HBL-05-005, Response to NRC Request for Additional Information Regarding License Amendment Request 04-02, Spent Fuel Cask Handling (TAC L52634). Calculation File No. PRA04-08 Enclosed

Response to NRC Request for Additional Information Regarding License Amendment Request 04-02, Spent Fuel Cask Handling (TAC L52634). Calculation File No. PRA04-08 Enclosed

ML051660414
Person / Time
Site:	Humboldt Bay
Issue date:	06/03/2005
From:	Jacobs D Pacific Gas & Electric Co
To:	Document Control Desk, NRC/FSME
References
HBL-05-005, TAC L52634 PRA04-08
Download: ML051660414 (18)

Text

Pacific Gas and ElectricCompany Donna Jacobs Diablo Canyon Power Plant Vice President P.0. Box 56 Nuclear Services Avila Beach, CA 93424 June 3, 2005 805.545:234 PG&E Letter HBL-05-005 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-133, OL-DPR-7 Humboldt Bay Power Plant, Unit 3 Response to NRC Request for Additional Information Regarding License Amendment Request 04-02, "Spent Fuel Cask Handling" (TAC NO. L52634)

Dear Commissioners and Staff:

On July 9, 2004, Pacific Gas and Electric Company (PG&E) submitted License Amendment Request (LAR) 04-02, Spent Fuel Cask Handling, in PG&E Letter HBL-04-016. LAR 04-02 requested a license amendment to allow the handling and loading of Holtec International's multi-purpose canisters and overpack in the Humboldt Bay Power Plant, Unit 3, 10 CFR 50 facilities.

By letter dated December 9, 2004, the Nuclear Regulatory Commission (NRC) staff requested additional information needed to continue their review of LAR 04-02.

The NRC staff verbally requested additional information on March 30, and April 28, 2005. Provided as Enclosure 1 is PG&E's response to the requests for additional information. PG&E probabilistic risk assessment calculation, PRA-04-08, is provided as Enclosure 2.

If you have any questions regarding this response, please contact Mr. Terence Grebel at (805) 545-4160.

Sincerely, emb/3522 Enclosures cc: PG Fossil Gen HBPP Humboldt Distribution cc/enc: James R. Hall John B. Hickman Eric Lewis HrY)sstej

PG&E Letter HBL-05-005 a

UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION Docket No. 50-133 In the Matter of ) Facility Operating License PACIFIC GAS AND ELECTRIC COMPANY) No. DPR-7 Humboldt Bay Power Plant )

Unit3 )

AFFIDAVIT I, Donna Jacobs, being of lawful age, first being duly sworn upon oath say that I am Vice President, Nuclear Services of Pacific Gas and Electric Company; that I have executed this response to an NRC request for additional information regarding Humboldt Bay Power Plant, Unit 3, License Amendment Request 04-02, "Spent Fuel Cask Handling" dated June 3, 2005, that I am familiar with the content thereof; and that the facts stated therein are true and correct to the best of my knowledge, information, and belief.

Donna J ~obs Vice Presid nt Nuclear Services Subscribed and sworn to before me on this 3rd day of June, 2005, by Donna Jacobs, personally known to me or proved to me on the basis of satisfactory evidence to be the person who appeared before me.

Notary Public Coimmbdonl U 142 State of California Noofry Pu~Ic - Caltomia County of San Luis Obispo ItLEOhSpoi1B.OI Son

Enclosure 1 PG&E Letter HBL-05-005 Page 1 of 9 PG&E Response to NRC Request for Additional Information Regarding License Amendment Request 04-02, "Spent Fuel Cask Handling" NRC Question I The Holtec Humboldt Bay Davit Crane Specification (submitted to NRC as an attachment to the 08/17/04 PG&E letter HBL-04-022) page 3 states "The two strand jacks operating in parallel combine to raise the total working load to 264 tons." Page 7 of 22 of the NUREG-0554/NUREG-0612 Compliance Matrix states, 'The strand jack collets automatically adjust for slack in any individual stand so that the strands will be evenly loaded."

1. Describe how these two standjacks automatically operate in unison to lift the load evenly.

2. Describe means to correct uneven lifting if such problem is discovered.

3. Describe the effect of uneven loading on the ability of the crane to stop and hold the load and to what extent stresses in load bearing members were evaluated for uneven loading conditions.

PG&E Response to Question I

1. The jacks are precision-machined devices, which are factory and field tested to ensure uniform movement through the entire range of the lift. Each jack has an identical stroke length. During each lifting cycle, all jacks are cycled in unison through their full range. The cycle is not complete until all jacks have reached their full extension. The hydraulic pump system injects fluid into each jack.

Hydraulic fluid naturally follows to the path of least resistance. Assuming that one jack were to attempt to lag behind the other jacks, fluid, following the path of least resistance, would instantaneously flow to the lagging jack until the jack pressure matched the remaining jacks, thus bringing all jacks back into equilibrium. At the top of the stroke, all three jacks would automatically top-out bringing all six jacks back into phase. This feature will be tested as part of the start-up test program.

2. Uneven lifting of the load is not possible with the davit crane. The connection between the strand anchor block and the lift yoke is via a single, centrally located pinned connection, which allows the lift yoke to pivot. The pivoting ability of the strand anchor block maintains the same load on each strand-jack. -In the non-credible event that one strand jack were discovered to be significantly lagging, the strand jack drive system has a locked-out bypass mode by which the "slack side" can be individually advanced to bring the system back into full balance.

This bypass capability is necessary to balance the system during the initial set-

Enclosure I PG&E Letter HBL-05-005 Page 2 of 9 up of the davit crane. Prior to each lift, the system is visually examined and tested to verify that the jacks are operating in unison and the load is evenly balanced.

3. As described above, uneven lifting of the load is not possible with the davit crane. In light of this, no specific inclusion of uneven loading was made in the design analysis. The individual parts were designed with a significant safety factor, and as such, in the non-credible event of some uneven loading, an overstress condition is unlikely.

NRC Question 2 The Holtec Humboldt Bay Davit Crane Specification (submitted to NRC as an attachment to the 08/17/04 PG&E letter HBL-04-022) page 4, 5.3 states that

'hydraulic pressure in the strandjacks is regulated to protect against a 'two-blocking" event." Page 8, item g 'limit switch failure" of the same report states "The effect of one of the redundant independent limit switches to stop the lift prior to "hard contact" of the Davit Crane members would be that the hydraulic pressure relief valves would limit the lift force." Page 11 of 22 of the NUREG-0554/NUREG-0612 Compliance Matrix Section 4.5, item 2 Compliance Evaluation states that "The protective control system will use two independent upper and two independent lower limit switches. These devices are independent of the drive control system."

1. Describe how the hydraulic pressure is regulated/relieved. Please include a discussion on the failure of such mechanism because this failure is not included in Section 7 "Davit Crane and Strand Jack Failure Modes and Effects Analysis".

Are manual actions required? If so, briefly describe the complexity of the manual actions.

2. Describe how the switches function and how they are independent from each other and from the drive control system. What is the sequence of events when one (or both) switch is activated?

PG&E Response to Question 2

1. The hydraulic system used to control the strand jacks is similar to the system used to control the davit positioning cylinders. Both systems employ the use of counterbalance valves to regulate and relieve hydraulic pressure on the systems.

The regulator relief setting of the counter balance valve corresponds to an available lift force in the jacks. Pressure is regulated such that the limiting lift force in the jacks equals the load, plus some small amount (e.g., 10 percent to 20 percent). The pressure relief exhaust directs hydraulic pressure back to the reservoir. Refer to PG&E Response to Question 3 for a detailed description of the counterbalance valves and the corresponding schematics.

Enclosure 1 PG&E Letter HBL-05-005 Page 3 of 9 The pressure relief settings of the counter balance valves will enable the system to detect a two-block event or a load hang-up event. This detection will prevent the jacks from exerting a force sufficient to damage themselves, the cask, or any of the load handling components. Redundant pressure relief valves will ensure complete protection of the system. The pressure relief valves provide a third and fourth level of defense, following the upper and lower limit switches, and do not require any manual actions to operate.

2. The switches are simple electronic paddle-type switches that send a signal to the programmable logic control (PLC) to stop the lifting actions once the load reaches its full-up position. There is one PLC to control all functions. The two limit switches are positioned at different locations on the davit crane to detect if the load is approaching its upper limit. Each switch sends a separate signal to the PLC on the control system. If either signal is detected, the PLC stops the lifting cycle. The limit switches do not require any type of hydraulic feedback circuit in the drive system to operate.

NRC Question 3 The Holtec Humboldt Bay Davit Crane Specification (submitted to NRC as an attachment to the 08/17/04 PG&E letter HBL-04-022) pages 11 thru 13 of 22, addressing the NUREG-0554/NUREG-0612 Compliance Matrix Sections 4.5 and 4.9, states that aThe Davit Crane does not employ holding brakes. Stopping and holding are passive safety features of the hydraulics."

1. Describe the passive safety features of the hydraulics. In particular, how it stops and holds the load. Also, describe how dynamic effects from the jacking are controlled and were considered in the design of load-bearing elements.

2. Describe the dynamic effects on the system from other postulated sudden movements. For example, upon loss of hydraulic power (e.g., rupture of a hydraulic line), what is the impact on the system/load when the two vertical booms fall suddenly from a vertical position (90°) to a fully extended position over the spent fuel pool? Can the Davit Crane be manually brought to a safe state upon loss of power?

3. Describe how the effects of wear and the resulting reduction in frictional load holding capacity will be monitored and controlled during the life of the crane.

Additional questions from NRC staff on March 30, 2005:

4. Response I states, "Adynamic adder of 15 percent was selected for structural evaluation of the Davit Crane components. " What is the basis for selecting the

Enclosure 1 PG&E Letter HBL-05-005 Page 4 of 9 dynamic adder of 15 percent?

5. Response 2 states, "The counter-balance valves lock up every time the crane is stopped. Catastrophic failure of a hydraulic line or loss of hydraulic power does not impart additional loads to the system. In the event of a catastrophic hydraulic system line failure (Line 2) during a load lift, the reverse flow of fluid is prevented by the check valve, thus locking the cylinder in position. " What is the reason for not postulating a catastrophic failure of line 1 or 3? If line I fails, what mechanism is there to prevent a load drop? If line 3 fails, what mechanism is there to prevent an acceleration of the load?

Additional questions from NRC staff on April 28, 2005:

6. The response to Davit Crane 3 should be expanded to clarify the interaction between the pistons on each side of the crane. That is, what is the potential for the piston on one side to respond differently from the other given a single hydraulic line break?

What controls the speed of retraction of the piston? If Line B catastrophically falls during retraction, what mechanism is available to control the speed of retraction of the piston?

PG&E Response to Question 3

1. The davit crane hydraulic positioning cylinders are similar to the lifting jacks used as components of the strand jacks. Both positioning jacks are equipped with counter-balance valves, which passively protect the hydraulic systems by requiring hydraulic pressure in the line to enable extending or retracting the jacks. Counterbalance valves, also known as motion-control valves and over-center valves, are commonly used to control an overrunning load or prevent uncontrolled excursion of a hydraulic cylinder. A typical counterbalance valve schematic is shown in Figure 1 of this response and uses three ports to control the fluid flow to the cylinder. In the counterbalance valve, fluid is free to flow from Port 2 to Port 1. A check valve is in place to prevent reverse flow of the fluid from Port 1 to Port 2. Fluid flow from Port 1 to Port 2 is only allowed through the pressure regulator if hydraulic pressure is provided at Port 3 or if the pressure at Port 1 exceeds the relief valve setting. (The non-piloted portion of the pressure relief valve setting is set to a minimum of 1.3 times the maximum lifted load and is incorporated only as.a self-protecting feature.) Fluid flowing from the pump to the extend side of the double-acting hydraulic cylinders cause the cylinders to extend and lift the load (see Figure 2). Fluid flow out of the extend side is blocked by the check valve in the counterbalance valve. To retract the cylinder, hydraulic fluid pressure must be applied to the retract side of the cylinder. The retract pressure is sensed by Port 3 of the extend side

Enclosure 1 PG&E Letter HBL-05-005 Page 5 of 9 counterbalance valve, which opens the pilot operated relief valve, and fluid is allowed to flow from the extend side of the cylinder back to the reservoir, allowing the cylinder to retract.

FIGURE 1:

COUNTERBALANCE VALVE SCHEMATIC The jacks and hydraulic jack systems are sized such that all movement is very slow compared to an electric overhead crane. The speed of travel is less than 12 inches per minute for both the strand jack motion and the davit positioning cylinders. This travel speed is controlled by the equipment sizing, and is not adjustable by the equipment operator.

2. The counterbalance valves in Figure 2 of this response protect the system against additional loads imparted due to catastrophic failure of any hydraulic line or loss of hydraulic pressure. As discussed below in Section 5 of this response and in accordance with Figure 2, the hydraulic lines are labeled as Line A for the retract side and Line B for the extend side. In the event of a catastrophic hydraulic line failure (Line B) during a load lift, the reverse flow of fluid is prevented by the check valve, thus locking the cylinder in position. In the event of a catastrophic hydraulic system line failure (Line A) during load lowering, the loss of pressure is seen by Port 3, causing the relief valve to close, thus locking the cylinder in position. A lock-up of the counter-balance valves causes the crane to make a normal stop and remain in a safe condition (stops where it is) without any manual actions. All active lifting components are accessible and can be repaired or replaced with a load on the crane and without risk of a load drop.

The davit crane relies on two identical pivot cylinders that pivot the boom from a negative angle to a positive angle under load. The davit crane pivot cylinders must provide drop protection against four distinct drop cases:

Enclosure 1 PG&E Letter HBL-05-005 Page 6of9 Case 1: Catastrophic Hydraulic Pressure Loss (Line B) During Cylinder Extension - Boom Before Top Dead Center Case 2: Catastrophic Hydraulic Pressure Loss (Line B) During Cylinder Extension - Boom Traveled Beyond Top Dead Center Case 3: Catastrophic Hydraulic Pressure Loss (Line A) During Cylinder Retraction - Boom Before Top Dead Center Case 4: Catastrophic Hydraulic Pressure Loss (Line A) During Cylinder Retraction - Boom Traveled Beyond Top Dead Center Shown in Figure 2 is a simplified schematic of a davit crane pivot cylinder and the two counterbalance valves. Line A provides pressure to Port 3 of the extend side counterbalance valve and Port 2 of the retract side counterbalance valve.

Line B provides pressure to Port 2 of the extend side counterbalance valve and Port 3 of the retract side counterbalance valve. In Case 1 the load attempts to retract the cylinder to its fully closed position. The absence of pressure in Line A on the retract side prevents the extend side counterbalance valve from opening (extend side counterbalance valve locks up), thus preventing cylinder retraction.

The counter balance valve does not open since there is no pressure seen at Port 3 of the extend side counterbalance valve. In Case 2 the load attempts to extend the cylinder to the fully open position. The sudden loss of pressure in Line B is sensed by retract side Port 3 and prevents fluid from exiting the retract side preventing further cylinder extension. In Case 3 the load attempts to extend the cylinder to its fully extended position. The check valve in the retract side counterbalance valve prevents the hydraulic fluid from flowing out of the retract side of the cylinder, and therefore prevents the cylinder from any further extension. In Case 4 the load attempts to retract the cylinder to its fully closed position. The sudden loss of pressure in Line A is sensed by extend side Port 3 and prevents fluid from exiting the extend side. The failure of the return line in any of the four cases does not result in any loss of control of the load, as the counterbalance valves will continue to control the travel at the designed speed.

It is important to note that the counterbalance valves are directly mounted to the cylinder. Directly mounting the counterbalance valves to the cylinder eliminates the potential for a line failure at the cylinder hydraulic connection.

In all cases, the cylinder is protected against a catastrophic line failure.

Additionally, the three-way valve shown in Figure 2 prevents pump pressure from reaching the retract side and extend side simultaneously.

Enclosure 1 PG&E Letter HBL-05-005 Page 7 of 9 EXTEND UNE B PRESSURE -

RETURN - - UNE A RETRACT n3 2 3 -

FIGURE 2:

DOUBLE-ACTING COUNTERBALANCE VALVE SYSTEM FOR THE DAVIT CRANE

3. As described in License Amendment Request 04-02, Section 4.2.1.2 (Reference PG&E Letter HBL-04-016, dated July 9, 2004), the strands are rated for loads significantly larger than design davit crane load (264 ton vs. 95 ton). The strand service life is also rated well beyond that expected by the davit crane. The manufacturer's recommended life is several hundred lifts, and the required lifting is six casks. Even with several test loads, this is a small fraction of the expected life. However, the strands will be inspected prior to each lift for wear and replaced, if required, per the manufacturer's recommendations. Per the strand jack manufacturer, the collet chucks last for the life of the unit. Most users are heavy equipment installation specialists and they have had chucks in service for over 15 years. The chuck teeth are case hardened to Rockwell 60 with core hardness of 35.

4. NUREG-0554 Section 2.2, Item 1,states, "A single failure-proof crane should be designed to handle the maximum critical load that will be imposed. However, a slightly higher design load should be selected for component parts that are subjected to wear and exposure. An increase of approximately 15 percent of the design load for these components would be a reasonable margin." In accordance with this guidance, a dynamic adder of 15 percent was selected for structural evaluation of the davit crane components.

Enclosure 1 PG&E Letter HBL-05-005 Page 8 of 9

5. An updated vendor schematic (Figure 2) has been integrated into the hydraulic discussion (Item 2) above to address catastrophic failure of hydraulic lines.

Figure 2 has been updated to clarify that there are only two hydraulic lines (Line A and Line B) associated with each positioning jack and that there are three ports to each of the counterbalance valves. Hydraulic lines previously labeled 1, 2, and 3, have been relabeled as Line A for the retract side and Line B for the extend side, and the counterbalance valve ports are now clearly labeled as ports 1,2, and 3. As discussed in Item 2 of this response, Port 1 of the counterbalance valve is directly mounted to the cylinder. There is no hydraulic line between Port 1 of the counterbalance valve and the cylinder, which negates the possibility of a line burst at this location. All postulated catastrophic hydraulic line failures have been addressed above in Item 2.

6. The hydraulics feeding the pivot cylinders are metered using a flow divider. The flow divider evenly distributes hydraulic fluid to each pivot cylinder to maintain uniform movement. In addition to the flow dividers, each pivot cylinder is equipped with a cylinder positioning system (CPS), which employs magnets embedded in the cylinder rods. As the cylinders extend and retract, these magnets pass by a sensor that monitors the position of each cylinder. The CPS continuously monitors and compares the position of each cylinder rod as it is extends and retracts. The CPS is hooked into the PLC of the davit crane and will lock up the cylinders if any "out of balance" condition occurs. A locked bypass switch allows the operator to equalize the cylinders if needed.

As stated previously in 2 above, cylinder travel speed is ultimately limited by the orifice size in the counterbalance valves. A catastrophic failure of Line B during retraction causes return fluid to be expelled from the system. This would still allow the cylinder to operate. However, the counterbalance valves would still function and prevent a loss of control situation.

NRC Question 4 Page 18 of 22 of the NUREG-0554INUREG-0612 Compliance Matrix Sections 6.6 item 1 Compliance Evaluations states that 'An O&M manual will be provided with the Davit Crane." That statement did not directly address the location of operating and emergency controls issue.

Describe the location of operating and emergency controls. Are they located on or near the crane where the crane operator can directly observe the crane movement?

Enclosure I PG&E Letter HBL-05-005 Page 9 of 9 PG&E Response to Question 4 Operating and emergency controls will be at the location of the hydraulic skid, which is adjacent to the crane and where the crane movement may be directly observed.

NRC Question 5 Page 49 of 68 of the Enclosure to the PG&E Letter HBL-04-016 (July 9, 2004) states that "This probabilistic evaluation determined that the probability of a cask drop causing a radiological release exceeding the guidelines of 10 CFR or a criticality event was less than 1x10-7 and therefore was not credible."

Describe the sequence of events that led to the cask dropping and how the cask dropping probability was determined. In particular, please focus on the areas where either human actions or hardware failures were involved.

Additional question from NRC staff on March 30, 2005 Please confirm that in "the probability of a cask drop causing a radiological release exceeding the guidelines of 10 CFR or a criticality event was less than 1x10-7', the probability given is per lift.

PG&E Response to Question 5 The cask dropping probability was determined by performing a probabilistic risk analysis (PRA) using NUREG-0612 Appendix B probabilistic techniques and associated human actions and hardware failures, and supplemented with updated cask drop reliability information in NUREG-1774. The PRA is consistent with the risk evaluation in NUREG-1738. The PRA used the Humboldt Bay ISFSI specific number of cask handling activities (16 lifts) and assumed a non-mechanistic drop.

The resultant release probability is 8.96 E-9, which is well under the I E-7 threshold.

Humboldt Bay Power Plant (HBPP), Unit 3, Defueled Safety Analysis Report Appendix A previously evaluated the potential of exceeding 10 CFR 100 from potential HBPP accidents, including the non-mechanistic failure of the spent fuel pool. NRC SER, Section 10.2, dated April 29, 1987, concluded that 10 CFR 100 would not be exceeded during any of these potential accidents. This evaluation bounds any offsite consequences from a cask drop accident.

Editorial correction: PG&E Letter HBL-04-016 incorrectly references the probabilistic evaluation of the davit crane as PRA-04-01; the correct PRA number is PRA-04-08.

PRA-04-08 is provided as Enclosure 2 of PG&E Letter HBL-05-005.

Enclosure 2 PG&E Letter HBL-05-005 PG&E Probabilistic Risk Assessment Calculation File No. PRA04-08, "Risk Assessment of Heavy Load Movements inside the Humboldt Bay Power Plant Refueling Building"

PACIFIC GAS & ELECTRIC COMPANY PROBABILISTIC RISK ASSESSMENT CALCULATION FILE NO. PRA04-08

SUBJECT:

Risk Assessment of Heavy Load Movements Inside the Humboldt Bay Power Plant Refueling Building PREPARED BY: /4fr DATE:______

Ph. Ale e ten '

VERIFIED BY: DATE: 747/ °'4 VERIFIED IN ACCORDANCE WITH: CF3.1D15 APPROVED BY: ___ A_ _ DATE: ___ 9__

___4

&.rgto J zoL.r This file contains: 6 pages

CALCULATION FILE PRA04-08 Sheet 2 RECORD OF REVISIONS REV. 0 Original Calculation.

INTRODUCTION As part of being able to decommission, Humboldt Bay Power Plant (HBPP) will have to unload its spent fuel assemblies from the spent fuel pool (SFP). HBPP is planning to place its spent fuel in storage/shipping casks, which has an integral multi-purpose canister (MPC). This assembly is referred to as a HI-STAR in this analysis. Once a HI-STAR is loaded it will be stored in an onsite independent spent fuel storage installation (ISFSI). To be able to store the spent fuel in the HI-STAR, HBPP will have to place a HI-STAR in the cask pit area located in the SFP. Each of these HI-STARs will be placed in and taken out of the SFP with a specially designed 95-ton rated davit crane installed in the Refueling Building (RFB). This davit crane will be designed to meet NUREG-0612 (Reference 1) single failure proof requirements, as applicable. The davit crane uses a strand jack mechanism for the lifting of the cask. In addition, while the HI-STAR is in the cask pit area, the MPC lid may be put into place with the existing 10-ton rated RFB crane, once the spent fuel has been placed into the MPC.

DISCUSSION NUREG-0612 (Reference 1) Appendix B provides guidance for acceptable estimates of event probabilities for loads handled near and over a spent fuel pool with the use of both standard and single failure proof cranes. These acceptable probabilities are ultimately the probability for consequences of a load drop exceeding the guidelines of twenty five percent of the 10 CFR 100 limits. This analysis was performed using NUREG-0612 Appendix B probabilistic techniques and supplemented with updated cask drop reliability information in NUREG-1 774 (Reference 2), and is consistent with the risk evaluation in NUREG-1738 (Reference 3). The design of the davit crane and strand jack system will meet the following criteria as applicable: (1) NUREG-0612, (2) NUREG-0554, and (3)ANSI N14.6.

The existing RFB crane was designed and built to industry standards equivalent to ANSI B30.2. The 10-ton auxiliary hook has been consistently maintained in good working order including periodic load testing. The 10-ton auxiliary crane may be used for handling the MPC lid. The use of the auxiliary crane for handling the MPC lid will provide at least a 10:1 safety factor to ultimate capacity.

Both the davit and RFB crane will meet NUREG-0612 Section 5.1.1 guidance. The davit crane has certain design features that meet the requirements for single failure proof cranes, but for conservatism, these features will not be credited and this crane will be assessed by standard crane failure probabilities. This analysis is a risk assessment of a mechanical failure, exclusive of seismic events, during a heavy loads movement with the davit or RFB crane over the SFP.

CALCULATION FILE PRA04-08 Sheet 3 ACCEPTANCE CRITERIA NEI 96-07 Revision 1, "Guidance for 10 CFR 50.59 Implementation", (Reference 4) provides guidance which indicates that if the frequency of occurrence of an accident remains below 1 E-6 per year, then it is considered to be a minimal increase in risk.

However, since an accident in this analysis could result in a direct release, the acceptance criterion is reduced by factor of 10. This acceptance criteria is consistent with the NUREG 1.174 low risk significance criterion for the LERF figure for merit.

ASSUMPTIONS and ASSERTIONS

1. The davit crane has design features that meet the requirements of a single failure proof crane, for conservatism these features will not be credited.

2. As part of initial testing and inspection of the davit crane at HBPP, a functional test will be performed consisting of the davit crane lifting a test load off of the refueling building floor, but will not carry this load over the SFP. For conservatism this load will be counted as a single load lifted over the SFP in this analysis.

3. There will be a total of 5 HI-STARs individually loaded with spent fuel assemblies.

Each of these HI-STARs will be brought into the RFB and picked up by the davit crane and lowered into the SFP cask pit. Once a HI-STAR is placed on the bottom of the cask pit the davit crane is detached from the HI-STAR and the HI-STAR is loaded with spent fuel. Once the HI-STAR is loaded the MPC lid is placed into position. This activity will be counted as 5 lifts during the entire loading campaign at HBPP, in this analysis. Once the MPC lid is restrained in place, the davit crane is reattached to the HI-STAR, raises the HI-STAR out of the SFP, and places it on the RFB floor. Therefore the loading of each HI-STAR with fuel will be counted as two lifts. Conservatively counting the functional test lift, as a load over the SFP, and the 5 MPC lid lifts, there will be a combined total of 16 planned lifts performed by the davit and RFB cranes during the entire fuel loading campaign at HBPP.

4. Due to the design of the davit crane there are no scenarios when the davit crane can leave its designed load path.

5. At no time does the davit crane load path pass over spent fuel.

6. The RFB crane will be administratively controlled so that it will only bring an MPC over the cask loading pit and not over the spent fuel storage racks.

7. All of the spent fuel stored in the SFP has been stored there for a minimum of 29 years. By the standards set by NUREG-0612 (Reference 1) Section 2.1, the SFP does not contain any "hot" spent fuel.

8. Per Appendix B of NUREG-0612 the probability of a load falling in an orientation to cause criticality is believed to be between 1 E-1 and 1 E-3. It is judged that this

CALCULATION FILE PRA04-08 Sheet 4 probability is significantly lower for Humboldt Bay cask loading activity on the basis that all of the fuel in the SFP pool is stored in Boral cans in the spent fuel storage racks or in a HI-STAR, which contains a fuel basket lined with neutron absorbers.

Therefore, conservatively it is judged that the probability of a load falling in a way to cause criticality is 1 E-5, a factor of 100 lower than the NUREG's probability.

9. The total time for all of the heavy load movements to be completed will take no longer than one year.

CALCULATIONS Per the guidance of NUREG-0612 Appendix B and Figure B-1, determination of the probability of exceeding NUREG-0612 guidelines requires the consideration of the accidents, which could result in exceedance of twenty five percent of 10 CFR 100 offsite release limits and/or could cause criticality. In evaluating the potential for exceedance of offsite limits, load drop on spent fuel and load drop causing pool failure were evaluated. Load drop on spent fuel, handling system failures and time over the SFP were considered. For the criticality potential, the contents of the SFP, a handling system failure, load failure causing fuel damage in the SFP, and the load falls in an orientation that causes criticality.

The following discussions are numbered to correspond with the fault tree contained in Figure 1 of this analysis, which reflects the format of NUREG-0612 Appendix B.

2.1 Off Site Releases Exceed Guidelines - This event is dependent of the probabilities of events 2.1.1 (Load Drop on "Hot" Spent Fuel) and 2.1.2 (Pool Contains "Hot" Spent Fuel"). As stated in the assumptions, all of the spent fuel stored in the SFP has been stored there for a minimum of 29 years. By the standards set by NUREG-0612 (Reference 1) Section 2.1, the SFP does not contain any "hot" spent fuel. Therefore, the event 2.1.2 is not applicable to the activities under consideration here and as a result the off site release exceeding guidelines is not applicable.

2.2.1 Pool Contains Highly Enriched Fuel - All of the spent fuel stored in the SFP has been stored there for a minimum of 29 years and therefore the potential for criticality due to high enrichment fuel is not applicable. However, in this assessment it is conservatively considered to be possible 2.2.2 Load Brought Over "Off-Load" Core - All of the spent fuel stored in the SFP has been stored there for a minimum of 29 years and therefore the potential for bringing a load over an off-load core is not applicable. However, in this assessment it is conservatively considered to be possible.

2.2.3 Handling System Failure - NUREG-1774 (Reference 2) states that since the issuance of NUREG-0612 there have only been 3 heavy load drops out of an

CALCULATION FILE PRA04-08 Sheet 5 estimated 54,000 lifts. This equates to a 5.6 E-5/lift probability of a heavy load drop. There are 16 lifts postulated at HBPP for a probability of 8.96 E-4.

2.2.4 Load Falls in Orientation to Cause Criticality - As stated in the assumptions section, it is judged that the probability of a load falling in a way to cause criticality is 1 E-5.

2.2.5 Failure to Maintain Adequate Boron concentration - As this is a BWR plant there is no Boron concentration in the SFP this event is not applicable.

2.2 Criticality In Spent Fuel - This event is dependent on probability of 2.2.3 and 2.2.4. This probability equals 8.96E-9.

2 Consequences Exceed Guidelines - This probability is the same as 2.2 due an offsite release exceeding the guidelines is not possible.

P(2) = P(2.2) = P(2.3)

• P(2.4)

P(2) = (5.6E-5) * (16 lifts)*(1 E-5) = 8.96 E-9 RESULTS The probability of exceeding twenty five percent of the 10 CFR Part 100 limits using the HBPP davit and RFB crane is 8.96 E-9, which is less than the minimal increase of 1 E-7 provided by NEI 96-07, and therefore is acceptable.

REFERENCES

1. NUREG-0612, Control of Heavy Loads at Nuclear Power Plants, U.S. Nuclear Regulatory Commission, July 1980

2. NUREG-1774, A Survey of Crane Operating Experience at U.S. Nuclear Power Plants from 1968 to 2002, U.S. Nuclear Regulatory Commission, July 2003

3. NUREG-1738, Technical Study of Spent Fuel Pool Accident Risk at Decommissioning Nuclear Power Plants, U.S. Nuclear Regulatory Commission, February 2001

4. NEI 96-07 Revision 1, Guidance for 10 CFR 50.59 Implementation, Nuclear Energy Institute, November 2000

CALCULATION FILE PRA04-08 Sheet 6 2

8.96 E-9 2.2 8.96 E-9 Load Drop On Pool Contains Pool Contains 2.1.1 2.1.2 1.2.1 not apj Hot Spent Fuel I Hot Spent Fuel not applicable Highly Enriched possible Fuel Load Brought 2.2.2 Over "Off-Load" possible Core 2.2.3 8.96 E-4 Load Falls in 2.2.4 Orientation to E-5 Cause Criticality Figure 1