Academic literature on the topic 'Seals (Closures) Testing'

The steam generator in a PWR primary coolant system is one of the pieces of equipment made in China for the Qinshan nuclear power plant, Zhejiang. It is a crucial unit belonging to the category of nuclear pressure vessel. The purpose of this research work is to carry out an examination of the weld quality of the steam generator under fatigue loading and to assess its reliability by using experimental results of a fatigue test of the nuclear pressure vessel steel S-271 (Chinese Standard) and of qualified tests of welded seams of a simulated prototype of the bottom closure head of the steam generator. A guarantee of weld quality is proposed as the quality assurance of safety for the China National Nuclear Safety Supervision Bureau. The results of the reliability analysis reported in this work can be taken as supplementary material for a Probabilistic Risk Assessment (PRA) of the Qinshan nuclear power plant [1, 2]. According to the requirement of Provision II-1500 CYCLIC TESTING, ASME Boiler and Pressure Vessel Code, Section III, Rules for Construction of Nuclear Power Plant Components [13], a simulated prototype of the bottom closure head of the steam generator was made in this work for the qualified tests. Qualified tests with small sample size present a problem which is difficult to solve in reliability analysis, and are therefore of interest. Here, we offer proposals attempting to solve this problem.

Summary This paper describes a methodology for incorporating uncertainties in the optimization of well count for the deepwater Agbami field development. The lack of substantial reservoir-description data is common in many deepwater discoveries. Therefore, the development plan must be optimized and proven to berobust for a wide range of uncertainties. In the Agbami project, the design of experiments, or experimental design (ED) technique, was incorporated to optimize the well count across a wide range of subsurface uncertainties. The lack of substantial reservoir-description data is common for many deepwater discoveries. In the Agbami project, the uncertainty in oil in place was significant (greater than a factor of 2). This uncertainty was captured in a range of earth (geologic) models. Additional uncertainty variables, including permeability, fault seals, and injection conformance, were studied concurrently. Multiple well-count development plans (high, mid, and low) were developed and used as a variable in ED. The ED technique allowed multiple well counts to be tested quickly against multiple geologic models. With the net present value (NPV) calculated for each case, not only was the well count for the overall highest NPV determined, but discrete testing of each geologic model determined the optimum well count for each model. The process allowed for testing the robustness of any well count vs. any uncertainty (or set of uncertainties). A method was demonstrated quantifying the difference between perfect and imperfect knowledge of the reservoir description (geologic model) as it pertains to well locations. Introduction The Agbami structure is a northwest/southeast-trending four-way closure anticline and is located on the Niger delta front approximately 65 miles offshore Nigeria in the Gulf of Guinea (see the map in Fig. 1). The structure spans an area of 45,000 acres at spill point and is located in 4,800 ft of water. The Agbami No. 1 discovery well was drilled in late 1998. The appraisal program was completed in 2001 and included five wells and one sidetrack drilled on the structure, with each encountering oil pay. These five wells and a sidetrack penetrated an average of approximately 350 ft of oil. In this phase (Phase 3) of the development process, the key objectives are to construct a field-development plan and to obtain sanctioning. With drilling depths of up to 10,000 ft below mudline in 4,800 ft of water, well costs at Agbami will be at the high end of typical deepwater costs. Therefore, an important optimization parameter in the field development is the total well count. Agbami is typical of many deepwater developments in that the seismic is less than perfect and the appraisal well data are sparse relative to the area coverage. Therefore, subsurface uncertainty is high. In fact, the 5% probable oil in place is more than two times the oil in place at the 95% probability. As a result, the development process is challenged with determining the optimum well count for the field development across the wide range of subsurface uncertainty. Several key development decisions were determined in the previous phase(Phase 2) of the development process. These decisions were taken as givens in this study and are listed as follows:• The recommended pressure-maintenance scheme and gas-disposition strategy for the 17 million-year (MY) units is a combination of crestal gas injection with peripheral water injection.• The recommended pressure-maintenance scheme and gas-disposition strategy for the 14MY/16MY units is crestal gas injection only.• The facility design capacity recommendations are:- 250,000 stock-tank bbl per day (STB/D) oil.- 450,000 thousand cubic ft per day (Mcf/D) gas production.- 250,000 STB/D water production.- 450,000 STB/D liquid production.- 450,000 STB/D water injection.

The bolted closure joint of a bare spent fuel cask is susceptible to age-related degradation and potential loss of confinement function under long-term storage conditions. Elastomeric seals, components of the joints typically used to facilitate leak testing of the primary seals that include the metallic seal and bolting, are susceptible to degradation over time by several mechanisms, principally thermo-oxidation, stress-relaxation, and radiolytic degradation. Irradiation and thermal exposure testing and evaluation of an ethylene-propylene diene monomer (EPDM) elastomeric seal material similar to that used in the CASTOR®1 V/21 cask. Testing covers a matrix of temperature and radiation exposure conditions relevant to extended storage of the cask. Semi-empirical models are being developed to predict loss of sealing force. A special insert was developed to allow Compressive Stress Relaxation (CSR) measurements before and after the irradiation and/or thermal exposure without unloading the elastomer. A condition of the loss of sealing force for the onset of leakage was suggested. The experimentation and modeling being performed could enable acquisition of extensive coupled aging data as well as an estimation of the time when loss of sealing under aging (temperature/radiation) conditions may occur.

The extended loss of AC power (ELAP) event can pose a significant challenge to the integrity of the Reactor Coolant System (RCS) in a Pressurized Water Reactor (PWR). To mitigate the consequences of this event, it is important to maintain adequate coolant inventory and the associated heat removal capability of the RCS. A critical RCS component in maintaining RCS inventory is the Reactor Coolant Pump (RCP) seals. To ensure seal integrity, the RCP seals are either independently cooled by back-up systems or are sufficiently robust to maintain their integrity without cooling until such time when cooling may be restored. A number of new RCP seal designs have been proposed by seal manufacturers to meet this challenge. This paper focuses on one such design, namely, the KSB Station Blackout (SBO) seal package. KSB RCP seals were first introduced in the nuclear industry in the 1970s. The original KSB RCP seals, designated as HDD-254 Type A, consisted of a three stage hydrodynamic design with each stage capable of retaining full RCS pressure. The Type A seals were initially installed in the Combustion Engineering (CE) Palo Verde units and in several reactors in Germany. In the 1980s, these seals were replaced with the Type C seals that incorporated several design improvements. These seals have been successfully installed and operated in over 100 RCPs in Europe, South America, South Korea, and China. These seals continue to demonstrate excellent operating experience with typical replacement interval of 4 to 6 years. Although the reliability of the Type C seals has been excellent based on operating experience, the seal was not specifically designed for coping with an ELAP event that might ensue following an SBO. In order to support the emerging needs of nuclear industry in response to Fukushima, KSB embarked on a seal design improvement program directed towards retaining the high operational reliability of the Type C seal while enhancing the RCP seal package’s high temperature coping capability. This activity resulted in a new seal package design that includes: (1) an advanced high temperature resistant, three stage, Type F seal, (2) a passive thermal check valve (PTCV) intended to passively isolate the RCP controlled bleed-off (CBO) line to maintain RCS inventory, and (3) a back-up fourth stage shaft seal called the “Stand-still” seal. This paper discusses the design and post-accident performance of KSB’s Type F hydrodynamic RCP seal package with emphasis on seal performance capabilities under ELAP conditions. The report concludes that the capability of the primary three stage hydrodynamic seals and the fourth stage “Stand-still” seal to function at high temperatures coupled with the reliable RCP CBO line closure capability and subsequent RCS depressurization ensures that any potential seal leakage would be held to a minimum (less than 2 gpm) for the duration of a 72 hour ELAP scenario. The ELAP coping strategies and their outcomes were validated by a seal test program conducted at KSB’s testing laboratories in Frankenthal, Germany. The results of the tests confirmed that the Type F seals exhibited extremely low leakage rates (∼0.01 gpm) at conditions representative of an ELAP scenario (120 hours up to 300 °C [572 °F] temperature and 160 barg [2320 psig] pressure).

Due to delays in the siting procedure to establish a deep geological repository for spent nuclear fuel and high level waste and in construction of the already licensed Konrad repository for low and intermediate level waste, extended periods of interim storage will become more relevant in Germany. BAM is involved in most of the cask licensing procedures and is responsible for the evaluation of cask-related long-term safety issues. Elastomeric seals are widely used as barrier seals for containers for low and intermediate level radioactive waste. In addition they are also used as auxiliary seals in spent fuel storage and transportation casks (dual purpose casks (DPC)). To address the complex requirements resulting from the described applications, BAM has initiated several test programs for investigating the behavior of elastomeric seals. These include experiments concerning the hyperelastic and viscoelastic behavior at different temperatures and strain rates, the low temperature performance down to −40°C, the influence of gamma irradiation and the aging behavior. The first part of the paper gives an overview of these tests, their relevant results and their possible impact on BAM’s work as a consultant in the framework of approval and licensing procedures. The second part presents an approach of the development of a finite element model using the finite element code ABAQUS®. The long-term goal is to simulate the complex elastomeric behavior in a complete lid closure system under specific operation and accident conditions.

Generic Safety Issue 23 (GSI-23) by the U.S. Nuclear Regulatory Commission (NRC) was identified in 1980 as a result of staff concerns about reactor coolant pump (RCP) seal failure during Station Blackout (SBO), that is, seal degradation leading to a significant loss of reactor coolant in pressurized-water reactor (PWR) plants. Resolutions of GSI-23 have been considered at PWR plants. In 2000, NRC decided to close GSI-23 and issue Regulatory Issue Summary00–002 (RIS 00–002)[1], based on considerations such as; for example, the improvement of RCP seal performance[2], and the reduction of the risk of RCP seal failure in certain plants by the addition of alternate power sources. After the closure of GSI-23, some licensees were planning to make other associated improvements under their individual plant program. In Japan, the RCP seal was showed that leakage rate was low under SBO testing conditions[3] in licensing safety reviews conducted according to new nuclear regulatory standards after the nuclear accident at the Fukushima Daiichi Nuclear Power Plant. On the other hand, a boiling-water reactor (BWR) is not included in GSI-23 because operating experience indicates that seal failures in BWRs result in smaller leak rates than seal failures in PWRs and, BWRs have the reactor coolant injection capability under SBO conditions, such as the reactor core isolation cooling (RCIC) and the high-pressure coolant injection (HPCI) system. In addition, for the particular BWR-2 type plants that do not have emergency makeup systems, the pump mechanical seal was tested under SBO conditions and successfully showed minimal leakage[4]. However, for the BWR-5 type plants which have the reactor coolant injection capability, such as the RCIC and HPCI systems, the pump seal had not been tested. In Japan, after the nuclear accident at the Fukushima Daiichi Nuclear Power Plant, licensing safety reviews of BWRs and PWRs are being conducted according to new nuclear regulatory standards. We took this opportunity to test the leak rate from Primary Loop Recirculation (PLR) pump mechanical seals under SBO condition. The peak of leak rate was approximately 0.6ton/h (2.6gpm) during the 24 hours of SBO testing condition. Despite damage of O-rings in the mechanical seal by heated water which were ovserbed at post-inspection test, a very low leak rate was realized because the leakage path after passing through the damaged parts of the O-rings was limited by the other restricting pathway in the mechanical seal. This seal leakage was very low, compared with the reactor coolant makeup capability of the RCIC system and the reactor coolant release capability from main steam safety relief valve (SRV). Therefore, we reconfirmed that the result of this leak rate does not affect the safety evaluation for the reactor. It is shown in this paper that the leak rate from PLR pump mechanical seals is low under SBO condition by our demonstration test.

Abstract The V26 containment vessel was procured by the Project Manager, Non-Stockpile Chemical Materiel (PMNSCM) for use on the Phase-2 Explosive Destruction Systems. The vessel was fabricated under Code Case 2564 of the ASME Boiler and Pressure Vessel Code, which provides rules for the design of impulsively loaded vessels. The explosive rating for the vessel, based on the Code Case, is nine (9) pounds TNT-equivalent for up to 637 detonations, limited only by fatigue crack growth calculations initiated from a minimum detectable crack depth. The vessel consists of a cylindrical cup, a flat cover or door, and clamps to secure the door. The vessel is sealed with a metal gasket. The body is a deep cylindrical cup machined from a 316 stainless steel forging. The door is also machined from a 316 stainless steel forging. The closure clamps are secured with four 17-4 PH steel threaded rods with 4140 alloy steel threadednuts on one end and hydraulic nuts on the other. A flange with four high-voltage electrical feedthroughs is bolted to the door and sealed with a small metal gasket. These feedthroughs conduct the firing signals for the high-voltage Exploding Bridge-wire detonators. Small blast plates on the inside of the door protect fluidic components and electrical feedthroughs. A large blast plate provides additional protection. Both vessel door and feedthrough flange employ O-ring seals outside the metal seals in order to provide a mechanism for helium leak checks of the volume just outside the metal seal surface before and after detonation. In previous papers (References 2 and 3), the authors describe results from testing of the vessel body and ends under qualification loads, determining the effective TNT equivalency of Composition C4 (EDS Containment Vessel TNT Equivalence Testing) and analyzing the effects of distributed explosive charges versus unitary charges (EDS Containment Vessel Explosive Test and Analysis). In addition to measurements made on the vessel body and ends as reported previously, bulk motion and deformation of the door and clamping system was made. Strain gauges were positioned at various locations on the inner and outer surface of the clamping system and on the vessel door surface. Digital Image Correlation was employed during both hydrostatic testing and dynamic testing under full-load explosive detonation to determine bulk and bending motion of the door relative to the vessel body and clamping system. Some limited hydrocode and finite element code analysis was performed on the clamping system for comparison. The purpose of this analysis was to determine the likelihood of a change in the static sealing efficacy of the metal clamping system and to evaluate the possibility of dynamic burping of vessel contents during detonation. Those results will be reported in this paper.