ML20206U464
| ML20206U464 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 05/18/1999 |
| From: | Caldwell J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Kingsley O COMMONWEALTH EDISON CO. |
| References | |
| NOED-99-3-002, NOED-99-3-2, NUDOCS 9905250232 | |
| Download: ML20206U464 (5) | |
Text
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UNITED STATES
- [** 40u~ o NUCLEAR REGULATORY COMMISSION E' ' ,7, REGloN ll1
.$ $ 801 WARRENVILLE ROAD s lisle. ILLINots 60532-4351
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May 18, 1999 Mr. Oliver D. Kingsley President, Nuclear Generation Group Commonwealth Edison Company.
ATTN: Regulatory Services .
Executive Towers West lli l 1400 Opus Place, Suite 500 l Downers Grove, IL 60515
SUBJECT:
NOTICE OF ENFORCEMENT DISCRETION FOR COMMONWEALTH EDISON COMPANY REGARDING BRAIDWOOD UN!T 1, NOED 99-3-02
Dear Mr. Kingsley:
By letter dated May 17,1999 (enclosed), your staff requested that the NRC exercise discretion not to enforce compliance with the actions required in Technical Specification 3.0.3. That letter documented information previously discussed with the NRC in a telephone conversation on May 16,1999, at approximately 3:00 p.m. (CDT). The principal NRC staff members who participated in that telephone conference included John Grobe, Director, Division of Reactor Safety, Region Ill; Marc Dapas, Deputy Director, Division of Reactor Projects, Region lil; Michael Jordan, Chief, Reactor Projects Branch 3, Division of Reactor Projects, Region Ill; I Cecil Thomas, Director, Project Directorate 111, Office of Nuclear Reactor Regulation (NRR); I and Eric Weiss, Chief, Pressurized Water Reactor Section, Reactor Systems Branch, NRR.
Your staff stated that on May 16 at 8:43 a.m., due to a small air pocket in the discharge piping common to both emergency core cooling system (ECCS) trains, Braidwood Unit 1 was required ;
to enter Technical Specification 3.0.3. You entered Technical Specification 3.0.3 because l Surveillance Requirement 3.5.2.3 could not be met which required your staff every 31 days to
" verify ECCS piping full of water," and because the subsequent limiting condition for operation (LCO) 3.5.2, ECCS Operating, could not be satisfied. Technical Specification 3.0.3 states:
"When an LCO is not met and the associated actions are not met, an associated
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action is not provided, or if directed by the associated actions, the unit shall be placed in a mode or other specified condition in which the limiting condition for operation is not applicable. Action shall be initiated within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to place the unit, as applicable, in mode 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. . . "
Your staff requested that a Notice of Enforcement Discretion (NOED) be issued pursuant to the NRC's policy regarding exercise of discretion for an operating facility, set out in Section Vll.c, of the " General Statement of Policy and Procedures for NRC Enforcement Actions"(Enforcement Policy), NUREG-1600, and be effective for the period of 14 days. This letter documents our telephone conversation on May 16,1999, at approximately 3:00 p.m. (CDT), when we orally issued this NOED.
9905250232 990518 PDR ADOCK 05000456 P PDR l:
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- l O. Kingsley l Your staff presented the basis for their conclusion that granting the NOED would not result in a safety concern. Their conclusion was based on the results of a study performed by Stone and )
Webster, entitled," Fluid Transient Study of the ECCS Piping Due to Pump Start-Up With Air l Bubble," which calculated the amount of load placed on the Residual Heat Removal piping caused by a water hammer, and an additional study performed by the Illinois Department of Nuclear Safety that evaluated the water hammer effects on ECCS piping containing large quantities of entrapped gas. The results of these studies indicated that piping loads and pressures resulting from a water hammer caused by 12 cubic feet of non-condensable gas into the piping would not damage the Residual Heat Removal system piping. Through qualitative assessment, your staff also stated that the addition of such a small amount of gas would have l no impact on the results of existing safety analyses for peak cladding temperature. A l quantitative analysis of the effect on the peak cladding temperature during a large break loss of '
coolant accident of injecting an additional 10 cubic feet of non-condensable gas into the vessel was performed. The results of that analysis are presented in your May 17,1999 letter. This analysis stated that the addition of an extra 10 cubic feet of non-condensable gasses would have no negative impact on peak cladding temperature. Consequently, having less than ,
10 cubic feet of gas in the piping would not impact the safety function of the ECCS. )
l Your staff proposed the following compensatory measures to be implemented throughout the duration of the NOED. All operating crews will be briefed about the existing problem and all .
work schedules will be reviewed to minimize work on the ECCS trains. The venting or l ultrasonic examination of piping high points will be performed inside and outside the
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containment on a weekly basis. The frequency of adding water to the 1D Safety injection l Accumulator will be monitored because of the belief by your staff that this was the most likely source of the gas. If the frequency of adding water increases by more than 50 percent over current trends, the frequency of venting and ultrasonic evaluation of piping inside and outside of containment willincrease to twice weekly. If gas pockets or voids are identified which total greater than 10 cubic feet, the unit will be shut down.
The NRC accepted the licensee's safety rationale combined with compensatory actions as an adequate basis for this NOED. The staff also accepted the proposed duration of the NOED l based on the time to procure parts and install additional vent valves on system high points.
Based on the above, the staff concluded that the Criterion 1 of Section B to NRC Manual Chapter 9900, " Technical Guidance, Operations - Notice of Enforcement Discretion," was met. l This criteria states that for an operating plant, the NOED is intended to avoid an undesirable transient as a result of forcing compliance with the license condition, and thus minimize the potential safety consequences and operational risks.
Consequently, the staff has concluded that this NOED is warranted because it involves minimal or no plant safety impact, is consistent with the enforcement policy and staff guidance, and has
! no adverse impact on public health and safety. Therefore, it is our intention to exercise discretion not to enforce compliance with Technical Specification 3.0.3 as related to the control of non-condensable gasses in the ECCS piping for the period from May 16,1999, at 8:43 a.m.
until May 30,1999, at 8:43 a.m., a period of 14 days. Notwithstanding our granting this NOED, we are concerned that considerable NRC staff interaction was necessary to address this issue.
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I O. Kingsley l I
As stated in the Enforcement Policy, action will normally be taken, to the extent that violations l were involved, for the root cause that led to the noncompliance for which this NOED was I
necessary.
Sincerely, l
/s/ J. L. Caldwell James L. Caldwell Deputy Regional Administrator Docket Nos. 50-456; 50-457 License Nos. NPF-72; NPF-77
Enclosure:
As stated cc w/ encl: D. Helwig, Senior Vice President H. Stanley, PWR Vice President C. Crane, BWR Vice President R. Krich, Vice President, Regulatory Services DCD - Licensing T. Tulon, Site Vice President K. Schwartz, Station Manager T. Simpkin, Regulatory Assurance Supervisor M. Aguilar, Assistant Attorney General State Liaison Officer Chairman, Illinois Commerce Commission l
DOCUMENT NAME: G:\brai\branoed.599
- See previous concurrences To receive e copy of this document, indicate in the box "C" = Copy without ettlenci 'E" - Copy wlettlenci *N" - No copy OFFICE ' Rill E
- Rill lE
- Rill lN 'NRR E RP / ,6, l NAME Jordan:co Clayton Grobe Thomas vie isiecon da dell DATE 05/18/99 05/18/99 05/18/99 05/18/99 03/N99 OFFICIAL RECORD COPY
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O. Kingsley However, as stated in the Enforcement Policy, action will normally be taken, to the extent that violations were involved, for the root cause that led to the noncompliance for which this NOED was necessary.
Sincerely, James L. Caldwell Deputy Regional Administrator Docket Nos. 50-456;50-457 License Nos. NPF-72; NPF-77
Enclosure:
As stated cc w/ encl: D. Helwig, Senior Vice President H. Stanley, PWR Vice President C. Crane, BWR Vice President R. Krich, Vice President, Regulatory Services DCD - Licensing T. Tulon, Site Vice President K. Schwartz, Station Manager T. Simpkin, Regulatory Assurance Supervisor M. Aguilar, Assistant Attorney General State Liaison Officer Chairman, Illinois Commerce Commission l
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l DOCUMENT NAME: G:\brai\branoed.599 l
To receive e copf of thle document. Indicate in the bom "C" = Copy without ettlenet *E" = Copy wIett,enet 'N' = No copy ;
OFFICE Rlll lf Rlli l6 Rlli 1l9 NRR M l6 _Rlli l NAME Jordan:coM Clayton [G GrobeQM iThom3 M 7Caldwell DATE 05/IT/99 " 05//S/99 05/%/89 7 05/)t/99" 05/ /99 OFFICIAL RECORD COPY
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. ; <. > n:? .w,a May 17,1999 U S Nuclear Regulatory Commission ATTN Document Control Desk Washington DC, 20555-0001 Braidwood Station, Unit 1 Facility Operating License No. NPF-72 NRC Docket No. STN 50-456 l l
Subject:
Request for Notice of Enforcement Discretion Conceming Extension of the Shutdown Requiremont of Technical Specification Limiting Condition for Operation 3.0.3
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The purpose of this letter is to provide the written follow-up of our request for a Notice of Enforcement Discretion (NOED) from compliance with Draidwood Station, Unit 1 Technical Specifications (TS), Limiting Condition for Operation (LCO) 3.0.3. Entry into LCO 3 0.3 was required due to the discovery of a gas pocket in Emergency Core Cooling System (ECCS) discharge piping common to both ECCS trains. Because the gas pocket (that could not be vented) was in a section of piping required for cither train of Low Pressure Safety injection to inject to all four Reactor Coolant System cold legs.
both trains of ECCS were considered inoperable. With both ECCS trains inoperable, the provisions of TS LCO 3.S 2, "ECCS-Operating," could not be satisfied. Accordingly. TS LCO 3 0 3 must be entered and requires within one hour, action be taken to place the unit in Hot Standby within seven hours, Hot Shutdown within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and Cold Shutdown within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />.
On May 13,1999. TS Surveillance Requirement 3.S.2.3 was performed. This ,
j surveillance involves verifying that the ECCS piping is full of water by venting off outside containment high points. During the performance of this surveillance, gas was noted {
exiting the piping during tho vonting process. As required by procedures and TS bases. l ultrasonic testing of susceptible piping not equipped with vent valves was completed !
This examination revealed gas pocket associated with the "B" train of ECCS piping that I l
could not be vented nor removed by flushing The affected train of ECCS was declared l
inoperable at 2350 on May 13,1999. Actions were initiated to install a vent valve in the section of piping with the gas pocket. Upon completion of the installation and successful venting of the line, confirmatory ultrasonic testing of the remaining susceptible locations was performed. This testing revealed a gas pocket in the common piping for both i ECCS trains, bnth trains of ECCS were declared inoperable and LCO 3.0.3 was entered I at 0843 on May 16,1999 i
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May 17,1999 U. S. Nuclear Regulatory Commission Page 2 Using the guidance provided in NRC Administrative Letter (AL) 95-05, " Revisions to Staff Guidance for implementing NRC Policy on Notices of Enforcement Discretion,"
Revision 1, a NOED was requested during a teleconference between representatives of
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Commonwealth Edison (Comed) Company and the NRC on May 16,1999. The NOED 1 was subsequently approved by the NRC at approximately 1454 on May 16,1999. The NOED addresses non-compliance with the TS LCO 3.0.3 shutdown requirements for a period of 14 days. As committed to during the May 16,1999, teleconference and as provided in'AL 95-05, this letter provides the written follow-up NOED request. The
- enclosure provides the following information in accordance with AL 95-05:
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Description of the TS requirement for which enforcement discretion is sought; Circumstances surrounding the situation, including apparent root causes, the need for prompt action, and relevant historical background; The safety basis for the request, including an evaluation of the safety significance, and potential consequences, including a qualitative risk assessment, of the proposed action; Basis for determining that the noncompliance will not be of potential detriment to the public health and safety, and that no significant hazards consideration is involved; Basis for concluding that the request does not involve adverse consequences to the environment; Proposed compensatory actions; Justification for the duration of the request; Acknowledgement of Plant Operations Review Committee approval, and Basis for concluding that Notice of Enforcement Discretion (NOED) cnteria of NUREG-1600," General Statement of Policy and Procedures for NRC l Enforcement Actions," are satisfied.
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May 17,1999 U. S. Nuclear Regulatory Commission Page 3 Should you have any questions concerning this letter please contact T. W. Sirnpkin at (815)458 2801, extension 2980.
Respectfully, l
~.
othy J. Tulon ite Vice President Braidwood Station
Enclosure:
Written Follow-up of Request for Notice of Enforcement Discretion cc: Regional Administrator - NRC Region lil NRC Senior Resident inspector - Braidwood station l
' 1 ENCLOSURE BRAIDWOOD STATION UNIT 1 WRITTEN FOLLOW-UP OF REQUEST FOR NOTICE OF ENFORCEMENT DISCRETION CONCERNING THE EXTENSION OF THE SHUTDOWN REQUIREMENT OF LIMITING CONDITION FOR OPERATION 3.0.3 FACILITY OPERATING LICENSE NO. NPF-72 NRC DOCKET NO. STN 50-45G l
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l ENCLOSURE l Written Follow up of Roquest for Notice of Enforcement Discretion Concerning (
the Extension of the Shutdown Requirement of Limiting Condition for Operation 3.0.3 l l Page 1 of 9
'1. DESCRIPTION OF THE TECHNICAL SPECIFICATION REQUIREMENT OR LICENSE CONDITION FOR WHICH ENFORCEMENT DISCRETION IS SOUGHT Enforcement discretion is requested from compliance with the shutdown requirements of l b,3idwood Station, Unit 1, Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.0.3 resulting from the condition of an identified gas pocket in piping common to both Low Head Emerger: Core Cooling System (ECCS) trains.
TS Surveillance Requirement (SR) 3.5.2.3 requires the ECCS piping to be verified full of ;
water on o 31-day frequency. The purpose of this surveillance is to ensure that the ECCS l
, will perform properly when called upon by preventing water hammer, pump cavitation, and l the introduction of non-condensable gases into the Reactor Coolant System (RCS). This verification is done in pari by venting the system at the installed high point vent valves. In the event that the release of non-condensable gases is detected during this operation, specific portions of the piping (identified in the TS Bases) that have been identified as susceptible to collection of non-condensable gases which are not equipped with vent valves are ultrasonically examined to confirm a water solid condition. If during the performance of this surveillance a water solid as-left condition can not be achieved (i.e., venting can not be j performed), the affected ECCS trains must be declared inoperable and the associated !
! Actions entered. LCO 3.5.2, "ECCS-Operating," does not provide Actions for the condition of a' gas pocket identified in piping common to both ECCS trains. Therefore, LCO 3.0.3 must be immediately entered. LCO 3.0.3 requires that when an LCO is not met and an associated Action is not provided, the unit must be placed in a Mode or other specified condition in which the LCO is not applicable. This requires that action be taken within one hour to place the unit in Hot Standby within seven hours, Hot Shutdown within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and Cold Shutdown within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />.
- 2. CIRCUMSTANCES SURROUNDING THE SITUATION, INCLUDING APPARENT ROOT CAUSES THE NEED FOR PROMPT ACTION AND RELEVANT HISTORICAL BACKGROUND ,
The results of recent monthly ECCS venting operating surveillances,1BWOSR 3.5.2.2-2.
that were started on January 21,1999 March 18,1999, and April 16,1999, met the procedure acceptance criteria that the designated ECCS pump casings and piping were verified full of water. The surveillance conducted on February 18,1999 did observe a small gas bubble when venting from the vent valve 1Sl058A (RH Heat Exchanger 1 A Discharge Header to Loops 1 and 4 Cold Legs Vent Connection). Upon the follow-up Ultrasonic Testing (UT) inspection conducted on February 19,1999, no gas or air voids were identified at the 3 susceptible points, l
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ENCLOSURE Written Follow-up of Request for Notice of Enforcement Discretion Concerning the Extension of the Shutdown Requirement of Limiting Condition for Operation 3.0.3 Page 2 of 9 1
A timeline of subsequent events is as follows.
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- On May 13,1999 TS SR 3.5.2.3 was performed. This surveillance resulted in the {
identification of gas in the ECCS piping, and the affected train of ECCS was j
dec'ared inoperable. As a result, the susceptible ECCS discharge piping without i vent valves was ultrasonically examined. This examination identified an gas pocket approximately seven feet long and 3/4 inch deep (204 cubic inches) in the "B" train )
ECCS piping. The Actions of LCO 3.5.2 were entered at 2350 on May 13,1999 for the "B" train of ECCS inoperable. The associated Action (i.e., Required Action A.1) of LCO 3.5.2 requires the affected ECCS train to be restored within seven days.
10 remove the gas pocket, a design change was initiated to install a vent valve in the affected 'B" train ECCS piping. This design change was installed on May 15, 1999. During verification that the newly installed vent was successful in removing the gas pocket, the 3 susceptible piping sections were again ultrasonically examined. This examination revealed the new vent was successful in removing the onginal gas pocket. This examination also revealed a different gas pocket approximately 8.5 cubic inches in volume. This pocket is located in a section of piping necessary for either train of Low Pressure Safety injection to achieve j injection into all four RCS loops. Accordingly, both trains of ECCS were declared l inoperable putting the system outside of LCO 3.5.2. As a result, LCO 3.0.3 requiring a plant shutdown was entered at 0843 on May 16,1999.
The cause of the gas pocket may be attributed to backleakage of the Safety injection (SI) accumulators through the check valves, thus allowing the introduction of this water into the ECCS discharge piping. We have concluded that when depressurized, the gas came out of ,
solution, creating the observed gas pockets.
At that point in time, prompt action was required in order to maintain the unit in an operational mode, thus avoiding the undesirable effects caused by the thermal transient associated with a unit shutdown and subsequent cooldown.
- 3. EVALUATION OF THE SAFETY SIGNIFICANCE AND POTENTIAL CONSEQUENCES INCLUDING QUALITATIVE RISK ASSESSMENT OF THE PROPOSED ACTION The safety consequences associated with the small size of the gas pocket are minimal The identified gas pocket is approximately 8.5 cubic inches in volume. The effects of a pump start with a voided pipe have been previously evaluated and submitted to the NRC by letter dated June 10,1991., requesting a TS change for Braidwood Station and Byron Station.
Assuming a void of approximately 19.5 cubic feet, the waterhammer analysis demonstrated structuralintegrity of the piping. A separate study conducted by the Illinois Department of Nuclear Safety as part of its review of this TS change request, and submitted to the NRC by
ENCLOSURE I
l Written Follow-up of Request for Notice of Enforcement Discretion Concerning the Extension of the Shutdown Requirement of Limiting Condition for Operation 3.0.3 Pago 3 of 9 letter dated July 5,1991, indicated a critical void size of 12 cubic feet. Although piping integrity would not be challenged with a void of this size, the associated pressure transient upon a pump start could, according to the IDNS study, approach the discharge relief valve setpoint of 600 psi.
l Based on the previous analysis, limiting the allowable size of any gas pocket to approximately 10.0 cubic feet, provides reasonable assurance of continued piping integrity under both normal and transient conditions Accordingly, as a conservative measure we commit to limit the total amount of non-condensable gases in alllocations of the ECCS to 10 cubic feet for the duration of the NOED, A qualitative assessment of the effect of an additional 10 cubic feet of gas introduced into the RCS on the ECCS analysis has also been performed. This assessment concluded that there would be little or no impact on peak cladding temperature (PCT) during a Locs of l
Coolant Accident (LOCA). This assessment is based in part on the large volume of nitrogen assumed to be injected into the RCS concurrent with the discharge of the Si accumulators.
During the teleconference requesting the NOED, we committed to providing a more quantified assessment of this impact in the written follow-up.
The impact of 10 cubic feet of non-condensable gas introduced into the reactor coolant system (RCS) via the residual heat removal (RHR) pump during a design basis accident for l Braidwood Unit 1 Cycle 8 was evaluated. The safety assessment conducted (PCT l Evaluation dated May 16,1999) concluded the introduction of about 10 cubic feet of non-l condensable gas into the RCS via the RHR discharge line will not have any adverse impact on the large break LOCA PCT for Braidwood Unit 1 Cycle 8.
, The capability of a localized pocket of gas to restrict flow through the ECCS piping and l prevent the ECCS from meeting its design bases flow demands has been assessed.
In order for the gas pocket to remain in place as it is being compressed due to the l increased discharge pressure from the pump, the interfacing relative flow velocity must be
- low enough to prevent surface interaction between the air pocket and the water. This
! stable, smooth flow surface only exists in a laminar flow regime. The velocity at which the l water would be able to romain laminar below the gas pocket is much less than one ft/sec.
with laminar flow regime being defined as Reynolds number less than 2000 to 4000. At 1 l ft/sec, the Reynolds number is approximately 35,000 for an 8" Schedule 160 line, which is l
half filled with water. This would represent a flow rate of approximately 60 gpm. With the speed at which the pump starts and the resulting discharge pressure available, the flowrate l would increase to a level of turbulent flow with approximately 1-2 seconds. or less.
Additionally, the profile of the water front as it fills the high point of the piping during pump starts would in itself create an enveloping " wave" that would immediately start
( entraining / pushing the gas out of the pocket.
From the above, it can be seen that a stable, turbulent flow stream will be developed within a few seconds of pump start at the localized high points in the ECCS. As a result of this I
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1 ENCLOSURE Written Follow-up of Request for Notice of Enforcement Discretion Concerning the Extension of the Shutdown Requirement of Limiting Condition for Operation 3.0.3 Page 4 of 9 l
highly turbulent flow and the characteristic entrainment/ flushing of the gas pocket, there will be no significant change to the ability of the ECCS to provide flow to the core in the time frame assumed in the accident analyses.
The suction piping for the Residual Heat (RH) and SI systems are exposed to Refueling Water Storage Tank head, thus maintaining a positive net positive suction head (NPSH) for the pumps. Both the RH and Si pumps are equipped with casing vents, which are vented on a 31. day frequency.
The Centrifugal Charging (CV) pumps do not have casing vents, but the suction and discharge piping enter from the top of the pump casing, so the pumps are considered to be essentially self-venting. The suction piping of the CV system is normally in operation and either the Volume Control Tank or the Refueling Water Storage Tank provides NPSH.
On the morning of May 17,1999, two Operators, two Engineers and two Radiation
' Technicians entered the Braldwood Station Unit 1 Containment for the purpose of 1) venting ECCS lines, and 2) performing a UT inspection o' ECCS lines at susceptible locations l
where gas pockets may be present. Upon opening the high point vent valves, gas was released from the ECCS piping.
l Listed below are the lines that do not contain high point vent valves and that were UT inspected. There are two areas where the UT inspection showed a gas pocket. The l calculated gas volume is indicated for each.
1Sl05CB-8" 44 inches long with a depth of 1/2 inch 0.031 cu. ft.
l 1 S105CA-8" 120 inches long with a depth of 1/4 inch 0.03 cu. ft.
1 S105C A-8" 46 inches long with a depth of 1/4 inch 0.011 cu. ft.
(2nd area on same line) 1 Sl08HA-2" water solid i 1 Sl0SDA-6" water solid l 1S108FA-3" water solid 1S108GB-1 1/2" water solid 1 Sl18DB-4" water solid
! The total volume of these three gas pockets was calculated to be 0.072 cubic feet, which is I
significantly less than the 10 cubic feet acceptance criterion but will be accounted for in satisfying this criterion. Furthermore, the affect of these remaining gas pockets with respect to the TS requirernent to verify ECCS piping is filled with water is being evaluated and various options including TS or Bases changes based on the previously submitted water hammer analysis are being examined.
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ENCLOSURE i
Written Follow-up of Request for Notice of Enforcement Discretion Concerning j the Extension of the Shutdown Requirement of Limiting condition for Operation 3.0.3 )
1 Page 5 of 9 l
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- 4. BASIS FOR DETERMINING THAT THE NONCOMPLIANCE WILL NOT BE OF POTENTIAL DETRIMENT TO THE PUBLIC HEALTH AND SAFETY AND THAT NO SIGNIFICANT HAZARDS CONSIDERATION IS INVOLVED 1
We have evaluated this request for an NOED and determined that it involves no significant hazards consideration. According to the standards of 10CFR50.92(c), an NOED is determined to involve no significant hazards consideration if operation of the facility in accordance with the NOED would not; (1) Involve a significant increase in the probability of occurrence or the consequences of an accident previously evaluated; or I
(2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or l
(3) involve a significant reduction in a margin of safety.
The requested NOED does not involve a significant increase in the probability of occurrence or the consequences of an accident previously evaluated.
The probability of an evaluated accident is derived from the probabilities of the individual precursors to that accident. Voids in the ECCS discharge piping are not assumed as the initiator for events. As such, the presence of the small gas pockets does not contribute to the overall probability of occurrence of an event. The consequences of an evaluated accident are determined by the ability of plant systems to mitigate those consequences.
The requested NOED is based on the continued ability of the ECCS systems to respond and mitigate the effects of applicable design basis events. The prevailing condition does not impair the assumed function of the ECCS systems. Our evaluation concluded that the addition of a small amount of entrapped gas to that already assumed to be introduced into the RCS will not affect the analyzed outcome of the transient. Therefore, this NOED does not affect the ability of plant systems to mitigate the consequences of an accident previously evaluated.
The requested NOED does not create the possibility of a new or different kind of accident from any accident previously evaluated.
Creation of the possibility of a new or different kind of accident would require the creation of one or more new precursors of that accident. .New accident precursors may be created by modifications to the plant configuration, including changes in allowable modes of operation This NOED does not involve the introduction of new equipment, and installed equipment will continue to be operated in a manner consistent with its design. No new precursors of an accident are created and no new or different kinds of accidents are created.
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ENCLOSURE l l
Written Follow-up of Request for Notice of Enforcement Discretion Concerning the Extension of the Shutdown Requirement of Limiting condition for Operation 3.0.3 4 Page 6 of 9
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l This NOED allows the operation of Unit 1 with small gas pockets present in the ECCS discharge piping. The effects of the voiding have been specifically analyzed to ensure i piping integrity upon a pump start with a significantly larger void than that currently observed. The effect on calculated PCT has also been evaluated and determined to be minimal. These evaluations and the continued operation of the plant equipment in a manner consistent with its design are sufficient to ensure no new or different kind of accident is created. Therefore, the requested NOED does not create the possibility of a new or different kind of accident from any accident previously evaluated.
The requested NOED does not involve a significant reduction in a margin of safety.
The margin of safety is based on the ECCS performing its safety function to m!tigate the consequences of certain accidents. Allowing the continued operation of the unit for a period of fourteen days is contingent on the proposed compensatory measures described below.
These measures will ensure that the ECCS piping will be sufficiently filled with water to maintain all ECCS design and safety functions. Therefore, the ability of the ECCS to 4 successfully fulfill its function to cool the core is not changed by this NOED. Specifically, the proposed compensatory measures will provide for a more frequent verification of discharge '
piping conditions, assuring operability. Thus there is no reduction in the margin of safety.
- 5. BASIS FOR CONCLUDING THAT THE REQUEST DOES NOT INVOLVE ADVERSE CONSEQUENCES TO THE ENVIRONMENT We have evaluated this NOED against the criteria for identification of licensing and regulatory actions requiring environmental assessment in accordance with 10 CFR 51.21.
We have determined that this requested action meets the criteria for a categorical exclusion set forth in 10 CFR 51.22(c)(9) and, as such, have determined that no irreversible consequences exist in accordance with 10 CFR 50.92(b). This determination is based on the fact that this is an NOED relative to a license issued pursuant to 10 CFR 50, that reflects a requirement with respect to the use of a facility component located within the restricted area, as defined in 10 CFR 20, and the action meets the following specific critena (i) The proposed action involves no significant hazards consideration. As demonstrated in Section 4 of this enclosure, this NOED does not involve any significant hazards consideration.
(ii) There is no significant change in the types or significant increase in the amounts of any effluent that may be released offsite. The NOED does not affect the generation of any radioactive effluent. The NOED would allow the operation of Unit i for a period of time with the ECCS discharge piping not water solid. As explained above, we have l
j ENCLOSURE i 1
Written Follow-up of Request for Notice of Enforcement Discretion Concerning !
the Extension of the Shutdown Requirement of Limiting Condition for Operation 3.0.3 l l
Page 7 of 9 l
concluded that plant equipment would operate as expected in the event of an accident to minimize the potential for any leakage of radioactive effluents. l 1
(iii) Thero is no significant increase in individual or cumulative occupational radiation exposure. The weekly occupational radiation exposure impact of the cornpensatory measures for venting and UT of the ECCS piping is estimated to be 83 mrem. The proposed action will not change the level of controls or methodology used for processing of radioactive effluents or handling of solid radioactive waste, nor will the I proposed action result in any change in the normal radiation levels within the plant.
Therefore, there will be no significant increase in individual or cumulative occupational ,
radiation exposure resulting from this change. )
l
- 6. PROPOSED COMPENSATORY ACTIONS 1 Venting of ECCS piping outside containment will be performed weekly. Ultrasonic testing of l susceptible ECCS piping outside containment without vents will also be performed weekly.
! Venting of ECCS piping inside containment, which is not now performed, will be conducted on a weekly basis.
The isometric drawings of ECCS piping inside containment were evaluated to determine the susceptible piping without vents. Each of the unvented high points are listed in item 3, and were UT inspected. All unvented high points are accessible, and will be subjected to weekly UT inspection.
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The Unit 1 Sl accumulator water level makeup frequency will continue to be trended. The Operations Department willinform System Engineering whenever water addition to the Unit 1 accumulators is required. If the frequency of Si accumulator makeup increases by more than 50% over the current trends, the frequency of the ECCS surveillance described above will be increased. This frequency will be increased from weekly to twice weekly.
If gas pockets or volds are identified which total greater than 10 cubic feet, the unit will proceed with the shutdown.
All crews will be briefed on the situation and all work schedules will be reviewed and work on the ECCS trains will be minimized.
- 7. JUSTIFICATION FOR THE DURATION OF THE REQUEST Based on the previous analysis, limiting the allowable size of any gas pocket to approximately 19.5 cubic feet, provides reasonable assurance of continued piping integnty under both normal and transient conditions. Accordingly, as a conservative measure, the total amount of non-condensable gases in all locations of the ECCS will be limited to 10
,u., ,
oi. v, . . . , . . . . . . . , . ... .. ... , . . . . .
e l ENCLOSURE Written Follow-up of Request for Notice of Enforcement Discretion Concerning the Extension of the Shutdown Requirement of Limiting Condition for Operation 3.0.3 Page 8 of 9 cubic feet for the duration of the NOED. A qualitative assessment of the effect of an additional 10 cubic feet of gas introduced into the RCS on the ECCS analysis concluded )
that there would be little or no impact on PCT during a LOCA. The requested 14 day j duration of the NOED will provided sufficient time to procure the necessary parts and I perform the engineering work associated with resolving this issue. Actions are in progress j to add vent valves at the two remaining susceptible locations outside containment. i Therefore, given the low risk significance of the NOED and the compensatory measures being taken, the short duration of the NOED is justified.
- 8. ACKNOWLEDGEMENT OF PLANT OPERATIONS REVIEW COMMITTEE APPROVAL This request has been reviewed and approved by the Braidwood Station Plant Operations <
Review Committee (PORC) to meet the requirements of station administrative procedures.
- 9. BASIS FOR CONCLUDING THAT THE NOTICE OF ENFORCEMENT DISCRETION j (NOED) CRITERIA OF NUREG-1600," GENERAL STATEMENT OF POLICY AND PROCEDURES FOR NRC ENFORCEMENT ACTIONS," ARE SATISFIED We have evaluated the NOED against the criteria specified in NUREG-1600. We have !
determined that the NOED meets the criteria for an operating plant. This determination is based on the avoidance of an undesirable transient caused by the shutdown of the reactor l as a result of forcing complia.nce with the TS LCO 3.0.3 and, thus, minimizes potential operational risks associated with a plant shutdown. i
- 10. MARKED-UP TECHNICAL SPECIFICATION PAGES IDENTIFYING PROPOSED CHANGES (IF APPLICABLE)
There are no changes to the Technical Specification as a part of the NOED.
- 11. OTHER SUPPORTING INFORMATION.
Braidwood Station PORC Members involved in the review and approval of this NOED request on May 16,1999 were as follows.
Keith Schwartz Braidwood Station Manager Tom Luke Engineering Manager Richard Graham Work Control Manager Mike Riegel Nuclear Oversight Manager Terrence Simpkin Regulatory Assurance Manager Frank Lentine Design Engineering Manager Mark Trusheim Operations Engineer
.