC) associated with Pressurizer heaters or
the use of operator aids within the TSs (i.e., the current percent-level denoted in Technical
Specification (TS) 3.4.4, Pressurizer
). Pressurizer heaters are discussed in various documents, such as NUREG 0737. However, the proposed change does not eliminate
maintaining Pressurizer heaters, but only acts to relocate the requirements from the TSs to
the TRM. Additionally, the relocation of the percent-level denoted in the TS to the TS Bases
does not change any TS limit or operating requirement. Based on the considerations
discussed above, (1) there is reasonable assurance that the health and safety of the public
will not be endangered by operation in the proposed manner, (2) such activities will continue
to be conducted in accordance with the site licensing basis, and (3) the approval of the
proposed change will not be inimical to the common defense and security or to the health and
safety of the public.
Attachment to 2CAN060903
Page 7 of 8
In conclusion, Entergy has determined that the proposed change does not require any exemptions or relief from regulatory requirements, other than the TS, and does not affect
conformance with any GDC differently than descr ibed in the Safety Analysis Report (SAR).
5.2 No Significant Hazards Consideration
A change is proposed to the Arkansas Nuclear One, Unit 2 (ANO-2) Technical Specifications (TSs) to relocate portions of TS 3.4.4, Pressurizer , relating to the Pressurizer heater banks to the Technical Requirements Manual (TRM) and to relocate the percent-level information denoted in the TS to the TS Bases.
Entergy Operations, Inc. (Entergy) has evaluated whether or not a significant hazards
consideration is involved with the proposed amendment by focusing on the three standards
set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:
- 1. Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?
Response: No.
The proposed change acts to relocate current Pressurizer heater requirements from
the TSs to the TRM and percent-level information to the TS Bases. The heaters serve
only a support role in maintaining normal operating pressure in the Reactor Coolant
System (RCS) and in can be used to support maintenance of subcooled conditions
during a natural circulation (loss of forced flow) cooldown of the plant. The heaters
are not credited in any accident analysis for accident prevention or mitigation. The
percent-level information is an operator aid and is not associated with any accident or
safety analysis limit. Neither of these items are related to accident initiators.
Therefore, the proposed change does not involve a significant increase in the
probability or consequences of an accident previously evaluated.
- 2. Does the proposed change create the possibility of a new or different kind of accident from any accident previously evaluated?
Response: No.
The proposed change does not result in any plant modifications or changes in the way
the plant is operated. The proposed change only acts to relocate current Pressurizer
heater requirements from the TSs to the TRM and to relocate the percent-level
information denoted in the TS to the TS Bases. The proposed change is unrelated to
any accident initiator.
Therefore, the proposed change does not create the possibility of a new or different
kind of accident from any previously evaluated.
Attachment to 2CAN060903
Page 8 of 8
- 3. Does the proposed change involve a significant reduction in a margin of safety?
Response: No.
The proposed change relocates current Pressurizer heater requirements from the TSs
to the TRM and relocates the percent-level information denoted in the TS to the TS
Bases. The heaters serve only a support role in maintaining normal operating
pressure in the Reactor Coolant System (RCS) and can be used to support
maintenance of subcooled conditions during a natural circulation (loss of forced flow)
cooldown of the plant. The current TS-required capacity of each heater bank is well
beyond that required to maintain RCS pressure during normal operations. Non-TS
back-up heaters are also installed to support pressure control during anticipated
transients. The heaters are not credited in any accident analysis for accident
prevention or mitigation. Because the Pressurizer heaters will continue to be
monitored and controlled, relocating the current TS requirements to the TRM will not
present an adverse impact to plant operation. In addition, the Pressurizer heaters are
not a structure, system, or component wh ich operating experience or probabilistic risk assessment has shown to be significant to public health and safety. The percent-level
information currently contained in the TS is an operator aid and is not associated with
any accident or safety analysis limit.
Therefore, the proposed change does not involve a significant reduction in a margin of
safety.
Based on the above, Entergy concludes that the proposed amendment presents no significant
hazards consideration under the standards set forth in 10 CFR 50.92(c), and, accordingly, a
finding of "no significant hazards consideration" is justified.
5.3 Environmental
Considerations
The proposed amendment does not involve (i) a significant hazards consideration, (ii) a
significant change in the types or significant increase in the amounts of any effluent that may
be released offsite, or (iii) a significant increase in individual or cumulative occupational
radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for
categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to
10 CFR 51.22(b), no environmental impact stat ement or environmental assessment need be prepared in connection with the proposed amendment.
6.0 REFERENCES
- 1. ANO-2 SAR
- 2. NUREG 0737, November 1980
- 3. CEN-114-P, Amendment 1-P, "Review of Small Break Transients in CE's Nuclear Steam Supply System," July 1979 Attachment 2 2CAN060903 Proposed Technical Specification Changes (mark-up)
ARKANSAS - UNIT 2 3/4 4-5 Amendment No. 20
,234 , REACTOR COOLANT SYSTEM
PRESSURIZER
LIMITING CONDITION FOR OPERATION 3.4.4 The pressurizer shall be OPERABLE with a water volume of 910 cubic feet (equivalent to 82% of wide range indicated level) and both pressurizer proportional heater groups shall be OPERABLE. APPLICABILITY: MODES 1, 2 and 3.
ACTION: (a) With the pressurizer inoperable due to water volume 910 cubic feet, be in at least HOT SHUTDOWN with the reactor trip breakers open within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
(b) With the pressurizer inoperable due to an inoperable emergency power supply to the pressurizer heaters, either restore the inoperable emergency power supply as required by TS 3.8.1.1 action b.3 or be in at least HOT SHUTDOWN within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
SURVEILLANCE REQUIREMENTS 4.4.4.1 The pressurizer water volume shall be determined to be within its limits at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
4.4.4.2 The pressurizer proportional heater groups shall be determined to be OPERABLE.
(a) At least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> by verifying emergency power is available to the heater groups, and (b) At least once per 18 months by verifying that the summed power consumption of the two proportional heater groups is 150 KW.